Report to Check From Engr. Awal

Consultant THE CIVIL AND STRUCTURESTitle STRUCTURAL ASSESSMENT OFSTEEL ROOFING SYSTEM OF DPS-STS SCHOOL (SENIOR

SECTION) OF STS GROUP

STRUCTURAL ASSESSMENT OFSTEEL ROOFING SYSTEM

OF DPS-STS SCHOOL (SENIOR SECTION)

OF STS GROUP

Revision History

0 Revision-0 (Original Issue ID:STS-01) 22.09.2015

Rev. Revision information Date

Originated and Prepared by Approved by

Engr. Sanjida Alam Sharna,BSc in Civil.

Mohammad Mahfuzur Rahman,MSc in Civil & Structural

Owner: TCS Page 1 of 19



SEP, 2015




1.0 SUMMARY

The structural design of Steel roofing system on DPS-STS School (Senior Section) of STS-GROUP, submitted by DOMINAGE STEEL BUILDING SYSTEMS (PVT) LTD (STS-Vendor) at JR,CaseroTower (11th Floor), 46,Mohakhali Comercial Area, Dhaka -1212 has found safe under all design load and load combination.

Design code is AISC ASD. Maximum allowed stress ratio is 1.33. Steel member tensile stress is 50ksi (ASTM A572). Ancholr bolt grade is 60ksi (Minimum). Concretr fc’ (Minimum) : 3500psi.

Recommendations along with necessary suggestions has made in drawing (i.e Weld data, Bolt grade, Stiffener requirement in main beam has written and shown in drawing seperately). Necessary corrections in the drawing has made and signed herewith.

2.0 SCOPE OF THE WORK:

Study of the design provided by one of STS-Group vendors including model, load schedule, structural drawing of steel roofing system in CAD.Study of project architectural drawings of the auditorium.Study of RC support system of the auditorium.Checking safety system of roof structures (Truss, Sub-beam, Bracing, purling, stiffener, roof sheeting etc.) with respect to wind & seismic load along with dead & live loads.Checking joint detailing with welded length & size along with specification of electrodes.Checking anchoring system (the size & no. of anchor bolts as well as the specification of bolts).Checking resistance adequacy of RC supporting members.

Deliverables:Recommendations along with necessary suggestions.Providing necessary corrections in the drawing.Corrected drawings.

3.0 STEEL STRUCTURE DESIGN CHECKING

Steel roofing system of DPS-STS SCHOOL (SENIOR SECTION) has designed using AISC AS Dcode. Steel fy is 50ksi. Maximum allowed design stress ratio is 1.33.

Loads (Dead, Live and Wind loads)Common Values

Cc 0.0000472 Ci 1

Vb 210 Cg 1.309 Exp-A




Width 1 8.00 mWidth 1 1.25 m

Total (kN/m)

DL 1 1.44 kN/m2 11.52DL 2 4.18 kN/m2 5.23LL 1 1.20 kN/m2 9.60LL 2 1.2 kN/m2 1.50

4.0 LOAD (LOAD UNIT: KN, METER):

Figure: Dead load on the structure (kN-m)

Figure: Live load on the structure (kN-m)




Figure: Wind load on the structure (kN-m)

5.0 MEMBER CAAPCITY & DESIGN STRESS RATIO

Figure: Design stress ratio.




Figure: Design stress ratio (Blow-up).




6.0 MEMBER & CONNECTION / JOINT DESIGN CALCULATION

(A) MAIN BEAM

Member Forces

Figure: Moment diagram

Figure: Moment Values (Load Case 7: kip-ft)

Figure: Axial Force Values (Load Case 7: kip-ft




Input Data: 750 10 450 25 Member Data: Member Properties: Y

d = 29.528 A = 45.73 in.^2 tw = 0.394 d = 29.53 in. bf = 17.717 tw = 0.39 in. tf = 0.984 bf = 17.72 in.

tf = 0.98 in.

Member Loadings: rt = 4.87 in. d = 29.5275590551181

X

P = 25.00 d/Af = 1.69

Mx = 540.00 Ix = 7792.89 in.^4

My = 0.00 Sx = 527.84 in.^3

rx = 13.05 in. bf = 17.7165354330709

Design Parameters: Iy = 912.34 in.^4

Fy = 50.00 Sy = 102.99 in.^3 Built-Up SectionKx = 1.00 ry = 4.47 in. Qs = 1.000Ky = 1.00 wt./ft. = 155.59 lbs./ft. Qa = 1.000Lx = 65.000 Ly = 20.000 Lb = 20.000 Cb = 1.70

Cmx = 0.85 Cmy = 0.85 ASIF = 1.000

Results:

