The Ada Covered Bridge is a 125-foot (38 m) span Brown truss covered bridge erected in 1867 in Ada , Michigan , United States. Carrying Bronson Street across the Thornapple River , it is located just south of where the Thornapple enters the Grand River , in turn just south of M-21 . It is listed on the National Register of Historic Places .
11-460: The bridge uses the Brown truss system, consisting of diagonal compression beams and almost vertical tension members (slanting in at the top toward the center of the span), patented by Josiah Brown Jr. of Buffalo, New York, in 1857. A timber bearing Brown's name was discovered during repair work carried out in 1913. The bridge is 125 feet (38 m) long, and originally rested on wooden pilings. As
22-411: A historical marker posted at the bridge, "it is said that farmers used to drive wagons loaded with stones onto the bridge during high water to hold it to the foundation." Repair work was carried out in 1913 to modify the trusses, and replace the timber abutments with reinforced concrete. The bridge was part of an important artery into the village of Ada until 1930, when the main highway was rerouted and
33-474: A - a (gross area of the member) is 8 x ½ = 4 in However, the area at section b - b (net area) is (8 – 2 x 7/8) x ½ = 3.12 knowing that the higher stress is located at section b - b due to its smaller area. To design tension members, it is important to analyse how the member would fail under both yielding (excessive deformation) and fracture, which are considered the limit states. The limit state that produces
44-652: A concrete bridge built further down the Thornapple River. At that time the bridge was closed to automobile traffic, reverting to pedestrian use only. In 1941 the Kent County Road Commission and the Works Progress Administration made extensive restorations, re-roofing the bridge with new protective creosote shingles and replacing many of its decayed underlying supports with new beams. The Road Commission purchased
55-602: A nearby barn to supply wood for replacement of badly deteriorated elements. The bridge was listed with the Michigan State Register on May 9, 1969, and with the National Register on February 16, 1970. It was awarded a Michigan Historical Marker (site L0075) on August 28, 1974. It is one of four existing publicly owned covered bridges in Michigan. In 1979 the roof collapsed due to heavy snow, and
66-590: Is now open only to pedestrian traffic and connects the Village of Ada on one side of the Thornapple River with a park on the other side. It is maintained by the Kent County Park system. Tension member Tension members are structural elements that are subjected to axial tensile forces . Examples of tension members are bracing for buildings and bridges , truss members, and cables in suspended roof systems. In an axially loaded tension member,
77-426: Is typical for covered bridges, its gabled roof is covered with creosote shingles. The Michigan State Legislature authorised Ada Township to borrow up to $ 3,000 for building or maintaining bridges in the area. Construction of this bridge, also known as the "Bradfield Bridge" was carried out in 1867 by William Holmes. Prior to construction of the upstream dam, the Thornapple River was prone to flooding. According to
88-507: The bridge was restored using funds raised by private donations. Shortly after the repairs were finished, the bridge was completely destroyed by fire. The citizens again rallied, this time with the help of the Amway corporation , headquartered in Ada, and rebuilt it once again. The replica bridge, now resting on concrete abutments, is 14 feet (4.3 m) wide and 125 feet (38 m) long. The bridge
99-465: The central problem of designing a member is to find a cross section for which the required strength doesn't exceed the available strength: P u < ¢ P n where P u is the sum of the factored loads. to prevent yielding 0.90 F y A g > P u to avoid fracture, 0.75 F u A e > P u therefore, the design must consider the loads applied to this member, the design forces acting on this member (M u , P u , and V u ) and
110-427: The smallest design strength is considered the controlling limit state. It also prevents the structure from failure. Using American Institute of Steel Construction standards, the ultimate load on a structure can be calculated from one of the following combination: 1.4 D 1.2 D + 1.6 L + 0.5 (L r or S) 1.2 D + 1.6 (L r or S) + (0.5 L or 0.8 W) 1.2 D + 1.6 W + 0.5 L + 0.5 (L r or S) 0.9 D + 1.6 W L= 14
121-484: The stress is given by: F = P/A where P is the magnitude of the load and A is the cross-sectional area. The stress given by this equation is exact, knowing that the cross section is not adjacent to the point of application of the load nor having holes for bolts or other discontinuities. For example, given an 8 x 11.5 plate that is used as a tension member (section a-a) and is connected to a gusset plate with two 7/8-inch-diameter bolts (section b-b): The area at section
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