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International Concrete Abstracts Portal

Showing 1-5 of 19 Abstracts search results

Document: 

SP72-05

Date: 

December 1, 1981

Author(s):

Peter Gergely

Publication:

Symposium Papers

Volume:

72

Abstract:

The effects of the thickness of concrete cover on corrosion, crack width, fire protection, and development length are examined. Increased cover thickness and concrete with low permeability are necessary for corrosion protection, though the former leads to wider surface cracks. However, transverse crack-ing and the width of cracks usually do not aggravate the corrosion problem. Thus it is not advisable in most structures to limit the surface crack width in order to avoid or reduce corrosion. Longitudinal cracks along the bar can cause rapid corrosion. The only reason for surface crack width limitation in buildings is appearance; fortunately recommended limits can usually be met even with heavy covers unless the beam is wide and the bar spacing is large. Fire damage to most indeterminate structures is dictated by thermal forces not as much by temperature rise of the steel. Determinate structures fail when a section loses its capacity but moderate covers are usually sufficient for fire protection of the steel. Crack width limits and cover requirements in current codes should be examined.

DOI:

10.14359/6757


Document: 

SP72-01

Date: 

December 1, 1981

Author(s):

Ivan M. Viest

Publication:

Symposium Papers

Volume:

72

Abstract:

Load and Resistance Factor Design is a major advance toward rational design of steel framed buildings. It combines the limit states of strength and serviceability with a modern probability-based approach to structural reliability. After a historical introduction, the method is defined and a generalized LRFD format developed. The discussion centers on sources of variability in design, on limit states and on probabilistic concepts underlying the numerical values of load and resistance fac-tors. The results of a design evaluation of LRFD are presented and steps are described that are being taken toward future adoption of the method into the AISC Specification.

DOI:

10.14359/6753


Document: 

SP72-11

Date: 

December 1, 1981

Author(s):

J. Warwaruk

Publication:

Symposium Papers

Volume:

72

Abstract:

Over the last two decades a world-wide interest in the response of structural members subjected to torsion has developed, This is due principally to improvements both in the knowledge of the structural action of reinforced concrete members and in design procedures, particularly the strength design process. The objective of this "overview" paper is to summarize and present recent significant developments that have occurred in the area of torsion-al response of members and in the process of design of such members for torsional effects. The paper includes a short historical review but the emphasis is on recent research and design techniques.

DOI:

10.14359/6763


Document: 

SP72-02

Date: 

December 1, 1981

Author(s):

R. Lenschow, S. 0. Olesen, and S. Sahlin

Publication:

Symposium Papers

Volume:

72

Abstract:

The use of concrete structures in off shore installations offers a challenge to structural engi-neers. Due to lack of direct experience from comparab-le, earlier concrete structures, it has often been necessary to rely more heavily on knowledge of the basic properties of concrete under extreme conditions. The paper describes a few examples. Inclined slipforming of large concrete tower structures requires creep and shrinkage deformations within the first few days to be accurately estimated taking into account the effect of heat generation and age on the strength and stiffness properties of the concrete. Off shore structures are generally exposed to fatigue loading from waves. Wave load histograms from the North Sea are presented and the problems in estimating the fatigue damage to the concrete is described. The effect of concentrated impact loads on slabs and cylindrical shells is treated. FEM analysis as well as laboratory tests have been performed. Finally, the strength of concrete under high water pressure is discussed.

DOI:

10.14359/6754


Document: 

SP72-09

Date: 

December 1, 1981

Author(s):

J. G. MacGregor

Publication:

Symposium Papers

Volume:

72

Abstract:

The ACI Building Code has become more and more complex as engineers and plan checkers have insisted that every eventuality be covered in the code. Three possible ways of simplifying codes are discussed. These include: (a) rearrangement of the code by components rather than stress states, (b) use of a performance code format plus a recommended practice and (c) use of a two-tiered code. The paper suggests that (a) and (c) are most likely to be successful at this time.

DOI:

10.14359/6761


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