The Calibration of the AASHTO ASD and LRFD for Maryland Sign and High Mast Lighting Structure Design

Federal Highway Administration (FHWA) new regulation (NPRM-23 CFR part 625) mandates State Transportation Agencies to adapt American Association of State Highway and Transportation Officials (AASHTO) LTS 6 (ASD) for sign and signal structure designs. Maryland State Highway Administration (MDOT SHA)/OOTS is currently developing the new Signal standards with collaboration of the Bridge Engineering Software and Technology (BEST) Center, University of Maryland, also the proposer of this proposal. FHWA also published the LRFD design edition in 2015 which may require the states to adopt in the future. The update for overhead sign structures standard design is currently in progress in-house of the MDOT SHA/OOTS. However, the following challenges are faced which require further research: (1) Complete design parameters of MD-specified sign structures by identifying the Maryland-specified Fatigue Importance Category Factor (I, II or III) for sign and light structure designs. (2) Defining wind pressure applicable by both ASD & LRFD design codes for sign structure design for different regions of Maryland (Eastern Shore, Appalachia Mountain and the Baltimore-Washington corridor). (3) Determining the additional impact in transition to the LRFD design in near future, i.e. wind pressure determination? (4) Developing fatigue load resisting connections, i.e. choosing between pipe-to-pipe vs gusset-plate weld connections for box truss sign structures. groove welded vs socket welded, etc. (5) Reviewing and conformance of SABRE design models with alternate commercial licensed finite element analysis software, i.e. STADD Pro.