Research On Integrated Intelligent System Of Health Monitoring And Damage Diagnosis For Long-Span Truss Structure

The current structural health monitoring(SHM)system exists the problem that the health monitoring and damage diagnosis subsystems are unrelated to each other,which leads to the low usage of the SHM system.This paper proposes to build an advanced structural health monitoring system,by integrating the two unrelated subsystems.The monitoring information required by the diagnosis system is determined based on the structural damage feature,the layout position and working mechanism of the intelligent sensors with event-driven sensing capability are determined using the monitoring information.Taking the Yangtze River International Conference Center as the engineering background and the long-span truss structure as the analysis object,a numerical model that meets the requirements of structural damage feature analysis is firstly established.Then the key vulnerable components and vulnerable parts of the structure are determined based on the analysis methods of structural vulnerable parts.Then the structural damage feature information during the service process is acquired by simulating different damage states of the structure.Finally the layout and working mechanism of the intelligent sensors are determined based on the analyzed results of structural damage feature information,which provides an implementation idea for the construction of an integrated intelligent system of health monitoring and damage diagnosis for long-span truss structures.The main research and conclusions of this paper are listed as following:1)A numerical analysis model of long-span truss structure for the design of integrated intelligent system of health monitoring and damage diagnosis is established.Ⅰ)Based on the damage detection report of existing truss structure and the post-disaster investigation results of enclosure structure,two types of damage in the long-span truss structure are summarized,namely the damage of main structure dominated by macroscopic cracks and of enclosure structure dominated by distributed microscopic defects.Ⅱ)In order to analyze the damage feature of main structure dominated by macroscopic crack,a single-scale overall structural model and a multi-scale structural model including vulnerable parts are established in turn,the multi-scale model is modified using the measured data based on the response surface method,and the rationality of the structural model with cracked component is verified.The results show that the relative error of structural response obtained by modified model and measured test is within 10%,and the relative error of stress intensity factor obtained by the numerical model and analytical formula is at most 5.44%.It indicates that the established multi-scale analytical models of main structure are credible.Ⅲ)In order to analyze the damage feature of enclosure structure dominated by distributed microscopic defects,a simplified analytical model of the standing seam metal roof and a numerical model of wind load which leads to the deterioration of bearing capability of enclosure structure are established,the correctness of metal roof model is verified by the test data.The results show that the relative error of ultimate wind obtained by metal roof model and test data is 8.59%,the simulated z-direction deflection and lateral stress are basically the same as the test data,and the errors are within the acceptable range.It indicates that the metal roof model can meet the analysis requirements.2)Aiming at the main structure with numerous components,this paper proposes an identification method of key vulnerable components based on the analysis of importance and vulnerability.The components with more importance and vulnerability in the structure are selected with overall structural model.By analyzing the stress distribution of key vulnerable components under the most unfavorable load of main structure,it is determined that the vulnerable part of main structure exists at the weld toe of intersecting weld.Aiming at the enclosure structure with huge spatial size,this paper proposes an identification method of vulnerable part of structure based on the wind-induced fatigue damage analysis.By calculating the fatigue damage increment at any position of the enclosure structure caused by the standard cyclic block of wind pressure,it is determined that the vulnerable parts of enclosure structure are distributed at the central position of the ridge and the cantilever end near the structural central axis.3)By updating the crack size at the vulnerable part of main structure and reducing the stiffness of roof panel at the vulnerable part of enclosure structure,different damage states of main structure and enclosure structure are simulated.Based on the analysis of structural response variation,the acquisition locations of response information that can characterize the structural damage evolution process are determined.The relationship between the relative changes of structural responses and damage states is analyzed,and the degradation law of wind-resistant bearing capacity of enclosure structure is explored.The results show that: at the acquisition location of response information,the relative change amplitude of structural responses all present a nonlinear increasing trend in the process of damage evolution,and the relative changes of different types of responses due to damage have an order of magnitude difference.The wind-resistant bearing capacity of enclosure structure shows a linear decreasing trend in the process of damage evolution,and the relationship between the wind-resistant bearing capacity and the damage state can be expressed by a linear equation.4)Based on the analysis results of structural vulnerable parts and damage feature information,the layout and working mechanism of the intelligent sensors for monitoring environmental information and structural responses are determined.The overall temperature change of the main structure and the information of wind field suffered by the enclosure structure can be obtained by the deployed single-physical quantity monitoring sensors.The deployed multi-physical quantity monitoring sensors can ensure the identification of local cracking of the main structure and the fatigue damage evolution of the enclosure structure,while reducing the recording of useless data.