Concrete arch buried bridge

摘要

A concrete arch buried bridge made up of upper and lower arched parts of corrugated metal provided with a reinforced concrete cap with a footing at each side, having an abutment extending inward under the margin of the upper part. The margins of the respective upper and lower parts have a connection which can be left loose to enable their relative movement and tightened so that they are rigidly held together. Each margin of the lower part has a permanent connection to the adjacent abutment which allows movement in the upward and downward direction, but resists lateral movement. The bridge is constructed by first placing the lower part on a compacted fill and making the connection between the margins of the upper part and the lower part. Then, the concrete cap is formed on top of the upper part and when the concrete is set sufficiently, the connection loosened and the fill completed on top of it. The weight of the concrete and the fill will cause the upper part to settle and move downward relative to the lower part. When the structure has settled the connection may either be tightened or left somewhat loose with provision made to prevent the lower part rising.