Embedded Files
The technology of creating container, shelters, supports, connectors, and functional shade.
Structural Engineering
Structural Technology – The technology of putting together parts and materials to create supports, containers, shelters, connectors and functional shapes.
(Water tower, buildings, roadways, table and chairs)
Elements of Structures
Elements of Structures
Column/Post - The purpose of Roman columns in structural engineering is to provide a vertical structural element that transmits, through compression, the weight of the structure above to other structural elements below. Roman columns were therefore often used to support beams or arches on which the upper parts of buildings, walls or ceilings rest. Roman Columns enabled the ancient Romans to build vast edifices with the humblest materials, to build bridges, aqueducts, sewers, amphitheaters, and triumphal arches, as well as temples and palaces. . It was applied extensively to doorways and windows and is an ornament as well as a utility. - Richard Collins
Bearing Wall - wall that bears the weight of the house above said wall, or above floor joist, resting upon it by conducting its weight to a foundation structure. The materials most often used to construct load-bearing walls in large buildings are concrete, block, or brick.
Frame - A structure that surrounds/encloses something. It is also used as a base for other structures, such as buildings, bridges, and basically anything else.
Beam - A beam is a horizontal structural element that is capable of withstanding load primarily by resisting against bending. The bending force induced into the material of the beam as a result of the external loads, own weight, span and external reactions to these loads is called a bending moment. Beams are characterized by their profile, their length, and their material. Beams are traditionally descriptions of building or civil engineering structural elements, but smaller structures such as truck or automobile frames, machine frames, and other mechanical or structural systems contain beam structures that are designed and analyzed in a similar fashion.
Cantilever - A cantilever is a rigid structural element, such as a beam or a plate, anchored at only one end to a (usually vertical) support from which it is protruding. Can be used in construction to create bridges or balconies. In cantilever bridges the cantilevers are usually built as pairs, with each cantilever used to support one end of a central section. Less obvious examples of cantilevers are free-standing (vertical) radio towers without guy-wires, and chimneys, which resist being blown over by the wind through cantilever action at their base.
Tie - A structural member that is designed to resist tension. Ties tend to be thinner than struts or beams.
Strut - A structural member that is designed to resist compression. Struts need to be designed to resist bucking so they tend to have a wider cross-section.
Arch - A curved symmetrical structure spanning an opening and typically supporting the weight of a bridge, roof, or wall above it.
Dome - A rounded vault forming the roof of a building or structure, typically with a circular base. A dome is a feature in structural geology consisting of symmetrical anticlines that intersect each other at their respective apices. Intact, domes are distinct, rounded, spherical-to-ellipsoidal-shaped protrusions on the Earth's surface. However, a transect parallel to Earth's surface of a dome features concentric rings of strata. Consequently, if the top of a dome has been eroded flat, the resulting structure in plan view appears as a bullseye, with the youngest rock layers at the outside, and each ring growing progressively older moving inwards. These strata would have been horizontal at the time of deposition, then later deformed by the uplift associated with dome formation.
Truss - Framework, typically consisting of rafters, posts, and struts, supporting a roof, bridge, or other structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object". A "two-force member" is a structural component where force is applied to only two points
Space Frame - A three-dimensional structural framework that is designed to behave as an integral unit and to withstand loads applied at any point.
Shell - A structure that provides protection and support. Usually a thin material on the outside surface. Something resembling or likened to a shell because of its shape or its function as an outer case
Tensile/Fabric - Is typically seen as a canopy or a sail shade shape. It stands by using tension not compression or bending.
Inflatable Structures- A structure that uses air pressure to help it maintain its desired size and shape.
Types of Structures
Tunnel - An artificial underground passage, especially one built through a hill or under a building, road, or river.
Support - A thing that bears the weight of something or keeps it upright.
Shelter - A place giving temporary shelter from danger or weather. Although shelter can be seen as any protective building there are also specific shelters like homeless or animal shelters.
Container - An object that can be used to hold something so it can be stored or transported.
Connector - A thing that links two or more things together. Component that connects structural systems or structural elements together in reference to buildings and structures.
Bridge - a structure carrying a road, path, railroad, or canal across a river, ravine, road, railroad, or other obstacle.
