Technical reasons analysis about a collapse accident of a new-building highway super large bridge pier formwork

March 12, 2011, a newly built highway´s super large bridge´s pier formwork collapse has happened, and three workers have been killed. Three technological personnel have made a thorough survey on the spot, and the relevant staffs have been inquired. The following aspects have been calculated and analyzed including the connect strength of bolts in the two semicircular formworks´ connection, the compressive strength of the connected holes, the connection holes´ shear strength, the shapes of holes and bolt connection technique. The technicians consider that in the pouring of concrete, the temperature is relatively low and increase the fixed time at the beginning of the concrete, together with casting speed is faster, and cause the new pouring concrete lateral pressure increased. The formwork bottom bolts have not glibly been connected, bolt hole connecting there is relatively large deformations, and the effective compressive-cut areas have been reduced. When the compressive and shear strength of one hole cannot meet the requirements, the connection hole is destructed by compressive stress and shear stress, the whole bolt is pulled out from the hole, then the load of the bolt transfer to the nearest bolt, which leading to the closest bolt or be pulled out on the whole, or be pulled apart, to generate a domino effect, the concrete pouring out at that time. Because concrete releasing from the single formwork´s bottom, producing level force to another half steel formwork, causing the formwork produce displacement, and the formwork fall due to the instability. Finally corresponding prevention measures are put forward; these have certain reference value to prevent similar accidents.