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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
SP161-01
Russel S. Fling
An 8000 sq ft (740 sq m) portion of an industrial building was load tested and vertical movements measured to an accuracy of 0.0043 in. (0.11 mm). Measured deflections were compared to those estimated before testing and to revised estimates after testing. Using simplified procedures and judicious estimates of design parameters, computed deflection normally should be within 40 percent of actual average deflection; the coefficient of variation should be less than 50 percent. With a complete and accurate selection of design parameters, the accuracy and statistical variability can be improved to 15 and 40 percent, respectively.
10.14359/1436
SP161-02
H. Solanki
Presents American and European design provisions for the control of deflections. Both minimum and computed versus allowable deflections of CEB-FIP Model Code (MC 1990) and ACI Code (ACI 318-89) are considered. The methods in both codes for predicting deflections and applying span/depth-thickness ratio are evaluated in design examples. Based on the simplified method for computing the long term deflection, no significant difference is found between the codes.
10.14359/1437
SP161-03
I. N. Robertson and C. J. Ambrose
The effective beam width method is used extensively for two- and three-dimensional analysis of flat plate structures subjected to combined gravity and lateral loading. Typically, the member stiffnesses are assumed constant throughout each span. This approach is shown to produce unreliable estimates of lateral drift and slab bending moments when compared with the results of a previously reported experimental program performed by researchers at the University of California at Berkeley. This paper presents a two-beam effective width model in which different section properties are used in negative and positive bending regions of the slab. Proposed slab stiffnesses for use in this model are based on a correlation between the experimental data and analytical analysis results. The application of the two-beam model using the proposed slab stiffness factors to a typical flat-plate structure is demonstrated in a worked example.
10.14359/1439
SP161-04
M. A. Polak, A. Scanlon, and D. V. Phillips
Presents available algorithms for deflection calculations of reinforced concrete (RC) beams, plates, and shells, using nonlinear finite element analysis. Detailed finite element formulations based on the layered approach and nonlinear constitutive laws are discussed and evaluated. The layered approach, through the rigorous treatment of the states of strain and stress can model complex behavior of both thin and thick plates. Further refinements can be incorporated using full three-dimensional modelling; this approach is briefly discussed in the paper. Alternative, simpler approaches based on the effective stiffness formulation are presented in the paper. The results of the finite element effective stiffness analyses are compared to both experimental results and the results of the layered analyses. Time-dependent effects of creep and shrinkage have a significant effect on deflections of reinforced concrete structures. The methods of incorporating these effects into layered and effective stiffness analyses are discussed in the paper. To demonstrate the usefulness of the finite element analysis, several examples of numerical results are presented and compared to experimental data. The examples include slabs with different loading, boundary, and reinforcement conditions.
10.14359/1441
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