The Exe North Bridge (Figure 1) is one of the two almost identical adjacent bridges crossing River Exe and forming a big roundabout in Exeter, UK. It is 60m long and consists of three spans, resting on two wall type pier structures in the river and abutments at the ends. It was constructed in 1969, so it is very close to its 50 years of designed service life.
The Vibration Engineering Section supported The University of Exeter undergraduate engineering student project “Analysis of transverse load distribution of Exe North Bridge superstructure”.
The north span of the test structure was instrumented with 12 strain transducers, which made it possible to study the load shedding characteristics of the deck structure under moving load. As a test vehicle, a four-axle, 32 tonne lorry was used to obtain a quasi-static strain response. The load test was performed overnight to avoid disturbing traffic. The truck made several passes in each lane, stopping every time for 30-45 seconds to record static strain (Figure 2.).
The load test revealed that, although the structure is nearing its 50 years of designed life, it still retains significant strength reserves.