How to construct upslope bridges and downslope bridges for a launching gantry?
As the launching gantry construct the bridge, we usually meet a lot of different working conditions like longitudinal slope. In this case, we have to adjust height of support legs to create a suitable construction environment.
I will take an example that how to construct a bridge with max longitudinal slope 5% which usually is the max gradient the launching gantry could be used.
1. Upslope bridge
As the launching gantry construct the upslope bridge, add about 2m to rear support leg, add relevant height to middle support leg and rear bracket and reduce 2m to front support leg, then adjust the height of middle support leg to keep the launching gantry balance;
Before the launching gantry moves to cross spans, reduce the height of front support leg, increase height of middle support leg, rear bracket and rear support leg, keep gradient of main girder<0.5% and hang one winch at front part of launching gantry to prevent it sliding down. As the front support leg reaches its position, adjust the height of front support leg depending on that of middle support leg, start girder erection after level the launching gantry.
2. Downslope bridge
As the launching gantry construct the downslope bridge, add about 2m to front support leg, add relevant height to middle support leg, and reduce 2m to rear support leg and relevant height to rear bracket, then adjust the height of middle support leg to keep the launching gantry balance;
Before the launching gantry moves to cross spans, increase the height of front support leg and middle support leg, reduce height of rear bracket and rear support leg, keep gradient of main girder<0.5% and hang one winch at rear part of launching gantry to prevent it sliding down. As the front support leg reaches its position, adjust the height of front support leg depending on the longitudinal slope, add short sleeve between inner sleeve and connecting beam if there is a large slope, start girder erection after level the launching gantry.
Kindly note, height adjustment stated above is just a theoretical height, we should adjust support legs to suit the worksite conditions in the project, and concrete steps shall be guided by professional manufacturer of launching gantry, please do not operate it without any guide.
