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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 17 Abstracts search results
Document:
SP133-09
Date:
September 1, 1992
Author(s):
Shivaprasad T. Kudlapur and Edward F. Nawy
Publication:
Symposium Papers
Volume:
133
Abstract:
Studies are limited on the early age performance of high-strength cold weather concretes and their shear strength interaction in cold weather. This paper presents shear transfer strength characteristics between regular high-strength concrete and (i) methyl methacrylate-based polymer concrete and (ii) magnesium phosphate based concrete in subfreezing temperatures. Analytical expressions were developed based on shear transfer hypothesis and verified by experimental results. The experimental study included tests on cylinders and L-shaped push off specimens to determine the early age shear interlock and shear frictional resistance between high-strength regular portland cement concrete and cold weather high-strength concretes as is experienced in rehabilitation of bridge decks and other infrastructure systems. Studies indicated that at early age of 24 hours, shear transfer strength of 1400 psi can be obtained with the use of appropriate material and shear reinforcement. The study also indicated the ACI 318-89 code limits on the shear-friction strength are too conservative even at early ages for high-strength cold weather concretes.
DOI:
10.14359/2872
SP133-10
Sami W. Tabsh
Concrete bridges in the United States constitute about fifty percent of the total number of highway bridges. Recent studies indicate that many of these bridges deteriorate due to age, corrosion of reinforcement, fatigue, cracking and spalling of concrete, and/or human error. Limited funds are available for rehabilitation, strengthening, and replacement. Therefore, there is a need for methods to identify the parts of concrete girder bridges most sensitive to damage using reliability models. This may help lower the costs of checking, inspection, and repair. Load and resistance sensitivity functions for the ultimate flexural capacity limit state of simply supported bridge girders are included. The study indicates that the reliability of bridge girders depends mostly on the strength and location of steel.
10.14359/2875
SP133-01
Edward G. Nawy
This paper presents the state of the art in evaluating flexural crack development and control of macrocracking. It is based on extensive research over the past five decades, in the United States and overseas, in the area of macrocracking in reinforced and prestressed concrete beams and in two-way action slabs and plates With the advent of limit states theories that generally lead to economic proportioning of members, control of cracking has become essential to maintain the integrity and esthetics of concrete structures. The trend is stronger than ever in better utilization of current concrete strengths, use of higher strength concretes that include super-strength concretes of 20,000 psi (138 MPa) compressive strength and higher, and increased application of prestressed concrete concepts. All these trends require closer control of serviceability requirements in cracking and deflection. Design expressions are given for the control of cracking in reinforced concrete beams and thick one-way slabs; prestressed, pretensioned, and post-tensioned flanged beams; and reinforced concrete two-way action structural floor slabs and plates. In addition, recommendations are given for the maximum tolerable flexural crack widths in concrete elements.
10.14359/3131
SP133-02
Andrew Scanlon and Ross B. Corotis
The American Concrete Institute, Standard 318, Building Code Requirements for Reinforced Concrete have permitted the design of reinforced concrete structures in accordance with limit state principles using load and resistance factors since 1963. A probabilistic assessment of these factors and implied safety levels is made, along with consideration of alternate factor values and formats. A discussion of issues related to construction safety and safety of existing structures is included.
10.14359/3138
SP133-03
M. Z. Cohn an Z. Lounis
An approach that integrates serviceability control with the ultimate limit state (ULS) design is presented. Each serviceability limit (SLS) is related to an amount of moment redistribution that corresponds to the permissible values of the crack widths, deflections, and stresses under service conditions. A design that simultaneously satisfies the specified ULS and SLS criteria may be obtained if the assigned moment redistribution percentages y do not exceed the recommended redistribution limits for serviceability control. The proposed approach integrates all relevant design criteria via the moment redistribution percentage y, and may be used within the framework of ACI 318-89 or other standard codes. The approach allows a direct extension to existing nonlinear, multicriteria, and optimal design methods.
10.14359/3143
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