Commentary on FEMA P-807 for Retrofit of Wood-Frame Soft-Story Buildings

2014 ◽  
Vol 30 (4) ◽  
pp. 1359-1380 ◽  
Author(s):  
Bruce Maison ◽  
Brian McDonald ◽  
David McCormick ◽  
Marko Schotanus ◽  
Jonathan Buckalew
Keyword(s):  
Lateral Force ◽  
Seismic Intensity ◽  
Building Performance ◽  
Seismic Evaluation ◽  
Site Class ◽  
Soft Story ◽  
Safety Margins ◽  
Lateral Strength ◽  
Independent Review ◽  
Wood Frame

The FEMA P-807 guideline titled Seismic Evaluation and Retrofit of Multi-Unit Wood-Frame Buildings with Weak First Stories is a new approach for building retrofit. It goes beyond current building codes and standards by quantifying performance in probabilistic terms. The authors performed an independent review of P-807, and the resulting commentary herein covers five topics: (1) building lateral force-drift (backbone) curves, (2) building interstory drift limits, (3) lateral strength requirements, (4) collapse safety margins, and (5) site class effects. It was concluded that P-807 may be an efficient way for relative ranking and selection of retrofit designs—but it has questionable accuracy for predicting actual building performance (i.e., the probability that a particular seismic intensity will result in a meaningful state of damage for a specific building).

Experimental Seismic Collapse Study of a Full-Scale, 4-Story, Soft-Story, Wood-Frame Building

2015 ◽  
Vol 21 (2) ◽  
Author(s):  
Pouria Bahmani ◽  
John W. van de Lindt ◽  
Gary L. Mochizuki ◽  
Mikhail Gershfeld ◽  
Steven E. Pryor
Keyword(s):  
Full Scale ◽  
Soft Story ◽  
Frame Building ◽  
Seismic Collapse ◽  
Wood Frame

Cost-Benefit Analysis of Buildings Retrofitted Using GIB Systems

2016 ◽  
Vol 32 (2) ◽  
pp. 861-879 ◽  
Author(s):  
Hossein Agha Beigi ◽  
Constantin Christopoulos ◽  
Timothy J. Sullivan ◽  
Gian Michele Calvi
Keyword(s):  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Ground Level ◽  
Seismic Intensity ◽  
Benefit Analysis ◽  
Significant Cost ◽  
Soft Story ◽  
Masonry Infills ◽  
System A ◽  
Repair Costs

Recently, the gapped-inclined brace system (GIB) has been developed as an effective retrofitting solution for soft-story buildings. This paper presents a cost-benefit study of a building retrofitted using the GIB system. A six-story, reinforced concrete (RC) frame with an open story at the ground level and masonry infills on all other floors is studied. To investigate the effectiveness of alternate retrofit configurations, different scenarios of GIB systems are numerically analyzed, expected repair costs for various levels of seismic intensity are computed, and cost benefit values are compared to each other and to those obtained when the building is strengthened and stiffened at the ground floor using conventional methods. Results show that GIB retrofit solutions are likely to represent significant cost benefits compared to traditional retrofit solutions. The results also indicate that GIBs do not need to be positioned at all column locations of the soft story, which could be beneficial in reducing the overall retrofit cost and improving architectural functionality of the retrofitted structure.

SEISMIC ASSESSMENT OF CONTEMPORARY VERSUS OLD URBAN FRAME BUILDINGS

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
ABDELRAHMAN ASHRI ◽  
ANAS ISSA ◽  
Aman Mwafy
Keyword(s):  
Comparative Study ◽  
Lateral Force ◽  
Fragility Functions ◽  
Seismic Code ◽  
Earthquake Losses ◽  
Relative Safety ◽  
Safety Margins ◽  
Before And After ◽  
Benchmark Structures ◽  
The Comparative Study

This comparative study probabilistically assesses the relative safety margins of code-compliant and pre-seismic code RC buildings with different heights in a region of medium seismicity. Detailed structural design and fiber-based modeling of six benchmark structures, namely two code-compliant buildings and two pre-code structures before and after retrofit, are undertaken to develop fragility functions using several earthquake records representing the most critical seismic scenario in the study area. Several inelastic dynamic analyses are performed to assess the seismic response and derive a range of fragility functions for the six benchmark buildings. Compared with contemporary structures, the study highlights the vulnerability of pre-code buildings due to the insufficient stiffness, strength, and ductility provided by their lateral force resisting systems. A practical retrofit solution for pre-code structures is subsequently assessed using the methodology adopted for other modern and old buildings. The probabilistic assessment results confirmed the comparable seismic performance of the retrofitted and code-conforming buildings. The comparative study, which provided insights into the differences between code-compliant versus pre-seismic code buildings before and after retrofit, contributes to reducing earthquake losses and improving community seismic resilience in earthquake-prone regions.

Full-Scale Experimental Verification of Soft-Story-Only Retrofits of Wood-Frame Buildings using Hybrid Testing

2014 ◽  
Vol 19 (3) ◽  
pp. 410-430 ◽  
Author(s):  
Elaina Jennings ◽  
John W. van de Lindt ◽  
Ershad Ziaei ◽  
Pouria Bahmani ◽  
Sangki Park ◽  
...  
Keyword(s):  
Experimental Verification ◽  
Full Scale ◽  
Hybrid Testing ◽  
Soft Story ◽  
Frame Buildings ◽  
Wood Frame

Fragility Curves for Architectural Glass in Stick-Built Glazing Systems

2012 ◽  
Vol 28 (2) ◽  
pp. 639-665 ◽  
Author(s):  
William C. O'Brien ◽  
Ali M. Memari ◽  
Paul A. Kremer ◽  
Richard A. Behr
Keyword(s):  
Seismic Design ◽  
Fragility Curves ◽  
Building Performance ◽  
Seismic Evaluation ◽  
Glass Panel ◽  
Curtain Wall ◽  
Applied Technology ◽  
Damage States ◽  
Performance Based Seismic Design ◽  
System Configurations

Fragility functions are presented for 15 glazing system configurations in support of Applied Technology Council efforts to develop a performance-based seismic design approach for building performance assessment. The study includes seismic evaluation of curtain wall and storefront systems in terms of probability and the consequences of damage, including economic and life safety consequences. Defined damage states consist of gasket degradation, initial glass cracking and crushing, and glass fallout. Alternatives are offered to the provided prototype fragilities for configurations with differing glazing characteristics, which account for varying glass-to-frame clearance, aspect ratio, and glass panel dimensions. Issues related to applying laboratory-based fragility data to actual glazing systems in the field are addressed.

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