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<p>The Abraham Lincoln Bridge is a 3-tower cable-stayed bridge connecting Louisville, Kentucky to Jeffersonville, Indiana. The design included an innovative foundation layout, cable-stayed detailing that simplified construction, and probabilistic 100 year service life design. The design contemplated the construction approach preferred by the Design Build contractor. This collaborative approach between the designer and contractor was critical to achieving efficient design elements such as the anchor box, anchorages at the deck level, and tie downs. Yet, despite careful planning, challenges presented themselves during construction, such as deficiencies of concrete materials and difficulties during shaft construction. This paper takes an in depth look at these challenges that arose during construction as we endeavour to share the knowledge gained, not from what went well, but rather from our collective failures.</p>

<p>KYTC's project requirements and the design/build team's drive to reduce cost and shorten construction schedule led to the development of a three-tower cable-stayed bridge with a flexible foundation system in the longitudinal direction. Working through the site specific challenges and external constraints the design team was able to deliver an affordable solution that could be built in a short period of time.</p> <p>The key measures taken by the design build team to address these unique challenges included the following:</p><ul> <li><p>The design/build team worked effectively with the owner's engineer to develop project specific design criteria to address the unique behaviour of the flexible system and to provide overall safety margin for the structural system consistent with the project requirements specified in the RFP;</p></li> <li><p>At the start of the final design, the designer identified the key system behaviour that needed to be properly captured not only for the completed structure but also for the critical erection stages. Appropriate computer models were developed to ensure such behaviour was properly modelled. Sensitivity of the key behaviour to the design assumptions including construction tolerances were also properly incorporated;</p></li> <li><p>At the early design stages, the designer and the contractor had extensive discussions and reached a consensus on the appropriate restrictions that are required in placement of superstructure steelwork and precast deck panels to limit the erection loads on the flexible foundations;</p></li> <li><p>To comply with the contractor's very aggressive construction schedule, the designer had to complete the design of the first tower before all studies and investigations (such as wind tunnel and technique shat load tests) had been completed. The designer made some reasonably conservative assumptions in design of the first tower based on the available information and prior experience. The first tower design was then confirmed, and design of the other towers, anchor piers and superstructure was progressively optimized when findings from the studies and investigations became available.</p></li></ul><p>The end result is a durable structure that will grace the Louisville Skyline for years to come.</p>

A 4 1/2-in. API full-hole, tool-joint pin is stress-analyzed photoelastically over a range of standoffs. A three-dimensional plastic model is loaded to different values of makeup torque. At each torque a range of cyclic bending loads and a range of cyclic tensile loads are simulated. The results show that makeup torques must be raised for extreme hand-tight, shoulder-gap standoffs if a given pin tension is to be maintained. Maximum static root stresses are shown to be nearly independent of standoff if a constant pin tension is maintained. Further analysis indicates that the fluctuating pin-root stresses are also nearly independent of standoff if complete relieving of the shoulder compression loads is prevented. These considerations indicate that standoff has a negligible effect on the fatigue life of a tool-joint pin if relieving of the joint shoulders under operating conditions is prevented.

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