Structural Analysis and Design of Community Building STRUCTURAL REPORT ON Detailed Engineering Survey, Soil Investigation, Detailed Design, Cost Estimate & Report Preparation of Naulo Bihani Nepal Community Building at Ward N0-4 in Kamal Municipality, Jhapa, Koshi Province, Nepal By SKY Engineering & Trading Pvt. Ltd. Kathmandu, Nepal 1 Structural Analysis and Design of Community Building 1. INTRODUCTION To make a Community building structurally sound, it is very important that the structural designer is consulted before its construction. The structural engineer, then works out the structural schemes and also gives the sizes of the structural members like beam, column, slab, etc. A Community building needs to be designed for all loads acting on it. Detailed structural designs are carried out and working drawings are to be prepared. Safety is the prime concern of the structural design. Serviceability and economy are other basic requirements that need to be considered during structural designing. The Community building should be designed not only for vertical loads but also for horizontal loads such as wind and earthquake loads. The structural designer has to take care of the safety of the Community building against the loads mentioned above. He is concerned in designing both superstructure and the substructure of the Community building. A Community building must be strong enough to transfer all the loads acting on it safely to the ground. It should be able to withstand all loads acting on it. Nepal lies in an earthquake prone zone. It is located in the boundary between Indian plate and Tibetan plate. Thus, Nepal experiences earthquakes frequently. Earthquakes are the most sudden, dramatic and devastating natural disasters. Although they last only for few seconds to minutes, they are the most devastating ones. Past records of the earthquake shows 18 major earthquakes have hit Nepal till now. So, designing of Community building against earthquake forces apart from other forces is a must in case of Nepal. Designing Community building against earthquake forces does not mean that we are making the Community building proof against it. Although, we can design such robust structure, it would be too expensive to build. It would be far cheaper to rebuild the Community building again instead of making it proof against earthquake. Hence, the Community buildings are made seismic resistant rather than seismic proof. According to this philosophy, no matter how much severe earthquake occurs, the Community building won’t collapse although it may be irreparably damaged. In, this background, it is ensured that this Community building has been designed to withstand all the acting loads including the earthquake making it seismic resistant. The structural design alone is not enough to ensure the safety of the Community building, equally important is its construction. The role of the contractor is of paramount importance as he is the one to execute the construction work at the site. He is required to execute the work according to the drawings supplied by the consultant to him and detailing has to be carefully followed. A large percentage of failure of the Community building is attributed to poor quality of construction. Past experiences from damages have shown that quality of material and workmanship plays an important role in good seismic behavior of the Community buildings. Hence, quality assurance in construction is expected to gain good seismic performance. 