To investigate the degradation law of the mechanical properties of corroded steel, the standard specimens from machining steel members in service for 9 years in an industrial environment were subjected to tensile tests. The influences of different degrees and types of corrosion on the fracture path, stress-strain curve, and mechanical properties of specimens were discussed. Finally, the damage constitutive model of corroded steel was established based on the damage mechanics theory. The results showed that the failure modes of corroded specimens were related to the degrees and types of corrosion. The fracture morphology of specimens with general corrosion were step-like and the fractures of steel were uneven. However, those with local corrosion were mainly flat-like, and the fracture path was along the cross section where the larger corrosion pits were located. The fracture path of the specimen was related to the interaction of the corroded surface and internal material defects (holes). Meanwhile, with the increase of corrosion degree, the yield platform of stress-strain curve gradually became shorter, or even disappeared, and the ultimate strain and elongation at break decreased, implying that the ductility of steel became worse. Ultimately, the good agreement between the curves of the model and test indicated that the damage model could reflect the damage development process of corroded steel in the tensile process better. Corrosion damage resulted in the decrease in the damage threshold, and the damage variable D decreased by the time fracture occurred and the maximum reduction rate was up to 62.5%.

The cross section would be reduced and the material properties of the steel structure would be deteriorated under the corrosion environment, which will have different effects on the earthquake resistant behavior. This paper takes corroded H-steel column as the research object. Firstly, the influence on the failure mode, bearing capacity, hysteretic properties, ductility and hysteretic energy is analyzed from specific factors which consist of different width-to-thickness on flange, different height-to-thickness on web and different axial compression ratios by FEA. The results show that, the area of the hysteresis loop diminishes gradually, the bearing capacity decrease clearly, the accumulative energy dissipation and ductility coefficient decreased continuously, and the degradation laws of buckling load, peak load, hysteretic energy and ductility coefficient of corroded H-steel columns are thereby established. When the thickness of flange decreased by 30%, the peak load decreased by 32% and hysteretic energy decreased by 77%. However, the peak load decreased by 14% and hysteretic energy decreased by 40% when the thickness of web decreased by 30%. When the axial compression ratio is 0.6, and the mass loss ratio of corroded H-steel columns reached 22%, the peak load and hysteretic energy decreased by 28% and 51% respectively. Secondly, the hysteretic model of load-displacement of corroded H-steel members under cyclic loading is proposed based on the simulation results and the degradation model of characteristic point of skeleton line was given. Finally, the evaluation criteria are proposed based on the seismic performance objectives, and the classification of failure types as well as the overall performance evaluation of corroded steel members are carried out.

This paper aims to study the hysteretic characteristics of the steel plates artificially corroded by neutral salt spray. Salt spray was applied to accelerate the corrosion on the steel plates; specimens of varying degrees of corrosion were obtained in this manner. And each specimen was subject to cyclic loading test to get the hysteretic curve. Then the experimental results were extensively discussed, focusing on strength and ductility, hysteretic energy, the skeleton curve, and unloading and loading curve. After that, the hysteretic constitutive model of corroded steel was established based on the first time loading criterion, unloading criterion, cycle skeleton criterion, and reloading curve criterion. The result of the experiment showed that, with the increase of the degree of corrosion, the mechanical properties and seismic energy dissipation performance of seismic energy of the steel decreased; the deterioration of ductility got aggravated. On the other hand, the skeleton curve and the Ramberg-Osgood model were well matched, and the coefficient of circular enhancement showed a decreasing trend; the variation of cyclic hardening exponent did not have an obvious pattern. Meanwhile, the hysteretic constitutive model of corroded steel and the results of the experiment were well matched.

The dynamic loads acting on concrete-filled steel tubular members under axial impacts by rigid bodies were studied herein by FEM. The whole impact process was simulated and the time history of the impact load was obtained. The effects of eight factors on the axial impact load were studied; these factors were the impact speed, mass ratio, axial pressure ratio, steel ratio, slenderness ratio, concrete strength, impact position, and boundary conditions. Besides this, the effects of concrete creep on the impact load were also considered by changing the material parameters of the concrete. The results show that axial impact load changes with time as a triangle. The peak value of impact load increases and the impact resistance improves with the growth of the axial pressure ratio, steel ratio, slenderness ratio, and concrete strength after creep occurs. As the eccentricity of the axial impact acting on a concrete-filled steel tubular member increases, the peak value of the impact load decreases. The enhancement of constraints at both ends of the member can improve the impact resistance. The creep reduction coefficients for the peak axial impact load of a concrete-filled steel tubular member under axial compression and considering the creep effect over 6 months and 30 years are 0.60 and 0.55, respectively. A calculation formula for the peak value of impact load was suggested based on the existing formula, and its accuracy was proved by finite element calculation in this study.

The main building of Zone II of Zhanjiang Bay Laboratory R&D Building adopts a steel frame–core tube shear wall structure system, with a 53.4 m large-span and heavy-load-transfer truss on the fourth floor. In order to propose the optimal construction and installation scheme for the large-span and heavy-load-transfer truss, the simplified model, single model, and 3D model are utilized to compare Scheme 1 with rigid connection and Scheme 2 with elastic connection and rigid connection. After completing the construction of the underground layer and towers on both sides, in Scheme 1, the fourth-floor transfer truss is directly connected to the towers on both sides in a rigid manner. Subsequently, the support at the bottom of the transfer truss is removed, allowing for layer-by-layer construction. The transfer truss remains rigidly connected to both side towers throughout. On the other hand, in Scheme 2, initially, the transfer truss is connected to both side towers through upper chords and diagonal bars before being constructed upwards until reaching the sixth floor. Once formed as a whole with two floors above using large diagonal tie rods, lower chords of the large-span and heavy-load-transfer truss are then connected with another diagonal bar to establish a rigid connection between the transfer truss and towers; thereafter, upward construction continues. Following completion of constructing a seven-story large diagonal tie rod, whereupon removal of support at the bottom of the conversion truss occurs, subsequent layer-by-layer construction takes place accordingly. It has been observed that employing Scheme 2 can enhance stress distribution within core barrel shear walls as well as transfer trusses while ensuring deflection and stress levels meet requirements for the large-span and heavy-load-transfer truss, thereby rendering structural stress more rationalized, leading to significantly improved overall safety.

Environmental factors significantly affect the fatigue performance of weathering steel welded components in high-altitude, low-temperature corrosive environments. This study conducted multi-factor-coupled constant-amplitude fatigue tests on Q500qENH weathering steel V-groove welded joints and built an equivalent finite element model using test data to explore key influencing factors under multi-condition coupling. Results show that stress level most significantly affects fatigue performance, followed by corrosion duration, then ambient temperature, with influences decreasing in turn. Analyzing 18-day cyclic immersion corrosion morphology predicts 21-year outdoor corrosion in plateau regions, providing a reliable method for long-term exposure prediction. Finite element simulations confirm that low temperatures improve slightly corroded specimens’ fatigue performance by 20%, but damage accumulates before optimal service. This study offers key parameters for safe design of high-altitude weathering steel welded components.