Tired bridges?

Research into bridge fatigue behaviour relies on RDP transducers

An important research programme to help predict the future life expectancy of masonry bridges is being conducted at the University of the West of England using load cells and LVDTs supplied by RDP Electronics.

In Britain and throughout Europe a very large proportion of the bridge stock is of masonary arch construction, built in the heyday of canal and railways era well over a century ago, when traffic movements and vehicle loading were significantly lighter than today. Predicting the projected life span and fatigue limits of these old bridges are becoming of increasing interest for bridge owners and providing material test data on the long-term behaviour of brick masonry a necessary requirement.

A research programme at the University of the West of England led by Dr Adrienn Tomor and was funded by the Engineering and Physical Sciences Research Council (EPSRC) studies the failure of representative examples of bricks for masonry arch bridges. Typical masonry types have been classified into three categories. The weakest category was widely used for the canals, were typically hand-made using locally sourced clay and varied widely in strength, even within the same bridge. By the time railways were constructed, industrial processes compacted the clay, leading to more consistent bricks, classified in the project as ‘medium’ strength. Finally, “strong” bricks are representative of today’s industrially manufactured bricks.

The main load bearing element of masonry arch bridges is the arch ring, in which the stresses can change significantly with the passing traffic. For areas with high stress concentration, long-term loading can lead to gradual deterioration of the material over time. Representative small-scale brick samples have been tested up to failure under compression and sheer within the test series, to help establish a relationship between stress levels and life excpectancy. Various RDP Electronics transducers are used in the test rigs, including RLU 5,000 kg load cells, GT 1000-L10 and GT2500RA-L10 LVDTs selected based on suitable precision, ease of installation and cost.