scholarly journals Effect of Water Condensate on Corrosion of Wires in Ungrouted Ducts

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7765
Author(s):  
Radoslav Ponechal ◽  
Peter Koteš ◽  
Daniela Michálková ◽  
Jakub Kraľovanec ◽  
František Bahleda
Keyword(s):  
Prestressed Concrete ◽  
Steel Wire ◽  
Limit State ◽  
Concrete Structures ◽  
Concrete Bridges ◽  
The Other ◽  
Actual State ◽  
Ultimate Limit State ◽  
Cross Sectional ◽  
Prestressing Steel

In the case of existing prestressed concrete structures, information about the actual state of prestressing is an important basis for determining their load-carrying capacity, as well as remaining service lifetime. This is even more important in the case of existing prestressed concrete bridges, which are exposed to a more aggressive environment than the other prestressed concrete structures. The level of prestressing is affected and reduced by prestress losses at a given time. In calculating the internal forces and stresses, required for the assessment of the Ultimate Limit State and the Serviceability Limit State, it is necessary to know not only the prestressing level but also the cross-sectional area of the prestressing steel (wire, strand or cable), which can change in time due to corrosion. In practice, in the case of the pre-tensioned concrete members, it has often happened in the past that cable ducts have been grouted only partially, or not at all, due to poor grouting technology. Experts did not realize what this could cause in the future—the penetration of water with aggressive agents directly into the cable duct and consequently corrosion of the prestressing steel, which means not increased protection of the steel, but rather acceleration of degradation. On the other hand, in many cases, corrosion also occurs in ducts that are not grouted and no water has entered them. This paper deals with this phenomenon—the formation of corrosion of prestressing steel in cable ducts in ungrouted ducts due to moisture. This problem was investigated experimentally and numerically in the simulation program ESP-r. Experimental measurements and numerical simulations have shown that the water vapor condenses in the cable ducts, which can subsequently cause corrosion of the prestressing steel.

The Application of CAD Technology on the Design of Reinforced and Prestressed Counterforce Wall System

2011 ◽  
Vol 214 ◽  
pp. 397-401
Author(s):  
De Ling Wang ◽  
Jiang Hai Shen
Keyword(s):  
Complex System ◽  
Finite Element ◽  
Prestressed Concrete ◽  
Computer Aided Design ◽  
Limit State ◽  
Ultimate Limit State ◽  
Finite Element Program ◽  
Prestressing Steel ◽  
Design Program ◽  
Element Program

The counterforce wall and pedestral is a complex system. Computer aided design technology is used to design and analyze this reinforced and prestressed concrete structure. Firstly CAD design program is used to design a representative wall section as a separate component. It helps doing ultimate limit state calculation and serviceability limit state checking computation. The prestress on concrete induced by prestressing steel according to construction method is also computed. Secondly, a finite element program is used to analyze the whole system. The prestress computed by CAD design program is regarded as external load. Simulation technology is also described in this paper. The stress, strain and deformation of the whole prestressed system are calculated and checked. Moreover, dynamic structural analysis is done by finite element program. Then vibration frequencies and modes can be obtained. By combining CAD design with finite element program, this complex system can be designed reasonably and effectively.

Permit checking of overloaded customized transport vehicle based on serviceability limit state reliability of concrete bridges

2020 ◽  
pp. 136943322097245
Author(s):  
Yangguang Yuan ◽  
Wanshui Han ◽  
Xin Xu ◽  
Junfeng Wang ◽  
Jianpeng Sun
Keyword(s):  
Critical Load ◽  
Prestressed Concrete ◽  
Limit State ◽  
Concrete Bridges ◽  
Ultimate Limit State ◽  
Load Effect ◽  
Serviceability Limit State ◽  
Transport Vehicle ◽  
Checking Procedure ◽  
Effect Ratio

To increase the authorization efficiency of overloaded customized transport vehicle (CTV), a serviceability limit state (SLS) reliability based permit checking method for concrete bridges is proposed through the optimization towards critical load effect ratio. In this procedure, the SLS reliability of crack width and the SLS reliability of concrete stress in tensile region are analyzed for reinforced concrete (RC) and prestressed concrete (PC) structures, respectively. The durability requirements and a unified reliable level can be concentrated reflected by the optimized critical load effect ratio. The results show that it is unreasonable to take a uniform target reliability index for all routes in permit checking of CTV, a stricter authorization criterion should be adopted for a higher expected authorization frequency. For a specific route level, a fluctuant variation of critical load effect ratio can be found with the increasing of bridge span. By introducing an ultimate limit state (ULS) based safety checking procedure, it is found that the SLS based permit checking criterion is crucial and determinative for the authorization of CTV instead of the ULS.

