Abstract
Reinforced concrete (RC) slabs which are now widely prevailed as the slabs of steel bridges, are historically investigated how and why they have developed. Namely, the various types of slabs applied for the steel bridges before RC slabs are surveyed to show that they had influences on the design of RC slabs such as the thickness and the span of the slab. And the bridge-flooring structures to support the slabs are also studied how they affected the design of the RC slab. At the same time, the traffic development and the material supplying conditions are also studied to make clear the the background of development of the RC slabs.
