A Japanese builder is using a new construction method called concrete lapping with preerected composite arch (CLCA). CLCA eliminates the shortcomings of the traditional arch construction methods and meets stringent cost and scheduling requirements. P. S. Concrete Ltd. of Tokyo has used CLCA to construct two bridges in Japan - the Asahi Bridge and the Joshi Bridge. Both bridges took two 8-month construction seasons to build.
CLCA uses rectangular cross-section tubular steel arches filled with concrete to act as the false work to form the reinforced concrete bridge arch. The first step in the process is to construct reinforced concrete abutments on each side of the river. Next, an assembly consisting of several tubular steel half arches is built standing upright on its end on opposite sides of the river. Each half is swung down around hinges at its springings to join at the arch crown, then the joined steel arch tubes are pumped full of concrete. Reinforced steel is placed around the composite structures initally using conventional techniques, and finally using movable platforms that work their way up the composite arches from each side of the river. The bridge is finished using conventional methods.