scholarly journals Comparative Study of Prestress Losses

2017 ◽  
Vol 7 (3) ◽  
pp. 1633-1637
Author(s):  
M. Boukendakdji ◽  
M. Touahmia ◽  
M. Achour
Keyword(s):  
Comparative Study ◽  
Prestressed Concrete ◽  
Concrete Beam ◽  
American Concrete Institute ◽  
Design Codes ◽  
Prestress Losses ◽  
British Standard ◽  
Simply Supported ◽  
Shrinkage And Creep ◽  
Post Tensioning

This paper compares the prestress losses as calculated by four different design codes; British standard CP110, Comite Europeen du Beton 70 and 78, American Concrete Institute 77 and the Prestressed Concrete Institute method (PCI). The comparison is done by determining the total losses which take place in a rectangular prestressed concrete beam for both pre-tensioning and post-tensioning systems. The results show that total losses calculated for the post-tensioning method are higher than those calculated for the pre-tensioning method, which is not the usual case. It seems that the PCI method may be required for special structures or for simply supported slender members which may be sensitive to small changes in deflections. However, for non-special structures, or where actual losses have little effect on the design, it is better to compute losses by the ACI method because it is simple and does take into considerations interactions between the various sources of losses. However, it is not possible to conclude which method gives the more accurate prediction of shrinkage and creep without direct co-relation to realistic insitu data.

Study on Prediction Model of Shrinkage and Creep of Prestressed Concrete Beam in Passenger Dedicated Line

2011 ◽  
Vol 255-260 ◽  
pp. 3998-4002
Author(s):  
Jun Li Luo ◽  
Zhi Sheng Xu ◽  
Jun Li ◽  
Ji Hao Yang
Keyword(s):  
Prestressed Concrete ◽  
High Speed ◽  
Concrete Beam ◽  
Influence Factors ◽  
Creep Model ◽  
High Speed Railway ◽  
Modified Model ◽  
Shrinkage And Creep ◽  
Prestressed Concrete Bridge ◽  
Passenger Dedicated Line

To improve the calculation precision of deformation in prestressed concrete bridge in passenger dedicated line and accurately predict the development of shrinkage and creep in bridge, a universal applicable modified model was put forward in this paper based on ACI 209R(1992) shrinkage and creep model. In the modified model, three influence factors-slump, strength and reinforcement - are corrected. And the modified model results were compared with the experimental results. It shows that the modified model can more accurately predict the development of shrinkage and creep of high-speed railway bridge and better accord with the law of it.

scholarly journals Prestress Losses in Concrete Rafters with Openings

2020 ◽  
Vol 10 (2) ◽  
pp. 5512-5519
Author(s):  
F. J. Alkhafaji ◽  
A. F. Izzet
Keyword(s):  
Cross Section ◽  
Prestressed Concrete ◽  
Beam Length ◽  
Prestress Loss ◽  
Prestress Losses ◽  
Simply Supported ◽  
Prestressing Force ◽  
Size Number ◽  
The Cross ◽  
Code Provisions

In this paper, experimental work was conducted to evaluate the losses in prestressing force of 13 (12 perforated and 1 solid) simply supported prestressed concrete rafters. All beams had the same dimensions and reinforcements. The tested beams were divided into four main groups and three additional subgroups were driven. These groups were classified according to size, number, and configuration of the openings, and the orientation of the posts (vertical or inclined). Regarding the prestress losses that have been affected by the cross-section properties, the provision of the codes is applicable only to prismatic solid beams, so non-prismatic or moreover perforated beams also need to be studied. This paper aims to propose a method based on the same code provisions but taking into consideration the cross-section variation along the beam length. The proposed method divides the overall length of the rafter into a number of assumed prismatic segments with heights measured at centers. Then, the overall prestress loss is found as the sum of these segments weighed by the ratios of the length of each beam segment to the overall length. The experimental results of the proposed method ranged from 84.749% to 95.607% denoting its validity.

A new steel anchorage system for post-tensioning applications using carbon fibre reinforced plastic tendons

1998 ◽  
Vol 25 (1) ◽  
pp. 113-127 ◽  
Author(s):  
Ezzeldin Y Sayed-Ahmed ◽  
Nigel G Shrive
Keyword(s):  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Fatigue Tests ◽  
Direct Tension ◽  
Element Analysis ◽  
Prestressing Steel ◽  
Reinforced Plastics ◽  
Anchorage System ◽  
Post Tensioning ◽  
Post Tension

During the past half century, the use of prestressing in different structures has increased tremendously. One of the most important techniques of prestressing is post-tensioning. The main problem associated with post-tensioning in different structures is the corrosion of the prestressing steel tendons even with well-protected steel. New materials, fibre reinforced plastics or polymers (FRP), which are more durable than steel, can be used for these tendons/strands and thus overcome the corrosion problem. However, different shortcomings appear when FRP tendons are introduced to post-tensioning prestressing applications. For carbon fibre plastic tendons (CFRP), there is no suitable anchorage system for post-tensioning applications. Some of the anchorages developed by others for use with FRPs are therefore described and assessed. A new anchorage system developed by the authors, which can be used with bonded or unbonded CFRP tendons in post-tensioning applications, is described. The results of direct tension and fatigue tests on CFRPs anchored with the new system are presented.Key words: anchorage system, cyclic loading, fatigue, fibre reinforced plastics, finite element analysis, post-tension, prestressed concrete, prestressed masonry, strands, tendons.

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