Investigation On Health Monitoring For Wooden Beams Of Ancient Buildings

In recent years,the application of structural health monitoring technology in the protection of cultural relics buildings has received more and more attention from relevant domestic and foreign experts.Health monitoring will be an important part of preventive protection of ancient wooden structures.Due to the special material properties of wood and the repair principles for the protection of ancient buildings,a mature method and technology for the health monitoring of ancient wooden structures has not yet been formed,and there is a lack of calculation methods to accurately determine the dangerous points of wood members and the placement of sensors based on the size,defect status,and load conditions of the wood members,as well as a method is absent to judge the safety degree of the wood members based on the monitoring data.In this paper,it takes the wooden beams as the research object,which is one of the most important load-bearing components in ancient wooden buildings.The study specifically focuses on the health monitoring scheme of ancient wooden beams,and discusses the variation patterns of the bearing capacity of wooden beams with defects.It will lay a part of the foundation for the future establishment of the overall health monitoring system of ancient wooden structures.Firstly,the paper determined the parameters of strain(stress),moisture content,temperature,and humidity should be monitored in the evaluation of the health of wooden beams.Based on the monitoring parameters and monitoring requirements,the selection of sensors were carried out.Then,under the premise of setting the safety judgment standards of wooden beams,the Qijia-beam with the largest load and working stress in the wooden structure of ancient buildings were the object.Abaqus finite element software was used to simulate the variation patterns of the bearing capacity of wooden beams with different defects such as cracks,internal decay and holes,fractures,and to determine the location of maximum working stress of the wooden beams.According to the experiment,the correctness and reliability of the numerical simulation results were verified,which provided a basis for the placement of strain(stress)sensor and the interpretation of monitoring data.Finally,a health monitoring system for wooden beams of ancient buildings was built based on Lab VIEW software and selected sensors and other hardware.The application of the simulation monitoring of the defective wooden beams verified the practicability of the system.The paper established a method for determining the safety of wooden beams,and used Abaqus finite element software to study the impact of different defect types,different defect sizes,and different defect positions on the safety of wooden beams;According to the sizes,damage conditions,load of the wooden beams,the stress distribution of the wooden beams was numerically simulated,the placement position of the strain(stress)sensor was accurately determined,and the quantitative relationship between the measured value of the wooden beam strain and its maximum strain value was determined.The result of this study showed that numerical simulation,which could accurately determine the location and the value of maximum tensile stress of the wooden beams,it was a good method to quantitatively investigate the influence of defect on the safety of wooden beams and to determine the installation position of the strain(stress)sensor for the monitoring of wooden beams safety;It was feasible to monitor and evaluate the safety of wooden beams based on the health monitoring system for wooden beams of ancient building.