Factors to consider while attempting incremental bridge launching
Building bridges has long since been an engineering feat achieved by mankind that dates right up to the medieval ages or even before. Since thousands of years, there has been a lot of innovation in bridge launching techniques. One such technique that is largely being used all over the world is incremental bridge launching method.
This technique consists of assembling the structure on one side of the obstacle to be crossed. This is followed by the structure being pushed across the obstacle and locked down in its final position. There are several advantages of using this technique. Some of these advantages involve creating minimal disturbance to surroundings, providing efficient work area for assembly, better worker safety (onlinepubs.trb.org, BRIDGE CONSTRUCTION PRACTICES USING INCREMENTAL LAUNCHING). When a bridge is being constructed using this method, it is very necessary for enhancing resistant of the structure during the launching process. The following pointers shed more light on these factors to implement while undertaking bridge launching techniques:
Providing stability
When the launching process is underway, the leading edge of the structure may undergo a ‘hogging’ movement. This may hamper the speed as well as the quality of construction being done. The hogging movement can basically be defined a type of cantilever action that makes it difficult to extend the bridge section. To reduce this, the span length of the structure’s nose can be extended at its leading edge. Sometimes, launching a tower and a stay system also is a good option. For attaching such additional systems, using heavy lifting equipment is a must.
Decreasing stress
The bridge structures may experience development of a lot of stress while they are being built up. For example, tensile stresses may occur in the upper and lower parts of a structure’s cross section. This may further lead to hogging and sagging of the entire bridge structures. To avoid these issues, a central pre-stressing condition needs to be developed wherein the compressive stress at all points along the structure’s cross sections is equal. Such pre-stressing can help improve the extension activities while completing the bridge structure while it is being built in incremental stages. In this way, the central pre-stressing can definitely help the workers to achieve a good quality finished state of the bridge.
Temporary structures
The longer a bridge, the more difficult it is to join its opposite halves. This is because the joining process may get hampered due to several factors. Some of these involve extreme weather conditions, shortage of equipment, shortage of manpower, etc. In such cases, a construction company can make use of strand jack lifting equipment to set up temporary structures such as piers along selective sections to give a support to the bridge structure (civildigital.com, 2017).
Along with these pointers to increase the resistance of bridge structures, there are several other aspects that need to be considered as well as implemented by businesses. These involve taking into account extreme weather conditions, providing appropriate training, taking safety measures and many more.
“The above opinions are purely a reflection of the author’s point of view. They do not reflect the position of Bygging Uddemann.”
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