Bridge Type Beam Bridge Truss Bridge Arch Bridge Suspension Bridge Design Features Distance Range Important Forces
Last name: First name: Date: Period: BRIDGES INTRO Welcome to Craggy Rock! COM INC COM* You got here just in time. This growing community needs four new bridges, and they're very picky about what they want! Test your engineering skills and try to match the right bridge to the right location. By the way, you may use each bridge type only once -- that's a direct order from the mayor of Craggy Rock. Good luck! Location 1: What type of bridge would be best? Why? Location 2: What type of bridge would be best? Why? Location 3: What type of bridge would be best? Why? Location 4: What type of bridge would be best? Why?
The beam bridge... consists of a horizontal beam supported at each end by piers. The weight of the beam pushes straight down on the piers. The farther apart its piers, the weaker the beam becomes. This is why beam bridges rarely span more than 250 feet. Beam bridge Beam Bridge: Forces Bending is the primary force that weakens beam bridges. When too much weight pushes down on the beam, the beam bends. Its top edge is pushed together by compression (getting shorter), and its bottom edge is pulled apart by tension (getting longer).
Cantilever bridge: Firth of Forth The truss bridge... consists of an assembly of triangles. Truss bridges are commonly made from a series of straight, steel bars. The Firth of Forth Bridge in Scotland is a cantilever bridge, a complex version of the truss bridge. Rigid arms extend from both sides of two piers. Diagonal steel tubes hold the arms in place. Truss Bridge: Forces A truss bridge is designed so that every bar experiences either a pushing (compression) or pulling (tension) force. However, because the bridge has so many bars, the bars rarely bend. The middle of the bridge is also strongly supported by the arms, which is why truss bridges can span farther than beam bridges (up to about 2000 feet).
The arch bridge... has great natural strength from its curved shape. Thousands of years ago, Romans built arches out of stone. Today, most arch bridges are made of steel or concrete and can span up to 800 feet. Because arch bridges are simple and elegant, they are often found as walking paths in city centers. Arch bridges are also commonly used to span tall canyons. New River Gorge Bridge Arch Bridge: Forces The middle of the arch bridge is its weakest point. When weight is added to the top of an arch, the sides want to spread outward. The supports in an arch bridge, called abutments, push back on the arch (compression) and prevent the ends of the arch from spreading apart.
Suspension bridge: Golden Gate Bridge The suspension bridge... can span 2,000 to 7,000 feet -- way farther than any other type of bridge! In all suspension bridges, the roadway hangs from massive steel cables, which are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge. Most suspension bridges have a truss system beneath the roadway to resist bending and twisting. Suspension Bridge: Forces The weight of the cars pushes down on the roadway but this force is counteracted by tension in the cables. The cables transfer the load into compression in the two towers. The two towers support most of the bridge's weight. Because of the large distance between towers, suspension bridges can be susceptible to torsion, or twisting, in very windy conditions.
Location 1: Build a multi-lane bridge for commuters and tourists Span: 2,000 feet Crossing: River Connects: City and major highway Special Notes: "I want a one-of-a-kind bridge that will span our beautiful river and welcome visitors from all over the world to our thriving city. Make sure the new bridge leaves enough room for sailboats on the river. Please don't build a bridge that looks like the Golden Gate Bridge in San Francisco or the Brooklyn Bridge in New York." -- Mayor of Craggy Rock What kind of bridge should you build? (Select one) Beam Suspension Arch Drawbridge Truss
Location 2: Build a bridge for walkers, joggers, and bikers Span: 100 feet Crossing: Stream Connects: Two bike paths Special Notes: "We're tired of getting bumped off the road by angry drivers! We want a simple bridge -- one that will connect the bike paths in East and West Craggy Rock over the city stream. We don't have much money, so we're not asking for much. We just want to get to work every day without risking our lives!" -- Craggy Rock Bike-n-Blade Coalition What kind of bridge should you build? (Select one)
Location 3: Build a highway bridge across a busy shipping port Span: 5,000 feet Crossing: Ocean bay Connects: Island and mainland Special Notes: "Our records indicate that more than 500 ships pass through Craggy Rock Harbor each day. Please build a bridge that does not block the flow of water traffic. We do not want angry sailors or congestion of any kind in our harbor. Thank you." -- The United States Coast Guard What kind of bridge should you build? (Select one)
Location 4: Build a railroad bridge in a national park Span: 500 feet Crossing: Deep river gorge Connects: Two rocky bluffs Special Notes: "We do not want the new bridge to detract from the natural beauty of Craggy Rock National Park. Please build a simple and elegant bridge -- one that does not have towers or piers." -- The National Park Service What kind of bridge should you build? (Select one)