Engineering Flashcards
Scalar
Quantities which have size but no direction.
e.g. $40, 60 seconds, 3kg
force vector quantity (4 properties).
Magnitude: Strength or intensity of the force (measured in N or lbf).
Sense: Orientation in which the force is applied. (arrow)
Direction: The orientation in which the vector points. (acute angle of horizontal)
Point of Application: Specific location where the force is exerted on an object.
co-linear force
The line of action of all the forces acts along the same line.
Example: Tug of war
concurrent force
Multiple forces applied to a single point and intersect at the one point.
Co-planar force.
Forces acting in the same plane or on the same two-dimensional surface.
four type of beam supports.
Fixed
Roller
Pin
Simple Support
Describe what a fixed beam support does
Offers resistance against vertical and horizontal movement as well as rotation.
Describe what a Roller beam support does
Provides vertical support while allowing horizontal movement, but prevents rotation.
Describe what a Pin beam support does
Allows rotation but restrains horizontal and vertical movement.
Describe what a Cantilever beam support does
A cantilever beam fixed at one end and free at the other is a structural element that offers support against vertical loads and moments at its fixed end while allowing rotation and limited lateral movement at its free end.
Define equilibrium in relation to structures.
When all forces or moments acting upon it are balanced.
What is a moment?
Also known as torque, is a measure of the rotational force applied to an object about a specific point.
How do you calculate a moment?
= force x perpendicular distance from pivot (M = fd)
What are the types of bridges?
Beam, Arch, Suspension, Cable-Stayed, Truss
BASCT
Describe a truss structure
A truss is a rigid framework with internal members that are connected in a triangular pattern.
Identify the typical component parts of a truss bridge
- Top Chord and Bottom Chord
- Deck
- Vertical
- Diagonal
- End post
- Hip vertical
- Support (abutment)
Types of truss bridges
Warren /\/\/\
Pratt \ \ / /
Howe / / \ \
What is compression ?
A type of force or stress that tends to shorten or squeeze an object along its axis.
It occurs when external forces push or press against the object’s structure, causing its particles or components to move closer together.
Commonly experienced by columns and beams
What is tension?
A type of force or stress that tends to elongate or stretch an object along its axis.
It occurs when external forces pull or stretch the object’s structure, causing its particles or components to move farther apart.
Commonly experienced by cables and ropes
In a truss bridge, what type of force is experienced by the top chord
Compressive forces
Benefits of a Truss compared to other bridge types
Efficient use of materials: triangular shapes allow for optimal strength to weight ratio.
Span large distances: Suitable for long spans without the need for intermediate supports.
Versatility: Can be constructed using various materials, such as steel, wood, or concrete.
Ease of inspection and maintenance: Clear visibility of members simplifies inspection and repair processes
.
Aesthetic appeal: Offers architectural flexibility and can be designed with visually appealing feature
In a truss bridge, what type of force is experienced by the bottom chord
tensile forces
Vector
Show both direction and magnitude.
e.g force, acceleration, velocity and displacement
Can be represented graphically
written with bar above pronumeral
Newton’s first law of motion
an object in motion will remain in motion unless acted upon by another force
Newton’s Second Law
Force = mass x acceleration
Newton’s Third Law
For every action there is an equal and opposite reaction
In a cable stayed bridge where are compression and tensile forces located
Compressive = towers
Tensile = cables
In a beam bridge where are compression and tensile forces located
Compressive = Piers, top of beam
Tensile = bottom of beam
In an arch bridge where are compression and tensile forces located
Compressive = abutments
Tensile = None
Addition of vectors: Sign of Vectors
Must be given sign because they have direction
Given positive or negative depending on direction of vector
Resultant (sum of all forces) = closing force which goes in opposite general direction to the other forces
A beam may be subjected to:
Concentrated loads.
Distributed loads
or a combination of both
What is a simply support beam
Pinned at one end and roller support at the other
Overhanging beam
Rests on two similar supports to the simply supported arrangement but extends beyond one or both of its supports.
What are the characteristics of cantilever
Rigidly fixed at one end and free at the other.
A pinned supports reactions can be unknown. Therefore it is analyzed in terms of its:
horizontal and vertical components
The total reaction of at the fixed end of a cantilever bean may contain.
Horizontal reaction force
Vertical Reaction Force
Reaction moment
(3 unknowns at fixed end)
Conditions of equilibrium
∑FH = 0
∑FV = 0
∑M = 0
Pins
Pins are typically small, cylindrical rods or bars made of steel or other strong materials. They are used in structural connections to transfer loads, provide support, or allow for movement between connected members.
Abutments
Foundations that support weight of bridge and hold back soil - typically made of concrete
Piers
Additional supports in the middle of bridges
Describe how you could find a zero Force Members
If a joint only has two non-colinear members and there is no external load or support reaction at that joint, then those forces are zero force members.
If three members form a truss joint for which two of the members are colinear and there is no external load or reaction at that joint, then the third non-colinear member is a zero-force member.
Determinacy of Coplanar Trusses
b + r = 2j (Determinate)
b + r > 2j (Indeterminate)
b = num of bar members
r = number of reactions
J = number of joints
What is magnitude in relation to force vector quantity
Strength or intensity of the force (measured in N or lbf).
What is sense in relation to force vector quantity
Orientation in which the force is applied. (Shown by an arrow)
What is direction in relation to force vector quantity
The orientation in which the vector points. (acute angle of horizontal)
What is Point of application in relation to force vector quantity
Specific location where the force is exerted on an object.
Gusset plate
Gusset plates, typically triangular or rectangular steel plates, reinforce and connect structural elements at joints where beams, columns, or trusses intersect, providing added support and stiffness through bolting or welding.
What is a simple support used for?
Simple supports aren’t widely used in real-life structures unless the engineer can be sure that the member will not translate; otherwise, they run the risk of the member simply falling off the support.
