Structures 1

Deck: Bridge Deck Framing

Is the surface of a bridge. The framing is the core that lies directly below the deck and rests on the substructure.

Axial Force

The compression or tension force applied to a structure along the length of its axis or perpendicular to the cross-section of the member. Stress (σ) = Force (F) / Area (A)

Suspension Bridge

A bridge that has its roadway suspended from one or more cables usually passing over towers and securely anchored at the ends.

Bending Force

A load applied to a specific part of a given material. It can be applied to a point, area, or volume. The unit for this calculation is pound

Deformation

It occurs when a structure changes its shape due to loads. Any structural element under load has some amount of deformation. When the load is removed, the element should gradually go back to its original state; if it does not, the deformation will be permanent. Structural elements have a stress limit, which is the maximum load it can resist before deforming permanently.

Loads; Dead, Live, Total

the permanent self-weight of a structure. (Construction Materials): the moveable, changing weights on a structure. (People/Vehicles)Total load = (live loads) + (dead load)

Gravity v Lateral Forces

The force causing attraction between any objects with mass towards their center. Any object with mass also contains gravitational forces; more mass means a larger load experienced within the object.

Lives loads that project their force horizontally onto the structure on which they act. Wind & Earthquake - lateral loads are geographically dependent

Anchor Plate, Washer and Nut

Flat wide piece of material that evenly distributes the load between bolts.

A thin disc with a hole in the middle that is used to evenly distribute the load of a fastener such as a nut or bolt.

A fastener in the shape of a hexagon that has a threaded hole in the middle in order to fasten a bolt. The hexagon shape makes it easier to tighten

Tributary Area

Area is the area of floor or roof (in plan) that causes loading on a particular structural element.

Force Polygon

a closed geometric shape whose sides taken in order represent in magnitude and direction a system of forces in equilibrium. Travel tip to tail and can be represented mathematically or graphically

Magnitude, Direction, Line of Action of Force

Three primary characteristics of a force. Magnitude is the amount of force that is applied. Direction is the angle of the force.Line of Action of Force is a line along the centerline of the force that extends indefinitely in both directions

Scalar vs Vector

Has both direction and magnitude. The line of action of a force of a vector is an infinitely straight hypothetical line that is collinear with the vector.
Quantities are defined as magnitude alone.

Span and Span to Depth Ratio

Span - The length of a structural component. Span to Depth Ratio - also known as slenderness ratio, is the ratio of the span length divided by the depth (vertical height). It is an important factor due to its impact on structural behavior as well as construction costs.

Concurrent and Non-Concurrent Forces

A set of point forces is considered concurrent if all the lines of action of those forces come together at a single point. Forces that do not intersect at a single point can create rotation and are considered non concurrent forces

Free Body Diagram

A simplified picture of a portion of a structure, completely detached, with vector arrows that indicate all of the external forces that act upon the free body.

Jaw Fork Clevis

Clevis fork joints, clevis fork heads, and joint pieces are connectors that allow lever arms and linkages to conduct thrust and traction. They are available in designs that rotate and with varying pin positions.

Static Equilibrium

A body at rest with the forces that act on the body balancing one another exactly. "Static" means the body is at rest and "Equilibrium"means the forces acting on the body are exactly balancing one another.

Stability

The response to unwanted movement and gross deformation to the structure that keeps it together. It depends on the condition of different components that help keeps its position against nature and forces that works against it. Structures that are able to resist applied load without moving in a big fashion are stable structures

Buckling

A structural instability created when a certain change in axial load disturbs a columns(or beams) equilibrium causing it to fail suddenly and catastrophically in a way that it cannot reset to its original form after the axial load is removed.

Uplift Forces

Uplift forces come from wind on either the side or below the structure. The weight of a bridge is usually substantially higher than the uplift forces acting upon it. Therefore, uplift resistance is usually created automatically. If the bridge is lightweight, then a funicular arrangement of rods can be used to resist the forces. In the case of a building, uplift forces are combated by the weight of the building or by the addition of supports.

Yield Strength

The tensile force at which a rod would stretch irreversibly. This force value is divided by the factor of safety in order to determine the allowable stress.

Factor of Safety

Definition: The ratio of ultimate stress of the component material to the working stress.

