Research On Seismic Performance And Resilience Of Inland River Overhead Vertical Frame Freight Wharf In High Intensity Reservoir Areas

The construction of inland river wharves plays an important role in water transportation and even economic development of China.As a key transportation network,wharf structure is the basic condition to ensure the transfer of land and water transportation.However,due to fewer ports in high intensity areas in Western China,there are few studies on seismic performance and resilience of wharvess.Compared with other countries such as USA,Japan and other industries in China,seismic research of water transport projects in China is relatively backward,which inevitably increases the potential earthquake risk of inland river wharves in high intensity areas.In addition,the existing port seismic research mainly focuses on the wharf structure on soft clay foundation along the coast,while the seismic research on the inland river overhead vertical frame wharf structure is relatively few.Therefore,this paper adopts the methods of literature research,theoretical analysis and numerical simulation to study the seismic performance and resilience of inland river overhead vertical frame freight wharf in high intensity reservoir area,taking a wharf construction project in Baihetan Hydropower Station reservoir area as background,which has important theoretical significance and engineering application value.The main research contents and conclusions of this paper are as follows:(1)Based on the soil parameters obtained from field tests,the finite element model is established and the pile-soil interaction mechanism in the soil-rock mixture foundation is analyzed by numerical simulation.Starting from the relationship between the horizontal soil resistance around the pile and the horizontal displacement of the pile body,the influence of soil equivalent dynamic shear modulus on the initial stiffness of p-y curve and the horizontal ultimate soil resistance is analyzed.In view of the shortcomings of Reese model and considering the influence of cohesion and internal friction angle on soil strength,the calculation expression of horizontal limit soil resistance is derived.By using Davidenkov function,a p-y curve model of single pile in soil-rock mixture foundation is established,and the model parameters are correlated with the equivalent dynamic shear modulus of soil to consider the influence of earthquake-induced weakening of soil-rock mixture foundation modulus on pile-soil interaction.The rationality and applicability of the model are verified by comparing the calculation results of the model with finite element numerical simulation and field test results.(2)The fine finite element model of wharf structure is established by Open Sees software,in which the beam-column members of pile foundation and upper frame structure are simulated by fiber element,and the pile-soil interaction is simulated by py curve of single pile on soil-rock mixture foundation established in this paper.The seismic response of the wharf structure under different earthquake intensities is calculated and analyzed,and the seismic response characteristics of the overhead vertical frame freight wharf are revealed.According to the relevant seismic design codes in China and USA as well as the results of static pushover analysis,the seismic performance indexes of the overhead vertical frame structure and the high-piled foundation on the wharf are determined.According to the performance-based seismic theory,the seismic performance of the wharf structure is evaluated according to different performance levels of the wharf structure.The results show that according to the performance-based design method,the seismic performance of the overhead vertical frame wharf structure meets the corresponding seismic action requirements and can better reflect the effect of earthquake on the wharf structure.(3)According to the seismic safety evaluation report of the wharf site and considering the randomness of earthquake action,three artificial seismic waves based on endurance time method are generated.Seismic response analysis of refined finite element model of wharf structure is carried out by endurance time method,and engineering demand parameters of upper frame structure and high pile foundation are determined according to structural characteristics of overhead vertical frame wharf.The calculation results show that the seismic response of the wharf structure gradually increases with the lapse of seismic time,which conforms to the definition and requirements of endurance time method and is in good agreement with the performance calculation results.According to the determined seismic performance demand index,the probability that the upper frame structure and the high pile foundation of the wharf will reach different limit states and different upper limits of damage states under given peak ground acceleration is calculated respectively,and the seismic fragility curve of the overhead vertical frame wharf structure is plotted accordingly.(4)Using the seismic fragility curves of the wharf structure,the structural functional losses under different earthquake intensities are calculated.Based on the existing research results at home and abroad,assuming that the functional recovery time of the structure is linearly related to the functional loss,three functional recovery models are used for post-earthquake repair of the wharf structure,and the seismic resilience of the wharf structure under different earthquake intensities is calculated when three functional recovery models are used.The results show that the seismic resilience of the wharf structure decreases gradually with the increase of ground motion strength.The exponential function recovery function has the most remarkable effect in structural repair.The function of the structure can quickly restore to the pre-earthquake state level in a short time after the earthquake.The seismic resilience of the structure under one earthquake is essentially the average value of the normalized functional function of the structure in the recovery time.Therefore,the seismic resilience of the wharf structure using the linear recovery model and the triangular function recovery model are identical.With the increase of ground motion intensity,when the exponential recovery model is used,the magnitude and gradient of reduction in seismic resilience of the structure are smaller than those of the other two recovery models,and the seismic resilience of the structure under the same intensity earthquake is larger.