Structural Reliability Analysis of Superstructure of Highway Bridges on CPEC

Abstract

Live load models representing truck traffic are the governing factors for the design of bridges. The live load effects on bridges depend on Gross Vehicle Weight (GVW), span of bridge, axle spacing/number, vehicular occupancy, number of lanes and number of vehicles. In Pakistan, American Association of State Highway and Transportation Officials LRFD (AASHTO) and West Pakistan Code of Practice for Highway Bridges (WPCPHB) codes are used for the design of bridges. This paper presents the reliability analysis of existing bridges of Pakistan for Chinese design trucks which are completely different from Pakistani design truck. The China-Pakistan Economic Corridor (CPEC) is a development megaproject that aims to connect Gwadar Port in south western Pakistan to China’s north western region of Xinjiang, through a network of highways and railways. Single span and multi-span bridges are selected on western route of (CPEC). The actual Weight-in Motion (WIM) data for Chinese trucks was not available so the axle configuration and axles weights are selected from literature. Average Daily Truck Traffic data (ADTT) for these bridges was taken from National Highway Authority (NHA). Analysis of bridges is carried out using CSI-Bridge and AASHTO LRFD, PHBC and Chinese Codes are used to analyze the bridges. The resultant load effects (shear, moment) are extrapolated using non-parametric and linear fit for 75 years return period to carry out the reliability analysis. It is concluded that the reliability index of various bridges is less than the target reliability value which is 3.5 in AASHTO LRFD Code, so the existing bridges are less safe. The probability of failure in single span bridge is maximum using HL-93 truck while in case of multi-span bridges Class-A truck has maximum failure probability. Keywords: Live load model, Highway bridges, on-parametric fit, reliability index