Finite element model updating for large span spatial steel structure considering uncertainties

In order to establish the baseline finite element model for structural health monitoring,a new method of model updating was proposed after analyzing the uncertainties of measured data and the error of finite element model.In the new method,the finite element model was replaced by the multi-output support vector regression machine(MSVR).The interval variables of the measured frequency were sampled by Latin hypercube sampling method.The samples of frequency were regarded as the inputs of the trained MSVR.The outputs of MSVR were the target values of design parameters.The steel structure of National Aquatic Center for Beijing Olympic Games was introduced as a case for finite element model updating.The results show that the proposed method can avoid solving the problem of complicated calculation.Both the estimated values and associated uncertainties of the structure parameters can be obtained by the method.The static and dynamic characteristics of the updated finite element model are in good agreement with the measured data.

The mechanical response of multi-tower continuous-span suspension bridge deck pavement based on whole bridge analysis

The effect of multiple span suspension structure on the mechanical response of bridge deck pavement was studied, and finite element analysis (FEM) of stress and strain of pavement according to the bridge floor system features of super-long and high flexibility was made. Meanwhile, the FEM results were compared with those of the single span suspension structure. Three-stage analytic hierarchy process (AHP) is developed to analyze the mechanical response including whole bridge analysis, partial beams section analysis and orthotropic plate analysis. The most unfavorable load position was determined by the numerical solutions acquired from each stage to study the main mechanical index of multiple span suspension structure. The FEM results showed that the mechanical response numerical solutions by using the three-stage AHP are greater than those by simplified boundary condition, and the force condition of multiple span suspension structure is worse than that of the single span suspension structure.

Software Practicalization for Analysis of Wind-Induced Vibrations of Large Span Roof Structures

Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on large span roof structures (LSRS) requires large amounts of calculations. Due to the com- bined effects of horizontal and vertical winds, the wind-induced vibrations of LSRS are analyzed in this pa- per with the frequency domain method as the first application of method for the analysis of the wind re- sponse of LSRS. A program is developed to analyze the wind-induced vibrations due to a combination of wind vibration modes. The program, which predicts the wind vibration coefficient and the wind pressure act- ing on the LSRS, interfaces with other finite element software to facilitate analysis of wind loads in the de- sign of LSRS. The effectiveness and accuracy of the frequency domain method have been verified by nu- merical analyses of practical projects.

Several issues to be considered for long-term better behavior of concrete gravity dams

Along with economic,social quick development and urbanization,dams and reservoirs are of strategic importance for flood control,water supply,electricity production,irrigation,etc.,both for developed countries and for developing countries.Climate change is a new challenging issue to be considered which will speed up the development of hydropower in developing countries.More and more attention will be paid on the long-term better behavior of dams to guarantee the safety of the people involved and the better development of the world.There are about 50000 old dams in the world and a lot of them have been completed and operated for more than 50 years.However,how do we evaluate the dams’safety?How do we make the decision to do rehabilitation work or to rebuild a new dam based on evaluation results?The life span and the real safety status of old dams becomes a challenging task for the dam society,especially for China because it has more than 6000 dams to be evaluated and rehabilitated within the next few years.Based on the investigation of the Fengman gravity dam,which is 91.7 m high,operated since 1943 and suffered uplift pressure,freeze and thaw problems,etc.,discussions on the life span evaluation of old concrete gravity dams have been made.The reasonable coefficient of dam safety has been discussed.The social decision for the final choice after comprehensive studies has been introduced.