Building - A structure with a roof and walls such as a house, store, factory, or school. They are used as a place for people to live, work, or store items.
Tower - a tall narrow building, either freestanding or forming part of a building such as a church or castle.
Types of Loads (external forces acting on a structure)
Dead Load - The permanent or stationary load of a structure. The weight of the structural members, partition walls, fixed permanent equipment and anything else fastened to the structure. Anything put in or on something for convenience or transportation - the intrinsic weight of a structure or vehicle, excluding the weight of passengers or goods. A dead load is the weight of a structure/vehicle without the weight of passengers or cargo.
Live Load - A live load is the weight of people or goods in addtion to the weight of the structure/vehicle they are in.
Moving Load - The moving load can be defined by any combination of forces (the definition of loads originating from vehicles can contain concentrated loads, linear loads, and planar loads). A moving load case lets you analyze a structure subjected to a load caused by a set of forces, moving along a defined route.
Dynamic Load - A “dynamic load exerts varying amounts of force upon the structure that is upholding it”. A person walking is a dynamic load because the force (person) is moving. A load on a structural system that is not constant, such as a moving live load or wind load.
Point Load - A load applied to a specific point on a structural member. An example would be a hammer striking a nail
Continuous Load - A load that is applied evenly across a structure. Snow piling up on a room would be an example of a continuous load.
Reaction Force - Reaction force is force acting in the opposite direction of an applied force.
Types of Stresses (internal forces acting on the materials of a structure)
Tension - A pulling force coming from each end of a string, cable, chain, or similar one-dimensional continuous object
(n) the state of being stretched tight. (v) apply a force to (something) that tends to stretch it.
Compression - Compression is basically applying pressure/force to a material to make it reduce size, and example would be taking a foam cube, and pushing on all sides so that way it can get smaller. Another example would be a spring, you apply force to both ends to make the spring “shrink”. This shrinking could be temporary or it could cause a failure of the member. This failure could cause crushing, bulging or breaking (depending on the properties of the material). In longer compression members there is great risk of failure due to buckling. To prevent buckling you can make the member thicker, shorter, or just provide extra supports to prevent the middle from being able to move out of the line.
Bending - Bending stress is a more specific type of normal stress. When a beam experiences load like that shown in figure one the top fibers of the beam undergo a normal compressive stress. The stress at the horizontal plane of the neutral is zero. The bottom fibers of the beam undergo a normal tensile stress
Torsion - The action of twisting or the state of being twisted, especially of one end of an object relative to the other.
Shear - A shear stress, denoted τ is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section. A strain in the structure of a substance produced by pressure, when its layers are laterally shifted in relation to each other.
STRUCTURAL ANALYSIS
Statics: the study of the physics that describe how structures react to loads applied to them
The fundamental premise of statics is that structures do not move. When loads are applied to them, they react such that they (mostly) maintain their size and shape.
Because the structure is not moving we can conclude that the net acceleration is equal to zero.
therefore
For that to be true, the sum of all forces (loads) acting on the structure must also be zero.
and
Furthermore, the sum of all moments (rotational forces) acting on the structure must also be zero.
The Greek letter epsilon ( ∑ ) is used to represent the mathematical phrase "the sum of".
So we can express the three fundamental statements of statics with these equations.
∑ F = 0 "The sum of all Forces are equal zero."
∑ M = 0 "The sum of all Moments (rotational forces) are equal to zero"
FREE BODY DIAGRAM
To analyze the forces on an object we want to look at it separate from everything else.
Example #1
∑ F = 0
Read this equation as "The sum of Forces are equal to zero". This mean that if you add up all of the forces acting on the body the sum will always be equal to zero. This is true if the body is "Static" or not moving. If the sum of the forces were greater than zero, then the body would be accelerating (moving) in some direction.
∑ F = Fnorm - Fgrav = 0
If we knew the weight of fish bowl (for example, 15 pounds) we could insert that into the formula and calculate the normal force.
∑ F = Fnorm - 15 lbs = 0
Fnorm = 15 lbs
If the stand was not strong enough to push up with 15 pounds the the fish bowl could not be sitting ontop of it. It would break the stand and fall on the floor. Because the stand is holding the fish bowl, we know the normal force is equal to the weight of the bowl.
