Collapse Responses of Concrete Frames Reinforced with BFRP Bars in Middle Column Removal Scenario

Abstract

Six concrete beam-column frame sub-assemblages reinforced with basalt fiber-reinforced polymer (BFRP) bars in the frame beams were designed to investigate the collapse resistance after a middle column removal. Effect of parameters, including span to depth ratio of frame beams, prestressing, as well as material types of stirrups in the beams, on the collapse resistance of the sub-assemblages, was investigated. Experimental results showed that the initial stiffness of the frame beams was apparently lower due to low elastic modulus of BFRP bars. The collapse resistance of the sub-assemblages presented wave-like increasing tendency with the vertical displacement of the failed middle column, and it mainly attributed to the cracking or crushing of concrete and rupture of BFRP bars in the frame beams. Top longitudinal BFRP bars at the beam ends near to the side column (BESCs) and bottom longitudinal BFRP bars at the beam ends near to the middle column (BEMCs) kept tensile during the loading process, which played an important role in resisting structural collapse. Adjacent structural members such as frame beams and columns could provide horizontal reaction forces to constrain the free deformation of the residual sub-assemblages after the middle column failed, and it was beneficial to mitigate the structural collapse risk. The vertical deformation of the frame beams was nearly linear and proportional to the vertical displacement of the failed middle column. Finally, the dynamic increase factor (DIF) of collapse load was discussed using energy conservation method, and a calculation method of DIF for prestressed concrete frame structures was developed. It was suggested that the DIF values for the non-prestressed frame structures reinforced with BFRP bars in the beams should be taken as 2.0, while those for the prestressed sub-assemblages can be taken between 1.44 and 2.0.

A preliminary analysis and discussion of the condominium building collapse in surfside, Florida, US, June 24, 2021

“…Remarkably, the FE method has been used in many existing studies to simulate the collapse behavior of buildings. For instance, a number of FE method-based studies have focused on the collapse resistance of structures before the formation of debris [21][22][23][24][25][26][27][28]. In contrast, studies on the collapse debris distribution are relatively limited, mainly due to the high computational cost of the FE simulations for such problems [20,29].…”

Impact of seismic retrofitting on progressive collapse resistance of RC frame structures

“…In addition, the robustness of sub-assemblages increased as the span to depth ratio of beams decreased. Kim et al [71] experimentally investigated the influence of anchorage techniques by varying the geometry and amount of CFRP materials on ten beam specimens. That study demonstrated that the full strength of CFRP sheets on the side faces could be achieved only by a combination of CFRP anchors and U-wraps.…”

Experimental Study and Numerical Analysis of Flexural Strength of BFRP Bar Concrete Beams Reinforced with Bamboo Fiber and Steel Wire Mesh

“…They are widely used in concrete structures such as bridges, roads, and wharfs [2]. Many experts and scholars have conducted in-depth research and analysis on the failure modes, mechanical properties, and bonding properties of BFRP bar concrete beams [3][4][5][6][7][8]. The low elastic modulus of BFRP bars causes large deformation of the concrete components and an increase of crack widths.…”