Design-Build of the Foothills Parkway Bridge in Tennessee
Corven Engineering, Inc. is a national leader in the design, construction engineering, inspection and rehabilitation of prestressed concrete bridges. The firm has special capabilities with regard to post-tensioned concrete bridges, with an emphasis on precast and cast-in-place segmental concrete bridges.
This IDS client provides technically appropriate and high quality services from concept, to completion, and throughout the life of a bridge.
John Corven (Principal of the firm) says: “Our goal is to optimize human and natural resources through designs that embrace form following function with inherently high durability. We organize our work in four core areas: Design, Construction Engineering, Inspection and Rehabilitation, and Technology Development.”
The engineers at Corven Engineering have been using the Bridge Designer software for over 20 years. They are unique in that they both design new bridges and provide construction engineering to contractors who are building post-tensioned concrete bridges. Straightforward model definitions, tendon definitions using simple geometric commands, time-dependent construction analyses, automated live load generation, and limit state combinations speed the design process.
For precast segmental bridges, long-term bridge deflections are combined with three-dimensional segment coordinates to provide daily set-ups for segment casting. Corven Engineering uses IDS’s the MC3D geometry control software for short-cell match-casting on many of their segmental bridge projects to help automate this procedure.
The following Corven Engineering project was developed using the Bridge Designer software:
FOOTHILLS PARKWAY BRIDGE NO. 2
Blount County, Tennessee
Delivery Method: Design-Build
Owner: National Park Service
Contractor: Bell & Associates Construction
Client: Bell & Associates Construction
Date of Services: January 2010 to June 2013
Total Construction Cost: $25 million
Located in a scenic, environmentally sensitive area with limited access, this bridge the last significant bridge needed to complete the 1.6-mile “missing link” for the Foothills Parkway along the Blount and Sevier County line near the Great Smoky Mountain National Park in Tennessee.
The precast segmental concrete bridge is 790′ long with a maximum span length of 180′. The alignment consists of a reverse curve with radii as small as 262′. The precast superstructure segments are 36′-10″ wide and 8′-8″ long and are prefabricated at a local precasting plant. Precast hollow segmental concrete box pier columns are used for the substructure. To limit the impact to the environment, the precast segments are erected in balanced cantilever “top down” using a specially designed straddle carrier mounted on a temporary work bridge.
Corven Engineering was the prime consultant for the project, and designer and Engineer of Record for this precast segmental concrete bridge design. Corven Engineering used BD2 and BD3 to analyze and design the superstructure for this highly curved bridge. During construction, Corven Engineering provided construction engineering services to the design/build team. In addition to integrated shop drawings, construction analyses, and post-tensioning stressing data, Corven Engineering used MC3D to provide daily geometry information for segment casting.
Corven engineers first created a 2D version of the model for longitudinal analysis and sizing of the post-tensioning layout. This first model was also used to evaluate long term stress redistributions (creep & shrinkage, and steel relaxation) and final deflections in order to obtain casting curves for geometry control.
The 2D model was also used for live loads and comprehensive check of all service load conditions and stress combinations.
Engineers then used this 2D model to create an accurate 3D version of the model including top slab widening in order to analyze transverse effects and t orsion. Once a 2D model is created, the Bridge Designer User Interface and the Analysis Engine provide the tools to quickly generate a 3D model. Corven used this feature to create accurate 3D modeling of the structure as well as the Post-Tensioning tendons with respect to the structure horizontal curvature or width variations.
John Corven says: once you have created and fully tested all construction stages and the 2D model is satisfactory, you can then quickly proceed with the analysis of the 3D model, and all construction stages, element numberings and Bridge Designer construction command syntax is directly and automatically transferred to 3D.
In addition the transverse can be accurately modeled for exact mechanical cross-section properties as well as exact geometry and topology for non-linear thermal gradient evaluation.
A careful review of time-dependent effects on the 3D model showed that the 2D analysis was sufficient to fully analyze all construction stages and longitudinal forces.