Abstract

The aim is the prediction of the failure time of prestressed concrete beams under low cyclic load. Since the experiments last long for low load, accelerated failure tests with higher load are conducted. However, the accelerated tests are expensive so that only few tests are available. To obtain a more precise failure time prediction, the additional information of time points of breakage of tension wires is used. These breakage time points are modeled by a nonlinear birth process. This allows not only point prediction of a critical number of broken tension wires but also prediction intervals which express the uncertainty of the prediction.

Highlights

  • The assessment of existing prestressed concrete bridges by means of recalculation in conjunction with rehabilitation and strengthening is gaining more and more importance compared to the construction of new bridges

  • The relation between the increasing stress on the gradually breaking wires and the waiting time is adequately modeled by this function as it tends to infinity for a stress near 0 and fits the majority of observed waiting times

  • The two proposed methods for predicting the failure time of prestressed concrete beams are based on predicting the time when a critical number of tension wires is broken

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Summary

Introduction

The assessment of existing prestressed concrete bridges by means of recalculation in conjunction with rehabilitation and strengthening is gaining more and more importance compared to the construction of new bridges. The current design codes had been developed over decades always adapting new design approaches that are current at that time Even for this reason the recalculation of older existing structures often leads to deficiencies concerning load-bearing capacity, durability, and resistance against fatigue. For the design of new bridges against fatigue or the assessment of existing bridges by means of recalculation, S-N curves are needed. The latter describes the fatigue resistance of the materials. There is a great need to optimize these tests procedures

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