FOS leaves room for unusual or unpredicted events

FOS= ultimate load (strength) Allowable load (stress)→ FOS = actual capacity/demandUsing a factor of safety increases safety and decreases risk.Things that affect FOS-Material properties and strength-Changes in material properties and strengthover time -Types of loading

Funicular Form

Cables/Chains or arches connecting two adjacent points and applying pressure from their given load. This can lead to tension and compression.

Force; Tension/ Compression

A tension force is a force that pulls a material apart and is usually a thinner member. A compression force squeezes materials together, were axial Compression forces can result in buckling between the members.

Truss

A supporting spanning structure, typically made of wood or steel, composed of several members connected together at endpoints or nodes (forming triangles)*Trusses as a whole act as bending, individual members act as either compression or tension depending on each scenario*

Stress

The axial force on a member divided by the cross-sectional area of the member:f (N/m²)=P (N)/A (m²)

Parallelogram Law

The Parallelogram Law states that the resultant of any two vectors will be the diagonal of a parallelogram formed on their vectors.

Rod vs Cable

A Cable is any flexible tension member that is made up of steel wires. Cables are a flexible element that works primary in tension.A rod is a rigid element that works primary in tension. Rods are used when the loads that are created are smaller and when cables that would hold the corresponding load would be too small. Rods are also easier and cheaper to connect than cables.

What makes a structure great?

Efficiency-materials used to make it safe Economy - life cycle and avoid overspending
elegance- aesthetically pleasing

Define "funicular"

Ideal form for a certain load case: Tension only or compression only

What is difference between gravity and lateral loads?
What are the two primary categories of gravity load?
What are the two primary types of lateral load?

Gravity is the force causing attraction between any objects with mass towards their center. Live and dead loads. Lateral loads
Wind & Earthquake lateral loads are geographically dependent.

Define truss:What two assumptions are often made when designing trusses?
...and what is the significance of these assumptions?

A supportive structure that's a long spanding elements when a beam would be insufficient. It's made of rigid triangular elements that can be 2d or 3d and made of wood or steel.

Assumptions: all loads applied to nodes
All joints at nodes are pinned connections. Forced in 2 directions.

How does a truss develop its internal resisting moment?

All loads and reactions are applied to the nodes. All forces are axial; through tension or compression.

What are the most common materials used for trusses? Why?
Why / where are trusses used?

Steel and Wood. When a beam is insufficient: sports complexes and large areas. Each trusses linear elements work in tension or compression, and other materials couldn't handle the stress.

What is difference between a strut and a cable?

Cables all work in tension and struts work in compression.

What is difference between Analysis and Design?

Analysis is investigation and design is creation. Anaylsis answers is the system safe and design is the configuration of members to be safe for assumed load.

How are loads determined?
Gravity
Dead
Live
Snow
Lateral
Wind
Seismic

Gravity
dead load-calculations
live load- program and load based
Lateral
-Wind and seismic- location
Snow- location

Define Tributary Area
Why work in PSF?

A zone or space that is responsible for supporting load(beams, girders, cables, suspension cable, spandrel walls)

Everything is in dead load that's measured in PSF

Details/Connections - definition
Details/Connections - what are some goals/objectives?
What is a "working point"?

Connecting members to other members- nodes, joints, ect.

Transfer loads to the ground- load path- goes through these points and members to the ground. Goals: safe, strength, adequately connected and sized, not flimsy, aesthetics, buildable and constructible.

Location where lines of actions of all members at a node should intersect to avoid bending.

Once the member force is known, from force polygon, how is the member size determined?
What is mean by member size?
What process is used for axially loaded members?

By measuring or by using the axial stress equation F=P/A, Tensile members, f=P/A, compression can do the same but worry about buckling
No F/p=A for cable but tower

Member size is related to the amount of load applied to an an area.

Define load tracing
Define FBD
Explain concentrated load vs. distributed load
What are the three types of supports?
What is a bay of framing?

The path loads take- beam -girder-column

Simplistic visual diagram of the ridged body with all forces acting upon it.

A concentrated load is a load that acts at one point and is distributed is dispersed amongst everything point load is concentrated load.
Roller:1 reaction, Pin 2 reactions, ridged : 3 reactions
Space between columns- typically square of rectangular.

What is difference between "span" and "spacing"?

Spacing is how far apart members are- the distance between parallel member supports
spanning is the distance between member supports often perpendicular to each other