Flexural Performance of Cross-Laminated Bamboo (CLB)...

Research ArticleFlexural Performance of Cross-Laminated Bamboo (CLB)Slabs and CFRP Grid Composite CLB Slabs

Qingfang Lv Weiyang Wang and Ye Liu

Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education Southeast UniversityNanjing 210096 China

Correspondence should be addressed to Qingfang Lv southeast_uni126com

Received 20 June 2019 Accepted 4 October 2019 Published 3 November 2019

Academic Editor Claudio Mazzotti

Copyright copy 2019 Qingfang Lv et al +is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In order to accord well with the requirements of sustainable development and green construction a cross-laminated bamboocomposed of an odd number of orthogonally oriented layers of bamboo scrimber is proposed in this paper Adjacent bamboolayers are face-bonded by structural adhesives under pressure +e uniform mechanical and physical properties can be obtainedthrough the orthogonal layup Flexural performances of three groups of one-way CLB slabs and two groups of one-way CLB slabsstrengthened with CFRP grids were investigated via four-point monotonic loading configuration until failure Experimentalparameters of thickness of the layer number of layers and manufacturing processes of CFRP grids were taken into considerationExperimental observations showed that the failure of the CLB slab was brittle and different failure modes were found in the CLBslab with CFRP grids via different manufacturing processes Test results showed that the load-carrying capacity increased with thethickness of the layer number of layers and application of CFRP grids pressed in the bamboo layer but the CFRP grids pressed inthe interface of adjacent bamboo layers weakened the load-carrying capacity +e strain analysis demonstrated that the com-pression region was utilized with more efficiency via CFRP grids pressed in the bamboo layer and the plane cross sectionassumption is suitable for both CLB slab and CLB slab strengthened with CFRP grids A theoretical calculation method of flexuralload-carrying capacity was proposed for the CLB slab the accuracy of which was proved

1 Introduction

In order to accord well with the requirements of sustainabledevelopment and green construction the construction in-dustry is undergoing significant modification and im-provement [1] More environment-friendly durable andless-labor materials are required to be adopted A typicalbiological material wood has been widely used in civilconstruction car industry furniture industry [2ndash4] whichsatisfies above requirements One of the most promisingengineered wood products is cross-laminated timber (CLT)CLT consists of an odd number of orthogonally orientedlayers of timber lumber [5] and adjacent layers are face-bonded via structural adhesives under pressure [6] +isspecific configuration provides CLT with excellent in-planeand out-of-plane strength rigidity and stability [1] suitablefor load-bearing panels and shear walls [7]

+ere are still many disadvantages of wood including along growth slow regeneration a significant shortage and alow utilization rate of the raw materials [8 9] +erefore it isnecessary to explore more feasible and appropriate materialsbased on sustainable requirements and the bamboo isattracting researchersrsquo attention Compared with wood ad-vantages of the bamboo are demonstrated as follows (1) fastergrowth speed (2) high specific strength (3) high specific ri-gidity and (4) lower water swelling ratio [8ndash10] +e bamboois convenient to be locally obtained in China which hascharacteristics as saving costs environmental friendliness andrecyclability [11ndash13] However the mechanical properties ofthe raw and unprocessed bamboo material are unstable withlarge discreteness [14] Many inevitable defects can also befound in the unprocessed bamboo material which results in apoor durability [15ndash17] To utilize the advantages of the rawbamboo and improve its material stability and performance

HindawiAdvances in Civil EngineeringVolume 2019 Article ID 6980782 17 pageshttpsdoiorg10115520196980782

kinds of bamboo engineering material including laminatedbamboo [18 19] and reconstituted bamboo [20 21] have beenproposed and studied which are beneficial to reduce thematerial discreteness and enlarge practical applications of thebamboo [22]

Inspired by the research studies on CLT an upgradedcross-laminated bamboo is proposed in this paper whichhas characteristics as uniform mechanical and physicalproperties due to orthogonal layup Failure modes andflexural performance of three groups of the one-way CLBslab a total of fifteen slab specimens were discussed Similarto generic CLT the excessive deflection is prone to be foundin the CLB under the out-of-plane loading [6] which makesthe design controlled by the structural stiffness [23] limitingits structural application and wasting a large amount ofstrength capacity+erefore to further improve the practicalutilization of the proposed CLB strengthening techniques[24ndash27] are recommended which are of important necessityIn wood structures strengthening techniques include pre-stressed steel bar [24] carbon fiber-reinforced polymer(CFPR) sheet [28 29] glass fiber-reinforced polymer(GFRP) sheet [30] and CFRP bar [31]Wei et al conducted aseries of tests to study the effect of the steel bar and FRP sheeton the flexural performance of the bamboo scrimber beams[8] Test results showed that the application of the fiber-reinforced polymer can be effective in improving the flexuralperformance of bamboo beams

However existing strengthening techniques with only onemain force direction for wood structures are regarded as notsuitable for CLBs with orthogonal force directions Apromising strengthening technique via FRP grids has beenextensively investigated in concrete [32 33] and it attracts theauthorsrsquo attention in applying it to the CLB +e majorconcern is to achieve a good bond behavior between the FRPgrids and CLB In this paper CFRP grids with high elasticmodulus were considered and two manufacturing processwere adopted for applying CFRP grids to the CLB slab (1)press the CFRP grids in the layer of the CLB slab and (2) pressthe CFRP grids in the interface of adjacent layers +estrengthening effectiveness of the CFRP grids on the CLB slabvia different manufacturing processes was further evaluated

2 Material

21 Bamboo Scrimber Bamboo scrimber is a new type ofengineering material featured as having high material ef-ficiency for utilizing almost 80 of raw bamboo inputs [34]+e process of the bamboo scrimber includes the following(1) saturate the crushed moso bamboo strips with two-component polyurethane adhesive (2) hot-press under atemperature of 140degC and a pressing rate of 1 minute to 2minutes per millimeter and (3) hot-cure and polish +eadopted process technology maintains the fibersrsquo longitu-dinal direction and retains the basic characteristics of thebamboo In this paper the bamboo scrimber was manu-factured by Hangzhou Dasuo Technology Co Ltd and hadan average bulk density of 1200 kgm3

Until now no material test standard and codes havebeen published for bamboo scrimbers in China therefore

the tensile compressive and flexural material tests on thebamboo scrimber were conducted based on the standardsfor measuring wood properties [35ndash37] and the di-mensions of the tension specimens are shown in Figure 1A total of ten tension specimens were prepared formeasuring tensile properties parallel to grain and tensileproperties perpendicular to grain respectively Each typeof test contained five tension specimens +e tensile testwas concentrically tested by the WDW-100E electronicuniversal testing machine depicted in Figure 2 and thetest results related to tensile tests are listed in Table 1 +eultimate tensile stress parallel to grain (fta) and elasticmodulus parallel to grain (Eta) of the bamboo scrimber are4745MPa and 1795 GPa respectively +e ultimatetensile stress perpendicular to grain (ftb) and elasticmodulus perpendicular to grain (Etb) of the bambooscrimber are 786MPa and 375 GPa respectively +efailure of the bamboo scrimber under tension includestension rupture and shear-tension failure in the weakenedregion

