Analysis of Tensile Stresses in Transfer Zone of Prestressed Concrete U-Beams

2005 ◽  
Vol 1928 (1) ◽  
pp. 134-141 ◽  
Author(s):  
Dongzhou Huang ◽  
Mohsen Shahawy
Keyword(s):  
Prestressed Concrete ◽  
Practical Method ◽  
Tensile Stresses ◽  
Prestressed Girders ◽  
Plate Elements ◽  
Mechanical Models ◽  
Concentrated Forces ◽  
Shell Plate ◽  
Finite Shell ◽  
Transfer Zone

Prestressed U-beam bridges compare favorably in cost and appearance to traditional concrete I-beam bridges. Consequently, U-beam bridges are gaining in popularity and usage, especially when aesthetic issues are deemed important. U-beam bridges first appeared in Florida in 2000; however, during construction, cracks developed in the webs of the U-beams. This paper presents results of an analysis of representative cracking of U-beams and proposes a practical method for the transfer zone stirrup design. For the purpose of the analysis, the U-beam is divided into a series of finite shell-plate elements, and the prestressing tendons are simulated as a number of concentrated forces. Two different mechanical models of the U-beams are developed on the basis of the stages of construction. Analytical results show that high tensile stresses occur in the end zone of the U-beam because of the prestressing tendons and that these tensile stress must be properly considered in bridge design. The research results are applicable to the design of prestressed U-beams and similar types of prestressed girders.

Capacity of prestressed concrete bridge decks under fatigue loading

2021 ◽  
Author(s):  
Eva O. L. Lantsoght ◽  
Cor van der Veen ◽  
Rutger Koekkoek ◽  
Henk Sliedrecht
Keyword(s):  
Prestressed Concrete ◽  
Large Scale ◽  
Fatigue Loading ◽  
Membrane Action ◽  
Variable Amplitude ◽  
Girder Bridges ◽  
Prestressed Girders ◽  
Series Of Experiments ◽  
Prestressed Concrete Bridge ◽  
Compressive Membrane Action

<p>In The Netherlands, existing slab-between-girder bridges with prestressed girders and thin transversely prestressed concrete decks require assessment. The punching capacity was studied in a previous series of experiments, showing a higher capacity thanks to compressive membrane action in the deck. Then, concerns were raised with regard to fatigue loading. To address this, two series of large-scale experiments were carried out, varying the number of loads (single wheel print versus double wheel print), the loading sequence (constant amplitude versus variable amplitude, and different loading sequences for variable amplitude), and the distance between the prestressing ducts. An S-N curve is developed for the assessment of slab-between-girder bridges. The experiments showed that compressive membrane actions enhances the capacity of thin transversely prestressed decks subjected to fatigue loading.</p>

Design method for checking tensile stresses under service loads in cracked prestressed concrete members with 2,400‐MPa strands

2019 ◽  
Vol 29 (1) ◽  
Author(s):  
Hyo‐Eun Joo ◽  
Sun‐Jin Han ◽  
Deuckhang Lee ◽  
Hyunjin Ju ◽  
Soo‐Yeon Seo ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Design Method ◽  
Tensile Stresses ◽  
Concrete Members

The Effect of Higher Prestress on Concrete Railroad Tie Behavior

2015 ◽  
Author(s):  
N. D. Catella ◽  
R. A. Mayville
Keyword(s):  
Stress State ◽  
Prestressed Concrete ◽  
Three Dimensional ◽  
Negative Consequences ◽  
Premature Failure ◽  
Model Interaction ◽  
Tensile Stresses ◽  
Prestressing Force ◽  
Consistent Performance ◽  
Three Dimensional Finite Element

