Collaborative Research: Engineered Earth Masonry for Affordable Seismic Resistant Low-Rise Buildings

在美国，家庭和企业对可持续和抗风险的低层建筑的需求持续存在，但价格非常实惠。本研究项目的目的是探讨高质量加筋土砌体(REM)在低层抗震建筑中的可行性。这一目标将通过使用不可生物降解的再生塑料纤维与内部钢筋相结合的方式，将可持续的、适合当地的但易碎的未烧土砖转化为更坚固、更具延展性的系统。这项研究将研究REM作为低层工业建筑和棚屋的低成本选择，以期通过降低建设和维护成本来促进小工厂和仓库的发展，从而促进经济发展。本研究的技术目标如下：(1)为低层抗震建筑设计、制作和验证一个经济实惠的高质量REM系统；(2)建立、验证和实施一个新的数值模型，以准确和有效地预测REM墙的结构反应。这些假设是：(1)用9%或更少的水泥稳定土块和砂浆，并用1%或更少体积分数的再生塑料纤维加固，结合内部钢筋，将改变REM的强度和延性，使其适用于抗震建筑；(2)基于新发展的非线性宏单元(MES)的计算高效的数值模型，其运动学被描述为尽可能少的自由度，将使REM结构在静力和动力荷载作用下的响应能够得到准确的预测。这项研究将分三个阶段进行。首先，选定的原型砌块-砂浆组合(未增强、纤维增强和灌浆钢筋纤维增强)将通过材料和组件的载荷测试进行表征。第二阶段将选择一个候选的加固系统。三维(3D)数字图像相关(3D-DIC)将被用来测量全场形变图并为数值模式的发展提供信息。由此得到的材料、砂浆接缝和REM组合的本构模型将用于制定详细的有限元(FE)模型。其次，通过REM墙体在准静态循环荷载作用下的大型试验和3D-DIC监测，获得性能数据。其结果将为新结构ME模型的制定和验证及其FE规范的实施提供参考。最后，通过数值计算结果与试验结果的比较，建立了基于有限元的大尺寸试件有限元模型。由此产生的第一代ME模型将用于初步估计地震设计系数和确定可行性的因素。此外，还将对具有代表性的可再生能源材料和建筑物的可持续性相关参数和建造成本进行初步量化，以提供与替代系统(例如轻型框架木材)进行比较的基础，并进行寿命周期成本分析。

There is a continuing demand in the United States for sustainable and hazard-resilient but highly affordable low-rise buildings for households and businesses. The goal of this research project is to investigate the feasibility of high-quality reinforced earth masonry (REM) for seismic resistant low-rise buildings. This goal will be achieved by transforming sustainable and locally appropriate but brittle unfired earth masonry into a stronger and more ductile system by using non-biodegradable recycled plastic fibers combined with internal steel reinforcement. This research will investigate REM as a low-cost option for low-rise industrial buildings and sheds, with a vision of fostering the development of small plants and warehouses by reducing construction and maintenance costs, thus promoting economic development. The technical objectives of this research are the following: (1) to engineer, prototype, and verify an affordable and high-quality REM system for seismic resistant low-rise buildings, and (2) to formulate, verify and implement a new numerical model to accurately and efficiently predict the structural response of REM walls. The hypotheses are:v(1) engineering of earth blocks and mortar stabilized with nine percent or less cement, and reinforced with one percent or less volume fraction of recycled plastic fibers, combined with internal steel reinforcement, will change the strength and ductility of REM, making it suitable for seismic resistant buildings, and (2) computationally efficient numerical models based on newly developed nonlinear macroelements (MEs), whose kinematics are described by the smallest possible number of degrees of freedom, will enable the accurate prediction of the response of REM structures subject to static and dynamic loads. This research will be conducted in three phases. First, selected prototype block-mortar combinations (unreinforced, fiber reinforced, and fiber reinforced with grouted steel bars) will be characterized through load testing of materials and assemblages. A candidate reinforced system will be selected for the second phase. Three-dimensional (3D) digital image correlation (3D-DIC) will be used to measure full-field deformation maps and inform the development of numerical models. The resulting constitutive models for materials, mortar joints, and REM assemblages will serve to formulate detailed finite element (FE) models. Second, performance data will be obtained through large-scale testing and 3D-DIC monitoring of REM walls subject to quasi-static cyclic loading. The results will inform the formulation and validation of new structural ME models and their FE code implementation. Third and final, ME-based FE models of the large-scale specimens will be developed based on the comparison between numerical and experimental results. The resulting first-generation ME models will be used for a preliminary estimate of seismic design coefficients and factors to establish feasibility. In addition, a preliminary quantification of sustainability-related parameters and construction cost for representative REM materials and buildings will be performed to provide a basis for comparison with alternative systems, for example, light-framed wood, as well as life-cycle cost analysis.