Referencing GBT 1935-2009 lsquolsquoMethod of testing incompressive strength parallel to grain of woodrdquo [38] andGBT 1939-2009 lsquolsquoMethod of testing in compressionperpendicular to grain of woodrdquo [39] the dimensions ofthe compression specimens are shown in Figure 3 A totalof ten compression specimens were prepared for mea-suring compressive properties parallel to grain andcompressive properties perpendicular to grain re-spectively Each type of test contained five compressionspecimens +e compressive test was also tested by theWDW-100E electronic universal testing machine depictedin Figure 4 and the test results related to compressive testsare listed in Table 1 +e ultimate compressive stressparallel to grain (fca) elastic modulus parallel to grain(Eca) ultimate compressive stress perpendicular to grain(fcb) and elastic modulus perpendicular to grain (Ecb) ofthe bamboo scrimber are 10799MPa 2155 GPa5164MPa and 637 GPa respectively For the compres-sion parallel to grain the failure modes of the bambooscrimber mainly are bond failure and local shear failure asshown in Figure 5(a) and the former failure mode ismainly caused by processing quality problems such asuneven dipping and hot pressing For the compressionperpendicular to grain the failure modes of the bambooscrimber mainly are split and shear failure depicted inFigure 5(b) regarded as brittle failure

22 Fiber-Reinforced Polymer Fiber-reinforced polymer hasbeen extensively investigated types of which include aramidglass carbon basalt and graphite [8] Among various fiber-reinforced polymers carbon fibre-reinforced polymer(CFRP) has been popular in recent years because of itsexcellent in-plane mechanical properties (such as stiffnessand strength) and lightness [40] Based on this the CFRP isselected to form a grid network in this study recognized asCFRP grids [41] which was fabricated by Nanjing NortaiComposite Material Equipment Manufacturing Co Ltd+e adopted CFRP grids have three epoxy resin-glued layers

2 Advances in Civil Engineering

in the longitudinal direction and two epoxy resin-gluedlayers in the transverse direction+e thickness and width ofthe single layer of CFRP reinforcement are about 07mmand 7mm respectively Based on ACI 4403R-04 ldquoGuideTest Methods for Fiber-Reinforced Polymers (FRPs) forReinforcing or Strengthening Concrete Structuresrdquo [42] theuniaxial tensile tests were conducted on two layers and three

layers of CFRP reinforcements via the WDW-100E elec-tronic universal testing machine at a loading rate of 001 kNs respectively and each series of CFRP tension specimenshad five specimens +e dimension and test setup for CFRPtension specimens are shown in Figures 6 and 7 respectively

+e average ultimate tensile stress and modulus ofelasticity for two-layer CFRP and three-layer CFRP are listed

60 55 70 6055

300

20

8

20

8

300

Unit mm

(a) (b)

Figure 1 Tension specimen (a) dimensions and (b) processed

Figure 2 Tension test of the bamboo scrimber

Table 1 Material properties of the bamboo scrimber

Property Average value Standard deviation Coefficient of variation ()Tensile test resultsUltimate tensile stress parallel to grain (MPa) 4745 881 1857Modulus of elasticity parallel to grain (GPa) 1795 086 478Ultimate tensile stress perpendicular to grain

(MPa) 786 104 1319

Modulus of elasticity perpendicular to grain (GPa) 375 033 889Compressive test resultsUltimate compressive stress parallel to grain (MPa) 10799 778 720Modulus of elasticity parallel to grain (GPa) 2155 116 538Ultimate compressive stress perpendicular to grain

(MPa) 5164 336 651

Modulus of elasticity perpendicular to grain (GPa) 637 061 965

Advances in Civil Engineering 3

Table 2 For two-layer CFRP the ultimate tensile stress andmodulus of elasticity are 114152MPa and 25550GPa re-spectively For three-layer CFRP the ultimate tensile stressand modulus of elasticity are 95257MPa and 26033GParespectively CFRP failed due to the fracture of CFRP fibersas shown in Figure 8

3 Experimental Program

31 Specimen Preparation +ree groups of one-way cross-laminated bamboo (CLB) slabs and two groups of one-wayCLB slabs strengthened with CFRP grids are discussed inthis paper Each group consisted of five test specimens withidentical parameters to take the material deviation andfabrication discreteness into consideration which demon-strated that a total of twenty-five test specimens werestudied +e key experimental parameters include thethickness of the layer number of layers CFRP grids andcorresponding manufacturing processes

311 Details of One-Way CLB Slab +e dimensions anddetails of three groups of one-way CLB slabs recognized as

60

20

20

Parallel

(a)

60

20

20

Perpendicular

(b)

Figure 3 Compression specimen (a) Parallel to grain (b) Perpendicular to grain

Figure 4 Compression test of the bamboo scrimber

(a) (b)

Figure 5 Failure modes of the bamboo scrimber under compression (a) Parallel to grain (b) Perpendicular to grain

280

7

CFRP

60 60

400

Aluminum plate Aluminum plate

Figure 6 Dimensions of CFRP


CLB-A CLB-B and CLB-C are shown in Figure 9 and listedin Table 3 In group CLB-A the one-way CLB slab iscomposed of five 20mm layers (t1 t2 20mm) In groupCLB-B the one-way CLB slab has seven layers+e thicknessof outermost layers is t1 20mm while the thickness ofmiddle layers is reduced to t2 12mm For group CLB-Cthe one-way CLB slab is composed of five 12mm layers(t1 t2 12mm) +e dimensions of groups CLB-A andCLB-B are designed as 1800mm in length (l) 600mm inwidth (b) and 100mm in thickness (t) while the dimensionsof group CLB-C are designed as 1800mm in length (l)600mm in width (b) and 60mm in thickness (t) In Table 3the numbers 1ndash5 denote the five specimens with identicalparameters in each group

312 Details of One-Way CLB Slab Strengthened with CFRPGrids In order to conveniently analyze the contribution ofthe CFRP grids for the flexural performance of the one-wayCLB slab the dimensions of the two groups of one-way CLBslabs strengthened with CFRP grids designated as CLB-Iand CLB-M are kept the same with the groups CLB-A and

CLB-C respectively +e dimensions and details of one-wayCLB slabs strengthened with CFRP grids are depicted inFigure 10 and presented in Table 4

+ere are two strategies in composing the CFRP gridsinto the one-way CLB slab (1) placing the CFRP grids intothe bottom layer and hot-pressing both of the CFRP gridsand bottom layer into an integrated whole recognized asmanufacturing process I and (2) placing the CFRP gridsbetween the bottom layer and penultimate layer and gluingand hot-pressing the CFRP grids and one-way CLB slabtogether recognized as manufacturing process M Asmentioned in Section 22 the CFRP grids have three gluedlayers in the length direction and two glued layers in thewidth direction +e spacing of the CFRP grids is chosen as50mmtimes 50mm

313 Specimen Fabrication Process As shown in Figures 9and 10 the CLB slab is glued by multiple bamboo layers andthe angle between two adjacent layers is 90 degrees in termsof the bamboo fibersrsquo arrangement direction +e bamboofibers parallel to grain are designed as the length direction ofoutermost layers (top and bottom layers) in the one-wayCLB slab All CLB slabs were fabricated in Hangzhou DasuoTechnology Co Ltd China +e main processes of the one-way CLB slab and CLB slab strengthened with CFRP gridsare shown in Figure 11

32 Test Protocol All twenty-five one-way CLB slab speci-mens strengthened with or without CFRP grids were testedunder a four-point monotonic loading configuration untilfailure as demonstrated in Figure 12 Before the formalloading a 10 kN preload was applied to the specimen andwas sustained about 3 minutes to verify the workability ofthe equipment +en the specimen was loaded at a loadingrate of 5 kN per minute until failure All slab specimens had a

Figure 7 Tension test of CFRP

Table 2 Material properties of CFRP

Property Averagevalue

Standarddeviation

Coefficient ofvariation ()

Two layersUltimate tensile stress

(MPa) 114152 5332 467

Modulus of elasticity(GPa) 25550 5899 2309

+ree layersUltimate tensile stress

(MPa) 95257 6297 661


Figure 8 Failure picture of CFRP


clear span L of 1700mm (distance between two supports)and a shear span Ls of 550mm (distance from the supportto the nearest loading point)

