Proportioning of self‐centering energy dissipative braces

Abstract

Self-centering energy dissipative (SCED) braces are designed to limit the maximum story drifts in buildings during earthquakes and to nearly eliminate residual drifts. The key properties of conventional braces (eg, strength, stiffness) can be determined with current seismic design procedures, but additional criteria are needed to select the hysteretic properties of SCED braces (eg, prestressing level, fuse activating deformation). Past investigations of the seismic performance of the SCED braced frames selected brace characteristics to match the hysteretic characteristics of buckling restrained braces (BRB). However, those characteristics may not be achieved because the performance of the SCED system is constrained by the elongation capacity of the post-tensioned tendons. To develop recommendations for proportioning SCED braces, the researchers conducted a parametric study on the properties of two typical SCED systems, using a ninestory steel braced frame office building. The seismic performances of the SCED systems were then compared with that of a BRB system including an analysis without property uncertainty and an analysis with uncertainty using Monte Carlo simulation. Based on the cost and seismic performances of SCED systems designed using various characteristics, recommendations are proposed for proportioning the SCED systems. Besides having much smaller residual drifts, the SCED systems had a smaller likelihood of exceeding a maximum story drift of 3% and less drift concentration compared with the BRB system, though they generated larger floor accelerations and forces in connections and adjacent members.The property uncertainty increased the residual drift of the SCED systems.

Experimental investigation of a low‐prestressed self‐centering energy dissipative brace

“…Five displacement histories were imposed on the prototype LP‐SCED specimen (Figure 10). To develop brace deformation histories based on a realistic building geometry, the test brace was assumed to be located in the first story of a nine‐story steel office building described in Xiao et al., 26 which originates from the SAC building 42 . The brace inclination to the horizontal direction was assumed to be 50 o .…”

“…To increase the resilience of buildings, various technologies have been developed with innovative features, such as self‐centering, 2–6 rocking, 7,8 , and replaceable components 9,10 . Among the self‐centering technologies, an attractive method is the introduction of a prestressing element into a conventional brace, such as a buckling‐restraint brace (BRB) or a friction brace, to provide a recentering capability 11–27 . Such self‐centering energy dissipative (SCED) braces are capable of controlling structural peak responses while nearly eliminating residual deformations, which significantly reduces structural repair costs and recovery time.…”

“…In addition, these systems require few changes to the architecture of the structure 13 . Therefore, SCED braces are an attractive candidate technology for the design of new and retrofitted resilient structures 26 …”

“…9,10 Among the self-centering technologies, an attractive method is the introduction of a prestressing element into a conventional brace, such as a buckling-restraint brace (BRB) or a friction brace, to provide a recentering capability. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Such self-centering energy dissipative (SCED) braces are capable of controlling structural peak responses while nearly eliminating residual deformations, which significantly reduces structural repair costs and recovery time. In addition, these systems require few changes to the architecture of the structure.…”

“…13 Therefore, SCED braces are an attractive candidate technology for the design of new and retrofitted resilient structures. 26 An SCED brace consists of a self-centering system and an energy dissipative system acting in parallel. 11 The selfcentering system consists of prestressing tension elements and axial-compression components.…”