Non-uniform temperature fields are developed during the welding of studs in steel–concrete composite bridges. Due to uneven thermal expansion and reversible solid-state phase transformations between ferrite/martensite and austenite structures within the materials, residual stresses are induced, which ultimately degrades the mechanical performance of the structure. For a better understanding of the influence on steel–concrete composite bridges’ structural behavior by residual stress, accurate simulation of the spatio-temporal temperature distribution during stud welding under practical engineering conditions is critical. This study introduces a precise simulation method for temperature evolution during stud welding, in which the Gaussian heat source model was applied. The simulated results were validated by real welding temperature fields measured by the infrared thermography technique. The maximum error between the measured and simulated peak temperatures was 5%, demonstrating good agreement between the measured and simulated temperature distributions. Sensitivity analyses on input current and plate thickness were conducted. The results showed a positive correlation between peak temperature and input current. With lower input current, flatter temperature gradients were observed in both the transverse and thickness directions of the steel plate. Additionally, plate thickness exhibited minimal influence on radial peak temperature, with a maximum observed difference of 130 °C. However, its effect on peak temperature in the thickness direction was significant, yielding a maximum difference of approximately 1000 °C. The thermal influence of group studs was also investigated in this study. The results demonstrated that welding a new stud adjacent to existing ones introduced only minor disturbances to the established temperature field. The maximum peak temperature difference before and after welding was approximately 100 °C.

During the stud welding process, residual stresses are inevitably induced due to the significant temperature gradients and associated heterogeneous thermal expansion and contraction. These residual stresses significantly influence the mechanical properties of the welded structure. Quantitative evaluation of the welding residual stress distribution on the steel plate surface was performed using X-ray diffraction (XRD) and the blind-hole method. Results demonstrate that the radial residual stress initially increases and subsequently decreases with increasing distance from the weld ring. The circumferential residual stress is characterized as compressive throughout the measured region, also exhibiting an initial increase, followed by a decrease, and a subsequent increase with greater distance from the weld center. Both radial and circumferential stresses form a compressive stress zone within the weld and its immediate vicinity, with a peak value of approximately 170 MPa. The significant solid-state phase transformations occurring in the weld metal and the adjacent heat-affected zone lead to the development of compressive stresses upon cooling. The compressive stresses observed in the base metal region, far from the weld, are likely attributable to the initial rolling stresses inherent to the steel plate.