复材约束混凝土核心增强方形空心钢管混凝土压弯性能研究

Bridge is of great significance in connecting the traffic networks of cities, especially in high seismic regions. Therefore, the developments of bridge members that have lighter weight, superior performance and longer service life with lower cost are the preconditions for larger span and height of bridge. At present, the concrete-filled steel tube (CFST) box has great popularity in engineering practice as bridge pier or main arch, which has high load-bearing capacity, superior flexural and torsional stiffness and high energy-dissipation capacity. However, the further requirements for higher load-bearing capacity and ductility are elicited with the improving of bridge scale. To meet these requirements, the strengths of steel and concrete must be promoted, which brings new challenges that the confinement of high strength steel tube to core concrete is weak and the ductility is excessive low. This study is aiming to propose a novel member, concrete-encased CFST box with FRP confined concrete cores, which could provide strong confinements to the core concrete, reducing the self-weight of structure, obtaining superior flexural and torsional stiffness, improving the load-bearing capacity and ductility, especially available for the applications in high seismic region. This study plans to develop the experimental investigations, finite element analysis and theoretical study in terms of the novel member under axial compression and combined compression and bending.

桥梁建设作为关系整个城市或交通网安全性的生命线工程具有重要意义，尤其对于高地震烈度区，发展轻量化、高性能、低成本、长寿命的桥梁结构构件是增加桥梁跨度与高度的前提条件。目前空心方钢管混凝土构件是一种在桥梁工程中已有广泛应用的结构构件（桥墩、主拱），其具有承载力高、抗弯和抗扭刚度大、抗震性能优等优势。但面临更大跨度和高度的桥梁结构，对承载力和延性提出了更高的要求，需采用高强钢材和高强混凝土，此时方钢管对混凝土的约束效果较弱，延性尤其不足。本项目旨在开发一种复材约束混凝土核心增强方形空心钢管混凝土构件，通过在双壁空心方钢管混凝土内部配置复材管，对混凝土形成很强的内部约束，减轻结构自重的同时可以达到很好的抗弯和抗扭刚度，改善对内部混凝土约束弱和延性低的劣势，提高构件的延性和承载力，尤其适合在地震区结构中应用。针对此新型组合构件，本项目将进行其在轴压和偏压工况下的试验研究、数值模拟及理论分析。

本文建议了一种采用纤维增强复合材料（Fiber Reinforced Polymer，FRP，简称复材）、钢材和混凝土的新型组合柱：复材约束混凝土核心增强方形空心钢管混凝土柱（Hollow concrete-filled steel tube box with FPR confined concrete core，CFSTFC），由外部方钢管、内置复材圆管、两者之间的夹层混凝土及复材管内部的核心混凝土（FRP-Confined Concrete Core, FCCC）和中心空圆钢管五个部分组成。本研究对此组合柱的偏压性能开展了试验研究、理论分析和数值模拟。完成了14个CFSTFC偏心受压短柱及4个轴心受压短柱试验研究，共计18个试件。考虑了偏心距、复材厚度、钢厚度、混凝土强度四个变量对CFSTFC柱偏压受力性能的影响，采用三维扫描技术，获得了加载过程中关键受力状态对应的构件外部变形，结合有限元软件，确定了钢管膨胀变形过程及其受力情况。通过试验，得到了此类构件偏心受压破坏的全过程和主要破坏模式，确定了两种典型的CFSTFC荷载-位移曲线类型，发现其荷载-变形行为与传统构件不同：具有显著的屈服后刚度和稳定的峰值后残余承载力，具有良好的偏压受力性能。本研究采用MSC.Marc有限元软件，建立了CFSTFC数值模拟模型，考虑了不同截面摩擦系数、6个主要参数对构件偏压受力性能的影响，包括混凝土强度、钢材强度、复材强度、钢管厚度、复材管厚度、偏心距，并进行了参数扩展分析。提出了M-N关系模型理论确定方法，进行了M-N参数扩展分析。建立了CFSTFC这一新型构件的设计计算方法，并证明其具有独特且优越的受力性能，在重载结构中具有广阔的应用前景。