For Axial Compression:For X-axis Bending: For Y-axis Bending:

Kx*Lx/rx = 59.75 Lc = 15.87 ft. fby = 0.00Ky*Ly/ry = 53.73 Lu = 19.69 ft. Fby = 37.50

Cc = 107.00 Lb/rt = 49.30 Mry = 321.85fa = 0.55 fbx = 12.28 ksi

Fa = 22.76 Fbx = 30.00 ksi Pa = 1040.72 Mrx = 1319.60 ft-kips

X-axis Euler Stress: Y-axis Euler Stress:

F'ex = 41.83 ksi F'ey = 51.73

S.R. = 0.433

(B) SUB BEAM




Member Data: Member Properties:

d = 12.795 in. A = 6.73 in.^2

tw = 0.197 in. d = 12.80 in.

bf = 6.890 in. tw = 0.20 in.

tf = 0.315 in. bf = 6.89 in.

tf = 0.31 in.

Member Loadings: rt = 1.83 in.

P = 4.00 kips d/Af = 5.90

Mx = 55.00 ft-kips Ix = 198.57 in.^4

My = 0.00 ft-kips Sx = 31.04 in.^3

rx = 5.43 in.

Design Parameters: Iy = 17.18 in.^4

Fy = 50.00 ksi Sy = 4.99 in.^3

Kx = 1.00 ry = 1.60 in.

Ky = 1.00 wt./ft. = 22.92 lbs./ft.

Lx = 30.000 ft. Ly = 10.000 ft. Lb = 10.000 ft. Cb = 1.70

Cmx = 0.85 Cmy = 0.85 ASIF = 1.000

Results: For Axial Compression:

For X-axis Bending:

Kx*Lx/rx = 66.30 Lc = 5.65 ft.

Ky*Ly/ry = 75.14 Lu = 6.88 ft.

Cc = 107.00 Lb/rt = 65.64 fa = 0.59 ksi fbx = 21.26 ksi

Fa = 19.97 ksi Fbx = 29.19 ksi

Pa = 134.47 kips Mrx = 75.50 ft-kips

X-axis Euler Stress:

F'ex = 33.97 ksi

Stress Ratio:

S.R. = 0.758Eqn. H1-3

CONNECTION DESIGN




A) Base Plate & Welding calculation

Load Name Developed Load

Permissible Load from Excel Calculation

Comments

Tension 220kN 93.31*16 No Bolt = 1492 kN SAFE

Compression 220kN 93.31*16 No Bolt = 1492 kN SAFE

Shear 105kN 48.07*16 No Bolt = 770 kN SAFE

Moment 460kN Moment has converted to Compression & tension force by code specified calculation.

SAFE

Welding DataWelding Amount (Provided)

Welding Amount (Required)

13mm 1.03mm

Controlling Forces

Horizontal Shear (V) = 105 kN

Vertical (P) = 220 kN

Moment (M) = 460 kNm

Column Section

Grade = A572

Tensile Strength (Fu) = 59.85 kN/cm2




Yeild Stress (Fy) = 45.89 kN/cm2

Width Thk.

Top Flange (bf1) (tf1) = 520 25 mm

Web (dw) (tw) = 760 10 mm

Bottom Flange (bf2) (tf2) = 520 25 mm

Connection Details

Connection Code = STS1

Bolt Grade = A572

Tensile Strength (Fu) = 59.85 kN/cm2

Allowable Tensile Stress (Ft) = 19.75 kN/cm2

Allowable Shear Stress (Fv) = 10.17 kN/cm2

Bolt Diameter (db) = 30 mm

Number of Bolts (n) = 16 mmBolt Center to Flange Outside

(Cw) =10 mm

Bolt Center to Plate Edge (ed1) = 10 mm (Along Length)

Bolt Center to Plate Edge (ed2) = 10 mm (Along Width)

Bolt Pitch (p) = 10 mm

Bolt Gauge (g) = 200 mm

Base Plate Length (N) = 870 mm

Base Plate Width (B) = 520 mmDistance Edge to CG of Bolts (m)

=20 mm

Bolt CG to Center of Column (f) = 415 mm

Estimate

Weight of Connection Plates = 162.52 kgs.

Weight of Anchor Bolts = 98.11 kgs.

260.63 kgs.

