How Has the Modeling of Diaphragms for Structural Analysis Evolved?

This series of articles by Allen Adams, Senior Product Manager at Bentley Systems, provides insight into historical influences on structural analysis methodologies applied today.

History helps with understanding the origin of the how and why of commonly accepted practices and can assist when automated results require verification by manual calculation. Providing historical background helps answer confusion about the methods used, the results obtained, and clarify best practices and methods for particular conditions.

In addition to historical background, the series focuses on types of diaphragm models that can be used, and the corresponding results from each method. Engineers will discover various tips and critical factors to consider when using each type of diaphragm model to mitigate the shortcomings inherent with each.

Post 1: A History of Diaphragms
Learn about a brief history of the consideration of diaphragms in hand calculations and analysis programs to understand why diaphragms are considered the way they are in modern analysis programs and even in building codes and specifications.
Post 2: Types of Diaphragms
Read about the various types of diaphragms used in different types of analysis. This covers flexible diaphragms, rigid diaphragms, semirigid diaphragms and even pseudo-flexible diaphragms. Many of these are covered in the building codes of ASCE 7-16.
Post 3: Characteristics and Modeling of Flexible Diaphragms
Take a closer look at the characteristics and modeling of flexible diaphragms and how ASCE 7-16 Section 12.3.1.1 describes configurations.
Post 4: Classifying Rigid Diaphragms
This blog post dives into rigid diaphragms such as concrete slabs and how ASCE 7-16 Section 12.2.1.2 defines rigid.
Post 5: Special Considerations for Rigid Diaphragms
The rigid diaphragm assumption is popular because it is easy to specify, provides a convenient method for distributing wind and seismic story forces to the frames, and analyzes quickly. This post highlights some issues of concern that need to be understood and considered.
Post 6: Classifying Semirigid Diaphragms
Historically diaphragms have been considered to be either flexible or rigid but in this article helps better define semirigid which is increasingly needed for modern-day structures that require a more robust analysis.
Post 7: Characteristics and Modeling of Semirigid Diagrams
Learn about what is involved when it comes to modeling semirigid diaphragms as well as the characteristics they exhibit.
Post 8: Impact of Mesh Size in Semirigid Diaphragm Analysis
When modeling with a semirigid diaphragm, the question arises on the appropriate mesh size to use. What is the impact on the results if a coarse mesh is used versus a fine mesh?