Research On The Constructing Monitoring Method And Its Engineering Application For The Concrete-Filled Steel Tubular Arch Bridge

Concrete-filled steel tubular (CFST) structure, getting developed recently in China, is a new kind of technology applied to the engineering project of the long-span arch bridge. This structural model of bridge is of the characteristics of high strength, large stiffness, light weight, simple shape, long span, and short construction period. It provides practical solutions to such problems as how to use the materials economically, simplify the construction method, and improve the loading capacity. It is a favorable model for the long-span arch bridge structure. For the construction of the long-span arch bridge with the CFST structure, the key technologies are control method, optimization of cable force during assembling the steel tubular arch rib, concrete creep effect, and the control of wind-induced vibration during the construction. The researches are focused on the key technologies mentioned above for the construction of CFST long-span arch bridge in this thesis.1. The control and optimization methods are investigated for the cable force during the bridge construction. The calculated results are exactly by using the mechanical theory for the steel tubular arch because of its material being homogenous. The differences between the calculated values and the observed values are selected as the data sequence, and the gray control model is established to realize the control error. The quadratic sum of pre-elevation value of arch rib is selected as the object function. The constraint conditions are the safety factor of the cable tension, the control section of steel tube, and the height mark of the control point. The nonlinear optimizing model is established finally. The cable tension and the quadratic sum of the pre-elevation value(s) can be calculated by using the genetic and iterative optimal algorithm. The optimization of adjusting cable tension can be realized just in one time.2. The control technology of the wind-induced vibration of the uncompleted structure during the construction is investigated. The uncompleted structure of CFST long-span arch bridge during the construction of arch ribs is the investigated object. The vibrating models of the bridge surface and the arch ribs under the effect of the pulse wind are established based on the Scanlan theory. The effects of the initial angle of wind and the rotation of the bridge surface are considered in the model. The wind resistance coming from different directions is considered only in the model because of the characteristics of the section shape of arch ribs. Investigations show that the observed vertical displacements of different points on the arch rib are close when the wind load is exerted in the form of static force. But the horizontal displacements are quite difference.3. The concrete creep effect of the arch ribs is investigated. The comparisons and summarizations are carried out systematically for the corresponding calculation theory of concrete creep and the calculating model of creep coefficient. The concepts of concrete basic creep and envelope creep effect factors are proposed respectively. The calculating model for the concrete creep factor and the calculating method for the concrete creep are proposed. The calculating model and calculating method are suitable to the circumstances, stress and working condition inside the steel tubular arch. The concrete envelope creep effect factor of the CFST arch is obtained by using the data both from the finite element analysis and the observations. Based on the stress comparisons in the steel tubular under the conditions of non concrete-filled and concrete-filled respectively, the influence degrees of the concrete creep can be analyzed at different control cross-section. This research provides a practical reference for the calculation of the concrete creep effect in the designing of the CFST arch bridge.