Report _FNL_on a Collapse Building_Coca-Colar Rd in Ilorin

7/28/2019 Report _FNL_on a Collapse Building_Coca-Colar Rd in Ilorin

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Report on a collapsed Building in Ilorin,Kwara State, Nigeria

Report ID: CIVILUINLORIN/001

May, 2012Collapsed Building Details:

Project: Office ComplexLocation: Coca-Cola Road, Ilorin, Kwara StateClient: Ahmad Oyedeji MUSTAPHA

Architect: Arc Design Consult,

SYNOPSIS

This report examines the case of collapse of a building that

occurred under construction, at a location along Coca-colaroad, Ilorin, Kwara State, Nigeria. The building was underconstruction when it suddenly collapsed on 12th April 2012during the day at noon.The framed-structure was proposedto be a two-storey building and its construction had reachedthe second suspended slab when it collapsed. The site wasvisited while the remains of the collapse were observed,materials used for the construction were examined and thesoilcondition was also observed.The town planningauthority in charge of approval of building plans waswritten in order to know the level of their involvement inthe collapsed structure, while the architectural drawingswere scrutinised. The contractor and the client in theconstruction of the building could not be reached duringthe period ofthese findings. The investigating team alsoobserved and confirmed that the collapse occurred duringthe pouring of the first floor concrete, which suggests thatthe cause was as a result of poor scaffolding and inadequatesupports/props and arrangement. The issue of punitive

measures that should be given to culprits was stressed.Proposed preventive measures are also suggested in theNigerian context in order to reduce and possibly stop theincessant cases of building collapses.

Investigators

A.A.Adedeji , MSc(Prague),PhD(ABU),MIAENG, FRND,MNICE,MNEAM,Reg

COREN)Department of Civil Engineering, Universityof Ilorin08033774616

[email protected]. JimohB.Eng. M.Eng. Ph.D. (Civil ),MNSE, COREN Regd

Department of Civil Engineering, Universityof Ilorin08035741851

[email protected]. J imoh,.Eng. M.Eng. Ph.D. (Civil ),MNSE, COREN Regd.

Department of Civil Engineering, Universityof Ilorin07037990341

[email protected] B.O. Adams, finaKWARA STATEArchitecture),

[email protected]. Osanishi,KWARA STATEStructure),

08037272030

[email protected]

Sponsor

NIGERIAN BUILDING AND ROADRESEARCH INSTITUTEFederal Minist ry of Science andTechnologyPlot 449, Samuel Ogedengbe Crescent,Jabi;,PMB 5065 Wuse GPO, Abuja-Nigeria

www.nbrri.gov.ng

By:Director-General/Chief Executive Officer

PROFESSOR DANLADIS. MATAWALBEng. (ABU), MSc. (London), DIC, PhD,CEng, FNSE, RE(coren)


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INTRODUCTION

Failure of structuresa phenomenon that is never designed to happenbut sadlynot astrange thing in the construction industry all over the world with particularreference to the developing countries. In Nigeria, incidences of collapsed buildingsare more rampant than for other structures. What usually accompanies the collapseis loss of lives and economy. This therefore calls forurgent check to forestall futureoccurrence.

Many structural failurefaults are usually attributed to negligence of structuralengineer, the builder and the other professionals involved in the constructionwithout having a thought of other causes. It is in this light that this investigationwas ordered and sponsored by theNigerian Building and Road Research Institute,Federal Ministry of Science and Technologyfrom the office of the Director-

General/Chief Executive Officer,to be carried out on the reported collapsedbuilding in other to know the cause of and perhaps the reasons for the failure andwhere to put the blame.

INVESTIGATION ON THE COLLAPSED BUILDING IN ILORIN

The building in focus is the recently reported case along Coca-cola road Ilorin,Nigeria. This investigation was carried out by the team mandated for the work.

The procedure of investigationinvolved:contact with regulation authority, site

inspection, tests of materials, discussion/observations,conclusion andrecommendation. Also included is the view of the Architect. It is important tomention that observation was based on what happened at the site of collapsedbuilding and the structural drawing was not available.

CONTACT WITH THE REGULATION AUTHORITY

Communication with the town planning authority Ilorin: The Town PlanningAuthority in Ilorin supplied useful information, to this team, on whether thebuilding was approved or not before construction. The extract from the reply dated7th May 2012 is as follows:-

The developer (client) and the builder of the building were invited to a meetingwith the management of KwaraStateTown Planning Authority with a view toinvestigating the cause of the collapse. The building was a two storey and it wasunder construction without Town Planning and Development Authorities building


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permit /approval. No qualified architect or engineer accepted full responsibility ofthe construction. The builder and the supervisor are not yet known during thisinvestigation. Structural drawings submitted were not signed by any CORENregistered engineer.

The deduction from the above information is that, the building was not designed orconstructed by a qualified Engineer.