+e layout of strain gages and displacement transducersis shown in Figure 13 which is same in all specimens A totalof five displacement transducers were adopted Two dis-placement transducers were installed at the supports tomonitor the vertical displacement of the slab specimen at theposition of supports due to the flexural deformation Twodisplacement transducers were employed at the loadingpoints to monitor the displacements of loading points andone displacement transducer was placed in the middle of theslab specimen to monitor the midspan displacement +edata of displacements obtained from the positions of sup-ports and midspan were collected for calculating the cleardeflection at the midspan of the slab specimen

As shown in Figure 13 three strain gages were attachedon the top and bottom slab surfaces at the midspan crosssection to measure the tensile and compressive strains Sixequally spaced strain gages were attached on the side slab

surface to monitor the strain variation along the slabthickness and change in height of the neutral axis +e loadapplied by the actuator was transferred from the force-transferring beam to the slab specimens values of whichwere directly recorded by the testing machine All data ofdisplacements and strains were automatically collected bythe KD7024 static strainmeter

4 Test Results and Discussions

41 Experimental Observations and Failure Modes +e ex-perimental observations and failure modes of one-way CLBslabs and CFRP grid-strengthened CLB slabs are depicted inFigures 14 and 15 respectively

For the one-way CLB slab without CFRP grids thetypical failure process is demonstrated by taking group CLB-A with five 20mm layers as an example+e deflection of theslab specimen slowly developed until the proportional limit+e small noise of the fracture of bamboo fibers was heard atthe load of 100 kN and small cracks were observed at the

l

Length direction

t

Basicelement

Layer

Parallel tograin

t lt 2

t 2t 2

t 1

Perpendicularto grain

(a)

tt l

t 2t 2

t 2t 1

b

Width direction

(b)

Figure 9 Details of one-way CLB slabs

Table 3 Dimensions of one-way CLB slabs

Group Specimen ltimes btimes t (mm) t1 (mm) t2 (mm) Nl

CLB-A CLB-A1 CLB-A2 CLB-A3 CLB-A4 CLB-A5 1800times 600times100 20 20 5CLB-B CLB-B1 CLB-B2 CLB-B3 CLB-B4 CLB-B5 1800times 600times100 20 12 7CLB-C CLB-C1 CLB-C2 CLB-C3 CLB-C4 CLB-C5 1800times 600times 60 12 12 5Note t1 is the thickness of the outermost layer as shown in Figure 9 t2 is the thickness of the middle layer as shown in Figure 9 Nl is the number of layers inone CLB slab

tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(a)

tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(b)

Figure 10 Details of one-way CLB slabs strengthened with CFRP grids (a) CLB-I and (b) CLB-M

Table 4 Dimensions of one-way CLB slabs strengthened with CFRP grids


CLB-I CLB-I1 CLB-I2 CLB-I3 CLB-I4 CLB-I5 1800times 600times100 20 20 5CLB-M CLB-M1 CLB-M2 CLB-M3 CLB-M4 CLB-M5 1800times 600times 60 12 12 5


bottom surface of the slab specimen at the position ofloading point or midspan With the further increase of loadboth displacement and cracks gradually grew

Until the ultimate load the bottom layer (parallel grainlayer) of the slab specimen first fractured near the loadingpoint accompanied with a big sound because the strain inthe bottom layer reached the ultimate tensile strain of thebamboo fiber +en the penultimate layer (perpendiculargrain layer) almost fractured at the same time due to thesignificantly low ultimate tensile stress compared withparallel grain layer +e cracks traced along the interfacebetween the penultimate and third layers and propagated tothemiddle of the third layer Similarly the second layer is theperpendicular grain layer which almost failed same as thethird layer Finally the top layer fractured showing the

failure of the slab specimen As shown in Figure 14 thefifteen one-way CLB slab specimens without CFRP grids hadthe similar failure process which was regarded as the tensilebrittle failure

For the one-way CLB slab strengthened with CFRP gridsdifferent failure processes are obtained from groups CLB-Iand CLB-Mwith different manufacturing processes of CFRPgrids As shown in Figures 15(a)ndash15(e) the failure process ofgroup CLB-I can be summarized as follows Cracks at thebottom layer corresponding to positions of midspan andloading points were observed when the applied load wasaround 140 kN Until the load of 160 kN the fracture of theslab specimens initiated from one of the above cracksresulted in an abrupt drop of force +e force then increasedwith the increase of displacement showing the contributionof the CFRP grids for the flexural performance of the slabspecimen Until the ultimate load the top layer of the slabspecimen failed and the CFRP grids also fractured

As shown in Figures 15(f )ndash15(j) there are two differentfailure modes for group CLB-M including (a) first bondfailure at the interface of CFRP grids and bottom layer andsubsequent debonding between CFRP grids and penultimatelayer for CLB-M1 and CLB-M5 and (b) direct bond failure atthe interface of CFRP grids and penultimate layer for CLB-M2 CLB-M3 and CLB-M4 In failure mode (a) the bamboofibers of the bottom layer fractured first at a relatively lowload accompanied with the debonding between the bottomlayer and CFRP grids +e CFRP grids and the remainingfour layers still worked together until the bond failure be-tween CFRP grids and penultimate layer occurred After thedebonding of CFRP grids and penultimate layer the rest ofthe layers fractured immediately In failure mode (b) theabrupt bond failure between the CFRP grids and

Placing bambooscrimber Gluing Pressing Curing

Orthogonal gt2MPa5 hoursT gt 25degC

(a)


Orthogonal gt2MPa5 hours

Placing CFRPgrids

In the bottom layer T gt 25degC

(b)

Placing bamboo scrimber

Gluing Pressing Curing

gt2MPa5 hoursPlacing CFRP

grids T gt 25degC

(c)

Figure 11 Fabrication processes of slab specimens (a) One-way CLB slab (b) One-way CLB slab strengthened with CFRP gridsmanufacturing process I (c) One-way CLB slab strengthened with CFRP grids manufacturing process M

CLB slab

Actuator

Loading point

Support

Wid

th d

irect

ionLength direction

Support

Data system Force transferring

beam

Figure 12 Test setup


1800

t

Actuatorforce Force-transferring

beamLoading point

Displacement transducerStrain gage

550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)

Figure 13 Layout of measurement equipment (a) Side face (b) Top or bottom face

(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)

Figure 14 Failure modes of groups CLB-A CLB-B and CLB-C (a) CLB-A1 (b) CLB-A2 (c) CLB-A3 (d) CLB-A4 (e) CLB-A5 (f ) CLB-B1 (g) CLB-B2 (h) CLB-B3 (i) CLB-B4 (j) CLB-B5 (k) CLB-C1 (l) CLB-C2 (m) CLB-C3 (n) CLB-C4 (o) CLB-C5


penultimate layer was found around the load of 25 kN andthe rest of the four layers gradually fractured with the in-crease of the load

+e local drawing of failure of the slab specimensdepicted in Figure 16 is to show some detailed failure po-sitions observed in slab specimens +e separation of ad-jacent elements in the perpendicular grain layer was foundas shown in Figure 16(a) Accompanied with the fracture ofslab layers the debonding between the adjacent bamboolayers could be also found in Figure 16(b) For slab speci-mens strengthened with CFRP grids the small cracks werefound near the major crack as shown in Figures 16(c)ndash16(e)clearly show the fracture of CFPR fibers and debonding ofCFRP grids

