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Showing 1-5 of 11 Abstracts search results

Document: 

SP244-09

Date: 

May 1, 2007

Author(s):

C.-M. Aldea, B. Mobasher, and N. Jain

Publication:

Symposium Papers

Volume:

244

Abstract:

The research presented in this paper focuses on a cement-based matrix-grid (CMG) system developed for masonry rehabilitation. The objectives of the research and development program were to determine the mechanical properties of the CMG system and to assess its effectiveness for improving unreinforced masonry (URM) wall seismic performance from a load bearing capacity and deflection limits point of view. CMG system is a composite consisting of a sequence of layers of cement-based matrix and alkali resistant (AR) glass coated reinforcing grid. The experimental program included materials and structural tests. Tensile and flexural tests were carried out on unaged and aged composite to assess its long term durability up to the equivalent of approximately 129 years service life. Selected tensile test results are presented in this paper, whereas full details of materials tests are presented in a separate paper. Structural tests included in-plane shear concrete masonry unit (CMU) walls. Three composite configurations were explored and the results were compared with those obtained using various fiber reinforced polymer (FRP) systems overlay configurations also tested in in-plane shear. Retention of tensile properties over time was approximately 75-80% after the equivalent of approximately 50 years service life. Structural test results demonstrated the ability of the cement-based system to strengthen the walls, and showed superior performance of field CMG system compared to FRP alternatives. X-cracking failures were observed, there was no delamination of the system from the CMU walls, and the system held the masonry pier together at failure. Due to its advantages and unique properties this system is a potential alternative to traditional and new FRP masonry rehabilitation and strengthening techniques.

DOI:

10.14359/18757


Document: 

SP244-10

Date: 

May 1, 2007

Author(s):

S. Weiland, R. Ortlepp, A. Bruckner, and M. Curbach

Publication:

Symposium Papers

Volume:

244

Abstract:

Strengthening by textile reinforced concrete noticeably increases both the ultimate load bearing capacity as well as the serviceability - especially deflections, crack widths and crack spacing are reduced. Beside that there are still some practical applications. This paper will give an overview of the ongoing research work with this new composite material Textile Reinforced Concrete (TRC).

DOI:

10.14359/18758


Document: 

SP244-08

Date: 

May 1, 2007

Author(s):

B. Mobasher, N. Jain, C.-M. Aldea, and C. Soranakom

Publication:

Symposium Papers

Volume:

244

Abstract:

Mechanical properties of a cement-based matrix - grid (CMG) system developed for masonry rehabilitation are discussed. CMG system is a composite consisting of a sequence of layers of cement-based matrix and alkali resistant (AR)-glass coated reinforcing grid. The experimental program included tension and flexural tests of composites with special consideration to long term durability. Variables studied include effect of composite thickness, fabric orientation, and effect of accelerated aging on the tensile and flexural responses. Results indicate that samples in the cross machine direction (XMD) showed the best combination of high tensile strength (in excess of 5 MPa?0.725 ksi) and Ultimate strain value (2.36%) as compared to the machine direction (MD) with (5 MPa?0.725 ksi and ultimate strain of 1.8%). After 28 days of accelerated aging, tensile strengths reduced to about 3.87 MPa?0.56 ksi for the MD and XMD directions respectively, representing average reductions of 23% and 17%. In the flexural samples, cross machine samples (XMD) show a combination of high flexural strength (15-17 MPa?2.18-2.47 ksi) and Maximum deflection (of 15-22 mm?0.59-0.87 in) as compared to the MD samples. Higher stiffness of fabrics in the cross machine direction due to the manufacturing process was the source of such differences in behavior. The first crack strain in flexure is as much as the ultimate tensile strength in tension for many composites. A discussion of comparison of tensile and flexural stress measures is presented.

DOI:

10.14359/18756


Document: 

SP244

Date: 

May 1, 2007

Author(s):

Editor: Corina-Maria Alde / Sponsored by: ACI Committee 549

Publication:

Symposium Papers

Volume:

244

Abstract:

The main advantage of continuous fibers and textiles as reinforcements in cement-based composites is the enhancement of mechanical behavior. There is an improvement both in the tensile and flexural performance, as well as in the ductility of the cementitious composite. The diversity in terms of fabric making, fabric geometry, and input fiber types and yarns provides an opportunity for development of cement based composites and allows engineering of the performance of the final products for the desired requirements. Recognizing the increasing research interest in thin fiber-reinforced cement-based composites using textiles and hybrid systems (textiles and chopped fibers) and their emerging industrial applications, ACI Committee 549 sponsored a two-part technical session on “Thin Fiber and Textile Reinforced Cementitious Systems” at the ACI Spring 2005 Convention in New York. Ten papers were presented by invited international experts from Canada, Germany, Hong Kong, and the United States. This Special Publication (SP) contains ten papers which provide insight on the topics of state of the art of thin fiber and textile-reinforced cementitious systems both in academia and the industry. The topics of the papers cover experimental and theoretical materials aspects, such as the effect of different input fibers, fabric type, and construction and matrix on mechanical and long-term properties of the composite; experimental and theoretical considerations on yarn-to-matrix bond and load transfer; as well as applications of the cementitious composites proposed and examples of strengthening of reinforced concrete using textile-reinforced concrete. The future of thin fiber and textile-reinforced cementitious systems depends on their ability to compete with existing solutions and to identify new applications. Research and development efforts are required in the areas of process, design, and applications of textile-reinforced concrete.

DOI:

10.14359/18667


Document: 

SP244-04

Date: 

May 1, 2007

Author(s):

J. Hegger, O. Bruckermann, and S. Voss

Publication:

Symposium Papers

Volume:

244

Abstract:

Textile Reinforced Concrete (TRC) is a composite material taking advantage of the non-corrosiveness of fiber materials such as alkali-resistant glass (AR-glass), carbon or aramid in order to design slender and filigree structural elements. Compared to short cut fibers, a textile reinforcement features a higher effectiveness, because the fiber bundles are arranged in the direction of the main tensile stresses. These properties make TRC a promising construction material opening up new fields of application for concrete. In this paper, the results of experimental investigations and numerical simulations on TRC-components are presented. The load bearing behavior and important properties of TRC are described and the differences between the reinforcement materials AR-glass and carbon are elaborated. These differences are not only due to the different mechanical properties of the two materials but particularly the result of their different bond performance. Design models for the tensile strength and the bending capacity of TRC-components are given which have been derived on basis of the investigations.

DOI:

10.14359/18752


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