复材管约束再生砖骨料混凝土柱的力学性能与设计方法

Waste bricks account for the largest fraction (approximately 50%) of China’s construction and demolition waste (C&D waste). An efficient way of utilizing waste bricks is to reuse them as recycled aggregates to partially or totally substitute natural aggregates for fabricating new concrete (i.e. recycled brick aggregate concrete, RBC). RBC generally exhibits inferior mechanical and durability properties compared with natural aggregate concrete due to the relatively high water absorption and low strength of bricks. Against this background, this project proposes a new composite column form, RBC-filled fiber reinforced polymer (FRP) tubes (RBCFFTs), in which the FRP tube provides significant enhancement of RBC mechanical properties through confinement and significant improvement of RBC durability through corrosion insulation. In this project, a systematic study will be conducted on RBCFFTs at three progressive levels (stress-strain behavior, column behavior and design methods) using a combined experimental, numerical and theoretical approach. Stress-strain models capable of considering the effects of key parameters, including strength of RBC, FRP confinement level, eccentricity and size, will be first developed, followed by the establishment of theoretical column models capable of simulating the static and seismic behavior of RBCFFTs, and finally a corresponding design procedure will be proposed for the design of axial load capacity and ductility of RBCFFTs. This project addresses China’s current urgent demands of advancing C&D waste utilization and is thus of significant importance to the sustainable development of the construction industry of China.

我国建筑垃圾中占比最大的是废旧砖（约占50%）。废旧砖的高效利用方式是将其制成再生骨料部分或全部取代天然骨料而生成再生砖骨料混凝土。由于砖吸水率较大、强度较低，再生砖骨料混凝土的力学性能与耐久性一般弱于天然骨料混凝土。本项目提出纤维增强复合材料管（复材管）约束再生砖骨料混凝土柱组合构件，利用复材管的约束作用大幅提升再生砖骨料混凝土的力学性能，同时利用复材管优越的耐腐蚀性大幅改善再生砖骨料混凝土的耐久性。本项目将结合试验研究、数值模拟与理论分析，从本构关系、构件性能与设计方法三个层面对复材管约束再生砖骨料混凝土柱展开系统研究，首先提出考虑再生砖骨料混凝土强度、复材约束量、偏心距、尺寸等关键参数的本构模型，然后探明构件的静力和抗震性能并发展理论分析模型，最终建立相应的构件承载力与延性设计方法。本项目符合当前我国大力推进建筑垃圾资源化的迫切需求，对我国建筑业可持续发展具有重要意义。

废旧砖是我国建筑垃圾的主要成分。废旧砖的高效利用方式是将其制成再生骨料部分或全部取代天然骨料而制成再生砖骨料混凝土。由于砖吸水率较大、强度较低，再生砖骨料混凝土的力学性能与耐久性一般弱于普通混凝土。本项目提出复材管约束再生砖骨料混凝土柱组合构件，利用复材管的约束作用大幅提升再生砖骨料混凝土的力学性能，同时利用复材管优越的耐腐蚀性大幅改善再生砖骨料混凝土的耐久性。本项目通过试验研究、数值模拟与理论分析对复材管约束再生砖骨料混凝土柱展开了系统研究。主要研究内容包括：1）复材约束再生砖骨料混凝土抗压性能；2）复材约束再生砖骨料混凝土尺寸效应；3）再生砖骨料混凝土主动约束性能；4）复材约束再生砖骨料混凝土应力应变模型；5）复材约束再生砖骨料混凝土三维有限元模拟；6）复材管约束再生砖骨料混凝土柱力学性能与分析设计。此外还研究了复材约束再生砖粉/砖块/砼骨料混凝土的力学性能。项目研究揭示了复材约束再生砖骨料混凝土与复材约束普通混凝土的异同。相同之处在于复材约束同样能显著提升再生砖骨料混凝土的抗压强度和变形能力。不同之处包括：复材约束再生砖骨料混凝土中会产生穿越砖骨料的裂缝；砖骨料受压时因孔隙坍塌而减小混凝土膨胀，从而会减弱复材的约束效率。在此基础上，项目建立了适用于复材约束再生砖骨料混凝土的应力应变模型和适用于复材管约束再生砖骨料混凝土柱的分析设计方法。项目研究成果也为废旧砖、废旧砼的多尺度综合利用打下了基础。