建国以来，我国城市住宅和其它民用房屋大多数是低层或多层建筑。这些建筑既不能停止使用，又急需扩大使用面积，且多数建筑在过去建造中没有进行抗震设防或者设防标准偏低。对这类建筑进行增层改造有着十分重要的理论研究意义和工程应用价值。 建筑轻钢结构增层是目前逐步被推广的一种房屋增层与改造形式，它具有自重轻、抗震性能好和施工方便等优点；在技术、经济以及安全性等方面较混凝土结构具有明显的优点，在国内逐渐获得广泛的应用，但目前设计方法也不够完善，一般只对增层部分进行设计计算。而采用轻钢结构增层后，结构的整体质量、刚度、周期、阻尼比等都发生了变化，仅对增层部分结构进行计算分析是不安全的，应进行建筑结构的整体分析。 本文在总结国内轻钢直接增层结构的形式、工程实例和研究现状的基础上，结合轻钢增层结构与既有上部结构共同作用的特点,利用有限元软件ANSYS对西安高新区某一办公楼原三层、四层钢筋混凝土框架结构分别增加一层、二层轻钢结构所组成的结构体系进行了静力和动力分析。对增层前、后结构的变形、位移等各项数据进行对比分析，分析结果表明：多层框架结构增层后，结构的应力、应变在增层楼层处变化比较明显，成为结构的薄弱层，需进行抗震验算；增层较多时，需要考虑结构高阶振型的影响。研究验证了多层框架轻钢增层的可行性，获得了轻钢增层结构的受力和变形规律，为轻钢增层结构的设计提供了理论参考。并对轻钢增层结构在实际工程应用中的一些关键性技术进行归纳和总结，从应用技术角度提出轻钢增层结构在轻型材料的采用、新旧结构的连接等施工方面的特点，并对连接部位及原结构的加固提出解决方案与建议。

Most of the urban residential and other civil buildings built before were low-rise or multi-storey. It is not economic to push down those buildings but to expand area is the urgent need; even most of these buildings are not earthquake-resistant qualified or don’t satisfy the seismic fortification criteria. So it is important to convert this building. The technique of adding stories with light-weight steel structures is gradually promoted to be a new type of structural reinforcement for its advantages of light weight, good earthquake-resistant performance and easy construction. Also, it is superior to concrete structure in aspects on technology, economy and safety, therefore this technique is widely used in China. However, the design method is not mature yet, mostly, only the load bearing capacity of adding part is considered. But, significant differences of the whole mass, stiffness, period and damping occur when adding light-weight steel structure on the original building. Therefore, it is no longer suitable of just calculating the adding part, and the analysis of the entire structure ought to be carried out. On basis of the form, case study and the present situation of research on the direct storey-addition of the light-weight steel structure and the feature of structure added by light-weight steel storey, this paper has made the static and dynamic analysis on the integral structure includes adding one or two stories light-weight steel frame on three storey, and four-storey by finite element analysis software ANSYS. The data of distortion, displacement etc. are analyzed in fore and after on added storey frame. The results show that the lower frame structure after adding light-weight steel stories, the variation of the stress and strain is obvious in the storey of adding, so it is a vulnerable one and it should be checked by the designer. When add more stories, the effect of high-order mode should be considered. In addition, it gets the rule of force and displacement about storey-adding of light-weight steel structure, and it offers theoretical reference on the design of adding storey for designer. Some critical technique in the practical application to light-weigh steel adding-storey structure is generalized, and the application of light-material and the construction feature of the connection with new structure are put forward from application technology. Then the design of connection area and reinforcement of the original structure are suggested.