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Rahul LeslieSuivre

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30 Nov 2018•0 j'aime•5,001 vues

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For novice, please continue from "Modelling Building Frame with STAAD.Pro & ETABS" (http://www.slideshare.net/rahulleslie/modelling-building-frame-with-staadpro-etabs-rahul-leslie). This is a presentation covering almost all aspects of Seismic analysis & design of Multi-storied RC Structures using the Indian code IS:1893-2016 (New edition), with references to IS:13920-2015 (Code for ductile detailing) & IS:16700-2017 (code for design of tall buildings) where relevant; following for each aspect of the code, (1) The clause/formula (2) It's explanation/theory (3) How it is/can be implemented in the software packages of (i) STAAD.Pro and (ii) ETABS This is the latest edition of the earlier slides based on IS:1893-2002 which this one supersedes. This is Part-I of a two part series.

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- 1. 1 Seismic Analysis/Design of Multi-storied RC Buildings using STAAD.Pro & ETABS according to IS:1893-2016 Presented by . Rahul Leslie Deputy Director, Buildings Design, DRIQ, Kerala PWD Trivandrum, India Part - I
- 2. 2 Topics Covered: • Computer modelling and analysis using STAAD.Pro & ETABS for – Seismic Coefficient method as per IS:1893 (Part 1)-2016* – Response Spectrum method as per IS:1893(Part 1)-2016* (Covered in Part-II) • Miscellaneous points * With references to IS:13920-2015 & IS:16700-2017 where relevant Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 3. 3 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie Aspects of Computer Model: • Modelling is done using analysis packages like STAAD.Pro, STRAP, NISA Des. Studio, ETABS, GT STRUDL, RISA-3D, MIDAS-Gen, etc.
- 4. 4 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie Aspects of Computer Model: • Modelling is done using analysis packages like STAAD.Pro, STRAP, NISA Des. Studio, ETABS, GT STRUDL, RISA-3D, MIDAS-Gen, etc. • Model contains • Beams • Columns • Shear walls But not usually • Slabs, except • Flat slabs / Flat plates • Sloped RC Roofs (in ETABS) • Masonry wall infills • Stair slabs Foundation is represented by support points only
- 5. 5 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 6. 6 Model for ETABS: B+G+4=6 stories Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 7. 7 ETABS Model Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 8. 8 ETABS Model Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 9. 9 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 10. 10 Model for STAAD: G+4 = 5 stories Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 11. 11 STAAD Model Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 12. 12 STAAD Model Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 13. 13 Aspects of Computer Model (Cont…) • A model must ideally represent the complete three dimensional (3D) characteristics of the building, including – geometry – stiffness of various members – supports – load distribution – mass distribution • For models in the purview of IS:16700-2017*, rigid offsets at beam-column joint region should also be considered. (7.2 (a), IS:16700-2017) * Criteria for Structural Safety of Tall Concrete Buildings, applicable to RC buildings in the range of 50 to 250m height Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 14. 14 Beams and columns • Beams and columns are modelled by frame elements • Plinth beams should also be modelled as beams • Slabs are not usually modelled Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 15. 15 Beams and columns • Stiffness of Beams and columns to be reduced as: • Beams: Ieff = 0.35 Igross • Columns : Ieff = 0.7 Igross (6.4.3.1, IS:1893(Part 1)-2016) – New Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 16. 16 Beams and columns • Stiffness of Beams and columns to be reduced as: • Beams: Ieff = 0.35 Igross • Columns : Ieff = 0.7 Igross (6.4.3.1, IS:1893(Part 1)-2016) – New • However, nothing has been mentioned on stiffness reduced factors for • Shear walls • Flat slabs / Slabs Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 17. 17 Beams and columns • Alternatively, in IS:16700-2017*, the reduction factors are given as : a) For factored load cases – • Slabs: Ieff = 0.25 Igross • Beams : Ieff = 0.35 Igross • Columns : Ieff = 0.7 Igross • Walls : Ieff = 0.7 Igross b) For un-factored load cases – • Slabs: Ieff = 0.35 Igross • Beams : Ieff = 0.7 Igross • Columns : Ieff = 0.9 Igross • Walls : Ieff = 0.9 Igross (7.2 & Table 6, IS:16700-2017) *(for buildings coming under its purview) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 18. 18 Beams and columns • Using two sets of stiffness reduction factors (SRF), however, has its own issues: It will require analysis using two copies of the same Finite Element model files, One with SRF for factored loads, and The other with SRF for un-factored loads ...unless the Analysis software packages in future come up with facilities for optioning different SRF for different load combination cases – (load combinations to be covered later) In Response Spectrum method (to be covered later), the models for factored and un-factored loads end up having different (but very close) sets of mode shapes and mode frequencies, thus having each model analysed with different sets of modal parameters, though for the same building – I presume it is okay and generally accepted Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 19. 