Photo Credit: Alex Mead
This is the Portage Lake Lift Bridge, officially the Houghton–Hancock Bridge, in Houghton, Michigan. This bridge connects the Upper Peninsula of Michigan to the Keweenaw Peninsula, which today is technically the Keweenaw Island due to a man made shipping canal. The lift bridge is the widest and heaviest double-decked lift bridge in the world, capable of elevating to a water clearance height of 100 feet!
Photo Credit: Alex Mead
This is the I-94, Telegraph Road Bridge near Detroit, Michigan. This seemly out of place bridge is needed to span over Telegraph road to allow for unobstructed traffic flow beneath I-94. This bridge uses a combination of steel arches and tension cables to carry the load of the deck and passing traffic. The road deck takes load to the cables, which are hung from the steel arches. These steel arches then finish the load path by bringing the load to the ground. If you look on the right side of the picture, the top of the foundation of the bridge can be seen where the blue arch contacts the ground.
Photo Credit: Karl Jansen
Pictured here is the Mackinaw Bridge, which connects the Upper Peninsula of Michigan to the Lower Peninsula. This suspension bridge was finished in 1957, boasting a length of 26,372 feet (4.99 miles) and a longest span of 3,800 feet. Suspension bridges are unique in the way the loads of the bridge are transferred to the ground. The cables of a suspension bridge work in tension, carrying the loads to the two towers which work in compression against the foundations on the earth. The cable ends are then secured in massive blocks of concrete that hold the tension in the cables completing the load path.
Photo Credit: Alex Mead
This is a soldier pile and railroad tie retaining wall. These types of walls are common due to their relative ease of construction and the availability of materials. Simply place the vertical members, brown tubes in this case, and stack the railroad ties behind. Then, back fill can be placed behind the wall. One major problem with this wall, however, is the placing of the railroad ties. All joins should be staggered by many inches and secured with large spikes. As you can see on the far right this is not done, and greatly reduces the strength of the wall.
Photo Credit: Alex Mead
This is a stack of wood I-Joists used to span long distances between supports in a wood frame structure. Wood I-Joists are typically made of solid wood flanges, the two fat outer parts top and bottom, and an OSB (oriented strand board) web, the skinny center part. I-Joists like this are advantages because they carry load more efficiently than a comparable solid wood member, are lighter than a comparable solid wood member, and can be ordered in spans that would be prohibitively expensive to for solid wood members. This job is using wood I-Joists to prop up form work for a large concrete job, and is thus going to make full use of the dozens of I-Joists bundled here.
Photo Credit: Alex Mead
The parking structure above is a perfect example of earthquake retrofitting a structure. The crisscrossed red members on the front of the structure were added after the completion of the building to increase the strength in the event of an earthquake. If you look closely the connections of the frame to the ground are pin connections. These pin connections literally are large plates with simple holes connected by a rod. These pin connections allow for rotation of the joint, but do not allow the frame to move up, down, or side to side apart from ground motion.
Photo Credit: Alex Mead
This is part of the structural testing lab at the University of Illinois, one of the premier structural labs in the world. The blue box is a particular piece of equipment capable of applying forces in all three cardinal directions as well as moments in all three cardinal directions. Experiments performed with this machine allow engineers to control all the aspects of the motion and load a structural element is undergoing. Seen here is a pier being tested for post seismic repair adequacy.
Photo Credit: Alex Mead
Featured above is a classic single span concrete bridge over a small river. The river is a minor branch of the Muskegon River in Muskegon, Michigan close to where it enters Muskegon Lake. Over the course of the lumber boom of the 1800’s this river carried billions of board feet of lumber from the interior regions of the state to the saw mills on the coast of Lake Michigan. These logs were in turn sawed into lumber and used to build homes, buildings, and other timber structures.
Photo Credit: Alex Mead
Seen here is a railroad bridge that crosses a busy highway in Muskegon, Michigan. Although seldom thought about by the general public, without bridges like this one the transportation infrastructure that makes up American would be much less efficient. Image having to stop at an intersection like this one for a train while driving 70 MPH on the freeway!