A Seismic Design Lateral Force Distribution Based on Inelastic State of Structures

2007 ◽  
Vol 23 (3) ◽  
pp. 547-569 ◽  
Author(s):  
Shih-Ho Chao ◽  
Subhash C. Goel ◽  
Soon-Sik Lee
Keyword(s):  
Seismic Design ◽  
Lateral Force ◽  
Elastic Response ◽  
Force Distribution ◽  
Relative Distribution ◽  
Inelastic Behavior ◽  
Seismic Demands ◽  
Framed Structures ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses

It is well recognized that structures designed by current codes undergo large inelastic deformations during major earthquakes. However, lateral force distributions given in the seismic design codes are typically based on results of elastic-response studies. In this paper, lateral force distributions used in the current seismic codes are reviewed and the results obtained from nonlinear dynamic analyses of a number of example structures are presented and discussed. It is concluded that code lateral force distributions do not represent the maximum force distributions that may be induced during nonlinear response, which may lead to inaccurate predictions of deformation and force demands, causing structures to behave in a rather unpredictable and undesirable manner. A new lateral force distribution based on study of inelastic behavior is developed by using relative distribution of maximum story shears of the example structures subjected to a wide variety of earthquake ground motions. The results show that the suggested lateral force distribution, especially for the types of framed structures investigated in this study, is more rational and gives a much better prediction of inelastic seismic demands at global as well as at element levels.

Seismic Design Aspects of Vertically Irregular Reinforced Concrete Buildings

2003 ◽  
Vol 19 (3) ◽  
pp. 455-477 ◽  
Author(s):  
Satrajit Das ◽  
James M. Nau
Keyword(s):  
Seismic Design ◽  
Lateral Force ◽  
Masonry Infills ◽  
Irregular Structures ◽  
Dynamic Analyses ◽  
Moment Resisting ◽  
Linear And Nonlinear ◽  
Definition Of ◽  
Design Earthquake ◽  
Nonlinear Dynamic Analyses

Seismic building codes such as the Uniform Building Code (UBC) do not allow the equivalent lateral force (ELF) procedure to be used for structures with vertical irregularities. The purpose of this study is to investigate the definition of irregular structures for different vertical irregularities: stiffness, strength, mass, and that due to the presence of nonstructural masonry infills. An ensemble of 78 buildings with various interstory stiffness, strength, and mass ratios is considered for a detailed parametric study. The lateral force-resisting systems (LFRS) considered are special moment-resisting frames (SMRF). These LFRS are designed based on the forces obtained from the ELF procedure. The results from linear and nonlinear dynamic analyses of these engineered buildings exhibit that most structures considered in this study performed well when subjected to the design earthquake. Hence, the restrictions on the applicability of the equivalent lateral force procedure are unnecessarily conservative for certain types of vertical irregularities considered.

Impact of Joint Modeling Approach on Performance Estimates of Older-Type RC Buildings

2017 ◽  
Vol 33 (3) ◽  
pp. 1101-1123 ◽  
Author(s):  
Beyhan Bayhan ◽  
Gökhan Özdemir ◽  
Polat Gülkan
Keyword(s):  
Joint Modeling ◽  
Joint Model ◽  
Analytical Models ◽  
Base Shear ◽  
Joint Rotation ◽  
Seismic Demands ◽  
Flexible Joint ◽  
Dynamic Analyses ◽  
Column Joint ◽  
Nonlinear Dynamic Analyses

The behavior of beam-column connections has usually been ignored in the modeling process due to its complexity and relatively recent awareness of its possible impact on response. This study presents the features of modeling unreinforced beam-column joints in estimating seismic demands. A representative RC frame is subjected to strong ground motions. Through nonlinear dynamic analyses, base shear, roof displacement, inter-story drift and joint rotation are noted. The dynamic analyses are performed comparatively through two analytical models with rigid and flexible joint assumptions. In the flexible joint model, shear deformation at the beam-column joint and bond-slip deformation at the beam-column interface are simulated through a previously verified analytical representation. Results indicate that introducing unreinforced beam-column joint behavior to the model may lead to almost two times larger seismic demands compared to those obtained from rigid connection assumption. Thus, the performance assessment of such buildings may conclude erroneously with underestimated seismic demands and damage levels when inelastic actions in the joints are ignored. However, in some cases, lower seismic demands can also be obtained for the flexible joint model.

scholarly journals Review of the Soft First Story Irregularity Condition of Buildings for Seismic Design

2010 ◽  
Vol 4 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Arturo Tena-Colunga
Keyword(s):  
Seismic Design ◽  
Nonlinear Dynamic ◽  
Substantial Reduction ◽  
Shear Stiffness ◽  
Building Codes ◽  
Lateral Shear ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses

The present study evaluates how the soft first story irregularity condition should be defined: (a) as a significant reduction of the lateral shear stiffness of all resisting frames within a given story, as established in the seismic provisions of Mexican building codes or, (b) as a substantial reduction of the lateral shear stiffness of one or more resisting frames within a given story, as proposed by the author. Both definitions are evaluated through nonlinear dynamic analyses of buildings systems with a suspected soft first story condition in order to discern which option is closer to define the soft fist story condition.

Robustness Based Structural Design: An Integrated Approach for Multi-Hazard Risk Mitigation

2011 ◽  
Vol 82 ◽  
pp. 770-777
Author(s):  
Dan Dubina ◽  
Florea Dinu
Keyword(s):  
Seismic Design ◽  
Structural Design ◽  
Risk Mitigation ◽  
Integrated Approach ◽  
Building Structures ◽  
Frame Buildings ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses ◽  
Story Building ◽  
Multistory Frame

Multi-story building structures can suffer local damage or even structural collapse in case of extreme natural or man-made hazards. While all buildings are at a certain risk, some attributes can reduce the risk by reducing the vulnerability. One such attribute is the use of structural systems which can ensure that, in case of abnormal loads or failure of some elements, the collapse is prevented and the risk to occupants is reduced. Mitigation of some specific hazard can also help to reduce the risk, eg. protective barriers against impact or stand-off distance against direct effects of blast. Past experience has shown that structures that are designed according to seismic design philosophy can survive to a multiplicity of hazards. The objective of the paper is the adaptation of seismic design methodology to robust design demands of multistory frame buildings prone to multi-hazard scenarios. The hazard is modeled by removal of critical members. Nonlinear dynamic analyses are carried out in order to evaluate their robustness.

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