19 Assign section modifiers … ETABS: For Beams Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 20. 20 Assign section modifiers … ETABS: For Columns Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 21. 21 Assign cracked properties… STAAD: For Beams Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 22. 22 Assign cracked properties… STAAD: For Columns Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 23. 23 Supports: • The type of support to be provided is decided by considering the degree of fixity provided by the foundation. • Fixed Supports: – Raft foundation: Support to be provided at the column ends (located at top of the raft) – Pile cap for multiple piles: Support to be provided at the column ends (located at top of the pile cap) – Isolated footing: When it is founded on hard rock, the column end may be modelled as fixed (located at the top of the footing) – Single pile: Fixed support of the column is recommended at a depth of five to ten times the diameter of pile, depending upon the type of soil, from the top of pile cap. Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 24. 24 Supports (cont…): • Pinned supports: – Isolated footing: Support to be provided at the column ends, (located at the bottom of the foundation). • Spring supports: – Spring supports can be provided with spring constants , eg., as per ASCE/SEI 41 (2006) • In General – Engineering judgement must be exercised in modelling the support Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 25. 25 Slabs and Masonry walls • The weight of slabs are distributed, as 2-way load distribution, on the supporting beams. • The weight of masonry walls are applied as uniform load on the supporting beam Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 26. 26 Diaphragms • Since the slabs are not modelled by plate elements, the structural effect due to their in-plane stiffness (7.6.3 (b), IS:1893(Part 1)-2016) can be taken into account as Rigid Diaphragms by – using ‘Master/Slave’ option (STAAD.Pro) – assigning ‘Diaphragm’ action (ETABS , STAAD.Pro V8i SS4 onwards) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 27. 27 Diaphragms • This method is to be resorted to, only if the slab is stiff enough to act as a rigid diaphragm • This is to be ascertained as per criteria specified in 7.6.4, IS:1893(Part 1)-2016 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 28. 28 Diaphragms • Diaphragms have to be checked whether they can be considered rigid (7.6.4, IS:1893(Part 1)-2016) by – considering a floor independently, – modelling the floor with shell elements & meshing it, – applying a lateral load at its to be ‘Diaphragm centre’ – checking it’s deformation Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 29. 29 Diaphragms • A floor diaphragm is considered to be flexible, if it deforms such that the maximum lateral displacement measured from the chord of the deformed shape at any point of the diaphragm is more than 1 .2 times the average displacement of the entire diaphragm (7.6.4, IS:1893(Part 1)-2016). Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 30. 30 Diaphragms • This method is to be resorted to, only if the slab is stiff enough to act as a rigid diaphragm • This is to be ascertained as per criteria specified in 7.6.4, IS:1893(Part 1)-2016 • If the criteria is not met: • The storey loads are to be distributed at the column points of the floor, proportionate to the floor mass distribution 7.6.4, IS:1893(Part 1)-2016 • In tall buildings, the in-plane stiffness of the floor slab is to be modelled (using meshed shell elements) -- 7.3.3, IS:16700-2017 # # for buildings in its purview Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 31. 31 Assign diaphragms: select all slabs in a storey and … ETABS: Floor Diaphragm Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 32. 32 ETABS: Floor Diaphragm Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 33. 33 ETABS: Floor Diaphragm Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 34. 34 STAAD: Floor Diaphragm Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 35. 35 STAAD: Floor Diaphragm Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 36. 36 STAAD: Floor Diaphragm Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 37. Slabs and masonry walls (cont…) • Masonry infill walls have in-plane stiffness that can influence the behaviour of the building under lateral load. - Effects of infill walls are to be modelled, and then stiffness irregularity* to be examined for (7.9.1, IS:1893(Part 1)-2016) - Effects of infill walls are to be modelled, for analysis, if they contribute to lateral stiffness# (7.3.4, IS:16700-2017) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie • Masonry infills are modelled by equivalent diagonal struts with pinned ends (7.9.2.2, IS:1893(Part 1)- 2016) * as per Table 6, IS:1893(Part 1)-2016 # for buildings coming under it’s purview.
