The Research On Health Monitoring And Safety Evaluation Methods For Spatial Grid Structures

As a new type of structure system, space grid structure has been rapidly developing for nearly thirty years at home and abroad, and is more and more widely used in all kinds of public architecture. It represents the level of building technology of a country or region. However, safety hidden trouble also exist, safety accident analysis shows that it has become the focus of attention and an urgent task to establish a set of safety appraisal methods and standards for spatial grid structure. The current safety assessment methods mostly focus on existing masonry or concrete structures, few papers or research references concerning the safety assessment of the space grid structures have been found, and a lot of respects are hardly touched on. In view of these, according to the national natural science foundation research subject of‘Research on Damage Mechanism of the Spatial Dome-Reinforced Concrete Structures and Reduce Vibration System in West Area’(51068019), based on the analysis of spatial grid structure damage mechanism and through theoretical analysis, numerical simulations and example demonstration, the damage identification and safety evaluation method about the spatial grid structure are studied in this dissertation.The main content of the dissertation are as follows:(1) Through the analysis of the existing space grid structure characteristics, types of injury and destroying forms, its safety control mathematic model and its safety control object and methods were given;(2) Through the analysis of existing sensor placement method, structural internal force distribution, structure damage characteristic and structural health monitoring work mode, sensor placement methods, damage parameter and recognition method were put forward for space grid structure;(3) The calculation model between components cross-sectional and structure load factor was established for the different types of space grid structure, weight index calculation model for space grid structure was identified, and weight distribution plan and quantization standard between structure stability and structural components (including nodes) were also given;(4) Based on FUZZY mathematics comprehensive evaluation principle, the study of the membership function and weight index, the comprehensive evaluation mathematical model and evaluation index treatment methods, In the light of the spatial grid structure characteristics, its safety assessment procedure, its evaluation grade criterion and comprehensive evaluation method were put forward.The research result shows that follows:(1) Structure load model and load effect combination for structural safety evaluation shall conform to requirements of the current structure design codes,geometric parameters and calculation model are the main factors that influence structural resistance model;(2) Structure security involves the control of structural rods, node and structural stability, with the current specification being their calculating standards, the component internal force being control parameter for structure rods(including nodes) ,and the structure bearing capacity being control parameter for structure stability respectively;(3) Sensor reasonable placements for structure and rods based on damage identification can be realized by means of static strain analysis method and effective nodal method based on the principle of kinetic energy respectively;(4) the damage location and degree of spatial grid structure bar element can be determined by means of strain difference value before and after rods damage, the rods node location and damage degree can be recognized if connected domain area is regarded as variable and the rods internal force change as damage parameter, the whole structural damage degree can be identified if the ratio of the product of nodal displacements and the bearing capacity before and after structure damage is regarded as damage parameter; (5) It is found that effective precautionary measures during the sensor installation and operation, intelligent degree of health monitoring system, and comprehensive utilization of traditional testing method and modern sensing technology are basic method to improve structural damage identification accuracy and safety evaluation effect.Through system monitoring and safety evaluation of large-scale complicated dome structure of Qing yang Stadium, Gansu province and K6 single-layer shell test model, damage identification and safety assessment methods proposed in this dissertation are verified, and they are convenient and effective for space grid structure.