SITE INSPECTION

The site was visited in April 26th 2012 and revisited on 25 May 2012 in order toascertain the cause of the collapse. At the site, inspection was carried out on theremain of the building while measurement and photographs were taken andsamples of the materials used for the construction were also selected for the tests.

The results of observation are presented below.

Construction defaults

Observation 1: There was no extra support (like timber props) under 1st floor as itwas used to carry the scaffolding of the second floor. Reliance was placed on fewcast reinforced concrete columns. See plate 1. This in effect will subject the 1stfloor slabs to extra heavy loads.

Observation 2: Ends of reinforcement for the beams were not anchored intocolumn reinforcement. See plate 2. This will not allow moment transfer frombeam to column and to the foundation. In this case little stresses will cause cracks

Plate 1 1st

& 2nd

floor in ruins

Ground floor 120 mm thick

First suspended floor 120 mm

thick

side beam carrying 1st floor

460mm deep and 225 mm wide

Edge columns carrying the 1

st

suspended floor 2225x225 section

Rubbles of the column weak concrete

The collapsed 2nd suspended floor


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and pull out of reinforcement and easy detachment of members meeting at thejoint.

Observation 3: No top bars for slabs over beam reinforcement and no provision fortorsion reinforcement at corners of slabs. See plate 3. This will cause cracks to begenerated over the supports of the slabs . The cracks will make the slabs behave assimply supported and not as continuous beam though in construction they appearso. This will create heavy bending moment at the middle span of slabs.

Observation 4. After the collapse the 1st floor came down directly on the groundfloor showing crushing of concrete .See plate 1. This is an indication of crushing ofconcrete.

Observation 5: Span of slab was up to 5.22m . Checking span effective depth ratiogives effective depth of 5220/20/1.3= 200 mm, assuming an modification factor of

1.3 and nominal span/effective depth ratio of 20 (because the slab was already asimply supported since there is no hogging reinforcement). But on site overalldepth of slab was 120 mm which gives effective depth of 89 mm (120-25-12/2=89mm). Thus deflection criteria was not satisfied and therefore the depth used wassmall.

No proper anchorage

for beam

reinforcement to

column reinforcement.

Isolated plain

concrete supposed to

be contained within

beam stirrup

Plate 2 Beam and column collapse

No top bars over beam reinforcement

and no torsional reinforcement at

corners

Plate 3 . 2nd

floor under construction justbefore collapse


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Observation 6: For already cast beams and columns, because there was noanchorage of beam reinforcement into columns reinforcement, a little lateral forcesor sagging moment which might have occurred during construction will causecracks formation and detachment of beams and columns at their joints therebydestabilizing the whole structure.

Observation 7: After collapse appearance of concrete within column links was inlumps (plate 4), showing that the concrete was weak and not prepared well.

Observation 8: When the above lapses were centred on 1st floor, there are alsosome problems with the second floor, especially its form work, which was beingcast when the collapse occurred. The formwork for this floor was probably notstrong or not supported well laterally or not properly mounted on the first floor

THE COLLAPSEANALYSISSTRUCTURAL PERSPECTIVE

Schematic diagram for describing the construction arrangement: While theobservations given above (1 to 8) are based on site observations, it is alsoworthwhile to put the construction arrangement in schematic diagram for otherexplanations. To evaluate the cause of collapse, it is important to present what

form the applied load and what form the resisting force at the point of this collapse.

(i) The applied load. The applied load on the 1st floor as at the time of

collapse are the self weight of the floor, the weight of the workers, the

weight of the wet concrete for the 2nd floor , the reinforcement, the self

Main bars forcolumn not well

binded

Column on first floor not

well connected

Lumps of concrete

within links shows

weak concrete

Plate 4Coloumn links and concrete lumps


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weight of the formwork and probably the vibration caused by movement

of the workers.

(ii) The resisting force: For the 2ndfloor under construction, the resisting

force is provided by the timber and bamboo props formwork which have

their bases seated on the 1st floor. For the 1st floor, this is provided byonly few R.C. columns. This arrangement is schematically presented in

Figure 1.

Figure 1 Schematic diagram for construction arrangement

Within the span of the first floor are props from 2nd floor. These can cause heavybending and collapse of the 1st floor slab. Also few reinforced concrete columnsare carrying the 1st floor. Because they are inadequate, they could be crushed orbuckled during the construction.

Collapse and direction: From above the applied load on the 2nd floor causedsagging of the floor and crushing of the columns resulting to the collapse.

The description of the 2st floor under construction: Plates 2, 3 and 4 show that thecasting of the floor was not complete when the failure occurred. The schematicdiagram of the floor is presented in Figure 2, showing the part cast given by theshaded part in the figure. This little concrete pour assisted the collapse forcing theformwork to follow the direction of arrow also shown the figure. This direction iswhere the concrete was being poured showing that the formwork tilted and there

was no lateral restraint.

