The Gold Standard in Steel Design

To view the figures and tables associated with this article, please refer to the flipbook above.

AISC recently released the 16th Edition Steel Construction Manual. The 16th edition celebrates nearly a century of publishing one of the most respected design aids in the construction industry.
The big changes in this edition are outlined here. While not everything new is mentioned here, a full list of changes and updates are included in the Preface to the 16th edition.

The AISC Committee on Manuals has dedicated the 16th edition to Dr. William (Bill) A. Thornton, former Chairman and long-time member of the committee. From 1985 until 2011, Bill served as the Chairman of the Committee on Manuals and oversaw the development of numerous Manual editions, including the First edition LRFD Manual and the 14th edition Manual. The 16th edition is only the second Manual ever to be dedicated and honors Bill’s many contributions to the industry.

The big story in the 16th edition starts in Part 2, General Design Considerations, which includes a wide range of guidance applicable to the design and construction of steel buildings. Significant changes were made to the tables that help guide users when specifying material: Table 2-4 includes the available grades of standard structural shapes, Table 2-5 includes available grades of plate and bar material, and Table 2-6 includes available grades of structural fasteners.
In addition to available material grades, the tables show preferred grades for different components. For every new Manual, AISC reviews the materials that are commonly used in steel construction to develop a list of preferred materials that reflect factors like ready availability, ease of ordering and delivery, and pricing. The use of preferred materials will help avoid material procurement issues and the potential for added cost.

An important distinction—preferred does not mean required. Any of the other applicable material specifications can be used successfully on a project, but the availability and cost-effectiveness of grades other than the preferred material specification should be confirmed with a fabricator prior to their specification.

Here are the major changes in the tables:

All shear connection design tables found in Part 10 have been updated from 36 ksi to 50 ksi connection material. Designers can use the tables to aid the design of typical shear connections using higher strength materials that are regularly used today.

The 2022 AISC Specification and 2020 RCSC Specification have adopted a new bolt specification, ASTM F3148. This new bolt grade has a tensile stress of 144 ksi, which puts its strength between Group 120 and Group 150 bolts. These new Group 144 bolts are an option in the shear connection tables throughout Part 10.

The Part 10 shear connection tables received a major revamp. The tables affected are:

Each of these tables is split into three subtables—one to verify the connection material strength, one to verify the shear transfer strength at the bolt holes, and one to verify the strength of the supported member when coped. The new tables will allow for an easier determination of the effective bolt shear transfer strength and the shear strength of the supported beam web when coped. See Table 10-1a in Figure 1.

Part 2 of the 16th edition includes expanded guidance for corrosion protection. A new section on galvanic corrosion was added to help identify situations where galvanic corrosion may be an issue when joining dissimilar metals. The new section lists conditions where galvanic corrosion is unlikely and where risk is high. A new table, Table 2-8 shown in Figure 2, provides a matrix of common construction metals and their steady state electrode potential as a basis to identify the potential for galvanic corrosion.

Additional changes in Part 2 includes a new section, Using the Manual Tables, that alerts users about interpolation within design tables, and a section on Simplified Determination of Required Strength that presents a simplification of the effective length method when a quick, conservative solution is desired.

When preparing contract documents, start with the updated section on Contract Document Information, which summarizes the requirements from the AISC Specification, the AISC Seismic Provisions, and the AISC Code of Standard Practice.

Solutions for a first- and second-order analysis of two beam-columns are now provided in Part 6. The new Table 6-5, shown in Figure 3, conveniently includes benchmark solutions for bending moments and deflections of a simply supported beam subjected to an axial load and transverse uniform load (Case 1), and a cantilevered member subjected to an axial force and transverse point load (Case 2).

These solutions are intended to validate solutions from computerized structural analysis or facilitate computation of required forces and deflections during design when the member configuration matches the given configurations.

Part 11, which in previous editions contained information for partially restrained (PR) moment connections, and Part 12, which included information for the design of fully restrained (FR) moment connections have been merged into the new Part 11, Moment Connections.

The new Part 12, Design of Simple Connections for Combined Forces, provides guidance on the design of typical shear connections subjected to axial or torsion forces in addition to shear forces.

Part 13, Design of Bracing Connections and Truss Connections, has several updates in the 16th edition. The Uniform Force Method has been expanded with a new “Special Case 4” that utilizes a single plate at the column connections. The new special case is useful where braces framing into the column web can create erection difficulties in the field, especially when columns have stiffener (continuity) plates in the web.

Part 13 also includes a new section covering chevron bracing connections, which require special consideration during both member and connection design due to a phenomenon called the “Chevron Effect.”

Lastly, Part 13 includes new material covering the design of horizontal bracing connections.

Part 9, Design of Connecting Elements, contains a new “Plastic Section Modulus for Coped W-Shapes” table as a companion to the coped beam elastic section modulus table in previous editions. The procedure for checking the available flexural strength of a beam with a cope at the top flange provided in Part 9 requires the calculation of the plastic bending moment of the coped section. This calculation is much simpler now using the coped beam plastic section modulus taken directly from the new table.

Tables 10-2 and 10-3 are used for the design of bolted/welded or all welded double-angle connections. For the weld between the angles and the support (“Welds B”), the weld design method was changed from the elastic method to the instantaneous center of rotation method. The updated design method will provide higher connection strengths. Additionally, these tables have a new weld geometry (“Welds C”) that includes additional lines of weld at the bottom of the angles, providing additional connection strength where needed.

The new Manual can be purchased at www.aisc.org/16thedition.

Margaret Matthew (matthew@aisc.org) is the AISC Director of Manuals. Yasmin Chaudhry (chaudhry@aisc.org) is a senior engineer in the AISC Steel Solutions Center.