To study the corrosion behavior of galvanized steel wires under stress, the influence of stress level, pH value, Cl- concentration and the coupling effect on the corrosion rate of cable steel wire were discussed through stress corrosion test. The prediction formula of corrosion rate of steel wire was established based on response surface method. The constitutive model of steel wire was also put forward. The results showed that the effects of stress level, pH value and Cl- concentration on corrosion rate were pH > Cl- > σ. The stress corrosion increase the corrosion degree of steel wire by 4 times, the degradation ratio of yield and ultimate strength by 2 times, and the degradation rate of elongation and elastic modulus by 3 times. The relationship between the stress level, corrosion degree and the strength or elongation of steel wire was linear, but that of elastic modulus was nonlinear.

This paper introduces a new signal-filtering method, which is aimed at processing long-span bridge structural health monitoring (SHM) data based on empirical mode decomposition (EMD) and fractal conservation law (FCL). The long-span bridge SHM data is selected from vertical vibration data of the Runyang Bridge’s main girder. The key idea of this paper is to enhance the frequency amplitude of the target signal and at the same time to weaken the surroundings-caused signal noise by combining methods as EMD and FCL after confirming the long-span bridge’s natural frequency. EMD operation consists of decomposing the vibration data by EMD, selection of effective intrinsic mode functions (IMFs) and effective IMF recombination. FCL theory will be applied on the filtering function to process effective IMFs in the frequency domain before recombination. This theory is based on a partial differential equation modified by a nonlocal fractional anti-diffusive term of lower order. The effect of the EMDFCL filter is compared with the EMD method, FCL method and filter strategy that combines EMD and low-pass filtering, respectively. Results show that the EMDFCL filter outperforms the other signal filtering methods in natural frequency recognition of long-span bridge SHM data. In particular, the bridge’s natural frequencies distinguished by EMDFCL match well with the calculated frequencies and original fingerprint.

A fatigue design method for the orthotropic steel deck bridges is proposed. The stress characteristics of welded details are analyzed using the finite element method. Based on the fatigue performance, the structural parameters of the orthotropic steel decks (OSDs) are optimized using the combination BP (back propagation) neural network and genetic algorithms (GA). The calculated results demonstrate that the weld stresses at the deck plate-to-rib, deck plate-to-rib-to-diaphragm welded details are mainly bending stress while those at the rib-to-rib welded details are mainly membrane stress. The fatigue stress of each weld is deeply affected by the transverse and longitudinal direction positions. The local effect of stress distribution of all welded details is remarkable. The calculated results obtained using the proposed model are in good agreement with those obtained using ANSYS and the errors are within 5%. The optimal structural results are highly influenced by the applied wheel loadings, while the optimal results for the deck thickness and the U-rib opening size are highly influenced by temperature. Especially on the ordinary lane, temperature has a great effect on the fatigue performance for all welded details.