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1

Experiment of the monitoring prestress loss of prestressed concrete beams with damages under static loading

Wang Jinbo, Li Guodong, Lan Chunguang, Guo Nan

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

437--451

EN

In this paper, based on the feasible method and sensors for the full-scale prestressed monitor, the novel optical fiber sensors and the traditional monitoring sensors will be set up into two prestressed concrete beams with the same geometrical dimensions, material properties, and construction conditions, etc. to investigate the working state of the novel sensors and obtain the evolution law of prestress loss of the prestressed feature component under the static load. The results show that the evolution law of prestress loss of the loaded beam under the condition of no damage state and initial crack is the same as the non-loaded one; however, the prestress loss increases with the increase of time under the situation with the limit crack. The total loss of the prestressed beam with the limit crack is 36.4% without damage. The prestress loss of the prestressed beam under the static load increase with the development of the crack (injury).

2

Evaluation of time dependent prestress losses in pretensioned concrete member with top and bottom tendons

Parkhats Vadzim, Krzywoń Rafał

Architecture Civil Engineering Environment

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2019

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Vol. 12, no. 3

105--112

EN

Prestress losses are usually calculated by bringing the tendons in the cross-section to the single resultant tendon. This solution is correct only for tendons concentrated in one part of the cross-section, while with their wider distribution, for example after the use of upper tendons, it may result in underestimation of losses in the lower tendons and overestimation in the upper tendons. The paper presents formulae to determine time dependent prestress losses separately for the top and bottom tendons of a pretensioned concrete member. Furthermore, variations of stress in the prestressing steel are analysed for two pretensioned concrete members to evaluate the possibility of using the equation (5.46) from the Eurocode 2 for the resultant tendon instead of the deduced formulae. The aim of this study is to show how great the error of estimated loss of prestressing force on the basis of several typical prestressed concrete sections can be.

3

Pre-stress losses in FRP pre-stressed reinforced concrete – subject overview

Przygocka M., Kotynia R.

Archives of Civil Engineering

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2018

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Vol. 64, nr 4/II

257--268

EN

This paper discuss the issue of pre-stress losses which occur in the FRP prestressed concrete structures. The prestress losses consist of immediate losses just after pre-tensioning of the FRP composite and time-dependent losses. Prestress losses are affected by different factors as strength properties of used materials, ambient temperature, humidity, UV radiation, bond between the FRP material and RC specimen, type of anchorage and creep of prestressing system. Two types of tests can be found in the available literature: material samples subjected to sustained uniaxial tension which verify the relaxation of FRP tendons (Wang et al., Sasaki and Nishizaki, Shi et al and Oskouei and Taleie) and flexural tests of RC beams strengthened with pre-tensioned FRPs (Wang et al.). Authors considered different types of composites: carbon (Wang et al, Sasaki and Nishizaki, Oskouei and Taleie), aramid (Sasaki and Nishizaki, Oskouei and Taleie), glass (Sasaki and Nishizaki), vinyl (Sasaki and Nishizaki) and basalt (Shi et al.).

4

Analiza opóźnionych strat sprężenia w konstrukcjach z betonu

Dyduch K.

Inżynieria i Budownictwo

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2016

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R. 72, nr 3

128--130

PL

Omówiono zasady obliczenia strat reologicznych w betonowym przekroju sprężonym według PN-EN 1992-1-1 oraz wpływu przekroju zbrojenia pasywnego na określenie efektywnych sił sprężających w betonie. Podano tok postępowania przy obliczaniu wpływu etapowego sprężenia i dodatkowo występujących obciążeń stałych na straty reologiczne w przekroju sprężonym (belka strunobetonowa doprężana kablami w kolejnych fazach powiększania obciążeń stałych).

EN

EC-2 rules for calculation the prestress looses as well as the method of taking into consideration an passive reinforcement in calculation of effective prestress force in concrete cross-section are presented. Additionally, calculation procedure for estimation of influence of step by step prestressing and additional dead loads on rheological prestress force loses (pre-tensioned beam post-tensioned step by step with the increase of dead load).