42 Load-Displacement Relationship +e load-midspandisplacement curves of CLB slabs without CFRP grids in-cluding groups CLB-A CLB-B and CLB-C are shown inFigure 17 It is obvious that the initial stage of CLB slab

specimens without CFRP grids was almost linear until theelastic limit +e nonlinear behaviors were gradually foundwith the increase of midspan displacement which resultedin a slow reduction of cross-sectional rigidity +e nonlinearsegments in the load-midspan displacement curves of theCLB slab specimens mainly lied on the plastic compressioncapacity of the bamboo scrimber

+e load-midspan displacement curves obtained fromslab specimens CLB-A2 CLB-B2 and CLB-C4 closest toaverage values of the three groups are compared inFigure 17(d) Comparing slab specimens CLB-A2 with five20mm layers and CLB-C4 with five 12mm layers themidspan displacements of the slab specimen with thickerlayers were significantly smaller than the midspan dis-placements of the slab specimen with thinner layers underan identical load which demonstrated a larger cross-sec-tional rigidity in the slab specimen with thicker layersComparing slab specimens CLB-A2 with five layers andCLB-B2 with seven layers the midspan displacements of theslab specimen with more layers were similar to those of the

(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)

Figure 15 Failure modes of groups CLB-I and CLB-M (a) CLB-I1 (b) CLB-I2 (c) CLB-I3 (d) CLB-I4 (e) CLB-I5 (f ) CLB-M1 (g) CLB-M2 (h) CLB-M3 (i) CLB-M4 (j) CLB-M5


slab specimen with fewer layer under the same load whileboth specimens had the same total thickness+e ductility ofthe slab specimens CLB-A2 and CLB-B2 with same totalthickness was almost the same but was significantly smallerthan that of the slab specimen CLB-C4 with smaller totalthickness

+e load-midspan displacement curves of CLB slabsstrengthened with CFRP grids including groups CLB-I andCLB-M are shown in Figure 18 Similarly the initial stage ofCLB slab specimens strengthened with CFRP grids wasalmost linear until the elastic limit As shown in Figure 18(a)the significant improvement in the ductility of CLB slabstrengthened with CFRP grids via manufacturing process Idiscussed in Section 312 was obtained compared with slabspecimen CLB-A2 without CFRP grids By introducing theCFRP grids via manufacturing process I the midspan dis-placements of the slab specimen became smaller than thoseof the slab specimen without CFRP grids under an identicalload +e cross-sectional rigidity of the slab specimen wasthus found to be increased by the existence of the CFRPgrids Besides the significant decrease of the midspan dis-placement near failure of the slab specimen is caused by thedeviation of the displacement transducer away from theoriginal position as shown in Figure 18(a)

As depicted in Figure 18(b) the application of CFRPgrids via manufacturing process M did not improve theflexural performance of the CLB slab specimen whencomparing the slab specimen CLB-C4 and group CLB-MContrarily the existence of the CFRP grids in the interface oftwo adjacent layers degraded the ductility of the CLB slab+e above phenomenon can be explained by the early bond

failure between the CFRP grids and the bamboo scrimberlayer as described in Section 41

43 Load-Carrying Capacity +e measured ultimate loadsof all tested slab specimens and the calculated average ul-timate loads of each group are listed in Table 5 Because theinfluence of shear-span ratio on ultimate flexural bearingcapacity can be neglected [43] this influence is not con-sidered in the following comparison +e average ultimateload obtained from group CLB-C with five 12mm layers isadopted as the reference value to evaluate the variation in theload-carrying capacity of slab specimens of different groupsCompared with group CLB-C the groups CLB-A withthicker layers and CLB-B with more number of layers haveachieved an efficient increase in ultimate load ranging from1155 to 1651 It can be found that the ultimate load ofthe CLB slab without CFRP grids increased with the increaseof thickness of each layer and number of layers

+e average ultimate loads of group CLB-I and CLB-Mare 1974 kN and 443 kN which correspond to a maximumincrease of 2357 and a decrease of 247 respectively +eapplication of CFRP grids via manufacturing process I(pressing the CFRP grids in the bamboo layer) provided thehighest improvement for the average ultimate load For theapplication of CFRP grids in the interface between thebottom layer and penultimate layer a 10 increase in theloading-carrying capacity was found in slab specimens CLB-M1 and CLB-M5 in which the bond failure first occurred atthe interface of CFRP grids and bottom layer However inslab specimens CLB-M2 CLB-M3 and CLB-M4 with failure

Separation ofadjacent elements

(a)

Debonding ofadjacent layers

(b)

Minor cracks

(c)

Fracture of CFRP

(d)

Debonding of CFRP grids

(e)

Figure 16 Local drawings of slab specimens (a) CLB-B4 (b) CLB-C1 (c) CLB-I1 (d) CLB-I4 (e) CLB-M2


mode of the direct bond failure at the interface of CFRP gridsand penultimate layer the load-carrying capacity reducedabout 50 Different interfaces where the bond failure firstoccurred affected the load-carrying capacity significantly

44 Load-Strain Curves +e load-average strain relation-ships of slab specimens are shown in Figure 19 +e tensilestrain is recognized as the positive strain which is calculatedas the average value of the three strain gages attached on thebottom layer of the slab specimen +e compressive strain isdefined as the negative strain which can be obtained fromthe average value of the three strain gages bonded on the toplayer of the slab specimen In all slab specimens the averagestrain in both tensile and compressive regions almost lin-early increased with the increase of the load in the initial

loading stage Only slight nonlinearity was observed in thelatter stage Besides the diversity of strain values obtainedfrom different slab specimens in the same group is mainlycaused by the material dispersion and local defects Asshown in Figure 19(c) the strains were abruptly changedwhen the bottom layer was fractured and then the strainsincreased again with the load until failure

+e average ultimate tensile and compressive strains ofbamboo fibers at the bottom and top surfaces are listed inTable 5 +e average ultimate tensile strains of the slabspecimens without CFRP grids range from 2563 με and 3338με and the average compressive strains range from 2924 μεand 3395 με +e average ultimate tensile and compressivestrains of the slab specimens strengthened with CFRP gridsrange from 2083 με to 3527 με and from 3557 με to 5063 μεrespectively In general the ultimate compressive strain was

0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)

Midspan displacement (mm)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)

Figure 17 Load-midspan displacement curves of CLB slabs without CFRP grids (a) Group CLB-A (b) Group CLB-B (c) Group CLB-C (d)Comparison of groups CLB-A CLB-B and CLB-C


more than the ultimate tensile strain in all slab specimensComparing groups CLB-A and CLB-I the average ultimatecompressive strain of the latter was 483 higher than theformer which demonstrated that the compressive regionwas utilized with more efficiency due to the employment ofCFRP grids pressed in the bamboo layer Furthermore theaverage ultimate compressive strains of groups CLB-C andCLB-M were 3156 με and 3557 με respectively +e im-provement in utilizing the compressive region via pressingin the interface was not significant

45 Strain Distributions and Neutral Axis +e strain dis-tributions along the slab thickness at themidspan cross sectionof representative slab specimens are shown in Figure 20Similar to Figure 19 the positive strain is adopted as the tensilestrain and the negative strain is the compressive strain +eordinate of the curve is defined as the distance between thestrain gage and bottom surface For all representative slabspecimens the distributions of tensile strains and compressivestrains are relatively symmetric In the direction of slabthickness the strain variation is almost linear until failurewhich means that the plane cross section assumption inbending is acceptable for the one-way CLB slab and one-wayCLB slab strengthened with CFRP grids in bending

+e neutral axes of slab specimens vary within thelimited range near themiddle height of the slab cross section