- 38. Slabs and masonry walls (cont…) • The properties of the diagonal struts are modelled according to the following: - Modulus of Elasticity as per 7.9.2.1, IS:1893(Part 1)-2016 - Where fm is the compressive strength of masonry (MPa), given by - Where fmo is the strength of mortar in the masonry, as per IS:1905-1987 and fb is the strength of bricks in the masonry, as per IS:1077-1992 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 39. Slabs and masonry walls (cont…) • The properties of the diagonal struts are modelled according to the following: - For the cross section of the strut, the terms used are: ‘thickness’ is the horizontal dimension of the diagonal strut cross section; and ‘width’ is the vertical dimension of cross section, measured perpendicular to the inclination of the strut. - For URM infill walls without any opening, width, Wds of equivalent diagonal strut is: - Where Lds is the (diagonal) length of the strut and - Where.. (continued on next page) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 40. Slabs and masonry walls (cont…) • The properties of the diagonal struts are modelled according to the following: - where (continued from previous page) - Em = modulus of elasticity of the materials of the infill - Ef = modulus of elasticity of the materials of the RC frame, - Ic = moment of inertia of the adjoining column, - t = thickness of the infill wall - θ = the angle of the diagonal strut with the horizontal; Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 41. Slabs and masonry walls (cont…) • The properties of the diagonal struts are modelled according to the following: - In case of infill walls with openings, no reduction in strut width is required (IS:1893-2016, Cl. 7.9.2.2(c)) - But it is known that openings reduce the stiffness of the diagonal strut, and the reduction is to be incorporated by suitably reducing the width of the strut. - The procedure given for calculating Wds is found to be developed by Mainstone & Weeks (1971) by utilising the formulae by Smith & Carter (1969) . - For reduction factors to account for openings in the masonry infills, many formulae have been developed. .. (continued on next page) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 42. Slabs and masonry walls (cont…) • The properties of the diagonal struts are modelled according to the following: - For example, Al-Chaar (2002) has developed a formula for the reduction factor due to openings. In his procedure, the reduction factor ρw the thickness of the strut to account for the effect of openings is - where Ao = area of the opening Ap = area of the infill panel (= l.h) - Subject to the condition that if Ao ≥ 60% of Ap, then ρw should be taken as zero. - ρw is the reduction factor for Wds, as Wdo = ρw .Wds - As of now (without any Amendment being published), the above reduction factor is not supported by the IS:1893-2016 code. Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 43. 43 Masonry walls (Table 6 (i), IS:1893(Part 1)-2016) : • The Structural Plan Density (SPD) should be estimated when unreinforced masonry (URM) infills are used. • When SPD of masonry infills exceeds 20%, the effect of URM infills shall be considered by explicitly modeling the same in structural analysis (by diagonal struts). Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 44. 44 Masonry walls (Table 6 (i), IS:1893(Part 1)-2016) : • The design forces for RC members shall be larger of that obtained from analysis of: • a) Bare frame, and • b) Frames with URM infills, using 3D modeling of the structure. • In buildings designed considering URM infills, the inter-storey drift shall be limited to 0.2 percent in the storey with stiffening and also in all storeys below. Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 45. 45 Shear walls • Structural shear walls and Shear core which are integrally connected to the frame and floor slabs, can be modelled by plate elements – ‘Surface elements’ (STAAD.Pro V8i and earlier) – Shell elements (STAAD.Pro Connect Edition and later) – ‘Wall element’ (ETABS) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 46. 