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.

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.

Effect of Pier Vertical Deformations on Deflections of Main Girders for High Pier and Long-Span Continuous Rigid-Frame Bridges

2010 ◽  
Vol 163-167 ◽  
pp. 1436-1439
Author(s):  
Jin Sheng Du ◽  
Hai Bin Liu
Keyword(s):  
Prestressed Concrete ◽  
Short Term ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Girder Bridges ◽  
Long Span ◽  
Concrete Box Girder ◽  
Concrete Box Girder Bridges ◽  
Main Girder

In some long-span prestressed concrete box girder bridges, excessive deflections of main girders are often observed. These unacceptable deflections have detrimental influence on the serviceability and safety of the structures. To better understand and estimate short term and long term deflections for prestressed concrete box girder bridges, pier vertical deformation and its effect on deflections of main girders of Jinghe Bridg is investigated in this paper. Piers in Jinghe Bridge are tall and the difference in height between piers up to 22 m. Analysis indicates that although the short term deformations of piers are small, the long term deformations of piers can be 3 times as large as that of short-term ones. The maximum short-term downward deflection of Jinghe Bridge caused by pier deformation for main girders is 7.7 mm and the maximum long-term downward deflection is 33.3 mm. These values are relatively small compared with the span length of the bridge. But when the deflection of the main girder itself is also included, the final total deflection of the main girder may exceed the design code limit.

Study on Crack Causes and Strengthening Measures of Large Span PC Continuous Box Girder Bridges

2010 ◽  
Vol 163-167 ◽  
pp. 3551-3554
Author(s):  
Wei Peng ◽  
Zhi Xiang Zha
Keyword(s):  
Prestressed Concrete ◽  
Load Test ◽  
Box Girder Bridges ◽  
Element Analysis ◽  
Box Girder ◽  
Girder Bridges ◽  
Long Span ◽  
Concrete Box Girder Bridges ◽  
Girder Bridge ◽  
Engineering Projects

This template Based on cracks observation and finite element analysis of real engineering projects as well as bridge load test after reinforcement, causes and types of cracks in prestressed concrete box girder bridges and treating measurements are systematically studied. The results obtained from the calculation are presented to demonstrate the effect of sensitive factors, such as arrangement of longitudinal prestressed tendons, the magnitude of vertical prestressed force, temperature gradient, etc. The results show that the arrangement of longitudinal prestressed tendons and the magnitude of vertical prestressed force take key roles in cracks control of box girder webs. Lots of treating measurements are presented in accordance with different types of cracks, some of them are applied to a reinforcement engineering of a long span pretressed concrete continuous box girder bridge with cracks. Load test after reinforcement of the bridge demonstrates the reasonability of the treating measurements. Several design recommendations and construction measures about reinforcements and some sensitive factors mentioned above are proposed to control cracks.

scholarly journals Life-Cycle Monitoring of Long-Span PSC Box Girder Bridges through Distributed Sensor Network: Strategies, Methods, and Applications

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Zheheng Chen ◽  
Tong Guo ◽  
Shengyou Yan
Keyword(s):  
Life Cycle ◽  
Prestressed Concrete ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Distributed Sensor ◽  
Railway Systems ◽  
Girder Bridges ◽  
Long Span ◽  
Design Values ◽  
Cycle Monitoring

Structural health monitoring (SHM) has attracted much attention in recent years, which enables early warnings of structural failure, condition assessments, and rational maintenance/repair strategies. In the context of bridges, many long-span steel bridges in China have been installed with the SHM systems; however, the applications of the SHM in prestressed concrete (PSC) bridges are still rather limited. On the other hand, the PSC box girder bridges are extensively used in highway and railway systems and premature damage of these bridges is often reported, resulting in considerable maintenance and/or replacement costs. First, this paper presents a state-of-art review on the SHM of long-span PSC bridges. Monitoring strategies, methods, and previous applications for these bridges are summarized and discussed. In order to well capture the behavior of the bridge during its whole life and to maximize the use of sensors, a life-cycle monitoring strategy is proposed, in which the sensor layout is determined according to requirements for construction monitoring, completion test, and in-service monitoring. A case study is made on a three-span PSC box girder bridge in China. The system configuration, sensor layout, and data communications, and so forth, are presented. The up-to-date monitored structural responses are analyzed and compared with the design values.

Behaviour Analysis of Prestressed Concrete Deck-Tied Arch Bridge

2013 ◽  
Vol 671-674 ◽  
pp. 952-956 ◽  
Author(s):  
Yi Qiang Xiang ◽  
Li Chang Zhang ◽  
Qiang Qiang Wu
Keyword(s):  
Prestressed Concrete ◽  
Internal Force ◽  
Analysis Model ◽  
Box Girder ◽  
Arch Bridge ◽  
Long Span ◽  
Prestressing Force ◽  
Horizontal Thrust ◽  
Tied Arch Bridge ◽  
Concrete Deck

The prestressed concrete deck-tied arch bridge doesn’t only have a long span, good appearance and economy, but also have the characteristics of low requirements to the foundation. It changes traditional tied arch bridge into deck-tied arch bridge, which looks like sunflower-shaped arch and prestressed steel strands are embedded in box girder on the top of the arch. Taking Yingbin Bridge as engineering background, the reasonable analysis model was established and behaviour of the bridge under design load was analyzed. The results shown that the design project is reasonable, prestressing force embedded in box girder can balance horizontal thrust in arch bridge effectively, improving the internal force of the main arch ring.

scholarly journals State-of-the-Art Review on Determining Prestress Losses in Prestressed Concrete Girders

2020 ◽  
Vol 10 (20) ◽  
pp. 7257
Author(s):  
Marco Bonopera ◽  
Kuo-Chun Chang ◽  
Zheng-Kuan Lee
Keyword(s):  
Prestressed Concrete ◽  
State Of The Art ◽  
Nondestructive Method ◽  
Prestress Loss ◽  
Prestress Losses ◽  
Long Span Bridges ◽  
Concrete Girders ◽  
Long Span ◽  
Vibration Responses ◽  
Prestressed Concrete Girders

Prestressing methods were used to realize long-span bridges in the last few decades. For their predictive maintenance, devices and dynamic nondestructive procedures for identifying prestress losses were mainly developed since serviceability and safety of Prestressed Concrete (PC) girders depend on the effective state of prestressing. In fact, substantial long term prestress losses can induce excessive deflections and cracking in large span PC bridge girders. However, old unsolved problematics as well as new challenges exist since a variation in prestress force does not significantly affect the vibration responses of such PC girders. As a result, this makes uncertain the use of natural frequencies as appropriate parameters for prestress loss determinations. Thus, amongst emerging techniques, static identification based on vertical deflections has preliminary proved to be a reliable method with the goal to become a dominant approach in the near future. In fact, measured vertical deflections take accurately and instantaneously into account the changes of structural geometry of PC girders due to prestressing losses on the equilibrium conditions, in turn caused by the combined effects of tendon relaxation, concrete creep and shrinkage, and parameters of real environment as, e.g., temperature and relative humidity. Given the current state of quantitative and principled methodologies, this paper represents a state-of-the-art review of some important research works on determining prestress losses conducted worldwide. The attention is principally focused on a static nondestructive method, and a comparison with dynamic ones is elaborated. Comments and recommendations are made at proper places, while concluding remarks including future studies and field developments are mentioned at the end of the paper.

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