Steel Design Module 1 - ANSI/AISC 360-16 Standard - AulaGEO

Module Detail: This module introduces the course on Specialization in Steel, focusing on the design and analysis of special moment frames using structural software like ETABS and manual calculations with MATLAB. It covers various aspects of a real infrastructure project, including floor plans, elevation views, load calculations, and connection designs.

Lesson Summary: In this introductory lesson, Engineer Juan Orozco welcomes participants to the Specialization in Steel course, specifically focusing on special moment frames. The lesson begins with an overview of a real infrastructure project, detailing the layout of a building with four apartments, each with specific features like bedrooms, kitchens, and living areas. The structural design involves analyzing spans between columns and using the ETABS software to model and study the building's behavior under loads.

The course will cover the AISC 360-16 standard for structural design and the ASCE 41-17 for seismic-resistant design. Manual calculations will be performed using MATLAB, with results compared to those from ETABS. Key components such as load-bearing beams, purlins, floor slabs, shear connectors, and various types of connections (moment and shear) will be analyzed and designed. The lesson also highlights the importance of accurately designing staircases and their connections to ensure structural integrity. Throughout the course, participants will gain hands-on experience with real-world applications, reinforcing their understanding of steel structure design principles.

Module Detail: This module initiates the Specialization Course in Steel, focusing on the design and analysis of flexural members in accordance with the ANSI/AISC 360-16 standard. It covers the classification of flexural sections, local and lateral buckling phenomena, and shear design.

Lesson Summary: In this lesson, we introduce Module 1 of the Specialization Course in Steel, focusing on special moment frames and the design of flexural members. The course begins with an in-depth study of the ANSI/AISC 360-16 standard, examining the classification of flexural sections into compact, non-compact, and slender categories. We explore local buckling in flexural members, including buckling in the flanges and web, and the width/thickness criteria necessary for stability.

The lesson also delves into lateral torsional buckling, analyzing the unbraced length (Lb) and its impact on the nominal and plastic moments. We discuss the significance of lengths Lp and Lr and their formulations in both the inelastic and elastic ranges. Additionally, the Cb factor is explained, highlighting its role in amplifying the nominal moment resistance of sections.

The module concludes with a detailed look at shear design, providing a comprehensive understanding of the forces and checks required for ensuring structural integrity. This lesson sets the foundation for the entire course, preparing participants for evaluations and practical applications of the concepts learned.

Each module includes evaluations, featuring theory questions, true/false statements, and practical exercises based on the AISC 360 standard and flexural member calculations. This lesson is an essential starting point for mastering the principles of steel structure design.

Module Detail: This module introduces the Specialization Course in Steel, focusing on the design and analysis of flexural members according to the ANSI/AISC 360-16 standard. It covers the fundamental concepts of flexural members, their stress analysis, and the classification of sections under bending.

Lesson Summary: In this lesson, we begin Module 1 of the Specialization Course in Steel: Special Moment Frames. The focus is on the design of flexural members based on the ANSI/AISC 360-16 standard. Flexural members, typically horizontal prismatic sections, support loads perpendicular to their longitudinal axis, resulting in bending and shear stresses.

We examine a typical horizontal member subjected to a uniformly distributed load and analyze the resulting bending moments and shear forces. The lesson covers the stress analysis of I-beams or H-sections under uniformly distributed loads, emphasizing the compression and tension experienced by the flanges and the role of the neutral axis.

We delve into the classification of sections under bending, explaining the four types of sections:

• Type 1: Plastic designs and seismic designs capable of developing plastic moments and sustaining necessary inelastic rotations for moment redistribution.

• Type 2: Compact sections that achieve plastic moments but have limited inelastic rotation capacity, suitable for static loads and reduced seismic performance factors.

• Type 3: Non-compact sections that initiate plastic flow but lack inelastic rotation capacity, typically failing due to inelastic buckling.

• Type 4: Slender sections that fail due to local elastic buckling without reaching the yield point.

Each section type is discussed in detail, highlighting their characteristics and limitations. This foundational lesson sets the stage for understanding the behavior and design requirements of flexural members in steel structures, preparing participants for more advanced topics in the course.

Module Detail: This module focuses on the critical topic of local buckling in flexural members as defined by the AISC 360-16 standard. It provides an in-depth analysis of flange and web buckling, essential for ensuring the structural integrity and performance of steel beams under load.

Lesson Summary: In this lesson, we continue the Specialization Course in Steel, concentrating on local buckling in flexural members. Local buckling occurs in the flanges and web of beams under bending, potentially preventing the development of plastic moments.

Flange Buckling: Local buckling in the compression flange can occur if it is too thin, leading to instability. This prevents the beam from achieving its plastic moment. We explore a beam section subjected to moments, highlighting the tension in the bottom flange and compression in the top flange. Thin compression flanges are prone to buckling, thus failing to reach the plastic moment.

Web Buckling: Local failure in the web occurs at points of concentrated loads and supports, leading to web crushing or buckling between the flanges. The standard provides checks to control these failures.

Width/Thickness Ratio: The standard defines the width/thickness ratio for flanges and webs, using parameters like Lamda (λ), which depends on whether the element is braced. Lamda p, Lamda ps, and Lamda r are upper limits for compact, seismic compact, and non-compact sections, respectively.

We use graphical and tabular methods to verify these ratios. For instance, Lamda is calculated as the ratio of the flange width (b) to its thickness (t). If Lamda is less than Lamda p, the section is compact. If Lamda is between Lamda p and Lamda r, it is non-compact, and if greater than Lamda r, the section is slender.

