Prestressed concrete pressure pipes, cylinder and non-cylinder, including joints, fittings and specific requirement for prestressing steel for pipes

2015 ◽  
Keyword(s):  
Prestressed Concrete ◽  
Specific Requirement ◽  
Prestressing Steel ◽  
Pressure Pipes

A new steel anchorage system for post-tensioning applications using carbon fibre reinforced plastic tendons

1998 ◽  
Vol 25 (1) ◽  
pp. 113-127 ◽  
Author(s):  
Ezzeldin Y Sayed-Ahmed ◽  
Nigel G Shrive
Keyword(s):  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Fatigue Tests ◽  
Direct Tension ◽  
Element Analysis ◽  
Prestressing Steel ◽  
Reinforced Plastics ◽  
Anchorage System ◽  
Post Tensioning ◽  
Post Tension

During the past half century, the use of prestressing in different structures has increased tremendously. One of the most important techniques of prestressing is post-tensioning. The main problem associated with post-tensioning in different structures is the corrosion of the prestressing steel tendons even with well-protected steel. New materials, fibre reinforced plastics or polymers (FRP), which are more durable than steel, can be used for these tendons/strands and thus overcome the corrosion problem. However, different shortcomings appear when FRP tendons are introduced to post-tensioning prestressing applications. For carbon fibre plastic tendons (CFRP), there is no suitable anchorage system for post-tensioning applications. Some of the anchorages developed by others for use with FRPs are therefore described and assessed. A new anchorage system developed by the authors, which can be used with bonded or unbonded CFRP tendons in post-tensioning applications, is described. The results of direct tension and fatigue tests on CFRPs anchored with the new system are presented.Key words: anchorage system, cyclic loading, fatigue, fibre reinforced plastics, finite element analysis, post-tension, prestressed concrete, prestressed masonry, strands, tendons.

scholarly journals Detection, Protection, Repair and Rehabilitation of Corroded Prestressed Concrete Structures

2021 ◽  
Author(s):  
Md Khorshed Alam Khan
Keyword(s):  
Mild Steel ◽  
Prestressed Concrete ◽  
Chloride Ions ◽  
Steel Reinforcement ◽  
Cross Sectional Area ◽  
Cold Climate ◽  
Tensile Failure ◽  
Sectional Area ◽  
Cross Sectional ◽  
Prestressing Steel

Corrosion is a natural and unavoidable process and its control is a global challenge. The civil engineers of 21st century are facing a major problem for corrosion of prestressed concrete as they maintain an aging infrastructure. It affects various public and private economic sectors including infrastructure, transportation, production, manufacturing and utilities. Corrosion of prestressing steel is much more severe than corrosion of mild steel reinforcement. This is due to higher strength of the prestressing steels, and the high level of stressing in the steel. Usually prestressing steels are stressed about 70%-80% of their ultimate strength which is much lower in mild steel reinforcement. The loss of cross-sectional area of the reinforcing steel due to corrosion is likely lead to tensile failure. The cross-sectional area of prestressing steel is less than mild steel reinforcement due to its higher strength. As a result, the loss of one prestressing strand or bar will have a tremendous effect on the capacity of the member than the loss of an equivalent size mild steel bar. The corrosion of prestressing steel in concrete is an electrochemical reaction that is influenced by various factors including chloride-ion content, pH level, concrete permeability, and availability of moisture to conduct ions within the concrete. Normally steels in concrete are protected from corrosion by a passive film of iron oxides resulting from the alkaline environment of the concrete. For the corrosion process to be initiated, the passive oxide film on the prestressing steel must be destroyed. Passivation of the steel may be destroyed by the carbonation or by the presence of the chloride ions. In Canada, one of the reasons of this problem is due to the huge amount of deicing chemicals to combat the cold climate. Once corrosion occurs, the corrosion products occupy up to six times as much volume as steel, leading to cracking and disruption of the concrete. The ACI limit on chloride in prestressed concrete members is half of that for conventionally reinforced concrete. Prestressing steel is also more inclined to other forms of corrosion related deterioration that do not occur in mild steel reinforcement. These forms are stress corrosion cracking, hydrogen embrittlement, fretting fatigue and corrosion fatigue. These types of deterioration are very difficult to detect, and can lead to brittle failure with little or no sign of warning. This report presents the mechanisms, causes and effects of corrosion in North American design and construction and the proper detection and protection systems.

