Evaluation of cyclic performance of a novel bracing system equipped with a circular energy dissipater

Abstract

In line with efforts made by researchers aiming to enhance ductility of the bracing systems, use of steel ring as an energy absorbing element with different pros and cons, has been evaluated in recent years. Hence, to alleviate drawbacks of this system, a novel bracing system including a circular yielding damper has been experimentally and numerically investigated in this paper. The main motivation to develop this system is to improve ductility, energy absorption and overcome some of the weaknesses of conventional systems. Moreover, this novel load-carrying system has a diamond-scheme in which there is a circular yielding damper and the damper and brace elements act indirectly with each other. To this end, an experimental specimen of the diamond-scheme bracing system with scale of 12 and pinned connections was built. Notably, the angle between the brace elements is taken equal to 15.6°. In the next step, the specimen was subjected to ATC-24 loading protocol and the experimental results were compared with the numerical outputs obtained from simulations using ABAQUS Software indicating a great agreement between them. Then, two types of diamond-scheme bracing including steel ring with various thicknesses as well as a link element with high rigidity substituted for the steel ring, were modelled in real-scale and placed inside a frame with two bays and one storey. Lastly, their performance was compared with that of the conventional bracing systems as well as the other similar previous studies. The results derived from experimental tests revealed that firstly, at the end of the testing process, all main brace elements remained elastic and only the steel ring has been damaged indicating the fact that the proposed system can properly distribute the induced loads in all components of the system (the steel ring works in shear and flexure and the brace elements are subjected to axial forces). Moreover, using a ring with load-carrying capacity of 3ton, a total capacity of nearly 27ton was achieved. It is noteworthy that the value of angle between brace elements plays a direct role in total capacity of the system. Numerical developments illustrated that as per increase in thickness of the ring (increase in the ring’s capacity), the capacity could raise up to 75% of that of a diagonal bracing system. Moreover, it was observed that energy absorption capacity of the diamond-scheme bracing system including the ring, is about 45% greater than that of the equivalent concentric brace. However, use of this system without presence of the ring (the case in which a link is present), despite having a behavior similar to that of the concentrically-braced frames (CBF), still suffers from drawbacks of the conventional braces as its braces act as the sacrificial element and incur buckling.