2 Structural Analysis and Design of Community Building 2. DESCRIPTION OF THE COMMUNITY BUILDING General features: Project: Detailed Engineering Survey, Soil Investigation, Detailed Design, Cost Estimate & Report Preparation of Naulo Bihani Nepal Community Building at Ward N0-4 in Kamal Municipality, Jhapa, Koshi Province, Nepal Architectural features: Type of Building: Community building Number of Floors: 3 floors Height of Storey: 3m Total Height of the Community building: Wall and Partition: 9m Masonry Walls Figure 1: Architectural Plan of Community building 3 Structural Analysis and Design of Community Building Structural features: Structural System: RCC Frame Structure Foundation Type: Isolated Square Footing Square Columns: 400mm* 400mm Primary Beams: 300mm*550mm Slab: Two-way slab 150 mm Staircase Slab: 175 mm Geotechnical Features: Soil Type: C (as per NBC:105-2020, part-1) Seismic Zone Factor: 0.3 Material Grade of concrete: M25 for column, beam, staircase and Slab and footing. Grade of steel: Fe 500 Unit weight of concrete = 25 kN/m3 Unit weight of the masonry wall= 19 KN/ m3 Young’s Modulus of Elasticity = 5000 √fck Poisson’s Ratio = 0.20 for concrete and 0.3 for rebar 4 Structural Analysis and Design of Community Building 3. MODELING, ANALYSIS AND DESIGN I. Modeling Since this is a Special Moment Resisting Frame structure, the main components to be modeled are: Beams and Columns. Slab are also modeled in frame and live load are assigned in slab whereas staircase dead and live load are calculated and assigned in frame. The analysis software used for modeling the structure is the ETAB 2000 v 19.0.0. The model map of the Community building is as shown in the figure. Fig 1: Three-dimensional view of the Community building in ETAB 5 Structural Analysis and Design of Community Building Dead Loads Dead loads are assumed to be produced by slab, beams, columns, walls, parapet walls, staircase, plasters and mortars, floor finish and water tank. The weight of Community building materials are taken as per IS 875(Part 1)-1987). Specific weight of materials [Ref: IS: 875(Part 1)-1987)] Materials Unit weight(γ) Reinforced Concrete 25.00 KN/m³ Brick Masonry with plaster 22.00 KN/m³ Floor Finishing (Screeding & punning) 23.00 KN/m³ Cement Sand Plaster 20.40 KN/m³ Floor finishing (Marble) 26.00 KN/m³ Live loads According to code, Live load for public Community building , For Community = 3 kN/m2 Corridor = 4 kN/m2 Meeting room and Hall = 5 kN/m2 Seismic Loads The loads calculated are applied in the modeled Community building. Besides from the dead and live loads, the probable seismic loads are also taken care of as Nepal is categorized amongst seismically active zones. Moreover, the Community building itself carries high importance and the seismic force consideration is of upmost priority. The Community building is Three storied and the static analysis is enough to ensure its safety against earthquake, but the dynamic analysis is also carried out and checked in some respect considering the maximum safety requirement in this type of Community building. Through consideration is given in analysis and design of the Community building following standard theories of structures and relevant codes of practice. 6 Structural Analysis and Design of Community Building A three-dimensional linear static analysis has been carried out using the standard software ETAB 19.0.0 The Structure is assumed to be fixed at the Plinth level. The brick wall is considered as the filler wall only. The beams are modeled as rectangular beams. The flange effect of the beams has been neglected. Center to center dimension of the structure has been considered in the analysis. The rigid end effect has also been considered in the analysis. The following load cases and combinations were used for the analysis of the structural components of the Community building. Load Cases Following loads have been considered in the analysis of the Community building as per IS 456-2000 and NBC:105-2020. 