Example #2
∑ F = 0
∑ F = Fnorm - Fgrav - F1 = 0
∑ F = Fnorm - 10 lbs - 45 lbs = 0
Fnorm = 10 lbs + 45 lbs
Fnorm = 55 lbs
EXAMPLE #3
Draw a "Free Body Diagram" for a 20 foot long bridge with a 6000 lb load in the middle.
Calculate the Reaction Forces
∑ F = 0
∑ F = R1 - Load + R2 = 0
R1 - 6000 + R2 = 0
R1 + R2 = 6000
We will need to use a different equation to solve this problem. Because we have two unknown forces, we can't solve this equation.
∑ M = 0
Read this equation as"The sum of all Moments are equal to zero".
A "Moment" is just a force acting on a body at some distance from its center of mass. In the fish tank example above, all of the forces were lined up with the center of mass of the body we were looking at. In this bridge example, the load is in the middle but the reaction force are offset to either side. When forces are offset, they create rotational forces called torque but when the object is not moving we call that force a moment. If the sum of all moments were not equal to zero, then the body would begin to spin or rotate. Since a static object is not moving or spinning, we can pick any point to calculate the moment (equal to zero). To solve for one reaction force, we will chose a point that is directly in line with the other reaction force. That will make the distance of the second reaction force to the point we chose equal to zero and zero times any force will be equal to zero (eliminating that variable from the equation).
we will calculate moments about point 1
∑ M1 = R1 x 0 - Load x 10 + R2 x 20 = 0
R1 x 0 - 6000 x 10 + R2 x 20 = 0
0 - 60,000 + 20R2 = 0
20R2 = 60,000
R2 = 3000 lbs
R1 + R2 = 6000
R1 + 3000 = 6000
R1 = 6000 - 3000
R1 = 3000
EXAMPLE #4
∑ Fvert = 0
∑ Fvert = Fnorm + Ffricton - Fgrav = 0
∑ Fvert = Fnorm + Ffricton - 58 kg = 0
Before we go any farther we need to make sure we are only dealing with the vertical components of each force.
Gravity is always pulling down so it is vertical. The Normal Force is always perpendicular to the surface, so in this case is it 12 degrees from vertical (). The Friction force is always parallel to the surface so that is 12 degrees from horizontal, 75 degrees from vertical. This Will require some Trigonometry to solve, so I will not put a problem like this on the test for Intro to Engineering.
∑ Fvert = Fnorm cos 12 + Ffricton cos 75 - 58 kg = 0
∑ Fvert = .966 Fnorm + .289 Ffricton - 58 kg = 0
This still leaves us with an equation with two unknown values. To resolve this we need to sum the force in the horizontal direction. This will let us know the proportion of the normal force to the friction force.
∑ Fhorz = Ffricton cos 15 - Fnorm cos 75 - 0 kg = 0
.966 Ffricton - .289 Fnorm = 0
Fnorm = .966 Ffricton / .289
Fnorm = 3.34 Ffricton
With this answer we can substitute 3.34 Ffricton for Fnorm in our sum of forces vertical equation.
∑ Fvert = .966 Fnorm + .289 Ffricton - 58 kg = 0
∑ Fvert = 3.34 Ffricton + .289 Ffricton - 58 kg = 0
Now we have an equation with only one variable so we can solve for Ffricton .
3.34 Ffricton + .289 Ffricton - 58 kg = 0
3.63 Ffricton = 58 kg
Ffricton = 58 kg / 3.63
Ffricton = 16 kg
Now with that answer we can substitute 16 kg into the equation for Ffricton
∑ Fvert = .966 Fnorm + .289 Ffricton - 58 kg = 0
∑ Fvert = .966 Fnorm + .289 (16 kg) - 58 kg = 0
.966 Fnorm + 4.624 - 58 kg = 0
.966 Fnorm = 53.376 kg
Fnorm = 53.376 kg / .966
Fnorm = 55.25 kg
Calculating Stresses in a Structure
To design a structure you need to make sure that each of the members are designed to resist the stresses it will experience when load is applied to the structure.
Example 1
King Post Trust Bridge
Example 2 Pratt Truss
Example 3 - Warren Truss Bridge
Page updated
Report abuse