Research on Assembled Buckling-Restrained Braces Wrapped with Carbon Fiber and Basalt Fiber
|School||Harbin Institute of Technology|
|Keywords||buckling restrained brace carbon fiber basalt fiber hysteretic behavior multi-wave buckling|
Buckling-restrained brace (BRB) is a hysteretic energy dissipation device, whichhave been applied in more engineering structures. New BRBs with reasonable configu-ration and superior performance have been put forward. In this paper, we developed anew type of assembled buckling-restrained brace which wrapped by carbon fiber or ba-salt fiber, its properties have been researched by experiment and finite element analysis.Firstly, carbon fiber and basalt fiber were used as a new type of wrapping con-straint material, we can replace the damaged inner core element by cutting the fiber ma-terial to make the outer restrained components separated, so it is easy that inner core ofassembled BRB can be replaced after earthquake. Assembled BRB wrapped with fiberconstraint material is also a solution of poor corrosion resistance of outer steel tube. Inthis paper, the stability and strength of the assembled BRB were checked, including theoverall stability, local stability, overall buckling strength, checking local bucklingstrength and so on. By checking, we find the designed buckling-restrained brace of thispaper meet the stability and strength requirements.Secondly, based on the finite element analysis software ABAQUS, finite elementmodel of BRB was built with solid elements, and the finite element model was cali-brated with the existing experimental results. The parameters affecting the performanceof BRB were analyzed, including initial imperfection, coefficient of friction between theouter restrained element and inner core element, the gap between inner core element andouter restrained element, the constraint ratio of BRB, the width thickness ratio of innercore element, the elastic modulus of the fiber material. According to parameters analysis,we found that: the performance of BRB specimens were not affected obviously by theinitial imperfections of inner core. Friction coefficient is a major influence factor of thedifference between tension and compression bearing capacity of BRB, it is the maincause of the imbalance of the bearing capacity. Constraint ratio is a key factor for theoverall stability, and the gap between inner core element and outer restraint element isthe main cause to multi-wave buckling, both of which can directly affect the property ofhysteretic curve. Width thickness ratio has an effect on buckling mode, the smallerthickness ratio will allow the occurrence of biaxial buckling instability. Elastic modulusof the fiber material is an important parameter that affects the performance of BRB, thesmaller elastic modulus will increase the gap between inner core element and outer re-strained element, which deteriorate the hysteresis behavior of BRB. For this paper, anew type of assembled BRB with large constraints ratio, its hysteretic performance isgood, and the0.5mm gap between inner core element and outer constraint element is aappropriate value.Finally, eight assembled BRB specimens were tested by quasi-static test, and dif- ferent loading methods, different wrapping constraint materials and different slender-ness ratio of BRB were consider in this paper. The results show that multi-wave buck-ling occurred on inner core, which resulted in the deformation of wrapping constraintmaterial and increase the gap between the inner core element and outer restraint element.As a result, the hysteresis curves of BRB “jump" in the compression stage. When load-ing program was adopted as the increasing amplitude cyclic loading with the addition offatigue loading program, BRB specimens fractured in the middle of the inner core ele-ment; when the loading program was adopted as increasing amplitude cyclic loadingwithout the maximum amplitude limit, the final rupture of the BRB specimen occurredin the junction of yielding segment and non-yielding segment Assembled buckling-restrained braces wrapped with carbon fiber and basalt fiber were analyzed in finiteelement software ABAQUS, the results of finite element analysis are in good agreementwith the experimental results. Based on finite element analysis, stress distribution oncomponent reflects the member stress state, and accordingly the crack positions of innercores can determined, which are essentially coincident with test. The hysteresis curvesand skeleton curves of finite element analysis and experimental research coincide verywell.The constraint effect of two fiber cloth is good, which can be used to resist the lat-eral thrust exerted by inner core. Two parts of constraint segments of assembled BRBcan be connected and restrained with fiber cloth. Experimental results also show if theconstraint effects of fiber material are enhanced, such as adopting closer wrapping me-thod and increasing the layers of fiber cloth, the performance of the buckling-restrainedbrace will be improved.