Name: eccentric load stresses in structural columns
Uploaded: 2024-05-23T13:00:08.000Z
Duration: 1 min 21 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Physics

PHYS.2

PHYS.2.D

design-of-columns-under-an-eccentric-load

Design of Columns under an Eccentric Load

Pour un poteau chargé avec une charge axiale excentrique dans le plan de symétrie, les contraintes normales dues à la charge excentrique peuvent être écrites comme des contraintes dues à une charge centrée équivalente et à la flexion.
Lors de la conception de poteaux avec des charges excentriques, la contrainte maximale développée dans le poteau ne doit pas dépasser la contrainte maximale admissible. Cette condition peut être satisfaite en utilisant deux approches distinctes.
La méthode des contraintes admissibles suppose que la contrainte admissible pour le poteau chargé de manière excentrique est la même que la contrainte maximale pour le poteau chargé centralement. La contrainte admissible pour le poteau peut être exprimée en fonction du rapport d’élancement.
La contrainte admissible pour la charge centrée est plus petite que celle due au moment de flexion. Il en résulte que la méthode de contrainte admissible est trop conservatrice. 
D’autre part, la méthode d’interaction prend en compte la contrainte admissible due à la charge centrée et à la flexion.
Il fournit une équation pour la contrainte maximale sous charge centrale lorsqu'il n'y a pas de moment de couple. De même, il définit la contrainte maximale due à la flexion pure lorsqu'il n'y a pas de charge.

conception de colonnes soumises à une charge excentrique

Concevoir des colonnes pour résister aux charges excentriques est un aspect essentiel de l'ingénierie structurelle, garantissant que les structures peuvent supporter des charges excentriques sans défaillance. Ce processus de conception doit tenir compte des contraintes normales supplémentaires introduites par le chargement excentrique, qui peuvent influencer de manière significative la répartition des contraintes et la stabilité globale d'une colonne. Une charge excentrique appliquée à une colonne, induit des contraintes normales qui peuvent être conceptualisées comme une combinaison de contraintes dues à une charge centrée équivalente et à des contraintes de flexion supplémentaires. Cela conduit à une répartition non- uniforme des contraintes qui doit être soigneusement analysée pour éviter une défaillance structurelle. Deux méthodes principales sont utilisées dans la conception des colonnes soumises à des charges excentriques : la méthode des contraintes admissibles et la méthode des interactions.

La méthode de contrainte admissible est une approche simple dans laquelle la contrainte admissible pour une colonne chargée de manière excentrique est égale à la contrainte maximale admissible pour une colonne chargée de manière centrique. Cette méthode simplifie le processus de conception en traitant la contrainte admissible en fonction du rapport de rigidité de la colonne, qui est une mesure de sa propension à se déformer sous charge. Cependant, cette méthode suppose que la contrainte admissible pour un chargement centré englobe les contraintes supplémentaires dues à la flexion, ce qui conduit à des conceptions conservatrices qui peuvent ne pas utiliser tout le potentiel du matériau. La prudence inhérente à cette approche garantit la sécurité, mais peut aboutir à des colonnes plus grandes et plus coûteuses que nécessaire.

La méthode d'interaction offre une approche plus subtile en considérant à la fois les contraintes admissibles dues au chargement centré et les contraintes résultant des moments de flexion. Cette méthode fournit un cadre pour calculer la contrainte maximale que la colonne peut supporter sans moment de couple (chargement centré pur) et la contrainte maximale due à la flexion pure (sans charge axiale). En tenant compte simultanément de ces conditions, la méthode d'interaction permet une estimation plus précise et moins conservatrice des contraintes admissibles dans les colonnes chargées de manière excentrique.

En pratique, la méthode d’interaction est souvent privilégiée pour sa capacité à concilier sécurité et efficacité matérielle. Cela nécessite une analyse détaillée de la répartition des contraintes au sein de la colonne, en tenant compte à la fois des charges axiales et des moments de flexion.

Conception de colonnes soumises à une charge excentrique

Pour une colonne chargée avec une charge axiale excentrique dans le plan de symétrie, les contraintes normales dues à une charge excentrique peuvent être écrites comme des contraintes dues à une ...

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Mechanical Engineering

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KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

eccentric load stresses in structural columns

Structural columns under eccentric load must be designed for both axial force and bending stress. An eccentric load is an off-center load, and it creates a non-uniform stress pattern across the column. Engineers must analyze this stress distribution carefully to reduce the risk of failure.

The stress in an eccentrically loaded column can be treated as the sum of two parts. One part comes from an equivalent centric load, which is a load applied through the center of the column. The other part comes from bending stresses caused by the load being off-center.

Two common design approaches are used for these columns. The allowable stress method sets the allowable stress for an eccentrically loaded column equal to the maximum stress allowed for a centrally loaded column. This method uses the column slenderness ratio, which describes how likely a column is to buckle.

The allowable stress method is simple, but it is also conservative. It assumes the centric-load allowable stress already covers the extra bending stress from eccentric loading. As a result, the column may be larger and more expensive than needed, even though the design is safe.

The interaction method gives a more detailed design check. It considers both the allowable stress from centric loading and the stress from bending moment at the same time. It compares the case of pure centric loading, with no couple moment, and the case of pure bending, with no axial load.

Because it includes both effects, the interaction method can estimate allowable stress more accurately. It is often preferred when engineers want a better balance between safety and material use. The method requires careful stress analysis of the column under both axial load and bending moment.

Eccentric Load Stresses in Structural Columns

eccentric-load-stresses-in-structural-columns

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design of columns under an eccentric load

Structural columns under eccentric load must be designed for both axial force and bending stress. An eccentric load is an off-center load, and it creates a non-uniform stress pattern across the column. Engineers must analyze this stress distribution carefully to reduce the risk of failure. The stress in an eccentrically loaded column can be treated as the sum of two parts. One part comes from an equivalent centric load, which is a load applied through the center of the column. The other part...

key terms and concepts

Learn how eccentric loads create combined axial and bending stresses in columns, and compare the allowable stress and interaction methods used in design.

Eccentric Load Stresses in Structural Columns | JoVE K12

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Eccentric Load Stresses in Structural Columns

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