Comparing the elastic stage and the ultimate stage of theCLB slab specimens without CFRP grids the neutral axisalmost remained unchanged during the whole loadinghistory and only a slight upward trend of the neural axis wasobserved +is phenomenon demonstrated that the positionof the neutral axis of the CLB slab specimen without CFRPgrids was not affected by the thickness of each layer andnumber of layers +e slight upward movement of theneutral axis was caused by the fracture of bamboo fibers inthe tension region

As listed in Table 6 the neutral axis of the group CLB-I islower than that of group CLB-A and the position of theneutral axis of the group CLB-I gradually moved downwardwith the increase of load before failure of the bamboo layerin the bottom layer which demonstrated that the CFRPgrids sustained part of the tensile force +e existence of theCFRP grids resulted in a redistribution of stress in the crosssection and sufficient compressive behaviors in the com-pression region were activated After the fracture of thebamboo fibers in the bottom layer the neutral axis of thegroup CLB-I slightly moved upward

5 Theoretical Analysis

51 Serviceability Limit State According to the Chinese codeGB 50005-2017 ldquoStandard for design of timber structuresrdquo[44] the displacement limit of the slab that corresponds to the

0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)

Figure 18 Load-midspan displacement curves of CLB slabs strengthened with CFRP grids

Table 5 Test results of all specimens

Specimen Ultimate load (kN) Standard deviation Ultimate tensile strains (με) Ultimate compressive strains (με)Ave (CLB-A) 1374 61 2889 minus 3395Ave (CLB-B) 1457 107 2563 minus 2924Ave (CLB-C) 588 36 3338 minus 3156Ave (CLB-I) 1974 79 3527 minus 5036Ave (CLB-M) 443 173 2083 minus 3557


serviceability limit state is prescribed as L250 where L is theclear span of the slab between supports 1700mm in thispaper +e average loads of groups CLB-A CLB-B and CLB-C at the midspan displacement of L250 were 4202 kN4691 kN and 984 kN respectively It is obvious that the loadat the serviceability limit state increased with the increase ofthe layer number and layer thickness +e average loads ofgroups CLB-A CLB-B and CLB-C at the midspan dis-placement of L250 were 6164 kN and 893 kN respectively Itis found that the CFRP grids pressed into the bottom bamboolayer can improve the load at the serviceability limit of the slabspecimen significantly but the CFRP grids bonded in theinterface decreased the load at the serviceability limit

52 Flexural Load-Carrying Capacity Until now no rele-vant standards and codes have been published for CLBslabs therefore the calculation of the flexural load-carryingcapacity of the CLB slab can be referred to similar calcu-lations of cross-laminated timber in Chinese code GB50005-2017 ldquoStandard for design of timber structuresrdquo [44]+e calculations of the flexural stress and effective cross-sectional rigidity are based on plane cross section as-sumption which is proved by the strain distribution alongthe slab thickness in Section 45 For simplicity only layersparallel to grain are taken into consideration +e effectivecross-sectional rigidity EIeff is obtained based on thefollowing equations

ndash4000 ndash3000 ndash2000 ndash1000 0 1000 2000 3000 40000

20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5

ndash6000 ndash4000 ndash2000 0 2000 4000 60000

10

20

30

40

50

60Fo

rce (

kN)

(d)

Figure 19 Load-average strain relationships of slab specimens (a) Group CLB-A (b) Group CLB-C (c) Group CLB-I (d) Group CLB-M


Strain (με)ndash4000 ndash3000 ndash2000 ndash1000 0 1000 2000 3000 4000

0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN

ndash2500 ndash2000 ndash1500 ndash1000 ndash500 0 500 1000 1500 2000

0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN

ndash4000 ndash3000 ndash2000 ndash1000 0 1000 2000 3000

0

10

20

30

40

50

60H

eigh

t (m

m)

(d)

Figure 20 Strain distributions along slab thickness at midspan (a) CLB-A3 (b) CLB-C1 (c) CLB-I2 (d) CLB-M1

Table 6 Positions of neutral axis under different loads

CLB-A3 CLB-I2 (before failure) CLB-I2 (after failure)P tl tlt P tl tlt P tl tlt20 484 048 30 447 045 175 466 04740 495 049 40 449 045 178 467 04760 497 050 60 457 046 180 477 04880 501 050 80 452 045 182 479 048100 504 050 100 448 045 185 481 048120 507 051 120 447 045138 569 057 140 455 045Note P is the applied load tl is the distance between the neutral axis and the bottom surface t is the slab thickness


EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)

where Ei is themodulus of ith layer parallel to grain Nmm2 Iiis the cross-sectional moment of inertia of ith layer parallel tograin mm4Ai is the cross-sectional area of ith layer parallel tograin mm2 ei is the distance between the centroid of ith layerparallel to grain and centroid of the CLB slab mm b is thewidth of the slab mm ti is the thickness of ith layer parallel tograin mm and n is the number of layers parallel to grainsFurthermore the flexural load-carrying capacity of the CLBslab can be calculated based on equation (4) when the span ofthe slab is more than 10 times the slab thickness t

MElt

2EIeffle fta (4)

where El is the elastic modulus of the outermost layer parallelto grain Nmm2 fta can be obtained from the ultimatetensile stress parallel to grain via coupon tests and M is thecross section moment and is calculated as PLs2

Based on above equations (1)ndash(4) the maximum tensilestress at failure can be calculated and the comparisonsbetween the calculated maximum tensile stress at failure andmeasured maximum tensile stress at failure are listed inTable 7 However only groups CLB-A CLB-B and CLB-Cwere involved in this paper while the groups CLB-I andCLB-M were not discussed +e main reasons are mainlyexplained as follows (1) for group CLB-I the difficulty indetermining the position of CFRP grids after pressingprocess makes the contributions of CFRP grids for theflexural load-carrying capacity difficult to be analyticallydefined and (2) for group CLB-M the unexpected bondfailure occurred Future studies will focus on the analyticalmodel of CLB slab strengthened with CFRP grids whileaccurately controlling the position of CFRP grids in the CLBslab Obviously the accuracy of the proposed analyticalmethod for calculating the flexural load-carrying capacity ofthe CLB slab is acceptable

6 Conclusions

In this paper five groups of one-way CLB slab specimensstrengthened with or without CFRP grids a total of twenty-

five specimens were tested under a four-point monotonicloading configuration until failure +e flexural performanceof slab specimens was analyzed based on load-displacementrelationship Strain distributions in the tension and com-pression regions and along the side surface were monitoredMain conclusions are summarized as follows

(1) For CLB slabs without CFRP grids the failure ini-tiated from the bottom layer near the loading pointdue to the strain in the bottom layer reaching theultimate tensile strain and immediately propagatedto adjacent perpendicular grain layer until the fullfailure of the CLB slab which is regarded as tensilebrittle failure For CLB slabs strengthened withCFRP grids different manufacturing processesresulted in different failure modes

(2) Based on the test results the ultimate load of CLBslabs without CFRP grids increased with the thick-ness of the layer and number of layers +e appli-cation of CFRP grids via pressing it into the bamboolayer significantly increased the ultimate load of slabspecimen but the CFRP grids bonded in the in-terface of adjacent layers negatively affected the load-carrying capacity

(3) Based on strain analysis obtained from tension andcompression regions the linear tensile and com-pressive strains were observed in the initial loadingstage and the ultimate compressive strain was gen-erally more than the ultimate tensile strain Comparedwith CLB slabs without CFRP grids a higher ultimatecompressive strain was observed in CLB slabsstrengthened with CFRP grids pressed in the bamboolayer which demonstrated that the compressive re-gion was utilized withmore efficiency Based on straindistributions along the slab thickness the plane crosssection assumption in bending is acceptable for theCLB slab with or without CFRP grids

