Monday, 8 August 2016

Case Study: Analysis of Transverse Load Distribution Characteristics of Exe North Bridge

Hello Everybody,

     It has been quite a while I haven't been updating my blog!!! I was busy organizing a field test on one of the bridges in Exeter, UK which I would like to share with you over this blog post. 

     The test was performed on the Exe North Bridge (Figure 1) which 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.

Figure 1
Figure 1. Exe North Bridge spanning the River Exe

     The north span of the test structure was instrumented with 12 strain transducers (Figure 2 & 3), 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 (Figure 4). 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 (Video 1).

Figure 2. Strain sensors installed on the soffit of the deck structure.


Figure 3. Me installing strain transducers on the deck soffit.


Figure 4. 32 tonne, 4-axle lorry remaining stationary over the bridge to record static strains.

Video 1. 

The test was supported by Full Scale Dynamics Limited where I am employed and The Vibration Engineering Section from The University of Exeter within the scope of undergraduate engineering student project "Analysis of transverse load distribution of Exe North Bridge superstructure". The purpose of the test was to study the load shedding characteristics of the structure as well as to showcase the importance of field testing in efforts to deal with the deteriorating infrastructure. The load test revealed that, although the structure is nearing its 50 years of designed life, it still retains significant strength reserves. Further findings about the test was presented on a conference paper in 6th Civil Structural Health Monitoring (CSHM-6) workshop in Belfast, UK [1].

Figure 5. Phd student Zandy Muhammed (left) from The University of Exeter and Me (right) supervising the undergraduate student Nick Trump (middle).

Stay tuned!
Farhad.