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Design-Construction Feature Segmental Design of The Harbour Island People Mover Roy L. Eriksson Project Engineer LEAP Associates International, Inc. Tampa, Florida Stephen Zendegui Project Manager LEAP Associates International, Inc. Tampa, Florida he Harbour Island People Mover is track basis to Misener Marine Con- Tan elevated system (see Fig. 1) struction, Inc. of Tampa. After estab- which links the mainland of downtown lishing the shape and design param- Tampa with Harbour Island, a billion eters for the guideway structure, Mise- dollar commercial development. The ner subcontracted with LEAP Asso- People Mover is actually an automated ciates International, Inc. to design and vehicle which transports pedestrians to produce the shop drawings for the pre- and from the development. Visitors to cast prestressed portion of the project. the island can park in the multilevel ga- The fabrication of the prestressed ele- rage at the mainland terminal (see Fig. ments was subcontracted to Florida Pre- 2) and conveniently ride this "horizontal stressed Concrete and the vehicle oper- elevator" to Harbour Island. ational system was designed and The $2.8 million contract for the proj- supplied by Otis Elevator Company, ect was awarded on a design/build fast- Transportation Technology Division. The scope of work performed by 'Currently, Vice President, Library of Engineering Ap- LEAP was divided into two parts: a seg- plications Programs, Inc. mental portion and the balance of the 38 !A1 a Describes the design and construction features of the precast prestressed segmental span of the Harbour Island People Mover, part of a billion dollar commercial development project in Tampa, Florida. PCI JOURNALJJuly-August 1985 39 Fig. 1. Segmental span of the Harbour Island People Mover which links the mainland of downtown Tampa with Harbour Island, a billion dollar commercial development. project. The two-piece segmental por- Structural System tion is the center span of a three-span The main structural system of the continuous guideway which spans the people mover consists of a concrete Crosstown Expressway (see Fig. 3). The guideway composed of precast pre- balance of the project, which actually stressed voided box beams supported by constitutes the bulk of the project, con- cast-in-place concrete piers founded on sists of a guideway supported by single drilled shafts. A total of 34 spans were precast prestressed concrete box beams used which were grouped into 12 units grouped into units made continuous for of one, two, three, and four spans which live loads. are continuous for live load. The total The focus of this article is on the length of the project is roughly 2500 ft analysis and design of the precast seg- (762 m). mental portion of the project. It was this The spans of the system are basically part that proved to he the most interest- linear with the stationing running adja- ing and challenging part with regard to cent to and along the centerline of LEAPS involvement in the project. Franklin Street (see Fig. 3). Two groups First, the basic layout of the entire of two cable-driven passenger cars system will be discussed including traverse the system on cushions of air, some of the reasons for selecting a seg- each group traveling in the opposite mental design. Then, the highlights of direction with respect to the other. the analysis and design techniques will Most of the guideway of the system is be discussed which include the loads a single track. However, at the bypass considered, the analysis tools used, and region (see Fig. 3), where the cars pass the actual design methodology. Some each other enroute to their respective unique aspects involved in the produc- terminus points, there is a double lane. tion of the precast prestressed compo- This region is characterized by a double nents also will he described. Finally, a box beam arrangement whereas the few of the special problems encountered other areas have only one beam per during construction, to which interest- span. ing solutions were found, will be pre- A section taken near midspan of the sented. segmental span revealing the compo- 40 Fig. 2. The Fort Brooke parking garage is at the mainland terminus of the People Mover. PCI JOURNALJJuly-August 1985 41 nent parts of the system is shown in Fig. The 48 x 54 in. (1219 x 1372 mm) 4. The four basic parts are the box beam, voided box beam has end regions which deck, flying surface, and rails. For pur- are solid for approximately 5 ft 7 in. (1.71 poses of comparison, a typical section m) at each end. Two intermediate dia- through a nonsegmental part of the proj- phragms, located at approximately third ect is shown in Fig, 5. Note that the points, were used in each of the 70-ft sidewalls of the segmental box were (21.3 m) segments which make up the thickened to accommodate the post- segmental span. The thicknesses of the tensioning ducts. end regions and the intermediate dia- HOTEL TAMPA FINANCIAL Dr CELJR LJ n f "TAMPA ETRIAN J CITY CENTER HOPPING MALL - BUILDING SHUTTLE STATION MULTI -LEVEL [j DE PARKING GARAGE / L.