The following documentation explains the structural design procedures performed. The design was followed in according to AASHTO specifications. Design analysis was implemented from "Design of Modern Highway Bridges- by Narendra Taly (Chapters 6 and 7). Information gathered for design was obtained from Banner and Associates, Inc. in Brookings, SD and South Dakota Concrete Products. Assistance with design procedures was from Dr. Nadim Wehbe, SDSU Civil and Environmental Engineering Structures professor, and Doug Wessels, Structural Engineer at Banner and Associates, Inc.
Expansion.
The replacement bridge was expanded from the original bridge according to the "South Dakota Bridge System Code Manual - 1998 Edition- obtained from the SDDOT. The replacement bridge was then extended to span 120 ft. as compared to the original length of 90 ft. All design of the bridge girders and deck is based on the 120 ft expansion.
Design Traffic.
The design truck loading for this bridge is for an HS20-44 and an estimated daily traffic volume of 100 vehicles per day. .
Bridge Type.
The design of this structure is for a continuous span, prestressed concrete I-Beam girder bridge with a continuous reinforced concrete deck and a New Jersey barrier. .
Girder Selection.
Graphs obtained from South Dakota Concrete Products were the basis for girder spacing and size (See figure B.1). With a 120 ft span length, a 54 M I-Beam girder with 5.25 ft was selected. The width of the bridge is 38 ft from outside edge to outside edge. Therefore, 8 I-Beam girders will be spaced at 5.25 ft on centers along the width of the bridge and an overhang of 7.5 in. on both ends.
Deck Design.
Normal weight concrete is to be used for the decking. The deck thickness was determined to be 8 ¾ in. AASHTO specification for deck thickness is 8 - 8 ¾ in. thick. Due to the amount of anticipated traffic and the weight of vehicles that will be utilizing the bridge, and 8 ¾ in.