Prestressed concrete crossties are used extensively by North American railroads because they offer improved service life and consistent performance. Recent industry trends have encouraged manufacturers to effectively increase concrete ties’ prestressing force to improve their structural performance in flexure and shear. This paper presents the results of linear and nonlinear three-dimensional finite element analyses of typical concrete crossties to study the stress state of crossties at prestress transfer and to identify potential negative consequences of increasing effective prestressing force. The analyses utilize finite-sliding contact with Coulomb friction to model interaction between prestressing strands and adjacent concrete. Variation of several parameters that affect stress state at prestress transfer are considered, including magnitude of prestressing force, stiffness of concrete, crosstie geometry, and strand configuration. The analyses indicate that tensile stresses develop near the ends of the crossties at prestress transfer and their magnitudes increase with decreasing transfer length and increasing prestress force. These tensile stresses may account for widespread longitudinal cracking that has been observed in premature failure of concrete crossties in the last ten years.

ON THE REDUCTION OF PRESTRESSING FORCE NEAR SUPPORTS IN PARTIALLY PRESTRESSED CONCRETE FLEXURAL MEMBERS

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Nazar Oukaili
Keyword(s):  
Prestressed Concrete ◽  
Load Capacity ◽  
Compression Zone ◽  
Flexural Members ◽  
Tensile Stresses ◽  
Prestressing Force ◽  
Service Load ◽  
Bending Stresses ◽  
The Moment ◽  
Concrete Section

Straight tendons in pretensioned members can cause high-tensile stresses in the concrete extreme fibers at end sections because of the absence of the bending stresses due to self-weight and superimposed loads and the dominance of the moment due to prestressing force alone. Accordingly, the concrete tensile stresses at the ends of a member prestressed with straight tendons may limit the service load capacity of the member. It is therefore important to establish limiting zone in the concrete section within which the prestressing force can be applied without causing tension in the extreme concrete fibers. Two practical methods are available to reduce the stresses at the end sections due to the prestressing force. The first method based on changing the eccentricity of some tendons by raising them towards the end zone. The second method is based on bond prevention by encasing some of the tendons in plastic sheathing, effectively moving the point of application of prestressing force inward toward midspan for part of tendons. The present study focuses on a proposed third method to reduce the effect of the prestressing force near end supports by using straight strands with limited initial prestressing value in compression zone. New equations were suggested for the cracking moment and the prestressing force which consider the prestressed tendons in compression zone.

Critical review of the CSA A14-07 design provisions for torsion in prestressed concrete poles

2014 ◽  
Vol 41 (4) ◽  
pp. 304-314
Author(s):  
Michael Kuebler ◽  
Maria Anna Polak
Keyword(s):  
Prestressed Concrete ◽  
Transverse Reinforcement ◽  
Torsional Response ◽  
Strut And Tie ◽  
Prestressing Force ◽  
Force Transfer ◽  
Theoretical Predictions ◽  
Strut And Tie Model ◽  
Torque Values ◽  
Transfer Zone

This paper focuses on the effect of the transverse reinforcement in concrete poles and its influence on torsional strength in an effort to simplify the governing Canadian prestressed concrete pole code (CSA A14-07). The rationale behind the CSA code values for amount, spacing, and direction of the transverse reinforcement is not apparent. A testing program consisting of 14 concrete pole specimens were produced to investigate the torsional response. The specimens were divided into two groups with different tip diameters. Within each group the spacing and direction of the wound helical transverse reinforcement varied. Experimental cracking torque values were compared with calculated theoretical cracking torques from ACI 318, Eurocode 2, and various journal articles. The theoretical predictions were generally unconservative. Post-cracking behaviour was modelled using the Compression Field Theory (CFT) and Softened Truss Model (STM) for torsion. It was found that the CFT predicts the post-cracking response with reasonable accuracy. The failure mode in pure torsion is brittle and sudden, and the transverse reinforcement provides no post-cracking ductility. The primary function of the transverse reinforcement is to minimize the longitudinal precracking due to prestressing transfer forces. CSA A14 transverse reinforcement spacing requirements were compared against code minimum spacing requirements and a strut and tie model of the prestressing force transfer zone. Based on the strut and tie model of the transfer zone it was concluded that the CSA A14 helical reinforcement spacing values were insufficient to resist the transfer forces. New helical reinforcement spacing values were recommended to simplify the current CSA A14 code requirements. In addition concrete mix designs, prestressing levels, and wall thicknesses all have a large impact on torsional capacity and therefore quality assurance of these factors should be emphasized in CSA A14.

