Seismic Design For Ordinary Concentrically Braces Frames Spreadsheet

When it comes to seismic design, Ordinary Concentrically Braced Frames (OCBFs) are among the most cost-effective and widely used systems in low to moderate seismic regions. While they may not offer the same ductility and energy dissipation as Special Concentrically Braced Frames (SCBFs), OCBFs remain a practical and reliable choice for many structures. This article explores key design considerations, seismic performance, and optimization strategies for engineers working with OCBFs in seismic zones.

What Are Ordinary Concentrically Braced Frames?

Ordinary Concentrically Braced Frames (OCBFs) are structural systems that resist lateral loads primarily through axial forces in diagonal bracing members. These braces are connected at beam-column joints and designed to align concentrically, hence the name.

Unlike their “special” counterparts, OCBFs have less stringent detailing requirements and are typically easier and cheaper to construct. However, their seismic resistance is lower, which is why their use is restricted in high seismic regions according to design codes such as ASCE 7 and AISC 341.

Where Are OCBFs Most Commonly Used?

OCBFs are commonly used in:

• Low- to mid-rise commercial buildings

• Industrial facilities

• Warehouses

• Retrofit projects where budget constraints limit the use of special bracing systems

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