| 摘要 |
<p>The superstructure of a road bridge, esp. across a river, supported on end bases and any intervening piers, is first raised by hydraulic presses and then lowered onto support elements thrust below the bridge bearings. The retracted presses are set on a correspondingly elevated base, and extended to raise the superstructure, which is then lowered onto further support elements at greater height, until the required level is attained. Bases and piers are heightened in stages, and bridges bearings are secured on them. Plates, of bridge width, are hinged to the superstructure ends, with their open ends sliding on the road tracks during raising and lowering. An existing bridge superstructure can be raised - as required because of higher water level or taller ship passage - without erecting a new one, and with min. road traffic interruption.</p> |