46 Other considerations • Staircase slabs built integrally with the frame should be modelled (5.4, IS:13920-2015; 8.1.2 , IS:16700-2017)* • Provide sliding joints at the interconnection of the stairs with floors, so that they will not act as diagonal bracing (5.5, IS:4326-1993). If it is not providable, either of the following may be adopted instead: • Separated Staircases — staircase carried by a structure separated from the building (with a vertical separation joint between the two), in which one end of the staircase rests on a wall and the other end is carried by columns and beams. • Built-in Staircase — When stairs are built monolithically with floors, RC walls are provided at either side of the stairs, extending through the entire height of the stairs and to the building foundations. *(for buildings coming under its purview) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 47. 47 Other considerations • Staircase slabs built integrally with the frame should be modelled (5.4, IS:13920-2015; 8.1.2 , IS:16700-2017) • Buildings with any irregularities listed in IS:1893(Part 1), buildings with floating columns and set-back columns, a detailed Non-linear analysis is to be done (5.5, IS:13920- 2016). • As of now, the most practical approach to doing a Non-linear analysis is the Non-linear Static Procedure (NSP), better known as Pushover analysis Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 48. 48 Other considerations for tall buildings • The model should incorporate rigid end offsets at the joints (7.2 (a), IS:16700-2017) • ETABS does this automatically • With STAAD.Pro V8i, one has to do this manually Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 49. 49 Other considerations for tall buildings • The model should incorporate rigid end offsets at the joints (7.2 (a), IS:16700-2017) • P- Δ analysis to be done (7.2(d) & 7.3.9, IS:16700-2017) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 50. P- Δ analysis
- 51. 51 Other considerations for tall buildings • The model should incorporate rigid end offsets at the joints (7.2 (a), IS:16700-2017) • P- Δ (P-Delta) analysis to be done (7.2(d) & 7.3.9, IS:16700-2017) • STAAD.Pro & ETABS has conceptually different approaches to P- Δ, and correspondingly the settings/parameters to be provided also are different: • In STAAD.Pro, the gravity loads (DL & LL) and the seismic loads are to be combined using the REPEAT LOAD option instead of the LOAD COMBINATION option, and then PDELTA analysis is run. • In STAAD.Pro, only Seismic Coefficient Method can be included with P- Δ analysis, not the Response Spectrum Method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 52. STAAD: P-Delta Analysis
- 53. 53 Other considerations for tall buildings • The model should incorporate rigid end offsets at the joints (7.2 (a), IS:16700-2017) • P- Δ (P-Delta) analysis to be done (7.2(d) & 7.3.9, IS:16700-2017) • STAAD.Pro & ETABS has conceptually different approaches to P- Δ, and correspondingly the settings/parameters to be provided also are different: • In ETABS, a load combination is to be specified, which is considered for the P- Δ analysis • This load combination is the most critical one from among the codal seismic load combinations, but with the seismic part omitted. In IS:1893-2016 (with the most critical one in pink) these are 1.2 DL + 1.2 LL + 1.2 EL 1.2 DL + 1.2 LL 1.5 DL + 1.5 EL 1.5 DL 0.9 DL + 1.5 EL 0.9 DL Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 54. 54 ETABS Version 9.7 and earlier
- 55. 55 ETABS Version 2013 and later
- 56. 56 Other considerations for tall buildings • The model should incorporate rigid end offsets at the joints (7.2 (a), IS:16700-2017) • P- Δ analysis to be done (7.2(d) & 7.3.9, IS:16700-2017) • Construction Sequence analysis to be done for buildings taller than 150 m (7.3.13, IS:16700-2017) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 57. Construction Sequence analysis
- 58. Construction Sequence analysis
- 59. Construction Sequence analysis
- 60. Construction Sequence analysis
- 61. Construction Sequence analysis
- 62. Construction Sequence analysis
- 63. Construction Sequence Analysis Single Step Analysis Construction Sequence analysis
- 64. Construction Sequence analysis
