scholarly journals Long-Term Characteristics of Prestressing Force in Post-Tensioned Structures Measured Using Smart Strands

2020 ◽  
Vol 10 (12) ◽  
pp. 4084 ◽  
Author(s):  
Sang-Hyun Kim ◽  
Sung Yong Park ◽  
Se-Jin Jeon
Keyword(s):  
Prestressed Concrete ◽  
Mechanical Strain ◽  
Prestress Losses ◽  
Prestressing Force ◽  
Eurocode 2 ◽  
Study Results ◽  
Girder Bridge ◽  
Creep And Shrinkage ◽  
Term Monitoring

The proper distribution of prestressing force (PF) is the basis for the design of prestressed concrete (PSC) structures. However, the PF distribution obtained by predictive equations of prestress losses has not been sufficiently validated by comparison with measured data due to the poor reliability and durability of conventional sensing technologies. Therefore, the Smart Strand with embedded fiber optic sensors was developed and applied to PSC structures to investigate the long-term characteristics of PF distribution as affected by concrete creep and shrinkage. The data measured in a 20 m-long full-scale specimen and a 60 m-long PSC girder bridge were analyzed by comparing them with the theoretical estimation obtained from several design equations. Although the long-term decreasing trend of the PF distribution was similar in the measurement and theory, the equation of Eurocode 2 for estimating the long-term prestress losses showed better agreement with the measurement than ACI 209R and ACI 423.10R did. This can be attributed to the more refined form of the predictive equation of Eurocode 2 in dealing with the time-dependency of the PF. The study results also confirmed the need to compensate for the temperature variation in the long-term monitoring to derive the actual mechanical strain related to the PF. We expect our developed Smart Strand to be applied practically in PF measurement for the reasonable safety assessment and maintenance of PSC structures by improving several of the existing drawbacks of conventional sensors.

scholarly journals Analysis of Short-Term Prestress Losses in Post-tensioned Structures Using Smart Strands

2022 ◽  
Vol 16 (1) ◽  
Author(s):  
Sang-Hyun Kim ◽  
Sung Yong Park ◽  
Sung Tae Kim ◽  
Se-Jin Jeon
Keyword(s):  
Prestressed Concrete ◽  
General Assumption ◽  
Design Parameters ◽  
Short Term ◽  
Prestress Losses ◽  
Predictive Equations ◽  
Girder Bridges ◽  
Long Span ◽  
Prestressing Force ◽  
Study Results

AbstractThe proper estimation of prestressing force (PF) distribution is critical to ensure the safety and serviceability of prestressed concrete (PSC) structures. Although the PF distribution can be theoretically calculated based on certain predictive equations, the resulting accuracy of the theoretical PF needs to be further validated by comparison with reliable test data. Therefore, a Smart Strand with fiber optic sensors embedded in a core wire was developed and applied to a full-scale specimen and two long-span PSC girder bridges in this study. The variation in PF distribution during tensioning and anchoring was measured using the Smart Strand and was analyzed by comparison with the theoretical distribution calculated using the predictive equations for short-term prestress losses. In particular, the provisions for anchorage seating loss and elastic shortening loss were reviewed and possible improvements were proposed. A new method to estimate the amount of anchorage slip based on real PF distributions revealed that the general assumption of 3–6-mm slip falls within a reasonable range. Finally, the sensitivity of the PF distribution to a few of the variables included in the equation of the elastic shortening loss was examined. The study results confirmed that the developed Smart Strand can be used to improve the design parameters or equations in PSC structures by overcoming the drawbacks of conventional sensing technologies.

Time-Dependent Prestress Losses in Prestressed Concrete Girders Built of High-Performance Concrete

1997 ◽  
Vol 1594 (1) ◽  
pp. 64-72 ◽  
Author(s):  
M. Myint Lwin ◽  
Bijan Khaleghi
Keyword(s):  
Prestressed Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Time Dependent ◽  
Step Method ◽  
Time Step ◽  
Prestress Losses ◽  
Concrete Girders ◽  
Prestressed Concrete Girders ◽  
Creep And Shrinkage

The Washington State Department of Transportation is one of several state departments of transportation involved in demonstration projects to acquire information and data on the design, fabrication, and construction of prestressed concrete bridges with high-performance concrete (HPC). Predicting the time-dependent prestress losses due to the creep and shrinkage of HPC and the relaxation of prestressing steel is difficult because of the limited experience with and data on the creep and shrinkage properties of HPC. The AASHTO load resistance factor design specification approach to estimating prestress losses is discussed, and the time-step method and the modified rate-of-creep method are introduced as ways of predicting more accurately the time-dependent prestress losses. A design example is used to compare and discuss numerically the prestress losses computed by the various methods. The modified rate-of-creep analysis method yields the lowest losses. The modified rate-of-creep method is a desirable, comprehensive, applicable, and practical method for estimating time-dependent prestress losses in composite and noncomposite prestressed concrete girders with HPC. This method is suitable for manual and electronic computation.

scholarly journals Testing and long-term monitoring of a curved concrete box girder bridge

2011 ◽  
Vol 33 (10) ◽  
pp. 2861-2869 ◽  
Author(s):  
Hugo C. Gomez ◽  
Paul J. Fanning ◽  
Maria Q. Feng ◽  
Sungchil Lee
Keyword(s):  
Box Girder ◽  
Long Term Monitoring ◽  
Concrete Box Girder ◽  
Box Girder Bridge ◽  
Girder Bridge ◽  
Term Monitoring

scholarly journals Long-term Deflections in Balanced Cantilever Prestressed Concrete Bridges

