1.1. Structural Concepts

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Questions and Answers

What is kinematics primarily concerned with?

The effect of mass on motion

The acceleration of an object

The geometry of motion (correct)

The forces acting on a body

Which unit is commonly used to measure force in the US?

Pounds (correct)

Newtons

Kilograms

Watts

Which type of force system has lines of action that intersect at a common point?

Concurrent force system (correct)

Parallel force system

Coplanar force system

Non-coplanar force system

What is the primary difference between kinematics and kinetics?

Kinematics describes motion without considering forces while kinetics analyzes the effect of forces. Signup and view all the answers

Which statement regarding the principle of transmissibility is correct?

The external effect is consistent regardless of where the force is applied along its line of action. Signup and view all the answers

A rigid body is best described as:

A matter with fixed parts relative to each other. Signup and view all the answers

Which of the following accurately defines a coplanar force system?

Forces whose lines of action lie in the same plane. Signup and view all the answers

Which type of mechanics deals specifically with the effect of forces on mass and acceleration?

Dynamics Signup and view all the answers

What is the definition of static equilibrium?

A body acted upon by a balanced force system. Signup and view all the answers

Which characteristic is NOT important when discussing a force?

Color Signup and view all the answers

Which of the following best defines a resultant force?

A single force that produces the same effect as multiple forces. Signup and view all the answers

In a free body diagram, what does the sketch primarily illustrate?

The forces exerted by one body on another. Signup and view all the answers

Which type of load is specifically associated with twisting actions?

Torque Signup and view all the answers

What does axial force represent?

A pulling or pushing action over a cross-section. Signup and view all the answers

What are bending moments primarily associated with?

Resistance to bending of a member. Signup and view all the answers

Which of the following is NOT considered an external load?

Internal Stress Signup and view all the answers

What is shear force primarily concerned with?

Components resisting sliding between sections. Signup and view all the answers

What best describes the action and reaction forces according to Newton's third law?

They act on different bodies and are equal and opposite. Signup and view all the answers

What is the formula for calculating stress?

S = P / A Signup and view all the answers

What occurs at the yield point in the stress-strain curve?

Material experiences significant elongation without increased load Signup and view all the answers

Which of the following statements is true regarding the ultimate strength?

It represents the highest point on the stress-strain curve Signup and view all the answers

What is allowable stress commonly based on?

Yield point or ultimate strength divided by a factor of safety Signup and view all the answers

What is the purpose of studying the strength of materials?

To increase safety and efficiency in selecting and proportioning materials Signup and view all the answers

What does the elastic limit indicate?

The point at which material starts to yield with no return to original shape Signup and view all the answers

What is the correct definition of rupture strength?

Stress at failure, typically lower than ultimate strength Signup and view all the answers

How is axial deformation characterized?

Load acting parallel to the member axis, causing elongation or shortening Signup and view all the answers

What is a common method to determine yield strength in materials lacking a well-defined yield point?

Offset method Signup and view all the answers

What does the stress-strain diagram represent?

The relationship between stress and strain showing various limits and points Signup and view all the answers

What do dead loads include in the context of structural loadings?

The weight of the structure and immovable loads Signup and view all the answers

Which of the following is an example of a movable load?

Snow on a roof Signup and view all the answers

What factor is NOT considered when evaluating allowable stress of columns?

Shape of the column cross-section Signup and view all the answers

How does the application of live loads affect structural deformation?

Gradual application leads to the same deformation as static load Signup and view all the answers

Which type of live load has a fixed magnitude and variable location?

Movable load Signup and view all the answers

What is the minimum design dead load for 'Ceramic or quarry tile (20 mm) on 25 mm mortar bed' according to the provided guidelines?

1.10 kPa Signup and view all the answers

Under which condition does the increase in stress due to live load become significant?

When applied rapidly Signup and view all the answers

What is the main cause of flexural failure in beams?

Exceeding the flexural capacity of the beam Signup and view all the answers

What characterizes buckling in structural members?

A sudden change in shape under axial load Signup and view all the answers

Which statement best defines bending in a structural member?

Occurs when a transverse load acts perpendicular to the neutral axis Signup and view all the answers

How does the modulus of elasticity affect material deformation?

Low modulus materials are less resistant to elastic deformation Signup and view all the answers

What is the relationship described by Hooke's Law?

The relationship between stress and strain in a material Signup and view all the answers

Which type of failure occurs due to insufficient shear resistance?

