Aerodynami stability (Tài liệu nghiên cứu sự ổn định động lực học của các cây cầu )

Aerodynamic Stability of a Longspan Bridge Jongdae Kim, Ph.D. [...]... Outline • Aerodynamic Stability • Flutter Derivatives from Free Oscillation Test • Flutter Derivatives from Forced Oscillation Test • Flutter Derivatives from CFD Analysi Aerodynamic Stability Aerodynamic Stability The primary concerns for long-span bridges for wind effects a) Stability regarding aerodynamic flutter for the bridge deck b) Buffeting of the structure due to the oncoming turbulent wind Aerodynamically... m  p * Length Scale 1: 60 SECTION MODEL SCALING PARAMETERS (TYPICAL FOR 1:60 SCALE OF MODEL) VALUE 1 Bridge Model (Plate Girder Bridge) MODEL Length (m) Depth (m) Width (m) Mass (kg/m) MMI (kg-m2 /m) f L (Hz) – lift f T (Hz) - torsion 2.134 0.048 0.457 7.77 0.218 3.02 5.127 TYPICAL PROTOTYPE (at 1:60 Scale) -3.0 27.4 27965 2.87 x 106 - PROPERTIES OF THE DYNAMIC SECTION MODEL Static Model Test 0.8... (radians) Torsional Response (radians) Torsional Response (radians) 0 -0.04 -0.06 -0.04 -0.06 -0.06 -0.08 -0.08 MEAN MEAN MEAN PEAK(RMS*3. 5) PEAK(RMS*3. 5) -0.08 PEAK(RMS*3. 5) -0.1 0 2 4 Deck Height Wind speed (V/fB) Smooth Flow 6 -0.1 0 2 4 6 0 2 4 Deck Height Wind speed (V/fB) Deck Height Wind speed (V/fB) Small Grid Large Grid Dynamic Section Model Test Results – Torsional Response 6 Flutter Instability... PEAK(RMS*3. 5) 0.08 Normalized Vertical Response (y/B) Normalized Vertical Response (y/B) 0.05 MEAN PEAK(RMS*3. 5) Normalized Vertical Response (y/B) MEAN 0.06 0.04 0.02 0.08 0.06 0.04 0.02 MEAN PEAK(RMS*3. 5) -0.1 0 0 2 4 6 Deck Height Wind speed (V/fB) Smooth Flow 8 0 0 2 4 6 Deck Height Wind speed (V/fB) Small Grid 8 0 5 Deck Height Wind speed (V/fB) Large Grid Dynamic Section Model Test Results – Vertical... derivatives for the aerodynamic stability analysis and aerodynamic admittance functions for the serviceability analysis of the structure Static & Dynamic Model Tests Static Model Test (Fixed deck)  Force coefficients (drag, lift, moment coeff) Dynamic Model Test (Free moving deck)  wind induced motion (vortex induced vibration, flutter, etc) Bridge Model (Plate Girder Bridge) PARAMETER SIMILITUDE REQUIREMENT... Angle of attack (degree) 20 -20 -10 0 10 Angle of attack (degree) 20 Dynamic Model Test DYNAMIC SECTION MODEL RIG Details of Dynamic Section Model Rig Dynamic Section Model – Smooth Flow Condition Dynamic Section Model – Turbulent Flow Condition (Large Grid) Dynamic Section Model – Turbulent Flow Condition (Small Grid) a36103.mst a36202.mst a36302.mst 0.1 0.1 0.1 0 -0.05 PEAK(RMS*3. 5) 0.08 Normalized Vertical... the stability criteria for the design wind speed, wind tunnel tests have traditionally been carried out by changing deck configurations in an ad-hoc manner until the stability is assured After a decision has been reached regarding the optimized bridge deck configuration, detailed wind tunnel tests are performed, which in some circumstances, include estimates of the aerodynamic derivatives for the aerodynamic... J.E Cermak L.E Robertson J Skilling M Yamasaki Big Wind Tunnels • BLWTL (London, Ontario, Canada) - The Boundary Layer Wind Tunnel Lab • RWDI (Guelph, Ontario, Canada) - Rowan Williams Davies and Irwin Inc • CPP (Fort Collins, Colorado, USA) - Cermak, Peterka, Peterson • BMTFM (Teddington, Middlesex, UK) - British Maritime Technology, Fluid Mechanics The University of Western Ontario Alan G Davenport... Deck Height Wind speed (V/fB) Small Grid Large Grid Dynamic Section Model Test Results – Torsional Response 6 Flutter Instability Criteria (How to know the onset of flutter) 1 Random (Peak factor=3~ 4)  Sinusoidal (Peak factor=1.4 1) 2 Response greater than an acceptable magnitude 3 Steepness change of response curve5  . Aerodynamic Stability of a Longspan Bridge Jongdae Kim, Ph.D.