Practical Applications: The lesson includes practical examples and references to specific pages in the AISC standard, both in English and Spanish, to ensure thorough understanding and application. We examine how different sections (I, channel, and T) meet these criteria and how these classifications impact their ability to develop plastic moments.

Summary: By understanding local buckling in flanges and webs and verifying the width/thickness ratio, engineers can design safer and more efficient steel structures. This lesson provides the foundational knowledge necessary to prevent local failures and achieve optimal structural performance.

Module Detail: This module delves into the critical topic of local buckling in flexural members, focusing on web and flange behavior under load conditions. It includes analysis methods and checks as per the ANSI/AISC 360-16 standard, helping engineers ensure the structural integrity of steel sections.

Lesson Summary: In this lesson, we continue our discussion on local buckling in flexural members. We begin by examining local failure in the web, which often occurs at points of concentrated loads and supports due to web crushing or buckling between the flanges. These failures can prevent profiles from reaching their plastic moment capacity.

The lesson covers the width/thickness ratio criteria for webs, explaining how the standard provides graphical and tabular methods to verify this ratio. Key equations are introduced, such as Lamda (λ), calculated as the ratio of the height (h) to the thickness (tw) of the web. For instance, Lamda p is given by 3.76 times the square root of the modulus of elasticity divided by the yield stress. If Lamda is within certain ranges, the section may be classified as compact or non-compact, affecting its ability to develop plastic moments.

We explore how to determine whether a section is compact, non-compact, or slender by analyzing the width/thickness ratio and referencing the relevant tables from the standard. For I-sections and channel sections, the moment capacity and the width/thickness ratio of both webs and flanges are crucial for classification.

In summary, this lesson provides a detailed approach to understanding and verifying local buckling in flexural members, using real-world examples and standard-based methods to classify and ensure the stability of steel sections under various load conditions. Participants will gain practical insights into preventing local failures and achieving optimal structural performance.

Module Detail:
In this module, we delve into the intricacies of lateral torsional buckling in flexural members, focusing on the conditions and preventive measures necessary to avoid this type of failure in steel beams.

Lesson Summary:
In this lesson, we introduce the concept of lateral torsional buckling in steel beams. Bent beams that are not properly braced to prevent lateral movement may experience lateral torsional buckling if their resistance to torsion and moment of inertia about the axis of least inertia are insufficient. This lesson covers the importance of lateral bracing to avoid such buckling, detailing the concepts of unsupported lengths (Lb) and how they impact the beam's behavior. We discuss the criteria for compact sections, the significance of the lengths Lp and Lr, and how beams can fail inelastically or elastically depending on these parameters.

Module Detail: This module explores the critical concept of lateral torsional buckling in flexural members, with a particular focus on the Cb value. The lessons cover how to graph and interpret the nominal moment as a function of unsupported length, and the significance of compact sections in preventing buckling.

Lesson Summary: In this lesson, we continue our discussion on lateral torsional buckling in flexural members, specifically addressing the Cb value. We explain its importance and how it influences the nominal moment versus unsupported length (Lb) graph. The lesson details how to interpret this graph for different profiles, such as I-sections, and the significance of lengths Lp and Lr in determining whether a section will fail plastically, inelastically, or elastically. We also cover the necessary equations and physical characteristics needed to calculate these values and their implications for the stability and strength of steel beams.

Module Detail: This module continues the discussion on lateral torsional buckling in flexural members, focusing on the calculation and significance of the plastic moment (Mp) and the nominal bending resistance (Mn). It explores the relationships between unsupported lengths (Lb), critical lengths (Lp and Lr), and how these influence the buckling behavior and resistance of steel beams.

Lesson Summary: In this lesson, we delve into the calculation of the plastic moment and its role in determining the nominal bending resistance of steel beams. We discuss how the values of Lp and Lr define different segments of the moment capacity curve, and the importance of the Cb factor in adjusting these values. The lesson explains that the plastic moment is achieved when the unsupported length (Lb) is less than Lp. If Lb falls between Lp and Lr, the profile may fail inelastically, and if Lb exceeds Lr, the profile will fail elastically. We cover the necessary equations and physical characteristics, including the modulus of elasticity, yield stress, and section moduli, to graph the nominal moment as a function of unsupported length. The critical importance of ensuring that the nominal moment does not exceed the plastic moment, even when adjusted by the Cb factor, is emphasized to maintain the integrity and safety of the structural design.

Module Detail: This module delves into the modification factor Cb for lateral torsional buckling in flexural members, exploring how variations in the moment diagram influence the nominal moment capacity of steel beams. It covers the importance of the Cb factor and its application in different segments of the moment diagram, as well as the equations used to calculate it.

Lesson Summary: In this lesson, we focus on the Cb factor and its role in accounting for variations in the moment diagram of flexural members. We begin by explaining how the Cb factor adjusts the nominal moment equations, which are typically applicable for constant bending moments. Through examples, we illustrate how different segments of a beam's moment diagram—variable and constant moments—affect the Cb value. Specifically, we explore how the Cb factor increases the beam's capacity to withstand greater moments before lateral instability occurs. The lesson also covers the calculation of the Cb factor using the maximum moment values and their positions along the unbraced length (Lb). By understanding the application and calculation of the Cb factor, participants will learn how to accurately assess the nominal bending resistance of beams under varying moment conditions, ensuring the stability and safety of their designs.