Nonlinear analysis of concrete structures

1982 ◽  
Vol 9 (3) ◽  
pp. 489-501 ◽  
Author(s):  
Ghoneim A. M. Ghoneim ◽  
Amin Ghali
Keyword(s):  
Finite Element ◽  
Computer Program ◽  
Prestressed Concrete ◽  
Concrete Structures ◽  
Number Of Layers ◽  
Proposed Model ◽  
Plate Elements ◽  
Nonlinear Stress ◽  
Strain Relationship ◽  
Relationship Of

A computer program is developed to determine the response of reinforced and prestressed concrete structures subjected to monotonic or cycling loading. The nonlinear stress–strain relationship of concrete and steel is accounted for by applying the load in increments and performing a series of iterations. The structure is treated as an assemblage of thin plate elements subjected to in-plane forces and bending. In the calculation of the structure stiffness, each element is assumed to be composed of a number of layers and the stiffness is allowed to vary over the area of the element and from one layer to the other according to the associated stress.The program employs an efficient finite element that makes it possible to use a relatively small number of elements. The reinforcements are idealized either by smearing a mesh or bars into a steel layer or, with heavy concentrated reinforcement or a prestress tendon, each reinforcing element is accounted for separately.The efficiency of the proposed model is tested by applying the computer program to three structures employing a very small number of elements in their idealization. The finite element idealizations are shown and the results of the analyses are compared with published experimental work.

Benefits of Using HSC for Improving Tensile Stresses on I-Type Prestressed Concrete Girders

2009 ◽  
Vol 96 (6) ◽  
pp. 10-15
Author(s):  
Young-Soo Yoon ◽  
Kyung-Hwan Min ◽  
Jae-Yong Lee ◽  
Jun-Mo Yang ◽  
Jae-Seong Lee ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Tensile Stresses ◽  
Concrete Girders ◽  
Prestressed Concrete Girders

Rehabilitation measures for Champlain Bridge, Montreal, Canada

1996 ◽  
Vol 23 (6) ◽  
pp. 1326-1340 ◽  
Author(s):  
G. P. Carlin ◽  
M. S. Mirza ◽  
M. Gaudreault
Keyword(s):  
Cathodic Protection ◽  
Prestressed Concrete ◽  
Concrete Beams ◽  
Pilot Project ◽  
Concrete Surface ◽  
Zinc Anode ◽  
Bridge Rehabilitation ◽  
Prestressed Girders ◽  
Protection Systems ◽  
Control Corrosion

Major rehabilitation of the Champlain Bridge, Montreal, Quebec, has been undertaken with the goal of restoring its overall integrity. The bridge is a major transportation link carrying over 42 million vehicle transits annually. Repairs to all elements of the structure have recently been under way, such as deck replacement, pier repairs including submerged regions, restoration to prestressed girders, implementation of cathodic protection to control corrosion, new drainage provisions, and crash barriers. Rehabilitation of the main steel truss spans over the St. Lawrence Seaway is presented elsewhere. Testing of two cathodic protection systems on prestressed concrete beams has been undertaken with the goal of full-scale installation on all 50 affected spans. A possible pilot project is being examined, which incorporates the use of zinc anode spray applied to the concrete surface to act as passive, or induced current type, or as a combination of active and passive systems on the different sections of the bridge. Key words: bridge rehabilitation, cathodic protection systems, condition survey, corrosion protection strategy, external prestressing, honeycombing and spalling, impervious membrane, injection of cracks, prestressed concrete beams, underwater pier repairs.

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