IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 09, 2015 | ISSN (online): 2321-0613 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS N. Mohan Reddy1 Dr. E. Arunakanthi2 1 PG Student 2Associate Professor 2 Department of Civil Engineering 1,2 JNTU College of Engineering, Anantapur, Andhra Pradesh, India Abstract— It is an attempt to investigate the effect of Irregular plan configuration for multistoried reinforced concrete building model.This paper mainly emphasizes on analysis of a multi-storey building (G+25) which is irregular both in plan and elevation. Modelling of 25 storeyed R.C.C. framed building is done on the ETABS v13.2.0 software for analysis. Post analyses of the structure such as Maximum Storey Displacement, Base Shear, Storey Drift, Maximum base reactions, Torsion and Over-turning moments are computed and then compared for all the analysed cases. ETABS is an engineering software product that caters to multi-story building analysis and design. ETABS stands for Extended Three dimensional Analysis of Building Systems. Basic or advanced systems under static or dynamic conditions may be evaluated using ETABS. Design of steel and concrete frames (with automated optimization), composite beams, composite columns, steel joists, and concrete and masonry shear walls is included, as is the capacity check for steel connections and base plates. ETABS provides an unequaled suite of tools for Structural Engineers designing buildings, whether they are working on one-story industrial structures or the tallest commercial high-rises. Key words: ETABS, G+25, R.C.C I. INTRODUCTION Earthquakes are the most undesirable and distressing of all natural calamities. From this, it is very difficult to save the structural properties and life. To overcome these concerns, we need to find the seismic performance of the built environment by developing various analytical procedures, which safeguard the structures to withstand during numerous minor earthquakes and also provide enough caution at the time of major earthquake. The behavior of a building during an earthquake depends on several factors such as stiffness, adequate lateral strength, ductility, configuration etc... During an earthquake, buildings with regular geometry and uniformly distributed mass and stiffness in plan as well as in elevation suffer much less damage compared to irregular configurations. But in present days, need and demand of the latest generation according to growing population has made the architects or engineers inescapable towards planning of irregular configurations. II. OBJECTIVE OF THE STUDY To obtain the Seismic performance of an irregular building located in various earthquake zones and in different types of soils of India. III. SCOPE OF THE STUDY The Present work is focused on the study of Seismic demands of an irregular R.C building for various seismic zones and different types of soils in India. The configuration involves plan irregularities such as diaphragm discontinuity, re-entrant corners and vertical irregularities such as geometrical irregularity, buildings resting on sloping ground. The performance was studied in terms of time period, base shear, lateral displacements, storey drifts and eccentricity in linear analysis using the code – IS1893 (Part 1):2002 . The entire modelling, analysis and design was carried out by using ETABS 13.2.0 version software. IV. IRREGULARITY The system of components of the building, which are able to resist the seismic forces, is known as lateral force resisting system (L.F.R.S). They are of different types. The most familiar forms of these systems used in a structure are special moment resisting frames (SMRF), shear walls and frame-shear wall dual systems. Generally, the damage in a structure initiates at a location where the weak planes are present in the building