Determination of Structural Properties for RPG DiffusorBlox® Wall Configurations

Conducted by:

National Concrete Masonry Association
Research and Developement Laboratory

NATIONAL CONCRETE MASONRY ASSOCIATION

The National Concrete Masonry Association (NCMA) is a non-profit organization whose mission is to support and advance the common interests of its members in the manufacture, marketing, research, and application of concrete masonry products. The Association is an industry leader in providing technical assistance and education, marketing, research and development, and product and system innovation to its members and to the industry.

NCMA Technical Staff

Robert D. Thomas, Vice President of Engineering and Research
R. Lance Carter, P.E., Manager of Engineered Landscape Products
Dennis W. Graber, P.E., Director of Technical Publications
Jeffrey H. Greenwald, P.E., Director of Codes and Standard
Jason J. Thompson, Structural Engineer
Robert S. Zobel, Ph.D., Manager of Research and Development

NCMA RESEARCH AND DEVELOPMENT
LABORATORY

The NCMA Research and Development Laboratory is exclusively devoted to the scientific research and testing of concrete masonry products and systems. The Laboratory is staffed by professional engineers and technicians with many years of experience in the concrete masonry industry. The Laboratory is equipped to perform nearly any physical research or testing of concrete masonry units and assemblages. The Laboratory performs research and development work for both the Association and individual companies.

NCMA Research and Development Laboratory Staff

Robert S. Zobel, Ph.D., Manager of Research and Development
Donald L. Breeding, Laboratory Supervisor
Douglas H. Ross, Senior Laboratory Technician
Joynul Kahn, Laboratory Technician

2302 Horse Pen Road
Herndon, Virginia 20171-3499
(703) 713-1900

Table of Contents

1.0 Introduction
2.0 Scope of Work
3.0 Calculation Procedures

Appendix A

Determination of Structural Properties for RPG DiffusorBlox® Wall Configurations

1.0 Introduction
This report summarizes the calculations performed by The National Concrete Masonry Association Research and Development Laboratory to determine cross sectional properties of the various DiffusorBlox® concrete masonry units supplied by RPG Diffusor Systems, Incorporated.

2.0 Scope of Work
Four different DiffusorBlox® Systems were submitted to the NCMA Research and Development Laboratory for determination of cross sectional properties. Each of these wall systems is composed of two alternating units designated A or B. Both eight-inch and twelve-inch nominal wall thicknesses were evaluated. For each wall thickness there were two different systems; one with a slot and one without a slot.

These four systems are designated as shown below:

Each of the above four systems could be grouted in different ways giving rise to several different possible geometric configurations. Each of the possible configurations considered herein is designated below:

For each of the above-designated configurations (6 total) the following geometric properties were determined:

Cross Sectional Properties Determined for Each Unit

Net Cross Sectional Area, A_n (in²)
Net Volume, V_n (ft³)
Equivalent Thickness, T_e (inches)
Location of Neutral Axis, Y_bar (inches)
Out-of-Plane Moment of Inertia, I_x (in⁴)
Out-of-Plane Section Modulii, Sx_int and Sx_ext (in³)
Radius of Gyration, r_x (inches)

All cross sectional properties were determined using unit dimensions provided in detail CAD drawings supplied to NCMA by RPG, Incorporated. Drawings for each configuration evaluated can be found in Appendix A Figures A-1 and A-2.

3.0 Calculation Procedures

The overall dimensions for each unit were determined from the CAD drawings. Due to the unusual shape and particular features of each unit, certain portions of each cross section were not considered structurally. Guidance for testing concrete masonry units is provided in American Society for Testing and Materials (ASTM) C 140 "Standard Test Method for Sampling and Testing Concrete Masonry Units and Related Units". This test standard specifically states that projections with a height greater than the thickness should be removed prior to testing the unit in compression. The reason for this is that such projections are considered unsupported. With reference to the structural properties determined for each DiffusorBlox® configuration, all projections falling into the above category were not considered when computing section properties. Appendix A contains drawings for each DiffusorBlox® unit which identify the portions of each unit that were considered structurally depending on the portion of the unit that is or is not grouted solid.

8-Inch Unit Configurations

Figures A-3 and A-4, which refer to the non-slotted 8-inch A and B units, identified as configuration number 1, show the overall unit dimensions as well as the idealized cross section that was used for determining section properties for the grouted system.

Figure A-5, which refers to the slotted 8-inch A and B units, identified as configuration number 2, shows the overall unit dimensions as well as the idealized cross section that was used for determining section properties for the ungrouted 8-inch slotted system. The slotted block configuration does not allow for grouting and therefore the figure shows the units as ungrouted.

12-Inch Unit Configurations

Figures A-6, A-7, A-8, and A-9 all refer to the 12-inch non-slotted A Block. Figure A-6 contains overall dimensions for the non-slotted A unit. Figures A-7 through A-9 contain the idealized cross sections that were assumed for the A unit in configurations 3, 4, and 5 respectively. Figure A-10, A-11, A-12, and A-13 all refer to the 12-inch non-slotted B Block. Figure A-10 contains overall dimensions for the non-slotted B unit. Figures A-11 through A-13 contain the idealized cross sections that were assumed for the B unit in configurations 3, 4, and 5 respectively.

Figures A-14 and A-15 refer to the 12-inch slotted A Block. Figure A-14 contains overall dimensions for the slotted A unit. Figure A-15 contains the idealized cross section that was assumed for the A unit in configuration 6. Figures A-16 and A-17 refer to the 12-inch slotted B Block. Figure A-16 contains overall dimensions for the slotted B unit. Figure A-17 contains the idealized cross section that was assumed for the B unit in configuration 6.

Standards methods of engineering mechanics were employed to determine the required cross sectional properties for each unit.

Table I summarizes the section properties for each unit for each configuration as previously defined. It should be noted that these properties are based on the individual units that make up the designated configuration.

Click here to view Table 1.

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