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2024-12-02

掌握结构失效模式: 识别和分析指南

在本文中,我们将探讨失稳的各种类型,主要特征、原因以及它们在不同结构体系中的表现。

结构的破坏模式(例如屈曲、弯扭屈曲、局部屈曲、剪切屈曲和壳体结构稳定性)的原因、行为及其影响的结构构件各不相同。 Thorough understanding and identification of these stability issues are crucial for conducting accurate analyses and designing robust structures. This article will assist you in that endeavor by offering a detailed explanation of each failure type, including its characteristics, main causes, and key features. Finally, a comparison table will be included to summarize the differences between the failure types, making it easier for you to identify and distinguish them.

As you go through this article, keep in mind that all these failure modes can be analyzed using Dlubal’s Structural Stability add-on. By utilizing this tool, you gain a unique opportunity to address the challenges associated with these failure types through advanced Finite Element Analysis (FEA). Each failure mode discussed here will be accompanied by an example, allowing a deeper dive into the topic. Additionally, Dlubal provides a wide range of valuable resources, including Knowledge Base articles, FAQs, webinars, and more, all available in the relevant section of Dlubal’s website to further enhance your understanding of the subject.

弯曲屈曲

Flexural buckling is a form of global instability that occurs in a structural member subjected to axial compression, causing the member to bend or "buckle" laterally due to the compressive force. This phenomenon happens when the critical load, beyond which the member loses its stability under compression, is exceeded. Buckling is most common in slender columns or members with a high length-to-radius of gyration ratio. This behavior is typically governed by Euler's buckling formula for elastic materials, but it can involve either elastic or inelastic buckling, depending on the material properties and geometry of the member.

侧向屈曲

Lateral-Torsional Buckling is an instability that occurs in beams subjected to bending, resulting in both lateral displacement and twisting. The primary cause of this phenomenon is compression in the top flange, coupled with inadequate lateral support. It is observed most often in flexural members such as beams and girders, where moment-induced stress plays a significant role. The occurrence of lateral-torsional buckling is influenced by factors such as unbraced length, cross-sectional shape, and moment gradient. It is typically analyzed using the elastic critical moment for lateral-torsional buckling.

局部屈曲

Local buckling is related to the failure of individual plate elements (e.g., flanges, webs) within a cross-section, without causing global instability of the entire member. The primary cause of local buckling is localized compressive stress that exceeds the critical buckling stress of the plate element. This type of buckling is prevalent in thin-walled sections like I-beams, box girders, and cold-formed steel members. It is important to consider because it affects the strength and stiffness of the members, leading to a potential reduction in load-carrying capacity.

剪切屈曲

Shear buckling refers to a type of structural instability that occurs in a member subjected to shear forces, causing the material to deform or "buckle" laterally. Shear buckling happens when the applied shear force exceeds the critical threshold, causing the structure to deform laterally or out of plane. This is particularly likely to occur when the member is thin and lacks adequate lateral support to resist the shear force. Hence, shear buckling is often observed in elements like plates, webs of I-beams, or other slender structures under shear stresses. The critical parameter governing shear buckling is the shear buckling stress, which is influenced by factors such as the element’s thickness, aspect ratio, boundary conditions, and material properties.

Shell Buckling

Shell buckling is the loss of stability in thin, curved structures (shells), such as cylindrical, spherical, or conical shapes (for example, tanks, silos, pipelines), when exposed to compressive or lateral loads. It occurs when these loads cause the shell to deform, reducing its ability to carry further load, which can lead to significant distortions or even collapse. The primary cause of shell buckling is a non-uniform distribution of stresses, typically resulting from axial forces, shear stresses, or external pressure.

Comparison Table

Now that each failure type has been defined and its characteristics outlined, the key differences between them are summarized in Table 1. This table provides a concise overview of each mode, highlighting the main structural element affected, the primary load conditions that lead to failure, the resulting deformation, and the critical factor that governs the mode.

Table 1
Failure Type Main Structural Element Primary Load Deformation Mode Critical Factor
弯曲屈曲 Columns/Members 轴压 Lateral deflection 长细比
侧向屈曲 弯矩 Lateral displacement + twisting Unbraced length
剪切屈曲 剪力 Diagonal buckling/wrinkling 板厚度
局部屈曲 Plate elements (e.g., flanges) Local compressive stresses Out-of-plane deformation 板的长细比
Shell Stability Curved/shell structures Axial, pressure, or shear Complex buckling patterns Imperfections, curvature

Final Words

In structural design, several common stability issues can emerge, especially when they are not properly considered in the design process. This article provides an overview of five such issues: buckling, lateral-torsional buckling, local buckling, shear buckling, and shell stability. The information provided aims to help you understand their underlying causes, behaviors, and the structural elements they affect. This knowledge will enable you to identify and distinguish these stability concerns, giving you a solid foundation for integrating them into your analyses and designing resilient and safe structures.


作者

Kirove 女士的职责是撰写技术文章并为 Dlubal 软件的客户提供技术支持。



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