Lecture 18a

Sub-structure:Design of Piers

Pier for S-826 connector at NW 103 Street, Miami.

Expansion of the deck from one-lane to two-lanes for the I-75 ramp from S-826 at Hialeah.

The new piers for the I-494 Wakota Bridge over the Mississippi River at South St Paul, Minnesota. The new bridge consists of twin long-span, cast-in-place, segmental concrete bridges. Each bridge is 98 feet in width with five lanes and two full-width shoulders. The five spans clear 1,879 feet with the maximum span of 466 feet. Substructure used 4 ksi concrete and the superstructure 6 ksi. Post-tensioning consists of 270-ksi seven wire super strand with 23 x 0.6 in-diam. strand tendons in the longitudinal direction and 4 x 0.6 in-diam. strand tendons in the transverse direction. The piers shown above flare up to match the box girder soffit and web incline angle. Note the icebreaker section. The box girders are attached to the stem walls with the reinforcing steel from the stem wall extending into the box girder diaphragm walls.

Lake Maracaibo’s segmental box girder bridge.

Seismic Effects upon Piers

Route 5 (Truck Lane)/ 405 Separation. This was a cast-in-place pre-stressed box girder with two 177’spans on a curved skewed alignment. The bridge collapsed at the bent, which consisted of two columns with #4 ties at 12”. The structure was a complete loss and was immediately demolished and removed.

San Fernando Road Overhead (Route 210). Two-span, cast-in-place pre-stressed concrete box girder with single column bents. Approach fills settled on foot. Bridge sagged four feet at base due to shattering of column at base.

San Fernando Road Overhead (Route 210) – Column Failure. Close up of column base. Concrete core at base was lost and #18 bars buckled (ties were #4 @ 12”). Structure was entirely replaced.

Column shear and buckling failure at 5/210 Interchange – Foothill Boulevard Underpass, four-span reinforced concrete box girder with four column bents. The superstructure appeared to have no damage.

Column shear and buckling failure. Foothill Boulevard Under-crossing. Octagonal tied columns (#4 @ 12 inches).

Shear failure at the top of the column.Foothill Boulevard Under-crossing.

Anchorage failure.Route 210/ Separation & Overhead.Bars pulled out of the pile shaft.

Cypress Creek Viaduct, I-880, collapsed by the Loma Prieta Earthquake, Oakland, California.

The Cypress Street Viaduct, I- 880 (Nimitz Freeway). This photo of the East side of freeway shows the collapsed structure. The reinforced box girder structure had spans varying from 71 to 90 feet in length (80 feet average). The curb-to-curb width of the bridge was approximately 52 feet. The columns (both lower and upper level) were separated about 15 feet in height.

Cypress Street Viaduct, I-880 (Nimitz Freeway).

Detailed view of the collapsed upper level, with the column showing longitudinal steel.

The confinement was #4 bars at 12-inch spacing.

The hinge at the right was retrofitted with cable restrainers.

Cypress Street Viaduct, I-880 (Nimitz Freeway). Photo shows the East side of the freeway at 32nd Street. The upper level column was tapered at the base and joined to the lower level column as a hinge connection. Note that the shear key and dowels are shown.

Bull Creek Canyon Channel Bridge – Failed columns by the channel paving.

Mission-Gothic Under-crossing. Column failure under the architectural flare.

La Cienega – Venice under-crossing. Column failure.

Fairfax – Washington Under-crossing. Column failure.

Jan. 1995 Earthquake. Map showing the Hanshin Expressway and the Port of Kobe City.

Failure of the column connections and the collapse of the super-structure spans.

Hanshin Expressway.

Buckled steel piers.

Close-up of buckled portion of steel piers.

Hanshin Expressway.

Shear failure of a massive rectangular reinforced concrete pier.

Hanshin Expressway. Failure of the butt welds in the longitudinal reinforcement.

Hanshin Expressway. Failure of the transverse confining reinforcement.

Hanshin Expressway. Shear failure of a massive rectangular reinforced concrete pier.

Hanshin Expressway. Pier failure.

Hanshin Expressway. Failure of single pier bents.

Bearings

Hanshin Expressway. The spherical housing for the fixed bearing failed at the support for the arch bridge.

Hanshin Expressway. Shear failure of bolts connecting the transverse keeper plate to the bearing assembly.

Hanshin Expressway.

The new bearings delivered to the jobsite to replace those that failed were in-kind type replacements.