Optical Sensor Developments for Measuring the Surface Strains in Prestressed Concrete Members

Wu, Chih-Hang John; Zhao, Weixin; Beck, Terry; Peterman, Robert J.

doi:10.1111/j.1475-1305.2009.00621.x

Cited by 12 publications

(5 citation statements)

References 11 publications

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“…9 depicts both the instantaneous and time-dependent prestress losses for all the specimens tested, including the prestress losses from specimen strains, the prestress losses from the measured prestressing forces, and the adjusted values of the prestress losses according to Eq. (7). As observed, the actual prestress losses can be estimated from the measured prestressing…”

Section: 2)mentioning

confidence: 71%

“…The experimental techniques used to determine prestress losses include several typologies [4][5][6][7]: 1) monitoring longitudinal concrete strains over time at the level of the center of gravity of the prestressing reinforcement; 2) load testing to determine crack initiation and/or crack reopening loads to obtain the available compressive stress in the bottom flange of a member; 3) severing the prestressing reinforcement by cutting it into a representative exposed length after placing strain gauges on the reinforcement; 4) relating the tension in the prestressing reinforcement to the vertical deflection recorded when known weights are suspended from it on a representative exposed length; and 5) determining the side pressure to close the induced crack in a small cylindrical hole drilled in the bottom flange of a member.…”

Section: Introductionmentioning

confidence: 99%

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Prestress losses evaluation in prestressed concrete prismatic specimens

Caro

Martí‐Vargas

Ros

2013

Engineering Structures

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This paper presents an experimental research work to evaluate prestress losses in pretensioned 12 prestressed concrete. An experimental program including variables such as concrete mix 13 design, specimen cross-section size and concrete age at the prestress transfer was carried out. 14 Several pretensioned prestressed concrete prismatic specimens were made and tested using 15 the ECADA+ test method, based on measuring prestressing reinforcement force. In addition, 16 specimens were instrumented to obtain the longitudinal concrete strains profiles at any time. 17Measurements from both techniques were taken over one year. Measured prestress losses 18 included elastic shortening losses and time-dependent losses due to concrete shrinkage and 19 creep. A coefficient to account for the relationship between the prestress losses from the 20 measured prestressing forces and the actual prestress losses from concrete compressive strains 21 is proposed. The experimental results were compared with the predicted prestress losses using 22 methods from several codes. 23 Keywords 24Concrete, pretensioned, prestress loss, creep, shrinkage, transfer, strain 25 26 2

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Section: 2)mentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Prestress losses evaluation in prestressed concrete prismatic specimens

Caro

Martí‐Vargas

Ros

2013

Engineering Structures

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“…Recent experiments have been conducted using an optical strain sensor [17]. However, conventionally strain gauges are attached along the sides of the concrete member prior to release [8].…”

Section: Existing Experimental Methodsmentioning

confidence: 99%

“…The second method consists in the analysis of the strain profiles on the concrete specimen surface after the prestress transfer versus the distance to the end. Recent experiments have been conducted using an optical strain sensor [17]. However, conventionally strain gauges are attached along the sides of the concrete member prior to release [8].…”

Section: Existing Experimental Methodsmentioning

confidence: 99%

Experimental Technique for Measuring the Long‐term Transfer Length in Prestressed Concrete

Martí‐Vargas¹,

A.²,

Ros³

2012

Strain

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This paper presents a proposal of a test setup and methodology for testing the transfer length evolution through time of prestressing reinforcement in pretensioned prestressed concrete members, aimed at providing a basis for standardization. The proposed test method is based on the instantaneous and time-related analysis of the prestressing reinforcement force profile at only one end of a pretensioned prestressed concrete member. The basis of the test method and the requirements of the prestressing frame and its components are presented, as well as the test procedure stages and the measurement devices. The interpretation of the test results and the criteria to determine both the initial and the long-term transfer lengths are explained.A test method application and the equipment for testing seven-wire prestressing strands have been designed. Some experimental results are provided to validate the test. A comparative analysis of test reliability with other existing experimental methods is also included.

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“…A novel alternative device to measure the transfer length, called a Laser Speckle Imaging (LSI) sensor, was developed previously by the authors 6,7,8,9,10 . It is based on a previously developed 5-axis (five degree of freedom) surface displacement measurement technique 11 and its operation has been verified through extensive manual testing.…”

Section: Novel Strain Sensor Developmentmentioning

confidence: 99%

A portable modular optical sensor capable of measuring complex multi-axis strain fields

et al. 2012

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This paper presents a portable optical sensor capable of measuring complex multi-axis strain fields without the need for special surface preparation or stringent sensor-to-surface alignment. The sensor consists of three to four electronic speckle photography (ESP) modules. The design of each modular element is based on a previously developed 5-axis (five degree of freedom) surface displacement measurement technique, and is able to measure two dimensional in-plane surface movement, unaffected by other degrees of freedom (displacement and rotation) movement. Identical modular strain elements are arranged in a Rosette grid layout so that accurate and robust multi-axis surface strain measurement can be achieved.Experiments were conducted to demonstrate the multi-axis strain field measurement capability of this optical sensor by using a test bed that provided a known directional planar strain field, and excellent results were obtained. In particular, experiments have shown that the principle strain can be accurately extracted independent of the orientation of the device. This portable optical sensor will allow precise non-contact measurement of practical complex strain fields such as those encountered in bridge abutments, and portions of beams near critical infrastructure support locations; in other words, wherever plane strains depart from uni-axial behavior. Its unique hand-held portable capability offers distinct advantages over laboratory strain measurement setups, allowing accurate robust non-contact measurements to be achieved even in a harsh field application environment.

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Optical Sensor Developments for Measuring the Surface Strains in Prestressed Concrete Members

Cited by 12 publications

References 11 publications

Prestress losses evaluation in prestressed concrete prismatic specimens

Prestress losses evaluation in prestressed concrete prismatic specimens

Experimental Technique for Measuring the Long‐term Transfer Length in Prestressed Concrete

A portable modular optical sensor capable of measuring complex multi-axis strain fields

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