Research on Stress Increase of Unbonded Tendons at Ultimate in Prestressed Concrete Continuous Beams

2012 ◽  
Vol 166-169 ◽  
pp. 1554-1557
Author(s):  
Xiao Dong Wang ◽  
Wen Zhong Zheng ◽  
Ying Wang
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beams ◽  
Simulation Analysis ◽  
Analysis Method ◽  
Stress Increase ◽  
Continuous Beams ◽  
Unbonded Tendons ◽  
Index Ratio ◽  
Prestressed Reinforcement ◽  
Rational Evaluation

Rational evaluation for stress increase of unbonded tendon at ultimate is the basis to exactly compute flexural load bearing capacity of unbonded prestressed concrete beams. Moment-curvature nonlinear analysis method is adopted to compile programs for calculating stress increase at ultimate in unbonded prestressed continuous beams. The precision of the method is proved by comparing results of 16 experimental two-span unbonded prestressed continuous beams to the prediction value of stress increase at ultimate. Based on the simulation analysis, law of the influence of some basic factors to stress increase at ultimate in unbonded tendons in continuous beams is obtained, such as non-prestressed reinforcement index, prestressed reinforcement index, ratio of span to depth and loading type. Then formulas for calculating stress increase at ultimate in unbonded tendons in prestressed concrete continuous beams were established.

Calculation Methods of CFRP Tendons Stress in Two-Span Prestressed Continuous Beams

2013 ◽  
Vol 859 ◽  
pp. 60-63
Author(s):  
Chong Xi Bai ◽  
Xin Yan Shao ◽  
Qiu Ping Wang
Keyword(s):  
Simulation Analysis ◽  
Full Range ◽  
Fiber Reinforced Polymer ◽  
Analysis Method ◽  
Stress Increment ◽  
Range Analysis ◽  
Reinforced Polymer ◽  
Continuous Beams ◽  
Unbonded Tendons ◽  
Deformation Compatibility

Crack width, deflection and load bearing capacity of two-span concrete continuous beams partially prestressed with unbonded carbon fiber reinforced polymer (CFRP) tendons can be calculated accurately, the first premise is to calculate reasonably the stress increment of CFRP tendons. However, the law of stress increment of unbonded tendons is unclear. Moment-curvature analysis method and deformation compatibility condition were used to compile nonlinear full-range analysis programs of this kind of continuous beam. The comparison between simulated results and tested results of stress in CFRP tendons indicates that the simulation analysis programs are reliable.

Ductility analysis of prestressed concrete beams with unbonded tendons

2008 ◽  
Vol 30 (1) ◽  
pp. 13-21 ◽  
Author(s):  
J.S. Du ◽  
Francis T.K. Au ◽  
Y.K. Cheung ◽  
Albert K.H. Kwan
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beams ◽  
Unbonded Tendons

Flexural ductility of prestressed concrete beams with unbonded tendons

2009 ◽  
Vol 6 (6) ◽  
pp. 451-472 ◽  
Author(s):  
F.T.K. Au ◽  
K.H.E. Chan ◽  
A.K.H. Kwan ◽  
J.S. Du
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beams ◽  
Unbonded Tendons ◽  
Flexural Ductility

Experimental Study on Behaviors of Unbonded Prestressed Concrete Beams Reinforced with CFRP Tendons

2008 ◽  
Vol 400-402 ◽  
pp. 567-573 ◽  
Author(s):  
Wen Zhong Zheng ◽  
Chong Xi Bai ◽  
Hui Dong Cheng
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beams ◽  
Limit State ◽  
Plastic Hinge ◽  
Stress Increment ◽  
Intermediate Support ◽  
Strength Limit ◽  
Continuous Beams ◽  
Bending Capacity ◽  
The Law

In order to research behaviors of unbonded prestressed concrete beams reinforced with CFRP tendons, static load experiments on 4 partially prestressed simple beams with unbonded CFRP tendons and 9 two spans partially prestressed concrete continuous beams with unbonded CFRP tendons were performed. Based on the experiment results of simple beams, the law of ultimate stress increment in unbonded CFRP tendons in simple beams was obtained. Based on the experiment results of continuous beams, the law of stress increment in unbonded CFRP tendons in continuous beams was obtained at serviceability state and at strength limit state of bending capacity. The calculation formula of length of equivalent plastic hinge for this kind of continuous beam was presented. The calculation formulas of moment modification coefficient with composite reinforcement index for intermediate support as variable and relative plastic rotation for intermediate support as variable were given respectively.