1. Dead Load (DL) 2. Live load (LL) 3. Earthquake Load in +ve X-direction 4. Earthquake Load in –ve X-direction 5. Earthquake Load in +ve Y-direction 6. Earthquake Load in –ve Y-direction Load Combination Following load combinations have been adopted as per NBC:105-2020. Design Assumptions Concrete Grade, M25 fck = 25 MPa for all member Steel Grade, Fe 500 fy = 500 MPa for all The concrete has been designed using limit state method based on IS 456 –2000. The detailing of reinforcement has been based on IS 13920 –1993 and NBC:105-2020 for detailing of reinforcement. • The design has been based on the most critical load combination mentioned above. 7 Structural Analysis and Design of Community Building NBC:105-2020 COMPLIANCE CHECK All Member Passed from ETABS analysis. 8 Structural Analysis and Design of Community Building FROM ETAB Response Spectrum Method is used for earthquake load calculation. 9 Structural Analysis and Design of Community Building For Load EQY in Ultimate State at Third Floor For RES_EQX_Ultimate ∆max = 18.218, ∆min = 14.501 and ∆max/∆min= 1.26 <1.5 For RES_EQY_Ultimate ∆max = 20.089, ∆min = 19.683 and ∆max/∆min= 1.02 <1.5 For RES_EQX_Servicibility ∆max = 17.442, ∆min 13.883 = and ∆max/∆min= 1.26 <1.5 For RES_EQY_Servicibility ∆max = 19.234, ∆min = 18.845 and ∆max/∆min= 1.02 <1.5 10 Structural Analysis and Design of Community Building Maximum Inter Storey Deflection for RES_EQX_Ultimate = Ductilty Factor Rμ = Maximum Inter Storey Deflection for RES_EQX_Ultimate = 0.001619 4.00000 0.00647 <0.025 Maximum Inter Storey Deflection for RES_EQY_Ultimate= Ductilty Factor Rμ = Maximum Inter Storey Deflection for RES_EQX_Ultimate = 0.002381 4.00000 0.00952 <0.025 Maximum Inter Storey Deflection for RES_EQX_Ser = Maximum Inter Storey Deflection for RES_EQY_Ser = 0.0016 <0.006 0.0015 <0.006 11 Structural Analysis and Design of Community Building 12 Structural Analysis and Design of Community Building SAMPLE BEAM DESIGN OUTPUT FROM ETABS IS 456:2000 + IS 13920:2016+NBC 2020 Beam Section Design Beam Element Details Type: Ductile Frame (Summary) Level Element Unique Name Section ID Combo ID Station Loc Length (mm) LLRF Story1 B47 139 B300*550 DL +0.3*LL- EQX ULT 200 5000 1 Section Properties b (mm) h (mm) b f (mm) d s (mm) d ct (mm) d cb (mm) 300 550 300 0 25 25 Material Properties Ec (MPa) fck (MPa) Lt.Wt Factor (Unitless) fy (MPa) fys (MPa) 25000 25 1 500 415 Design Code Parameters ɣC ɣS 1.5 1.15 Factored Forces and Moments Factored Mu3 kN-m Factored Tu kN-m Factored Vu2 kN Factored Pu kN -62.1533 16.1423 64.2197 0 Design Moments, M u3 & Mt Factored Moment kN-m Factored Mt kN-m Positive Moment kN-m Negative Moment kN-m -62.1533 26.9039 32.0078 -89.0572 Design Moment and Flexural Reinforcement for Moment, M u3 & T u Design -Moment kN-m Top (+2 Axis) Design +Moment kN-m -Moment Rebar mm² -89.0572 Bottom (-2 Axis) 32.0078 +Moment Rebar mm² Minimum Rebar mm² Required Rebar mm² 412 0 412 378 378 143 0 378 Shear Force and Reinforcement for Shear, V u2 & T u Shear Ve kN Shear Vc kN Shear Vs kN Shear Vp kN Rebar Asv /s mm²/m 102.197 0 188.2894 53.0182 993.84 Torsion Force and Torsion Reinforcement for Torsion, T u & VU2 Tu kN-m Vu kN Core b 1 mm Core d 1 mm Rebar Asvt /s mm²/m 16.1423 64.2197 270 520 499.93 13 Structural Analysis and Design of Community Building SAMPLE COLUMN DESIGN OUTPUT FROM ETABS IS 456:2000 + IS 13920:2016+NBC 2020 Column Section Design Column Element Details Type: Ductile Frame (Summary) Level Element Unique Name Section ID Combo ID Station Loc Length (mm) LLRF Story3 C2 66 C400*400 DL +0.3*LL-EQYULT 2450 3000 0.984 Section Properties b (mm) h (mm) dc (mm) Cover (Torsion) (mm) 400 400 58 30 Material Properties Ec (MPa) fck (MPa) Lt.Wt Factor (Unitless) fy (MPa) fys (MPa) 25000 25 1 500 415 Design Code Parameters ɣC ɣS 1.5 1.15 Axial Force and Biaxial Moment Design For P u , Mu2 , Mu3 Design Pu kN Design M u2 kN-m Design M u3 kN-m Minimum M 2 kN-m Minimum M 3 kN-m Rebar Area mm² Rebar % % 76.3747 -233.7483 24.6583 1.5275 1.5275 4410 2.76 Axial Force