Concrete Data

Mix Grade = M25

Compressive Strength (fc') = 2.50 kN/cm2

Weld Data

For E70XX Electrode (Fu) = 48.23 kN/cm2

Allowable Stress in weld = 0.3 x Fu kN/cm2

Allowable Stress in weld (Fw) = 14.47 kN/cm2

Anchor Bolt

Force in Bolt Group = P / 2 ± M / ( dw + tf1 / 2 + tf2 / 2 )


b



Compression (C) = 695.99 kN

Tension (T) = 475.99 kN

Force per Bolt

Compression / Bolt (Cb) = 87.00 kN 2 C / n

Tension / Bolt (Tb) = 59.50 kN 2 T / n

Shear / Bolt = 6.56 kN V / n

Compression Capacity = 93.31 kN Fc x Ab

Tensile Capacity = 93.31 kN Ft x Ab

Shear Capacity = 48.07 kN Fv x Ab

Pull Out Capacity = 70.73 kN [ ( p x db ) x Le ] x u x n

Calculated Shear Stress / Bolt (fv) =

0.93 kN/cm2 V / Ab n

Allowable Tensile Stress with Shear (Ts) =

13.20 kN/cm2 [ ( 0.43 Fu ) - ( 1.8 fv ) ]

Tension Capacity with Shear = 93.31 kN Ts x Ab x n

Base Plate

Dimension (a) = 100 mm g / 2

Dimension (b) = 10 mm Cw

Bolt Force to Flange = a3 / ( a3 + b3 ) x Tb

Bolt Force to Flange (Pfb) = 86.91 kNEffective width along Flange (bfm)

=20 mm 2 Cw

Moment (Mf) = 0.87 kNm Pfb x Cw

Plate Thickness Required (tp) = sqrt ( 6 M / 0.75 Fy bfm )

Plate Thickness Required (tp) = 31.74 mm Use Allowable Tensile Stress in Flange

=20.70 kN/cm2

Total Force in Flange (Pf) = 695.29 kNCalculated Tensile Stress in

Flange =5.35 kN/cm2 Pf / ( bf x tf )

Size of Flange Fillet Weld Required =

6.54 mmPf / ( 0.707 x Fw x 2 x bf )

Bolt Force to Web / Gusset = b3 / ( a3 + b3 ) x Tb

Bolt Force to Web / Gusset (Pwb) = 0.09 kN

Effective width along Web (bwm) = 200 mm

Moment (Mw) = 0.01 kNm

Plate Thickness Required (tp) = sqrt ( 6 M / 0.75 Fy bwm )

Plate Thickness Required (tp) = 1.00 mm Use

Total Force in Web / Gusset (Pw) = 0.17 kN

Web Tension Stress = Pw / ( tw x bwm )

Web Tension Stress = 0.01 kN/cm2 Pw / ( bwm x tw )

Size of Web Fillet Weld Required 0.00 mm Pw / ( 0.707 x Fw x 2 x




= bwm )Gusset Plate

Tension Side Flange Gusset

Thickness (ts) = 25 mm

Height (hs) = 250 mm

Length (ls) = 20 mm

Angle (ø) = 85.43 Deg

Dimension (D1) = 15 mm

Tension Force in Gusset (Pg) =Pw / Sin

øTension Force in Gusset (Pg) = 0.17 kN

Calculated Tensile Stress = Pg / [ ts x D1 x ( Sin ø )2 ]

Calculated Tensile Stress = 0.05 kN/cm2 Pg / [ ts x D1 x ( Sin ø

)2 ]

Compression Side Flange Gusset

Effective Length (Ls) = 242.82 mm

Effective width (De) = 14.95 mm

Effective Area (As) = 3.74 cm2

Ixx = 0.70 cm4 D1 x Sin ø

rxx = 0.43 cm De x ts

k = 0.75 ts x De3 / 12

k Ls / r = 42.19 sqrt ( Ixx / As )

Allowable Compressive Stress = 23.42 kN/cm2

Compression Force in Gusset (Pg) =

0.17 kN

Calculated Compressive Stress = Pg / ( ts x D1 x ( Sin ø )2

Calculated Compressive Stress = 0.05 kN/cm2

Welds to Flange Gusset

Effective Length of Weld (Lw) = 2 D1

Effective Length of Weld (Lw) = 30 mmSize of Gusset Fillet Weld

Required =0.92 mm

Welds to Column Web for Shear

Effective Length of Weld (Lu) = 750 mmSize of Web Fillet Weld Required

=1.03 mm

B) END PLATE MOMENT CONNECTION

Desing Loads




Picture: Moment value for DL+LL combination (Unt: kN-m)

Picture: Axial force value for DL+LL combination (Unt: kN-m)

Picture: Shear force value for DL+LL combination (Unt: kN-m)

Connection Calculation

Moment End-Plate Connection Design (Flush Type)Owner: TCS Page 14 of 19



Design Forces

Design Moment M = 30 kNm 266 k-in

Design Shear V = 7 kN1.57 kips

Axial force P = 75 kN16.86

kips*-*ve for comression and *+*ve for tension

Consider

End-late material yield stress, Fpy= 275 N/mm^2 39.9 ksiAllowable shear stress of bolts= 72 N/mm^2 10.4 ksi

