Present traffic conditions across London's historic Tower Bridge had increased in both frequency and weight, causing wear and misalignment that also meant that the draw-bridge style decks are not properly locked down anymore.
Monitoring the Load
If left unresolved, additional damage would result in a major shutdown for repairs on what is a busy route into the capital city. In order to resolve this issue, an ABB load monitoring solution was installed to continuously measure the load across the bridge decks.
If an imbalance was detected, the load cells would activate an adjustment to retain equal loads across the deck bearings which lowers wear and, eventually, increases the bridge’s working life.
A Weighty Problem
The central 200 foot roadway span of London's Tower Bridge opens draw-bridge style to enable shipping to pass by the busy River Thames. Each deck weighing more than 1,000 tons pivots on main bearings accommodated in the towers as they are lowered and raised.
However, these bearings were adversely affected by heavier vehicles and increased amounts of traffic, which resulted in wear and misalignment as some took on more load than others. It also meant that the bridge decks were not accurately engaged when locked down. If this issue is not resolved, the damage would continue and lead to closure of the bridge for major repairs.
Balancing the Load
To overcome the problem, the old stationary resting blocks for the decks were replaced with active ones capable of movement. ABB Millmate Pressductor load cells were then housed in each of the new blocks to continuously measure the load across the bridge decks and, most importantly, to relay load data to a PLC (programmable logic control) system. If the PLC detected an imbalance in weight, it would activate hydraulic cylinders to adjust the position of the resting blocks.
This action retains equal loads across the deck bearings at all times, helping to increase their life as well as the life of the overall bridge structure.
Installing ABB's continuous load monitoring system avoided the need to shut down a major bridge for repairs and extended the life of the bridge structure.
This information has been sourced, reviewed and adapted from materials provided by ABB Measurement & Analytics.
For more information on this source, please visit ABB Measurement & Analytics.