The random field model of corrosion depth on steel plate surface in neutral salt spray environment was investigated. 10 groups of specimens were subjected to accelerate corrosion by the neutral salt spray test, and the surface profile of corroded steel plates and the 3D data of corrosion depth were measured by three-dimensional non-contact surface topography instrument. The probability characteristics of corrosion depth were studied and the relationship between the average and the standard deviation of corrosion depth and the mass loss rate were analyzed. The corrosion depth were tested for ergodicity and stationarity and the autocorrelation function model of random field model of corrosion depth was proposed. The results of the study show that the corrosion depth on steel plate surface in neutral salt spray environment conformed to the normal distribution. With the increase of mass loss rate, the average and the standard deviation of the corrosion depth increased. The corrosion depth has ergodicity and stationarity. The random field model of cosine trigonometric function can accurately characterize the distribution of corrosion depth, which prepared the preliminary preparation for the finite element analysis of the corroded steel structure.

The time-dependent reliability of corroded steel beam was investigated. Nine groups of specimens were subjected to accelerate corrosion by the outdoor periodic spray test and monotonic tensile test. The surface profile of corroded steel plates and the 3D data of corrosion depth were measured by the three-dimensional non-contact surface topography instrument (PS50 3D). The probability distribution of corrosion depth and nominal yield strength of corroded steel plates were studied. Finally, a probabilistic limit state equation for corroded steel beams was established and the time-dependent failure probability and reliability index of corroded steel beams was calculated by Monte Carlo simulation method (MCS). The results of study show that the corrosion depth on steel plate surface and nominal yield strength of corroded steel plate conformed to the normal distribution. With the increase of corrosion time, the average, the standard deviation of the corrosion depth and relative yield strength increased while the mean of relative yield strength, nominal yield strength, nominal ultimate strength, the elongation decreased. The reliability index decreased rapidly with corrosion time, which shows that the reliability of steel structures under the aggressive environmental should be caused attention.

Construction projects require concurrent consideration of the three major objectives of construction period, cost, and quality. To address the multi-objective optimization issues of construction projects, mathematical models of construction period, quality, and cost are established, respectively, and multi-objective optimization models are constructed for different construction objectives. A hybrid optimization method combining an improved genetic algorithm (GA) with a time-varying mutation rate and a particle swarm algorithm (PSO) is proposed to optimize construction projects, which overcomes the shortcomings of the original GA and improves the global optimality and stability of results. Various construction projects were considered, and different construction objectives were analyzed individually. Finally, an uncertainty analysis is developed for the proposed GA-PSO algorithm and compared with GA and PSO. The results indicate that the proposed hybrid approach outperforms the PSO and GA algorithms in providing a better and more stable multi-objective optimized construction solution, with performance improvements of 4.3–8.5% and volatility reductions of 37.5–64.4%. This provides a reference for the optimal design of wind farms, buildings, and other construction projects.

The bond properties for plain bars in frost-damaged concrete under monotonic and reversed cyclic loading were investigated. Rapid freeze–thaw and the pull-out tests were carried out on the specimens with three kinds of concrete strength grade. The compressive strength of frost-damaged concrete and the bond stress–slip response of the specimens with different concrete strength grades and freeze–thaw cycles were obtained. The effect of concrete strength grade and of the freeze–thaw cycle on the bond behaviours between concrete and plain bars was studied. Results indicated that, with the increase in the number of freeze–thaw cycles, the bond strength, residual bond capacity, residual bond stress and the cyclic bond stress decreased while the peak slip increased, as well as there being a more obvious bond degradation rate for the specimens with the same concrete strength grade. For specimens subject to the same number of freeze–thaw cycles, the bond strength, residual bond capacity, residual bond stress and the cyclic bond stress increased with the increasing concrete strength grade. A bond–slip model for plain bars in frost-damaged concrete under monotonic and reversed cyclic loading is proposed, which can be used for performance evaluation of existing reinforced-concrete structures in cold areas.