美国技术标准用弦线模量对我国技术更新的启示

用弦线模量计算地基变形是中国的原始自主创新。它改正了压缩模量和各种计算模型存在的问题，所以对计算结果有很大的改进。它依据土性物理指标用软件计算，是各种计算方法中最简单的方法。用于地基设计规范能够实现以变形控制设计的目标；用于黄土地区建筑规范，能够依据基础面积、基底压力、相邻基础影响等条件，并考虑地区差异、土性的微结构差异等条件真实地计算不同类型黄土的湿陷量，实现定量评价黄土湿陷性的目标。在中国对弦线模量研究的同时，美国在金属材料非线弹性变形计算中也研究并已经在其技术标准中采用了弦线模量代替杨氏模量，中国的同类标准也引用了它。这对在我国地基规范中采用弦线模量法进行技术更新，应该具有重要的启示作用。在简要介绍弦线模量法主要情况的基础上，进一步阐明这一观点。

Inspiration for China's technology update drawn from chord modulus being introduced in USA's technical standards

Calculating foundation deformation by using chord modulus is a China's self-innovation technology. It corrected the faults in compression modulus and various calculation models.,and improved the calculated result. The calculation is based on physical indicators of soil and by software; therefore it is also a simplest method. According to it the goal that to control the deformation in the foundation design specification can be reached. Also, taking region differences and micro-structure differences of soil into consideration, the software can calculate the collapse of different types of loesses considering the factors such as the footing area, foundation pressure, adjacent footing influence and so on, thus assessing the quantitative loess collapsibility. During almost the same time when the chord modulus is being researched; it is also researched in the calculation of metal material deformation in USA, which has replaced method of calculating nonlinear elastic deformation by using the Young's modulus and was then introduced in China's related specifications.These facts should give us an important inspiration for technology update to use chord modulus in code for design of building foundation. The paper is going to summarize the chord modulus and further clarify this views.