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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 19 Abstracts search results
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
SP72-02
R. Lenschow, S. 0. Olesen, and S. Sahlin
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.
10.14359/6754
SP72-03
H. Aoyama and S. Otani
Each damaging earthquake produces certain aftershocks to earthquake engineering and research communities. The 1968 Tokachi-Oki earthquake triggered a series of research works in Japan. One significant accomplishment is the development of the methods to evaluate the earthquake resisting capacity of buildings. This paper describes a three-level procedure for existing low- to medium-rise (up to six stories high) reinforced concrete bui ldings. The higher is the level of procedure, the more complicated is the analysis, and the more reliable is the result. The earthquake resisting capacity is evaluated by the strength and ductility of an earthquake resisting elements. The strength and ductility of different types of elements were formu-lated on the basis of statistically analyzed experimental data and engineering judgements. The sequence of failure from stiff brittle elements to flexible ductile elements are taken into consideration. A good correlation was observed between the calculated capacity indeces and degrees of observed earthquake damage.
10.14359/6755
SP72-04
W. G. Corley, A. E. Fiorato, and R. G. Oesterle
This paper presents experimental data on strength and deformation capacity of isolated structural walls. The data are applicable to walls used as lateral load resisting elements for wind or earthquake forces. The objective is to describe variables that influence strength and deformation capacity. Effects of load history, section shape, vertical and horizontal reinforcement confinement reinforcement, moment-to-shear ratio, axial compressive stress, and concrete strength are considered. Deformation capacities obtained from tests are discussed in terms of overall limits on lateral drift.
10.14359/6756
SP72-05
Peter Gergely
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.
10.14359/6757
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