- 65. Construction Sequence analysis
- 66. Construction Sequence analysis
- 67. Construction Sequence Analysis Single Step Analysis Construction Sequence analysis
- 68. 68 Other considerations for tall buildings • The model should incorporate rigid end offsets at the joints (7.2 (a), IS:16700-2017) • P- Δ analysis to be done (7.2(d) & 7.3.9, IS:16700-2017) • Construction Sequence analysis to be done for buildings taller than 150 m (7.3.13, IS:16700-2017) • Note: a case with floating columns has been demonstrated only because the effects of construction sequence are most prominent in such cases. Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 69. 69 Analysis as per IS:1893-2016 Seismic Coefficient Method (Static Analysis) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 70. 70 Static analysis: • The Design horizontal seismic coefficient Ah is calculated from (6.4.2, IS:1893 (Part 1)-2016) – Zone factor Z (Table 3 & Fig. 1, IS:1893 (Part 1)-2016) – Importance factor I (Table 8, IS:1893 (Part 1)-2016) – Response reduction factor R (Table 9, IS:1893 (Part 1)-2016) – Horizontal Acceleration coefficient Sa/g Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 71. 71 Static analysis: • Where the Horizontal acceleration Sa/g is determined from the Response spectrum curve (Fig.2A, IS:1893(Part 1)-2016) -- Modified Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 72. 72 Static analysis: • Where the Horizontal acceleration Sa/g is determined from the Response spectrum curve (Fig.2A, IS:1893(Part 1)-2016 – Modified) • Separate Response Spectrum curves are given for Seismic Coefficient Method and Response Spectrum Methods (Fig.2A & 2B, IS:1893(Part 1)-2016) – New • Also the both the Response Spectrum curves are horizontal straight lines after T = 4s. – Modified (Earlier, the code was silent on the portion of the curve for T > 4s) • But the above is insignificant in case of Fig.2A, IS:1893(Part 1)-2016 since the Seismic Coefficient Method is only applicable for regular structures having T < 0.4s (6.4.3, IS:1893(Part 1)-2016) - - New • Unless, of course, the method is to be used for Base Shear correction (to be covered later) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 73. 73 Static analysis (cont…): Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 74. 74 Static analysis (cont…): Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 75. 75 Static analysis (cont…): Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 76. 76 Static analysis: • The time period of the structure is determined using (7.6.2 (a) & 7.6.2 (c), IS:1893(Part 1)-2016) – RC frames without brick infills h = height of building in m – RC frames with brick infills d = base dimension in m (parallel to direction of earthquake) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 77. 77 Static analysis: • The time period of the structure is determined using (7.6.2 (a) & 7.6.2 (c), IS:1893(Part 1)-2016) – Buildings with RC walls (7.6.2 (b), IS:1893(Part 1)-2016) --New Aw = total effectie cross-sectional area of RC wall in the first storey in m2 Awi = cross-sectional area of RC wall i in the first storey in m2 Lwi = length of RC wall i in the first storey in m (both for walls parallel to direction of earthquake) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 78. 78 Static analysis: • The time period for irregular configurations is calculated for parameters determined as per the following figures (Fig.5 , IS:1893(Part 1)-2016) --New Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 79. 79 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie Static analysis (cont…): • Where the type of soils are – Type I (Rock or Hard soil): N > 30, among other descriptions – Type II (Medium soils): 10 ≤ N ≤ 30 for all soils N >15 for poorly graded, among other descriptions – Type III (Soft soils): N < 10 (Table 4, IS:1893(Part 1)-2016) • Where the N values are taken as the weighted average of N values of soil layers up to 30m below ground level (6.4.2.1, IS:1893(Part 1)-2016) -- New
- 80. 80 Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building 6.4.2, IS:1893(Part 1)-2016, description of (Sa/g) - (a)
