FHWA launches new nationwide seismic bridge design training

Public Roads, Autumn, 1996 by James W. Keeley

The second example is a 122-m, three-span, skewed steel plate girder bridge over a river in New England in AASHTO Seismic Performance Category B with a design acceleration of 0.15 g. The superstructure rests on steel-reinforced elastomeric bearings and wall piers with spread footings on rock. This example highlights the modeling of elastomeric bearings, skew effects on girder systems, varying cross sections, and wall pier design.

The third example is a skewed, 21-m, single-span, prestressed concrete girder bridge with tall, closed, seat-type abutments on spread footings. This bridge is in the Mississippi Valley with a design acceleration of 0.36 g. It illustrates AASHTO's requirements for tall abutments and the Mononobe-Okabe method of determining seismic earth pressure forces.

The fourth example is a 98-m, reinforced concrete box girder, three-span, skewed bridge in the western United States with a design acceleration of 0.30 g. It has two column bents with pinned connections between the columns and spread footing foundations. It illustrates skew effects, foundation springs for spread footings, two-column behavior, and pinned base column design.

The fifth example is a 454-m, steel plate girder bridge in the inland Pacific Northwest with a design acceleration of 0.15 g. It has nine spans and consists of two units - a straight four-span Unit 1 and a curved five-span Unit 2 with a 396-m radius curve. The superstructure is composed of four steel plate girders with a composite cast-in-place concrete deck. The substructure elements, seat-type abutments, and single-column intermediate piers are all cast-in-place concrete supported on steel H-piles. All substructure elements are oriented to the centerline of the bridge. This example illustrates preliminary seismic design, multiple-unit behavior, deck force transfer through steel cross frames, seismic performance category B effects on single-column piers, and steel pile design.

The sixth example is an 88-m, sharply curved (104 degrees), three-span, concrete box girder bridge in the northwestern United States with a design acceleration of 0.20 g. The substructure is composed of steel pipe piles in monolithic end-wall-type abutments and single-column flared piers founded on drilled shafts. This example illustrates the effect of large curvature, drilled shafts, integral abutments with piles, and rectangular flared column to circular drilled shaft detailing.

The seventh example is a 219-m, 10-span, prestressed girder bridge with open pile bents and a design acceleration of 0.10 g. The super-structure consists of three continuous-span bridges arranged in a 3-4-3 span series. This example illustrates preliminary seismic design for six different options for the pile piers - three versions of concrete piles and three versions of steel piles. The three versions of both the concrete and steel piles include one plumb pile and two batter piles. For each option, the seismic analysis is done using hand calculations to illustrate how various pile options can be quickly evaluated without using a computer.