Research Project: Fred Hartman Bridge The Fred Hartman Bridge is truly a magnificent engineering accomplishment, not to mention a beautiful structure. During the mid 1980s the existing tunnel underneath the Houston Ship Channel in Texas, America, could not cope with the increased volume of road traffic and had to be replaced by a bridge. This large amount of traffic required four lanes with full shoulders in the each direction. A detailed investigation resulted in two independent beams as the most economic solution. The busy ship traffic between the Gulf of Mexico and Houston Harbor required a navigational clearance of 53 m. The towers were protected against ship collision by locating one of them on shore and the other one in shallow water and surrounding it with an artificial island. The project was awarded for $ 91.3 and the bridge was designed in accordance with American Association of State Highway and Transportation Officials and international codes. All structural parts were designed in service limit state and ultimate limit state. The concrete for the roadway slab was C 50 standard and for the tower C 42, the reinforcement had a yield strength of 420 N/mm2 and the structural steel ultimate strength of 520 N/mm2. The high winds experienced in the area were the primary concern of engineers especially since the Fred Hartman is part of a main route for hurricane evacuations. The aesthetically handsome result, a double-diamond tower configuration, creates “truss-action” for greater lateral stiffness to resist inevitable hurricane-force winds. The tower and deck configurations had never been tried in real world applications. As noted, technically, they deliver a "truss ac-tion" for greater lateral stiffness and work in tandem with the inward-sloping cables to torsionally resist unbalanced dynamic loadings imposed upon the decks. Floating foundations were used in the alluvial soils around the Houston Ship Channel, where rock is found only in great depth. They consist of 130 Nos, 50 cm square and 40 m long pre-stressed driven piles. Load tests indicated a bearing capacity of 200 t during service. The 3.6 m deep pile cap was reinforced with several layers of bars with 40 mm. The tower legs were built by free cantilevering with jumping forms in 4.5 m sections. For the first tower a formwork truss was used covering its full width, on which two cranes were running. The relocating of the large steel truss proved to be difficult. Therefore, smaller individual jumping forms for each tower leg were used for the second tower. All tower legs had wall thicknesses of 305 mm and two layers of reinforcement at 150 m. The forms for the cable anchorage area were built in sections on the ground with the steel pipes precisely located. The steel grids for the beams were for economic reasons fabricated in South Africa. After shipment, the final corrosion protection was applied in the pre-assembly yard and the grid sections were then test bolted and surveyed. The first short starter elements of the beam in the tower axis were lifted with tower cranes. On them the derricks were installed with which all other beam elements were lifted. Above water the grid elements were delivered from the pre-assembly yard by barges and lifted to the beam by the derricks. Since no welding on site is acceptable in the USA even today, the main girders were connected with cover plates and high-strength bolts. The precast slabs were also delivered by barges and lifted up by the derricks. The precast slabs span between the cross girders. The stay cables comprise 20–61 strands 15 mm with wedge anchorages at both ends. They are protected by thick-walled PE pipes and were grouted after installation. Wrapping of the PE pipes with UV-resistant self-adhesive yellow PVF tape reduces the temperature changes of the stay cables from direct solar radiation and improved the aesthetics of the bridge. The tower legs were built by free cantilevering with jumping forms in 4.5 m sections. For the first tower a formwork truss was used covering its full width, on which two cranes were running. The relocating of the large steel truss proved to be difficult. Therefore, smaller individual jumping forms for each tower leg were used for the second tower. All tower legs had wall thicknesses of 305 mm and two layers of reinforcement at 150 m. At the intersection of the inner tower legs at beam level 220, reinforcement bars 25 mm from each side had to cross. This reinforcement was preassembled in a cage with a weight of 18 t on the ground and then lifted. The bridge, named for Fred Hartman (1908–1991), the editor and publisher of the Baytown Sun from 1950 to 1974, is the longest cable-stayed bridge in Texas and is the seventy-seventh largest bridge in the world. The construction cost of the bridge was $117 million. When the Bridge opened on 27th September 1995, it eliminated a restrictive tunnel under the Houston Ship Channel and alleviated years of stress for countless frustrated drivers. It was also an aesthetic success, providing a new and exciting signature span for Texas. Today, it is one of the world’s most well-known cable-stayed bridges, accommodating 200,000 vehicles per day. They developed the unique, award-winning double-diamond towers that stand as tall as a 45 story building yet efficiently resist hurricane winds. The cable-stayed main span unit is 2,475 feet long; the length of eight football fields and allows eight lanes of traffic to smoothly flow 175 feet over the Houston Ship Channel. Vision, determination, form, purpose... When combined these qualities creates works of art, monuments and engineering wonders.