Seismic design and test of gusset connections for buckling‐restrained braced frames

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SUMMARY The debonding mechanism has a significant effect on the performance of a buckling‐restrained brace (BRB). In this paper, a method for estimating the compression strength adjustment factor for any given BRB core strain is presented. Experimental investigations were conducted on four BRBs to examine the efficiency of four different debonding materials in reducing the difference between the cyclic peak compression and tension. Test results indicate that chloroprene rubber is very easy to install and very effective in minimizing the difference between the compressive and tensile capacities. The excellent performance of 13 full‐scale welded end‐slot BRBs (WES‐BRBs) is illustrated through experiments. Cyclic loading test results of a 12.5‐m long jumbo WES‐BRB reveal that its peak compressive strength exceeds 16,800 kN and its maximum core strain reaches 0.035. All WES‐BRBs show satisfactory performance with a very stable hysteresis response, modest peak compressive to tensile strength ratio, and very predictable axial stiffness. These specimens sustain a cumulative plastic deformation of greater than 400 times the yield deformation. The hysteresis responses can be satisfactorily predicted by using a two‐surface plasticity analytical model. Advantages of the welded end‐slot connections are also presented through a discussion on the effects of the BRB yield region length ratio on the effective stiffness, the yield story drift, and the core strain level. Copyright © 2014 John Wiley & Sons, Ltd.

Section: Introductionmentioning

confidence: 99%

Welded end‐slot connection and debonding layers for buckling‐restrained braces

Tsai

Wei³

et al. 2014

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“…Thus, the maximum column shear force ( V col ) was used to compute the equivalent strut axial force. Force equilibrium and compatibility conditions of the equivalent strut and the column allow the calculation of the horizontal ( S ) and vertical ( N ) force component of the equivalent strut axial force as follows :

S = N = \frac{d_{c} l_{f i x} V_{c o l} ((), 0.3 L_{c o l} - 0.18 l_{f i x})}{4 I_{c} true/ t_{g} + d_{c} l_{f i x} ((), 0.3 d_{c} + 0.18 l_{f i x})}

where d c and I c are the column width and the moment of inertia, respectively. L col is the clear story height.…”

Section: Experimental Programmentioning

confidence: 99%

Retrofit of reinforced concrete frames with buckling‐restrained braces

Mahrenholtz

Lin

et al. 2014

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SUMMARYDamage to buildings observed in recent earthquakes suggests that many old reinforced concrete structures may be vulnerable to the effects of severe earthquakes. One suitable seismic retrofit solution is the installation of steel braces to increase the strength and ductility of a building. Steel bracings have some compelling advantages such as their comparatively low weight, their suitability for prefabrication, and the possibility of openings for utilities, access, and light. The braces are typically connected to steel frames that are fixed to the concrete structure using post-installed concrete anchors along the perimeter. However, these framed steel braces are not without some disadvantages such as heavier steel usage and greater difficulties during the installation. Therefore, braces without steel frames appear to be an attractive alternative. In this study, braces were connected to gussets furnished with anchor brackets, which were fixed by means of a few post-installed concrete anchors. The clear structural system and the increased utilization of the anchors allowed the anchorage to be designed precisely and economically. The use of buckling-restrained braces (BRBs) provides additional benefits in comparison with conventional braces. BRBs improve the energy dissipation efficiency and allow the limitation of the brace force to be taken up by the highly stressed anchorage. Cyclic loading tests were conducted to investigate the seismic performance of BRBs connected with post-installed anchors used to retrofit reinforced concrete frames. The tests showed that the proposed design method is feasible and increases strength as well as ductility to an adequate seismic performance level.

“…Takeuchi et al [1] summarized the most recent literature related to connection failure, which includes research highlights [2][3][4][5][6][7][8][9][10][11][12][13][14] and the steel structure seismic provisions [15,16]. Additionally, Lin et al [17] investigated the connection stress distribution by means of experimental testing and FEM analysis, proposing several design recommendations. Zhao et al [18] proposed a practical design method to ensure the global stability of the BRBs based on a moment amplification factor in order to simplify the effect of connections.…”

Section: Introductionmentioning

confidence: 99%

Out‐of‐plane stability assessment of buckling‐restrained braces including connections with chevron configuration

Takeuchi

Matsui

Mihara

2016

SUMMARYOne of the key limit states of buckling-restrained braces (BRBs) is global flexural buckling including the effects of the connections. The authors have previously proposed a unified explicit equation set for controlling the out-of-plane stability of BRBs based on bending-moment transfer capacity at the restrainer ends. The proposed equation set is capable of estimating BRB stability for various connection stiffnesses, including initial out-of-plane drift effects. However, it is only valid for symmetrical end conditions, limiting application to the single diagonal configuration. In the chevron configuration, the out-of-plane stiffness in the two ends differs because of the rotation of the attached beam. In this study, the equation set is extended to BRBs with asymmetric end conditions, such as the chevron configuration. Cyclic loading tests of the chevron configuration with initial out-of-plane drifts are conducted, and the results are compared with the proposed equation set, which is formulated as a function of the normalized stiffness of the attached beam.