Modeling Options for Transfer Structures to Assess the Behavior of Mix Use Building Structures in High Seismic Zone

Abstract

In modern world due to multi-functional requirements and architectural constraints, the transfer structures in low to moderate seismic zones are being used. However, the suitable modeling options and modification factors to account the true behavior of these types of structures need to be investigated in high seismic zones. In this study, a small prototype simply supported beam having shear span to depth ratio of less than 2 has been first designed manually using strut and tie approach and then modeled using different modeling techniques such as non-linear shell layered, area element, solid element, line element and strut and tie method (STM), available in commercial software’s. The cracking pattern, stress and strain distribution obtained from the different FEM modeling technique have been compared with experimental studies in the literature and on the basis of the results obtained, non-linear shell layered is selected as reference model. All other models are modified to approximately align with reference model in respect of mid span deflection. To account for the effect of cracking on stiffness, the modulus of elasticity and shear modulus of concrete is reduced by 20% in case of frame/line element. For shell/area element, moment of inertia is reduced by 35% of its gross value. For solid element, the modulus of elasticity and shear modulus of concrete is reduced by 40%. Whereas in case of STM, no stiffness modification factors are used. The findings of the small prototype are used in modeling transfer girders (TGs) in 11-storied building. The transfer girder (TG) is given at ground level and the building is founded on soil profile type-SD and located in seismic zone-04. The cracks pattern, stress and strain distribution, storey shear, overturning moments and deflections are worked out using gravity and seismic load combinations using equivalent static procedure. These parameters from each model have been compared with those obtained from the reference model in order to rank the modeling techniques. Based on this comparison, it is found that STM, thick shell, solid and line element are better modeling techniques in order of preference starting from STM. On the basis of the building performance in this study, it is confidently recommended the use of TGs in severe seismic zone-04. This research will help practicing engineers to select the best modeling technique for modeling of TG in mix use building structures.