Effects of corrosion on degradation of tensile strength of steel bridge members

Evaluation of existing steel bridges becomes vital due to natural aging, increasing load spectra, deterioration caused by corrosion, increasing seismic demand, and other problems. In the result, bridge structures exposed to aggressive environmental conditions are subjected to time-variant changes of resistance. Corrosion becomes one of the major causes of deterioration of steel bridges and there have been many damage examples of older steel bridge structures due to corrosion around the world during past few decades. Controlling corrosion on bridge structures can prevent premature failure and lengthen their useful service life, both of which save money and natural resources, and promote public safety. Therefore, understanding of the influence of damage due to corrosion on the remaining load-carrying capacities is a vital task for the maintenance management of steel highway infrastructures. But at the moment, number of steel railway and highway bridge infrastructures in the world is steadily increasing as a result of building new steel structures and extending the life of older structures. Therefore, it would be an exigent task to measure several thousands of points, to accurately reproduce the corroded surface by numerical methods and to predict the behaviour of that corroded member more precisely. So, there is a need of more brisk and accurate assessment method which can be used to make reliable decisions affecting the cost and safety. Therefore, this paper presents the analytical results of many actual corroded steel members and comparison of them with their respective experimental results. Further, a simple and reliable analytical method by measuring only the maximum corroded depth (tc,max) is proposed, in order to predict the residual strength capacities of corroded steel plates more accurately

Prediction of Residual Buckling Strength in Corroded Steel Bridge Members

Abstract: At present, degradation process of steel bridges has become major problem in all over the world. Steel bridges are exposed to numerous degradation processes during long year operation period, which causes various types of defects. Corrosion is one of major cause of deterioration process of steel bridge structures. Because of the corrosion, remaining load carrying capacities of steel bridge structures are gradually decreased. So it is very important to carefully evaluate the remaining strength of steel bridges in order to understand the feasibility of those steel structures for the current usage and to evaluate the necessity of retrofitting of selected corroded members to strengthen the existing structures. There are lots of researches have been conducted in order to find out remaining tensile strength of corroded steel bridge members. To find out remaining buckling strength of corroded steel, previously conducted tensile test results are not accurate. So evaluation of buckling strength is an essential source of information for carrying out a comprehensive evaluation of its current buckling strength capacity and also the parameters involve in the method should be easily measurable. There is a need of more brisk and accurate assessment method which can be used to make reliable decisions affecting the cost and safety. This study proposes a new method to calculate the remaining buckling strengths by using minimum thickness ratio based on the results of many buckling strength tests conducted on specimens of corroded steel bridge plates with different corrosion conditions based on the results of many compression coupon tests of actual corroded plates. And also, it is an impossible task to predict remaining buckling strength capacities of each and every aged bridge structure by conducting experiments and so nowadays, the finite element analysis method has become the most common, powerful and flexible tool in structural analysis and makes it possible to predict the strength of complex structures more accurately than existing classical theoretical methods. Further, since it is not easy to measure several thousands of points, to accurately reproduce the corroded surface by numerical methods and to predict their buckling behaviors , a simple and reliable analytical model is proposed by measuring only the maximum corroded depth (Tc,max), in order to estimate the remaining strength capacities of actual corroded members more precisely

Analytical Study on Significance of Corroded Surface Measurement on Residual Strength Prediction

AbstractThe maintenance and safety of the existing bridges is an important concern of all highway and railroads. To assure adequate safety and determine the ongoing maintenance needs, thorough regular inspections are required. These inspections should form the essential source of information for carrying out a comprehensive evaluation of its current capacity. But the number of steel bridge infrastructures in the world is steadily increasing as a result of building new steel structures and extending the life of older structures. Most of these structures are subjected to corrosion due to environmental exposure which can reduce their carrying capacities. So, there is a need of more brisk and accurate assessment method which can be used to make reliable decisions affecting the cost and safety. In modern practices, numerical simulation is being used to replace the time-consuming and expensive experimental work and to comprehend on the lack of knowledge of mechanical behavior, stress distribution, ultimate behavior and so on. Therefore, using of numerical analysis method will give important knowledge not only for the strength estimation but also for subsequent repair and retrofitting plan. This paper presents the results of non-linear FEM analyses and compares them with their respective tensile tests of corroded plates which are obtained from a steel plate girder used for about 100 years with severe corrosion condition. Further, the effect of number of measuring points on the remaining strength estimation is studied to establish an analytical methodology to predict the residual strength capacities of a corroded steel member by measuring lesser number of points with an acceptable accuracy level

Investigation on Improvement of Low Cost NERD Slab System

The NERD center floor slab system was introduced by late Dr. A.N.S. Kulasinghe in early 1987 specially for domestic buildings which are used by middle income families in Sri Lanka. The invention of NERD system directed to identify cost effective slab construction system relative to conventional slab system and also the use of un-propped construction technique and reduction of depth of slab caused to reduce construction time and material required for construction activities. The NERD system consists with 50 mm thick in-situ concrete slab retain on trapezoidal shape pre-stressed beams which are placed by keeping 600 mm interval between each. Although, the concept of NERD system is being widely adapted in domestic building construction exposed beam under the soffit of the slab keeps away people from the use of NERD slab system. Therefore, this research has been given much more advertency to make it as flat soffit slab with the improvement of structural arrangement of the NERD system such a way that changing the shape of pre-stressed beam and thickness of in-situ concrete slab with hollow arrangement to reduce utilized concrete of the slab