Hybrid Testing Of Frame Structures Based On Model Updating Of Sectional Yield Surface

Hybrid testing, which combines the advantages of numerical computation and physical experiment, is an effective method to evaluate the dynamic response of structures. It is potential in assessing the seismic performance of large scale structures with the help of substructuring technique. However, there are some model errors in substructure hybrid testing. One model error is derived from discteting the prototype structure in too simple computational model and rough numerical elements, e.g. story shear model and constitutive models in member level are used to represent frame structures. The other model error is resulted from the parameter uncertainty of the assumed model in numerical substurctrues, e.g. the members which undergo nonlinearity but can not be tested experimentally will be represented by assumed numerical models. The advantage of substructure hybrid testing will be eclipsed if the whole structure is dominated by numerical substructure s.To reduce the two model errors in hybrid testing, it is necessary to adopt proper computational model and refined numerical element. Besides, the measured data of experimental substructure can and should be used to identify the parameters of the predefined numerical model, then the identified parameters can be used to calibrate the corresponding model in numerical substructure during hybrid testing. Hybrid testing system based on finite elemnt software and model updating framework is studied to provide technical supports for the two strategies above.This study focus on reducing model errors in hybrid testing of frame structure s, thus, hybrid testing with online sectional model updating is proposed. The main work and conclusions are as follows:(1) The sectional constitutive model account for axial-flexural interaction is proposed for beam-column element. The sectional yield surface of axial force and bending moment is formed based on section assembly concept, and the sectional constitutive model is built according to the classical plastic theory. Section state determination and constitutive relation integration are discussed for the application of the sectional constitutive model. A nonlinear finite element software based on MATLAB is developed. Numerical simulation show that: the sectional constitutive model not only can account for the influence of axial force on the bending capacity, but also features with kinematic, isotrophic and mixed hardending. Besices, the sectional constitutive model can balance both computation accuracy and efficiency.(2) The parameter identification method of the sectional constitutive model for beam-column elements is proposed. A frame column is taken as the system to be identified, the nodal displacements and forces of the column in basic coordinate system are chosen as the inputs and outputs, and force based element with sectional constitutive law is adoped as the numerical model of the column. UKF is employed as identification algorithm in parameter estimation and joint estimation forms. The performance of UKF Pure parameter estimate with respect to the initial value and noise of the filter are analized. Besides, the identification with and without model errors using both Pure parameter estimation and Joint UKF estimatio n are discussed. The results show that the identification method is robust, accurate and efficient.(3) Hybrid tesing framework with online model updating based on fin ite element software is estimated. The problem associated with two-loop hybrid testing system is analized and a simulation platform for hybrid testing system is built. The three-loop hybrid testing framework based on finite element is studied, in which the communication between MALAB finite element and middle loop d SPACE is summarized, besides, the functions of the d SPACE are extended to include commands generating and boundary conditions controlling. The framework of hybrid testing with online model updating for frame structures is proposed. Numerical simulation and hytrid testing have shown that the platform of simulation and the framework of testing are feasible and effective.(4) Hybrid testing of frame structure with and without online modeling updating are carried out. Plan steel frames are taken as the target structure and considered as bar-system model, the methods for static and dynamic analysis are specified. A full scale frame column is designed as the specimen and loaded by three-actuator experimental setup, the measurement layout is also introduced. The conventional hybrid testing and the hybrid testing with online model updating are conducted. The results show that the boundary condiction of a plan column can be realized by three-experimental setup, the advantage of conventional hybrid testing is not obvious for large scale frame structrues, while the hybrid testing with online model updating can greatly improve the accuracy of testing results.