Cyclic response of hollow and concrete-filled circular hollow section braces

Abstract

The behaviour of seismic-resistant buildings relies heavily upon the inclusion of energy dissipating devices. For concentrically-braced frames, this function is accomplished by diagonal bracing members whose performance depends upon both cross-sectional properties and global slenderness. Traditionally preferred rectangular hollow sections are susceptible to local buckling, particularly in cold-formed tubes, owing to the residual stresses from manufacture. This paper explores the response of hollow and concrete-filled circular tubes under cyclic axial loading. The uniformity of the circular cross-section provides superior structural efficiency over rectangular sections and can be further optimised by the inclusion of concrete infill. A series of experiments was conducted on filled and hollow specimens to assess the merit of the composite section. Comparisons were drawn between hot-finished and cold-formed sections to establish the influence of fabrication on member performance. Two specimen lengths were utilised to assess the influence of non-dimensional slenderness. Parameters such as ductility, energy dissipation, tensile strength and compressive resistance are presented and compared with design codes and empirically derived predictions.

Experimental investigation on lightweight concrete-filled cold-formed elliptical hollow section stub columns

“…This could be explained by the fact that significant changes that propagated in the stub column geometry as the test progressed. As the axial displacement increased, the CHS stub column buckled in a ringshaped mode at two or more locations along the length, and these rings were eventually compressed together, becoming very stiff, similar observation was reported by Sheehan and Chan [23]. In this paper, to ease for comparison, the ultimate test load, N u,filled was defined as the point of first distinctive peak (marked with "O" in the Fig.…”

Cyclic Performance Evaluation of Hollow Structural Section (HSS) and Concrete-Filled Tube (CFT) Braces

“…In this study, the energy dissipation is de¯ned as external work and is equal to the area enclosed via brace axial force-brace axial deformation hysteresis curves, similar to the de¯nition used by Sheehan and Chan. 2 Previous studies showed that the energy dissipation of HSS members is increased by concrete in¯ll 2,14 but none of these studies specify which parameters, namely width (diameter)-to-thickness ratio and length-to-width (diameter) ratio, have more signi¯cant e®ect on the contribution of concrete in¯ll in increasing the energy dissipation of HSS members.…”

“…Hollow Structural Section (HSS) and Concrete-Filled Tube (CFT) have been widely used as braces, as indicated in extensive numerical and experimental research studies. [1][2][3][4][5][6] Schneider, 7 Shams and Saadeghvaziri, 8 Huang et al 9 have investigated the e®ect of the cross-section shape and thickness on the ultimate strength of CFT columns under axial load. The results have shown that the short circular CFT columns loaded axially convey an elastic-perfectly plastic behavior and also have more post-yield axial ductility compared to square or rectangular CFT columns.…”

Prediction of ductile fracture for circular hollow section bracing members under extremely low cycle fatigue

“…Experimental studies on cyclically loaded bracing members (i.e. Tremblay [1], Fell [2], Nip et al [3,4], Sheehan and Chan [5] and Elchalakani et al [6]) has been conducted to investigate the influence of geometry, material type and manufacturing process on their hysteretic response, ductility capacity and fracture life. Fracture initiated soon after the occurrence of local buckling, due to the accumulation of high local strains, causing sudden strength loss.…”

“…As a result, the prescribed ductility levels, such as the maximum inter-story drift for a braced frame, were not achieved. From previous experimental investigations [1][2][3][4][5][6], the diameter-to-thickness ratio (D/t) and member slenderness (KL/r) were found to have a major influence on the cyclic-loading-induced fracture of bracing members, where D, t, L and r are the diameter, thickness, length and radius of gyration, respectively, of the tube, and K is the effective length factor. However, quantifying the effects of these parameters on the fracture life of bracing members remains a challenge.…”