| In recent years, the continuous rigid bridge with its unique advantages in the mountainous highway construction is more popular, whether it is design or construction process structures have been an unprecedented development, but also to the construction process unprecedented risk. In order to reduce construction jobs risk and loss control to the minimum range of risk, the scientific and effective evaluation for mountain bridge construction period is particularly urgent. In this paper, taking the continuous rigid frame bridge construction risk as the object of study, based on a comprehensive analysis of the cantilever prestressed concrete continuous rigid frame bridge beam characteristics and construction technology, combined with the risk assessment theory, established the "Construction Risk Assessment of Continuous Rigid Frame Bridge based on Efficacy Coefficient Method ", this system includes risk static assessment and risk dynamic assessment. This paper focuses on the risk assessment study of static. The main contents are as follows:1)Risk static assessment is that according to construction drawing design and construction organization design and other documents before the construction. First,analyzing common risk sources and specific risk sources of the nine sub-project, and to determine each risk source(upper risk indicators) underlying risk indicators. Here to introduce the theory of efficacy coefficient method, and obtain the individual risk index efficacy coefficient values by using power function for quantifying underlying risk indicators. Secondly, using AHP to determine the weight of each layer, scale method using pairwise comparison judgment matrix, and borrowing mathematical software Matrix Laboratory to finish consistency test. The normalized eigenvector of largest eigenvalues of judgment matrix is needed right weight. Finally, starting from the underlying individual risk index efficacy coefficient values and their weighting coefficients synthesized whole bridge project to assess the overall effectiveness of the static coefficient. And to determine the risk level of the bridge construction,when the bridge project to assess the overall effectiveness of the static coefficient values greater than 80, the risk level to level III(high risk), in addition to developing the necessary risk control measures should be dynamic risk assessment.2) Risk dynamic assessment is to evaluate the construction process bridgeproject. Regard the dynamic data of the construction process as the risk indicator variables. Calculate timely and dynamic the individual risk indicators efficiency coefficient. Then grasp the real-time status quickly to prevent the construction risk.Promote dynamic risk assessment is not only a means of assessing more of a risk control measures. This paper focuses on the various segments of the main beam cantilever casting works. Selected segments of deflection and stress increment error as the risk indicator variables. Midas software simulation derived by calculating the value, and then calculated the incremental efficacy segment deflection coefficient by the power function, which promptly monitors risk profile of the main beam cantilever casting work. When the incremental efficacy segment deflection coefficient greater than 80 released a high risk,it is warning time to do construction risk prevention and emergency measures.3)In order to verify the feasibility of the establishment of evaluation method,this paper uses evaluation methods recommended by "Highway Bridge and Tunnel Construction Safety Risk Assessment guidelines" and the "Construction Risk Assessment System of Continuous Rigid Frame Bridge based on Efficacy Coefficient method" for risk assessment on Dadu River Bridge. The former concludeds the overall risk of the Dadu River Bridge construction value is 13 points(high risk), special risk assessment of major risk source: cantilever construction method job, hand-dug pile, pier construction, scaffold law pouring operations,excavation construction risk ratings are high risk, high risk, high risk, moderate risk,moderate risk. The latter comes to the construction of the overall effect of static risk factor Dadu Bridge is 83.67(high risk), wherein the main beam segments each cantilever pouring construction efficacy coefficient 86.34(high risk), pile engineering efficacy coefficient 85.09(high risk), pier engineering efficacy coefficient 85.00(high risk), box girder pouring project efficacy coefficient 83.38(high risk), capping beam engineering efficacy coefficient 82.62(high risk),approach bridge project efficacy coefficient 81.09(high risk), caps abutments collar beam engineering efficacy coefficient 78.77(high risk), side span cast section and closed section project efficacy coefficient 77.99(moderate risk), deck lines and ancillary works efficacy coefficient 72.89(moderate risk). Risk assessment in the dynamic main beam segments each cantilever pouring construction project withgradual increase risk of increasing the boom sections. Their risk assessment results are basically the same. The latter result is more objective and comprehensive assessment, indicating that the established evaluation system is feasible and reasonable. |
