Study On The Seismic Performance Of Embedded Steel Cylinder Breakwater Based On The Displacement

Embedded steel cylinder structure had strong adaptability,short construction period and high safety,and it was suitable for deep water area.Embedded steel cylinder quay wall was widely applied in the world at present,and embedded steel cylinder breakwater was not widely applied in the world.Seismic performance index of embedded steel cylinder breakwater was defined according to seismic design thought of seismic design guidelines for port structures(PIANC 2001).Meanwhile,the dynamic response and the deformation mechanism of breakwater for the port in Venezuela before and after foundation reinforcement were studied by shaking table test and the numerical simulation.The seismic performance of breakwater was evaluated based on the displacement.In the end,affecting of the major factors for seismic performance of the breakwater was analyzed.The main works and conclusions are as follows:(1)Based on seismic design guidelines for port structures(PIANC 2001),the statistical results of seismic damage for port structures in Japan,and the characteristics of steel cylinder structure,normalized residual horizontal displacement of embedded steel cylinder breakwater is identified as seismic performance index.The damage degree is divided into four grades of Serviceable(?),Repairable(?),Near collapse(?),and Collapse(?),and the seismic performance of breakwater can be evaluated by normalized residual horizontal displacement for embedded steel cylinder breakwater.(2)The influence on the dynamic response of embedded steel cylinder breakwater in the backfilled sand foundation for the port of Venezuela is analyzed according to numerical simulation.It is found that the far-field seismic has a greater impact on the horizontal residual displacement of the breakwater than the near-field seismic waves with the increase of the peak ground acceleration.It is suggested that the effect of far-field and near-field seismic is considered in the design of seismic performance for breakwater.At the same time,numerical simulation shows that the stress of the bottom of the steel tube and the mud surface is larger,and it is a weak link of the structure.It can provide a reference for engineering design.(3)Stiffness of backfill sand outside cylinder plays a key role in the stability of embedded steel cylinder breakwater for the port of Venezuela and it is advised that backfill sand outside the cylinder should be considered in the process of design for foundation reinforcement.The seismic performance grade of the breakwater before the foundation reinforcement at Level 1 is grade S,the seismic performance grade at Level 2 is grade A,which is not satisfied with the requirement of the seismic performance.The seismic performance grades of the breakwater after the foundation reinforcement at Level 1 and Level 2 are all grade S,which meet the design requirements of the seismic performance.The reasonable range of foundation reinforcement for backfill sand outside the cylinder is determined.(4)The deformation mode of embedded steel cylinder breakwater is mainly determined by the steel cylinder structure and the foundation conditions.As the bottom sand of the breakwater is dense fine sand,the breakwater is dominated by horizontal movement.The horizontal displacement is larger by reason of the change of the lateral force due to liquefaction before foundation reinforcement,and the horizontal displacement is small after foundation reinforcement.The deformation mechanism of embedded steel cylinder breakwater is verified by the shaking table test and numerical simulation.(5)The influence on the seismic performance for embedded steel cylinder breakwater of embedded length,diameter height ratio,internal friction angle of sand outside cylinder and internal friction angle of sand inside cylinder is analyzed by numerical simulation.It is found that embedded length,diameter height ratio,internal friction angle of sand outside cylinder have great influence on the seismic performance of the breakwater,and internal friction angle of sand inside cylinder has low influence.At the same time,it is found that the order of the seismic performance for the breakwater from large to small is diameter height ratio,embedded length,internal friction angle of sand outside cylinder and internal friction angle of sand inside cylinder through the orthogonal test.