FRP约束再生骨料混凝土内钢管组合柱基本力学性能及抗震性能研究

Construction waste recycling is an important task of the construction industry in the energy-saving and emission-reduction aspect, as well as structural seismic design is one of key problems of structural safety. The objects of this research are a new form of hybrid tubular columns which consist of an outer FRP tube and an inner steel tube, with the space between filled with recycled aggregate concrete. The important performance of the hybrid columns are perfect durability, anti-seismic capability and high value-added recycling waste concrete. Based on the existing research, the research will be conducted on the hybrid FRP-recycling waste concrete-steel tubular columns to study their failure mode, load capacity, deformation capacity and energy dissipation capacity. Firstly an experimental programme in which the hybrid columns are tested subjected to monotonic and cyclic concentric axial compression will be under way to examine these impotant parameters, involving recycled aggregate replacement rate, concrete strength, void ratio (i.e. ratio between the inner diameter and the outer diameter of the annular concrete section), the diameter-to-thickness ratio of the steel tube, the thickness of FRP tube and cyclic loading paths. And a stress-strain model for the confined recycling waste concrete in the hybrid columns will be proposed. Secondly, based on the above model and tests under combined axial compression and cyclic lateral loading, the finite element model using fiber beam element will be developed to examine the parameters on recycled aggregate replacement rate, concrete strength, axial compression ratio and whether to provide shear connection between inner steel tube and concrete, and deeply understand the seismic behavior of the hybrid columns. The result will provide an important reference and scientific basis for the practical application of hybrid FRP-recycling waste concrete-steel tubular columns.

建筑废弃物再生利用是建筑业节能减排的重要工作，结构抗震设计是结构安全的核心问题之一。本项目的研究对象为一种新型组合结构，即外FRP管内钢管中间填充再生骨料混凝土空心柱结构，其重要特点是耐久性能、抗震性能优越和废弃混凝土高附加值再生利用。本项目拟在现有研究基础上研究FRP约束再生骨料混凝土内钢管组合柱破坏形式、承载能力、变形能力和耗能能力等。基于单调和循环轴压试验研究再生骨料替代率、混凝土强度、试件空心率、内钢管径厚比、FRP管厚度、循环加载路径等参数对该组合柱基本力学性能的影响，并建立约束再生骨料混凝土应力-应变关系模型；利用此模型，并结合以组合柱拟静力试验，建立基于纤维梁单元的理论模型以考察再生骨料替代率、混凝土强度、轴压比、加载方式以及内钢管和混凝土之间是否提供剪力连接件对新型组合管柱抗震性能的影响，以深入了解其抗震性能，为FRP约束再生骨料混凝土内钢管组合柱的实际应用提供理论依据。

本项目提出了一种纤维复合材料（简称FRP）约束再生混凝土内钢管空心组合圆柱（简称FRSTC）。该新型柱由外FRP管，内钢管及双管环形区域内再生混凝土构成。.首先，对FRSTC进行了单调轴压性能研究，通过对荷载-轴向位移、荷载-FRP应变、荷载-钢管应变、FRP环向-轴向应变等关系曲线的研究，探讨了FRP管厚度、PRP材料、再生骨料替代率等对FRSTC轴压性能的影响。研究结果表明： FRST极限承载力随着再生骨料替代率的增加有下降趋势，而极限轴向位移有增加趋势；DSTC的极限轴压承载力计算模型对于FRSTC依然适用。.其次，对FRSTC进行了循环轴压性能研究。通过对荷载-轴向位移、应力-应变包络线、FRP环向应变等的研究，分析了再生骨料替代率、再生混凝土强度、加载速率等对FRSTC循环轴压性能影响，建立了约束再生混凝土的残余应变与卸载应变关系、应力退化率与包络卸载应变关系。研究结果表明：低强再生混凝土柱的应力-应变曲线有明显的强化段，高强再生混凝土柱应力-应变曲线在刚进入强化段时有一定回落，不同再生骨料替代率对FRSTC承载力影响不大；FRP约束普通混凝土的循环轴压应力-应变模型的加/卸载曲线模型适用于FRSTC柱的循环轴压性能预测。.然后，对FRSTC开展了在恒定轴压和往复水平荷载作用下的拟静力试验。通过对滞回曲线、骨架曲线、承载力退化系数、延性系数、位移转角、曲率、等效塑性铰高度、刚度退化系数、耗能、等效粘滞阻尼系数、累积损伤系数等的研究，分析了再生骨料替代率、轴向加载方式、剪力连接件、FRP管材类型、钢管厚度、试件空心率、FRP管厚度、轴压比、再生混凝土强度等对FRSTC抗震性能的影响。研究结果表明：FRSTC柱滞回曲线呈现饱满的梭形，试件变形和耗能性能良好；再生骨料替代率影响较小；折线型恢复力模型能较好地预测试件的滞回性能。.FRSTC具有承载力高、延性好的特点，可为建筑结构提供一种新型的高性能环保型构件形式。同时解决废弃混凝土的环境污染问题，实现资源的可持续发展，扩大和提升RAC的应用范围和层次。