and Biaxial Moment Factors K Factor Unitless Length mm Initial Moment kN-m Additional Moment kN-m Minimum Moment kN-m Major Bend(M3) 0.805174 2450 -13.4669 0 1.5275 Minor Bend(M2) 0.694462 2450 10.2031 0 1.5275 Shear Design for Vu2 , Vu3 Major, V u2 Minor, V u3 Shear Vu kN Shear Vc kN Shear Vs kN Shear Vp kN Rebar Asv /s mm²/m 77.9161 155.8322 109.6198 109.6198 54.7195 54.7195 77.9161 155.8322 443.37 443.37 Joint Shear Check/Design Joint Shear Force kN Shear VTop kN Shear Vu,Tot kN Shear Vc kN Joint Area cm² Shear Ratio Unitless 14 Structural Analysis and Design of Community Building Joint Shear Force kN Shear VTop kN Shear Vu,Tot kN Shear Vc kN Joint Area cm² Shear Ratio Unitless Major Shear, V u2 0 0 164.3478 960 1600 0.171 Minor Shear, V u3 0 0 328.6956 960 1600 0.342 (1.4) Beam/Column Capacity Ratio Major Ratio Minor Ratio 0.465 0.929 Additional Moment Reduction Factor k (IS 39.7.1.1) Ag cm² Asc cm² Puz kN Pb kN Pu kN k Unitless 1600 44.1 3453.8229 820.7974 76.3747 1 Consider Ma Length Factor Section Depth (mm) KL/Depth Ratio KL/Depth Limit KL/Depth Exceeded Ma Moment (kN-m) Major Bending (M 3 ) Yes 0.817 400 4.932 12 No 0 Minor Bending (M 2 ) Yes 0.817 400 4.254 12 No 0 Additional Moment (IS 39.7.1) SAMPLE SLAB DESIGN DESIGN OF SLAB Slab thickness Slab effective depth Concrete Steel Loading Slab Load Dead Load Live Load Floor Finish Other Load Total Load Factored Load Length of longer span(ly) Length of shorter span(lx) Ration of spans Type of slab to be designed D 150 mm d fck fy 125 mm 25 MPa 500 MPa DL LL FF OL Ws 3.75 KN/m 5.00 KN/m 1.50 KN/m 1.00 KN/m 11.25 KN/m Wsu 17 KN/m ly (lx) 6.00 5.00 ly/lx two way 1.20 αx(+) 0.0490 m m Based on type of slab & ratio of span valued added from table 26 of IS456 Moment coefficient for shotrer direction 15 Structural Analysis and Design of Community Building 0.0650 Moment coefficient for longer direction αx(-) αy(+) Moment coefficient for longer direction αx(-) 0.0470 My(+) My(-) Mx(+) Mx(-) Mmax 14.77 19.83 20.67 27.42 KN/m KN/m KN/m KN/m 27.42 KN/m 90.81 mm 406.85 mm2 389.06 406.85 mm2 mm2 553.60 mm2 Ø Astx(1) s Astx(p) 10.00 78.54 125.00 628.30 mm L/d L/d 48.00 26.00 Moment coefficient for shotrer direction 0.0350 CALCULATION OF MOMENT Moment for longer direction Moment for longer direction Moment for shorter direction Moment for shorter direction Maximum Moment= Effective Depth of slab required= CALCULATION OF STEEL REQUIRED Ast = 0.5 f ck é 4 .6 M u ù ê1 - 1 ú bd f y ëê f ck bd 2 ûú Asty(+) Asty(-) Astx(+) Astx(-) Area of steel required in longer direction for +ve moment Area of steel required in longer direction for -ve moment Area of steel required in shorter direction for +ve moment Area of steel required in shorter direction for -ve moment AREA OF STEEL PROVIDED Astx(p) AREA OF STEEL PROVIDED dia. Of bar used area of 1 bar spacing AREA OF STEEL PROVIDED CHECK FOR DEFLECTION Span to depth Ratio Basic Span to depth Ratio Modification Factor (k1) calculatin Pt= (L/d)max (L/d)basic Kf fs kt Kc mm 0.50% = = = = = = (Refer Clause:23.2.1 IS456-2000) (L/d)*Kt*Kc*Kf 26 1.5 256 1.200 1 (Refer Figure:4 IS456-2000, Page-38) (Refer Figure:4 IS456-2000) (Refer Figure:5 IS456-2000) 16 Structural Analysis and Design of Community Building (L/d)max L/d= = 46.8 40.00 Hence Safe DESIGN OF STAIRCASE 1 GENERAL INFORMATION Staircase type fy 500.00 N/mm2 fck 25.00 N/mm2 Cover 20.00 mm Diameter of main bars 12.00 mm Diameter of distribution bars 12.00 mm Tread 0.300 m Rise 0.165 m Thickness of waist slab 0.150 m Width of slab 1.500 m Width of landing 1.500 m Thickness of landing slab 0.150 m Span of landing 1 0.000 m Span of flight 1.800 m Span of landing 2 1.500 m Total Span 3.300 m Area of slab 0.051 m2 Area of step 0.025 m2 Total area 0.076 m2 DL per m 1.903 KN/m DL 6.342 KN/m2 FF 1.500 KN/m2 LL 4.000 KN/m2 Total load per m square 11.842 KN/m2 Factored