AISC Design Guide 10: Erection Bracing of Low-Rise Structural Steel Buildings

How to Apply AISC Design Guide 10: Erection Bracing of Low-Rise Structural Steel Buildings

Mastering the principles of erection bracing as outlined in AISC Design Guide 10 is crucial for structural engineers involved in low-rise steel construction. Proper temporary bracing ensures the safety of personnel and the integrity of the structure during the erection phase, preventing costly delays and potential failures. This guide will equip you with a practical framework to effectively implement the recommendations of Design Guide 10, enhancing your project management capabilities and reinforcing your reputation as a competent and safety-conscious engineer.

Before You Begin

Prerequisites:

• •Knowledge: Foundational understanding of structural mechanics, steel design principles (including load combinations and member capacities), and construction site safety protocols. Familiarity with basic structural analysis software is beneficial.
• •Tools/Resources: A copy of AISC Design Guide 10: Erection Bracing of Low-Rise Structural Steel Buildings, applicable building codes, project structural drawings, and structural analysis software.
• •Time Required: 2-4 hours for initial study and application to a typical low-rise building project, depending on complexity.

Step-by-Step Implementation

Step 1: Identify Erection Stages and Critical Loadings

Understand the sequence of steel erection for the specific project. Identify stages where temporary bracing is most critical, such as before permanent lateral load-resisting systems are fully connected or when individual members are being lifted and positioned. Recognize that erection loads can include wind, construction loads, and forces from erection equipment.

Step 2: Determine Required Bracing Locations and Types

Based on the erection sequence and identified critical stages, determine where temporary bracing is needed. AISC Design Guide 10 emphasizes diagonal bracing (cables or struts) and the potential use of structural elements like roof diaphragms (once sufficiently connected) for load transfer. Consider bracing bays and the need to stabilize columns and beams during erection.

Step 3: Calculate Temporary Bracing Forces

Analyze the forces that the temporary bracing system must resist. This involves calculating lateral loads (wind, erection forces) and their distribution, as well as vertical components transferred to bracing members. Use principles of statics and the geometry of the braced frame to determine tension and compression forces in bracing elements, as illustrated in the guide's examples. Remember to consider the load path from the point of application to the bracing anchorage.

Step 4: Select and Design Temporary Bracing Members

Choose appropriate materials for temporary bracing, such as steel cables or structural members. Design these members to safely withstand the calculated erection forces, considering their tensile or compressive capacity. Ensure that the capacity of these temporary members exceeds the required bracing forces with an appropriate margin of safety.

Step 5: Design Bracing Connections and Anchorages

Connections are critical for transferring loads effectively. Design connections for temporary bracing elements to their supporting structural members and to their anchorages. These connections must be capable of resisting the calculated forces. The guide highlights that temporary bracing connections may often be satisfied with a minimal number of fasteners, but this must be verified through calculation.

Step 6: Verify Stability of Braced Bays and Supporting Members

Beyond the bracing members themselves, ensure that the structural members to which the bracing is attached are stable. This includes checking columns for axial loads from the vertical component of bracing forces and verifying that beams and girders can transfer lateral loads to the bracing points without excessive deformation.

Step 7: Document the Erection Bracing Plan

Clearly document the proposed temporary bracing scheme, including bracing locations, member sizes, connection details, and calculated forces. This documentation is essential for communication with the erection contractor and for site safety management.

Common Pitfalls to Avoid

• • Underestimating Erection Loads: Assuming erection loads are negligible or can be resisted by permanent members before