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

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 16,800kN 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.