Shear failure Signup and view all the answers

What causes bending stress in a structural member?

Transverse load acting perpendicularly Signup and view all the answers

Which diagram illustrates different types of beam failures?

Types of beam failures diagram Signup and view all the answers

Which phenomenon occurs gradually due to increasing axial load?

Buckling Signup and view all the answers

Which type of stress is illustrated in the diagrams of the document?

Shear stress and normal stress Signup and view all the answers

Study Notes

Structural Concepts

Rigid body: A body whose parts are fixed relative to each other, simplifying analysis.
Force: Causes a change in the body's state of motion; characterized by magnitude, line of action, and direction.
Force system: Arrangement of forces acting on a body, classified as coplanar or non-coplanar.
Types of force systems: Concurrent (lines of action intersect), parallel (lines of action are parallel).
Principle of transmissibility: External effect of a force is constant regardless of application point along its line of action, but internal effects are dependent on the point of application.

Principles of Static Equilibrium

Static Equilibrium: A body with balanced forces is at rest.
Free body diagram: A sketch displaying forces exerted on a body, helping analyze equilibrium.
Strength of materials: Studies the relationship between external loads and their internal effects on bodies.
Types of external loads: Axial, twisting (torque), bending loads, and combinations.

Stress-Strain Relationships

Stress: Force per unit area (S = P/A).
Strain: Unit deformation.
Proportional limit: The point where stress is directly proportional to strain (Hooke's Law).
Elastic limit: Stress beyond which the material doesn't return to its original shape when unloaded.
Yield point: Significant elongation without increased load, used for steel design.
Yield Strength: For materials lacking a defined yield point, it's determined by the offset method.
Ultimate stress/strength: Highest stress value the material can withstand.
Rupture strength: Stress at failure (lower than ultimate in structural steel).
Allowable stress: Limited to values below the proportional limit, often based on yield or ultimate strength divided by a factor of safety.

Types of Failure in Beams

Flexural failure: Occurs when the load exceeds the beam's flexural capacity.
Shear failure: Results from insufficient shear resistance between beam materials.

Bending and Buckling

Bending: Caused by a transverse load perpendicular to the neutral axis, creating bending stress.
Buckling: A sudden change in shape under axial load, occurring due to increasing axial load.

Hooke's Law - Axial Deformation and Modulus of Elasticity

Modulus of elasticity: Measures a material's resistance to elastic deformation.
Hooke's law: Describes the relationship between stress and strain in a material.

Structural Loadings

Prevailing Design Load: Considers axial load, material overstressing, and buckling.
Dead loads: Weight of the structure and permanently attached items.
Minimum Design Dead Loads: Includes values for ceilings, acoustical boards, gypsum boards, coverings, insulation, floor finishes (e.g., cement, tile, terrazzo, wood).
Movable loads: Loads that can be moved, often applied gradually (e.g., storage contents).
Live loads: Loads varying in position, classified as movable and moving loads.
Impact: Increase in stress due to rapid application of a load.
Snow and ice loads: Considered movable, as they don't always cover the entire roof.
Minimum Uniform Live Loads: Vary for different building types (e.g., hospitals, offices, schools).
Minimum Roof Live Loads: Depend on roof slope.

Lateral Loads

Wind loads: Important for large structures with open interiors.
Soil pressure: Active pressure is about half of vertical pressure, while passive pressure is about four times the vertical pressure.
Hydrostatic pressure: Loads on dams, tanks, calculated using hydraulic principles.
Earthquake forces: Structures must be designed to withstand earthquake effects, especially horizontal accelerations.
Centrifugal forces: Act on curved bridges, treated as moving loads.
Longitudinal forces: Horizontal forces acting along the roadway (e.g., forces on a bridge).

Structural Forms

Steel-cable structure: Efficient for carrying loads through tension.
Flexible membrane: Carries loads by tension, similar to many cables side-by-side.
Arch: Inverted cable structure, conforming to the equilibrium polygon based on the load.
Shell: Membrane with flexural stiffness and strength (like an arched cable), often made of reinforced concrete.
Planar truss or planar framework: Supports concentrated load with a two-member arch.
Space framework: Supports three-dimensional structures, using a tetrahedral nucleus.
Framed structure: Beams can be cantilevered or end-supported, commonly used in modern construction.

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Module 1 - Structural Concepts (Atlas)