To study the influence of residual stress on the corrosion behavior of welded structures, methods such as residual stress measurement, microstructure observation, and corrosion morphology observation were used. The energy transformation model and corrosion-resistance constant model were utilized to reveal the mechanism of residual stress on the welded structures’ corrosion behavior. The results show that the fusion line was the region that is most heavily affected by corrosion and sustains more serious corrosion damage than other areas, resulting in the welded structure becoming a high-incidence area for corrosion cracking and failure. Residual tensile stress could reduce the activation energy and surface atomic density, and therefore decrease the corrosion resistance of the welded structures. The residual compressive stress decreased the activation energy needed by metal atoms to convert into metal ions in welded structures, and simultaneously increased the surface atomic density. The corrosion resistance of the welded structures ultimately increased owing to the combined influence of changes in activation energy and surface atomic density.

Strain measurement is an important component in model tests of combustible internal explosions. Strain gauges are used to measure strain in traditional electrical measurement methods and have some limitations, such as susceptibility to electromagnetic interference, short life, and inability to distribute. Fiber Bragg gratings (FBGs) are developing into useful sensing tools that can respond to changes in stress, strain, and temperature by changing wavelengths. FBGs have excellent sensing performance, such as long life, antielectromagnetic interference, easy networking, and good reusability. In this paper, FBG sensors are applied to strain monitoring in ethylene flammable implosion experiments. In the ethylene flammable implosion tests, an FBG was placed on the inner surface of the bottom plate of the rectangular steel test device near the detonation vent by the sticking method. The reliability and repeatability of the strain change of the FBG affected by detonation overpressure and combustion were tested at this point. Four explosion tests were carried out. The test results showed that FBG sensors could obtain stable and reliable strain data in all four tests. The strain variation reflects the development of overpressure and combustion in the whole process from ignition. For the strain amplitude formed by overpressure, the minimum was 1.449 με (the third test), and the maximum was 48.181 με (the fourth test).For the strain amplitude step change formed by the deflagration flame front passing the measurement points, the minimum was 1.673 με (the second test), and the maximum was 19.724 με (the fourth test).The strain amplitude produced by the deflagration temperature effect in the four tests ranged from 72.803 με (the first test) to 143.381 με (the fourth test).The results show that FBG sensors can provide reliable and effective strain monitoring data for the experimental study of flammable implosions.

The nucleation mechanism of corrosion cracks in welded structures in natural seawater has been revealed through investigation on the corrosion behavior of X65‐welded structures in natural seawater. The evolution laws of surface corrosion morphology, residual stress, and areas of welded structures with the most serious corrosion damage were analyzed by microstructure observation, corrosion morphology observation, residual stress detection, and magnetic field detection. The results show that the main factors of determining surface corrosion morphology evolution law of welded structures are microstructures of the weld joint, heat‐affected zone (HAZ), and the fusion line. Due to the difference of corrosion rates between the weld joint, HAZ, and the coarse Widmänstatten structure in fusion line, the fusion line of welded structures receives the most serious damage while being corroded. Meanwhile, mutual reinforcement of residual stress and corrosion damage on the surface of welded structures further accelerate the nucleation of corrosion cracks. Under the influences of microstructure, residual stress, and corrosion, corrosion cracks that are parallel to weld joints generate first in the fusion line of welded structures. Therefore, it makes welded structures the source of marine steel structures’ corrosion failure.

BS700 high-strength steel is widely used in engineering. Welding residual stress during the manufacturing process has a significant influence on the structural safety and service life of steel structures. In this study, the residual stress of a BS700 butt-welded box section axial compression member was studied by the blind-hole method, its distribution law was summarized, and a residual stress distribution model was established. By establishing a finite element model considering initial geometric imperfection and residual stress, the influence of residual stress on the stability of axial compression members was analyzed. The results illustrated that the residual tensile stress near the weld in the welded box section axial compression members was the largest: the average residual tensile stress reached 76.6% of the measured steel yield strength, the residual tensile stress at the roof and web were almost the same, and the residual tensile stress at the corner was approximately 11.6% of the measured yield strength. The residual stress had a different influence on the stability factor of the axial compression members with different width-thickness ratios, and the influence decreased with the increase in the width-thickness ratio. In addition, when the slenderness ratio of members ranged between 20 and 70, the residual stress had a significant influence on the stability of members, while outside that interval, the influence was relatively small.

The corrosion behaviors of X65 welded structures were investigated, aiming to achieve the influence of residual stress on the corrosion behaviors of welded structures in the nature seawater. Methods such as corrosion rate measurement and corrosion morphology observation were used in the research. The results indicated that high-level of residual stress could accelerate the corrosion damage of weld joint, HAZ, and parent metal of welded structures, but had little influence on the overall corrosion rate of welded structures. Under the influence of different level of residual stress, corrosion morphology evolution on the surface of weld joint, HAZ, and parent metal were different, and so did the corrosion characteristics of the different areas of welded structures. Compared to the weld joint and parent metal, area with the most serious corrosion damage generated in the HAZ at last. Therefore, the HAZ needs to be significant concerned while designing the corrosion failure prevention measures of the welded structures.

The overall stability of a movable high-strength inverted-triangular steel bridge is worth studying because of its new truss structure. In this study, an approach was proposed based on the stiffness equivalence principle in which the inverted-triangle truss structure was modeled as a thin-walled triangular beam. On this basis, the calculation of the critical load of elastic stability of a movable high-strength inverted-triangular steel bridge with variable rigidity at both ends and locally uniformly distributed load was carried out based on the energy theory, which was in good agreement with existing theories. A material performance test at BS700 was carried out to establish the material properties, and then a finite element model of the bridge was established, the results of which were compared with those of the experimental load test, in order to verify the accuracy of the finite element model. Considering material nonlinearity and geometric nonlinearity, nonlinear buckling analysis of the bridge was conducted and the factors influencing the bridge’s ultimate bearing capacity were analyzed.