(4) +e load at the serviceability limit state increased withthe increase of the layer number layer thickness andCFRP grids pressed in the bamboo layer but decreaseddue to CFRP grids bonded in the interface +e an-alytical method related to flexural load-carrying ca-pacity was proposed for CLB slabs without CFRPgirds the accuracy of which was proved

Data Availability

All data used to support the findings of this study areavailable from the corresponding author upon request

Table 7 Validation of the analytical method of calculating the flexural load-carrying capacity

Group Pu (kN) Mmax (kNmiddotm) EIeff (times1011 Nmiddotmm2) σc (MPa) εmax (με) Ep (MPa) σa (MPa) Δ ()

CLB-A 1374 37785 71082 4771 2889 17950 5186 800CLB-B 1457 400675 74313 4839 2563 17950 4601 518CLB-C 588 1617 15347 5674 3338 17950 5992 531Note Pu is the measured ultimate load as listed in Table 5Mmax is the maximum cross section moment σc is the calculated maximum flexural stress based onequation (4) εmax is the average measured maximum strain as listed in Table 5 Ep is the elastic modulus parallel to grain under tension σa is the measuredmaximum flexural stress at failure calculated as Epεmax Δ is the error of the calculated maximum flexural stress compared with measured maximum flexuralstress


Conflicts of Interest

+e authors declare that they have no conflicts of interest

Acknowledgments

+e authors would like to acknowledge the financial supportfrom the Integrated Key Precast Components and NewWood-Bamboo Composite Structure (2017YFC0703502)

References

[1] K S Sikora D O McPolin and A M Harte ldquoEffects of thethickness of cross-laminated timber (CLT) panels made fromIrish Sitka spruce on mechanical performance in bending andshearrdquo Construction and Building Materials vol 116pp 141ndash150 2016

[2] Y Xiao Q Zhou and B Shan ldquoDesign and construction ofmodern bamboo bridgesrdquo Journal of Bridge Engineeringvol 15 no 5 pp 533ndash541 2009

[3] E-S Chele M-C Ricardo P-M Ana and M-R TeresaldquoBamboo from traditional crafts to contemporary design andarchitecturerdquo ProcediamdashSocial and Behavioral Sciencesvol 51 pp 777ndash781 2012

[4] J M O Scurlock D C Dayton and B Hames ldquoBamboo anoverlooked biomass resourcerdquo Biomass and Bioenergyvol 19 no 4 pp 229ndash244 2000

[5] Y Liao D Tu J Zhou et al ldquoFeasibility of manufacturingcross-laminated timber using fast-grown small diameter eu-calyptus lumbersrdquo Construction and Building Materialsvol 132 pp 508ndash515 2017

[6] ZWang M Gong and Y-H Chui ldquoMechanical properties oflaminated strand lumber and hybrid cross-laminated timberrdquoConstruction and Building Materials vol 101 pp 622ndash6272015

[7] Q Zhou M Gong Y H Chui and M MohammadldquoMeasurement of rolling shear modulus and strength of crosslaminated timsber fabricated with black sprucerdquo Constructionand Building Materials vol 64 no 30 pp 379ndash386 2014

[8] Y Wei X Ji M Duan and G Li ldquoFlexural performance ofbamboo scrimber beams strengthened with fiber-reinforcedpolymerrdquo Construction and Building Materials vol 142pp 66ndash82 2017

[9] Y Wei M Zhou and D Chen ldquoFlexural behaviour of glulambamboo beams reinforced with near-surface mounted steelbarsrdquo Materials Research Innovations vol 19 no 1pp S1ndash103 2015

[10] Y Wei X Ji M Zhou L Zhao and M Duan ldquoMechanicalproperties of bamboo-concrete composite structures withdowel-type connectionsrdquo Transactions of the Chinese Societyof Agricultural Engineering vol 33 no 3 pp 65ndash72 2017

[11] M Waite ldquoSustainable textiles the role of bamboo and acomparison of bamboo textile properties-Part 1rdquo Journal ofTextile and Apparel Technology and Management vol 6no 2 2009

[12] T Afrin R K Kanwar X Wang and T Tsuzuki ldquoPropertiesof bamboo fibres produced using an environmentally benignmethodrdquo e Journal of e Textile Institute vol 105 no 12pp 1293ndash1299 2014

[13] C J Lee and J Park ldquoGrowth model of bamboo-shapedcarbon nanotubes by thermal chemical vapor depositionrdquoApplied Physics Letters vol 77 no 21 pp 3397ndash3399 2000

[14] B Shan L Gao Z Li Y Xiao and Z Wang ldquoResearch andapplicant of solar energy-prefabricated bamboo Pole houserdquo

in Proceedings of the 12th International Symposium onStructural Engineering Beijing China November 2012

[15] C Uko and N Gowripalan ldquoStrength properties of raffiabamboordquo Construction and Building Materials vol 3 no 1pp 49ndash52 1989

[16] S Paudel and M Lobovikov ldquoBamboo housing marketpotential for low-income groupsrdquo Journal of Bamboo andRattan vol 2 no 4 pp 381ndash396 2003

[17] P J Kaur S Satya K K Pant and S N Naik ldquoEco-friendlypreservation of bamboo species traditional to modern tech-niquesrdquo BioResources vol 11 no 4 pp 10604ndash10624 2016

[18] N Nugroho and N Ando ldquoDevelopment of structuralcomposite products made from bamboo II fundamentalproperties of laminated bamboo lumberrdquo Journal of WoodScience vol 47 no 3 pp 237ndash242 2001

[19] M Mahdavi P L Clouston and S R Arwade ldquoA low-technology approach toward fabrication of laminated bamboolumberrdquo Construction and Building Materials vol 29pp 257ndash262 2012

[20] L Qin and W Yu ldquoResearch on surface color properties ofthermo-treated reconstituted bamboo lumber after artificialweathering testrdquo Advanced Materials Research vol 79ndash82pp 1395ndash1398 2009

[21] Y W-J Y Yang-lun and Z Y R Ding-hua ldquoStudies onfactors influencing properties of reconstituted engineeringtimber made from small-sized bamboordquo China ForestProducts Industry vol 6 p 007 2006

[22] B Sharma A Gatoo M Bock and M Ramage ldquoEngineeredbamboo for structural applicationsrdquo Construction andBuilding Materials vol 81 pp 66ndash73 2015

[23] W Yang J Shenxue L Qingfang Z Qisheng W Libin andL Zhitao ldquoExperimental study on flexural performance ofbamboo beamsrdquo Building Structure vol 1 2010

[24] V De Luca and C Marano ldquoPrestressed glulam timbersreinforced with steel barsrdquo Construction and Building Ma-terials vol 30 pp 206ndash217 2012

[25] A Borri andM Corradi ldquoStrengthening of timber beams withhigh strength steel cordsrdquo Composites Part B Engineeringvol 42 no 6 pp 1480ndash1491 2011

[26] K U Schober and K Rautenstrauch ldquoPost-strengthening oftimber structures with CFRPrsquosrdquo Materials and Structuresvol 40 no 1 pp 27ndash35 2007

[27] Y J Kim and K A Harries ldquoModeling of timber beamsstrengthened with various CFRP compositesrdquo EngineeringStructures vol 32 no 10 pp 3225ndash3234 2010

[28] Y-F Li Y-M Xie and M-J Tsai ldquoEnhancement of theflexural performance of retrofitted wood beams using CFRPcomposite sheetsrdquo Construction and Building Materialsvol 23 no 1 pp 411ndash422 2009

