Capability Research On Stiffness Degradation Of Inland River Overhead Vertical Wharf Structure

After the impoundment of The Three Gorges Reservoir, which greatly improves the flow conditions of the Yangtze River Basin. High water level remains long, low water level remains short, which provides a good condition for the shipping industry. Inland river overhead vertical wharf with its maximum throughput, simple and efficient handling technology, adaptability to changes in water level and many other great advantages are being more and more widely used in the practical engineering. Now inland river overhead vertical wharf is still used in all vertical piles with vertical and horizontal contact beam below. This structure type requires a higher overall stiffness, but inland river overhead vertical wharf always works in adverse environment, subjected to a wide range of load and In the process of using the stiffness degradation is much severe. It is very necessary to study the performance of inland river overhead vertical wharf with stiffness degradation.The thesis takes practical engineering as background and uses numerical simulation method to establish a three-dimensional finite element model respectively inland river overhead vertical wharf around stiffness degradation with static analysis, modal analysis and seismic analysis to obtaining the performance characteristics change of the wharf structures while stiffness degradation. The main research contents and conclusions are as follows.(1) Taking Orchard Port, Chongqing, China as a case study. Establishing a three-dimensional finite element model, take the self-weight, cargo load, mooring force, impact force and container loading bridge load for static analysis to calculate the moment shear and axial force of each member of the wharf structure. Determine the role of the external load, the main force member of wharf structures. Combined with force transmission characteristics and the external load characteristics of each member, then qualitatively determines the inland river overhead vertical wharf during using marina: piles, columns, crossbeams, track beams, berthing member, panels and spandrel beams stiffness degradation faster, while the stiffness degradation of other components is relatively slow.(2) According to the results of static analysis, consulting component damage coefficient and damage relations between states of Standard for appraiser of reliability of civil buildings Specifying stiffness degradation factors of each member and drawing up structural stiffness degradation of the two states to established finite element model of the structure for modal analysis. The results show that modal frequency of the structure is more sensitive for stiffness degradation, and as the degradation of structural stiffness, modal frequency will decreases.(3) Chosing EI Centro seismic wave, adjusting the peak based on the seismic intensity of the port and using the adjusted acceleration of process as the input of transient dynamics analysis for seismic analysis under the three states on the wharf structure. The results show: In the process of stiffness degradation of wharf structure, the overall displacement increases with the decrease of the stiffness of the overall, internal force of structural members first increases and then decreases; further analysis learned that increasing stiffness of piles and columns of wharf structure helps improve seismic behavior of the structure, while increasing the stiffness of the upper beam structures will reduce the seismic behavior. In order to improve the seismic behavior of inland river overhead vertical wharf to meet the safety, serviceability and durability required in the circumstances, appropriate to reduce the size and number of the upper beam system to reduce the stiffness of the upper beam system.