Highway bridge load rating has been moving toward structural reliability since the issuance of AASHTO LRFR specifications; however, the recommended load factors were carried out by a few reliable truck data. The objective of this study is to calibrate the live load factor in AASHTO LRFR Rating Specification by using huge amount of WIM data collected in California for more than ten years between 2001 and 2013. Since traffic volumes, vehicular overloads, and traffic components are highly related to the load effect induced, a set of calibration equations is proposed here, in which the nominal standard load effect models are used and different requirements of loading are taken into account. By the analytical model of platoons of trucks and the extrapolation of the gathered WIM data over a short period of time to remote future over a longer time period, the expected maximum live load effects over the rating period of 5 years are also obtained. Then, the live load factor is calibrated as the product of the codified value multiplied by the ratio between the nominal standard load effect and the expected mean value. The results show that the products of the two ratios present rather constant, implying the proposed method and load configurations selected are effective. In the end, the live load factors of 1.0 and 0.7 along with load configurations are recommended for a simple span length less than 300 ft. The recommended calibration method and live load factors will eliminate the unnecessary overconservatism in rating specifications.

Abstract： Emergencies result in random fluctuations to market demand and market prices, turning suppliers' risk attitude from neutral to aversion. Under this condition, the emergency buy-back contract model is build with the random market price and the risk-aversion supplier. The profit-CVaR risk assessment criterion of decentralized decision-making is revised to the Profit-CVaR risk evaluation criterion of centralized decision-making, the Buy-back contract is studied about whether it can realize the two-echelon supply chains' coordination under the new criterion. Numerical simulation is conducted to this model. The result shows that, when the market demand obeys normal distribution, the optimal order quantity of supply chain is related to the change of risk factors' step length and the variance of the normal distribution function. In certain range, when the risk factors change in a smaller step length, the optimal order quantity will occur bifurcation mutations, and the retailer and the suppliers' expected revenues and the wholesale price will also occur bifurcation mutations correspondingly. In addition, this kind of bifurcation mutations' intervals and the amplitude of above values will increase with the variance. And the supply chain can't be coordinated under the model in the bifurcation mutation area, while it can realize coordination in those areas without bifurcation mutations.Key words：stochastic price；risk aversion；buy-back contract；supply chain coordination；bifurcation phenomena 0 前言 *

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In this paper, the wind-induced responses of the Shanghai World Financial Center (SWFC) under Super Typhoon Lekima are measured using the health monitoring system. Based on the measurements, the characteristics of vibration, including probability density distribution of accelerations, power spectra, and mode shapes are studied. The curve method and the standard deviation method are used to analyze the relationship of the first- and second-order natural frequencies and damping ratios with amplitudes and the mean wind speed. The results show the following: (1) The structural wind-induced responses in the X and Y directions have high consistencies, and the vibration signals exhibit a peak state; moreover, response amplitudes and acceleration signals disperse when the floor height increases. (2) The first- and second-order natural frequencies in the X and Y directions decrease with the increasing amplitudes and are negatively correlated with mean wind speed; the maximum decrease in natural frequency is 5.794%. The first- and second-order damping ratios in the X and Y directions increase with the increasing amplitudes and are positively correlated with the mean wind speed; the maximum increase in damping ratio is 95.7%. (3) The curve method and the standard deviation method are similar in identifying dynamic characteristic parameters, but the discreteness of the natural frequencies obtained by the curve method is lesser. (4) Under excitations of various typhoons, the mode shapes of SWFC are basically the same, and the mode shapes in the X and Y directions increase with the height and have nonlinearity.

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