systems. These weaknesses activate further structural deteriorations, which leads to the structural collapse. These weaknesses often occur due to the presence of structural irregularities in stiffness, strength and mass in a building system. As per IS 1893:2002(part I), the structural irregularity can be broadly classified as, 1) Vertical irregularity and 2) Plan irregularity (a) Classification of Structural Irregularity Here, we just focus on Plan irregularity and study the structural behavior of the structure with irregular Plan configuration. V. MODELING OF THE BUILDING In this study, entire analysis for all the 3D models has been done using ETABS 13.2.0 version software. The results are tabulated in order to focus the parameters such as Lateral Displacement, Base shear, Storey drift, Torsion and Base reactions acting on the building. Here, the entire analysis process is carried out by linear analysis. All rights reserved by www.ijsrd.com 287 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS (IJSRD/Vol. 3/Issue 09/2015/072) In this study a Commercial building of 25 storey having different plan configurations at different levels (i.e. storeys 1-10, storeys 11-17, storeys 18-25) of the structure which is further analysed in different zones and different soil types (as per IS 1893 (Part I): 2002). Here, the structure in different zones and different soils is consider to study the effect of lateral deflection, storey drifts, bending moment, shear force and axial force caused due to lateral load (i.e. due to quake load). VI. BUILDING PARAMETERS The building has irregular plan configuration. A floor to floor height of 3.0m is assumed. The location of the building is assumed to be at different zones and different type of soils. An elevation and plan view of a typical structure is shown in fig. 2.1 (a) and 2.1 (b). Size of Structural Members: A. Column Size: 1) Rectangular Columns:  C 610mm x 915mm  C 700mm x 1100mm  C 800mm x 1250mm 2) Circular Columns:  C 1220mm dia  C 1300mm dia  C 1350mm dia (b) Building plan (Common to storeys 1 to 10 of all models) B. Beam Size:        B 460mm x 610mm B 460mm x 760mm B 540mm x 760mm B 610mm x 950mm B 610mm x 1200mm B 650mm x 950mm B 850mm x 1200mm C. Slab Thickness: 115 mm D. Grade of Concrete: M40 E. Grade of Steel: 1) For Beams:  Longitudinal Reinforcement: Fe500  Shear Reinforcement : Fe250 2) For Columns:  Longitudinal Reinforcement: Fe550  Shear Reinforcement : Fe415 (c) Building plan (Common to storeys 11 to 17 of all models) F. In this, all the Analyses has been carried out using Dynamic analysis procedure as per IS 1893-2002. VII. PLAN AND ELEVATION OF MODEL Plans of the model considered with 3 different plan configurations along the height of the building (i.e. storeys 1-10, storeys 11-17, storeys 18-25) is shown below. (d) Building plan (Common to storeys 18 to 25 of all models) All rights reserved by www.ijsrd.com 288 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS (IJSRD/Vol. 3/Issue 09/2015/072)    1.2(DL + LL – Wx) 1.2(DL + LL + Wy) 1.2(DL + LL – Wy) B. Dynamic Load Combination:     1.2(DL + LL + Sx) 1.2(DL + LL + Sy) 1.2(DL + Sx) 1.2(DL + Sy) X. RESULTS AND DISCUSSION In the present study, seismic response of high rise building (G+25) with irregular plan configuration at different levels using ETABS v13.2.0 under loading has been carried out. The objective of this study is to see the variation of loaddisplacement graph and check the maximum base shear and displacement of the. Following are the graphs drawn for the irregular G+25 storey building using ETABS. A. Torsion: (d) 3D view of G+25Storey Building VIII. MODEL DATA Story Load Case/Combo T (kN-m) Location Plinth 1.2(DL+LL+Ex) Max 198364.2 z2 s1 Plinth 1.2(DL+LL+Ex) Max 269775.3 z2 s2 The design data shall be as follows: Plinth 1.2(DL+LL+Ex) Max 331268.2 z2 s3 A. Live