Name: beam deflection and boundary conditions
Uploaded: 2024-05-23T13:00:02.000Z
Duration: 1 min 23 s
Channel: JoVE

La curvatura de la curva plana en un punto de la curva se puede expresar usando una expresión que involucre la primera y la segunda derivadas de la curva.
La pendiente es insignificante para la curva elástica de la viga, por lo que la ecuación rectora para la curva elástica se expresa como una ecuación diferencial lineal de segundo orden, considerando la rigidez a la flexión.
Si la rigidez a la flexión varía a lo largo de la viga, se expresa en función de x. Sin embargo, para una viga prismática, la rigidez a la flexión permanece constante.
La integración de esta ecuación proporciona el ángulo formado por la tangente a la curva elástica en un punto con la horizontal.
Este pequeño ángulo, al integrarse, nos da la deflexión del haz en cualquier punto. Las condiciones de contorno de los apoyos de la viga determinan las constantes de las ecuaciones.
Las vigas apoyadas, en voladizo y en voladizo son los tres tipos de vigas que se consideran principalmente. En el caso de las vigas apoyadas y en voladizo, la deflexión en los puntos de apoyo es cero.
Tanto la deflexión como la pendiente en el punto de apoyo son cero para las vigas en voladizo. Estas condiciones permiten el cálculo de las constantes.

ecuación de la curva elástica

Equation of the Elastic Curve

<div>
 El concepto de curvatura en curvas planas, crucial en ingeniería estructural, define con qué intensidad se dobla una viga bajo carga. Esta curvatura se determina utilizando la primera y segunda derivada de la curva.
 
 Considere una viga en voladizo con una carga puntual en su extremo libre (por ejemplo, un trampolín). Al analizar la deflexión de una viga con pendientes pequeñas, la forma de la curva elástica de la viga se vuelve clave. La ecuación que rige este análisis involucra el momento flector y la rigidez a la flexión de la viga, que es un producto del módulo de elasticidad y el momento de inercia de la sección transversal de la viga.
 
 <img alt="Equation 1" src="/files/ftp_upload/15667/15667_Equation_1.svg" style="text-align: center; height: 32px;">
 Para vigas prismáticas, donde la sección transversal permanece constante, el análisis se simplifica, haciendo que la rigidez a la flexión sea constante a lo largo de la longitud de la viga. La integración de la ecuación gobernante permite calcular el ángulo formado por la tangente a la curva en cualquier punto, lo que, tras una mayor integración, produce la deflexión de la viga en ese punto.
 
 <img alt="Equation 2" src="/files/ftp_upload/15667/15667_Equation_2.svg" style="text-align: center; height: 28px;">
 Las condiciones de contorno en los soportes de las vigas son vitales para completar estos cálculos. Las vigas apoyadas, voladas y en voladizo son tipos comunes de vigas, cada una con condiciones de contorno distintas. Por ejemplo, la deflexión y la pendiente en el punto de apoyo de una viga en voladizo son cero, lo cual es esencial para calcular las constantes de las ecuaciones de deflexión.
 
 Predecir con precisión la deflexión de la viga es crucial para garantizar la seguridad y funcionalidad estructural. La deflexión excesiva puede causar fallas estructurales o problemas de servicio, lo que subraya la importancia de comprender el comportamiento de la viga bajo carga.
 
</div>

Ecuación de la curva elástica

La curvatura de la curva plana en un punto de la curva se puede expresar usando una expresión que involucre la primera y la segunda derivadas de la curva.
El...

Education

Educación

JoVE Core

Mechanical Engineering

Ingeniería Mecánica

Unit 1

Unidad 1

Deflection of Beams

Deflexión de vigas

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

beam deflection and boundary conditions

Beam deflection and boundary conditions help describe how a beam bends under load. In structural engineering, the curvature of a plane curve shows how sharply the beam bends. That curvature is found from the curve’s first and second derivatives.

A cantilever beam with a point load at its free end is a common example. A diving board works like this type of beam. When slopes are small, the beam’s elastic curve becomes the main shape used in the analysis.

The governing equation connects bending moment with flexural rigidity. Flexural rigidity is the product of the modulus of elasticity and the moment of inertia of the beam’s cross-section. For a prismatic beam, the cross-section stays constant, so the flexural rigidity is constant along the beam.

Integrating the governing equation gives the angle of the tangent to the curve at any point. A second integration gives the deflection at that point. Boundary conditions at the beam supports are needed to find the constants in these equations.

