The principle of the incremental launching bridge (ILM bridge) consists of building the bridge segments in a casting yard located behind the bridge abutment before building the bridge deck. Each segment is matchcast against the previous one and prestressed to the bridge deck already built. The entire bridge deck is then jacked forward a distance equal to the length of this segment.
You repeat this process until the bridge is fully constructed. This form of construction is often used for bridges with constant cross sectional shape throughout their length, and the bridge should either be straight or have a constant horizontal and vertical curvature.
In this article we will take a closer look into what advantages the incremental launching bridge method offers when constructing a bridge.
How is the ILM bridge beneficial?
There are three main advantages to the ILM bridge: the speed at which it can be built, increased flexibility of the method itself, a safer work environment when building it, cost reductions in terms of required equipment, and minimized environmental disturbance.
Increased construction speed
The ILM bridge method is one of the fastest and most efficient methods available. The bridge segments and the advancement of the bridge over the pillars happen in fixed installments with repetitions in both design and the process of fixing the segments. This results in a fast construction process since there won’t be any need for unique adjustments for each segment.
Easier access to the “construction site”
Valleys, steep slopes, streams, and other water bodies all provide a challenge with limited access to the area. Having to go back and forth with precast bridge segments can be difficult, or at times even impossible. The ILM method’s biggest advantage is that the majority of the construction work can take place from the prefabrication areas without needing to access surrounding areas.
Increased safety for the workers
Using the ILM bridge launching approach minimizes the risk for the construction workers since all the construction and assembly processes are done on-site of the prefabrication area. The lower elevation levels and not having to work around bridge pillars or half-constructed platforms also increases safety for the workers.
Requires less and smaller equipment
Due to the segments being constructed on-site, the project requires both less and smaller equipment, tools, and machines to deliver materials to constructed areas of the platform since all the construction and assembly takes place in the prefabrication area. As such, ILM bridge launching is often considered a fairly cost-effective method of construction.
Causes minimal disturbance to terrain
Last but not least, the incremental bridge launching approach does not cause any disturbance to surrounding areas, including environmentally sensitive areas. This is due to the fact that the launching process takes place from the prefabrication area, thus reducing the disturbance of surrounding landscape and trees compared to conventional methods.