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

美国对家庭和企业可持续、抗灾但价格低廉的低层建筑有着持续的需求。该研究项目的目标是研究高质量钢筋土砌体（REM）用于抗震低层建筑的可行性。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，将可持续且适合当地但易碎的未烧土砌体转变为更坚固、更具延展性的系统来实现。本研究将研究REM作为低层工业建筑和棚屋的低成本选择，旨在通过降低建设和维护成本来促进小型工厂和仓库的发展，从而促进经济发展。本研究的技术目标如下：(1) 为抗震低层建筑设计、原型设计并验证一种经济实惠且高质量的 REM 系统；(2) 制定、验证和实施新的数值模型，以准确有效地预测 REM 墙的结构响应。假设是：v(1) 用 9% 或更少的水泥稳定土块和砂浆的工程，并用 1% 或更少体积分数的再生塑料纤维加固，与内部钢筋相结合，将改变 REM 的强度和延展性，使其适合抗震建筑，以及 (2) 基于新开发的非线性宏观单元 (ME) 的计算高效数值模型，其运动学由尽可能小的自由度数描述，将能够准确预测 REM 的响应承受静态和动态载荷的结构。这项研究将分三个阶段进行。首先，将通过材料和组合件的负载测试来表征选定的原型块砂浆组合（未加固、纤维加固和用灌浆钢筋加固的纤维）。第二阶段将选择候选强化系统。三维（3D）数字图像相关（3D-DIC）将用于测量全场变形图并为数值模型的开发提供信息。由此产生的材料、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，将通过对 REM 墙进行准静态循环载荷的大规模测试和 3D-DIC 监测来获得性能数据。结果将为新结构 ME 模型及其 FE 代码实施的制定和验证提供信息。第三个也是最后一个，大型样本的基于 ME 的有限元模型将根据数值结果和实验结果之间的比较来开发。由此产生的第一代 ME 模型将用于初步估计抗震设计系数和因素，以确定可行性。此外，还将对代表性 REM 材料和建筑的可持续性相关参数和建筑成本进行初步量化，为与轻质框架木材等替代系统进行比较以及生命周期成本分析提供基础。

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.