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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP297

Date: 

March 6, 2014

Publication:

Symposium Papers

Volume:

297

Abstract:

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


Document: 

SP297-08

Date: 

March 6, 2014

Author(s):

M. Baradaran Shoraka, K.J. Elwood, T.Y. Yang, and A.B. Liel

Publication:

Symposium Papers

Volume:

297

Abstract:

Probability of collapse is currently used to set targets for system performance and response measures of new buildings. This study compares the probability of collapse for new, retrofitted and existing concrete buildings. Retrofitting plays an important role in reducing seismic risk from older concrete buildings. In order to decide on the most appropriate and economical retrofit strategy for an existing structure, it is necessary to assess the risk of collapse of each rehabilitation measure. At present, it is frequently assumed that retrofitting a non-ductile concrete building will enhance the seismic performance such that it can reach the same performance level as a ductile building designed based on current seismic codes. However, based on the evaluation of the concrete frames presented in this paper, typical retrofit schemes (such as: adding an additional lateral force restraint system; increasing ductility of existing concrete columns; and weakening the existing beams) cannot achieve the same performance as modern code-conforming structures. The study finds that retrofitting schemes where the columns or beams are modified such that the frame satisfies the collapse prevention level of ASCE 41-13 have the least beneficial effect regarding seismic collapse safety; and conversely, adding a shear wall will significantly improve the seismic performance in terms of the probability of collapse.


Document: 

SP297-09

Date: 

March 6, 2014

Author(s):

Insung Kim and Garrett Hagen

Publication:

Symposium Papers

Volume:

297

Abstract:

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.


Document: 

SP297-07

Date: 

March 6, 2014

Author(s):

P. Benson Shing and Andreas Stavridis

Publication:

Symposium Papers

Volume:

297

Abstract:

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.


Document: 

SP297-01

Date: 

March 6, 2014

Author(s):

W. M. Ghannoum and A.B. Matamoros

Publication:

Symposium Papers

Volume:

297

Abstract:

A database of 490 pseudo-static tests of reinforced concrete columns subjected to load reversals was used to evaluate nonlinear modeling parameters that define the lateral force versus lateral deformation envelope relation of columns under seismic excitations. Based on the modeling parameters, criteria that identify acceptable deformation levels at various performance objectives are proposed. The effects of bi-directional loading and number-of-cycles of the displacement history on the drift ratio at axial failure are discussed, and recommendations are given to account for such effects. Modeling parameters and acceptance criteria are provided in a format that is consistent with provisions of the ASCE 41-06 Standard entitled “Seismic Rehabilitation of Existing Structures”.


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