load 17.763 KN/m2 Load per meter 26.645 KN/m 2 LOAD CALCULATION 2.1 LOAD ON WAIST SLAB 2.2 Open-well LOAD ON LANDING 17 Structural Analysis and Design of Community Building 3 Self weight of slab 3.75 KN/m2 FF 1.00 KN/m2 LL 4.00 KN/m2 load per meter square 8.75 KN/m2 Factored load 13.13 KN/m2 load per meter 19.69 KN/m CALCULATION OF MOMENTS 26.65 19.69 19.69 0.000 1.80 1.500 From manual calculation, we have ; R1= 41.59 KN R2 = 35.90 KN The point of zero shear force is obtained at x = Mmax. = 4 5 6 32.46 1.561 m from left support KNm DEPTH Effective depth from moment consideration 0.079 m Overall depth provided 0.150 m Effective depth 0.124 m Ast 647.16 mm2 Diameter of steel 12.00 mm Area of each steel 113.10 mm2 Spacing required 262.14 mm Spacing provided 150.00 mm Actual steel 1130.97 mm2 CALCULATION OF MAIN STEEL CALCULATION OF DISTRIBUTION STEEL Ast 270.00 mm2 Diameter of steel 12.00 mm Area of each steel 113.10 mm2 18 Structural Analysis and Design of Community Building 7 8 9 Spacing required 628.32 mm Spacing provided 150.00 mm Actual steel 1130.97 mm2 Vu 41.59 KN Ꚍv 0.22 N/mm2 Pt 0.61 % Ꚍc 0.675 N/mm2 Ꚍ'c=k*Ꚍc 0.8775 N/mm2 Check Safe in shear CHECK FOR SHEAR CHECK FOR DEVELOPMENT LENGTH Ld in terms of Ø 48.55 M1 56.73 KNm V 41.59 KN Lo(ancorage required) 124.00 mm Ld 1487.98 mm Ø< 30.65 mm Result Safe DEFLECTION CHECK Span Length (L in m) As per IS 456(Clause 34.1.1) 2.800 Breadth (b) (mm) 1500 Depth (D) (mm) 150 d (mm) 124.00 2 25.00 2 500.00 fck (N/mm ) fy (N/mm ) Moment (M) KNm 32.463 2 Ast(reqd) mm 647.163 2 1130.973 Ast(prov) mm Ast % (Pt) Service stress (fs) N/mm 0.61 2 165.944 23 α β γ δ λ 1.602 Permissible L/d = αβγδλ 36.846 1 1 1 19 Structural Analysis and Design of Community Building Required depth(d) 75.992 Actual L/d 22.581 Check Safe DESIGN OF ISOLATED FOOTING Design of Isolated Square Footing Here b 2 Fck= fy= 25 N/mm 500 N/mm2 colmsize= d 450 * 450 mm 150 kN/m2 safe bearing capacity of soil = depth of excavation = Axial load = Total weight on soil= 1.5 765 kn 841.5 kn area of footing required = 5.61 m2 = Required length and breath 2.37 * 2.37 footing provided footing size = 2.50 * thus provided area = 6.25 m2 The net earth pressure acting upward due to factored load is Pu= 2.50 m 184 kN/m2 0.18 N/sq.mm where 1.5 is partial safety factor Shear in one way action the critical section is taken as distance d away from the face of column l 1.025 Now effective depth required is MM 406.47 D depth MM 450 d effective depth MM 394 (L) Check for Bending Moment Bending moment about an axis x-x passing through the face of column = 241.64 knm Now effective depth required is d = BM 0.138 * fck * b = 170.5 mm OK Now area of tension steel is given by Area of reinforcement (Ast) BM= 0.87 fyAst * (d - fyAst ) fck b 20 Structural Analysis and Design of Community Building where , Bm = fy = d= fck = b= 241.64 knm 500 394 25 2.5 m by solving Ast = 1453 mm 1477.5 mm2 minimum reinforcement Ast= design Ast= 2 1477.5 Shear in two way action The critical section is taken at a d/2 distance away from the face of the column A2= 0.712 Now shear force Vu= 184[6.25-0.712336] = 1018.93 kn shear strength of M 25 concrete τ'c = ks *τc ks= 0.5+ βc = ks= = thus Ks = βc longer side of column/shorter side of column 0.5+1 ks≤1 1.5 1 thus τ'c =τc = 0 . 