- 81. 81 Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building 6.4.2, IS:1893(Part 1)-2016, description of (Sa/g) - (a)
- 82. 82 Static analysis: • Zone factor (Table 3, IS:1893(Part 1)-2016) – Z = 0.10 for Zone II – Z = 0.16 for Zone I II – Z = 0.24 for Zone IV – Z = 0.36 for Zone V Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 83. 83 Static analysis: • Importance factor (Table 8, IS:1893(Part 1)-2016) – I = 1.5 for special buildings (including community halls) – I = 1.2 for residential and commercial buildings with occupancy > 200 persons -- New – I = 1.0 for other buildings • Response reduction factor (Table 9, IS:1893(Part 1)-2016) – R = 3 for ordinary detailing (with ordinary detailed shear wall, if any) – R = 5 for ductile detailing (with ductile detailed shear wall, if any) ie., as per IS:13920-2016 – R = 4 for ductile detailing with ordinary detailed shear wall – R = 4 for ordinary detailing with ductile detailed shear wall – R = 3 for ordinary detailing with ordinary detailed shear wall – R = 5 for ductile detailing with ductile detailed shear wall Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 84. 84 Static analysis (cont…): • The base shear is determined by (7.2.1, IS:1893(Part 1)- 2016)... ... but subject to the condition that VB ≥ (VB)min (7.2.2, IS:1893(Part 1)-2016) – New ... Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 85. 85 Static analysis (cont…): • Where (VB)min is to be determined from ρ, given as the percentage of weight of the building (Table 7, IS:1893(Part 1)-2016)... (VB)min = ρW ... which is, in effect, as good as saying, for eg., for a structure in Zone III, Medium soil, I = 1.0 and R = 5, that T should be taken as not more than Tmin = 1.98s (by back calculating from ρ to Sa/g, and Sa/g to Tmin) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie Zone ρ II 0.7 III 1.1 IV 1.6 V 2.4
- 86. 86 Static analysis (cont…): • For tall buildings, ρ is determined from (Table 5, IS:16700-2018)... (VB)min = ρW ... for buildings of intermediate heights (ie., in the range of 120 to 200m), interpolation is to be used Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie Zone ρ for H≤120m ρ for H≥200m II 0.7 0.5 III 1.1 0.75 IV 1.6 1.25 V 2.4 1.75
- 87. 87 Static analysis (cont…): • The base shear is determined by (7.2.1, IS:1893(Part 1)- 2016)... ... but subject to the condition that VB ≥ (VB)min (7.2.2, IS:1893(Part 1)-2016) – New ... Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie • Design lateral force for each level is determined by (7.6.3, IS:1893(Part 1)-2016)... ... Where Wi is the seismic weight (to be covered) of the i’th storey at height hi
- 88. 88 A Simple Example A six storied structure Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 89. 89 Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building
- 90. 90 Lumped mass model Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building
- 91. 91 height 18 m Period 0.075x(18)0.75 = 0.6554 sec Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building (Assumed to be open structure)
- 92. 92 Levels W (kN) h (m) Wh2 SW*(Wh2/ SWh2) Qi (kN) 1 0 0 0 0 0 2 23.57 3 212.13 1.5541 0.0632 3 23.57 6 848.52 6.2163 0.2529 4 23.57 9 1909.17 13.9866 0.5691 5 23.57 12 3394.08 24.8651 1.0117 6 23.57 15 5303.25 38.8516 1.5807 7 23.57 18 7636.68 55.9464 2.2763 SW 141.42 (kN) 19303.83 141.42 kN 5.7539 kN Vb 5.7539 (kN) height 18 m Period 0.6554 sec Sa/g 1.5258 Ah 0.0407 Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building = (ZI)/(2R) x sa/g = (0.16*1)/(2*3) * 1.5258
- 93. 93 The forces are applied …and analysed Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building
- 94. 94 The forces are applied Presented by Rahul LeslieSeismic Analysis of Multi-storied RC Building
