Molecular dynamics simulations are employed to investigate the superelastic–plastic behaviors of nanocrystalline NiTi shape memory alloy subjected to tensile strains of up to 12%. The effects of strain rate (6 × 108/s–4.8 × 109/s) and temperature (400–600 K) on the recoverable phase transformation and irrecoverable plastic deformation during loading are examined. The findings indicate that reducing grain size, increasing temperature, and strain rate all serve to suppress martensitic transformation. The plastic deformation observed in nanocrystalline NiTi exhibits a close relationship with grain-boundary sliding, the generation of disordered structures, and the proliferation of dislocations. The stress–strain behaviors display an obvious strain-rate hardening effect in terms of both the critical transformation stress and the yield stress of the martensite phase. Additionally, it is found that the strain-rate sensitivity is weakened by decreasing the grain size. At higher temperatures, the temperature-softening during plastic deformation is closely related to the sliding of grain-boundary atoms. More pronounced grain-boundary sliding leads to an increase in disordered structures and the destruction of the crystal structure. The evolution of the microstructure manifests that the strain-rate hardening effect competes significantly with the temperature-softening effect, particularly at high temperatures and high strain rates. Higher temperatures are capable of weakening the strain-rate hardening effect, while higher strain rates tend to alleviate the temperature-softening phenomenon. Meanwhile, strain rate and temperature exert coupling effects on the residual strain in nanocrystalline NiTi after unloading, by influencing both the residual martensite and unrecoverable disordered structures.

In this paper, a method to control the lime reaction by different slaking conditions is proposed to reduce the occurrence of cracks in newly repaired earthen city walls. The effects and mechanisms of the slaking time (0 h, 12 h, 24 h, 48 h and 72 h), lime content (10%, 15% and 20%), and moisture content (14%, 18% and 22%) on the cracking and mechanical properties of lime soil were analyzed by the test results of surface cracks, triaxial compression, particle gradation, pH value, X-ray diffraction and scanning electron microscope. The results show that proper slaking of lime soil specimens can reduce surface cracks and improve mechanical properties. After 12 h of appropriate slaking, the crack rate of the lime soil with 20% content decreased by 97.13%, the cohesion increased by 20.27%, and the internal friction angle decreased by 11.27%. However, the mechanical properties decreased when the slaking time was too long. After 72 h of slaking, the cohesion of 20% lime soil decreased by 8.21% and the internal friction angle increased by 2.82%. Further analysis shows that the appropriate slaking conditions can regulate the reaction rate and alkali environment, control the lime produced cementitious substances, improve the particle gradation and further reduce the occurrence of surface cracks. These results provide a basis for the restoration technology of newly repaired earthen city walls.

At present, the midstory isolation (MSI) technology has great potential for application in historical buildings’ retrofitting and multifunction buildings. The coupling effect due to the variability of the location of the isolation layer may amplify the structural seismic response and is required for in‐depth analysis. This paper aims to evaluate the magnitude of the coupling effect and delimitate the region of the coupling effect to be considered. Based on the complex mode superposition method, the explicit formulas for calculating the random response of the simplified model are deduced. The root‐mean‐square (RMS) ratio of the shear force coefficient of the upper isolation system is adopted as the performance indicator to evaluate the coupling amplification effect of the MSI system. Parameter analysis indicates that the coupling region is closely related to the mass ratio and frequency ratio of the upper and lower structures to the isolation layer. In general, the region of the coupling effect to be considered can be divided into two parts according to parameters of frequency ratios, depending on the thresholds of the performance indicator. As the mass ratio of the upper isolation system to the entire system increases, one of the coupling regions shrinks and eventually disappears, indicating that the coupling amplification effect in this region can be neglected under certain conditions. Finally, the time‐domain analysis of three representative numerical cases of MSI buildings was performed to verify the reliability of the results obtained from the frequency‐domain analysis. The research results can provide technical guidance for the preliminary design of the MSI buildings.