DETERMINATION OF PARTIAL FACTORS FOR MODELUNCERTAINTIES ADOPTED IN EARTHQUAKE PROOF DESIGN CODEFOR HIGHWAY ARCH BRIDGES

摘要

Determination of partial factors for model uncertainties prescribed in earthquake proof design code forhighway arch bridges has been attempted. In this study, model uncertainties mean the scatter of thenumerical results obtained from dynamic response analysis of arch bridge under strong earthquakemotion. The dynamic response analysis with respect to one typical steel arch bridge is carried out byseveral bridge researchers and engineers. Inverse-Lohse type arch deck bridge whose arch span length andbridge length are 114 meters and 173 meters, respectively, is adopted as the subject of study. Hyogoken-Nanbu Earthquake (Kobe Earthquake) wave is used as an input earthquake motion. Computer software forstructural analysis such as ABAQUS Ver.5.8, Y-fiber3D Ver.3.2, TDAP-III Ver.2.11, and NON-PIER areapplied in numerical analysis. Either Fiber model or Moment-Curvature model is used as a structuralelement model. About damping, either Rayleigh damping model or mass-proportional one is adopted innumerical analysis. Furthermore, it is treated in this study whether geometric nonlinearity is considered ornot. The value of partial factor for model uncertainties is determined by considering the scatter ofmaximum axial force of arch rib, maximum bending moment of stiffened girder, maximum horizontaldisplacement of stiffened girder, and so on obtained from dynamic response analysis. The result showsthat the value of 1.15 may be suitable to the partial factor in case that Moment-Curvature model is adoptedinstead of Fiber model. It has been also revealed that the value of 1.10 may be appropriate to the case thatmass-proportional damping model is applied instead of Rayleigh damping model or the case thatgeometric nonlinearity is not taken into account in dynamic response analysis of highway arch bridges.Finally, the following value of partial factor γA is proposed according to the response analysis;that is, γA = 1.0 in case of static analysis and γA = 1.05 in case of dynamic analysis.