load : Plinth 1.2(DL+LL+Ex) Max 317382.7 z3 s1 Plinth 1.2(DL+LL+Ex) Max 431640.4 z3 s2 Plinth 1.2(DL+LL+Ex) Max 530029.1 z3 s3 Plinth 1.2(DL+LL+Ex) Max 476074 z4 s1 Plinth 1.2(DL+LL+Ex) Max 647460.7 z4 s2 Plinth 1.2(DL+LL+Ex) Max 795043.6 z4 s3 Plinth 1.2(DL+LL+Ex) Max 714111 z5 s1 Plinth 1.2(DL+LL+Ex) Max 971191 z5 s2 Plinth 1.2(DL+LL+Ex) Max 1192565 z5 s3   3kN/m2 at typical floor 1.5 kN/m2on terrace B. Wall load:    Exterior walls Interior walls Parapet wall : 12kN/m : 6kN/m : 6kN/m C. Wind Load: As per IS: 875(Part 3)-1987 D. Earthquake Load: As per IS-1893 (Part 1) – 2002 E. Type of Soil: Checked for all the 3 Types as per IS: 1893(Part 1) – 2002 F. Storey Height:   Typical floor: 3 m, Ground floor: 3m G. Floors: G.F. + 25 upper floors. IX. LOAD COMBINATIONS Here, we have two types of Load Combinations for the analysis of the structure. Namely, A. Static Load Combination:       1.5(DL+LL) 1.2(DL + LL + Ex) 1.2(DL + LL – Ex) 1.2(DL + LL + Ey) 1.2(DL + LL – Ey) 1.2(DL + LL + Wx) B. Base Shear: Base Shear values for different zones and different soils for the load case Ex 3 along X–axis and Ey 3 along Y-axis respectively. All rights reserved by www.ijsrd.com 289 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS (IJSRD/Vol. 3/Issue 09/2015/072) Storey Shear X Shear Y Location Story25 40.3 39.8 z2 s1 Plinth 40660.9449 41701.69 z2 s1 Story25 54.8 54 z2 s2 Plinth 55298.885 56714.3 z2 s2 Story25 67.2 66.3 z2 s3 Plinth 67903.778 69641.83 z2 s3 Story25 64.4 63.6 z3 s1 Plinth 65057.5118 66722.71 z3 s1 Story25 87.6 86.4 z3 s2 Plinth 88478.2161 90742.88 z3 s2 Story25 107.6 106.1 z3 s3 Plinth 108646.0447 111426.9 z3 s3 Story25 96.6 95.3 z4 s1 Plinth 97586.2677 100084.1 z4 s1 Story25 131.4 129.6 z4 s2 Plinth 132717.3241 136114.3 z4 s2 Story25 161.3 159.1 z4 s3 Plinth 162969.0671 167140.4 z4 s3 Story25 144.9 142.9 z5 s1 Plinth 146379.4016 150126.1 z5 s1 Story25 197 194.4 z5 s2 Plinth 199075.9862 204171.5 z5 s2 Story25 241.9 238.6 z5 s3 Plinth 244453.6006 250710.6 z5 s3 C. Storey Displacement: Maximum Storey displacement values for the load case 1.2(DL+LL+Ex)Max along X-direction and for 1.2(DL+LL+Ey) Max along Y-direction for different zones and different soils. Storey Max Disp X (mm) Max Disp Y (mm) Locatio n D. Max. Storey Drift: Maximum Storey Drift values for different zones and different soils for the load case 1.2(DL+LL+Ex) Max along X-direction and for 1.2(DL+LL+Ey) along Y-direction. Storey Drift X Drift Y Location Story19 0.000727 0.00074 z2 s1 Story19 0.000988 0.001 z2 s2 Story19 0.001213 0.00123 z2 s3 All rights reserved by www.ijsrd.com 290 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS (IJSRD/Vol. 3/Issue 09/2015/072) Story19 0.001162 0.00118 z3 s1 Plinth 149937.35 150124.4 z4 s1 Story19 0.00158 0.0016 z3 s2 Plinth 203915.58 204170.5 z4 s2 Story19 0.00194 0.00197 z3 s3 Plinth 250400.53 250709.5 z4 s3 Story19 0.001742 0.00177 z4 s1 Plinth 224908.24 225188.9 z5 s1 Story19 0.002369 0.0024 z4 s2 Plinth 305873.38 306255.7 z5 s2 Story19 0.002908 0.00295 z4 s3 Plinth 375600.79 376064.2 z5 s3 Story19 0.002613 0.00265 z5 s1 Story19 0.003553 0.0036 z5 s2 Story19 0.004362 0.00442 z5 s3 E. Max. Base Reactions: Max Base reactions values along X axes and Y axes for the load case 1.5(DL+Sy) Max for different Zones and different Soils. XI. COMPARISON OF DIFFERENT ZONES IN SAME TYPE OF SOIL (SAY TYPE III (SOFT) SOIL) A. Max. Storey Displacement: Max. storey displacement values along X-direction for Load case 1.2(DL+LL+Ex) Max Storey Vx (kN) Vy (kN) Location Story Zone 5 Zone 4 Zone 3 Zone 2 Plinth 62474.765 62552.71 z2 s1 Plinth 0 0 0 0 Plinth 84966.081 85072.29 z2 s2 Story1 12.3 8.2 5.5 3.4 Plinth 104334.05 104462.8 z2 s3 Story2 21.2 14.1 9.4 5.9 Plinth 99960.209 100084.9 z3 s1 Story3 30.4 20.3 13.5 8.4 Plinth 135945.73 136115.7 z3 s2 Story4 39.8 26.5 17.7 11 Plinth 166934.18 167140.1 