Experimental Study on Mechanical Performance of Unbonded and Bonded Prestressed Concrete Beams

2012 ◽  
Vol 178-181 ◽  
pp. 2387-2392
Author(s):  
Jian Su ◽  
Nan Gai Yi ◽  
Zong Guang Sun ◽  
Yang Bai ◽  
Ai Guo Zhang
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beam ◽  
Mechanical Performance ◽  
Concrete Beams ◽  
Stress And Strain ◽  
Strain Variation ◽  
Yield Strain ◽  
Prestressed Concrete Beam ◽  
Bearing Load ◽  
Prestressed Reinforcement

The experiment which based on the stress performance of unbonded and bonded prestressed concrete beam, has made a systematically research on the stress and strain variation law of pretressing tendon in the aforementioned reinforcement prestressed concrete structure. When the bonded prestressed concrete beam bearing load, there is a larger variation in stress and strain of prestressing reinforcement along the length. The maxima of stress and strain of prestressing reinforcement in bonded prestressed concrete beam appears in midspan, it is achieved the yield stress and yield strain, the minima appears in bearing, the stress and strain of prestressing reinforcement in bonded prestressed concrete beam is proportional to the distortion. The stress and strain of prestressed reinforcement in unbonded prestressed concrete beam is almost the same along the length.

Beams prestressed with unbonded tendons at ultimate

1996 ◽  
Vol 23 (6) ◽  
pp. 1220-1230 ◽  
Author(s):  
Marco Andrea Pisani ◽  
Emilio Nicoli
Keyword(s):  
Numerical Analysis ◽  
Key Words ◽  
Prestressed Concrete ◽  
Concrete Beams ◽  
Experimental Tests ◽  
Safety Factors ◽  
Unbonded Tendons ◽  
External Tendons ◽  
Simplified Method ◽  
Good Agreement

This paper presents a numerical investigation on beams and slabs prestressed with either unbonded internal or external tendons. Twenty-three experimental tests (beams and slabs prestressed with unbonded internal tendons) were numerically simulated to verify the reliability of the numerical algorithm adopted. The good agreement established enables us to study the behaviour of these beams in depth and to compare it with the behaviour of similar beams prestressed with external tendons. The numerical analyses were then repeated after including the safety factors related to the materials. The outputs were then compared with the results adopted by making use of the simplified method suggested by Eurocode E.C.2 Part 1-5, to check the size of the error involved in the adoption of the latter. Key words: numerical analysis, unbonded internal tendons, external tendons, European Prestandard, prestressed concrete, beams, post-tensioned.

Theoretical Analysis of Natural Vibration Frequency for Unbonded Prestressed Concrete Beams

2012 ◽  
Vol 594-597 ◽  
pp. 882-885 ◽  
Author(s):  
Feng Ge Li ◽  
Rong Li
Keyword(s):  
Prestressed Concrete ◽  
Natural Frequencies ◽  
Concrete Beams ◽  
Flexural Rigidity ◽  
Variable Stiffness ◽  
Natural Vibration Frequency ◽  
Test Results ◽  
Unbonded Tendons ◽  
Proposed Model ◽  
Calculation Results

This papers deals with the study of the influence of prestress force on the natural frequencies for unbonded prestressed concrete beams. A total of 5 unbounded prestressed concrete simply support beams were constructed and tested. The test results show that the prestress force has little effect on the nature frequencies of unbonded prestressed concrete beams. A model of variable stiffness is proposed to calculate the natural frequencies of prestressed concrete beams with unbonded tendons, which assumed that the flexural rigidity of the beam is changing when beams vibrating. The calculate results show that the calculation results by the proposed model agree well with experimental ones.

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