2009 ◽  
Vol 4 (1) ◽  
pp. 22
Author(s):  
Eltayeb Hassan Onsa ◽  
Elsafi Mohamed Adam ◽  
Abdalla Khogali Ahmed ◽  
Mohamed Elmontasir Elbagir
Keyword(s):  
Prestressed Concrete ◽  
Concrete Bridges ◽  
Live Load ◽  
Prestressed Concrete Bridges ◽  
Prestressing Force ◽  
Load Tests ◽  
The Moment ◽  
Aashto Lrfd ◽  
Made In

Long-term deflections in balanced cantilever prestressed concrete bridges are reviewed. Burri and Shambat Bridges are taken as cases study to calculate long-term deflection. The two bridges were constructed at Khartoum State in the years 1972 and 1962, respectively. Due to the shortage of the basic data regarding the two bridges the AASHTO-LRFD is used to estimate and calculate the missing data in the two bridges. The Moment Area method is used to calculate the long-term deflections due to the dead load, live load and prestressing force. The calculated long-term deflections are compared with measured live load deflections obtained from load tests made by a Chinese contractor requested to evaluate the two bridges. Remarkable differences between theoretical and measured deflection at the end of cantilevers are encountered. The differences are probably due to the basic assumptions made in the formulations of deflection calculations. Some adjustments in the long-term deflection formulae are suggested to bring the calculated deflections in compatibility with measured ones.

scholarly journals DEFORMATIONAL ANALYSIS OF PRESTRESSED HIGH‐STRENGTH CONCRETE MEMBERS USING FLEXURAL CONSTITUTIVE MODEL

2005 ◽  
Vol 11 (2) ◽  
pp. 145-151
Author(s):  
Renata Zamblauskaitė ◽  
Gintaris Kaklauskas ◽  
Darius Bačinskas
Keyword(s):  
Constitutive Model ◽  
Prestressed Concrete ◽  
Linear Time ◽  
High Strength ◽  
Concrete Members ◽  
Calculation Technique ◽  
Short And Long Term ◽  
Modulus Method ◽  
Creep And Shrinkage

In this paper, an attempt has been made to extend application of the recently proposed Flexural constitutive model to short‐ and long‐term deformational analysis of flexural partially prestressed concrete members. The effect of tension stiffening and non‐linear time effects of creep and shrinkage are taken into account. Effective modulus method is used for modelling long‐term deformations. The proposed calculation technique is based on the layered approach and use of material stress‐strain relationships. Curvatures prediction results were tested against experimental data of partially prestressed concrete beams reported in literature.

scholarly journals Effect of Time Dependent Variables on Different Types of PSC Box Girder Bridges.

2019 ◽  
Vol 11 (02) ◽  
pp. 123-128
Author(s):  
Norine George ◽  
Kiran Umachagi ◽  
Sunil Kumar Tengli
Keyword(s):  
Cross Section ◽  
Prestressed Concrete ◽  
Cell Types ◽  
Time Dependent ◽  
Box Girder ◽  
Temperature Creep ◽  
Dependent Variables ◽  
Concrete Box Girder ◽  
Girder Bridge ◽  
Creep And Shrinkage

Time dependent variables such as temperature gradient, effective temperature, creep, and shrinkage lead to long term deflection in prestressed concrete girders. This in turn effects the serviceability and sustainability of the bridge in the long run. Therefore, research and analysis is of paramount importance before deciding the type of girder to be used. A parametric study was carried out in order to determine the most desirable and efficient type of box girder to be used for a prestressed concrete bridge having a continuous span. Three prestressed concrete box girder bridge models of single, multi-cell rectangular and multi-cell trapezoidal cross section, having similar span, width and depth were taken into consideration. The finite element models were analysed using MIDAS Civil. The behaviour of the box girder cell types under various time dependent properties such as temperature, creep and shrinkage are presented in this paper. The results show that the prestressed concrete box girder bridge of multi-cell rectangular cross section exhibits greater forces and moments due to time dependent variables in comparison to the other two box girder cell types.

scholarly journals LONG‐TERM DEFORMATION ANALYSIS OF NON‐CRACKED PC MEMBERS USING FLEXURAL CONSTITUTIVE MODEL AND DESIGN METHODS

2006 ◽  
Vol 12 (2) ◽  
pp. 124-133
Author(s):  
Renata Zamblauskaite ◽  
Gintaris Kaklauskas ◽  
Povilas Vainiūnas
Keyword(s):  
Constitutive Model ◽  
Prestressed Concrete ◽  
Linear Time ◽  
Deformation Analysis ◽  
Stress And Strain ◽  
Concrete Members ◽  
Calculation Technique ◽  
Modulus Method ◽  
Creep And Shrinkage

In this paper, an attempt has been made to extend application of the recently proposed Flexural constitutive model to long‐term deformation analysis of prestressed concrete members. The effect of non‐linear time effects of creep and shrinkage are taken into account. Effective modulus method is used for modeling of long‐term deformations. The proposed calculation technique is based on the layered approach and use of material stress and strain relationships. Curvatures and deflections prediction results were tested against experimental data of prestressed concrete beams reported in the literature.

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