Prestressing Steel Ropes - Corrosion Impact on its Properties

2020 ◽  
Vol 309 ◽  
pp. 272-280
Author(s):  
Jiří Kolísko ◽  
Vítězslav Vacek ◽  
Petr Pokorný ◽  
Michaela Kostelecká
Keyword(s):  
Maraging Steel ◽  
Prestressed Concrete ◽  
Mechanical Characteristics ◽  
Concrete Structures ◽  
Steel Reinforcement ◽  
Prestressing Steel ◽  
Anticorrosion Protection ◽  
Long Time ◽  
Prestressed Reinforcement ◽  
Prestressed Structures

Steel reinforcement made of refined maraging steel in the form of wires and tendons has been for a long time used commonly for reinforcement of prestressed concrete structures. Defects on some of them and unfortunately even accidents of some cases of bridge objects, mainly recently published by media, related to corrosion of prestressed reinforcement awoke interest of both professional and wide non-professional public related to its durability. This issue also opens up a question of durability and liability of prestressed structures. In majority of existing prestressed structures the anticorrosion protection of reinforcement was traditionally secured mainly by alkalinity of the environment, i.e. concreting and/or grouting of prestressed elements in ducts. The abstract presents information related mainly to mechanical characteristics of corrosion-affected prestressed elements.

scholarly journals Assessment of Mechanical Properties of Corroded Prestressing Strands

2020 ◽  
Vol 10 (12) ◽  
pp. 4055 ◽  
Author(s):  
Chi-Ho Jeon ◽  
Cuong Duy Nguyen ◽  
Chang-Su Shim
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Prestressed Concrete ◽  
Critical Issue ◽  
Concrete Bridges ◽  
Structural Behavior ◽  
Maximum Deformation ◽  
Prestressing Steel ◽  
External Tendons ◽  
Governing Factor

The corrosion of prestressing steel in prestressed concrete bridges is a critical issue for bridge maintenance. To assess structures with corroded strands, it is necessary to define the mechanical properties of the strands and their influence on the structural behavior. In this study, corroded strands were taken from external tendons in existing post-tensioned concrete bridges and tested to determine the effects of corrosion on their tensile properties. Empirical equations for the tensile strength and ductility of the corroded strands were proposed using test results. The most corroded wire governs the mechanical properties of the strand. Experiments on prestressed concrete beams with a single corroded strand were conducted to investigate their structural behavior. A reduction in the flexural strength and maximum deformation was observed in these experiments. According to the section loss of a wire in a strand and its location in a beam, the flexural capacity can be evaluated using the proposed equation. The reduced ultimate strain of the corroded strand can be the governing factor of the flexural strength.

Reliability-Based Assessment of Flexural Strength of High-Speed Rail PC Box Beam in Marine Environment

2013 ◽  
Vol 405-408 ◽  
pp. 678-683
Author(s):  
Zhao Hui Lu ◽  
Hai Li ◽  
Yan Gang Zhao
Keyword(s):  
Flexural Strength ◽  
Marine Environment ◽  
Prestressed Concrete ◽  
High Speed ◽  
High Speed Rail ◽  
Prestressing Steel ◽  
Box Beam ◽  
Maintenance And Rehabilitation ◽  
Structural Engineers ◽  
Asset Managers

This paper examines the effect of pitting corrosion of prestressing steel strands on flexural strength of prestressed concrete (PC) beams in marine environment. A reliability-based methodology for the prediction of time to structural failure after corrosion initiation was proposed and probabilities of failure are evaluated using FORM as exampled by a high-speed rail PC box beam. The methodology presented in this paper can be used as a tool for structural engineers and asset managers to assess a corrosion-affected concrete infrastructure and make decisions with regard to its maintenance and rehabilitation.

Fatigue reliability of deteriorating prestressed concrete bridges due to stress corrosion cracking

2001 ◽  
Vol 28 (4) ◽  
pp. 673-683 ◽  
Author(s):  
M A Maes ◽  
X Wei ◽  
W H Dilger
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Prestressed Concrete ◽  
Corrosion Cracking ◽  
Concrete Bridges ◽  
Concrete Bridge ◽  
Fatigue Reliability ◽  
Prestressing Steel ◽  
Prestressed Concrete Bridges ◽  
Prestressed Concrete Bridge

In this paper, an analysis framework is presented to develop a relationship between fatigue reliability in a prestressed concrete bridge and the progress of stress corrosion cracking (SCC) in prestressing steel. The fatigue limit state uses a cumulative damage model for prestressing steel wires, which is a function of both stress range and minimum stress. The SCC model takes into account varying degrees of material susceptibility, stress regimes, and environmental conditions and is structured around three stages: initiation of micro-cracking, propagation, and macro-crack instability using linear elastic fracture mechanics. The framework is an overall time-dependent analysis of the safety against fatigue of a prestressed concrete bridge. It involves a stochastic analysis of the evolution of prestressing wire corrosion as a function of time and a time-dependent probabilistic analysis of the fatigue reliability of the prestressed concrete bridge suffering a certain degree of deterioration. The uncertainties involved in the fatigue model, the SCC model, and traffic actions are considered. The updating of uncertainties is simplified by considering a limited number of classes representative of the severity of SCC exposure. The framework is applied to three deteriorating highway bridges.Key words: fatigue analysis, prestressing strands, stress corrosion cracking, reliability assessment, prestressed concrete bridges, deterioration.

Sign in / Sign up

Export Citation Format

Share Document