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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP245-09

Date: 

April 1, 2007

Author(s):

B. Taljsten and H. Nordin

Publication:

Symposium Papers

Volume:

245

Abstract:

Strengthening of concrete structures with fibre reinforced polymer materials has today grown to be a widely used method over most parts of the world. As a way of higher utilization of the FRP (Fibre Reinforced Polymers) prestressing has proved to be beneficial. Most of the research done with prestressing Carbon Fibre Reinforced Polymers (CFRP) for strengthening has been with surface bonded plates. However, in this paper a presentation is given where CFRP quadratic rods are bonded in the concrete cover in sawed grooves and then immediately prestressed. Testing has, proven this to be an advantageous way of bonding CFRP to the concrete. There is also a tendency that the shear forces between the CFRP and the concrete are transferred more efficiently compared to surface bonded plates and sheets. In the tests performed, no mechanical device has been used to keep the prestress during testing, which then means that the adhesive has to transfer all shear stresses to the concrete. These tests have then been compared with concrete beams strengthened with prestressed external steel and CFRP tendons and similar load carrying capacity has been obtained.

DOI:

10.14359/18767


Document: 

SP245-07

Date: 

April 1, 2007

Author(s):

Y.J. Kim, C. Shi, L. Bizindavyi, and M.F. Green

Publication:

Symposium Papers

Volume:

245

Abstract:

The issue of the rehabilitation of damaged structures has attracted the attention of researchers to resolve undesired problems caused by increased traffic loads, corrosion, or impact damage. Appropriate methods are therefore essential for extending the lifespan of the structures. The application of carbon fiber reinforced polymer (CFRP) sheets has been reported as a promising and viable solution with many advantages such as increased flexural strength, and improved serviceability and durability. CFRP sheets may be used more efficiently by applying prestress. For this effective strengthening application, the method of prestressing CFRP sheets and its feasibility are important parameters that need further investigation. In this study, the applicability of a prestressing system is investigated on large-scale prestressed concrete beams (3.3 m span) tested under static loading. Nonlinear finite element analysis is conducted to predict the behavior of tested beams, including a parametric study to investigate the contribution of different prestress levels in the CFRP sheets to the flexural behavior of strengthened beams.

DOI:

10.14359/18765


Document: 

SP245-08

Date: 

April 1, 2007

Author(s):

A. Elrefai, J. West, and K. Soudki

Publication:

Symposium Papers

Volume:

245

Abstract:

The monotonic flexural performance of reinforced concrete beams strengthened with external post-tensioned CFRP tendons was investigated. Variables include straight and double draped tendon profiles, and two post-tensioning conditions: at service load (50% of the yielding capacity - in-service beam) or after overloading to twice the steel reinforcement yield strain (overloaded beam). The beams were tested to failure in four-point bending. Experimental results indicated that the tendon profiles investigated did not affect the beam behavior. Overloading of the beam prior to post-tensioning had a significant effect on the deflection capacity of the beam, with a slight effect on the yield and ultimate capacities. A strain reduction approach, developed previously for unbonded steel tendons, was extended to model the beam behavior. The loading history of the beam prior to strengthening was explicitly accounted for in the model. The analytical predictions showed good agreement with the experimental values.

DOI:

10.14359/18766


Document: 

SP245-10

Date: 

April 1, 2007

Author(s):

Z. Wu, K. Iwashita, and X. Sun

Publication:

Symposium Papers

Volume:

245

Abstract:

Fiber reinforced polymer (FRP) composites have been widely used as externally bonded reinforcements to strengthen or rehabilitate deteriorated concrete structures. However, premature debonding failure due to the limitation of bond at the FRP-concrete interface is often encountered which limits FRP material potential for flexural strength increase. To minimize debonding failures and mechanical damage such as vehicular traffic and impact, etc., near surface mounted (NSM) FRP technology has emerged as another structural rehabilitation method. This study aims at evaluating a new strengthening using prestressed NSM carbon fiber reinforced polymer (CFRP) tendons. Although NSM FRP tendons are less susceptible to debonding than externally bonded FRP laminates, the load-carrying capacity of RC structures with NSM reinforcements is still likely to be governed by "premature" debonding failure. An experimental program with design variables such as prestress level and bonding agents was carried out to study the strengthening performance in terms of stiffness, cracking behavior and load-carrying capacity. The experimental results are presented and discussed in this paper. Experimentally validated bonding method is also proposed in this study.

DOI:

10.14359/18768


Document: 

SP245-02

Date: 

April 1, 2007

Author(s):

C.C. Choo, I.E. Harik, and H. Gesund

Publication:

Symposium Papers

Volume:

245

Abstract:

An analytical investigation was conducted to study the long term effects in the strength interaction (Pn-Mn) behavior of non-slender concrete columns prestressed with fiber reinforced polymer (FRP) tendons. Two long term concrete stress-strain behaviors were used and compared to the instantaneous or short term load. The expressions for the strength interaction of FRP prestressed concrete columns are derived from the strain compatibility and equilibrium conditions and are presented herein. Based on this preliminary investigation, it was concluded that the long term loadings and the tensile creep rupture of FRP tendons considerably influence the column strength. The results of the column cross sections considered herein show that disregarding long term effects may be conservative provided that rupture of FRP tendons does not occur in the columns.

DOI:

10.14359/18760


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