2nd

floor slab under construction

Scaffold support for 2nd

floor. This is made of

few block wall, bamboo and timber props

resting on cast 1st floor

DPCConcrete columns supporting 1st floor

1st

floor slab already constructed

Soil


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The shaded portion is the area of slab being poured just before the collapse whilethe unshaded area is not yet poured see also plates 1 and 2 of the exposedreinforcement.

Though at the time of visit some weeks have elapsed therefore concrete test willnot give the actual strength at failure..

Topography at the site: The terrain is well drained and the soil is firmInplates 5 and6 are the general view of the site.

Plate 5 General view of the site Plate 6 The collapse side and adjacentnew building under construction

3 421

C

B

A

27000mm

6 mY12@200c/c

Both direction

Figure 2 Schematic diagram of the collapsed floor.

panel 1 Panel 2 panel 3

panel 4 panel 5

Direction of sway and

tilting at collapse


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Stage of construction at collapse: Up to the time of collapse, the DPC (groundfloor) had been constructed; some columns and beams have been cast also beforethe collapse-see plate 7. Also formwork for the casting of the first floor wasalready in place as shown in plate 8. The first floor was being cast or poured whenthe incident occurred.See plates 9 and 10. At this stage, the collapse brought theconstruction to an abrupt end.

EXPERIMENTAL AND VISUALTESTS OF MATERIALS

Aggregate:The aggregates found on site were sharp sand and granite. Sieveanalysis was carried out on them. Results obtained are shown in the tables below.

Plate 7An isolated column after collapse

of the bod buildin

Plate 8 Formwork distorted

Floor not

yet cast

Block ru

Plate 9 Reinforcement arrangement Plate 10 Reinforcement arrangement

concrete not et oured


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Three samples tagged A, B and C were tested. The average of the samples(A)showed that the sizes ranges between 10 mm to 14 mm,, while sample rangesbetween 20 to 30 mm and sample (C) between 14 mm to 20 mm. The fine sandwas sharp does not contain much fines (sizes less than 0.75mm is just 0.6 %).

Thus, it is not silty. Typical examples of the results are shown for the coarseaggregate in Table 1 and sharp sand analysis in Table 2.

Table 1 Coarse aggregate Sample ADiameter m Wt retained % retained % passing

31. 0.00 0.00 100.01 382.0 39.2 60.810 389.0 39.9 20.9

6.3 196.5 20.2 0.Pa 6.5 0.7 0.

From the result, the sizes are 10 mm to 14 mm

Table 2 Sharp sand analysis

Dia m Wt retained % retained % passing16.00 0.0 0.0 100.08.00 9.0 1.9 98.4.00 25.0 5.3 92.2.36 24.0 5.1 87.1.00 91.5 19.3 68.0.50 216.0 45.5 22.0.30 25.0 5.3 17.0.25 23.5 4.9 12.0.090 51.0 10.7 2.0

0.075 3.0 0.6 1.Pan 4.0 0.8 0.6

Reinforcement rods: The reinforcement rods used were observed adequate in sizesas employed in each members.

Foundation level:This cannot be seen but the collapse was not due to foundationfailure.

Form work:The formwork used is composed of mixture of bamboo of nominalsize 10 mm diameter and timber (bamboo) of nominal size 2inches (50 mm) by 3inches (75 mm). The spacing is nominally 600 mm. Slenderness ratio which isheight to minimum width are 3600/10= 36 for bamboo and 12x24/2 = 144 for thetimber. This shows that the scaffoldings are slender and prone to buckling failure

Collapse and direction: From above the applied load on the floor was greater thanthe resisting force which is an indication that the formwork props could not hold


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the applied loads, resulting to the collapse. The failure involved movement in thevertical and horizontal directions as shown in and plates 5 and 6 and Figure 1. Theresponse of the props which lead to the failure could be caused by sinking at theirsupports, side sway of the whole formwork or buckling of the props. But becausethe props are seated on the firm DPC, the most possible cause is the side sway ofthe props. This therefore shows that the formwork was not carefully selected,designed and even constructed.

The description of the collapsed floor:Plates 7 and 8 show that the casting of the

floor was not complete when the failure occurred. The schematic diagram of thefloor is presented in Figure 2, showing the part cast given by the shaded part in thatfigure. This little concrete pour assisted the collapse forcing it to follow thedirection of arrow also shown inFigure 2. This direction is where the concrete wasbeing poured. The deduction from this is that the collapse cannot be due to overstress of concrete or steel since the building was not yet put to use and thus theoverstress was on the formwork.

