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Flexible Metal Deck Roof Diaphragms

D. Matthew Stuart, P.E., S.E., F.ASCE

Course Outline

A. General:

1. Description of diaphragms as a planar structural system.
2. Load path mechanisms.
3. Shear and flexural stiffness and resistance.
4. Deck termination and sidelap conditions.

B. Fasteners:

1. Welded connections.
2. Screw connections.
3. Power-Driven fasteners.
4. Button-Punched sidelaps.
5. Miscellaneous.

C. How to Fasten Steel Deck:

1. Welded connections.
2. Screw connections.
3. Power-Driven fasteners.
4. Button-Punched sidelaps.

D. Miscellaneous:

1. Special edge collector conditions.
2. Load tables.
3. Diaphragm deflection.
4. Supplemental overlayments.

E. Design Example.

F. Example of Roof Deck Attachment Diagram and Schedule.

This course includes a multiple choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will be able to:

Intended Audience

This course is intended for structural engineers and architects.

Benefit to Attendees

This course will enable a design professional to understand what a flexible metal deck diaphragm. In addition, this course will make it possible for the user to be able to design a simple roof deck diaphragm.

Course Introduction

Flexible metal deck diaphragms are essentially planar structural systems found in roofs and floors of buildings. They are comprised of interconnected units, attached to supporting members, such that the entire assembly possesses both in-plane shear strength and stiffness. The major components of a diaphragm include the individual deck panels, the structural members to which they are connected and the connecting devices or fasteners. Fastener types include welds, screws, power driven pins, or other mechanical devices that have a predictable capacity. The strength and stiffness of a diaphragm depends on the panel properties, the span arrangements, and the quality of the connections.

Course Content

In this lesson, you are required to download and study the following course content in PDF format:

Flexible Metal Deck Roof Diaphragms

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

If you have trouble reading any of the material on line, it is recommended that the course material be printed out for better resolution.

Course Summary

A diaphragm acts like a short deep beam. The maximum average shear occurs at the ends of the roof diaphragm. The maximum flexural chord forces occur along the extreme edges of a roof deck diaphragm. Zones near the mid-span of the roof are subjected to less unit shear therefore less diaphragm strength is required. The larger design shears at the ends of a diaphragm can be resisted by using both heavier gage panels and fewer connections or by more frequently connected lighter gage panels. However, from a practical constructability standpoint it is more common to use a single deck and connector type over an entire roof and increase the frequency of the connectors in order to resist greater in plane shear forces. The types of common fasteners used in a metal roof deck include welds, screws, power-driven connectors and button-punches. A roof deck attachment diagram and schedule should be provided on all projects in order to provide clear instructions to the deck installer concerning the required fastener type, spacing and extent.

Related Links

For additional information related to this subject, please visit the following websites or web pages:

Steel Deck Institute:


Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.