F-1 APPENDIX F 1 PROPOSED GUIDE SPECIFICATION 2 APPLICATION EXAMPLES 3 F.1 Introduction 4 Based on the work performed to characterize the redundancy of the bridges studied, a set of requirements 5 was developed so an Engineer can establish whether a steel bridge possesses an adequate level of 6 redundancy after the failure of a main tension member. Given that the characterization of redundancy 7 requires the consideration of every alternate load path and complex interactions between the components 8 of a bridge, 3-D finite element analysis (FEA) is considered as the most suitable analysis tool. 9 The FEA methodology developed in NCHRP Project 12-87a is applicable to typical steel bridges that 10 contained members designated as fracture critical members (FCMs): simple span and continuous I-girder 11 and tub-girder bridges, through-girder bridges, truss bridges, and tied-arch bridges. The methodology has 12 not been thoroughly benchmarked for non-typical steel bridges, i.e., cable stayed bridges, suspension 13 bridges, etc. However, the overall methodology discussed hereafter may be used to evaluate non-typical 14 bridges at the discretion of the Owner and/or Engineer. For a bridge superstructure which has one or more 15 members that may be considered as fracture critical members (FCMs), the redundancy analysis consists of 16 the following required steps: 17 18 1. Selection of an adequate finite element analysis tool as described in section F.1.1. 19 2. Construction of a three-dimensional finite element model capable of simultaneously capturing 20 material and geometrical non-linearity and the formation of alternative load paths. The 21 construction of these model requires the analysist to: 22 • Construct the geometry, meshes and of the different components of the superstructure 23 steelwork as described in section F.1.2. 24 • Construct the geometry, meshes and of the concrete slab and concrete barriers as described 25 in section F.1.3. 26 • Model the connections between the steelwork components, including connection failure 27 and/or flexibility when required. This requirement is described in section F.1.4. 28 • Model the frictional contact interaction between the slab and the steelwork, and model 29 shear stud behavior when required, as described in section F.1.5. 30 • Include the effect of the flexibility of the substructure as described in section F.1.6. 31 3. Identification of steel members that are subjected to net tension across its entire or a portion of its 32 cross-section, and which failure is suspected to result in collapse or loss of serviceability. At the 33 very least, the Engineer must include that least the following, considering one complete member 34 failure, i.e., the entire cross-section of the member is failed,, at a time: 35 • In girder bridges (I-girder, tub-girder, wide flange girder, and through-girder bridges), at 36 least, the following member failures shall be investigated: 37
PROPOSED GUIDE SPECIFICATION APPLICATION EXAMPLES
Jun 16, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
