低周反复荷载下钢筋-钢纤维再生混凝土粘结损伤演化机理及本构模型

Steel fiber recycled coarse aggregate concrete (SFRCAC) has significant performance, and its evolution mechanism and constitutive relation are the basic problems in structural member design. The bond tests of monotonic loading and low cyclic reversed loading will be conducted with the consideration of various volume fractions and aspect ratio of steel fiber, replacement ratios of recycled coarse aggregate, reinforcement diameters, anchoring lengths, concrete strengths and stirrup ratios. The main content is shown as follows: (1) The effects of various factors on the bond strength will be investigated. Based on the mechanical model of thick wall cylinder and the action mechanism of steel fiber, a calculation formula of bond strength and a bond-slip constitutive relation associated with the position function will be proposed. (2) By using acoustic emission technique, the damage evolution law and failure mechanism will be studied. Based on the theory of damage mechanics, ahysteretic model of bond damage, which can comprehensively reflect the strength degradation, rigidity degeneration, and energy dissipation will be proposed. The statistical analysis method will be used to develop the skeleton curve model of bond damage. The developed skeleton curve model matches the bond-slip constitutive relation of monotonic loading. The expected research results can enrich the basic theory of SFRCAC and promote the applications of SFRCAC in structural engineering.

钢纤维再生混凝土性能良好，其粘结损伤演化机理及本构关系是结构构件设计的基础问题之一。本项目采用单调和反复拉拔试验，考虑钢纤维体积率、钢纤维长径比、再生粗骨料取代率、钢筋直径、混凝土强度、锚固长度和配箍率等影响因素，研究内容有：(1)上述因素对钢筋与钢纤维再生混凝土粘结强度的影响；基于厚壁圆筒力学模型和钢纤维增强机理，建立能够综合反映各变化参数影响的粘结强度计算公式；基于粘结应力位置函数关系式，提出考虑粘结位置影响的粘结滑移本构模型。(2)结合声发射技术研究钢筋与钢纤维再生混凝土的粘结损伤演化机理；引入能综合表征粘结强度衰减、刚度退化、累积能量耗散等滞回特征值变化规律的损伤因子，基于损伤力学，建立粘结损伤滞回规则；利用统计分析方法，建立与单调加载粘结滑移本构关系相统一的粘结损伤骨架曲线模型。预期成果可丰富钢纤维再生混凝土的基本理论，推动其在工程结构中的应用。

钢纤维再生混凝土是力学性能良好、绿色环保的新型建筑材料，本项目围绕其粘结滑移性能、劣化机理及粘结-滑移本构关系等方面开展研究。.通过84个单调加载中心拉拔试验，研究了钢纤维体积率、再生粗骨料替代率、混凝土保护层厚度、箍筋约束、钢筋锚固长度对钢筋钢纤维再生混凝土粘结强度、粘结滑移曲线的影响。试验结果表明：粘结强度随再生粗骨料替代率、钢筋锚固长度的增加而降低，随钢纤维体积率、钢筋保护层厚度和配箍率的增加而提高。其中，与再生粗骨料替代率为50%和100%的再生混凝土相比，掺入体积率1.5%的钢纤维后，粘结强度分别提高了15.2%和19.6%；与普通混凝土相比，再生粗骨料替代率100%的混凝土粘结强度降低达17.9%。在此基础上，通过试验结果回归分析，建立了钢纤维再生混凝土极限粘结强度计算公式。此外，通过钢筋开槽贴应变片的粘结试验结果，分析了粘结应力与相对滑移沿锚固长度的分布规律，建立了钢纤维再生混凝土粘结-滑移本构模型。.通过36个低周反复加载试验，重点研究了钢纤维体积率、再生粗骨料替代率、配箍率对钢筋钢纤维再生混凝土粘结性能的影响。试验结果表明：往复荷载下试件的粘结滑移全过程可分为弹性阶段、裂缝扩展阶段、破坏阶段和裂缝闭合阶段；与单调加载相比，往复荷载下各试件粘结强度有明显退化；随再生粗骨料替代率的增加，试件粘结强度退化率增大，耗能减小；掺入钢纤维和增加配箍率可明显改善再生混凝土的粘结强度退化和滞回耗能。在此基础上，通过回归分析建立了低周反复荷载下钢纤维再生混凝土混凝土的粘结-滑移滞回骨架曲线模型。