Seismic Response of an Instrumented 13-Story Steel Frame Building Damaged in the 1994 Northridge Earthquake

Abstract

This paper summarizes a case study of a 13-story welded steel moment frame (WSMF) building affected by the 1994 Northridge earthquake. The building, which was instrumented, sustained extensive damage to its welded connections. Ground motion records from the basement and response records from the sixth and twelfth floors were available. Damage data was collected with post-earthquake inspection and testing of each joint. The primary objective of the study was to compare modeled behavior with recorded response in order to assess the value of present analytical tools and modeling techniques for predicting the distribution and severity of connection failures. Calculated elastic time-history displacements matched well with recorded displacements in the E-W direction, less so in the heavily-damaged N-S direction where the elastic model was unable to simulate fractured moment connections. In the elastic analyses, joint demand was represented by beam demand-capacity ratios (DCRs). The highest beam DCRs were concentrated between the second and seventh floors; these locations correlated strongly with observed damage. Inelastic time-history analyses improved the displacement match in the N-S direction. They also indicated that panel zone yielding would have controlled the intended ductile response. This study suggests that for a regular structure, current modeling and analysis tools for both elastic and inelastic analysis, while unable to simulate premature brittle fractures, can be useful for predicting in a probabilistic way the intensity and distribution of damage expected in moderate seismic events.

Influence of the link overstrength factor on the seismic behaviour of eccentrically braced frames

“…Mass and stiffness coefficients have been derived so as to have an equivalent viscous damping factor equal to 0.05 in correspondence to the first and third mode of vibration. This value is also suggested by other researchers and studies [27], although some lower values may seem to be more proper, particularly with reference to the fundamental mode of vibration of high-rise buildings [28][29][30][31]. In accordance with Ricles and Popov [32], no stiffness proportional damping has been considered for the shear elements of links.…”

A design procedure for tied braced frames

“…[25,26]). Simplified design displacement spectra ( Figure 5) are derived on the basis of the response of SDOF bilinear systems to the accelerograms that are selected for the inelastic dynamic analyses of the TBFs.…”

Fragility Assessment of Pre-Northridge Steel Moment Frames Using Finite-Length Plastic Hinge Elements and Concentrated Plasticity Fracture Elements

“…Several numerical studies investigated the SAC Project Los Angeles buildings [Luco and Cornell (2000); Lee and Foutch (2002); Wang and Wen (2000); Xu and Ellingwood (2011)] using models implemented in DRAIN-2DX and IDASS [Prakash, Powell and Campbell (1993); Kunnath (1995); Uang, Yu, Sadre et al (1995)]. Several authors [Luco and Cornell (2000); Shi and Foutch (1997); Prakash, Powell and Campbell (1993)] stated that, although considering failure of connections consistently increases displacements, the magnitude of the increase varies among different building typologies.…”