Research On Deformation Monitoring Technology And Life Evaluation Method For Ancient Wood Structures

Ancient wood structure(AWS)is one of the ancient structural types with a long history,which has a number of advantages,such as excelent anti-seismic capability and good durability.Due to the impact of long-term environmental corrosion and operating load,an increasingly number of ancient wood structures are under going variable degrees of deformation,and some are even collapsing finally.Therefore,condition monitoring is an effective way to prevent from failing of AWS.However,there are some drawbacks in the current deformation monitoring technologys(DMT).For instance,some are expensive and unable to conduct real-time monitoring,as well as it is complex to implement the integration and processing of monitoring data.Furthermore,there exist less data processing methods and life evaluation methods(LEM)for condition monitoring of AWS.Consequently,the monitoring of deformation based on fiber bragg grating(FBG)strain measurement is conducted to reveal long-term deformation regulation of AWS.Then,LEM considering bearing capacity and deformation values is proposed to predict the residual life of AWS,which can proivde suggestions for repair work of AWS.The main works and results are summarized as follows:(1)This thesis studies on the deformation monitoring technology of AWS and proposes a new DMT of ancient wood beam and column based on FBG strain measurement.More specifically,the deflection of beam and inclination angle of column can be obtained through strain measurement by adopting the proposed method.Therefore,the propsed method not only can calculate the deformation values of multiple components by single sensor but also has the advantages of low cost,aesthetics,convenient and other characteristics.The results of both the finite element simulation and experimental study show that the proposed method has excellent accuracy and feasibility as well as higher applicability compared with other method in AWS.(2)This thesis presents a method to predict the residual life of AWS.Generally speaking,considering the influence of long-term corrosion on ancient wood components' mechanical properties,the thesis firstly studies the effect of component discreteness on structural cross-sectional area,strength,elasticity modulus and other structural paremeter.And then a residual life evaluation method,based on bearing capacity and deformation values,is proposed.The result shows that 1)the bearing capacity declined rapidly as corrosion time increasing.By the contrast,the deformation value of AWS will increase fastly;2)furthermore,the improved Gerhards cumulative damage formula and Weibull model are able to effectually predict and fit the residual life of the ancient wood structure.(3)As an engineering background,"Seven Family Building",one of China historic cultural folk houses,is developed and installed a condition monitonring system.Whereby the measured reponses were acquired,conbined with the in situ loading test,the feasibility and efficiency are validated for the proposed deformation monitoring technology.The result shows that the developed deformation monitoring technique and condition monitoring system are efficient.(4)This thesis develops a whole finite element model of "Seven Family Building",and the model is updated by the in-site loading test and measured data from condition monitoring system.Combined with the proposed forecast method of evaluating the residual life,the AWS,i.e."Seven Family Building",is performed the assessment on the residual life.This work not noly validates the proposed theory,but also realises forecast the residual life of AWS in service.It provides the experimental data and technical support for the repairing of AWS in the future.