Extended end-plate (EP) bolted connections are widely used in steel structures as moment-resisting connections. Most of these connections are semi-rigid or in other words flexible. The paper aims to study the behavior of such connections under the effect of column top-side cyclic loading using the finite element (FE) method. For semi-rigid connections, it is very vital to determine the moment-rotation relationship as well as the connection stiffness. These beam-column connections have been parametrically studied, the effect of joint type, shear forces, diameter of bolt, thickness of end-plate, and end-plate style were studied. Parametric studies show that the panel zone shear force is the key factor and has a significant effect on the connection stiffness. Finally, based on the component method, the stiffness of the bending component is improved, and the initial stiffness calculation model of the connection under column top-side cyclic loadings is established. The results show that the calculation model is in good agreement with the finite element analyses, and this proves that the calculation model proposed in this study could act as a reference method.

Based on numerical shape functions and the structural stressing state theory, the mechanical properties of the curved prestressed concrete box girder (CPCBG) bridge model under different loading cases are presented. First, the generalized strain energy density (GSED) obtained from the measured strain data is used to represent the stressing state pattern of the structure; then, the stressing state of the concrete section is analyzed by plotting the strain and stress fields of the bridge model. The stressing state pattern and strain fields of the CPCBG are shown to reveal its mechanical properties. In addition, the measured concrete strain data are interpolated by the non-sample point interpolation (NPI) method. The strain and stress fields of the bridge model have been plotted to analyze the stressing state of the concrete cross-section. The internal forces in the concrete sections are calculated by using interpolated strains. Finally, the torsional effects are simulated by measuring the displacements to show the torsional behavior of the cross-section. The analysis and comparison of the internal force and strain fields reveal the common and different mechanical properties of the bridge model. The results of the analysis of the curved bridge model provide a reference for the future rational design of bridge projects.

Aiming to provide a solution for natural resource consumption and agricultural waste pollution, jujube nucleus is utilized as a substitute for coarse aggregate in the preparation of lightweight aggregate concrete. The effect of the jujube nucleus (JN) replacement ratio and the elevated temperature on the uniaxial compressive stress–strain curves of jujube nucleus concrete (JNC) are experimentally studied. The results show that the failure of the JNC prisms became more serious with the increase in the JN replacement ratio. The linear proportion in ascending branch and the descending slope of the stress–strain curves for JNC increased gradually with the increase in the JN replacement ratio and elevated temperature, which is probably owing to the higher porosity and lower stiffness of the jujube nucleus, compared to natural aggregate. Moreover, as the JN replacement ratio and the elevated temperature increase, the peak stress and elastic modulus in the stress–strain curves of JNC decrease gradually, whilst an increase in the peak strain shows up, which is possibly due to the growth of hydrate calcium silicate and calcium hydroxide hampered by sucrose molecules. Based on the test results, a series of theoretical formulas are proposed to predict the compressive performance of JNC. A material constitutive model is developed for describing the stress–strain relationship of JNC by considering the JN replacement ratio and elevated temperature.

This study investigates the mechanical behavior of molybdenum tailings (MT) concrete circular specimens under combined chloride salt dry–wet cycling and high-temperature exposure, simulating post-fire conditions in corrosive environments. A total of 50 circular cross-sectional specimens were fabricated with varying concrete strength grades (C30 and C40), MT replacement ratios (0–100%), and exposure conditions (NaCl solutions: 20,000 and 50,000 mg/L; temperature: ambient/400 °C). Axial compression experiments were conducted to evaluate their performance. Analysis of mass change rates and post-cycling phenomena indicated that MT content significantly influenced mass variation, with the 100% MT group having a 2.3 times higher mass increase than the 0% MT group. Especially, under coupled conditions, compared with the 0% MT control group, the 25% MT group showed a 28.6% increase in peak stress, 8.3% reduction in peak strain, 12.1% rise in Elastic modulus, and 13.3% decrease in Poisson’s ratio, confirming that MT incorporation mitigates coupled strength degradation. Two failure modes were identified: end-cone failure and overall splitting failure. Chloride salt corrosion markedly reduced the load-bearing capacity of the specimens, decreasing both their peak displacement and peak strain. Furthermore, peak strain decreased as the molybdenum tailings replacement ratio increased. Scanning electron microscopy (SEM) revealed that dry–wet cycling prior to high-temperature exposure promoted hydration product densification, indicating a partial enhancement of hydration reactions and consequent strength improvement. Although high-temperature exposure degraded the strength of MT concrete, the incorporation of MT mitigated this weakening effect. The relationship between the peak stress of concrete and its axial compressive strength under the coupled effects of MT replacement ratio and NaCl solution concentration has been established via fitting. This study reveals the coupled damage mechanism, verifying the mitigating effect of MT on coupled chloride-thermal damage, and establishing a validated bearing capacity prediction model, which provides a valuable reference for assessing the behavior of MT concrete circular specimens subjected to salt corrosion and elevated temperatures.