Podcast
Questions and Answers
What are the three equilibrium equations used to determine the reactions RA, HA, and RB?
What are the three equilibrium equations used to determine the reactions RA, HA, and RB?
What does the bending moment in a beam counter?
What does the bending moment in a beam counter?
What is a requirement for finding the shear force and bending moment at a section of a beam?
What is a requirement for finding the shear force and bending moment at a section of a beam?
What type of beam has a bending moment of zero at the midspan when the overhang length is b/L = 0.5?
What type of beam has a bending moment of zero at the midspan when the overhang length is b/L = 0.5?
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Why is it crucial to clearly understand the sign conventions for internal forces?
Why is it crucial to clearly understand the sign conventions for internal forces?
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What is the purpose of analyzing internal forces in beam members?
What is the purpose of analyzing internal forces in beam members?
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What is the primary difference between a beam and a bar?
What is the primary difference between a beam and a bar?
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What type of support allows rotation but no translation?
What type of support allows rotation but no translation?
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What type of beam is supported at one end and free at the other?
What type of beam is supported at one end and free at the other?
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What type of load is applied over a small area?
What type of load is applied over a small area?
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What develops in a beam due to external loads?
What develops in a beam due to external loads?
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How many unknown reactive forces does a fixed support have?
How many unknown reactive forces does a fixed support have?
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What is the purpose of drawing a free-body diagram of the beam section?
What is the purpose of drawing a free-body diagram of the beam section?
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What type of beam loading varies linearly along the beam length?
What type of beam loading varies linearly along the beam length?
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What type of support restricts both translation and rotation?
What type of support restricts both translation and rotation?
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What type of beam is similar to a cantilever beam but has one end extending past the support?
What type of beam is similar to a cantilever beam but has one end extending past the support?
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Study Notes
Introduction to Beam Bending
- This module covers the topic of beam bending, building on the previous modules that examined the effects of axial forces and the resulting stresses and strains in bars
- The previous modules discussed the effects of torsional moments on bars, and this module will examine other aspects of loading systems acting on beams
- After this module, the concept of beams will be well-understood, including the definition of a beam and the various forces acting on it
- Different types of beam supports and beam configurations will also be covered
- The concepts of shear force and bending moment will be explained, and examples will be provided on evaluating the reactive forces for different beam loading conditions
Understanding Beams
- A beam is a structural member that is loaded transversely (perpendicular) to its longitudinal axis
- Beams are different from bars which were loaded axially (along the length) in previous modules
- While bars experienced axial forces, beams experience transverse loads and the resulting bending moments
- The vectorial direction of the loads and moments acting on beams is perpendicular to the beam's longitudinal axis
Beam Supports
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Beams can be supported in different ways, such as:
- Pinned or hinged support - allows rotation but no translation
- Roller support - allows translation in one direction but no rotation
- Fixed support - completely restricts translation and rotation
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The type of support affects the reactive forces developed at the supports
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Pinned and roller supports have 2-3 unknown reactive forces, which can be determined using the equations of static equilibrium
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Fixed supports have 3 unknown reactive forces that need to be evaluated
Cantilever and Overhanging Beams
- A cantilever beam is supported at one end and free at the other
- It develops 3 unknown reactive forces - a vertical force, a horizontal force, and a moment
- An overhanging beam is similar, with one end supported and the other end extending past the support
- The overhang can induce bending moments and rotation, which the roller support cannot resist
Types of Beam Loading
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Concentrated (or point) load - a load applied over a small area
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Distributed (or linear) load - a load that varies linearly along the beam length
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The beam may experience a combination of different loading types along its length### Overview of Beams and Supports
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Beams can experience various types of loading and support conditions, which result in different internal forces and moments
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Axial force, shear force, and bending moment are the key internal forces that develop in beams due to external loads
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Beams supported at both ends (simply supported) can experience different loading patterns like concentrated, linearly varying, or uniformly distributed loads
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Cantilever beams are fixed at one end and free at the other, and can experience concentrated or moment loads
Analyzing Internal Forces in Beams
- To analyze the internal forces, we first draw the free-body diagram of the beam section of interest
- The support reactions (e.g. RA, HA, RB) are determined using the equilibrium equations: ΣFx = 0, ΣFy = 0, and ΣM = 0
- The shear force (V) and bending moment (M) diagrams are then plotted along the length of the beam
- The shear force represents the transverse internal force, while the bending moment counters the external bending effects
Example Problems
- For a simply supported beam with an overhang, the bending moment at the midspan is zero when the overhang length is b/L = 0.5
- To find the shear force and bending moment at a section 2 m from the left support, we need to determine the support reactions first
- The support reactions can be calculated using the equilibrium equations, which then allows us to find the desired internal forces at the section of interest
Key Takeaways
- Beams can be supported in different ways (pinned, roller, fixed) which affects the internal force distributions
- The sign conventions for shear force, axial force, and bending moment need to be clearly understood
- Analyzing the internal forces is a crucial step before evaluating the stresses in beam members
Introduction to Beam Bending
- Beam bending builds on previous modules that examined axial forces and resulting stresses and strains in bars
- This module examines other aspects of loading systems acting on beams
Understanding Beams
- A beam is a structural member loaded transversely (perpendicular) to its longitudinal axis
- Beams experience transverse loads and resulting bending moments, unlike bars which experienced axial forces
- The vectorial direction of loads and moments acting on beams is perpendicular to the beam's longitudinal axis
Beam Supports
- Beams can be supported in different ways:
- Pinned or hinged support: allows rotation but no translation
- Roller support: allows translation in one direction but no rotation
- Fixed support: completely restricts translation and rotation
- The type of support affects the reactive forces developed at the supports
Cantilever and Overhanging Beams
- A cantilever beam is supported at one end and free at the other, developing 3 unknown reactive forces
- An overhanging beam is similar, with one end supported and the other end extending past the support, inducing bending moments and rotation
Types of Beam Loading
- Concentrated (or point) load: a load applied over a small area
- Distributed (or linear) load: a load that varies linearly along the beam length
Overview of Beams and Supports
- Beams experience various types of loading and support conditions, resulting in different internal forces and moments
- Axial force, shear force, and bending moment are the key internal forces that develop in beams due to external loads
Analyzing Internal Forces in Beams
- To analyze internal forces, draw the free-body diagram of the beam section of interest
- Determine support reactions (e.g. RA, HA, RB) using the equilibrium equations: ΣFx = 0, ΣFy = 0, and ΣM = 0
- Plot shear force (V) and bending moment (M) diagrams along the beam length
- Shear force represents the transverse internal force, while bending moment counters the external bending effects
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Description
Learn about beam bending, building on axial forces and torsional moments, and understand the definition of a beam and forces acting on it.