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Engineer's Notebook - Aids for the structural engineer's toolbox

Antiquated Structural Systems Series

Part 9a - Open Web Steel Joists
D. Matthew Stuart, P.E., S.E., F. ASCE, SECB

Additional tables for the article can be found by clicking on the links below, or additional tables and photos can be viewed in the PDF version of this article linked below.

For this series of articles, "antiquated" has been defined as meaning outmoded or discarded for reasons of age. In reality, however, most of the systems that have been discussed are no longer in use simply because they have been replaced by more innovative or more economical methods of construction.

This article, however, deals with a method of construction that is still very much in use today. Nevertheless, the historic, original construction practices described in this article may still be encountered in existing structures. Therefore, the primary purpose of this series of articles will be fulfilled: to compile and disseminate a resource of information to enable structural engineers to share their knowledge of existing structural systems that may no longer be in use, but are capable of being adapted or reanalyzed for safe reuse in the marketplace of today and the future.

Open Web Steel Joists

History

The author would first like to thank the Steel Joist Institute (SJI) for providing much of the material that was used in the development of this article. In fact, a brief history of open web joists is provided in the Catalog of Standard Specifications and Load Tables for Steel Joists and Joist Girders, published by SJI. A brief summary of this history is as follows:

1923 The first Warren type, open web truss/joist is manufactured using continuous round bars for the top and bottom chords, with a continuous bent round bar used for the web members.

1928 First standard specifications adopted after the formation of SJI. This initial type of open web steel joists was later identified as the SJ-Series.

1929 First load table published.

1953 Introduction of the longspan or L-Series joists for spans up to 96 feet with depths of up to 48 inches, which were jointly approved by AISC.

1959 Introduction of the S-Series joists, which replaced the SJ-Series joists. The allowable tensile strength was increased from 18 ksi to 20 ksi, and joist depths and spans were increased to 24 inches and 48 feet, respectively.

1961 Introduction of the J-Series joists, which replaced the S-Series joists. The allowable tensile strength was increased from 20 ksi to 22 ksi. Introduction of the LA-Series joists to replace the L-Series joists, which included an allowable tensile strength increase from 20 ksi to 22 ksi. Introduction of the H-Series joists, which provided an allowable tensile strength of 30 ksi.

1962 Introduction of the LH-Series joists, which provided yield strengths between 36 ksi and 50 ksi.

1965 Development of a single specification for the J- and H-Series joists by SJI and AISC.

1966 Introduction of the LJ-Series joists, which replaced the LA-Series joist. In addition, a single specification was developed for the LJ- and LH-Series joists.

1970 Introduction of the DLH- and DLJ-Series joists, which included depths up to 72 inches and spans up to 144 feet.

1978 Introduction of Joist Girders, including standard specifications and weight tables.

1986 Introduction of the K-Series joists, which replaced the H-Series joists.

1994 Introduction of the KCS joists, which provided a constant moment and shear capacity envelope across the entire length of the member.

SJI also recently published 80 Years of Open Web Steel Joist Construction. This publication includes a complete chronological listing of the standard specifications and load tables for all of the steel joists, and weight tables for the Joist Girders, previously made available by SJI over the time period from 1928 to 2008. This manual can be an invaluable tool for an engineer involved in the analysis of existing buildings constructed with open web steel joists.

In addition, there were also a number of joists produced by manufacturers that were either never members of SJI or joined it later. Some of these manufacturers in-clude: Ashland Steel Joists (manufactured by Ashland Steel Products Co., Inc - Ashland City, Tennessee); Vescom Structural Systems, Inc. - Westbury, New York; Ridgeway Joists (manufactured by Continental Steel Ltd. - Coquitlam, British Columbia); Northwest Joist Limited (a Division of Brittain Steel Limited - New Westminster, British Columbia); Cadmus Long Span and Joist Corporation (affiliated with Alexandria Iron Works, Inc. - Alexandria, Virginia); T-Chord Longspan Joists (manufactured by the Haven Busch Company - Grandville and Grand Rapids, Michigan); and the Macomber Steel Company - Canton, Ohio. Table 1 (please see online version; article end note provides web address) provides a summary description of the joists produced by these manufacturers.

In addition, some manufacturers, prior to becoming SJI members, produced products other than the historical stan-dard SJI joist series. Some of these manufacturers include: Truscon Steel Company - Youngstown, Ohio; Macmar and Kalmantruss joists (manufactured by Kalman Steel Corporation, a Subsidiary of Bethlehem Steel Company - Bethlehem, Pennsylvania); and Gabriel Steel Company - Detroit, Michigan. Table 2 (please see online version; artcile end note provides web address) provides a summary description of the joists produced by these manufacturers. In addition to the information provided in Table 2, it should be noted that Bethlehem Steel Company also produced cold formed joists with hat channel sections for the chord members, and Gabriel Steel Company also produced unique V-shaped top chord and single round bar bottom chord members.

Additional manufacturers not included in Tables 1 and 2 include: Berger Steel Company (double V-shaped chord mem-bers); Armco Steel (cold formed hat channel chord members); Raychord Corporation (cold formed hat channel and U-shaped chord members); Republic Steel (cold formed hat channel chord members); and USS AmBridge (cold formed U-shaped chord members).▪

Resource Material

80 Years of Open Web Steel Joist Construction; A Compilation of Specifications and Load Tables Since 1928; Steel Joist Institute; Myrtle Beach, South Carolina (2009).

Catalog of Standard Specifications, Load Tables and Weight Tables for Steel Joists and Joist Girders; 42nd Edition; Steel Joist Institute; Myrtle Beach, South Carolina (2007).

Miscellaneous Steel Joist and Joist Girder Specifications and Load Tables; SJI Archives; Steel Joist Institute, Technology, Engineering, and Education Center; Myrtle Beach, South Carolina

Another Resource

Robert Higgins, P.E., maintains a website that provides civil and structural engineering information in the following categories:

  • Out-of-print material that may be useful when working on existing facilities.
  • Older, usually conservative methods for solving technical problems.
  • Public domain documents that have limited availability.

In summary, this is content that is difficult to find anywhere else. To access it, visit www.SlideRuleEra.net.

D. Matthew Stuart, P.E., S.E., F. ASCE, SECB is licensed in 20 states. Matt currently works as a Senior Project Manager at the main office of CMX located in New Jersey, and also serves as Adjunct Professor for the Masters of Structural Engineering Program at Lehigh University, Bethlehem, PA. Mr. Stuart may be contacted at mstuart@CMXEngineering.com.

Watch for Part 9b in an upcoming issue.

Table 1 online version

Table 2 online version

Design Element Design Element

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