Continuous drive friction welding (CDFW) is an economical and productive method for joining similar metals. In this study, 45 # steel was joined via CDFW, and the material heat distribution, flow behaviour, flash formation and fracture mode were investigated via experiments and simulations. The bar was divided into three zones in the direction of radius (R), the R zone near the axis, the edge zone at the edge of the R and the 0.5 R zone between the R zone and edge zone. The maximum flow velocity and temperature of the joint first appeared in the 0.5 R zone, and as the friction continued, the maximum temperature moved to the edge zone, followed by flash. When the friction time was 9 s, the maximum tensile strength was 674 MPa, the fracture mode was the coexistence of ductile and brittle and the fracture location had an obvious boundary. Ductile fracture occurred in the R zone, and the flash took a lot of heat, brittle fracture occurred in the 0.5 R and edge zones. The maximum microhardness of the joint is 295 HV in the weld zone, and the microhardness decreased in the partially deformed zone. When the friction time was appropriate, the heat distribution was uniform and sufficient, and the grains exhibited a significant degree of dynamic recrystallisation refinement.

The present work addresses the critical challenge of assessing building facade watertightness against wind-driven rain, a major threat to structural integrity and durability. The current evaluation methods rely heavily on standardized test outcomes, neglecting a disconnect between test conditions and real-world exposure, leading to subjective judgments. To bridge this gap, this paper developed a quantitative method linking key inspection parameters (pump pressure, water spray distance) to wind-driven rain characteristics (wind speed, rainfall intensity) in the Shanghai area using statistical return periods. The calculation process encompasses regression models that correlate extreme rainfall and wind velocity values over sub-daily intervals, as well as a method for extrapolating maximum wind velocities using wind data coinciding with rainfall events. This approach enables specification-compliant performance assessment and tailored inspection protocols, such as JGJ/T 299, EN 12155, and ASTM E547. Applied to two Shanghai buildings, the method demonstrated a robust framework for translating environmental data into actionable inspection criteria. The results show a direct correlation between test parameters and extreme weather statistics. For instance, the watertightness performance of an old building is quantitively assessed as a return period of 1.02 years, while a new office building aiming for 50-year waterproofing could be inspected at a pump pressure of 900 kPa and a spraying distance of 0.15 m using the proposed method. This paper offers a data-driven alternative to empirical assessments, enhancing reliability in facade design and regulatory compliance, and provides a scientific basis for decision-making in building maintenance and renovation.

Currently, both Chinese and international standards have not addressed the fatigue design for encased composite beams with welded shear studs (ECB-S), which undoubtedly limits the application of encased composite structures under fatigue loading conditions. This paper, combining a series of existing fatigue test results for ECB-Ss, proposes a fatigue design method for ECB-S that can serve as a reference for practical engineering design. Regarding the flexural fatigue failure characteristics of ECB-S, the overall safety of ECB-S is ensured through individual fatigue designs for key components such as the embedded steel sections, tensile rebars, and encasing concrete. Specifically, the fatigue design or verification of tensile rebars is based on the design S - N curve obtained from forty-two S - N data points in ECB and ECB-S fatigue tests, taking into account the effect of stress ratio. The fatigue design or verification of embedded steel sections is based on the S - N curve derived from eight S - N data points in ECB-S fatigue tests, considering the coupling effects of fractures between embedded steel sections and tensile rebars. For the compressive concrete, the fatigue design methods in the current reinforced concrete structural codes are directly applied for verification. Finally, the feasibility and rationality of the ECB-S fatigue design method proposed in this paper are validated by fatigue test results, and corresponding fatigue design recommendations are provided. The mean values of ratios of fatigue lives between the calculated values by the design method and experimental values are 0.403 for embedded steel sections and 0.280 for tensile rebars. Additionally, the maximum compressive stress in concrete remains below its compressive fatigue strength. The findings of this paper can offer reference and guidance for the practical engineering design of ECB-S.

Based on the Zhengzhou–Xuchang Intercity Railway tunnel project passing beneath Terminal 1 of Xinzheng International Airport, this study employs a three-dimensional numerical analysis model to investigate the effects of tunnel depth and pile foundation structure on ground surface settlement and pile foundation response during twin-line shield tunnelling in typical cohesive soils under tunnel side-crossing and under-crossing conditions. The results indicate that during tunnel side-crossing, the ground surface settlement profiles evolved from V-shaped to W-shaped before and after twin-tunnel breakthrough. With increasing tunnel depth, the lateral displacement profiles of the left-row and right-row piles transformed from spindle-shaped to X-shaped. With increasing pile count, the maximum axial force per pile decreased from 320.1 kN in the single-pile configuration to 197.4 kN in the six-pile configuration, a reduction of 38.3%. During tunnel under-crossing, the lateral displacement profiles of both left-row and right-row piles exhibit X-shaped profiles at different tunnel depths, and the pile-top displacement varies slightly with a maximum of 1.1 mm. With increasing pile count, the maximum axial force per pile decreased from 202.2 kN to 132.1 kN, a reduction of 34.7%. The findings provide valuable reference for design and construction control of twin-line shield tunnels crossing existing airport pile foundations in cohesive soil.