Question: Which bridge in Seattle has a superstructure and substructure that are rigidly connected to act as a continuous unit ?

text: List of bridges in Seattle
List of bridges
Key : Year opened * : Listed in the National Register of Historic Places [ 15 ] † : Listed as a city landmark [ 16 ]
The city of Seattle, Washington, United States, has multiple bridges that are significant due to their function, historical status, or engineering. Bridges are needed to cross the city's waterways and hilly topography. Twelve bridges have been granted historical status by the city, federal government, or both. Seattle also has some of the only permanent floating pontoon bridges in the world. Original crossings over Seattle's mudflats were typically supported by timber piles. Lake Washington and Puget Sound are to the east and west of the city, respectively. They connect via a series of canals and Lake Union that are collectively known as the Lake Washington Ship Canal. The four double-leaf bascule bridges crossing the Ship Canal are the oldest still used in the city, having opened between 1917 and 1930. The easternmost - the Montlake and University bridges - connect neighborhoods south of the canal to the University District. The Fremont Bridge crosses the center of the canal and is one of the most often raised drawbridges in the world due to its clearance over the water of only 30 feet (9.1 m). The westernmost crossing of the ship canal is the Ballard Bridge. Floating bridges carry Interstate 90 and State Route 520 across Lake Washington to the Eastside suburbs.
Name ( Alternative names in parenthesis ) Year opened Type Length Spans Carries
Arboretum Sewer Trestle c. 1913*† Arch 180 ft ( 55 m ) Lake Washington Boulevard E Sewer and a footpath
Ballard Bridge ( 15th Avenue Bridge ) 1917* Bascule 2,854 ft ( 870 m ) Salmon Bay 15th Avenue NW
Cowen Park Bridge 1936*† Arch 358 ft ( 109 m ) A ravine in Cowen Park 15th Avenue NE
First Avenue South Bridge 1956 Bascule 300 ft ( 91 m ) Duwamish River State Route 99
Fremont Bridge ( Fremont Avenue Bridge ) 1917*† Bascule 242 ft ( 74 m ) Fremont Cut Road connecting Fremont Avenue N and 4th Avenue N
George Washington Memorial Bridge ( Aurora Bridge ) 1932*† Cantilever and truss 2,945 ft ( 898 m ) Lake Union State Route 99
Homer M. Hadley Memorial Bridge ( Third Lake Washington Bridge ) 1989 Floating pontoon 5,811 ft ( 1,771 m ) Lake Washington Interstate 90
Jeanette Williams Memorial Bridge ( West Seattle Bridge ) 1984 Cantilever 2,607 ft ( 705 m ) Duwamish River Road connecting Fauntleroy Way SW and the Spokane Street Viaduct
Jose Rizal Bridge ( 12th Avenue South Bridge ) 1911* Truss arch 420 ft ( 130 m ) S Dearborn Street and Interstate 90 12th Avenue S and Interstate 90
Lacey V. Murrow Memorial Bridge 1993 Floating pontoon 6,620 ft ( 2,020 m ) Lake Washington Interstate 90
Magnolia Bridge 1930 Truss 3,600 ft ( 1097 m ) Filled-in tidelands of Smith Cove W Garfield Street
Montlake Bridge 1925*† Bascule 344 ft ( 105 m ) Lake Washington Ship Canal State Route 513
North Queen Anne Drive Bridge 1936† Arch 238 ft ( 73 m ) Wolf Creek N Queen Anne Drive
Salmon Bay Bridge 1914† Bascule and truss 200 ft ( 61 m ) Salmon Bay BNSF Railway
Ship Canal Bridge 1962 Truss 4,429 ft ( 1,350 m ) Portage Bay Interstate 5
Schmitz Park Bridge 1936*† Rigid frame 175 ft ( 53 m ) A ravine in Schmitz Park SW Admiral Way
Spokane Street Bridge 1991 Swing 480 ft ( 150 m ) Duwamish River SW Spokane Street
SR 520 Albert D. Rosellini Evergreen Point Floating Bridge ( Evergreen Point Floating Bridge , 520 Bridge ) 2016 Floating pontoon 7,708 ft ( 2,350 m ) Lake Washington State Route 520
20th Avenue NE Bridge ( Ravenna Park Bridge ) 1913*† Arch 354 ft ( 108 m ) A ravine in Ravenna Park 20th Avenue NE ( pedestrian access only )
University Bridge 1919* Bascule 218 ft ( 66 m ) Portage Bay Eastlake Avenue NE