Simplified Seismic Evaluation of Older Concrete Frames for Collapse Potential (Atc 78)


Abstract eng:
The life safety risk from seismic vulnerabilities of older concrete buildings, particularly frame buildings, is well known. Existing evaluation methods – which are based on component performance – are reasonable to assess damage potential, but are generally judged to be too conservative to predict collapse and significant risks to life safety. For several years, the Federal Emergency Management Agency (FEMA), through the Applied Technology Council (ATC), has sponsored the development of a simplified method to estimate collapse risk, which can be used to rank older concrete buildings for the purpose of identifying the truly dangerous ones. It is expected that such a method would be applied to a significant inventory of buildings in a screening phase of risk mitigation, so the level of engineering effort must be minimized. The method developed includes estimation of an approximate period and tabular approaches to estimate drift distributions at each story based on relative strengths and strength ratios of vertical and horizontal structural elements and presence of walls. For buildings where columns govern collapse, drift demand is compared with plastic rotation capacity for each column and a column rating related to the probability of loss of vertical load capacity is determined. The ratings of columns in the critical story are then statistically combined to estimate a probability of story collapse at that story. In contrast to conventional component-based methodologies, a probability of complete story collapse is thus deduced and the final collapse risk rating depends on the condition of the combination of components. For wall buildings where columns do not govern, other rules about redundancy and wall failure apply. The method has been developed targeted at U. S. building types and covers gravity frames with or without lateral force design, slab-column frames, frame buildings with walls, and bearing wall buildings. Structures are limited to 13 stories, but can have both horizontal and vertical irregularities. Trial evaluations have been carried out for frame structures to compare this methodology to other procedures for seismic assessment of these buildings and assess the difficulty of conducting the assessment.

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Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 1166.:
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