opportunities to explain technical concepts, receive input and propose solutions for the committee’s approval. This blended concept devel- opment and outreach process was critical in building advocacy and creating excitement for the project. “It didn’t happen overnight, but at each meeting, we would show genu- ine regard for what the public had to say about the design,” Molas said. “They had a lot of really good ideas and provided a valuable local perspective that deserved our attention.” Designers introduced refinements to the plan at each meeting, incorpo- rating what had been discussed at the previous meeting. Even when it was a relatively modest but important suggestion – such as the instal- lation of charging stations to accommodate the elderly population who use battery-powered scooters to cross the bridge – it was given serious attention and became an integral part of the plan. PAC members not only helped the study team better understand com- munity concerns and priorities, but also served as a critical link back to their constituents, sharing the progress of the study and receiving valu- able feedback from the public. Ultimately, their endorsement of the bridge design was what turned public enthusiasm in favor of the project. “The public gradually took ownership of the overall design,” Molas said. “They helped establish the vision, and the engineers and design- ers worked with the client to find ways to make it work.” That idea of ownership extended further than either Moon or Molas an- ticipated, as the committee started viewing the project from the client’s perspective, sometimes suggesting that certain aspects of the project might be unnecessary or too expensive. Historic Design – Modern Construction Techniques Much of the community saw the old bascule bridge as an important part of their personal history. It was always there; always a part of their life. It couldn’t just be replaced with a standard bridge. And to properly honor Volusia County veterans, it should be something special. “As it was going to be a bridge to honor America’s military veterans, we gathered input from veterans on the committee throughout the de- sign process, and they were favoring an arch bridge design that was common in the 1920s and 1930s that looked powerful and formidable – which they saw as a symbol of the strength and perseverance of mili- tary veterans,” Moon said. Incorporating a non-traditional design ran the risk of significantly in- creasing the cost of the project. Arch bridges of this type typically used extensive and costly cast-in-place (CIP) construction. So the complex bridge design team, led by WSP’s project engineer-of-records Victor Ryzhikov, P.E; and Christopher Vanek, P.E., developed an innovative concept to maximize the use of pre-cast components, including all arch and superstructure components, “A CIP approach was simply not practical today, so we came up with an evolutionary design that precast those segments in the controlled
environment of a casting yard, and then brought them to be assembled at the site, sort of like Lego blocks,” Molas said. The bridge is composed of a pure concrete open spandrel arch bridge with a main span through-deck arch over the waterway. During con- struction, the beams and main span arches were hoisted into position by cranes, then closure pours were used to connect all the elements together. It was these connection points, and the order of their assembly, that Ryzhikov and Vanek focused much of their design efforts towards. The connections must be small, compact, but incredibly rigid and reason- ably easy to assemble on site. Although the open spandrel approach spans were constructed only with closure pours, the longer main span through arch required a combination of longitudinal and transverse post-tensioning to create a rigid frame, that could be supported via PT hanger bars over the channel. As part of the design process, 3D BIM was utilized to verify construc- tability and accuracy of the complex connection points. The 3D draw- ings also aided in plans review and were ultimately used by the CEI and contractor for reference during construction. Pedestrian Friendly Design The design also achieved another PAC objective – lowering the overall profile of the bridge. “The arch was a simple way to carry the weight of the bridge from above rather than below, creating a thinner profile over the channel while still meeting the minimum height requirement,” Molas said. “The arch allowed us to create a much shallower deck than conventional designs would, lowering the roadway profile at midspan significantly compared to the nearby segmental bridge that has the same naviga-
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csengineermag.com
july 2020
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