Nominal Tensile strength of Bolts, Ft= 785 N/mm^2 90.0 ksi ,90 ksi for A 325, 113 ksi for A490φ= 0.75

φb= 0.90

Geometric Design Data

Width of flange, bf = 140.00 mm5.51 inch

End plate width, bp = 175.00 mm6.89 inch

Thickness of flange, tf = 5.00 mm0.20 inch

Bolt gage, g = 140.00 mm5.51 inch

pf = 60.00 mm2.362

inch

pb = 100.00 mm3.94 inch

h= 350.00 mm13.78

inch

Web thickness, tw 4.00 mm0.16 inch

Number of rows of bolt,n = 4 (Max, n=10)

∑dn= 530 mm 20.87 inch

h1= 285 mm 11.2 inch

hn= -18 mm -0.7 inch

γr = 1.25 for flush connections

Maxial= P/2*(h-tf)

= 13 kNm 114.51 k-in




M= M+Maxial

= 43 kNm 380 kips

Mu= 1.5*(M+Maxial)

= 64 kNm 570.1 k-in

Flange Force, Ff= M/(h-tf)= 121 kN 27.19 kips

1. required bolt dia, db,req

= (2*Mu /(∏*φ*Ft*∑dn))^0.5= 12.9 mm 0.508 inch

Acceted, db = 13 mm 0.5 inch

2. Solve for end plate thickness, tp,reqd,

s= 1/2*(bp*g)^0.5= 78 mm 3.08 inch

pf = 60.00 mm 2.36 inch ≤ sY= bp/2*(h1/pf+h2/s)+2/g*(h1*(pf+0.75pb)+h2*(s+0.25*pb)) + g/2

= 1588 mm 62.5 inch

Pt= ∏*db2*Ft/4

= 82 kN 18.52 kips

φMnp= φ(2*Pt*(∑dn))= 57 kNm 508.5 k-in

tp,reqd = sqrt(1.1*γr*(φMnp)/(φb*Fpy*Y))= 14.2 mm 0.558 inch

Use, tp = 15.0 mm 3. Check for Shear

Shear per bolt (V/(2*n)) = 0.20 kips 1 kN

Shear capacity per bolt = 2.15 kips 10 kN≥ Applied shear per bolt ok

4. Weld designa) Top Flange to end plate weld

Dreqd= Ff/((2*(bf -tf)-tw)*0.928)= 2.8 sixteenths

Use 3 /16 inch fillet welds




b) Beam web to end plate weld

D= 0.6*Fy*tw/(2*0.928)2.03 sixteenths

Use 3 /16 inch fillet welds

Provided Bolt Dia: 8-16dia boltProvided end plate thickness: 15mm




STEEL STRUCTURE AT ROOF:

Steel structure at roof needs bracig. Bracing arrangement has been added in APPENDIX B.

6.0 CONCLUDING REMARKS

The structure was modeled using 3-D computer program ETABS and designed for all possible load combinations. The following observations have been done.

The maximum unfactored top deflection is 2.0inch which is less than the allowable limit of 2.7inch. Hence it is safe and stable from deflection point of view.

The factory has a basement floor 6 ft below the road level. The foundation of the factory building is on 24” thick raft foundation on the left portion. The punching shear stress in the raft is 93 psi, which is less than allowable punching shear stress 109 psi for concrete strength 3000 psi (i.e Actual core test data was 3390psi). The reinforcement provided in the mat foundation is also found satisfactorily from flexural moment. It has a pile foundation part as well, that has also found safe from all load and load combination.Pile foundation is on 18” dia 45 ft long piles, pile cap with 12” thick basement floor slab, that acting together, will be enough to carry the load from above.

The reinforcement provided at ground floor columns are found adequate for all columns except few as marked in section 5.7. Those underreinforced column will be strengthened. Provided reinforcement in all columns at other floor levels are also found more than the required reinforcement.

The typical floor roof slab is flat slab and two way beam supported slab. The maximum panel size is 21’-4” x 15’-0” and the thickness provided 8” is adequate as per BNBC / ACI Code. For smaller panel sizes, provided thickness is adequate. The reinforcement provided in typical floor roof slab is different in different location which is adequate forom design point of view. Slab punching check also shows satisfactory as per ACI code. Required beam reinforce is less than provided reinforcement.

REFERENCESBNBC (2006), Bangladesh National Building Code (BNBC), Dhaka, Bangladesh.ACI (1999), “Building Code Requirements for Structural Concrete”, ACI 318-99, American Concrete Institute, Detroit, USA.





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