钢管纤维自应力自密实混凝土柱设计理论研究

为改善钢管高强混凝土柱的延性，解决核心混凝土振捣困难，降低收缩徐变对结构性能的不利影响，将纤维混凝土、自应力自密实混凝土和钢管高强混凝土技术相结合，提出一种新型组合结构—钢管纤维自应力自密实高强混凝土柱。研究纤维自应力自密实高强混凝土的配合比和工作性能，分析硬化后约束混凝土的宏观力学性能和细观结构，揭示纤维自应力自密实高强混凝土的膨胀机理，提出其自应力设计理论。在此基础上，通过钢管纤维自应力自密实高强混凝土柱的轴心受压、偏心受压和受剪试验，研究纤维种类、纤维掺量、自应力值和套箍率等因素对其力学性能的影响；通过新型组合柱低周反复加载试验，研究不同轴压比下，上述因素对其滞回特性的影响；通过新型组合柱的受压长期持载试验，研究其收缩和徐变特性。结合理论分析和数值模拟，提出钢管纤维自应力自密实高强混凝土柱轴压、偏压、受剪承载力及相应的抗震设计方法，建立收缩徐变计算公式。

A new type of composite structure is developed by using fiber reinforced self-stressing and self-compacting high strength concrete as filling materials to improve the ductility of high strength concrete filled steel tube (CFST) columns, to overcome the difficulty in core concrete vibration, and to reduce the negative effect of the shrinkage and creep of concrete on structural properties. The optimal mixture proportions of fiber reinforced self-stressing and self-compacting high strength concrete are determined by analyzing the microstructure and mechanical properties of the core concrete and a design theory is then proposed for fiber reinforced self-stressing and self-compacting high strength concrete. A series of tests are conducted on composite structures under axial, eccentrical, and shear loads to study the effects of the type of fiber, the steel fiber volume fraction, the magnitude of self-stress, and the steel proportion on the mechanical properties of fiber reinforced self-stressing and self-compacting high strength concrete filled steel tube (FSH-CFST) columns. Based on the low-period cyclic load tests of FSH-CFST columns, the effects of the type of fiber, the steel fiber volume fraction, and the steel proportion on the hysteresis behavior and energy absorption capacity under the same axial-load level are studied. Long-term tests are carried out to investigate the shrinkage and creep of FSH-CFST columns under sustained load. Finally, theoretical analysis and numerical simulation are combined to propose a design method of FSH-CFST columns under axial, eccentrical, shear, and seismic loads. The equations are also formulated for calculating the shrinkage and creep of FSH-CFST columns.