Study On Damage Evolution Rule And Damage Model Of Multi-ribbed Composite Wall

Multi-ribbed composite wall structure is a new structural system, characterized by ecology, saving energy and good aseismic performance. Much progress has been achieved in previous study through a lot of systematic tests and theoretical researches on multi-ribbed composite walls. But further research on damage problems of multi-ribbed composite walls should be made, such as damage evolution of material, infilled frames and structure subject to loads in service, damage degree evaluation of walls, identify performance level of walls, control on performance damage of walls in the condition of temperature and humidity and so on. The preceding research provides effective means for determing the energy dissipation mechanism and endurance properties of this structure. Taking multi-ribbed composite wall for consideration, detailed research is made on the above contents. Main research works and productions are as follows:1. The basic mechanical performance tests of porous lightweight concrete were made for porous lightweight concrete concluding autoclaved aerated concrete and foamed concrete. Cube compression strength, prismoid compression strength, Young's modulus and stress-strain curves were obtained. Those provide reliable foundation for finite element calculation.2. The elastic-brittle-plastic damage constitutive model and multi-axis strength criterion model were presented. According to damage properties of porous lightweight concrete, four parameters strength criterion model was proposed. Elastic-brittle-plastic damage constitutive model of porous lightweight concrete was presented. The basic theory of the damage constitutive model consists of elastic-brittle-plastic of porous lightweight concrete, continuous dielectric mechanics, basic principle of irreversible thermodynamics, and four parameters strength criterion model. Finally numerical simulation using test data was made.3. The macro-damage model of fundamental element of masonry infilled frame was presented. Based on the inner mechanism of damage and energy dissipation, the rigid frame elements of damage fiber bars were presented through considering damage of material and adopting fiber bars. Elementary stiffness matrix with damage was deduced. The damage variable was defined. Damage evolution equation was presented. Then the macro-damage model of fundamental element of masonry infilled frame was presented, combined with damage elements of tension and compression diagonal braces. Macro-damage finite element analysis program MRCS-D was developed. Mechanical analysis and numerical simulation were made using MRCS-D, and damage values of each element, named local damage index (LDI) were obtained.4. General damage analysis of multi-ribbed composite walls was made, and the performance levels of damage were determined. A new damage index, named general damage index (GDI) was proposed through energy method. It is also showed that the damage evolution rule between micro-damage of material and macro-damage of structure for multi-ribbed composite walls is right. Five performance levels for damage process of multi-ribbed composite walls were determined using GDI. Meanwhile, the contribution ratios and mutual change relations of masonry, ribbed-beam and ribbed-column were calculated, for the whole process from integrated to destroyed process when multi-ribbed composite walls subjected to loads.5. The research on damage of multi-ribbed composite walls subjected to temperature and humidity field were made. The research on temperature and humidity conduction mechanism and damage mechanism were made. The elastic constitutive model of temperature and humidity damage was presented. The element finite model accorded with practical situation was presented. It is found that sharp drop of temperature and humidity was the reason of sharp raise of surface stress. Appling temperature loads on concrete surfaces and preformed cracks were economic and effective methods for controlling surface temperature cracks in the production of multi-ribbed composite walls. And it is consistent with practical situations.