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International Concrete Abstracts Portal

Showing 1-5 of 97 Abstracts search results

Document: 

SP188-77

Date: 

August 1, 1999

Author(s):

T. Shimomura, H. Mutsuyoshi, Z. Wu, A. Kobayashi, and T. Ishibashi

Publication:

Symposium Papers

Volume:

188

Abstract:

The technical research committee on continuous fiber (CF) sheet in the Japan Society of Civil Engineers (JSCE) has been engaged in making a new design system for concrete structures retrofitted with externally-bonded CF sheets since 1998. This paper presents the framework and some tentative contents of the design system. The system is on the basis of the concept of performance-based design, in which a structure to be retrofitted is systematically verified if it can satisfy any required performance items during the residual service life. Performance items of structures are verified in terms of the verification index which represents each performance item quantitatively. Evaluation methods for several performance items under development are shown in this paper regarding structural safety and serviceability of structures. The importance of precise prediction of peeling-off of CF sheet from concrete is emphasized. In the verification process of performance items, time-dependent performance changes due to environmental and loading attack are taken into account, so that structural and durability design are unified in a rational way.

DOI:

10.14359/5693


Document: 

SP188-84

Date: 

August 1, 1999

Author(s):

A. Khalifa, G. Tumialan, A. Nanni, and A. Belarbi

Publication:

Symposium Papers

Volume:

188

Abstract:

This paper presents the results of an experimental investigation on the response of continuous reinforced concrete (RC) beams with shear deficiencies, strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets. The experimental program consisted of nine full-scale, two-span, continuous beams with rectangular cross section. The tested beams were grouped into three series. Three beams, one from each series, were not strengthened and taken as reference beams, whereas, six beams were strengthened using different schemes. The variables investigated in this study included the amount of steel shear reinforcement, amount of CFRP, wrapping schemes, and 900/00 ply combination. The experimental results indicated that the contribution of externally bonded CFRP to the shear capacity of continuous RC beams is significant and is dependent on the tested variables. In addition, the test results were used to validate shear design algorithms. The proposed algorithms show good correlation with the test results and provided conservative estimates

DOI:

10.14359/5687


Document: 

SP188-64

Date: 

August 1, 1999

Author(s):

R. El-Hacha, G. Wight, and M. F. Green

Publication:

Symposium Papers

Volume:

188

Abstract:

When the serviceability or ultimate strength of a reinforced or prestressed concrete beam is assessed to be inadequate, fibre reinforced polymer (FRP) sheets may be suitable for strengthening these beams. FRP sheets exhibit high strength-to-weight ratios and are non-corrosive. When bonded to the tensile face of a concrete beam, FRP sheets supplement the flexural reinforcement of the beam, increasing the beam’s strength. To improve the efficiency of this strengthening technique, FRP sheets may be applied with an induced prestress. This paper presents results from an on-going experimental investigation that examines the effectiveness and feasibility of using prestressed carbon fiber reinforced polymer (CFRP) sheets to increase the capacity and improve the serviceability of damaged concrete members. A practical mechanical anchorage system for prestressing the CFRP sheets against the concrete beam is presented and the results of the prestressing process are discussed. The flexural behaviour of one 4.5 metre T-section prestressed concrete beam strengthened with prestressed sheets and loaded to failure at room temperature (22×C) is presented and compared to that of an unstrengthened control beam. The paper describes the on-going investigation into the behaviour of beams strengthened with prestressed CFRP sheets and tested at low temperature (-27×C). Aspects of the research program related to the long-term behaviour of beams strengthened with prestressed FRP are also discussed.

DOI:

10.14359/5668


Document: 

SP188-42

Date: 

August 1, 1999

Author(s):

G.P. Terrasi, U. Meier, and B. Burkhardt

Publication:

Symposium Papers

Volume:

188

Abstract:

The aim of this project is the production of a 28 m high CFRP-prestressed spun concrete pylon as a support for electric lines at the 110 kV voltage level (Duralight concept). It is intended to use this pylon as a support mast in a section of the 110 kV line of the Nordostschweizerische Kraftewerke (NOK, Power Company of North East Switzerland) Beznau-Baden. The fundamental advantage of this new design is the low weight in combination with an optimum corrosion resistance. The high corrosion resistance of the CFRP prestressing and shear reinforcement allows minimization of the concrete cover so that a cross-sectional wall thickness in the region of only 4 cm (1.6 inches) can be obtained. This is at present about 10 cm (4 inches) if steel reinforcement is used. The low weight of the CFRP reinforcement (the density of CFRP is only 1.6 g/cm3, which is a fifth of the density of steel) and its high tensile strength (CFRP pretensioning rods have a tensile strength of 3000 MPa, which is twice that of a prestressing steel) are also noteworthy. These two factors permit a weight reduction on the reinforcement side of 90% compared with conventional pre-stressed concrete construction. On the matrix side, high-strength spun concrete of strength class B110 is used. Owing to its high strength, it helps to achieve the stated minimization of the cross-sectional dimensions. The envisaged pylon weight of 4730 kg means a 45% weight reduction compared with the traditional steel reinforced spun concrete pylon. The transport and installation costs are thus lower and the expected life without maintenance is 50 years. This paper describes the technical fundamentals studied in a four year research program at the Swiss Federal Laboratories for Materials Testing and Research EMPA for designing and manufacturing this prototype pylon. The presented pilot project results from a close co-operation of the spun concrete element production plant SACAC with EMPA and the power company NOK.

DOI:

10.14359/5646


Document: 

SP188-56

Date: 

August 1, 1999

Author(s):

K. Brosens and D. Van Gemert

Publication:

Symposium Papers

Volume:

188

Abstract:

The anchorage of externally bonded reinforcement is extremely important. Due to high shear stress concentrations, premature failure is often initiated in the end zones. A non linear model to describe the phenomena at the end of the externally bonded reinforcement has been set up to allow a safe design of the anchoring capacity and the anchorage length. Appropriate safety factors have to be used to take into account the brittle behaviour of the system. A series of 24 direct shear tests were performed to verify the assumptions and to check the validity of the model. These test specimens consist of two concrete prisms bonded together with one, two or three layers of CFRP using different bonded lengths and widths.

DOI:

10.14359/5660


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