[29] YWei S Yan S ChenM Duan and L BWang ldquoNumericalsimulation on bending performance of FRP reinforcedbamboo beamsrdquo Acta Materiae Compositae Sinica vol 36no 4 pp 1036ndash1044 2019

[30] Y Nadir P Nagarajan M Ameen and M Arif MuhammedldquoFlexural stiffness and strength enhancement of horizontallyglued laminated wood beams with GFRP and CFRP com-posite sheetsrdquo Construction and Building Materials vol 112pp 547ndash555 2016

[31] H Johnsson T Blanksvard and A Carolin ldquoGlulammembers strengthened by carbon fibre reinforcementrdquo Ma-terials and Structures vol 40 no 1 pp 47ndash56 2007

[32] H Fang X Xu W Liu et al ldquoFlexural behavior of compositeconcrete slabs reinforced by FRP grid facesheetsrdquo CompositesPart B Engineering vol 92 pp 46ndash62 2016


[33] R Guo Y Pan L Cai and S Hino ldquoBonding behavior ofCFRP grid-concrete with PCM shotcreterdquo EngineeringStructures vol 168 pp 333ndash345 2018

[34] P Van der Lugt ldquoDesign interventions for stimulatingbamboo commercialization-dutch design meets bamboo as areplicable modelrdquo Doctoral thesis Delft University ofTechnology Delft Netherlands 2008

[35] Chinarsquo National Standard General Requirements for Physicaland Mechanical Tests of Wood (GBT 19282009) ChinarsquoNational Standard Beijing China 2009

[36] Chinarsquo National Standard Method of Testing in TensileStrength Parallel to Grain of Wood (GBT 1938-2009) ChinarsquoNational Standard Beijing China 2009

[37] Chinarsquo National Standard Method of Testing in TensileStrength Perpendicular to Grain of Wood (GBT 14017-2009)Chinarsquo National Standard Beijing China 2009

[38] Chinarsquo National Standard Method of Testing in CompressiveStrength Parallel to Grain of Wood (GBT 1935-2009) ChinarsquoNational Standard Beijing China 2009

[39] Chinarsquo National Standard Method of Testing in CompressionPerpendicular to Grain of Wood (GBT 1939-2009) ChinarsquoNational Standard Beijing China 2009

[40] Y Li H Zhang Y Liu et al ldquoSynergistic effects of spray-coated hybrid carbon nanoparticles for enhanced electricaland thermal surface conductivity of CFRP laminatesrdquoComposites Part A Applied Science and Manufacturingvol 105 pp 9ndash18 2018

[41] X Yang W-Y Gao J-G Dai Z-D Lu and K-Q YuldquoFlexural strengthening of RC beams with CFRP grid-rein-forced ECC matrixrdquo Composite Structures vol 189 pp 9ndash262018

[42] ACIGuide Test Methods for Fiber-Reinforced Polymers (FRPs)for Reinforcing or Strengthening Concrete Structures (ACI4403R-04) ACI Farmington Hills MI USA 2004

[43] J Zhou H Jiang L Lu Y Qi and Y Zhang ldquoExperimentalstudy on flexural bearing capacity of recombinant bamboobeamsrdquo Building Structure vol 23 pp 42ndash45 2016

[44] Chinarsquo National Standard Standard for Design of TimberStructures (GB 50005-2017) Chinarsquo National Standard BeijingChina 2018


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kinds of bamboo engineering material including laminatedbamboo [18 19] and reconstituted bamboo [20 21] have beenproposed and studied which are beneficial to reduce thematerial discreteness and enlarge practical applications of thebamboo [22]

Inspired by the research studies on CLT an upgradedcross-laminated bamboo is proposed in this paper whichhas characteristics as uniform mechanical and physicalproperties due to orthogonal layup Failure modes andflexural performance of three groups of the one-way CLBslab a total of fifteen slab specimens were discussed Similarto generic CLT the excessive deflection is prone to be foundin the CLB under the out-of-plane loading [6] which makesthe design controlled by the structural stiffness [23] limitingits structural application and wasting a large amount ofstrength capacity+erefore to further improve the practicalutilization of the proposed CLB strengthening techniques[24ndash27] are recommended which are of important necessityIn wood structures strengthening techniques include pre-stressed steel bar [24] carbon fiber-reinforced polymer(CFPR) sheet [28 29] glass fiber-reinforced polymer(GFRP) sheet [30] and CFRP bar [31]Wei et al conducted aseries of tests to study the effect of the steel bar and FRP sheeton the flexural performance of the bamboo scrimber beams[8] Test results showed that the application of the fiber-reinforced polymer can be effective in improving the flexuralperformance of bamboo beams

However existing strengthening techniques with only onemain force direction for wood structures are regarded as notsuitable for CLBs with orthogonal force directions Apromising strengthening technique via FRP grids has beenextensively investigated in concrete [32 33] and it attracts theauthorsrsquo attention in applying it to the CLB +e majorconcern is to achieve a good bond behavior between the FRPgrids and CLB In this paper CFRP grids with high elasticmodulus were considered and two manufacturing processwere adopted for applying CFRP grids to the CLB slab (1)press the CFRP grids in the layer of the CLB slab and (2) pressthe CFRP grids in the interface of adjacent layers +estrengthening effectiveness of the CFRP grids on the CLB slabvia different manufacturing processes was further evaluated

2 Material

21 Bamboo Scrimber Bamboo scrimber is a new type ofengineering material featured as having high material ef-ficiency for utilizing almost 80 of raw bamboo inputs [34]+e process of the bamboo scrimber includes the following(1) saturate the crushed moso bamboo strips with two-component polyurethane adhesive (2) hot-press under atemperature of 140degC and a pressing rate of 1 minute to 2minutes per millimeter and (3) hot-cure and polish +eadopted process technology maintains the fibersrsquo longitu-dinal direction and retains the basic characteristics of thebamboo In this paper the bamboo scrimber was manu-factured by Hangzhou Dasuo Technology Co Ltd and hadan average bulk density of 1200 kgm3

Until now no material test standard and codes havebeen published for bamboo scrimbers in China therefore

the tensile compressive and flexural material tests on thebamboo scrimber were conducted based on the standardsfor measuring wood properties [35ndash37] and the di-mensions of the tension specimens are shown in Figure 1A total of ten tension specimens were prepared formeasuring tensile properties parallel to grain and tensileproperties perpendicular to grain respectively Each typeof test contained five tension specimens +e tensile testwas concentrically tested by the WDW-100E electronicuniversal testing machine depicted in Figure 2 and thetest results related to tensile tests are listed in Table 1 +eultimate tensile stress parallel to grain (fta) and elasticmodulus parallel to grain (Eta) of the bamboo scrimber are4745MPa and 1795 GPa respectively +e ultimatetensile stress perpendicular to grain (ftb) and elasticmodulus perpendicular to grain (Etb) of the bambooscrimber are 786MPa and 375 GPa respectively +efailure of the bamboo scrimber under tension includestension rupture and shear-tension failure in the weakenedregion

Referencing GBT 1935-2009 lsquolsquoMethod of testing incompressive strength parallel to grain of woodrdquo [38] andGBT 1939-2009 lsquolsquoMethod of testing in compressionperpendicular to grain of woodrdquo [39] the dimensions ofthe compression specimens are shown in Figure 3 A totalof ten compression specimens were prepared for mea-suring compressive properties parallel to grain andcompressive properties perpendicular to grain re-spectively Each type of test contained five compressionspecimens +e compressive test was also tested by theWDW-100E electronic universal testing machine depictedin Figure 4 and the test results related to compressive testsare listed in Table 1 +e ultimate compressive stressparallel to grain (fca) elastic modulus parallel to grain(Eca) ultimate compressive stress perpendicular to grain(fcb) and elastic modulus perpendicular to grain (Ecb) ofthe bamboo scrimber are 10799MPa 2155 GPa5164MPa and 637 GPa respectively For the compres-sion parallel to grain the failure modes of the bambooscrimber mainly are bond failure and local shear failure asshown in Figure 5(a) and the former failure mode ismainly caused by processing quality problems such asuneven dipping and hot pressing For the compressionperpendicular to grain the failure modes of the bambooscrimber mainly are split and shear failure depicted inFigure 5(b) regarded as brittle failure

