FEMA P695 Methodology Research Articles

The influence of gravity column continuity on the seismic performance of special steel moment frame structures

This paper investigates the influence of the stiffness and strength of gravity columns on the collapse performance of buildings that utilize steel special moment frames as the main seismic lateral load resisting system. The research centers on the development of a simple lumped column approach, where all the gravity columns are combined into one elastic, continuous, and pinned-base element. Once this approach was validated, 2-, 4- and 8-story buildings that were originally analyzed without the influence of gravity columns in the ATC 76-1 project were re-analyzed including gravity columns. The FEMA P-695 methodology was used to assess the collapse performance. The effect of having a different number of gravity columns and different column sections was modeled by varying the moment of inertia of the lumped gravity column. The results show that the gravity columns have a profound influence on the collapse performance of buildings, especially for taller structures. Moreover, it was found that the correlation between the results of the nonlinear static analyses and the nonlinear dynamic analysis, based on collapse evaluation, provides insight into the choice of an optimal section for the lumped column. This means, in turn, that the designer can determine the number and the size of gravity columns that are required to significantly improve the building's collapse performance.

Assessing the Collapse Probability of Base-Isolated Buildings considering Pounding to Moat Walls using the FEMA P695 Methodology

The collapse probability of two three story base-isolated buildings considering pounding to moat walls is examined using the methodology in FEMA P695. The superstructure models consist of a steel intermediate moment frame and a steel ordinary braced frame designed for the same seismic hazard. The behavior of these buildings under various ground motions is first examined, and it is found that the more rigid braced frame results in larger displacements demands on the isolation system, increasing the potential for impact. The collapse studies examine the effect of moat wall gap distance on the probability of collapse for these structures. These studies show that the flexibility and ductility of the moment frame model allow the superstructure to better absorb the impact forces. The braced frame superstructure tends to impact at lower shaking intensities and degrades in strength more rapidly due to the limited ductility that increases the risk of collapse.

Seismic Safety Evaluation of Reinforced Concrete Walls through FEMA P695 Methodology

AbstractQuantification of building system performance and response parameters such as response modification coefficient (R), system overstrength factor (Ω0), and deflection amplification factor (Cd...

Influence of the gravity framing system on the collapse performance of special steel moment frames

This paper investigates the influence of the gravity framing system on the seismic performance of special steel moment frames (SMFs). The buildings used in this study were taken from one of the examples that form part of the ATC-76-1 project, which used the FEMA P-695 methodology to assess the collapse probability of SMF systems. Two, four and eight story SMFs were analyzed with and without the gravity frame to quantify their collapse performance. Aspects of the gravity frame that were investigated include the contribution of stiffness and strength of beam to column connections, and the location of splices in the gravity columns. Moreover, this research investigates the potential for the development of inelastic deformations in the gravity columns, and the effect of such deformations on structural response. The results show that gravity connections and gravity column continuity profoundly affect the computed response and collapse probability. The inelastic behavior in gravity columns has a less important effect but should be included in the analysis.

A FEMA P695 Study for the Proposed Seismic Performance Factors for Cold-Formed Steel Special Bolted Moment Frames

The objective of this study was to verify the adequacy of the proposed Seismic Performance Factors for the newly developed Cold-Formed Steel Special Bolted Moment Frames in the AISI S110 Seismic Standard. The FEMA P695 methodology, Qualification of Building Seismic Performance Factors, was used for this purpose. A total of 13 archetype designs, representing two seismicity and two gravity load levels, were designed and analyzed. The computed results from all individual archetypes and four performance groups showed that the proposed seismic performance factors met the acceptance criteria and could provide a sufficient margin against collapse under the maximum considered earthquake.