Bridge Builder for Pearl Harbor Memorial Bridge (PDF) –
This project required a very unusual bridge builder in that four main frames were needed. Most balanced cantilever bridges require only two main frames, as most bridges of this type only have two webs.
We performed an independent design review of the bridge builder, together with the required structural analysis. We calculated the bridge builder reactions on the bridge superstructure and the expected formwork deflections. These parameters are required for checking construction stresses and developing proper casting curves for the balanced cantilevers. The immediate form deflections are combined with long-term creep and shrinkage deformations to determine the theoretical formwork elevations at the time of each segment pour.
Bridge builders, also referred to as form travelers, are self-launching formwork systems that support themselves entirely off the previous segment for constructing the current segment. Once the concrete has reached the specified strength, the longitudinal bridge tendons are stressed and the bridge builder is advanced by one segment length. The bridge builder is launched on a set of rails, which also provide the reactions at the back of the main frames to prevent the system from over-turning.
The contractor also hired us to develop an erection scheme and lifting solution for raising and installing the bottom deck that forms the underside of the segments. Lifting was accomplished with hydraulic jacks and the contractor tried out both bar- and strand-based lifting solutions. During the bottom deck erection we were on site to offer technical assistance and pre-lift inspections. Prior to the first segment pour at each heading, we performed an inspection to make sure the form traveler was properly assembled and secured.
Once construction was underway, we assisted the contractor with operational issues as they arose, such as trouble-shooting the cause of equipment damage and pre-pour setup issues.
For further information on form travelers, please feel free to contact us.
