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International Concrete Abstracts Portal

Showing 1-5 of 23 Abstracts search results

Document: 

SP180-07

Date: 

October 1, 1998

Author(s):

J. A. den Uijl

Publication:

Symposium Papers

Volume:

180

Abstract:

From pull-out and push-in tests on specimens with short embedment length an empirical relation has been derived, which describes the local bond stress as a function of the local slip and steel stress change. With the help of this bond model the transfer length and the bi-linear relationship for the development length of a pretensioned strand (ACI Building Code 1989, CEB-FIP Model Code 1990) is simulated. It is also used to indicate the influence of strand yielding on the development length. For the estimation of the concrete cover and strand spacing required to prevent the occurrence of visible bond splitting cracks the response of the concrete to the radial displacement of the strand-to-concrete interface is analyzed by means of a so-called thick-walled-cylinder model. The radial interface displacement consists of transverse deformation of the strand coupled with steel stress change (Poisson effect) and wedging action caused by the shape of the strand (lack-of-fit effect) and surface roughness. Besides the section geometry, this model takes into account the softening behaviour of concrete loaded in tension. It is used to explain the influence of various parameters such as concrete cover, strand spacing, strand diameter and concrete strength on the bond properties of strand.

DOI:

10.14359/5876


Document: 

SP180-11

Date: 

October 1, 1998

Author(s):

A. Azizinamini

Publication:

Symposium Papers

Volume:

180

Abstract:

Safety concerns and a lack of test data on bond capacity of deformed reinforcing bars embedded in high-strength concrete are among the reasons for the AC1 318 building code imposing an arbitrary limitation of 10,000 psi (69 MPa) when calculating tension development and splice lengths. This limitation was first introduced in the 1989 revision of the AC1 3 18 building code. In an attempt to evaluate the impact of this limitation and develop provisions for its removal, an investigation was carried out at the University of Nebraska-Lincoln, partial result of which will be presented in this paper. Results of the investigation are used to discuss the differences that exist between normal and high strength concrete, develop hypotheses to explain these observed differences, and suggest alternatives for removal of the current concrete compressive limitations existing in the ACI 3 18 building code for calculating tension development and splice lengths. In this paper high strength concrete is defined as concrete with compressive strength exceeding 10,000 psi (69 MPa).

DOI:

10.14359/5880


Document: 

SP180-15

Date: 

October 1, 1998

Author(s):

E. Vintzileou and N. Psilla

Publication:

Symposium Papers

Volume:

180

Abstract:

This paper presents the results of an experimental investigation on the anchorage of deformed steel bars embedded in bed joints of masonry. The effect of bar diameter, anchorage length and vertical load on the mortar joint is investigated. Although the horizontal bars in masonry are under unfavourable conditions, such as low strength of mortar, small cover values, lack of bond at places where the bars pass over large holes of the masonry unit, tests have proved that embedment lengths as low as 30 to 40 times the bar diameter seem to be sufficient for the bars to develop their yield strength.

DOI:

10.14359/5884


Document: 

SP180-05

Date: 

October 1, 1998

Author(s):

G. Creazza, R. Di Marco, S. Russo and E. Siviero

Publication:

Symposium Papers

Volume:

180

Abstract:

This paper describes a theoretical and experimental analysis designed to characterize the initial branch of the bond-stress/slipping curves (5-s) for normal-strength and high-strength concretes. The theoretical analysis is used to interpret the results of experimental trials on reinforced concrete ties prepared with class 50 and 100 lMPa concrete mixtures and submitted to tensile forces without inducing any yield in the bar. The purpose of the investigation was to study any changes in bond behavior (over the limited range of slipping values considered) due to the better mechanical features of the 100 MPa concrete, and thus contribute to a better understanding of how high-strength reinforced concrete elements behave in a ser-viceability state.

DOI:

10.14359/5874


Document: 

SP180-22

Date: 

October 1, 1998

Author(s):

R. Tepfers

Publication:

Symposium Papers

Volume:

180

Abstract:

The Comite Euro-International du Beton (CEB) has set up under its Commission 2 “Material and Behavior Modelling” a Task Group TG 2/5 “Bond Models” with terms of reference to write a State-of-the-Art report. Chapter 8 in the report will deal with bond of non-metallic reinforcement, FRP. The work has been started using the Japanese State-of-the-Art knowledge presented in [5]. Now research experience is added. The bond concept elaborated for steel rebars is used to interpret the action of the FRP rods/bars. The different bond influencing factors are discussed also for FRP rods/bars. Comparison is performed with steel rebars. The bond of FRP rod/bar depend on more parameters than bond of steel. Variables of interest are form of rod/bar section, type of surface deformations and treatment, modulus of elasticity, Poissons ratio etc. Therefore it is appropriate to use the known bond action of deformed steel rebars in its different stages as a reference, when investigating the bond performance of FRP rods/bars.

DOI:

10.14359/5891


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