- 95. 95 Seismic Coeff. method ETABS: Define & Apply Seismic parameters: • Direction • T • Z, I, R • Soil Type STAAD: Define Seismic parameters: • Z, I, R • Structure Type or Tx & Tz • Soil Type • Damping ratio ξ Apply • Direction (X, Y,Z), factor Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 96. 96 ETABS: Seismic coeff. method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 97. 97 ETABS: Seismic coeff. method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 98. 98 ETABS: Seismic coeff. method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 99. 99 ETABS: Seismic coeff. method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 100. 100 STAAD: Seismic coeff. method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 101. 101 STAAD: Seismic coeff. method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 102. 102 STAAD: Seismic coeff. method Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 103. 103 Masses to be included: • For seismic analysis, the effective masses to be included for analysis are (7.4.1, IS:1893(Part 1)- 2016) : – Full dead load – 0.25 times Imposed Loads having intensity ≤ 3 kN/m2 – 0.5 times Imposed Loads having intensity > 3 kN/m2 – 0.2 times Snow Loads exceeding 1.5 kN/m2 -- New – Imposed Load on roof need not be considered (7.3.1, 7.3.2 , 7.3.5 & Table 10, IS:1893(Part 1)-2016) • The earlier edition clause that Live load reduction for upper floors (as per 3.2, IS:875(Part 2) - 1987) shall not be applied further for mass calculation in now missing – it was mentioned in 7.3.3, IS:1893 (Part 1) – 2002 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 104. 104 Add Seismic Masses EATBS • Select loads to combine STAAD • Add self wt., Joint loads, Member loads, Floor loads Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 105. 105 Define Mass Source:- ETABS: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 106. 106 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 107. 107 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 108. 108 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 109. 109 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 110. 110 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 111. 111 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 112. 112 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 113. 113 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 114. 114 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 115. 115 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie STAAD.Pro V8i SELECT 4
- 116. 116 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie STAAD.Pro V8i SELECT 4
- 117. 117 STAAD: Seismic masses Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie STAAD.Pro V8i SELECT 4
- 118. 118 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 119. 119 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 120. 120 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 121. 121 Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 122. 122 Results of Seismic Analysis – Bending Moment & Shear Force • Gravity Loads – Bending Moment • Gravity Loads – Shear Force • Seismic Loads – Bending Moment • Seismic Loads – Shear Force Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 123. 123 Load combinations: will be covered later Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 124. 124 ETABS: Run Analysis Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 125. 125 ETABS: Gravity Loads Bending Moment Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 126. 126 ETABS: Gravity Loads Shear Force Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 127. 127 ETABS: Seismic Force in Z direction Bending Moment Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 128. 128 ETABS: Seismic Force in Z direction Shear Force Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 129. 129STAAD: Run Analysis Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 130. 130 STAAD: Gravity Loads Bending Moment Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 131. 131 STAAD: Gravity Loads Shear Force Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 132. 132 STAAD: Seismic force in Z direction Bending Moment Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 133. 133 STAAD: Seismic force in Z direction Shear Force Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie
- 134. 134 Analysis as per IS:1893-2016 Response Spectrum Method (Dynamic Analysis) Seismic Analysis of Multi-storied RC Building Presented by Rahul Leslie Continued in Part-II with …
- 135. 135 Continue with Part-II rahul.leslie@gmail.com

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