UCII: On-Line Bridge Monitor

Bridge Details:

The bridge selected for this project was one of several bridges being built during the final construction stage of the Ronald Reagan Cross-County Highway in Cincinnati, Ohio. The test bridge carries westbound traffic over State Route 127 (Hamilton Avenue).

The bridge is a 3-span, continuous rolled steel beam bridge with a reinforced concrete deck and integral abutments. This particular bridge was selected, in part, because the structural form utilized is representative of a large portion of in-service structures currently contained within Ohio’s bridge inventory. Detailed examination of the design and construction plans for the bridge was required in order to develop a monitoring system that would properly characterize the structure’s response to a large number of construction and service related inputs. The size, anticipated function, and detailing of the main bridge components must be clearly visualized before an effective monitoring scheme can be developed. A three-dimensional CAD model of the structure, shown below, was developed to assist with the monitoring system design. Although the benefits derived from a three-dimensional CAD model of the bridge may seem trivial, this model provided the researchers with pragmatic visualization of:

• The geometry and relative scale of the various components of the finished structure.

• The connectivity between the principal and secondary structural components.

• Sequencing of construction events.

• Physical obstacles or obstructions to placing sensors in analytically determined locations.

• Feasible location and placement of protective infrastructure for the monitoring system.

CAD Rendering of the HAM-126 Bridge - Top View

CAD Rendering of the HAM-126 Bridge - Bottom View

The general design characteristics of the test specimen are outlined in the chart below. The bridge was designed in accordance with the "Standard Specifications for Highway Bridges" adopted by the American Association of State Highway and Transportation Officials (AASHTO), 1992 and the Ohio "Supplement" to those specifications.

The plan and elevation views of the bridge, as given in the design plans, are shown below. The bridge, designated HAM-126-0881L, has an overall length of 138.97 ft and is skewed just under 6 degrees. It has a center span length of 88.47 ft and two end span lengths of 40.21 ft and 40.30 ft. The width of the bridge deck is 40 ft measured between the parapet toes. The deck accommodates two lanes of traffic and a shoulder. The deck is a monolithic concrete wearing surface with a normal crown super-elevation. The bridge was designed using HS20-44 and alternate military loading cases.

Framing Plan View of the HAM-126 Bridge

Cross Section View of the HAM-126 Bridge - Bottom View

The steel framing system for the bridge has five lines of beams and intermediate angle crossframes. The beams are constructed of A572-50 grade steel, which has minimum yield strength of 50,000 psi. The beam lines are spaced on 9.75 ft centers. The ratio of the end spans lengths to the intermediate span length is about 0.5, which was dictated by clearance requirements for the roadway below the bridge. An interesting aspect of the design is that the beams are designed as composite with the reinforced concrete deck only between the field splices. This was done because the end spans are very short in relation to the intermediate span and are dominated by negative moment under uniform loading. The beams were sized according to the maximum negative moment at the pier locations (HS20-44 lane load governs) and the maximum positive moment at the middle of the intermediate span (HS20-44 truck load governs).

The endspan beams for the bridge are W36x194 rolled steel sections and the intermediate span beams are W36x182 rolled steel sections. The different sections are connected using bolted field splices located 15 ft from each pier. The bolts used for the splices are 1 in diameter A325 high strength bolts. The W36x182 sections are made composite with the concrete deck by using 7/8 in diameter by 5 in long end welded shear studs (Figure 2.12). Intermediate crossframes consisting of 3 x 3 x 5/16 steel angles are field welded perpendicular to the beams at 14 ft intervals.

The minimum thickness of the deck is 8.75 in. Reinforcing steel clearances are 2.5 in at the top of the deck and 1 in at the bottom. The deck has concrete haunches with a design thickness of 2 in to encase the edges of the top flange. The haunches are tapered to the original deck thickness over a distance that varies between 9 in and 12 in. Reinforced concrete parapets are located on the cantilevered deck overhangs. The concrete specified for the deck is Class S (4500-psi design compressive strength) and the specified reinforcing bars are epoxy coated Grade 60 steel.