International Concrete Abstracts Portal

Editors: Kenneth J. Elwood, Jeff Dragovich and Insung Kim

This CD provides eleven papers summarizing new developments in the assessment and retrofit of concrete buildings, with a particular focus on the collapse prevention performance level. Many of the papers report on efforts by task groups of ACI 369, Committee for Seismic Repair and Rehabilitation. Several papers in this CD summarize research efforts related to the ACI 369 proposals under development, including modeling parameters and acceptance criteria for existing and jacketed columns, slender walls, and slab-column connections. Other papers report on retrofit case studies, a new assessment procedure for concrete buildings in Turkey, and practical numerical models for existing beam-column joints, in filled frames, and collapse simulation.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-297

Case studies on seismic assessment and rehabilitation of reinforced concrete buildings are discussed based on the projects in which Degenkolb Engineers has been involved in the past 5 years. Design, analysis and challenges are discussed to present applications of ASCE 31-03, Seismic Evaluation of Existing Buildings and ASCE 41-06, Seismic Rehabilitation of Existing Buildings.

There are many vulnerable reinforced concrete (RC) buildings located in earthquake-prone areas around the world. These buildings are characterized by the lack of seismic details and corresponding non-ductile behavior and significant potential of partial and global collapse. One of the current challenges of the earthquake engineering profession and research communities is the identification of such buildings and determination of effective and economical retrofit methods for response enhancement. Identification of these buildings is not a trivial task due to the various sources of non-ductile behavior and the large number of involved sources of uncertainty. Furthermore, accurate determination of collapse-prone buildings is important from an economical perspective. Unfortunately, there are not enough economical resources to retrofit all the non-ductile buildings that have the symptoms for collapse potential. In order to use the available monetary resources in an effective manner, these buildings should be accurately and reliably ranked to identify those that are most vulnerable to collapse. This paper intends to provide a contribution to the accurate determination of the most collapse vulnerable non-ductile RC buildings by discussing the methods from existing literature and exploring the research needs related to (a) gravity load failure modeling and (b) consideration of sources of uncertainty in an efficient manner.

A new law known as the "Urban Renewal Law" for risk mitigation was passed in May 2012 with the objective of reducing seismic risk associated with the existing building stock in Turkey. As stated in the law, new provisions are set forth to assess and to identify seismically vulnerable residential buildings as quickly as possible. The buildings that are classified as high risk are either demolished or strengthened. New buildings are constructed through the financing options provided by the government. In this study, first, the technical provisions of seismic risk assessment, based on linear elastic analysis, are briefly described with special emphasis on the deformation limits. Because of the inability of the linear elastic analysis to allow for redistribution, some flexibility is provided on how many vertical load bearing elements are allowed to exceed their performance limits. Afterwards, three case study buildings are analyzed by using the new provisions and ASCE/SEI 41-06 linear elastic procedure. Level and sources of conservatism in the two approaches are critically evaluated.

The assessment of the seismic vulnerability and collapse potential of masonry‐infilled RC frame buildings presents a significant challenge because of the complicated failure mechanisms they could exhibit and the number of factors that could affect their behavior. In general, there are two types of analysis methods that can be used to simulate the inelastic behavior of infilled frames. One is to use simplified frame models in which infill walls are represented by equivalent diagonal struts, and the other is to use refined finite element models that can capture the failure behavior of RC frames and infill walls in a detailed manner. However, both types of models have limitations in simulating structural response through collapse. While refined finite element models are not computationally efficient, simplified models are less accurate because of their inability to represent some failure mechanisms that could occur in an infilled frame. In this paper, possible failure mechanisms and causes of collapse of masonry‐infilled RC structures are discussed, and both simplified and refined finite element analysis methods that can be used to simulate the inelastic response of these structures and assess their vulnerability to collapse are presented with numerical examples. Additional research and development work needed to improve collapse simulations is discussed.