Abstract
Buckling-restrained braces are commonly installed in building structures as concentric diagonal or chevron braces to protect the main construction from seismic actions. These elements have shown repeatedly their usefulness for reducing the seismic response, both from theoretical and experimental studies; and a number of practical applications have been reported. However, seismic records with near-fault effects possess special characteristics that might impair the performance of these devices, similarly as what occurs in base isolation; about energy issues, in such records (containing strong velocity pulses) the energy is delivered in a short time interval, thus being difficult to be absorbed. This work presents a numerical study regarding the performance of buckling-restrained braces under three types of seismic records: cortical far-field, subductive far-field and near-field (i.e. containing velocity pulses). The study is carried out on a symmetric 4-story steel moment-resisting unbraced frame that was tested at the E-defense laboratory, Japan; the dynamic response of such unbraced bare frame is numerically simulated, obtaining a satisfactory agreement. The same numerical model is used to describe the 2-D dynamic behavior of the steel frame equipped with buckling-restrained braces. The inputs are three series of ten ground motion records; each of these series belongs to one of the three aforementioned types. The average responses for each of the three types of inputs are compared; the obtained results show that the buckling-restrained braces are able to reduce the dynamic response of the frame and that no significant differences can be observed among the efficiency for far-fault and near- fault records.
Highlights
Energy dissipators are intended for seismic protection of buildings and other constructions
Results from Figs. (6 and 7) show that, for all the considered types of records, the buckling-restrained braces are able to reduce the dynamic response in terms of relative displacement and interstory drift; no relevant differences can be observed, neither among cortical, subductive and near-fault records, nor between BRB1 and BRB2, nor between Design Response Spectrum” (DRS) and MCE levels
This paper presents a numerical study on the seismic efficiency of buckling-restrained braces for reducing the seismic response of short-height frame buildings under several types of inputs
Summary
Energy dissipators are intended for seismic protection of buildings and other constructions They take up most of the input energy; as a result, the main structure remains protected, even for severe ground motions [1, 2]. Buckling-restrained braces are one of the most common hysteretic dissipators, having been mostly considered for buildings [4, 5]. These elements have slender steel core bracing rods; typically are used either as diagonal or chevron concentric braces Figs. Tensile and compressive axial stresses exceed the steel yielding point; core buckling is prevented by encircling it with a squattest encasing Undesirable shear stress transfer between steel core and casing is prevented by a sliding interface
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