Experimental study of CFRP strengthened steel columns subject to lateral impact loads

Abstract

In both building and civil engineering structures, the occurrence of impact loading to column elements can be a significant issue, particularly in regard to disproportionate collapse. For existing structures vulnerable to impacts, the development of appropriate strengthening techniques is key to extending service life and improving robustness. In the case of structural steelwork, composites such as carbon fibre reinforced polymer (CFRP) offer a promising means of retrofitting and improving performance under impact. Towards this, the present study experimentally investigated a total of 12 square hollow section (SHS) columns under impact loads. The test series included both unstrengthened and CFRP strengthened samples with different fibre orientations with a view to finding the optimum CFRP configuration. As a means of simulating lateral impact on axially loaded elements, a purpose-built test rig was manufactured to apply a compressive preload to the samples prior to impact. Different preloading levels were applied to the samples before they were impacted transversely. The results show that the strengthening effectiveness increased with higher preloading level. The average reduction in the transverse displacement for the strengthened columns tested under 70% preloading level was around 32% compared to the unstrengthened column while this value was about 22% for the columns tested without compressive preload.

Loading rate effects on CFRP strengthened steel square hollow sections under lateral impact

“…It was found that applying CFRP in the transverse direction has the minimum contribution compared to other configurations, while using fibres in both directions provides the higher contribution. This is due to the ability of this configuration in preventing local and global buckling [9]. Regarding the preloading level, it was also found that in absence of the pre-compression load the SHS sample had lower transverse displacement as shown in Figure 5.…”

“…Recently, two experimental studies were published on the behaviour of CFRP strengthened steel hollow sections under impact load [9,10]. In the first study [9], strengthening of square hollow sections was examined with different CFRP configurations comprising fibres oriented in the longitudinal, transverse and both longitudinal and transverse directions. One of the main contributions of this study was the effect of axial pre-compression which represented pre-existing axial load on the columns prior to applying the impact load.…”

“…The current study makes a comparison between the effectiveness of CFRP under various loading rates (impact and quasi-static) which has not been investigated elsewhere. The previously referred to studies [9,10] have tested a series of strengthened samples under impact loading rate only.…”

“…The main aim of the present study is to compare the structural response of SHS steelwork strengthened with specific CFRP configurations at different loading rates. By understanding the response of this strengthening technique under various loading rates, ultimately a design guide can be established for different loading rates thus allowing practitioners to benefit from the considerable advantages this technique can offer [6,9]. The work presented here is an extension of a preliminary study on rectangular hollow sections conducted by the authors [15].…”

Experimental and Numerical Investigation of Steel Sections under Impact Effect

“…Researchers have been developing drop weight test setups that are based on free falling movement of hammer from various drop heights [12][13][14][15][16][17]. The drop-weight test setup is widely used in impact experiments in which impact load is applied to test members.…”