Emergency Response Training Class Gary Bowling, Oregon DOT Bridge Engineering Section
Presentation • Purpose • Bridge Components • Preparation for the Inspection • Performing the inspection • Reporting the results
Purpose • Make some ordered sense of the chaos and provide you with a clear understanding of how you fit into the big picture. • Maximize the use of available personnel. • Minimize duplication of effort.
Purpose • Minimize Confusing and Conflicting Reports. • Provide an accurate accounting of the condition of the bridges under your jurisdiction. • Bottom line: Insure the safety of the driving public.
Major Bridge Components • Deck • Superstructure • Substructure • Foundation • Utilities
Bridge Components Deck Railing Superstructure Girders Cap Substructure Columns Foundation
Deck • The deck carries the roadway / sidewalk. • The deck is supported by the superstructure. • Transfers vehicular loads to the superstructure.
Superstructure • Superstructure members transfer traffic loads from the deck to the substructure. • Superstructure members can be exposed to tension, compression, and bending forces.
Substructure • The substructure transfers loads from the superstructure to the foundation material. • The substructure is generally exposed to axial compressive forces. • Can be supported by spread footings or piling.
Major Bridge Components(Utilities - APWA Color Code) • Electrical • Gas • Communication • Potable Water • Irrigation • Sewer Company & Phone No. Red Company & Phone No. Yellow Company & Phone No. Orange Company & Phone No. Blue Company & Phone No. Purple Company & Phone No. Green
Utilities Sewer Line
Bridge Nomenclature Describing where the problem is?
Rules of Orientation and member numbering • Look ahead at increasing milepost or city street addresses. • All bridge items are numbered in consecutive order from the leading end of the bridge and left to right.
Bridge Nomenclature • Bent - a substructure unit that supports the superstructure of a bridge and is supported by the foundation. • Bents are numbered consecutively in the same direction as increasing highway mileposts, or city street addresses.
Bent 3 Bent 4
Bridge Nomenclature • Span - portion of the bridge superstructure that is located between two bents. • Spans are numbered numerically, in consecutive order, in the same direction as increasing highway mileposts, or city street addresses.
Bridge Nomenclature Increasing Mileposts Span 9 Span 11
Bridge Nomenclature • Superstructure Members can be timber, steel or concrete. • Superstructure Members are numbered numerically, in consecutive order, from left to right, while looking ahead, on line, at increasing mileposts, or city street addresses.
Span 3 Girder 1 Span 3 Girder 2 Span 3 Girder 3
Bridge Nomenclature • Substructure Members can be steel, concrete or timber. • Substructure Members are number numerically, in consecutive order, from left to right, when looking ahead, on line, at increasing mileposts or city streets.
Bent 3, Column 4 Bent 3, Column 5
Bridge Nomenclature • When the structure has Intermediate Spans or Columns that are founded on larger spans. • The columns/spans are numbered consecutively, with the bent/span number along with an alphabetical letter. • Commonly occurs on an arch span.
Span 5B Span 5A Bent 5B Column 4 Span 5 Bent 5A Column 4
Bridge Nomenclature • A Truss is a structure that is made up of individual members that are arranged and connected, in triangular patterns, to create a long span. • A Truss is made up of at least two chords, an upper chord and a lower chord. • Truss Panel Points - are located on the chords where two or more truss members are connected.
Upper Chord L0 LowerChord Panel Point
Bridge Nomenclature • Panel points are numbered consecutively, in the same direction as the designated bent or span, starting with “0”, along with an identifier to show whether the panel point is on the upper chord, lower chord, an intermediate point, and whether it is on the left or right truss. • Truss Members are identified by using two panel point designations.
Increasing Mileposts U6R U8RL9R L12RU13R L5R
Bridge Mechanics • Load Paths • Bending, Tension, and Compression
Bridge Mechanics (Compression) Compression Tension (Tension) Bending
Deck is in bending Girders are in bending Cap is in bending Columns are in compression
Bridge Mechanics Visualize a rope hanging from two panel points. Members in compression will be much thicker members. Members in Tension will be much thinner in section.
Properties of Bridge Materials • Design Criteria - Seismic forces that develop during the vibratory response of a structure to earthquake ground shaking at its foundation are inertia forces whose intensity depends on the product of the mass and acceleration. (Force = Mass of the bridge X Ground Acceleration)
Properties of Bridge Materials(Timber) • If the structure is provided with proper lateral bracing and all of the components are adequately tied together, timber is one of the more efficient earthquake resistant materials for low-rise structures. • Timber is a very resilient material.
Properties of Bridge Materials(Reinforced Concrete) • Even though Reinforced Concrete tends to be very massive, it can be used effectively if it is properly reinforced. • The proper amount of steel reinforcement and correct detailing plays a very important role in the seismic response of the structure.
Typical Reinforced Concrete Girder Rebar Stirrups Primary Steel Reinforcement
Typical Pre-stress Concrete Girder Prestressing Strands or Post-tensioning Conduits Prestress Strand Jacking Load + 160,000 psi
Properties of Bridge Materials(Steel) • Because of its high strength per unit weight, Structural Steel members are usually very slender. Thus buckling becomes a serious problem. • Member Connections can also be a problem for steel structures.
Typical Structural Steel Sections Flange Web
Employee Safety and Equipment • ODOT is committed to a safe and healthy workplace through prevention, equipment maintenance, education, training and compliance with all state and federal regulations.
Job Safety Analysis (JSA) • Dissect the job into sequential steps. • Identify the potential hazards of each step. • Specify how each hazard will be mitigated. • Follow the game plan.