Section 6: Steel Straddle Bent Caps

Design Criteria

All steel straddle bent caps must satisfy the requirements in the manual and must be evaluated for redundancy according to
AASHTO Guide Specifications for Internal Redundancy of Mechanically-Fastened Built-up Steel Members or AASHTO Guide Specifications for Analysis and Identification of Fracture Critical Members and System Redundant Members,
 as applicable
Members or portions that would otherwise be classified as Nonredundant Steel Tension Members (NSTM) when evaluated based on load path redundancy alone, shall instead be designated in the contract documents as SRMs (system redundant members) or IRMs (Internal redundant members) and need not be subject to the hands-on in-service inspection protocol for NSTM as described in 23 CFR 650. The SRMs or IRMs shall be fabricated according to the American Welding Society (AWS) D1.5 Bridge Welding Code Fracture Control Plan (FCP).

Submittal and Approval

To satisfy FHWA requirements, TxDOT Bridge Division must approve each steel straddle bent cap design for internal redundancy and system redundancy.
 At the 60% PS&E level, in coordination with the District Bridge Engineer, send a pdf of the following documents to the Bridge Division Design Section Director for
Bridge Division approval
.
  • Bridge Layout
  • Steel straddle bent cap plan sheets
  • Steel straddle bent cap design calculation package meeting the requirements of AASHTO Chapter 6, including the calculations demonstrating redundancy. Include explanation of assumptions for modeling and modeling method.
To satisfy FHWA requirements, TxDOT Bridge Division must submit each steel straddle bent cap design for redundancy to FHWA. Upon FHWA and TxDOT's acceptance and approval of 100% Plans, submit final calculation package in accordance with TxDOT Bridge Design Manual – LRFD Chapter 6, including final redundancy calculations, as well as the full completed refined analysis records/computer models as this information will be retained and included with the bridge inspection management system.
An approval memo will be sent to the District and filed in the bridge inspection management system.