Experimental Research on the Flexural Behavior of Thin Protective Concrete-Encased Narrow Rectangular Concrete-Filled Steel Tube Columns
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摘要: 为推进适用于产业化生产的高性能钢结构住宅体系,提出了一种防护型薄混凝土外包窄矩形钢管混凝土柱。其构件具备工业化生产、装配式施工、减少抹灰工序及降低使用期维护成本等优点。为研究其在静载荷作用下的整体力学性能及薄混凝土外包层的受力与破坏形态,设计并完成了3个薄混凝土外包矩形钢管混凝土柱试件的轴心与偏心受压试验。试验以偏心距为主要变化参数,重点分析不同偏心条件下试件的承载力、破坏特征、荷载-位移曲线、荷载-挠度曲线、荷载-应变曲线以及外包混凝土层的开裂与破坏情况。试验结果表明:采取构造措施使薄混凝土外包层在柱端不直接受力、柱中与钢管协同工作,可有效改善钢管柱的整体受压稳定性;当构件长边方向偏心距较小时,因钢管截面尺寸相对较小,其破坏可能由弯矩作用平面外的受压承载力控制;在全截面受压状态下,采取适当抗裂措施的外包混凝土层在正常使用荷载下未出现新增裂缝及剥离破坏,试件极限破坏形态均表现为端部钢管长边方向的局部鼓曲,设计需采取合适的加强措施。Abstract: To promote high-performance steel structure residential systems suitable for industrial production, this paper presents a thin protective concrete-encased narrow rectangular concrete-filled steel tube (CFST) column. This component offers several advantages, including industrialized production, prefabricated construction, reduced plastering procedures, and lower maintenance costs throughout its service life. To investigate the overall mechanical properties of this system under static loading, as well as the load transfer and failure modes of the thin concrete cladding, axial and eccentric compression tests were designed and conducted on three thin protective concrete-encased rectangular CFST column specimens. The tests utilized eccentricity as the primary variable, focusing on the analysis of bearing capacity, failure characteristics, and the load-displacement, load-deflection, and load-strain curves of the specimens under varying eccentricity conditions. Additionally, this study examined the cracking and failure of the thin concrete cladding. The test results indicated that: 1)Implementing structural measures to prevent the thin concrete cladding from directly bearing loads at the column end, while ensuring compatibility with the inner steel tube, significantly enhanced the overall compressive stability of the steel tube column. 2)When the eccentricity in the long-side direction of the component was minimal, the relatively small cross-sectional area of the steel tube resulted in the failure mode being governed by the compressive bearing capacity associated with the out-of-plane bending moment. 3)In a fully compressed cross-section state, the thin concrete cladding, when equipped with appropriate anti-cracking measures, did not exhibit cracks or peeling failure under normal service loads. The ultimate failure modes of the specimens consistently manifested as local bulging in the long-side direction of the end steel tube. Consequently, appropriate reinforcing measures should be incorporated into the design.
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