Prestress Loss Calculations: Another Perspective

PCI Journal ◽  
2016 ◽  
Vol 61 (3) ◽  
Author(s):  
David B. Garber ◽  
José M. Gallardo ◽  
Dean J. Deschenes ◽  
Oguzhan Bayrak
Keyword(s):  
Prestress Loss

scholarly journals A Stress Measurement Method for Steel Strands Based on LC Oscillation

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Dongjun Chen ◽  
Benniu Zhang ◽  
Xingxing Li ◽  
Chong Tu ◽  
Can Yuan ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Oscillation Frequency ◽  
Stress Measurement ◽  
Resonant Circuit ◽  
Electromagnetic Signal ◽  
Prestress Loss ◽  
Factors Affecting ◽  
Existing Structures ◽  
Detection Circuit ◽  
Frequency Meter

The prestress loss is one of the main factors affecting the safety of prestressed concrete structure. While the detecting signals like sound and light are difficult to spread in steel strands, there is no effective method for prestress detection of the bonded prestressed steel strands in existing structures yet. In this paper, taking into consideration that the electromagnetic oscillation characteristic can make the signal propagate effectively on the bonded prestressed steel strands, a nondestructive prestress detection method based on the electromagnetic effect to detect oscillation frequency is proposed. In a detection circuit, the steel strands are simulated as an inductance component, in which an induced electromagnetic signal passes through the steel strands to form resonance. And then, a frequency meter is used to detect the oscillation frequency of the resonant circuit. The oscillation frequency is supposed to have relationship with the prestress loading on the steel strands. A section of steel strands with a length of 1.2 m is adopted to test the correlation of stress and oscillation frequency. Both the theoretical and experimental results show that the resonant frequency of the circuit decreases with the increase of the stress of the strand and is linear in a certain range.

scholarly journals EM-Based Monitoring and Probabilistic Analysis of Prestress Loss of Bonded Tendons in PSC Beams

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Zheheng Chen ◽  
Shanwen Zhang
Keyword(s):  
Probabilistic Analysis ◽  
Prestressed Concrete ◽  
Monitoring Methods ◽  
Prestress Loss ◽  
External Tendons ◽  
Material Environment ◽  
Key Factor ◽  
One Year

The prestress level is a key factor of prestressed concrete (PSC) beams, affecting their long-term serviceability and safety. Existing monitoring methods, however, are not effective in obtaining the force or stress of embedded tendons. This paper investigates the feasibility of elastomagnetic (EM) sensors, which have been used for external tendons, in monitoring the long-term prestress loss of bonded tendons. The influence of ambient temperature, water, eccentricity ratio, plastic duct, and cement grouts on the test results of EM sensors is experimentally examined. Based on the calibrated EM sensors, prestress loss of a group of PSC beams was monitored for one year. In order to further consider the high randomness in material, environment, and construction, probabilistic analysis of prestress loss is conducted. Finally, the variation range of prestress loss with a certain confidence level is obtained and is compared with the monitored data, which provides a basis for the determination of prestress level in the design of PSC beams.

Prestress Loss Measurements in Missouri's First Fully Instrumented High-Performance Concrete Bridge

2005 ◽  
Vol 1928 (1) ◽  
pp. 118-125 ◽  
Author(s):  
Yumin Yang ◽  
John J. Myers
Keyword(s):  
Prestressed Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Concrete Bridge ◽  
Prestress Loss ◽  
Prestress Losses ◽  
Concrete Girders ◽  
Allowable Stresses ◽  
Loss Estimate

Prestress losses have a direct impact on concrete stress development and deflection behavior of highway bridge members. A poor estimate of prestress losses can result in a structure in which allowable stresses are exceeded or camber and deflection behavior is poorly predicted, such that the serviceability of a structure may be adversely affected. This paper reports the prestress losses observed throughout fabrication, shipment, erection, and the first 2 years of service for the first high-performance superstructure concrete bridge in Missouri. The prestress losses investigated included prerelease losses, elastic shortening losses, relaxation losses, creep losses, and shrinkage losses. Results from the study were compared with eight commonly used loss estimate models for total prestress losses, including AASHTO and Prestressed Concrete Institute methods. Recommendations were proposed by the authors for the most appropriate methodology to use to predict prestress losses in high-strength concrete girders accurately.

Pertes de charge des ancrages actifs injectés dans un massif rocheux

1989 ◽  
Vol 16 (1) ◽  
pp. 72-81 ◽  
Author(s):  
Brahim Benmokrane ◽  
Gérard Ballivy
Keyword(s):  
Epoxy Resin ◽  
Field Study ◽  
Key Words ◽  
Solid Rock ◽  
Rapid Loss ◽  
Prestress Loss ◽  
Massif Rocheux ◽  
Second Stage ◽  
Initial Stage

Estimation of loss of prestress is an essential part of the design of permanent or temporary prstressed anchors since stability of the retained structure must not be compromised. Findings of a field study on long-term behaviour of prestressed anchors are presented herein: different lengths of anchors in solid rock were injected with cement grout or epoxy resin. Load variation in the anchors with time indicated two distinct stages of loss of prestress: an initial stage of rapid loss of prestress and a second stage of very minor and uniform loss ending about 6 months after prestressing. Our study also showed that restressing anchors after a period of time reduces subsequent prestress loss and that overdimensioning of the injected length does not. Key words: rock, prestressed injected anchor, grout, loss of prestress, creep, relaxation.

Feasibility Study of Prestress Force Prediction for Concrete Beams Using Second-Order Deflections

2018 ◽  
Vol 18 (10) ◽  
pp. 1850124 ◽  
Author(s):  
Marco Bonopera ◽  
Kuo-Chun Chang ◽  
Chun-Chung Chen ◽  
Yu-Chi Sung ◽  
Nerio Tullini
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beams ◽  
Flexural Rigidity ◽  
Beam Theory ◽  
Concrete Bridges ◽  
Prestress Loss ◽  
Prestressed Concrete Bridges ◽  
Loss Prediction ◽  
Euler Bernoulli Beam ◽  
Post Tensioned

The safety and sustainability of prestressed concrete bridges can be improved with accurate prestress loss prediction. Considerable loss of the prestress force may imply damages hidden in the bridge. In this study, a prestress force identification method was implemented for concrete beams. Based on the Euler–Bernoulli beam theory, the procedure estimates the prestress force by using one or a set of static displacements measured along the member axis. The implementation of this procedure requires information regarding the flexural rigidity of the beam. The deflected shape of a post-tensioned concrete beam, subjected to an additional vertical load, was measured in a short term in several laboratory experiments. The accuracy of the deflection measurements provided favorable prestress force estimates. In particular, the “compression-softening” theory was validated for uncracked post-tensioned concrete beams.

Sign in / Sign up

Export Citation Format

Share Document