Technique of Fixed Time Closure for Main Bridge of South Bridge of Xiazhang Sea-Crossing Bridge

The main bridge of the south bridge of the Xiazhang Sea-Crossing Bridge is a steel and concrete composite girder cable-stayed bridge with double pylons and parallel cable planes.Originally it was decided that the closure of the central span of the main bridge was to be carried out,using the cutting closure scheme,but because the temperature prediction of the scheme was demanding and the starting time for the closure was uncertain,the cutting closure scheme was therefore changed into the technique of the fixed time closure.The technique was that after the second girder segment of the main bridge was installed nearby the closure gap,the expanded closure gap was consecutively observed,the material for the closure segment was laid off in advance and immediately after the last typical segment was installed,the closure segment was lifted in place and installed.In the technique,the slotted hole tool plates and the temporary connectors were used as the auxiliary tools,the closure gap was firstly fixed by the plates and connectors,the dimensions of the permanent splice plates were then confirmed and finally the tool plates would be replaced with the permanent splice plates and the closure of the central span was completed.With the technique of the fixed time closure,the closure of the central span of the bridge proceeded smoothly.Practice proved that the technique relaxed the accuracy requirement for the system deformation prediction,increased the reliability of the closure and reduced the safety risk of the structure.