ARCHITECTS PERSPECTIVE

While the information given above is from the structural perspective, the view ofthe Architect is also included as follow, whle the set of drawing submitted forapproval purposes comprise of 13 sheets, thus:

i. The cover page Sheet 1;ii. The locational plan Sheet 2;iii. The name sheet Sheet 3;

Plate 12 Column already cast and

bamboo formwork

Plate 11 Full rubbles after failure


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iv. The site plan Sheet 4;v. The ground floor plan Sheet 5;vi. The first floor plan Sheet 6;vii. The second floor plan Sheet 7;viii. The roof plan Sheet 8;ix. The front elevation Sheet 9;x. The right-side elevation Sheet 10;xi. The back elevation Sheet 11;xii. The left-side elevation Sheet 12;andxiii. The plumbing details Sheet 13.

Observation 1:

(i) The cantilevered balcony were too deep for construction without support;

(ii) it was noted that one sheet was missing, or sheet No. 11 was omitted in theprocess of the numbering;

(iii) only three of the sheets were endorsed cover page (sheet 1), locational plan(sheet 2) and plumbing details (sheet 13);

(iv) the graphics with which the drawings were accomplished was unprofessional;and

(v) all the sheets of the set of drawing bore the stamp of the Town PlanningAuthority.

Observation 2: It was also observed from this perspective that:(i) The ground floor plan comprised an open space, two stairwells and 2 No.

one cubicle toilets. The windows were 1800 mm in length.(ii) At the first floor plan and in addition to what made up the ground floor, 2

No. cantilevered balcony with protrusion of 1200mm were attached.(iii) The boundary, peripheral walls were maintained, however on the second

floor plan, this floor, more partition walls were introduced. This floorcontained 3 offices, a resting room, kitchenette, office of the principals, anadjourning office for his secretary, two stairwells and 2 cubicle toilets. Inaddition, 2 cantilevered balconies, each with protrusion of 1200mm were

attached,while the roof plan shows simple and functional gable roof.

Interaction with the consultant architect: The architect did a design on officecomplex for the client but the drawing was not used. All the sheets of the set ofdrawing were sealed and endorsed. Rather than the client calling for amendmentsin areas not acceptable to him he decided on commissioning a draughtsman, whoproduced the design that was used on the construction site at Coca-cola Road. The


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draughtsman after the production of the drawings fished out the endorsed sheetsfrom the works of the architect.t these were the only three sheets that wereunaffected by the product of the draughtsman mentioned viz: cover page (sheet 1),locational plan (sheet 2) and plumbing details (sheet 13). The draughtsman beingthe one that produced the initial drawings took undue advantage of hiscloseness toarchitect and adopted the architects trademarks. Some architectural drawings areshown in Figures 3 to 7.

Figure 3 ground floor plan


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Figure 4 First floor plan

Figure 5 Second floor plan


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Figure 6 Back view

Figure 7 Left side view


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DISCUSSION

The response of the Town Planning Authority, the site visit made and the materialobservation and testing indicate that the building process did not pass through theright channel for approval and construction was badly handled. The arrangement ofthe props and the formworks, give the impression of inadequate supervision. Thisfailure could have been avoided if good formwork material was used and properlyconstructed with proper lateral support. Discussion with people on the collapsedstructure showed ineptitude on the part of the supervision personnel and theinadequacy in the process of approval of documents submitted for the purpose ofconstruction. Here is a project that was situated along a major road, yet theauthority vested with the power of regulating construction did not notice it towarrant issuance of Stop Work Order. Everyone dissociated himself fromknowledge of the drawings. Could the client, therefore, be playing pranks?

CONCLUSION

This report has been able to identify the major causes of the collapsed of thebuilding along Coca-cola Road in Ilorin, KwaraState. It identified the fact thatthere was a hidden agenda on the part of the client (who could not be reachedduring the course of this investigation), professionals in the building industry andthat poor workmanship contributed to the fatal collapse of that building underconstruction. It is possiblethat the following attributes could have influenced thefailure of the building:

inadequate formwork props to support the decking during pouring of concrete;

the absence of soil test report ;

no structural designs and details;

absence of co-ordination between the professional bodies and the local townplanning authority;

lack of adherence to specifications by the unqualified and unskilled personnel;

poor and bad workmanship ;

the use of substandard building materials especially formwork;

lack of proper supervision by professionals;

inadequate enforcement of the existing enabling building regulations; and,

flagrant disobedience of town planning regulations by developers/landlords.


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RECOMMENDATION

Having considered the remote causes of the collapse building structure, remedialactions such as those listed below could be used as preventive measures.

1. Stringent penalties should be applied to those responsible for collapse of thebuilding, particularly when loss of lives was involved.

2. Continuing professional development should be emphasised by both theprofessional bodies and the government on modern trends in the buildingindustry, to keep members of the building industry abreast with new trends inconstruction for appropriate procedural ethics in construction.

3. Government should screen those who were involved in the building project.

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Report _FNL_on a Collapse Building_Coca-Colar Rd in Ilorin

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