Risk Assessment For Long-span Continuous Rigid-frame Bridges During Construction Stage

With the advance of Western Development, the construction of mountain bridges obtainswidely development, especially the long-span continuous rigid frame bridge, but themountains’ geographical situation make the characteristics of bridge, such as: curve, largelongitudinal gradient, high pier, long-span. Combine these complex characteristics of bridgeand the complexity of the mountainous area, make mountains bridges face huge risk inconstruction stage. Upon this background, this paper carries out the risk analysis of long-spancontinuous rigid frame bridges in construction stages.Summarized the risk accident appear in the construction domestic and overseas, get thebasic risk factors in the bridge construction stage, analyse and distinguish the bridges’ riskevents, ascertain the main risk events influence that influence the bridge safety.Combined domestic current bridge risk research, mirrored existing risk analysis results,established the basic process of risk assessment, separately establish the risk probabilitymodel and the risk loss model, ascertain the risk synthetic evaluation model, the acceptancecriteria and the risk grade level. Put forward a method called F-R-M, combining finiteelement methods and RBF network and Monte Carlo simulation, which is used for riskprobability estimate. Classify the risk loss and solve the risk loss quantitatively; establish thegrade level based on social acceptance criteria and enterprise acceptance criteria.Using the finite element program MIDAS/Civil build the finite element model ofXiangXiHe large bridge, carry out the analysis and calculation on this bridge. Establish therisk hierarchical analysis model of XiangXiHe large bridge, ascertain the main mode of peril,get the probability value and risk loss value, use the risk synthetic evaluation model, judgerisk grade level, and then formulate corresponding risk treatment.Analyzed the cradle falling accidents and summed up the risk source of cradle falling.Analyzed the stress and displacement of bridge structure, which biggest cantilever in thenormal condition, all cradle falling and unilateral cradle falling. At each condition, get theinternal force of pier and beam consolidation, stress of biggest cantilever tip. Ascertain themost unfavorable condition, and proposed corresponding risk treatment to risk sources ofcradle falling.