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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 13 Abstracts search results
Document:
SP161-08
Date:
April 1, 1996
Author(s):
M. A. Bhatti, B. Lin, and J. P. Idelin Molinas Vega
Publication:
Symposium Papers
Volume:
161
Abstract:
The usual design practice for analysis of reinforced concrete slabs with openings is to neglect holes if their area is less than 10- 12% of the total slab area. This practice is based in part on studies conducted in early sixties regarding the effects of holes on the elastic behavior of plates. A literature survey revealed no specific studies regarding the effects of holes on deflection and strength of reinforced concrete slabs with openings. This paper presents a numerical study of the effects of openings of different sizes on the behavior of reinforced concrete slabs. A nonlinear finite element model for reinforced concrete slabs is developed using three dimensional brick elements taking into account cracking and crushing of concrete, and plasticity of both reinforcement and concrete. Distributed and concentrated loads are applied to slabs until collapse. Results show that when slabs are subjected to uniformly distributed loads, the openings do not have much effect on their strength and serviceability. The openings should be considered, however, when designing slabs subjected to concentrated loading where the opening ratios are larger than 2.5% .
DOI:
10.14359/10055
SP161
Editors: Edward G. Nawy and Debrethann R. Cagley
SP-161 All the papers presented in this publication were reviewed by recognized experts in accordance with the ACI review procedures. It is hoped that designers, constructors, and codifying bodies will be able to draw on the material presented in this volume in conjunction with the ACI 435 Committee Report "Control of Deflection in Concrete Structures", in improving the long-term deflection behavior and performance of concrete constructed facilities.
10.14359/14201
SP161-12
T. S. Lok and J. S. Pei
Load-deflection responses of simply-supported (SS) and simply-supported all-round (SSAR) steel fiber reinforced (SFR) concrete square slabs subjected to a central point load have been obtained. The slabs measured 810 mm x 810 mm x 50 mm. The elastic response alone is of particular interest and presented here because this has a major influence on the durability of SFR concrete. Results for each SFR concrete slab are compared with theoretical elastic solutions for both boundary conditions and also with the behavior of identical plain concrete and weldmesh reinforced slabs in each case. A modified depth instead of the full slab thickness is proposed for estimating the elastic response of SFR slabs for the two boundary conditions; the depth effectively reduces the elastic stiffness of the cross section. The limiting load level at which the initial response may be considered as linear is established, but the limiting load is dependent on the behavior of the slab. This limiting load level is compared with results calculated from a modified empirical expression for predicting the load at which first crack is perceived to occur. In the empirical expression, a triangular linear stress block with the modified depth is used. On average, the modified depth is about 0.7 times the overall SFR concrete slab thickness for both the SS and SSAR boundary cases. The influence of fiber type, fiber concentration, and boundary condition on the modified depth is not significant.
10.14359/1507
SP161-11
R. Ganeswaran and B. V. Rangan
Presents the results of a study on long-term deformations of high-strength concrete. Shrinkage and creep deformations of high-strength concretes, as well as deflections of beams and one-way slabs made of high- strength concrete are reported. The measured deformations are compared with the values predicted by the ACI method, the CEB-FIP Model Code, and the Australian Practice. The comparison shows several discrepancies between measured and predicted values.
10.14359/1505
SP161-10
P. R. Chakrabarti
In this project, an attempt is made to study the instantaneous load- deflection behavior of partially prestressed beams with unbonded post- tensioning tendons. Thirty-three beams with the following variables were tested: different mixes of reinforcing and prestressing steel, T-beams and rectangular beams, normal and high-strength concrete, low and high ratios of span/depth, and different effective stresses in tendons. Cracking was observed and deflections measured at precracking and postcracking stages. A suitable method for deflection calculation at precracking and postcracking stages is proposed. The proposed deflections and the deflections obtained by current ACI 318-89/92 code equations are compared with the measured deflections.
10.14359/1503
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