Probabilistic Lifetime Assessment of Prestressed Concrete Structures Exposed to Chloride Environment

2013 ◽  
Vol 378 ◽  
pp. 135-139
Author(s):  
Chun Hua Lu ◽  
Hui Li
Keyword(s):  
Prestressed Concrete ◽  
Prediction Models ◽  
Limit State ◽  
Concrete Structures ◽  
Hangzhou Bay ◽  
Chloride Ingress ◽  
Prestressing Steel ◽  
Corrosion Initiation ◽  
Definition Of ◽  
Chloride Environment

In order to study the durability behavior of marine prestressed concrete structures exposed to chloride environment, the structural service life is defined as the corrosion initiation of prestressing steel bars. For the chloride ingress in prestressed concrete, a calculated model used to predict the lifetime is developed. Based on the definition of durability limit state, a probabilistic lifetime model and its time-dependent reliability analytical method are proposed by considering the random natures of influencing factors. Then, the probabilistic lifetime prediction models are applied to a PC bridge located in Hangzhou Bay with Monte Carlo simulation. It is found that the time to corrosion initiationt0follows a lognormal distribution. With the permitted failure probability of 5.0%, it is also observed that the structural durability lifetimes are 25.6, 107.4 and 224.2 years forc=40mm,c=60mm andc=80mm, respectively.

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.

scholarly journals Corrosion Detection in PSC Bridge Tendons Using Kernel PCA Denoising of Measured MFL Signals

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 5984
Author(s):  
Chang Kook Oh ◽  
Changbin Joh ◽  
Jung Woo Lee ◽  
Kwang-Yeun Park
Keyword(s):  
Prestressed Concrete ◽  
Evaluation Method ◽  
Principal Component ◽  
Concrete Bridges ◽  
Kernel Principal Component Analysis ◽  
Cross Sectional ◽  
Measuring Device ◽  
Prestressed Concrete Bridges ◽  
Significant Damage ◽  
Non Destructive

The construction of prestressed concrete bridges has witnessed a steep increase for the past 50 years worldwide. The constructed bridges exposed to various environmental conditions deteriorate all along their service life. One such degradation is corrosion, which can cause significant damage if it occurs on the main structural components, such as prestressing tendons. In this study, a novel non-destructive evaluation method to incorporate a movable yoke system with denoising algorithm based on kernel principal component analysis is developed and applied to identify the loss of cross-sectional area in corroded external prestressing tendons. The proposed method using denoised output voltage signals obtained from the measuring device appears to be a reliable and precise monitoring system to detect corrosion with less than 3% sectional loss.

Prestressed Concrete Continuous Beam Bridge Span Arrangement and Structure Size Proposed Analytical

2014 ◽  
Vol 496-500 ◽  
pp. 2516-2519
Author(s):  
Chun Hui Dong
Keyword(s):  
Prestressed Concrete ◽  
Limit State ◽  
Steel Beam ◽  
Live Load ◽  
Cross Sectional ◽  
Bridge Span ◽  
Continuous Beam Bridge ◽  
Stress And Deformation ◽  
Beam Bridge

By analyzing the bridge structure in the course of the dead load and live load, taking into account different load safety factor for load combinations that will limit state as a result of the combination of two kinds of forces calculated tendon force estimates, estimate the various sections of the steel beam, in accordance with certain requirements of the steel beam is a good layout, construction and consider re-simulate prestress for the role of the second combination, the process of the construction and use of a cross-sectional strength checking, stress and deformation checking checking.

scholarly journals Reinforced concrete structures strengthened with CFRP (ACI x FIB) - Recommendations for bending design criteria

2022 ◽  
Vol 15 (2) ◽  
Author(s):  
Igor Del Gaudio Orlando ◽  
Túlio Nogueira Bittencourt ◽  
Leila Cristina Meneghetti
Keyword(s):  
Reinforced Concrete ◽  
Limit State ◽  
Concrete Structures ◽  
Experimental Tests ◽  
Fiber Reinforced Polymers ◽  
Design Criteria ◽  
Ultimate Limit State ◽  
Reinforced Concrete Structures ◽  
Carbon Fiber Reinforced Polymers ◽  
Model Code

abstract: This work deals with the evaluation of the design criteria and security check (Ultimate Limit State - ULS) of the American (ACI-440.2R, 2017) and European (FIB Model Code, 2010) standards of reinforced concrete structures strengthened with Carbon Fiber Reinforced Polymers (CFRP), by the technique of Externally Bonded Reinforcement (EBR). It is intended to evaluate if, for a given database of 64 experimental tests of beams and slabs, the obtained results respect the safety conditions according to the mentioned standards, to increase the efficiency of this reinforcement technique and to lead to the establishment of regulatory design criteria in Brazil. Results show a conservative match among experimental and theoretical values calculated according to the two guidelines and it is concluded that a future regulation in Brazil on this subject should be based on the FIB Model Code.

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