Analysis And Application Of Plastic Damage Response Of Combined Dam Structure Under Oblique Incidence Of Near-fault Ground Motions

There are abundant water resources in the meizoseismal area in southwest China.Some of the high dams that have been built,under construction and planned are located near the seismic fault zone,which are influenced by the complicated rules of near-fault ground motions.At present,most of the studies assume that the near-fault ground motions propagate along a vertical direction,and the incident angle of earthquake waves are neglected.Besides,in recent years,heterogeneous concrete combined dam structures have become a trend,its deformation coordination problems have been widely concerned,and the dynamic response of structures under complex seismic waves needs to be studied.Based on the structure-soil interaction and the basic finite element theory,this paper analyzes the dynamic response of a CC-RCC combined dam structure in southwest China under the near-fault obliquely incident seismic waves.The main research work and conclusions are as follows:(1)According to the wave equations corresponding to different scattering waves,the calculation formulas of each parameter of the 3D viscous-spring boundary are derived.The viscous-spring boundaries are applied through the secondary development of ABAQUS.Combining on the viscous-spring boundaries,the formulations of the equivalent nodal forces are derived.Then the equivalent nodal forces of the boundaries under oblique incidence of P waves and SV waves are deduced respectively.Finally,the displacements of the midpoint on the free surface in the semi-infinite space are verified,which proves the validity and precision of the methods.(2)According to the characteristics of different materials and contact relations between them,a 3D finite element model of the CC-RCC combined dam structure is established.The Concrete Damaged Plasticity model is used for the dynamic analysis,and the viscous-spring artificial boundaries are adopted as the foundation constraint.Based on the dam site conditions and the characteristics of near-fault ground motions,three groups of near-fault pulse earthquakes are selected,and three corresponding nonpulse earthquakes are fitted by their response spectra.The six groups of near-fault ground motions are used as a dynamic load for subsequent calculations.(3)Taking near-fault plane P waves and SV waves with an oblique incidence as examples,the dynamic analysis of the dam body is carried out.The results indicate that:a)The near-fault pulse earthquakes are more destructive than the non-pulsed ones;the dynamic response of the dam body increases with the ratio of PGV/PGA.b)The damage of the dam body first increases and then decreases with the incidence angle of P waves,and reaches the maximum when the angle is 60° or 75°.The damage of the dam body decreases with the incidence angle of SV waves,and generally reaches the maximum when the angle is 0°.c)The relative displacements between the dam crest and the different parts of the foundation are different,which proves the necessity of considering the structure-soil interaction.d)The worst damage of the dam body occurs at the interface between different materials,the inflection point of the dam,and the dam longitudinal seam.e)The law of the influence of the pulse effect of near-fault ground motions and the incident angle of earthquake waves is complex,which should be considered comprehensively.The above research results and conclusions can provide technical support for the dynamic analysis of heterogeneous concrete combined dam structures under complex ground motions.