^ CROSSTOWN SEGMENTAL SPAN EXPRESSWAY BYPASS BYPASS GARRISON CHANNEL SHUTTLE STATION HARBOUR ISLAND Fig. 3. Sketch showing major areas of the project and the locations of the main landmarks in the vicinity. 42 Fig. 4. Section through midspan of the segmental portion reveals the post-tensioning ducts and prestressed strands. phragrns were controlled by the shape designed with 5000 psi (34.5 MPa) con- and placement of styrofoam voids (see crete. Fig. 6). The rails, located at each extreme A 28-day concrete strength of 5000 psi edge of the deck, have rectangular cross (34.5 MPa) was required in the design of sections measuring 5 in. x 2 ft 10 in. the boxes. However, cylinder tests (127 mm x 0.86 m). The flying surface showed strengths consistently well measures 8 ft x 4 in. (2.44 m x 102 mm) above this value throughout the project. and, as with the deck, is centered on the The deck is 6 in. (152 mm) thick box beam. directly above the box (plus a build-up of varying thickness) and tapers to about Why Segmental Design? 5 in. (127 mm) at the outer edges. The nominal width of the deck is 12 ft (3.66 Length was one of the main design m) and is centered on the vertical axis constraints which affected the three op- through the centroid of the box. Small tions considered for the span over the keyways were formed near the edges on Crosstown Expressway. The Express- the upper surface of the deck where the way Authority prohibited the placement rails are joined. The deck as well as the of a permanent bent between the road- other cast-in-place components were ways of the expressway. This meant that PC JOURNAL/July-August 1985 43 Fig. 5. Section through nonsegmental portion shows thinner side walls in these spans. the span length had to be a minimum of without changing to a larger box cross about 140 ft (42.7 m), section. Moreover, it would have been The first of the possibilities consid- very difficult to transport and erect a ered was a steel box section. Designing single 140-ft (42.7 m) girder. a steel section to span 140 ft (42.7 m) The solution adopted, which was would have been possible. However, suggested by LEAP, was to use a post- since a high premium was placed on ar- tensioned segmental design. Two 70-ft chitectural impressions, this option was (21.3 m) segments could be easily han- quickly ruled out since it would not dled and once erected on a temporary have blended very well with the con- bent, could be post-tensioned together. crete sections used in the balance of the By using bundled strands in ducts, a project. sufficient eccentricity at midspan could Also considered was the same one- be achieved to satisfy design require- piece design used on the rest of the ments. A box section with the same ex- project. Parallel strand patterns were terior dimensions as the other boxes used in these cases, but this was not could be used and so the architectural possible for this long of a span because a requirements were easily satisfied with suitable strand pattern could not be this option. Additionally, the mainte- found to satisfy both service conditions nance requirements would be lower and ultimate strength requirements than for steel. 44 Fig. 6. Reinforcing scheme of a typical beam prior to the side forms being lifted into place. Design Aspects sequence of construction of the seg- mental span, there was actually one The loads acting on various parts of other component load which acted on the overall system were grouped into the segmental unit. This was the load five general categories: vehicle loads, which was placed on the structure to dead loads, wind, thermal forces, and simulate the removal of the shoring. A shrinkage and creep forces. These loads summary of the construction procedure were combined into three critical load which gave rise to this other load corn- cases. ponent follows. Case I consisted of the car, dead, The two segments were first erected shrinkage and creep, and thermal loads. on the permanent supports and the tem- Case II consisted of the same loads as porary bent and then post-tensioned to- Case I except that full wind load was gether (see Figs. 7 and 8). This caused substituted for the car load plus all loads both pieces — now acting as one unit - were reduced by 25 percent. Case III to lift up off the temporary bent ap- consisted of car, dead, partial wind, proximately V in.

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