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Numerical Analysis of Masonry-Infilled Reinforced Concrete Frames Subjected to Seismic Loads and Experimental Evaluation of Retrofit Techniques

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Abstract

 

Masonry-infilled reinforced concrete (RC) frames constitute a significant part of the building inventory in earthquake-prone regions around the world. The development of
accurate analysis tools and retrofit techniques is important for enhancing the seismic safety of older construction of this type. Most of the existing analytical approaches have
either adopted simplified models with limited predictive capabilities or been restricted to the monotonic loading regime. Additionally, many of the retrofit methods used in
practice have not been experimentally validated.
 
The present study aimed to establish and use refined computational tools for the reliable and robust analysis of masonry-infilled RC frames with and without retrofit, and
to experimentally validate recently developed retrofit schemes. Constitutive models have been developed to analyze infilled frames in an accurate and detailed manner.
An existing smeared-crack model has been enhanced to accurately describe diffuse cracking and crushing in concrete and masonry under cyclic loading.
Furthermore, a novel cohesive interface model has been formulated to describe strongly localized cracks in concrete members and the behavior of mortar joints. The model can
account for various aspects of the cyclic behavior of these materials, such as the cyclic normal unloading/reloading response, frictional sliding, and geometric dilatation and
irreversible crushing under large compressive stresses. A major challenge was the formulation of a robust stress update algorithm for the interface model. The models are
validated with experimental tests at the material and structural levels. The analyses demonstrate the capability of the models to accurately capture the response of infilled
frames.
 
Results of large-scale, shake-table tests on a masonry-infilled RC frame are presented. The purpose of the tests was to evaluate two retrofit methods for infills. One is
to use an overlay of Engineered Cementitious Composite material (ECC) and the other is to use Glass Fiber Reinforced Polymeric (GFRP) overlays. The material properties,
specimen configuration, input ground motions, and experimental observations are described in detail. Both retrofit techniques improved the performance of the specimen. A
series of nonlinear analyses has been conducted to provide further insight into the behavior of the retrofitted specimen.
 
Using the validated constitutive models, dynamic analyses have been conducted on infilled RC frames of three different configurations subjected to a collection of eight
ground motions that have been scaled to different intensity levels. The results of the analyses indicate that the addition of a relatively thin ECC overlay can significantly
improve the performance of an infilled non-ductile RC frame.

Cite this work

Researchers should cite this work as follows:

  • Ioannis Koutromanos (2011), "Numerical Analysis of Masonry-Infilled Reinforced Concrete Frames Subjected to Seismic Loads and Experimental Evaluation of Retrofit Techniques," http://nees.org/resources/3578.

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