Supported, overhanging, and cantilever beams each have different boundary conditions. For a cantilever beam, the deflection and slope at the support point are zero. Predicting deflection is important because too much bending can lead to structural failure or serviceability problems.

Beam Deflection and Boundary Conditions

deformation of a beam under transverse loading

deformation-of-a-beam-under-transverse-loading

Beam Deflection from Loads and Supports

Beam deflection depends on the loads on a beam and the support conditions at its ends. For indeterminate beams, especially those with overhanging parts and multiple concentrated loads, careful analysis is needed to predict how the beam will bend. The first step is to draw an accurate free-body diagram. A free-body diagram shows the forces and moments acting on the beam. It helps reveal how the bending moment changes along the beam length. The bending moment diagram also shows how the beam...

equation of the elastic curve

Beam deflection and boundary conditions help describe how a beam bends under load. In structural engineering, the curvature of a plane curve shows how sharply the beam bends. That curvature is found from the curve’s first and second derivatives. A cantilever beam with a point load at its free end is a common example. A diving board works like this type of beam. When slopes are small, the beam’s elastic curve becomes the main shape used in the analysis. The governing equation connects bending...

elastic curve from the load distribution

Beam Deflection Under Distributed Load

Beam deflection under distributed load is a key part of beam analysis in engineering. It helps predict how a beam bends and reacts when a load is spread along its length. Engineers use this relationship to judge whether a structure will stay safe and functional. The analysis starts with the link between load, shear force, and bending moment. These quantities can be written in differential form. When beam flexibility is treated as constant, further differentiation leads to a higher-order...

deflection of a beam

Beam Slope and Deflection by Singularity

Beam slope and deflection can be found with singularity functions when beam loading is hard to write as one simple equation. This method is useful in structural engineering because it helps describe beams under several loads without breaking the problem into many separate cases. Singularity functions are mathematical tools for showing discontinuities in a load, shear force, or bending moment equation. They are especially helpful when a load acts at a single point or over a set interval. In the...

method of superposition

Beam Deflection Under Combined Loads

Beam deflection under combined loads can be found with the method of superposition. This structural engineering method is used to analyze how multiple loads affect a beam. It works by finding the slope and deflection from each load separately, then adding those results together. The method applies only when the beam stays within its elastic limit. In that range, the material deforms in a linearly elastic way. That makes it valid to combine the effects of separate loads without changing the...

moment-area theorems

Beam Deflection Using Moment-Area Rules

The moment-area theorems help describe beam bending in structural engineering. They are often used for building floor supports and other beams under load. The theorems use the elastic curve, which is the shape a beam takes as it deforms. The first theorem links slope change to area on an M/EI diagram. Here, M is the bending moment, E is the modulus of elasticity, and I is the moment of inertia. When M/EI is plotted along the beam length, the area under the curve gives the total rotation...

beams with symmetric loadings

Moment-Area Method for Cantilever Deflection

The moment-area method is used in structural engineering to find the slope and deflection of a beam under load. It is especially useful for a cantilever beam with a concentrated load and a moment at the free end. The analysis begins with a free-body diagram. This diagram helps calculate the reactions at the fixed end. After that, the bending moment diagram is drawn to show how the bending moment changes along the beam. Points where the bending moment is zero are important in this step. Next,...

beams with unsymmetric loadings

Beam Deflection and Level Points

Beam deflection and level points can be found for a supported beam under unsymmetrical loadings using moment-area theorems. This type of analysis helps show how a beam bends when forces are spread unevenly along it. It is an important part of structural engineering because it links load patterns to beam response. The first moment-area theorem is used to find the slope at any point on the beam. It states that the change in slope between two points equals the area under the moment diagram over...

maximum deflection

Locating the Beam’s Highest Deflection

Maximum deflection in a supported beam depends on where the load is placed. With an unsymmetrical load, such as a train moving across a bridge, the beam may bend most at a point that is not the midpoint. Finding that point is important for judging stress and deflection in the structure. The point of maximum deflection is called point O. At point O, the tangent to the deflection curve is horizontal. That means the slope is zero there. To locate point O, the slope at any point X along the beam...

key terms and concepts

Learn how beam deflection, curvature, and boundary conditions work together in structural engineering, using cantilever and other beam types.

Beam Deflection and Boundary Conditions | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Beam Deflection and Boundary Conditions

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