Using Soft Metric Reinforcing Bars in ... - Page 7

For projects designed in metric units and using metric reinforcing bars, for example, designs by State Departments of Transportation, the furnishing of soft metric bars is a non-issue in the context of this report.

The major challenges will be associated with construction projects which are designed in inch-pound units, and the Rebar Fabricator desires to furnish soft metric bars.

Mills. Tags on bundles of soft metric bars being shipped to Fabricators should display or cross reference the equivalent inch-pound bar sizes. Certified Mill Test Reports should be in metric units and include equivalent inch-pound units.

Role of Rebar Fabricator. The Rebar Fabricator, who will be furnishing soft metric bars to construction projects which were originally designed in inch-pound units and will be built in inch-pound units, assumes a key role in supporting the mills' initiative toward production of only soft metric bars. First and foremost, the Rebar Fabricator will be obliged to serve as the communicator or facilitator to the Contractor, the Placer, and Architect/Engineer for such projects regarding the metric aspects. Besides direct communications, the Rebar Fabricator can follow-up and confirm the arrangements via the placing drawings and other submittals connected with non-metric projects.

Detailing. The Rebar Fabricator's placing drawings should include information that soft metric bars will be furnished for the particular non-metric project. If the placing drawings have already been prepared with designations of inch-pound bars, and it is subsequently decided that soft metric bars will be furnished to the project, a conversion table could be added to the placing drawings to cross reference the inch-pound bar sizes with the soft metric bar sizes. A table similar to Table 1 should suffice. For non-metric projects where the Rebar Fabricator intends to furnish metric bars at the outset, the placing drawings could be prepared with the metric bar designations. In this scenario also, a conversion table similar to Table 1 could be included on the placing drawings.

Fabrication. Since soft metric rebars are physically the same as corresponding sizes of inch-pound bars, all aspects of fabricating soft metric rebars will be identical to the fabricating practices used for inch-pound bars. CRSI has prepared and published Hook Details for ASTM Standard Metric Rebars -dimensions of end hooks, stirrup hooks, and seismic stirrup/tie hooks-soft converted values of the standard hook dimensions used for inch-pound bars. See Figure 2.

Bundling and Tagging. The same practices which a Rebar Fabricator uses for inch-pound bars can be used for bundling and tagging of soft metric bars. Tags on bundles of soft metric bars should include cross referencing of the equivalent inch-pound bar size(s). Lengths of bars and other dimensions can be stated in feet and inches. Weights of bundles of soft metric bars can be the same as the bundle weights used for inch-pound bars. Weights of bundles of inch-pound bars can be expressed in pounds.

Role of the Placer. Ironworkers will have to be made aware that the soft metric bars have different numbers to designate sizes of the bars. Training aids like Table 1 can be used. If more than one strength level (Grade of steel) is being used for the particular project, a training aid similar to Figure 1 can be reviewed. For non-metric construction projects, Ironworkers will still be working with dimensions in feet and inches. Placing practices for soft metric bars will be identical to those for inch-pound bars. For metric projects, i.e., projects designed in metric units and which will be built in metric units, Ironworkers will have to become familiar with the overall scheme of metric units. Discussion of such matters is outside the scope of this brief report. CRSI intends to publish a metric edition of its popular book, Placing Reinforcing Bars in 1998, which should aid Ironworkers to become familiar with metric units.

ROLE OF THE ARCHITECT/ENGINEER
New Projects in Inch-Pound Units. The Architect/ Engineer, designing new construction projects which will be built in inch-pound units, can greatly assist in a smooth transition toward acceptance and adoption of soft metric bars by initiating changes in the practice of preparing project drawings and project specifications.

A first step would be to include a conversion table on the project drawings or in the project specifications. The table would relate the inch-pound rebar sizes, which are called out on the project drawings, to the soft metric bar designations in the current ASTM Rebar Specifications. A conversion table similar to Table 1 should suffice.

A larger step by the Architect/Engineer would be to designate or label the reinforcing bars on project drawings and in project specifications with the metric bar designations - using the soft metric designations #10, #13, #16, #19, and so on in place of the inch-pound designations #3, #4, #5, #6, and so on. Spacings of bars, lap splice lengths or any other dimensions concerning reinforcing bars can still be expressed in feet and inches, i.e., retain the current dimensioning practice and units of feet and inches but change the practice of labeling bar sizes. Examples are:

New Projects in Metric Units. For new construction projects which are required to be designed in metric units, the thesis of this report is a non-issue. The Architect/Engineer would designate metric reinforcing bars as #10, #13, #16, etc., on project drawings and in the project specifications.