scholarly journals Incorporation of Torsional & Higher-Mode Responses in Displacement-Based Seismic Design of Asymmetric RC Frame Buildings

2019 ◽  
Vol 9 (6) ◽  
pp. 1095
Author(s):  
Beka Abebe ◽  
Jong Lee
Keyword(s):  
Seismic Design ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Rc Frame ◽  
Performance Objective ◽  
Frame Buildings ◽  
Displacement Based ◽  
Rc Frame Buildings ◽  
Plan Configuration ◽  
Displacement Based Seismic Design

Direct displacement-based design (DDBD) is currently a widely used displacement-based seismic design method. DDBD accounts for the torsional response of reinforced concrete (RC) frame buildings by using semi-empirical equations formulated for wall-type buildings. Higher-mode responses are incorporated by using equations obtained from only a few parametric studies of regular planar frames. In this paper, there is an attempt to eliminate torsional responses by proportioning frames’ secant stiffnesses so that the centers of rigidity and supported mass (the mass on and above each story) coincide. Once the torsional rotations are significantly reduced and only translational motions are achieved, higher-mode responses are included using a technique developed by the authors in their recent paper. The efficiency of the proposed design procedure in fulfilling the intended performance objective is checked by two plan-asymmetric 20-story RC frame building cases. Case-I has the same-plan configuration while Case-II has a different-plan configuration along the height. Both cases have different bay widths in orthogonal directions. Verification of the case studies by nonlinear time history analysis (NTHA) has shown that the proposed method results in designs that satisfy the performance objective with reasonable accuracy without redesigning members. It is believed that a step forward is undertaken toward rendering design verification by NTHA less necessary, thereby saving computational resources and effort.

Effect of bidirectional excitation on seismic performance of regular RC frame buildings designed for modern codes

2021 ◽  
pp. 875529302110478
Author(s):  
Payal Gwalani ◽  
Yogendra Singh ◽  
Humberto Varum
Keyword(s):  
Seismic Performance ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Inelastic Behavior ◽  
Moment Frame ◽  
Frame Buildings ◽  
Bidirectional Excitation ◽  
Rc Frame Buildings ◽  
Nonlinear Time History ◽  
Hinge Model

The existing practice to estimate seismic performance of a regular building is to carry out nonlinear time history analysis using two-dimensional models subjected to unidirectional excitations, even though the multiple components of ground motion can affect the seismic response, significantly. During seismic shaking, columns are invariably subjected to bending in two orthogonal vertical planes, which leads to a complex interaction of axial force with the biaxial bending moments. This article compares the seismic performance of regular and symmetric RC moment frame buildings for unidirectional and bidirectional ground motions. The buildings are designed and detailed according to the Indian codes, which are at par with the other modern seismic codes. A fiber-hinge model, duly calibrated with the biaxial experimental results, is utilized to simulate the inelastic behavior of columns under bidirectional bending. A comparison of the estimated seismic collapse capacity is presented, illustrating the importance of considering the bidirectional effects. The results from fragility analysis indicate that the failure probabilities of buildings under the bidirectional excitation are significantly higher as compared to those obtained under the unidirectional excitation.

Introducing Dynamic Nonlinear Soil-Foundation-Structure Interaction Effects in Displacement-Based Seismic Design

2013 ◽  
Vol 29 (2) ◽  
pp. 475-496 ◽  
Author(s):  
Roberto Paolucci ◽  
Raffaele Figini ◽  
Lorenza Petrini
Keyword(s):  
Seismic Design ◽  
Damping Ratio ◽  
Time History ◽  
Nonlinear Behavior ◽  
Interaction Effects ◽  
Structure Interaction ◽  
Soil Foundation ◽  
Displacement Based ◽  
Dynamic Time ◽  
Displacement Based Seismic Design

An iterative linear-equivalent procedure to take into account nonlinear soil-structure interaction effects in the displacement-based seismic design is presented for the case of shallow foundations. The procedure is based on the use of empirical curves to evaluate the stiffness degradation and the increase of damping ratio as a function of foundation rotation. Iterations are performed to ensure that admissible values of foundation rotations are complied with, in addition to the standard checks on structural displacements and drifts. Some examples of application of the approach to the design of bridge piers are provided. Design results are checked by means of nonlinear dynamic time-history analyses performed by a macro-element-based numerical tool, assuming nonlinear behavior of both structure and soil-foundation system.

Research on Seismic Damage of Buildings in the Beichuan Earthquake

2014 ◽  
Vol 580-583 ◽  
pp. 1613-1617
Author(s):  
Fan Wang ◽  
Chen Ning
Keyword(s):  
Seismic Design ◽  
Plastic Hinge ◽  
Seismic Damage ◽  
Rc Frame ◽  
Analysis Software ◽  
Element Analysis ◽  
Frame Buildings ◽  
Rc Frame Buildings ◽  
Component Failures ◽  
Beichuan County

This paper mainly discusses seismic damage of RC frame buildings in Beichuan county based on the investigation on the spot. The building damage forms are classified and component failures are analyzed. Applying finite element analysis software, the performance of RC frame buildings under severe earthquake is simulated and the components plastic hinge development is researched. The analysis results are made a comparison with real damage of buildings in this paper and some suggestions are proposed to seismic design.

scholarly journals Rapid assessment of peak storey drift demands on reinforced concrete frame buildings

2019 ◽  
Vol 52 (3) ◽  
pp. 109-118
Author(s):  
Timothy J. Sullivan
Keyword(s):  
Reinforced Concrete ◽  
Linear Time ◽  
Rapid Assessment ◽  
Time History ◽  
Seismic Assessment ◽  
Rc Frame ◽  
Reinforced Concrete Frame ◽  
Concrete Frame ◽  
Frame Buildings ◽  
Rc Frame Buildings

The peak storey drift demands that an earthquake imposes on a building can be assessed through a detailed engineering seismic assessment or recorded if a building is instrumented. However, for the rapid seismic assessment of a large number of buildings, it is desirable to have a simplified means of estimating storey drift demands. Consequently, this paper proposes a simplified means of quickly estimating storey drift demands on reinforced concrete (RC) frame buildings. Expressions for peak storey drift demand as a function of ground motion intensity are developed by utilising concepts and simplifications available from displacement-based seismic design and assessment methods. The performance of the approach is gauged by comparing predicted storey drift demands with those obtained from rigorous non-linear time-history analyses for a number of case study buildings. The promising results suggest that the approach proposed will be useful for rapidly assessing the likelihood of damage to a range of drift-sensitive elements in modern RC frame buildings.

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