To conduct fracture resistance analysis of railway steel bridges in low-temperature environments, propose

low-temperature anti-fracture design recommendations, and provide key parameter data such as low-temperature mechanical properties and impact toughness of Q345qD bridge steel widely used in railway steel bridges, this paper selects

five temperature points that railway steel bridges may encounter during service, conducting systematic low-temperature static tensile tests and low-

temperature impact tests, and comparing and analyzing the test results with existing literature data. The conclusions are as follows:

1) As the environmental temperature decreases, the yield strength and tensile strength of bridge steel Q345qD both increase, with the increase in tensile strength being greater than that in yield strength. The yield-to-tensile ratio decreases with temperature reduction, indicating higher strength reserves.

2) Bridge steel Q345qD exhibits good plasticity in low-temperature environments, with no significant decrease in elongation after fracture and reduction of area.

Within the studied temperature range, the elastic modulus shows no significant change.

3) Bridge steel Q345qD demonstrates good impact toughness. Within the studied temperature range, compared to Q345 structural steel with the same yield strength, it has higher upper and lower shelf energy, indicating better impact toughness. It also meets the impact energy limits specified by relevant standards under low-temperature conditions.

In summary, bridge steel Q345qD possesses good low-temperature strength, plasticity, and impact toughness, making it suitable for use in conventional bridge low-temperature environments.