To investigate the fatigue performance of the stud connectors of steel-concrete structures, fatigue crack propagation analysis and fatigue life calculation were carried out. Firstly, the finite element model with the initial crack based on linear elastic fracture mechanics (LEFM) was established, and the parameter analysis of the stress intensity factors (SIFs) of the studs and cracks with different geometric sizes was performed. Then, the propagation with mixed-type fatigue crack and I-type fatigue crack of the stud were calculated, and the variation of effective SIFs with the fatigue crack depth was analyzed. Finally, the flow chart of stud fatigue life evaluation which considers crack initiation and stable propagation was presented, and the short stud of steel-UHPC composite structures was taken as an example and verified. The calculation results show that the fatigue crack propagation type and the initial crack have an obvious influence on the fatigue life of the stud. It has acceptable accuracy that the fatigue life of short stud in UHPC simulated by considering the crack initiation. The critical damage parameters are greatly affected by the fatigue stress amplitude, and the initiation life of fatigue crack can account for more than 90% of the total fatigue life. This paper can provide a reference for evaluating the fatigue performance of studs in steel-concrete composite structures. Accurate evaluation of the fatigue life of stud connectors conforms to the concept of sustainable development.

The temperature distribution of the bridge and its thermal effect has always been an important issue for researchers. To investigate the temperature distribution and thermal stress in the steel-concrete composite bridge deck, a 1:4 ratio temperature gradient effect experimental study was carried out in this paper. First, a set of experimental equipment for laboratory temperature gradient loading was designed based on the principle of temperature gradient caused by solar radiation, the temperature gradient obtained from the measurements were compared with the specifications and verified by the FE method. Next, the loading of the steel-concrete composite deck at different temperatures was performed. The thermal stress response and change trend of the simply supported and continuously constrained boundary conditions under different temperature loads were analyzed. The experimental results show that the vertical temperature of steel-concrete composite bridge deck is nonlinear, which is consistent with the temperature gradient trend of specifications. The vertical temperature gradient has a great influence on the steel-concrete composite bridge deck under different constraints, and the extreme stress of concrete slab and steel beam is almost linear with the temperature gradient. Finally, some suggestions for steel-concrete composite deck design were provided based on the research results.

Traditional theoretical calculations, field measurements, and finite element methods sometimes fail to realize life cycle simulations of the temperature field and temperature effect of steel–concrete composite bridge deck systems. In this paper, a simulation method based on a back propagation–long short-term memory (BP-LSTM) network correlation model is proposed to predict the temperature field and temperature effect in a low-cost and highly efficient manner. A bridge was used as the engineering background according to a health monitoring system, and the finite element method based on the principle of heat transfer was used to expand the data sets. Data sets with structural, time, and environmental characteristics as the independent variables and temperature and the temperature effect as the dependent variables were formed. The correlation between the dependent and independent variables was verified using the maximal information coefficient. Thus, the BP-LSTM model was established, and the mean squared error loss function considering the time weight was designed. The data set was read in for training, verification, and testing, and a correlation model representing the relationship between the set’s independent and dependent variables was obtained with relatively high accuracy. Finally, combined with the bridge’s historical meteorological data, the established correlation model was used to simulate the bridge’s temperature field and temperature effect. The results indicated that the finite element calculation results of the structure’s temperature field based on the heat transfer principle were basically consistent with the measured results. The independent variables in the data set were non-linearly related to the dependent variables. The BP-LSTM’s prediction accuracy of the temperature field and temperature effect was above 98.8% and 94.5%, respectively, in good agreement with the target value. The variation law of the temperature field and temperature effect of the steel–concrete composite bridge deck system simulated by combining the historical meteorological statistics was in accordance with reality.