INTRODUCTORY WEBINAR:

Transcription

1 INTRODUCTORY WEBINAR: BRIDGE LOAD RATING Webinar Overview: Introduction to the Bridge Load Rating Program Background on load rating Virtis walk-thru Bridge Load Rating Program Helping local agencies and their consultants meet their load rating requirements Sponsored by: Contact Information Center for Technology and Training: Bridge Load Rating Program Website: Questions? Ask in the chat window or comment that you have a question and you d like to use the phone 1

2 Poll Question 1: Overview of load ratings Bridge Load ratings: Establish the safe load capacity Reviewed following inspections Controlled by the weakest link Have a lower target reliability index than design Superstructure We will look at bridge superstructures General Procedure Gather bridge information Determine applied loads Determine capacity of member Conduct load rating calculations Update MBIS database Submit results to bridge owner Governing References Additional References The Manual for Bridge Evaluation, Second Edition, 2011, AASHTO AASHTO LRFD Bridge Design Specifications, Customary U.S. Units: 6 th Edition, 2012 Bridge Analysis Guide, 2005 Edition w/ 2009 Interim Updates, MDOT AASHTO Standard Specifications for Highway Bridges: 17 th Edition,

3 Bridge Advisories Latest bridge information Available on MDOT s website (also linked from CTT s Bridge Program website) When are bridges load rated? New bridge Change in loading or structural capacity Permit requests Load Rating Prioritization: Condition of Bridge Members Bridge Advisory Number: BA Schedule for rating submittal How do I know which of my bridges is due when? Damage/deterioration: Description Location Extents Required Background Info Overview of load rating procedure Design/construction plans & specifications Shop drawings Bridge inspection reports Three rating methods: Allowable Stress Rating (ASR) Load Factor Rating (LFR) Load and Resistance Factor Rating (LRFR) 3

4 Documentation Assumptions Calculations input and output files Components to Load Ratings Federal Inventory Federal Operating Michigan Operating Overload (Permit) Vehicles Note: In LRFR these are referred to as: Design (Federal) Legal (Michigan) Permit (Overload) Inventory and Operating Dead Load Inventory Corresponds to customary design level of stresses Operating Describes maximum permissible live load for bridge Compute according to existing conditions Material unit weight must be at least the value specified in the AASHTO Design Specs. Composite beams: Separate loads acting on noncomposite and composite sections Live Load HS-20 / HL-93 Truck or Lane Load 28 Michigan Legal Trucks 20 Overload Trucks Wheel Load If deck controls Live Load Designations Normal Lowest set of max loadings that apply to all roads in Michigan Designated Local or state owned roads that allow loads heavier than normal Special Designated Typically applies to interstate roadways 4

5 Capacity of Member General Equation Nominal capacity from Bridge Analysis Guide Structural steel Reinforced concrete Prestressed concrete Load factor methods for timber and masonry are not available use ASR or LRFR Rating Factor = Reserve Capacity for Live Load Legal Live Load General Equation (LFR) C A1 D RF A2( L I) RF = Rating factor for live load capacity C = Capacity of the member D = Dead load on member L = Live load on member I = Impact factor A 1 = Factor for dead load = Factor for live load A 2 General Equation (LRFR) RF = rating factor C = capacity γ DC = LRFD load factor for structural components and attachments DC = dead load effect due to structural components and attachments γ DW = LRFD load factor for wearing surfaces and utilities DW = dead load effect due to wearing surfaces and utilities γ P = LRFD load factor for permanent loads other than dead loads = 1.0 P = permanent loads other than dead loads γ LL = evaluation live load factor LL = live load effect IM = dynamic load allowance Rating Factor Basic Submittal Process A rating factor will be produced for each beam capacity (flexure, shear ) and legal vehicle combination Lowest rating factor indicates the controlling factor Owner or appointee enters data into the Michigan Bridge Inspection System (MBIS) MDOT manages database MDOT submits reports to FHWA 5

6 MBIS Assumption Form MBIS Summary Form Questions? Poll Question 2 Ask in the chat window or comment that you have a question and you d like to use the phone Virtis Virtis is a software product managed by AASHTO and a user s group for the purpose of load rating bridge superstructures MDOT has purchased a license which allows local agencies and their consultants to obtain Virtis for use on Michigan bridges Virtis - Capabilities Simple or continuous spans, hinges Steel, reinforced & prestressed concrete Steel rolled beams, plate girders, hybrid systems Harped and/or debonded strands Parallel, tapered, and parabolic webs Transverse and longitudinal stiffened Load rate individual members, whole bridge, or multiple bridges 6

7 How to get Virtis Bridge Load Rating Program Website Submit AASHTO software request form to CTT CTT will verify Michigan agencies (consultants must submit letter stating their use of software only for MI bridges) AASHTO will send a supplemental license agreement to requestor Software will be issued direct from the software vendor Must be relicensed each year For more information: Getting Started Gather Background Information Virtis Organization of Bridge Inventory Virtis Bridge Description Virtis Material Properties 7

8 Virtis Material Properties, cont. Virtis Beam Shapes Virtis Beam Shapes, cont. Virtis Appurtenances Virtis Appurtenances, cont. Virtis Superstructure Definition 8

9 Virtis Superstructure Definition, cont. Virtis - Typical Section Overview Virtis Framing Plan Details Virtis Individual Member Details Virtis Analysis Settings Michigan Trucks: Vehicle downloads: MDOT s Virtis support webpage (linked from Resource page) 9

10 Virtis Analysis Progress Virtis Analysis Reports Virtis Analysis Reports, cont. Virtis Tutorials: Why Virtis? Easy to keep calculations up to date Can be adapted quickly to reflect most current bridge condition Store all load rating files in one location Reduce costs when updating ratings Files are portable can be supplied to new consultant when updated rating is required Questions? Ask in the chat window or comment that you have a question and you d like to use the phone 10

11 Getting Help: CTT Call Center Center for Technology and Training: Upcoming Classroom Sessions Guided tutorials Hands-on activities Seating limited to 20 participants Bring a laptop with Virtis installed IT assistance will be available 12 hours of bridge inspector recurrent training Training Session Locations and Schedule Poll Question 3: Schedule: Day 1: 8:00 AM 5:00 PM Day 2: 8:00 AM 12:00 PM Locations: Escanaba (April 10 & 11) Saginaw (April 30 & May 1) Howell (May 2 & 3) Grayling (June 4 & 5) Grand Rapids (June 6 & 7) Big Rapids (September 11 & 12) Thank you for your attention! Additional Assistance: loadrating@mtu.edu 11