BRIDGE EXPLORATIONS What makes bridges stay up What makes bridges fall down Different types of bridges You will design and construct a bridge You will test your bridge’s load capacity Beam Bridges The Tarr Steps – England Circa 1000 B.C. KOCHER VIADUCT, AUTOBAHN, GERMANY 185 m HIGH, 1128 m LONG Top of beam is in compression and bottom is in tension. The middle of the beam is neutral – the middle is in neither compression or tension. Making a beam stiffer: I Beams move most of the beams material away from the neutral axis which is underutilized. This results in a stiffer beam. Arch Bridges PONT DU GARD, FRANCE, 63 BC-13 BC 47.4 m HIGH Arches are made of wedge-shaped stones in compression. Without the keystone the two sides of the arch will fail. The wedged stones at the bottom must be prevented from moving outwards using abutments (stones anchored into the soil). MOSTAR BRIDGE, YUGOSLAVIA 1566-1567 27.3 m SPAN, 19 m HIGH Cabin John Bridge, Washington D.C. RHINE RIVER, BONN- BUEL, 1948 FRANCIS SCOTT KEY BRIDGE, WASHINGTON, DC HEILBRONN, AUT0BAHN, GERMANY Truss Bridges A truss is a hinged triangle TENMON BRIDGE, KUMAMOTO PREFECTURE, JAPAN SPAN 100 + 300 +100 m 42 m CLEARANCE, 1966 Why are trusses so common? The members are in either experiencing compression or tension; the members are not bending. Trusses can be arranged into many shapes. Truss Bridge with a moveable center section. Cabin John Bridge, under construction using timber false work Cantilever Truss Bridge Cantilever Bridges Cantilever is a beam supported at only one end. The Forth Rail Bridge – c.1882-1889 Scotland One the worlds most massive bridges. Suspension Bridges Akashi-Kaikyo Bridge 3911 m http://www.youtube.com/watch?v=kuW HIAOxcLA&feature=PlayList&p=B7C0C 5CE439D8D7C&playnext=1&playnext_f rom=PL&index=11 Cable is made by running spools of smaller cable back and forth across the towers. This is called spinning the cable. Cable Stay Bridges Kaohsiung County, Taiwan Øresund Bridge between Denmark and Sweden Relatively inexpensive to construct – no large cables need to be spun over towers. Able to span large distances. What kind of Bridges? MARACAIBO BRIDGE, VENEZUELA, 1957 FEHMARNSUND BRIDGE, 248 m SPAN Combination arch and beam. GANTER BRIDGE DESIGNED BY CHR. MENN Engineering Design Process • • • • Problem Statement Problem Analysis Design Specifications Brainstorming / Idea generation • Idea Selection • Implementation Problem Statement What is the maximum load a short paper bridge can carry? Problem Analysis • How will structure carry loads? • How is failure likely to occur? • What can be done to prevent failure? Design Specifications 10” minimum span 1” max. bearing at abutment Tape is connector only. Bridge cannot be taped to the abutment. Materials: Three 2”X12” strips (cut from heavy poster paper) Idea Generation & Selection Brainstorming Minimize judgment Combine ideas Select final idea based on best fit for Design Specifications Implementation Construct bridge Test bridge Review and evaluate design