Monday, 26 September 2016

Detecting Damage on Bridge Structures Using Inclinometers

Hello Everybody,

I have been developing a new bridge Condition Assessment (CA) concept recently that I would like to share with you through this post. The idea is about detecting any possible anomalies involved in bridge structural condition using rotation as a main parameter. To achieve so, I conducted the below mentioned studies.

I developed an algorithm, which employs the Influence Line and the Moment Area theorems, to study the sensitivity of rotation to detect change in structural stiffness of a bridge structure under moving load. The algorithm calculates the rotation recorded along the length of a simply supported beam structure while load is moving. It also simulates damage at any point across the structure in terms of reduction in stiffness. The figures provided below depicts the results obtained from the aforementioned study.

Figure 1. Rotation recorded at the left end of a beam structure under moving load

Figure 2. Difference in rotation between healthy and damaged cases

Figure 1 shows the rotation recorded at left end (x=0) of a beam structure while load is moving from one end to another. 15% damage was also simulated in the study at midspan of the beam and blue plot shows the healthy and red plot the damaged cases. Figure 2 shows the difference between two plots where peak of the graph matches with the damage location and its magnitude represents the severity of the damage. From this study the required resolution of a sensor (inclinometer) was determined as 10^-3 radians to detect 15% stiffness loss on a beam structure. Following this, I made an extensive research about inclinometer sensors available in the market. It was a challenging task to find a high resolution sensor which is also cost efficient. Eventually, I came up with an idea of using accelerometers to record rotation. The idea was tested on a bridge structure available in the Structures Laboratory at the University of Exeter. The inclinometers were placed horizontally on the structure and recorded accelerations while loaded trolley were manually pulled (8 runs) from one end to another. Because the output of the accelerometer obeys a sinusoidal relationship as it is rotated through gravity, the inverse sine function of it converted recorded acceleration to rotation (angle). The idea worked well and 10-6 radians resolution was obtained.

Figure 3. 15m long bridge structure available in the Structures Lab at The University of Exeter

Figure 4. Rotation time history obtained using accelerometers under loaded trolley

The findings obtained from the above mention numerical analysis are promising to detect any possible damage involved in structural condition of a bridge structure. The idea is still being developed. I built up a 3m long simply supported beam structure in the lab and will test the concept experimentally. I look forward to sharing the results through upcoming posts.

Figure 5. 3m long, simply supported beam structure built in the lab.
Stay tuned!

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!

Saturday, 2 April 2016

Introduction to my blog

Hello Everyone and welcome to my blog! 

My name is Farhad Huseynov and I am a Structural Engineer mainly specialized in Bridge Engineering. Currently I am working as an Early Stage Researcher (ESR 7) for Full Scale Dynamics LTD in Exeter, UK and have been involved in research project named "Railway Weigh-in-Motion for Bridge Safety" which is part of the Marie Sklodowska - Curie ITN Project "TRUSS" funded by the European Union under the Horizon 2020. At the same time I am a PhD student in Civil Engineering Department at the University College Dublin (UCD). Throughout this social media platform I will regularly share my social and professional activities that I hope you will enjoy while reading.

As a first blog entry, a brief description about myself and my research topic would be a good idea to start with...

So, I am 29 years old and was born in Baku, capital city of the Republic of Azerbaijan. It is a small yet culturally rich country in the Caucasus region, situated at the crossroads of Eastern Europe and Western Asia and also known as a Land of Fire (Odlar Yurdu) that some of you might have already noticed the phrase on Atletico Madrid's shirts as of 2012 :)

Lovely view of Baku taken from the Mountain Park

I obtained my BSc degree in Civil Engineering from the Middle East Technical University (METU) in Ankara, Turkey and MSc degree in Structural Engineering from The University of Sheffield in Sheffield, UK and graduated with distinction in 2009 and 2012, respectively. During my MSc degree I worked on a dissertation topic named "Finite Element Modelling of Bosporus Suspension Bridge", the bridge that crosses the Bosporus strait in Istanbul and connects two continents, Europe and Asia. Since then I am fascinated with design and analysis of bridge structures. Hence, after graduation I started working as a Bridge Design Engineer for an industry leading company in Turkey, particularly in Istanbul, and had a chance to design around 30 bridges all over that region before I joined TRUSS. 
Illuminated view of Bosporus Suspension Bridge. Istanbul, Turkey

After gaining extensive bridge design experience now I have been involved in a research project that aims to develop a Structural Performance Monitoring technique for bridges that is cost efficient, practically applicable, and provide higher confidence in estimating the performance condition of the applied bridge structure. The main task behind the proposed research study is to reduce the uncertainties (e.g traffic/railway loading) involved in bridge assessment and to 'measure' quantitatively the performance of a bridge structure using Virtual Instrumentation (VI) concept. VI is a simple concept that integrates the field monitoring tests with a physics based model. It uses deformations (in terms of displacement) obtained from a few installed instruments as a load on a calibrated/updated 3-D FE model to accurately predict the pertinent response of a bridge structure.

The proposed research idea is to first develop an appropriately detailed 3-D FE model of a bridge and calibrate/update it using deformations obtained from intense field tests. Later the final model will be integrated with continuous monitoring system to calculate the stresses and deformations across the whole structure i.e. non-instrumented locations. This concept will also be used to estimate the traffic/railway loading which is the main source of uncertainties involved in bridge assessment. Directly measured or recorded  train/vehicle load and bridge responses will be used to characterise the bridge structure. Later so called Moving Force Identification (MFI) techniques will be applied to estimate the load of a passing train/vehicle.

Currently I am running a test at one of the bridges in Exeter and will update you soon with the results. Hope to see you all again next time!

Stay tuned!