Bridge Exam

Beam-Pros and Cons

-: Easy to build; inexpensive relative to other bridge types; used widely in urban and rural settings -Limited span; large ships or heavy boat traffic cannot pass underneath; design generally not considered very interesting or eye-catching

Why do architects and engineers build arch bridges?

-Can be built using a wide range of materials The basic principle of arch bridge is its curved design, which does not push load forces straight down, but instead they are conveyed along the curve of the arch to the supports on each end. These supports (called abutments) carry the load of entire bridge and are responsible for holding the arch in the precise position unmoving position. Conveying of forces across the arch is done via central keystone on the top of the arch. Its weight pushes the surrounding rocks down and outward, making entire structure very rigid and strong. *Sturdy *Vast range of materials can be used

Suspension-Pros and Cons

-Span distances up to 7,000 feet; considered attractive; allow large ships and heavy boat traffic to pass underneath -Expensive (require a long time and a large amount of material to build)

Cable Stayed-Pros and Cons

-Span medium distances (500-2,800 feet); less expensive and faster to build than suspension bridges; considered attractive -Typically more expensive than other types of bridges, except suspension bridges

Truss-Pros and Cons

-Very strong; frequently used as a draw bridge or as an overpass for railroad trains -Difficult to construct; high maintenance; difficult to widen if necessary; generally not considered attractive

Arch-Pros and Cons

-Wide range of materials can be used; considered attractive; very strong -: Relatively expensive; typically, designs are limited to certain sites (e.g., where the ground can support the large forces at the base of the arch; where the span-to-depth ratio of the arch is proportional; or where an arch is visually appropriate)

What is the surface area of a cross section of 1/8 in x 1/8 in. balsa wood beam?

0.00004 in4 ????? ASK MRS.FOSTER

When a horizontal beam bends down in the middle , the top of the beam is in : A.Tension B. compression C. torison D. Shear

ASK

Which type of Bridge design is Most effective for a short span bridge

Arch Bridge

Beam

Beam bridges are the oldest known bridges and tend to be the simplest to design and build. Roughly half of all bridges in the United States are beam bridges. They consist of vertical piers and horizontal beams. A beam bridge's strength depends on the strength of the roadway and can be increased by adding additional piers. While beam bridges can be quite long, the span, or distance between adjacent piers, is usually small.

What is the name of a famous suspension bridge?

Golden Gate Bridge

The force of gravity pushing down on a bridge is an example of which Newton's laws?

Newtons 3rd Law

Where is there a cable-suspended bridge located ?

San Fransico, CA

Which type of Bridge is Most effective for a long span?

Suspension bridge

What is the name of a famous arch bridge?

Sydney Harbour Bridge

What does surface area mean?

The area of such an outer part or uppermost layer

Cable Stayed

The first modern cable-stayed bridge was completed in Sweden in 1956. Cable-stayed bridges were created as an economical way to span long distances. This bridge's design and success were made possible as new materials and construction techniques were developed. Cable-stayed bridges have one or more towers, each of which anchors a set of cables attached to the roadway.

Arch-Effect

They are often chosen for their strength and appearance. It is the shape of the arch that gives the bridge its strength, which is reinforced by placing supports, or abutments, at its base. Arch bridges can be built from various materials, including wood, stone, concrete, and steel.

Why are Triangles used in bridges?

Triangles are used in bridges because they evenly distribute weight without changing their proportions. When force is applied on a shape like a rectangle it would flatten out. Before triangles were used in bridges, they were weak and could not be very big

Identify the four types of trusses

Warren Truss Parker Truss Camelback Truss Pennslyvania Truss

Truss

Wooden truss bridges were used as early as the 1500s, but the first metal one was completed in 1841. They are very strong and have been used for railroad bridges mainly because of the heavy loads that they can support. A truss, a rigid support structure that is made up of interlocking triangles, holds up the roadbed and is set between two piers. The triangle is used because it is the only shape that is inherently rigid.

Three parts to a suspension bridge are the towers, the cables and the ___________________?

cables

Force Diagram-Arch Bridge

https://www.google.com/search?q=arch+bridge+forces+diagram&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjdtMOL45nbAhWDrVkKHS24BmMQ_AUICigB&biw=1433&bih=776#imgrc=CGp2zEmZ34_psM:

Force Diagram-Beam

https://www.google.com/search?q=beam+bridge+force+diagram&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi4zLDb45nbAhUkwVkKHe0kBogQ_AUICigB#imgrc=zQTSzYFOhDobvM:

Force Diagram-Cable Stayed

https://www.google.com/search?q=cable+stayed+bridge+force+diagram&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiwoP-e5JnbAhWNtlkKHeQ8B4IQ_AUICigB#imgrc=5Mq3e_ZjelXehM:

Force Diagram-Suspension

https://www.google.com/search?q=suspension+bridge+force+diagram&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi_i6DC45nbAhVCpFkKHfM4BZ4Q_AUICigB&biw=1433&bih=776#imgrc=cr3-vkR53SMUWM:

Force Diagram-Truss

https://www.google.com/search?q=truss+bridge+force+diagram&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjFkt6C5JnbAhWExVkKHbtWB9EQ_AUICigB#imgrc=oaSq-wBtPCA2EM:

Suspension-Effect

suspension bridges are strong and can span long distances. One early bridge was designed and built in 1801 in Pennsylvania. They are commonly found across harbors with a lot of boat traffic. The primary elements of a suspension bridge are a pair of main cables stretching over two towers and attached at each end to an anchor. Smaller cables attached to the main cables support the roadway. *Very strong; frequently used as a drawbridge or as an overpass for railroad trains