Design Guide for Low- and Medium-Rise Steel Buildings

How to Apply Design Guide for Low- and Medium-Rise Steel Buildings

Mastering the principles outlined in the AISC Design Guide for Low- and Medium-Rise Steel Buildings is crucial for engineers aiming to deliver cost-effective, structurally sound, and efficient steel structures. This guide provides practical strategies to optimize material usage, connection design, and overall building performance, directly impacting project budgets and client satisfaction. By integrating these concepts into your design workflow, you can enhance your professional reputation and ensure successful project outcomes.

Before You Begin

Prerequisites:

• • Knowledge: A solid understanding of fundamental structural engineering principles, including load calculations, material properties, and steel member behavior. Familiarity with the AISC Steel Construction Manual and relevant building codes (e.g., IBC, ASCE 7) is essential.
• • Tools/Resources: Access to the AISC Design Guide for Low- and Medium-Rise Steel Buildings, AISC Steel Construction Manual, structural analysis software, and relevant design software.
• • Time Required: Allow 2-4 hours for initial review and understanding of key concepts, with ongoing application time varying based on project complexity.

Step-by-Step Implementation

Step 1: Optimize Beam and Girder Spacing for Economy

Begin by strategically spacing beams and girders to minimize the quantity of steel required. The cost of fabrication and erection for individual members is largely fixed, so reducing the number of pieces directly translates to material cost savings. Consider wider spacing where practical, ensuring that the increased span of individual members does not lead to excessive deflection or vibration issues, which would necessitate more robust, and potentially costlier, solutions.

Step 2: Evaluate High-Strength Steel Utilization

Assess opportunities to employ higher-strength steels (e.g., ASTM A572 Grade 50) for beams and columns. This can offer a lower price-to-strength ratio compared to standard ASTM A36 steel, potentially reducing member weights and overall material quantities. For instance, a lighter high-strength steel section might effectively replace a heavier standard-strength steel member, leading to significant material cost savings.

Step 3: Minimize Moment and Special Connections

Carefully review the structural system to reduce the number of expensive rigid moment connections and specialized bracing connections. These connections are typically more complex and costly to fabricate and erect. Where possible, consider alternative framing schemes, such as utilizing spandrel beams as moment-resisting elements for lateral loads, or designing efficient, deep sections that inherently provide greater stiffness.

Step 4: Standardize Member Sizes and Repetitive Use

Prioritize the repetitive use of identical member sizes and shapes throughout the design. This standardization significantly streamlines detailing, fabrication, and erection processes, leading to reduced labor costs and improved construction efficiency. Even in areas where beam spacing must be adjusted, consider using a standard section with a reduced number of shear studs in composite floor systems.

Step 5: Apply Live Load Reductions Strategically

Implement live load reductions as permitted by applicable codes for member design, particularly for longer spans or larger tributary areas. While this might not drastically alter the weight of smaller filler beams, it can lead to substantial savings in the weight of girders, columns, and foundation elements, contributing to overall project cost reduction.

Step 6: Consider Composite Design for Floor Systems

Explore the use of composite floor systems, which combine steel beams with concrete slabs acting compositely. This approach can enhance floor load capacity and stiffness, potentially allowing for shallower floor depths or longer spans. Evaluate both shored and unshored construction methods to determine the most economical and practical solution for the project.

Step 7: Address Serviceability and Vibration Concerns

While focusing on strength and economy, ensure that serviceability criteria, particularly floor vibration, are adequately addressed. The guide provides methods for assessing vibration and