تحلیل المان محدود در مورد رفتار لرزه ای ستونهای کامپوزیتی قاب بتن فولادی تقویت شده توسط CFRP Experimental research and finite element analysis on seismic behavior of CFRP-strengthened seismic-damaged composite steel-concrete frame columns

1. Introduction The frame column structure composed of sections of steel-reinforced concrete has been widely used in super-high building structures and large span structures due to its high load-carrying capacity, good seismic performance, and other advantages [1]. Seismic evaluation and strengthening of composite steel-concrete structures are not mentioned in guidelines publications, such as “Standard for Seismic Appraisal of Buildings” (GB50023-2009),“Technical specification for seismic strengthening of buildings” (JGJ116-2009) and “Technical guidelines for seismic evaluation and strengthening of post-earthquake buildings”. In practical engineering, the carbon fiber sheet has received considerable attention due to its high-strength, light-weight, high corrosion resistance, and ease of fabrication, etc. This effective strengthening method using composite steel-concrete structures has become more and more widely used in the United States, Canada, Japan, and recently, Europe. In China, the research and application of carbon fiber reinforced polymer (CFRP) for strengthening reinforced concrete structures began in 1997. Several studies have been conducted on the seismic performance and behavior under reinforced concrete [2–4] and composite steel–- concrete columns [5–7], steel fiber reinforced concrete (SFRC) [8] and concrete-encased composite structures of concrete frame and steel–- concrete composite columns, as well as the behavior under ultra-high performance fiber reinforced concrete (UHPFRC) [9–11] and numerical simulation methods [12,13]. The design calculation theory and construction method are given in the building codes, such as ACI 318- 05code [14], JGJ 138-2001 specifications [15], AIJ-SRC standard [16] and the AISC Manual of Steel Construction [17]. In experimental research, these include, a study on seismic-damaged RC column, frame and beam–column joints strengthened with stainless steel wire mesh composite [18], CFRP [19], and epoxy resin injection [23–25], respectively. The method of CFRP-strengthened seismic-damaged exterior joints in composite frame consisting of CFSST columns and steel beams were proposed by Xu et al. [20]. A detailed investigation on the assessment of the performance of new material was presented by Zhang [21], and the theoretical development of the mechanical properties of new material with the time was extensively studied by Wang [22]. According to published experimental studies, RC structures could be strengthened with new material [21,22].