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，结构墙作为抗侧力构件被广泛应用；此外，它们通常被认为是不符合当前规范要求的现有结构的主要改造补救措施。提出的研究的主要重点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）结构墙设计。这些材料提供拉伸应变硬化响应和高压缩应变能力。在本项目中，将首先进行实验研究，以了解HPFRCC材料结构墙在位移逆转下的剪切和弯曲行为。这个实验阶段将包括测试几个用聚乙烯（Spectra）或钢纤维加固的矮矮的和细长的HPFRCC结构墙。重点将放在研究诸如材料开裂后强度和应变能力、墙体长径比、剪应力水平和钢筋细部等变量对HPFRCC结构墙性能的影响。分析研究将旨在开发模型来预测深蹲和细长HPFRCC墙在位移逆转下的剪切和弯曲行为。为此，现有的预测钢筋混凝土构件响应的理论将被修改，以解释HPFRCC材料优越的拉伸和压缩性能。还将开发简化模型来估计HPFRCC结构墙在不同性能水平下的抗剪强度与位移关系和位移极限。通过材料和墙体试验为支柱和纽带开发强度因子，将探索使用支柱和纽带模型来预测HPFRCC墙体的抗剪强度。最后，将为耐震HPFRCC墙体制定钢筋细部要求。

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.