Study On Seismic Performance Of Deck-type Reinforced Concrete Arch Bridge In Near-fault Area

Deck-type reinforced concrete arch bridge has become one of the main types of highway bridge types in mountainous areas in Southwest China due to its good mountain terrain adaptability and superior mechanical properties.Southwest China is a highincidence area of strong earthquakes in China.Most of the destructive earthquakes in recent decades are concentrated in this area,which brings great challenges to the service safety of bridges.Deck-type reinforced concrete arch bridges are generally thrust structures,which are very sensitive to the displacement of foundation.However,the characteristics of near-fault ground motion,such as directivity effect,hanging wall effect,and fling-step effect,often cause serious damage to the arch ring or even complete collapse,leading to the overall destruction of the bridge.The Wenchuan earthquake shows that the seismic performance of deck-type reinforced concrete arch bridges is very sensitive to near-fault ground motions.In view of these factors that the complex dynamic characteristics of this type of arch bridge,the great destruction potential of near-fault earthquakes and the lack of the actual earthquake damage and relevant researches,this paper conducts research on the seismic performance of deck-type reinforced concrete arch bridge in near-fault area.It is expected to provide reference for the seismic design and reinforcement of the same type of arch bridge in the near fault area.The main research contents and conclusions of this paper are as follows:(1)Based on the Open SEES,a full-bridge finite element analysis model considering factors such as material,geometry,and boundary nonlinearity was established.And the near-fault ground motion was used as an excitation condition to perform nonlinear timehistory analysis on the bridge,revealing the seismic response characteristics of deck-type reinforced concrete arch bridges,as well as the influence of the nonlinearity of arch ring material and the collision effect of the deck on its seismic response.Studies have shown that the maximum response of the bending moment of arch ring is located at the springing section,the maximum lateral displacement response is located at the arch crown section,and the maximum vertical displacement is between 1/4 span and 3/8 span;the bidirectional force characteristics of spandrel columns are obvious;the deck will undergo rigid displacement and rigid rotation under earthquake;the nonlinearity of the arch ring material and the collision effect of the deck have a great impact on the seismic response of the arch bridge.(2)Select typical near-fault pulse-like ground motions and near-fault non-pulse-like ground motions as excitation conditions,and conduct nonlinear time history analysis on the bridge reference model(M1)by setting three different working conditions to discuss the influence of multi-dimensional ground motion,near-fault pulse effect and vertical ground motion on the seismic response of deck-type reinforced concrete arch bridge.Studies have shown that the multi-dimensional ground motion has a certain impact on the seismic response of bridges;the impact of vertical ground motions on the seismic response of deck-type arch bridges cannot be ignored;the pulse effect has a very significant amplification effect on the seismic response of bridges.(3)Based on the IDA method and the scaling method,the nonlinear time-history analysis of the bridge is carried out by setting two different analysis conditions.And combined with the component damage analysis method,which based on the Capacity Demand Ratios(C/D),It is revealed that the seismic damage mode of deck-type reinforced concrete arch bridge and the influence of near-fault effects such as pulse effect and significant vertical ground motion on its seismic damage mode.The seismic performance of deck-type reinforced concrete arch bridge in near-fault area is studied.Studies have shown that the spandrel structure is more prone to damage than the arch ring;this type of bridge is more prone to damage subjected to near-fault pulse-like ground motion;the significant vertical ground motion characteristics of the near-fault area have little effect on the full-bridge damage mode of this type of bridge.