The Failure Mechanism, Safety Evaluation And Seismic Protection Technique Of Arch Bridge In The Strong Earthquake Area

In the process of this project examines, mainly from investigate scene, data analysis and theory research, as arch substructure to the focus, as wenchuan representation arch to the research object,insist on the failure mechanism research to base,the safety assessment system research to measure,the seismic protection of new technologies to purpose for the overall research ideas, follow the principles of research practical, integrate the theoretical analysis and numerical simulation methods together, achieve structural dynamics,rock mechanics,geomorphology,engineering control Science are multidisciplinary,integration and innovation. After three years (2008 ~ 2010), made the following innovative achievements:(1)Through the basic equations of plane deflection of arch circular cross section, derived arch vertical motion dynamic parameters formula, receive longitudinal shock main factors: the length of arc,the full angle of arc,the weight of arch,the flexural stiffness of arch cross-section,the ratio of arch building weight, and analysis that factors impact on the level of arch longitudinal vibration.(2)By the equation of arch lateral bending and torsion vibration introduced the horizontal seismic forces, drawn arch lateral seismic vibration equation, and establish the corresponding simplified mechanical model, use the energy derive arch dynamic characteristics of horizontal vibration formulas. After analysis, the parameters of span ratio and the ratio of arch construction weight were two most important factors that affect transverse vibration.(3)Based on Newmark sliding block theory and Zeng and Steedman rotation theory model, establish sliding mode, rotation mode and the platform body sliding and rotational coupled vibration displacement model, according to the formula of M-O, calculate the critical sliding acceleration and the critical rotation acceleration, and finally proposed platform body vibration displacement calculation.(4)Based on Prandtl failure surface and Coulomb wedge theory equilibrium condition, conside seismic force and contact surface friction impact, use Mononobe-Okabe formula, derived ground bearing capacity formula under earthquake, and which can safety assessment soil strength reduced.(5)According to the Mises flow rule, get abutment slope strain rate and sliding surface and line angle under earthquake, under which come to work that force acting on slope and energy that plastic flow consume, according to the principles of external forces acting and internal consumption of energy equivalent, ultimately derive the greatest seismic active earth pressure and its corresponding slip surface angle.(6)Using the finite element MIDAS/Civil7.0 analyzed arch bridge,the main arch and foundation that unstable failure mechanism, found stress concentration and displacement mutation in the top sides of abutment,the arch vault to 1/4 of the surface and bridge turning point.(7)Based on the principles of safety evaluation index constructing in the earthquake zone, according to the characteristics of earthquake areas arch, establish safety evaluation index system and quantitative methods, use calculating method and fuzzy comprehensive evaluation were coupling, establish and calculate arch safety assessment system.The results has certain fixed reference value and significance for pre-earthquake zone protection and post-arch bridge.(8)For arch whole and local security states in the earthquake area, focus on to substructure and foundation, research and develope expansion pile compression reinforcement in liquefied foundation,abutment reinforced by the anchor prestressed self-balancing,abutment strengthening technology by contains support, and establish corresponding calculation methods,design methods and construction methods.