22 Fiber-Reinforced Polymer Fiber-reinforced polymer hasbeen extensively investigated types of which include aramidglass carbon basalt and graphite [8] Among various fiber-reinforced polymers carbon fibre-reinforced polymer(CFRP) has been popular in recent years because of itsexcellent in-plane mechanical properties (such as stiffnessand strength) and lightness [40] Based on this the CFRP isselected to form a grid network in this study recognized asCFRP grids [41] which was fabricated by Nanjing NortaiComposite Material Equipment Manufacturing Co Ltd+e adopted CFRP grids have three epoxy resin-glued layers





60 55 70 6055

300

20

8

20

8

300

Unit mm

(a) (b)





(MPa) 786 104 1319


(MPa) 5164 336 651







60

20

20

Parallel

(a)

60

20

20

Perpendicular

(b)



(a) (b)


280

7

CFRP

60 60

400













Standarddeviation



(MPa) 114152 5332 467



(MPa) 95257 6297 661











l

Length direction

t

Basicelement

Layer

Parallel tograin

t lt 2

t 2t 2

t 1


(a)

tt l

t 2t 2

t 2t 1

b

Width direction

(b)





tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(a)

tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(b)













(a)



Placing CFRPgrids


(b)




grids T gt 25degC

(c)


CLB slab

Actuator

Loading point

Support

Wid

th d

irect

ionLength direction

Support


beam



1800

t


beamLoading point


550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)








(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





60 55 70 6055

300

20

8

20

8

300

Unit mm

(a) (b)





(MPa) 786 104 1319


(MPa) 5164 336 651







60

20

20

Parallel

(a)

60

20

20

Perpendicular

(b)



(a) (b)


280

7

CFRP

60 60

400













Standarddeviation



(MPa) 114152 5332 467



(MPa) 95257 6297 661











l

Length direction

t

Basicelement

Layer

Parallel tograin

t lt 2

t 2t 2

t 1


(a)

tt l

t 2t 2

t 2t 1

b

Width direction

(b)





tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(a)

tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(b)













(a)



Placing CFRPgrids


(b)




grids T gt 25degC

(c)


CLB slab

Actuator

Loading point

Support

Wid

th d

irect

ionLength direction

Support


beam



1800

t


beamLoading point


550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)








(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia






60

20

20

Parallel

(a)

60

20

20

Perpendicular

(b)



(a) (b)


280

7

CFRP

60 60

400













Standarddeviation



(MPa) 114152 5332 467



(MPa) 95257 6297 661











l

Length direction

t

Basicelement

Layer

Parallel tograin

t lt 2

t 2t 2

t 1


(a)

tt l

t 2t 2

t 2t 1

b

Width direction

(b)





tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(a)

tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(b)













(a)



Placing CFRPgrids


(b)




grids T gt 25degC

(c)


CLB slab

Actuator

Loading point

Support

Wid

th d

irect

ionLength direction

Support


beam



1800

t


beamLoading point


550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)








(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia











Standarddeviation



(MPa) 114152 5332 467



(MPa) 95257 6297 661











l

Length direction

t

Basicelement

Layer

Parallel tograin

t lt 2

t 2t 2

t 1


(a)

tt l

t 2t 2

t 2t 1

b

Width direction

(b)





tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(a)

tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(b)













(a)



Placing CFRPgrids


(b)




grids T gt 25degC

(c)


CLB slab

Actuator

Loading point

Support

Wid

th d

irect

ionLength direction

Support


beam



1800

t


beamLoading point


550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)








(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









l

Length direction

t

Basicelement

Layer

Parallel tograin

t lt 2

t 2t 2

t 1


(a)

tt l

t 2t 2

t 2t 1

b

Width direction

(b)





tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(a)

tt l

t 2t 2

t 2t 1

l

Length direction

CFRPgrids

Parallel tograin


50

50

(b)













(a)



Placing CFRPgrids


(b)




grids T gt 25degC

(c)


CLB slab

Actuator

Loading point

Support

Wid

th d

irect

ionLength direction

Support


beam



1800

t


beamLoading point


550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)








(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









(a)



Placing CFRPgrids


(b)




grids T gt 25degC

(c)


CLB slab

Actuator

Loading point

Support

Wid

th d

irect

ionLength direction

Support


beam



1800

t


beamLoading point


550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)








(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


1800

t


beamLoading point


550 300 300 550

(a)

600

t

Top

Bottom

Side

Strain gage

(b)


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (k) (l)

(m) (n) (o)








(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia







(a) (b)

(c) (d)

(e) (f )

(g) (h)

(i) (j)










(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









(a)


(b)

Minor cracks

(c)

Fracture of CFRP

(d)


(e)







0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia






0 5 10 15 20 25 300

20

40

60

80

100

120

140

160Fo

rce (

kN)


CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

CLB-B1CLB-B2CLB-B3

CLB-B4CLB-B5

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

Forc

e (kN

)


(b)

CLB-C1CLB-C2CLB-C3

CLB-C4CLB-C5

0 10 20 30 40 50 600

10

20

30

40

50

60

70

Forc

e (kN

)


(c)

CLB-A2CLB-B2CLB-C4

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160Fo

rce (

kN)


(d)










0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









0 10 20 30 40 50 600

50

100

150

200

Forc

e (kN

)


CLB-I2CLB-I3CLB-I4

CLB-I5CLB-A2

(a)

0 10 20 30 40 500

10

20

30

40

50

60

70

Forc

e (kN

)


CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5CLB-C4

(b)








20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





20

40

60

80

100

120

140

160Fo

rce (

kN)

Strain (με)

CLB-A1CLB-A2CLB-A3

CLB-A4CLB-A5

(a)

Strain (με)

CLB-C1CLB-C4CLB-C5

ndash4000 ndash2000 0 2000 40000

10

20

30

40

50

60

70

Forc

e (kN

)

(b)

Strain (με)

CLB-I2CLB-I3

CLB-I4CLB-I5

ndash6000 ndash3000 0 3000 60000

50

100

150

200

Forc

e (kN

)

(c)

Strain (με)

CLB-M1CLB-M2CLB-M3

CLB-M4CLB-M5


10

20

30

40

50

60Fo

rce (

kN)

(d)




0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



0

20

40

60

80

100H

eigh

t (m

m)

20kN40kN60kN

80kN100kN

120kN138kN

(a)

Strain (με)

10kN20kN30kN

40kN50kN

60kN62kN


0

10

20

30

40

50

60

Hei

ght (

mm

)

(b)


0

20

40

60

80

100

Hei

ght (

mm

)

30kN40kN60kN

80kN100kN120kN

140kN160kN180kN

(c)

Strain (με)

10kN20kN30kN

40kN50kN55kN


0

10

20

30

40

50

60H

eigh

t (m

m)

(d)





EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


EIeff 1113944n

i1EiIi + EiAie

2i1113872 1113873 (1)

Ii bt3i12

(2)

Ai bti (3)


MElt

2EIeffle fta (4)



6 Conclusions







Data Availability








Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




Acknowledgments


References


















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia

















RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


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