25 fck 1.25 shear resistance= 1662.68 ok Load transfer from column to footing Nominal bearing stress in column = 1.5*765*1000/(450*450) 5.666667 N/mm2 = Allowable bearing stress = 0.45*√fck 11.25 N/mm2 = now Excess load = -1130625 N -3375 mm2 Area of steel required As = 2 Minimum Ast=0.5% of column area = 1012.5 mm thus no additional dowel bars are required to tranfer load additional Ast = No dowel bars are needed Arrangement of bars for foundation slab dia of bars used = NO of bars required = spacing of reinforcement required = spacing of reinforcement provided= dia of bar used = Development length = available L = 16 mm 8 312.5 mm c/c 150.0 mm c/c 16 tension 725 mm 1475 OK for compression 446.6666667 21 Structural Analysis and Design of Community Building 4. CONCLUSION After the analysis of the Community building components, the Community building is found to be safe against the loads considered above. The Axial force, moment, Shear force and torsional forces are checked at different sections of the beams and columns using ETAB. All the sections are found to be stressed within the permissible limits due to axial, shear, flexural and torsional forces produced due to above forces. The slab and foundations were checked manually. The depth of slab which is is safe against the deflection and shear and the reinforcement provided are sufficient to counter the flexural forces as well. The foundation was checked against one way shear, two way shear and bending moments. The footings provided as per the drawing are safe and the reinforcement provided is sufficient. The structural safety would further depend upon the effectiveness of construction procedures as well as collapse and serviceability criteria followed during the construction phases. To make the Community building earthquake resistant, the Community building is designed following the Indian standard codes. Column design is verified so that Moment capacity of the columns remains higher than the adjacent beams. Therefore, the design philosophy adopted is Strong column and weak beam. Shear stirrups is sufficiently provided so that none of the elements are Vulnerable to shear failure and failure mode will be flexural, which is more ductile. Bearing capacity of the soil is assumed to be 100 KN/M2. Isolated footings provided as shown in the drawings are sufficient to bear the Community building loads to prevent any possible settlement. Durable M20 concrete has been used in the foundation which is in contact with the soil. M25 grade of concrete is used for Columns, Beams and slabs. Ductile detailing has been extensively adopted following NBC2020. 22 Structural Analysis and Design of Community Building 5. ANNEXES ANNEX- 1: LIST OF DESIGN SHEET 1. Earthquake Load Calculation as per NBC 105 2. Foundation Design Sheet ANNEX- 2: LIST OF STRUTURAL DRAWING 3. Typical beam column layout 4. Beam reinforcement details 5. Slab reinforcement details 6. Column reinforcement details 7. Footing reinforcement details 8. Beam column joint details 9. Staircase reinforcement details 10. Details of reinforcement for other structural and non structural components 23 Structural Analysis and Design of Community Building REFERENCES IS: 456 – 2000 Code of Practice for Plain and Reinforced Concrete IS: 875 (Parts 1-5) Code of practice for design loads (other than earthquake) for Community buildings and structures (second revision) Part 1 – Dead loads Part 2 – Imposed loads NBC 105: 2020 Seismic Design of Community buildings in Nepal IS: 1893 – 2016 Criteria for Earthquake Resistant Design of Structures IS: 13920 - 1993 Ductile Detailing of Reinforced Concrete Structures subjected to Seismic forces Code of Practice SP: 16 – 1980 Design Aids for Reinforced Concrete to IS: 456 – 1978 SP: 34 – 1987 Handbook on Concrete Reinforcement Detailing Jain, A.K. Reinforced Concrete, Limit State Design, fifth edition, Nem Chand and Bros, Rookie, 1999 Sinha, S. N. Reinforced Concrete Design, Second edition, Tata McGraw Hill Publishing Company Ltd, New Delhi, 1996 Reinforced Concrete Design, Second edition, Tata McGraw Hill Publishing Pillai,U.C. and 24
0
advertisement
Download
advertisement
Add this document to collection(s)
You can add this document to your study collection(s)
Sign in Available only to authorized usersAdd this document to saved
You can add this document to your saved list
Sign in Available only to authorized users