Use of High-Performance Fiber Reinforced Cement Composites to Increase the Displacement Capacity of Structural Walls

在地震区的中低层结构中，结构墙被广泛用作抗侧力构件；此外，对于不符合现行规范要求的既有结构，结构墙通常被认为是主要的加固补救措施。这项研究的主要目的是通过使用高性能纤维增强水泥复合材料(HPFRCC)开发一种新的钢筋混凝土(RC)结构墙体设计。这些材料具有拉伸应变硬化响应和高压缩应变能力。在本项目中，将首先进行一项试验研究，以了解高性能混凝土碾压混凝土材料建造的结构墙在位移反转作用下的剪切和弯曲性能。这一实验阶段将包括测试几种用聚乙烯(Spectra)或钢纤维加固的高强混凝土结构墙。重点研究了材料开裂后强度和应变能力、墙体高宽比、剪应力水平和配筋方式等变量对高强混凝土墙体受力性能的影响。分析研究的目的将是开发模型来预测高强混凝土墙体在位移反转作用下的剪切和弯曲性能。为此，现有的预测钢筋混凝土构件反应的理论将被修正，以考虑HPFRCC材料优越的拉伸和压缩性能。此外，还将开发简化模型来估算HPFRCC结构墙体在不同性能水平下的抗剪强度与位移关系和位移极限。将探索使用压杆和拉杆模型来预测HPFRCC墙的抗剪强度，其中压杆和拉杆的强度系数是通过材料和墙试验得出的。最后，将制定高性能混凝土抗震墙的配筋详细要求的规定。

Structural walls are widely used as lateral load resisting elements in low- and medium-rise structures located in seismic zones; moreover, they are often considered a primary retrofit remedy for existing structures that do not meet current code requirements. The main focus of the proposed research is to develop a new design for reinforced concrete (RC) structural walls through the use of high-performance fiber reinforced cement composites (HPFRCCs). These materials offer a tensile strain-hardening response, and high compression strain capacity. In this project, an experimental study will be first conducted to understand the shear and flexural behavior of structural walls constructed with HPFRCC materials under displacement reversals. This experimental phase will include the testing of several squat and slender HPFRCC structural walls reinforced with either polyethylene (Spectra) or steel fibers. Emphasis will be placed on studying the effect of variables such as material post-cracking strength and strain capacity, wall aspect ratio, shear stress level and reinforcement detailing on the behavior of HPFRCC structural walls. Analytical studies will be aimed at developing models to predict the shear and flexural behavior of both squat and slender HPFRCC walls under displacement reversals. For this purpose, existing theories developed to predict the response of reinforced concrete members will be modified to account for the superior tension and compression behavior of HPFRCC materials. Simplified models will also be developed to estimate the shear strength vs. displacement relationship and displacement limits corresponding to various performance levels in HPFRCC structural walls. The use of strut-and-tie models, with strength factors developed for struts and ties from material and wall tests, will be explored to predict the shear strength of HPFRCC walls. Finally, provisions for reinforcement detailing requirements will be developed for seismic-resistant HPFRCC walls.