Seismic Behavior Evaluation of Semi-Rigid Steel Frames with Knee Bracing by Modal Pushover Analysis (MPA)

Nowadays use of a new structural bracing system called 'Knee Bracing System' have taken the specialists attention too much. On the other hand nonlinear static analysis procedures in estimate structures performance in earthquake time have taken attention too much. One of these procedure is modal pushover analysis (MPA) procedure. The accuracy of MPA procedure for simple steel moment resisting frame has been verified and considered in Chintanapakdee and Chopra-s article in 2003. Since the accuracy of MPA procedure has not verified for semi-rigid steel frames with knee bracing, we are going to get through with this matter in this study. For this purpose, the selected structures are four frames with different heights, 5 to 20 stories, will be designed according to AISC criteria. Then MPA procedure is used for the same frames with different rigidity percentiles of connections. The results of seismic responses are compared with dynamic nonlinear response history analysis as exact procedure and accuracy of MPA procedure is evaluated. It seems that MPA procedure accuracy will come down by reduction of the rigidity percentiles of semi-rigid connections.

Authors:

• Farzan Namvari
• Panam Zarfam

Keywords:

• Knee Bracing
• Modal Pushover Analysis
• SeismicBehavior
• Semi-Rigid Connections.

References:

[1] C. W. Roeder, E. P. Popov, "Eccentrically braced steel frames for
earthquakes," journal of structural division, AICE 1978;104(ST3), PP.
391-412
[2] A. Ochoa, "Disposable Knee Bracing: Improvement in
Seismic Design of
Steel Frames,"Journal of Structural Engineering,
ASCE;112(7), pp. 1544-1552.
[3] F. Namvari, Thesis for master-s degree, Dezful (Iran), Islamic azad
university, Dezful branch, 2010.
[4] AISC, "Load and Resistance Factor Design Specification for Structural
Steel Buildings," American Institute of Steel Construction, Chicago,
1994.
[5] M. Mofid and P. Khosravi," Non-Linear Analysis of Disposable Knee
Bracing," Computers & Structures, no. 75, pp. 65-72, 2000.