The efficient maintenance of the steel bridges is considered to be important. The hybrid structures in this study, the steel bridges are composed with concrete members. As a result, it prevents corrosion. In addition, the stiffness increases from the bridges of only steel members. The bridges will be able to last for a long time by these effects. However, it tends to crack by its thermal stress when concrete hardened. If a concrete thermal gradient is reduced, the crack is suppressed.
