A062 NDT of steel materials steel bridge design

NDT of Steel Materials, Steel Bridge Design, and Evaluation as Per LRFR By Piya Chotickai tailieuxdcd@gmail.com Outline Steel Bridge Design  Design consideration and limit state  Design loads and load combination  Load distribution Nondestructive Evaluation (NDE)  Principles of NDE  Dye Penetrant Testing  Ultrasonic Testing  Magnetic Particle Testing  Acoustic Emission Load Evaluation per LRFR  Load rating from standards  Load rating from bridge load test tailieuxdcd@gmail.com Steel Bridge Design Basic design expression in AASHTO LRFD: iiQi  Rn Where Qi = force effect, Rn = nominal resistance, I = load factor,  = resistance factor, I = load modification factor Load modification factor (I) accounts ductility, redundancy, and operation importance of the bridge I = D R i D = 1.0 for conventional design R = 1.0 for conventional redundancy, 1.05 for nonredundant members I = 1.0 for conventional bridge tailieuxdcd@gmail.com Limit state is a condition beyond which a bridge system or bridge component ceases to fulfill the function for which it is designed Strength Limit State:  Strength I  Normal vehicular use of the bridge without wind  Strength II  Owner-specified special design vehicle (or permit vehicles) without wind  Strength III  Bridge exposed to wind velocity > 90 km/hr High winds prevent the presence of significant LL on bridge  Strength IV  High dead load to live load force effect ratios (Long Span Bridge)  Strength V  Normal vehicles with wind of 90 km/hr tailieuxdcd@gmail.com Serviceability Limit State:  Service I  Normal operational use of the bridge with 90 km/hr wind and all loads taken at their nominal values  Service II  Control yielding of steel structures and slip of slip-critical connections due to vehicular live load Fatigue Limit State  Fatigue and fracture load combination relating to repetitive gravitational vehicular live load and dynamic responses under a single design truck tailieuxdcd@gmail.com Load Combination and Load Factor tailieuxdcd@gmail.com Load Factor for Permanent Load tailieuxdcd@gmail.com Resistance Factor for Strength Limit State tailieuxdcd@gmail.com Bridge Analysis Structural response: Live load model and strain gage instrumentation Thai Truck 1.3 HS20-44 Truck Load 1.3 HS20-44 Lane Load tailieuxdcd@gmail.com Obtain structural response from 1-D model with GDF or 3-D analysis model GDF ~ 0.21-0.52 (Schilling, 1982) AASHTO LRFD provided GDF equations obtained from extensive finite element analyses AASHTO LRFD: 30% Impact Factor 3-D Model 1-D Model with GDF tailieuxdcd@gmail.com Only permanent loads and vehicular loads are considered in load rating Dead Load: Structural component and attachment (DC), wearing surface and utilities (DW) Accordance with the actual conditions Secondary effect from prestressing shall be considered as permanent load Vehicular Load: Design Load: HL-93 design load per LRFD Legal Load: AASHTO legal load (Type 3, Type 3S2, Type 3-3) Permit Load: Actual Permit Load tailieuxdcd@gmail.com Design Load (HL-93) tailieuxdcd@gmail.com Type Type 3S2 Type 3-3 AASHTO Legal Loads tailieuxdcd@gmail.com Load Rating Equation: RF  Where C C S  Rn C( = = = = = = DC )(DC)  ( DW )(DW)  ( ( L )LL  IM P P) CS Rn for strength limit state fR for service limit state condition factor system factor (redundancy) LRFD resistance factor nominal resistance tailieuxdcd@gmail.com NBI Rating (Scale 1-9) and Repair Actions NBI Rating Action Minor maintenance Major maintenance Minor repair Major repair Rehabilitation Replacement tailieuxdcd@gmail.com Condition Factor (C) Structural Condition NBI Rating C Good or Satisfactory or higher 1.00 Fair 0.95 Poor or Lower 0.85 tailieuxdcd@gmail.com Load Factor for Load Rating (LRFR 2003) tailieuxdcd@gmail.com Legal Load Factor (L) Permit Load Factor (L) tailieuxdcd@gmail.com IM = = = Dynamic Load Allowance 15% for Fatigue Limit State 33% for Other Limit State Multiply static load with (1+IM/100) Impact factor = Max Dyn Response / Max Static Impact Factor at Bottom Flange – Use FFT to Define Dynamic Response tailieuxdcd@gmail.com Dynamic Load Factor (Nowak and Zhou 1985) Mean Standard Deviation Type of Structure Range Average Range Average P/C AASHTO girders 0.05-0.10 0.09 0.03-0.07 0.05 P/C Box & Slabs 0.10-0.15 0.14 0.08-0.40 0.30 Steel girders 0.08-0.20 0.14 0.05-0.20 0.10 Rigid frame, truss 0.10-0.25 0.17 0.12-0.30 0.26 tailieuxdcd@gmail.com Load Rating by Load Testing Load Tests: Diagnostic Test - To determine certain response characteristics - Can be static or dynamic test Proof Test - To establish the maximum safe load where the bridge behavior is within the linear elastic range - Mostly static Why does structural response from analysis differ from actual behavior? Due to unintended composite action, secondary members, unintended continuity/fixity, and nonstructural elements tailieuxdcd@gmail.com Benefits: Unknown or low-rated components Load Distribution Difficult to analyze the effects of observe deterioration or damage on the load carrying capacity Fatigue evaluation and distortion-induced fatigue Dynamic load allowance Measurements: Strain – electrical resistance gages Displacement and rotation – laser, displacement transducer (LVDT), tiltmeter Dynamic characteristic - accelerometer tailieuxdcd@gmail.com RFT = RFC * K Where RFT = Load rating for live-load capacity based on load test RFC = Rating Factor from analysis K = (Measured Response)/(Analysis Response) Multi-Axle Vehicle tailieuxdcd@gmail.com Values for Kb tailieuxdcd@gmail.com Thank you tailieuxdcd@gmail.com