Indirect Determination of Residual Prestressing Force in Post-Tensioned Concrete Beam.

Jakub Kraľovanec,Jozef Jošt,Martin Moravčík,Petra Bujňáková

doi:10.3390/ma14061338

Abstract

A diagnostic survey on the precast prestressed bridge Nižná confirmed significant deterioration due to environmental distress. Evidently, decisive failures of the structure have a similar character as in the previous precast prestressed bridge in Podbiel in the northern part of Slovakia. These failures result from the unsuitable concept of the first generation of precast prestressed concrete beams, which was used in the former Czechoslovakia in the second half of the 20th century. Subsequently, experimental verification using the proof-load test was also executed. This bridge was built in 1956, so at the time of testing, it was 60 years old. The paper presents the indirect determination of prestressing level in one precast post-tensioned concrete beam using the saw-cut method. Experimental measurement was executed during the bridge demolition. Subsequently, a 2D numerical model in ATENA 2D Software, with the assumption of nonlinear material behavior for verification of experimental results, was performed. Finally, the residual prestressing force was evaluated and compared with the expected state of prestressing according to Eurocodes after 60 years of service.

Highlights

In the early 1960s in former Czechoslovakia, the precast and prestressing technology have initiated to develop [1,2]
Decisive failures of the structure have a similar character as in the previous precast prestressed bridge in Podbiel in the northern part of Slovakia. These failures result from the unsuitable concept of the first generation of precast prestressed concrete beams, which was used in the former Czechoslovakia in the second half of the 20th century
Experimental measurement was executed during the bridge demolition

Summary

Introduction

In the early 1960s in former Czechoslovakia, the precast and prestressing technology have initiated to develop [1,2]. If it is possible to determine the ratio of the released strain (stress), for example, by using validated results of a numerical analysis or parametric study, full isolation of the concrete block is not necessary. This is especially true in cases of older bridges with a considerably low concrete covers, which limits the maximal depth of the performed saw-cuts. All of the abovementioned methods only have a negligible impact on the integrity of the concrete structure and cause local damage that can be properly repaired These techniques are generally considered as non-destructive indirect methods for determining the state of prestressing [17,18]. From an extensive failure investigation of the first generation of precast bridges in Slovakia, a precast post-tensioned bridge in Nižná was selected and is discussed in this paper

Bridge Survey

Conclusions

27. Eurocode 2: Design of Concrete Structures—Part 1–1