BOLT CONNECTION BEHAVIOR AND DESIGN OF A FOUR-ANGLE ASSEMBLED STEEL BUCKLING-RESTRAINED BRACE: THEORETICAL ANALYSIS

The bolts in an assembled buckling-restrained brace (ABRB) will combine the outer restraining angle steels together, and undertake tensile and shear forces while the ABRB deforms laterally. This paper presents a simplified design method for the bolt connections among angle steels, and the method is suitable for the situation that the ABRB only deforms in one direction. Firstly, the interaction between an inner core and outer restraining components is studied. Then, the reaction of the inner core to outer restraining components is decomposed into two states, namely one symmetric deformation state and one anti-symmetric deformation state. In the former state, the bolts prevent the outer angle steels from separating one another without a global lateral displacement; while in the latter state, the bolts make the angle steels bend cooperatively in the lateral and longitudinal directions. Relying on theoretical derivation, the equations to determine the bolt forces in the two states are obtained respectively, where the prying forces due primarily to local deformation of plate components of angle steel are taken into account. By the combination of the two states, the bolt forces are determined accurately. Finally, the influence of bolt distance on the amplitudes and distributions of bolt forces is introduced.