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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 16 Abstracts search results
Document:
SP225-06
Date:
May 1, 2005
Author(s):
A. Scanlon
Publication:
Symposium Papers
Volume:
225
Abstract:
Current practice related to design of concrete structures for deflection control is reviewed. The paper discusses the limitations of the current code procedures based on minimum thickness rules and deflection calculations. Results are presented to demonstrate the sensitivity of deflections to span to depth ratio, sustained live load, and extent of cracking.
DOI:
10.14359/14378
SP225-11
March 1, 2005
D. T. Blackman and R. J. Frosch
Epoxy coated reinforcement is often used as a means of improving the durability of structures. The use of epoxy coating on reinforcement, however, has been shown to decrease bond strength resulting in increased crack spacing and crack widths relative to uncoated reinforcement. While the general influence of epoxy coating on cracking is recognized, there is scare data available to substantiate the magnitude of the effect. The objective of this research was to evaluate the influence of epoxy coating on crack spacing and crack widths. Ten specimens were subjected to a constant moment region, and the crack spacings and widths were measured over a range of reinforcement stress levels. Primary variables included the epoxy coating thickness, reinforcement spacing, and reinforcement stress. The results from this study showed that epoxy coating thickness affects both crack spacing and width. In general, as coating thickness is increased, crack width increased and crack spacing decreased. While crack control aimed at minimizing corrosion of reinforcing steel may not be of concern when epoxy coated steel is used, crack control remains an important design consideration for aesthetic reasons, for increasing structural durability, and for the design of water-retaining or other specialized structures.
10.14359/14383
SP225-08
R. H. Scott and A. W. Beeby
Current code provisions for deflection calculations in reinforced concrete beams and slabs are discussed. A comprehensive series of laboratory tests to investigate long term tension stiffening effects is summarised, results from which indicated that tension stiffening decays much more rapidly than was previously understood. Revised code provisions are proposed based on this finding.
10.14359/14380
SP225-10
P. R. Chakrabarti, PhD, PE, SE
Composite materials and high strength adhesives are becoming popular for various structural repair jobs. These materials provide good solutions for repairing, and retrofitting concrete structures. In this system repair work can be done within a short time, without using much labor, and the repair materials generally do not alter the geometric shapes of the original structural member. However, the interactive behavior (both short and long term) of un-bonded post-tensioned structural components, when repaired and retrofitted with composite materials is not yet properly understood. The current research was conducted to understand this. Eleven 12’-0" long beams B1 thru B11, were loaded close to their ultimate values. The tests were stopped based on three criteria: excessive cracking, or pre-stressing load reaching over 80%-85% fpu, or deflection reaching twice the allowable deflection. The cracked beams were repaired with varying amount of composite materials adhesives, and tested again. The beams were named B1CR, B2CR, B3EgR and so on, where CR represents repair with carbon FRP and EgR represents repair with e-glass FRP. The tests were stopped again based on the above three criteria. Using Carbon and E-glass FRP and adhesives, a very effective repairing and retrofitting system has been developed. The load carrying capacities and deflections of these beams and that of the original un-cracked beams were compared. Various repairing schemes were adopted. Attempts were made to find the minimum usage of the composite materials, prevent diagonal shear cracking, and prevent sudden compression failures. The changes in post-tensioning forces, the effect of having mild steel in the tension zone, and crack propagation at ultimate stage were recorded and discussed here.
10.14359/14382
SP225-09
K. B. Bondy, FACI
This paper critically examines the deflection criteria in Chapter 9 of the current ACI Building Code, ACI 318-02, with a particular focus on two-way non-prestressed slabs. The relationship between criteria based on deflection computations and arbitrary minimum thicknesses, which are independent of loading and concrete strength, are scrutinized. A numerical example is presented in which it is demonstrated that current code criteria can lead to unsatisfactory performance in heavily loaded slabs. Recommendations are made for changes to improve code deflection criteria.
10.14359/14381
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