z3 s3 Story5 49.2 32.8 21.9 13.7 All rights reserved by www.ijsrd.com 291 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS (IJSRD/Vol. 3/Issue 09/2015/072) Story6 58.6 39.1 26.1 16.3 Story9 0.000845 0.001352 0.002028 0.003042 Story7 68 45.4 30.2 18.9 Story10 0.000844 0.001351 0.002027 0.00304 Story8 77.4 51.6 34.4 21.5 Story11 0.00098 0.001568 0.002351 0.003526 Story9 86.6 57.8 38.5 24.1 Story12 0.001017 0.001627 0.00244 0.00366 Story10 95.9 63.9 42.6 26.6 Story13 0.000999 0.001597 0.002395 0.003592 Story11 103.5 69 46 28.8 Story14 0.000963 0.00154 0.00231 0.003464 Story12 114.6 76.4 50.9 31.8 Story15 0.00092 0.001471 0.002205 0.003307 Story13 125.5 83.7 55.8 34.9 Story16 0.000875 0.001399 0.002098 0.003146 Story14 136 90.7 60.5 37.8 Story17 0.000855 0.001368 0.002051 0.003075 Story15 146 97.4 64.9 40.6 Story18 0.00109 0.001744 0.002615 0.003721 Story16 155.6 103.7 69.2 43.2 Story19 0.001213 0.00194 0.002908 0.003962 Story17 164.9 110 73.3 45.8 Story20 0.001156 0.001848 0.002771 0.003856 Story18 176.8 117.9 78.6 49.1 Story21 0.001035 0.001655 0.002481 0.003691 Story19 190.1 126.7 84.5 52.8 Story22 0.000885 0.001416 0.002123 0.003183 Story20 202.7 135.2 90.1 56.4 Story23 0.00072 0.00115 0.001724 0.002586 Story21 214.1 142.7 95.2 59.5 Story24 0.000547 0.000874 0.00131 0.001964 Story22 223.8 149.2 99.5 62.2 Story25 0.000393 0.000628 0.000941 0.001411 Story23 231.6 154.4 103 64.4 Story24 237.6 158.4 105.6 66 Story25 241.9 161.3 107.6 67.2 C. Over-turning Moment: Over-turning Moment values of the structure along X-axis (Mx) for the Load case 1.2(DL+LL+Ex) Max B. Storey Drift: Storey Drifts of the structure along X-Direction for Load case 1.2(DL+LL+Ex) Max Story Zone 2 Zone 3 Zone 4 Zone 5 Plinth 0.00042 0.000671 0.001006 0.001509 Story1 0.000709 0.001134 0.001701 0.002551 Story2 0.000813 0.0013 0.00195 0.002925 Story3 0.000843 0.001348 0.002023 0.003034 Story4 0.000856 0.001369 0.002053 0.00308 Story5 0.000861 0.001378 0.002067 0.0031 Story6 0.000862 0.00138 0.00207 0.003104 Story7 0.000859 0.001375 0.002063 0.003094 Story8 0.000853 0.001365 0.002047 0.003071 Storey Zone 2 Zone 3 Zone 4 Zone 5 Plinth 4690852 7490315 11222932 16821857 Story1 4440140 7089176 10621224 15919297 Story2 4189902 6688538 10020054 15017327 Story3 3939928 6288325 9419520 14116312 Story4 3690552 5889066 8820418 13217445 Story5 3442236 5491504 8223861 12322397 Story6 3195577 5096594 7631282 11433315 Story7 2951306 4705502 7044431 10552825 Story8 2710282 4319608 6465377 9684029 Story9 2473502 3940503 5896505 8830508 Story10 2242091 3569989 5340521 7996318 All rights reserved by www.ijsrd.com 292 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS (IJSRD/Vol. 3/Issue 09/2015/072) Story11 2017310 3210083 4800448 7185994 Story16 45406.94 72651.1 108976.6 163465 Story12 1797373 2859653 4276026 6400585 Story17 41466.38 66346.21 99519.31 149279 Story13 1584685 2520821 3769002 5641274 Story18 37160.32 59456.51 89184.77 133777.2 Story14 1380505 2195602 3282397 4912591 Story19 33760.53 54016.85 81025.27 121537.9 Story15 1186193 1886171 2819474 4219430 Story20 29993.45 47989.51 71984.27 107976.4 Story16 1003207 1594862 2383736 3567046 Story21 25840.24 41344.38 62016.57 93024.85 Story17 833109.8 1324175 1978928 2961058 Story22 21282.07 34051.31 51076.96 76615.44 Story18 677561.2 1076766 1609038 2407448 Story23 16300.1 26080.16 39120.24 58680.35 Story19 538618.9 855502 1278013 1911779 Story24 10875.5 17400.8 26101.2 39151.8 Story20 412229.1 654322.4 977113.4 1461300 Story25 4990.818 7985.309 11977.96 17966.94 Story21 299748.1 475396.8 709595 1060892 Story22 202601.5 321006.1 478879 715688.3 Story23 122284.4 193542.8 288554 431070.8 Story24 60361.59 95510.31 142375.3 212672.7 Story25 18467.37 29523.55 44265.12 66377.49 XII. CONCLUSIONS From the results obtained by the analysis of Irregular G+25 model, following conclusions