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International Concrete Abstracts Portal

Showing 1-5 of 9 Abstracts search results

Document: 

SP226-02

Date: 

March 1, 2005

Author(s):

R. E. Barnett, J. E. Tanner, R. E. Klingner and F. H. Fouad

Publication:

Symposium Papers

Volume:

226

Abstract:

This paper is a summary of ACI 523.5R, which is a guide for using autoclaved aerated concrete panels. Its design provisions are non-mandatory, and are a synthesis of design recommendations from the Autoclaved Aerated Concrete Products Association, and from the results of research conducted at the University of Alabama at Birmingham (UAB), the University of Texas at Austin (UT Austin), and elsewhere. This paper discusses the design equations associated with the various typical structural uses of autoclaved aerated concrete. Those uses include flexural, axial compression, shear, bearing, bond and development of reinforcement and special seismic design provisions. The design provisions of this Guide are not intended for use with unreinforced, masonry-type AAC units. Design of those units is covered by provisions currently under development within the Masonry Standards Joint Committee.

DOI:

10.14359/14389


Document: 

SP226-05

Date: 

March 1, 2005

Author(s):

R. E. Klingner, J. E. Tanner, and J. L. Varela

Publication:

Symposium Papers

Volume:

226

Abstract:

This paper summarizes the final phases of the technical justification for proposed design provisions for AAC structures in the US. It is divided into two parts. The first part describes the design and testing of a two-story, full-scale AAC shear wall specimen that was designed and tested at The University of Texas at Austin, under reversed quasi-static loads representative of those experienced in a strong earthquake. The specimen withstood repeated reversed cycles to story drifts of about 0.3%, and displacement ductility ratios of about 3. The specimen conformed with the two main objectives. Those objectives were: 1) to show that the behavioral models developed for the shear walls also govern in a building; and 2) to demonstrate that a squat wall can exhibit failure governed by flexure. The second part describes the development of R and Cd factors for seismic design of AAC structures. The seismic force-reduction factor (R) specified in seismic design codes is intended to account for energy dissipation through inelastic deformation (ductility) and structural over-strength. The factor (R) is based on observation of the performance of different structural systems in previous strong earthquakes, on technical justification, and on tradition. For structures of autoclaved aerated concrete (AAC), the force-reduction factor (R) and the corresponding displacement-amplification factor (Cd) must be based on laboratory test results and numerical simulation of the response of AAC structures subjected to earthquake ground motions. The proposed factors must then be verified against the observed response of AAC structures in strong earthquakes. The objectives of this paper are: (1) to present a general procedure for selecting values of the factors (R) and (Cd) for use in the seismic design of structures; and (2) using that procedure, to propose preliminary values of the factors (R) and (Cd) for the seismic design of AAC shear-wall structures. The general procedure is based on comparing the predicted ductility and drift demands in AAC structures, as functions of the factors (R) and (Cd), with the ductility and drift capacities of AAC shear walls, as observed in quasi-static testing under reversed cyclic loads. Nonlinear numerical simulations are carried out using hysteretic load-displacement behavior based on test results, and using suites of natural and synthetic ground motions from different seismically active regions of the United States.

DOI:

10.14359/14392


Document: 

SP226-08

Date: 

March 1, 2005

Author(s):

N. Neithalath, J. Weiss, and J. Olek

Publication:

Symposium Papers

Volume:

226

Abstract:

Three classes of specialty cementitious materials were evaluated for their potential benefits in sound absorption including a Foamed Cellular Concrete (FCC) with density ranging from 400 – 700 kg/m3, Enhanced Porosity Concrete (EPC) incorporating 20-25% open porosity, and a Cellulose Cement Composite (CCC) with density 1400 – 1700 kg/m3. Cylindrical specimens of these materials were tested for acoustic absorption in an impedance tube. The FCC specimens showed absorption coefficients ranging from 0.20 to 0.30, the higher value for lower density specimens. The closed disconnected pore network of FCC hinders sound propagation, thereby resulting in a reduced absorption, even though the porosity is relatively high. The most beneficial acoustic absorption was observed for EPC mixtures. When gap-graded with proper aggregate sizes, these no-fines EPC mixtures dissipate sound energy inside the material through frictional losses. The cellulose fiber cement composites use cellulose fibers at high volume fractions (~7.5%), which are believed to provide continuous channels inside the material where the sound energy can be attenuated. By engineering the pore structure (by careful aggregate grading as in EPC, or incorporating porous inclusions like morphologically altered cellulose fibers) cementitious materials that have the potential for significant acoustic absorption could be developed.

DOI:

10.14359/14395


Document: 

SP226-07

Date: 

March 1, 2005

Author(s):

C. Shi, Y. Wu and M. Riefler

Publication:

Symposium Papers

Volume:

226

Abstract:

The use of lightweight concrete has many advantages over conventional concrete. The reduced self-weight of lightweight concrete will reduce gravity load and seismic inertial mass. The lightweight concrete reported here has compressive strengths from 8 to 50 MPa with dry densities from 800 to 1400 kg/m3, which is strong enough for any load-bearing and non-load-bearing applications. The compressive strength to flexural strength ratio increases as the compressive strength of the concrete increases. The introduction of a small amount of fiber does not affect the flexural strength and drying shrinkage of the concrete, but improves the ductility and handling properties of the product very significantly. The lightweight concrete has a higher moisture loss during drying, but a lower shrinkage than the normal weight concrete due to the buffer effect of the moisture in the lightweight aggregate. Properly designed fiber-reinforced ultra lightweight concrete can be easily cut, sawed and nailed like wood.

DOI:

10.14359/14394


Document: 

SP226-03

Date: 

March 1, 2005

Author(s):

F. H. Fouad and J. Dembowski

Publication:

Symposium Papers

Volume:

226

Abstract:

Autoclaved aerated concrete (AAC) is a lightweight uniform cellular material, first developed in Sweden in 1929. Since that time, plain and reinforced AAC building components have been widely used in Europe and other parts of the world. Until recently, however, AAC was relatively unknown to the United States precast construction market. Today, AAC prefabricated elements are gaining rapid acceptance in the United States due primarily to increasing energy cost, environmental concerns, and the ease of construction using AAC elements. Although AAC is a well-recognized building material in Europe, very little research work has been done on U.S.-produced AAC products. The primary objective of this work was to study the structural behavior of U.S.-made reinforced AAC elements. The laboratory test program included most commonly used reinforced AAC elements: floor panels, lintels, and wall panels. Two U.S. manufacturers supplied the AAC elements. Floor panels and lintels were tested in bending, whereas the wall panels were tested under axial or eccentric loading. The ultimate load capacity, cracking, deflection, and failure mode were observed and recorded for each test. The results provide a database that will be used to refine the analytical methods for the structural design of reinforced AAC elements. This information is needed to enhance AAC design methodologies and lay the foundation for establishing AAC as a reliable engineered construction material in the U.S.

DOI:

10.14359/14390


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