This necessitates widening of the pier foundations, the piers and pier caps, as well as the bridge deck to counter the additional imposed load on these members. The ever-increasing traffic on highways has resulted in their widening from two to four to six lanes and therefore bridges too need expanding to avoid creating bottlenecks. Cleaning of the hole is an often-overlooked aspect that can be eliminated with hollow-drill bits attached to vacuum cleaners that suck out the dust while drilling. The conventional reinforced concrete technique involves anchoring new steel reinforcement bars into the existing section (foundations, piers, pier caps, or the bridge deck) by drilling and cleaning holes, injecting a highly viscous resin mortar, and finally inserting the rebar. This technique does not need any formwork and can retrofit large areas, albeit with much wastage of materials and a rough, often unsightly, finish. The shotcrete technique involves anchoring a wire mesh onto the existing concrete and pneumatically spraying it with concrete. One retrofitting option is concrete jacketing, which involves augmenting the size of the existing concrete section by either sprayed concrete (shotcrete) or conventional reinforced concrete. Once the assessment is made, a choice of retrofitting certain components with specific solutions can be undertaken analytically and then executed at site.
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Although destructive testing should be limited where possible, all testing methods at their core assess the material’s residual strength, as well as the bridge’s deflection, internal cracking, and stress levels. The first step in the rehabilitation process is the health monitoring, achieved by visual inspections and destructive and non-destructive testing methods, particularly where drawings are unavailable.
#Hilti anchors for splays to concrete Patch#
Current solutions to remediate and retrofit bridges are exclusively post-installed in nature, such as external pre-stressing, metal plate bonding, concrete jacketing, concrete overlay, crack injection, and patch repair, amongst others, are very common. To counter these numerous challenges and extend a bridge’s service life is no easy task and requires not one but a combination of multiple solutions that tackle all defects. Defects arising due to fatigue are inevitable and revealed through cracking, excessive deflection, spalling, corroded reinforcement or steel members, and loss of pre-stress, amongst others. This has allowed certain bridges, such as the iconic Forth Bridge in Scotland, to last over 125 years since its construction.Ī typical bridge is subjected regularly to dynamic vehicular loads and continual weathering effects during its service life, leading to fatigue in its constituent materials.
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Breathing a second life into vital bridges is possible if maintenance is regular, restrictions are placed on speed limits, overloaded lorries are restricted, and, most importantly, rehabilitation efforts are undertaken. Collapse of the Majerhat Bridge in Kolkata is not an isolated incident and serves as a reminder that bridges, like buildings, have a certain lifespan. Extending the lifespan of these vital capillaries to withstand ever-heavier loads requires effective and efficient solutions to their rehabilitation. Forming the spine of a growing economy, India has an extensive network of bridges and roads, with a huge investment push not just to build and extend the network but also maintain and repair those approaching the end of their service life.