are drawn. D. Base Shear: Base shear values along X – axis for the Load case Ex 3 Storey Zone 2 Zone 3 Zone 4 Zone 5 Plinth 67903.78 108646 162969.1 244453.6 Story1 67891.66 108626.7 162940 244410 Story2 67819.83 108511.7 162767.6 244151.4 Story3 67658.22 108253.2 162379.7 243569.6 Story4 67370.92 107793.5 161690.2 242535.3 Story5 66922 107075.2 160612.8 240919.2 Story6 66275.58 106040.9 159061.4 238592.1 Story7 65395.72 104633.2 156949.7 235424.6 Story8 64246.52 102794.4 154191.7 231287.5 Story9 62792.07 100467.3 150701 226051.5 Story10 60996.46 97594.33 146391.5 219587.2 Story11 58905.73 94249.18 141373.8 212060.6 Story12 56942.27 91107.64 136661.5 204992.2 Story13 54637.93 87420.69 131131 196696.6 Story14 51965.44 83144.71 124717.1 187075.6 Story15 48897.53 78236.05 117354.1 176031.1 1) The plan configuration of the structure has major impact on the seismic response of the structure in terms of displacement, story drift, story shear etc... 2) The structural performance of the building model is better in zone II when compared to the other three zones. That too, in soil Type I (i.e., Hard Soil) it performs well. 3) It has been concluded that the Storey Overturning moment decreases with increase in the storey height. 4) Greater the height of the structure (building), higher will be the Storey Displacement. 5) The Drift values increases along with the storey height to some extent and then decreases. In this case, The Storey Drift value of the building is more at storey 19 in all the zones. With the help of graph, we can also conclude that, as the plan configuration changes, the drift curve also changes its fashion even in the same structure. 6) The Torsion and Base shear values of the building decreases with increase in height of the structure. 7) The above stated Structural properties (i.e., Displacement, Storey Drift, Base shear, Overturning Moment…) of the building differs more by about 72% in Zone V when compared to Zone II. 8) Whereas, the Axial shear force values are same in all the zones. All rights reserved by www.ijsrd.com 293 Seismic Analysis of a Multi-Storeyed Building with Irregular Plan Configuration Using ETABS (IJSRD/Vol. 3/Issue 09/2015/072) REFERENCES [1] S.K.Duggal (2013), “Earthquake Resistant Design of Structures”, Oxford University press. [2] Taranath B.S. (1988), “Structural Analysis and Design of Tall Buildings” McGraw-Hill Book Company. [3] P. Prashanth, S. Anshuman, R.K. Pandey, Herbert Arpan, “Comparison of design results of a Structure designed using STAAD and ETABS Software,” INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING, Volume 2, No 3, 2012 [4] Ravikumar C M, Babu Narayan K S, Sujith B V, Venkat Reddy D “Effect of Irregular Configurations on Seismic Vulnerability of RC Buildings” Architecture Research 2012, 2(3): 20-26 [5] Rucha S. Banginwar, M. R. Vyawahare, P. O. Modani “Effect of Plans Configurations on the Seismic Behaviour of the Structure By Response Spectrum Method” International Journal of Engineering Research and Applications (IJERA) Vol. 2, Issue 3, May-Jun 2012, pp.1439-1443. [6] Guleria, Abhay. "Structural Analysis of a MultiStoreyed Building Using ETABS for Different Plan Configurations." Vol. 3.Issue 5 (2014): 1481-484. International Journal of Engineering Research & Technology (IJERT). [7] Bureau of Indian Standards: IS: 1893(Part I): 2002, Criteria for Earthquake Resistant Design of Structures: Part 1 General provisions and Buildings (Fifth Revision), New Delhi, India. [8] Bureau of Indian Standards: IS: 875(Part 1)–1987, Dead Loads on Buildings and Structures (Second Revision), New Delhi, India. [9] Bureau of Indian Standards: IS: 875(Part 3)–1987, Wind Loads on Buildings and Structures (Second Revision), New Delhi, India. [10] ETABS 13.2.0, “Documentation and Training Manuals” All rights reserved by www.ijsrd.com 294