Study On Temperature And Desiccation Fissure's Producing Mechanism Of Light-weight Filled Wall Frame

Development prospects of light weight-block infill wall are very wide as it has a series of advantages such as light weight, environmental protection and so on. However, when it is extended and applied, all kinds of problem of fissure appear easily. The appearance of building and use functions are influenced. The problem of fissure in framework-infill wall restricts seriously the wide application of new type-energy saving-wall material. So it is necessary to study and analyze fissure's producing and developing in framework-infill wall more. The main purpose of this paper is to study on temperature and desiccation fissure's producing mechanism of light-weight filled wall frame.Firstly, characters and types of fissure in framework-infill wall were summarized based on wide investigation and research and the test of fissure width and depth on wall. By reading lots of references and investigating practical engineering, the reasons are analyzed initially. The fissure's producing causes of light-weight filled wall frame were analyzed combining fissure conditions in actual engineering. There are two types: one is the changes of temperature, and the other is desiccation of block. Inherent stress is produced in infill wall because of lots of factors. It is produced at the beginning and always changes, and lager inherent stress is formatted in weaker region of wall in the process of change. When this inherent stress is larger than tensile strength of wall's material here, fissure is produced. Stress is more centralized in the weaker region such as the boundary of wall, so it is more sensitive to every kind of factors. In addition, the larger value of drying shrinkage of light weight block and mortar is the inherent factor of fissure. The crack resistance of block is smaller because of the tensile and shear strength of block and the bonding strength between mortar and block are lower.This paper used ANSYS to calculate the principal tensile stress and displacement of walls which is different dimension and material. The solutions are got by analyzing the results of calculation: (1) The principal tensile stress in the bottom and top floor of wall is larger, and it becomes smaller to center of building. It is mostly symmetrical distribution along medial axis of wall and extreme value at the four corners of wall. (2) The discrepancy of principal tensile stress between framework-infill walls that is made of different wall material. It is related to shrinkage, coefficient of linear and elastic modulus. The shrinkage is larger, the fissure of wall appears more easily; the coefficient of linear is larger, the stress of temperature is larger; The elastic modulus is larger, the stress of wall is larger. (3) The displacement along the length direction of wall becomes larger from center to end. And the displacement of wall increases along highness direction of wall. The wideness of wall influences X-displacement and Y-displacement very small, and the highness of wall influences Y-displacement larger.At last, some control measures of wall-filled frame's fissure were put forward according to study results and practical engineering from choice of wall material, design method of architecture and structure, sturctue and constryction measure and so on.