Incremental launching method or ILM bridge construction
When talking about construction, the first thing that comes to mind is the construction of a building or a bridge. No doubt, bridge building and launching is one of the key areas in the construction industry. The bridge launching process is a complex, lengthy process with many aspects involved depending on factors such as project size and resources at hand. There are various bridge launching techniques such as cast-in-situ, precast and cable-stayed method. One such bridge launching method which simplifies bridge construction is the incremental launching method procedure. Plenty of planning and detail goes into the construction of a strong and operational ILM bridge. Standard construction methods need to be followed in order to avoid construction mishaps.
Let’s take a closer look at the construction cycle of incremental launching bridges as well as the suitability of the ilm bridge construction method.
Construction cycle of incremental launching bridge
The ILM bridge method follows a suitable technological design with certain aspects of the ILM method which is projected to the superstructure design. This brings in many advantages and is highly effective in comparison to other methods, in spite of the higher material demands. Some of the major advantages include minimum formwork, maximum productivity, and reinforcement assemblages along the whole length of the segment, etc. It is virtually a factory for bridge construction in segments.
Now, what does the construction cycle of an ILM look like? Simply put, the principle behind the incrementally launched bridge comprises building superstructure segments in a casting yard that could be located behind the bridge abutment. Every segment is matchcast against the earlier one and then prestressed to the section of superstructure built previously. Then the entire superstructure is jacked forward to a distance equal to the length of this segment. Until the bridge is in its final position, this process is repeated after which the temporary bearings are replaced by the permanent bearings. This construction method is generally used for bridges with a constant cross-sectional shape throughout their length. The bridge should either be straight or have a constant vertical and horizontal curvature. Additionally, workers’ safety is an important element to be considered. The time taken to build each part of the bridge and eventually converting it into a single piece requires enormous accuracy and precision
Suitability of ILM bridge construction method
The incremental launching method is convenient and efficient, applicable mainly to structures with high piers or locations where the formwork on solid centring cannot be used. This could include areas above the existing built-up area and water areas. If we were to analyze the suitability of this method compared to others, the ILM procedure is faster, uses less space with its superstructure assembly, and causes minimal disturbance to its surrounding environment, especially sensitive areas. Moreover, it offers increased worker safety as the erection work is carried out at a lower elevation and is used for bridge decks with lengths greater than 250m.
Hence, although it requires specialized construction equipment, considerable analysis and design expertise, incremental bridge launching is still considered a popular bridge launching method. This is due to the fact that even today it is the most feasible method for constructing bridges in environmentally protected or inaccessible areas such as deep valleys and water crossings, as well as locations with poor soil conditions which make accessible equipment inconvenient. Businesses can learn more about the incremental launching method procedure by contacting us at Bygging Uddemann for a consultation or to get a quote.
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