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Showing 3 results for Life Prediction

H.r. Ashrafi, A.a. Ramezanianpour,
Volume 5, Issue 3 (9-2007)
Abstract

Deterioration of concrete structures in the Gulf region is a serious problem. Penetration of Chloride ion into concrete is responsible for such early deterioration. Determination of chloride diffusion coefficient is an effective way to predict the service life of concrete structures. In order to investigate the performance of concrete mixtures in such environments, ordinary and silica fume concrete mixtures containing various water to cementitious materials ratios were used. Rapid chloride permeability test and determination of diffusion coefficient of chloride ion penetration in accordance with bulk diffusion test under laboratory conditons simulated to Persian Gulf climate, and site investigation were performed. Concentration of chloride ions in various depths of concrete specimens was measured using acid soluble chloride test method. Test results show that silica fume reduces the chloride penetration and the diffusion coefficient in concrete mixtures. Different models were made for rapid chloride test results, and diffusion coefficient, of concretes maintained in the hot and corrosive environments of the Persian Gulf. The models which were calibrated with real data obtained from the concrete structures are capable to predict the penetration and service life of concrete structures in such corrosive environments.
Z.y. Wang, Q.y. Wang,
Volume 13, Issue 4 (12-2015)
Abstract

This paper presents a finite element analysis and its related experimental test of corrugated steel web beams subjected to fatigue loading. A particular focus in this study was set on the fatigue failure arising from the web-to-flange welded joint of the corrugated steel web beam. A detailed three-dimensional finite element model which explicitly includes the geometry of the web-to-flange welds along the corrugated web was developed to simulate the test corrugated web beam. The finite element model is verified by comparing with related fatigue experimental test results. The effective notch stress approach was also applied to analyse the web-to-flange welded joint replicating the local critical region in the corrugated web beam. The fatigue strength of the web-to-flange welded joint was evaluated and compared numerically by considering the stress distribution at potential fatigue crack initiation location. The fatigue life of the corrugated web beam was assessed numerically by incorporating material S-N relation and employing fracture mechanics approach. The comparison with the fatigue test results show that it is possible to expect the fatigue crack failure arising at the weld root or weld toe corresponding to the sections with reference angle using the effective notch stress analysis. The range of these predictions was evaluated by comparing with fatigue test results with accuracy and can be considered between AASHTO fatigue categories B and B’. The parametric notch stress analysis incorporating the influences of corrugation angle was performed and demonstrates it is possible to expect the fatigue crack failure arising at the weld root or weld toe. Finally, a practical solution for possible fatigue life enhancement of such structure is proposed by decreasing the corrugation angle or smoothing the intersection geometry of the corrugated web is suggested together with a moderate increase of the flange thickness.


Mohammad Reza Saberi, Alireza Rahai, Masoud Sanayei ,
Volume 15, Issue 1 (1-2017)
Abstract

Steel bridges play a very important role in every country’s transportation system. To ensure that bridges perform reliably, engineers monitor their performance which is referred to as Structural Health Monitoring (SHM). An important element of SHM includes the prediction of service life. There is ample historical evidence that bridge damage is pervasive and their life time is decreasing. To manage costs and safety, service life prediction of bridges is necessary. We present a statistical method to predict service life for steel bridges. A nonparametric statistical model based on the bootstrap method for stress analysis for fatigue life prediction of steel girder bridges is proposed. The bootstrap provides a simple approach for reproduction of the probability distribution of measured strain data. The bootstrap is sensitive to the number of events in the verification sample (data), thus we introduce a stable survival distribution function (SDF). An index is presented in this paper for inferring the service life of steel bridges, which can be known as the Life Index (µ). The life index function shows variation of the age of steel bridges under daily traffic loads. A regression model is developed which relates the service life of steel bridges using a bridge life index based on measured operational strain time histories. The predicted remaining service life derived from the model can contribute to effective management of steel bridges. The proposed method assists bridge engineers, bridge owners, and state officials in objective assessment of deteriorated bridges for retrofit or replacement of deteriorated bridges. Timely repair and retrofit increase the safety levels in bridges and decrease costs.



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