Abstract
This paper presents a performance-based plastic design (PBPD) methodology for the design of steel concentric braced frames. The design base shear is obtained based on energy–work balance equation using pre-selected target drift and yield mechanism. To achieve the intended yield mechanism and behavior, plastic design is applied to detail the frame members. For validity, three baseline frames (3, 6, 9-story) are designed according to AISC (Seismic Provisions for Structural Steel Buildings, American Institute of Steel Construction, Chicago, 2005) seismic provisions (baseline frames). Then, the frames are redesigned based on the PBPD method. These frames are subjected to extensive nonlinear dynamic time-history analyses. The results show that the PBPD frames meet all the intended performance objectives in terms of yield mechanisms and target drifts, whereas the baseline frames show very poor response due to premature brace fractures leading to unacceptably large drifts and instability.
Highlights
Steel concentrically braced frames are very efficient steel structures that are commonly used to resist forces due to wind or earthquakes
This paper presents a performance-based plastic design (PBPD) methodology for the design of steel concentric braced frames
The results show that the PBPD frames meet all the intended performance objectives in terms of yield mechanisms and target drifts, whereas the baseline frames show very poor response due to premature brace fractures leading to unacceptably large drifts and instability
Summary
Steel concentrically braced frames are very efficient steel structures that are commonly used to resist forces due to wind or earthquakes. Obtaining the design base shear for a pre-determined hazard level is a key factor in PBPD method It is calculated by equating the work needed to push the structure monotonically up to the target drift (no pushover analysis needed) to that required by an equivalent EP-SDOF system to achieve the same state. According to a study by Banihashemi et al (2015), by doing along the number of nonlinear dynamic and multi-modal pushover analyses on a lot of braced frames, it is possible to present a simple equation to estimate yield drift ratio as follows:. The strength distribution along the height of the structure should be according to the lateral force distribution obtained from nonlinear dynamic analysis (Chao et al 2007) This guarantees that the input energy will dissipate and will prevent the concentration damage in a story. It is noteworthy that the post-buckling strength of a brace is considered 0.5 Pcr for in-plane buckling
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