Seismic Evaluation of Reinforced Concrete Columns and Collapse of Buildings

There are a large number of reinforced concrete (RC) buildings in seismically active areas of the world that are not designed and constructed in accordance with modern seismic design provisions. These buildings are vulnerable to severe damage or collapse due to their low lateral displacement capacity and rapid degradation of shear strength during strong ground motions. Typically, columns in such buildings lack adequate strength and ductility in reverse cyclic loading and experience brittle shear failure and loss of axial load carrying capacity. To assess vulnerability to earthquake damage and decide on the required level of retrofit, expected behavior of the columns in terms of strength and deformation capacity must be evaluated. This can be achieved by estimating the load-deformation response considering all potential failure mechanisms associated with axial, flexure and shear behavior. This study presents an analytical model for estimation of lateral load-displacement response of reinforced concrete columns. In the proposed model, flexural deformations are calculated through fiber section analysis employing cracked concrete behavior while shear behavior is modeled through Disturbed Stress Field Model (DSFM). The interaction between flexural and shear mechanisms is considered through axial strains and concrete compression softening. The proposed model also considers other critical aspects such as deformations due to reinforcement slip, buckling of compression bars, enhancement in strength and ductility of the concrete due to confinement, concrete tension stiffening and tension softening, and concrete compression softening effects. The comparison of predicted responses with experimental data indicates that proposed model is a suitable displacement-based evaluation approach that can be employed to accurately estimate load-displacement relationships and failure modes. During a seismic activity, local structural failure in the lower-story columns can initiate vertical or progressive collapse in the buildings with inadequate ductility if gravity loads cannot be transferred to undamaged columns. After one or more columns fail, an alternate load path is needed to transfer the loads carried by failed member (s) to other structural members. If adjoining elements cannot resist and redistribute the additional loads, a series of failures will occur until entire or substantial part of the structure collapses. In order to investigate redistribution of gravity loads resulting from column failure, a study is presented using a progressive collapse model and experimental data. During the experimental phase, an existing reinforced concrete building of regular structural configuration was tested by physically removing one first-story exterior column. The structural response of the test building was monitored by recording strains and displacements of selected frame members in the vicinity of removed columns. During the computational phase of the research, two- and three- dimensional models of the test building were generated in SAP-2000. Linear static and non-linear dynamic analyses were performed for both two- and three-dimensional building models. The experimental and predicted structural performances are compared and effectiveness of currently available analysis and design methodologies is discussed.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Civil Engineering

Grantor dc:publisher

The Ohio State University

Year dc:date

2012

Author dc:creator

• Lodhi, Muhammad S.

Contributors dc:contributor

• Sezen, Halil

• Civil Engineering
• Reinforced concrete
• column
• flexure
• shear
• progressive collapse

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1357318783

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1357318783