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International Concrete Abstracts Portal

Showing 1-5 of 27 Abstracts search results

Document: 

92-S24

Date: 

March 1, 1995

Author(s):

ACI Committee 224

Publication:

Structural Journal

Volume:

92

Issue:

2

Abstract:

This report reviews the state of the art in design, construction, and mainte-nance of joints in concrete structures subjected to a wide variety of use and environmental conditions. In some cases, the option of eliminating joints is considered. Aspects of various joint sealant materials and jointing techniques are discussed. The reader is referred to ACI 504R for a more comprehensive treatment of sealant materials, and to ACI 224R for a broad discussion of the causes and control of cracking in concrete construction. Chapters in the report focus on various types of structures and structural elements with unique characteristics: buildings, bridges slabs on grade, tunnel linings, canal linings, precast concrete pipe, liquid-retaining structures, walls, and mass concrete.

DOI:

10.14359/9656


Document: 

JL81-16

Date: 

March 1, 1984

Author(s):

Frank J. Heger and Timothy McGrath

Publication:

Journal Proceedings

Volume:

81

Issue:

2

Abstract:

New semiempirical equations for crack width control in the vicinity of 0.01 in. (0.25 mm) applicable to flexural members such as pipe, box sections, and structural slabs are presented with comparisions with test results and equations in various codes and standards. The most common type of reinforcement in pipe and box sections is welded smooth wire fabric with main circumferential reinforcement at 2 to 4 inches on center and cross wires spaced at 6 to 8 inches on center. Typical reinforcement ratios are between 0.002 and 0.015. Most test results referenced in the paper are for this construction; however, pipes reinforced with smooth wire, smooth bars, deformed wire, deformed bars, and welded deformed wire fabric are used, and test results for pipe with all of these reinforcements are included. Furthermore, the use of ties improves crack control as shown by tests included in the programs described. The recommended design equations for crack control include the influence of surface roughness of reinforcement, area of concrete surrounding each bar or wire, and reinforcement ratio as major variables. It is shown that the nominal reinforcement stress at the specified maximum crack width decreases significantly with increasing reinforcement ratio p, a variation not considered in crack width control criteria found in current American reinforced concrete design codes. Because of this, existing crack width criteria can be unconservative in the design of concrete pipe, box sections, and other structural members with similar reinforcement. The design equations proposed in the paper have been adopted by the AASHTO Bridge Committee for use in Section 1.15.4 - Design of Precast Concrete Pipe - in the 1983 AASHTO Bridge Specification.

DOI:

10.14359/10652


Document: 

JL79-45

Date: 

November 1, 1982

Author(s):

Frank J. Heger and Timothy J. McGrath

Publication:

Journal Proceedings

Volume:

79

Issue:

6

Abstract:

New semiempirical equations for determining the shear strength of one-way flexural members are presented, together with comparisons with test results and with equations in various codes. The shear strength equations presented in this paper include the steel reinforcement ratio e and the ratio of shear span to depth of member M/Vd as major variables. They also include consideration of effects of curvature, and they provide a much more accurate determination of the shear strength of buried pipe, buried box sections, or pipe under three-edge bearing test load than other methods, such as equations in the ACI Building Code or the AASHTO Bridge Specification. They show that shear strength of buried pipe and box sections is about 50 percent higher than strengths obtained by the current Code equations, while shear strength in a three-edge bearing test is about 27.5 to over 100 percent of the strength given by the Code equations. The proposed equations also give more accurate shear strengths for other one-way flexural members such as footings and heavily loaded slabs.

DOI:

10.14359/10921


Document: 

JL77-43

Date: 

November 1, 1980

Author(s):

ACI Committee 517

Publication:

Journal Proceedings

Volume:

77

Issue:

6

Abstract:

Accelerated curing of concrete is used extensively in the production of precast concrete structural members, pipe, masonry units, and prestressed products. Steam curing is probably the most widely used method at the present time. Recent modifications and changes in this method are discussed, as well as the effect of the curing cycles. In addition to steam curing, the effect of variations in the concrete materials on accelerated curing is discussed, as are special cements and accelerators. Special treatments, including carbonation, accelerated drying, and heating concrete prior to molding, are also covered. Recently, some new accelerated curing methods have been developed. These include electrical, oil, and infrared curing. A section of this report deals exclusively with these methods.

DOI:

10.14359/7018


Document: 

JL67-63

Date: 

December 1, 1970

Author(s):

ACI . Committee 517

Publication:

Journal Proceedings

Volume:

67

Issue:

12

Abstract:

Recommendations are made for the application of steam at atmospheric res-sure to accelerate the curing of concrete products. The effects of h atmosp eric steam curing on the properties of concrete as discussed briefly. The current practices in applying this method of curing to precast concrete products, including concrete masonry units, several types of concrete pipe, prestressed and conventional reinforced structural units, and other miscellaneous items, are outlined for each product. General recommendations are given regarding construction and use of kilns, hoods, and other enclosures; layout of plant and piping; orientation of steam jets; and temperature recording and controlling equipment.

DOI:

10.14359/7326


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