Bridges

History of Bridges The earliest bridges were primitive. – Logs falling across a stream are considered the earliest bridge. – Following that was the practice of stringing large vines across the two areas needing to be bridge Engineered arches originated in the Middle East approximately 4,000 BC

Rome Romans applied the arch for bridges and aqueducts around 800 BC Though they constructed many kinds of bridges such as wooden and beam bridges – They are known for their stone arch bridge Stone arch bridge withstood heavy use and can still be seen today in Europe Civil Engineering – Branch of engineering relating to the building of municipal systems, such as roads, bridges, dams, and communication towers.

London Bridge Notable bridge of the medieval period Massive stone bridge that replaced an older wooden bridge Built by Peter Colechurch Completed in 1209 AD Featured 19 arches Lasted 600 years Needed frequent repairs – “London Bridge is Falling Down”

Ponte Vecchio Florence, Italy Architects:Taddeo Gaddi and Neri di Fioravante Spans 276’ over the Arno River Arch/Deck arch Bridge

Jean Perronet “Father of Modern Bridge Building” Best known Bridge – Pont de la Concorde in Paris Arch Bridge Completed in 1791 Still stands today

Civil Engineering Education Drafting – Skills and knowledge needed to visually communicate ideas on paper or a computer program Surveying – Accurately gather information about Earth’s surface Soil Science – Determines the characteristics of the type of foundation needed

Civil Engineering Education Mathematics – Calculating stresses on a structure or analyzing the material requirements of each member. Materials and processes – Provides an understanding of the strength and other characteristics of metals, woods, plastics, etc. Transportation – Awareness of all laws relating to transportation and construction of roadways, bridges, and other highway systems

Civil Engineering Education Environmental Issues – Examines how the environment effects construction and provides information necessary to protect people and the environment Physics – Explores physical principals and mathematical equations that are key to designing sound structures

Factors in Bridge Design What is the span of the bridge? What will be the load of the bridge? What type of load will the bridge have? What environmental factors will affect the bridge? What is the budget allowance for the bridge? What are the soil characteristics of the banks? What are the soil characteristics for the bottom of the river is support columns are needed? What is the construction time frame?

Truss King Post – A central vertical post used in architectural or bridge designs Warren – Consists of longitudinal members joined only by angled cross-members Pratt – Consists of longitudinal members joined only by angled cross-members

Truss K Truss – A truss in the form of a K due to the orientation of the vertical member and two oblique members in each panel Whipple – Considered a subclass of the Pratt truss because the diagonal members are designed to work in tension. The main characteristic of a Whipple truss is that the tension members are elongated, usually thin, at a shallow angle and cross two or more bays

Types of Trusses King Post TrussWarren Truss

Types of Trusses Pratt TrussK-Truss

Types of Trusses Whipple BowstringBollman Truss

Types of Trusses Town LatticeHowe Truss

Terms Bridge – Structure that spans a gap Design – Process of creating Angle – Figure formed by two lines extending from the same point Limit – Constraint Critical load – Weight a structure can support before failing Compression – Tendency to push, squash, or squeeze a material Average – Value provided by dividing the sum of a set of quantities in a set Criteria – Set of standards or rules on which a judgment or decision can be based Beam – Horizontal supporting member Conclusion – Reasoned judgment

Terms End grain – Grain of wood as seen from the end of a wood strip Dimension – Measure in one direction Hypothesis – Prediction based on prior knowledge made in order to test its consequences Efficiency – Strength to weight ratio Force – Capacity to do work or cause physical change; energy, strength, or active power

Terms Inference – Act of deriving logical conclusions from premises known or assumed to be true Lamination – Layering a structure Load – Overall force that a structure is subjected in supporting weight Load-bearing capacity – Maximum load that a system can support before failing Mass – Amount of matter within an object Superstructure – Structure of the bridge that extends above the roadbed Scale – System of proportion Modification – Change the properties, form, or function

Terms Truss – Rigid framework, designed to support a structure Sketch – Drawing Substructure – Structure of the bridge that extends below the roadbed Model – Small object built to scale Timber – Wood used for building materials Span – Distance between supports Tension – Force pulling apart materials

Truss Bollman – Only surviving example of a revolutionary design in the history of American bridge engineering. Employs wrought iron tension members and cast iron compression members. Town Lattice – This type of bridge uses a substantial number of lightweight elements, easing the task of construction. Truss elements are usually of wood, iron, or steel. Howe Truss – Includes vertical members and diagonals that slope up towards the center, the opposite of the Pratt truss.