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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:
SP161-06
Date:
April 1, 1996
Author(s):
P. L. Fuhr, D. R. Huston, and A. J. McPadden
Publication:
Symposium Papers
Volume:
161
Abstract:
An optical technique has been developed whereby two angles and linear displacement can be simultaneously measured in a noncontact manner. The method depends upon the usage of a diffraction grating with linear variation of period along its length. The grating is attached to a structure at a point of interest, while all other system components are placed at a remote location. Evaluation of this measurement technique has been demonstrated on a laboratory- based structure, which simulated conditions found at deep trench (or tunnel) walls or bracing systems. In a construction site configuration, this sensor allows the user to determine if the walls are undergoing structural deformation. In addition, the magnitude of deformation may be measured and alarm conditions may be monitored. Experimental results obtained using this technique are presented and compared with theory.
DOI:
10.14359/1445
SP161-09
N. J. Gardner and J. Zhang
North American design codes offer two methods to insure deflection serviceability. The design engineer can calculate the live load and sustained load deflections and check that they are less than code specified limits. Alternatively, the codes give maximum span/depth ratios for which serviceability can be assumed to be satisfied and deflections do not need to be calculated. However, the span/depth provisions of ACI 318-89 and CSA A23.3- M84 do not consider many of the factors which influence the deflection behavior of reinforced concrete beams and may not be consistent with the code specified deflection limits. The immediate and long term deflections of reinforced concrete beams were calculated using a layered, nonlinear finite element model. The long term deflections were calculated by a hybrid technique using an effective reduced modulus for concrete creep and a conventional finite element, time-dependent load vector for shrinkage and tensile cracking. The modelling technique was verified using the extensive experimental data of Christiansen. Span/depth ratios are proposed, which include the effects of concrete strength, tension steel ratio, and compression steel ratio, for incremental deflection criteria of span/500 and span/250. Long term deflection multipliers are given for sustained moments of 30, 50, and 70 percent of the design ultimate moment.
10.14359/1449
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
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
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