PURPOSE: To facilitate the distribution of load to main levers by connecting divided trusses with pins to form an arch-shaped form shoring, bearing connections on struts and, at the same time, providing a jack between an abutment and a pin to make it possible to control axial force.

CONSTITUTION: A plurality of triangular shoring elements 10 are connected to each other to form divided trusses 3 and, at the same time, the divided trusses 3 are connected with 4 to form an arch-shaped form shoring A. The connections 4 of the divided trusses 3 are borne on struts 6 erected on the ground B and, at the same time, a jack 22 is provided to at least one end of a pair between holders 17 of abutments 1 and arch load receiving pins 5. When the struts 6 are settled, the jack 22 is operated to control the distribution of load to main levers 11. According to the constitution, the execution can be easily and economically carried out.