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.

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.

Structural Design of High-Performance Concrete Bridge Beams

2000 ◽  
Vol 1696 (1) ◽  
pp. 171-178
Author(s):  
Xiaoming (Sharon) Huo ◽  
Maher K. Tadros
Keyword(s):  
Structural Design ◽  
High Performance ◽  
High Performance Concrete ◽  
Highway Bridges ◽  
Major Effect ◽  
Minor Effect ◽  
Bottom Flange ◽  
Prestress Losses ◽  
Bridge Beams ◽  
Creep And Shrinkage

Recently high-performance concrete (HPC) has been used in highway bridges and has gained popularity for its short-term and prospective long-term performances. Benefits of using HPC include fewer girder lines required, longer span capacity of girders, reduced creep and shrinkage deformation, less prestress losses, longer life cycle, and less maintenance of bridges. Research has been conducted on several issues of structural design of HPC bridge beams. The topics discussed include the effects of section properties of prestressed concrete girders, allowable tensile and compressive stresses, creep and shrinkage deformations of HPC, and prediction of prestress losses with HPC. The results from a parametric study have shown that a section that can have a large number of strands placed in its bottom flange is more suitable for HPC applications. The use of 15-mm-diameter prestressing strands allows the higher prestressing force applied on sections and can provide more efficiency in HPC bridges. The research results also indicate that the allowable compressive strength of HPC has a major effect on the structural design of bridges, whereas the allowable tensile stress has a minor effect on the design. Equations for predicting prestress losses based on the experimental and analytical results are recommended. The recommended equations consider the effects of lower creep and shrinkage deformations of HPC.

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.

scholarly journals Time-dependent reliability analyses of prestressed concrete girders strengthened with CFRP laminates

2019 ◽  
Vol 196 ◽  
pp. 109297 ◽  
Author(s):  
D. Dias-da-Costa ◽  
L.A.C. Neves ◽  
S. Gomes ◽  
S.A. Hadigheh ◽  
P. Fernandes
Keyword(s):  
Prestressed Concrete ◽  
Time Dependent ◽  
Cfrp Laminates ◽  
Concrete Girders ◽  
Prestressed Concrete Girders

scholarly journals Innovative design approach of precast–prestressed girder bridges using ultra high performance concrete

2010 ◽  
Vol 37 (4) ◽  
pp. 511-521 ◽  
Author(s):  
H. Almansour ◽  
Z. Lounis
Keyword(s):  
Prestressed Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Concrete Slab ◽  
High Strength ◽  
Design Approach ◽  
Highway Bridge ◽  
Efficient Design ◽  
Ultra High Performance Concrete ◽  
Prestressed Concrete Girders

The construction of new bridges and the maintenance and renewal of aging highway bridge network using ultra high performance concrete can lead to the construction of long life bridges that will require minimum maintenance resulting in low life cycle costs. Ultra high performance concrete (UHPC) is a newly developed concrete material that provides very high strength and very low permeability to aggressive agents such as chlorides from de-icing salts or seawater. Ultra high performance concrete could enable major improvements over conventional high performance concrete (HPC) bridges in terms of structural efficiency, durability, and cost-effectiveness over the long term. A simplified design approach of concrete slab on UHPC girders bridge using the Canadian Highway Bridge Design code and the current recommendations for UHPC design is proposed. An illustrative example demonstrates that the use of UHPC in precast–prestressed concrete girders yields a more efficient design of the superstructure where considerable reduction in the number of girders and girder size when compared to conventional HPC girders bridge with the same span length. Hence, UHPC results in a significant reduction in concrete volume and then weight of the superstructure, which in turn leads to significant reduction in the dead load on the substructure, especially for the case of aging bridges, thus improving their performance.

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