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University of Illinois Contribution on Analytical Investigation

University of Illinois Contribution on Analytical Investigation. Amr S. Elnashai Sung Jig Kim Curtis Holub Narutoshi Nakata Oh Sung Kwon. Outline. Introduction Analysis Tools Effect of Vertical Ground Motion on Piers

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University of Illinois Contribution on Analytical Investigation

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  1. University of Illinois Contribution on Analytical Investigation Amr S. Elnashai Sung Jig Kim Curtis Holub Narutoshi Nakata Oh Sung Kwon

  2. Outline • Introduction • Analysis Tools • Effect of Vertical Ground Motion on Piers • Assessment of Bridge with Skewness Considering Torsional Effect on RC Piers • Advanced Bridge Analysis with Soil-Structure Interaction • Future Work

  3. Introduction

  4. Analytical Focus • Analysis of a series of bridge structures subject to different levels of earthquake excitations • DIANA, OpenSees, and Zeus-NL- the MAE Center advanced analysis platform • The unique features of each FE application will be combined as distributed computational simulation using UI-SIMCOR as a simulation coordinator • Analytical work will provide the modeling of PSD conditions to zoom on parameters resulting in high levels of simultaneous horizontal and vertical accelerations. • Study the seismic response of the bridge systems, including foundations and surrounding soils • Appropriate multidirectional loading and boundary conditions for columns can be obtained • Determination of the appropriate input loading for the specimens tested in the subsequent phases of the project

  5. Analysis Tools

  6. Analysis Tools • FE applications • Nonlinear frame analysis, nonlinear hysteretic concrete model, meshed section, freely available • Open source application, soil modeling • 2 and 3-D modeling of reinforced concrete structures • UI-SimCor • Simulation coordinator for the distributed computational simulation • Combine unique features of each application

  7. UI-SimCor Tested Structure UI-SIMCOR Disp. Disp. Force Force Structural Module (Zeus-NL) Soil & Foundation Module (OpenSees) Multi-Platform Simulation Framework • Simulation overview • Key components of implementation • PSD test integration scheme: α-OS method • Sub-structuring technique • Communication between each modules • Hardware for physical testing

  8. UI-SimCor Simulation Coordinator Component 1 Main Routine Object 1of MDL_RF class API Simulation Monitor MDL 1 Client Server Stiffness Evaluation Disp. DOF Mapping Force TCP/IP Network Object nof MDL_RFclass Component n API Static Equilibrium Simulation Monitor MDL n Client Server Dynamic Equilibrium Objects of MDL_AUXclass Equipments AUX DAQ Client Server API Simulation Control Camera Multi-Platform Simulation Framework • Framework architecture

  9. Effect of Vertical Ground Motion on Bridge Pier

  10. Parametric Study with Simple Model L1 L2 H Pier Section • Parameters • Five equal spans with each span length varying 10m to 50m • Variable span (5 cases): The ratio of the length of first span to that of second span is changed from 0.2 to 1.0 • Variable column height (5 cases): 4 m to 12 m • Ground motions recorded at 6 stations • 6 combinations of components for each EQ record • L, T, L+T, L+V, T+V and L+T+V • L: longitudinal GM, T: Transverse GM, V: Vertical GM

  11. Parametric Study with Simple Model VGM HGM Axial force variation Increasing ratio of V due to VGM Axial force Summary • Axial force is mainly affected by vertical ground motion • Especially, as span ratio increase, the effect of vertical seismic motion to axial force increase significantly only when vertical record is considered • Shear capacity is reduced by vertical ground motion • Span length is longer • Span ratio is close to 1 • Column height is shorter • In case of seismic assessment for the structure with above geometric configurations, vertical ground motion should be considered

  12. Complex Straight Bridge 30.795 m 27.215 m 23.700 m 32.260 m 24-#11 for the outer bars 8-#11 for the inner bars Total: 32 - #11 6.085 m 6.085 m Layout of Model Structure 6.575 m 5 6 7 8 9 10 1219 mm • Concrete • - , • Reinforcement bar • , • Initial load (kN) Expansion Joint 50.8mm cover 6085 6575 6290 5945 Rectangular Wall (B=457, H=9000) #4 Stirrups @ 406mm cs. Circular Pier (D=1219) Circular Pier (D=1219) Circular Pier (D=1219) 4740 18960 32260 30795 13875 27215 127755 Layout of Santa Monica Freeway (unit, mm) Modeling and Consideration • Prototype Structure • Collector-Distributor 36 of the Santa Monica (I10) Freeway • Significant damage by Northridge earthquake (1994) • Model Structure • The bridge is assumed to have three piers • The initial loads applied to the top of piers as deck self-weight • 6 earthquake records used in parametric study were selected

  13. Complex Straight Bridge Contribution of VGM to axial force variation Increasing ratio of shear capacity by VGM Horizontal period of vibration Vertical period of vibration Period change by V/H ratio Effect of V/H Ratio • Variable V/H ratios • A fixed time interval and PGA of horizontal ground motion • 16 V/H ratios per earthquake record are considered • Range of 0.5 to 2.0 with an increment of 0.1 • Effect on the periods of vibration • The period is elongated for both components as the vertical amplitude increases • The slope of rate of period increase is steeper up to a V/H Ratio of 1.0 • Effect on Axial Force and Shear Capacity • Axial force variation increases as V/H ratio increases • Shear capacity is reduced by 5% to 36%

  14. Complex Straight Bridge Increasing ratio of capacity by VGM Horizontal period of vibration, Kobe (port Island) Effect of Time Interval • Variable time interval • Range 0.0 to 5.0 sec with an increment of 0.5 sec (11 cases) • This is accomplished by shifting the HGM along the time axis • The original recorded V/H ratios are fixed • Effect on the period vibration and Shear Capacity • The horizontal period is more elongated when the time interval is small • The shear capacity tends to increase slightly as the arrival time interval increases

  15. Torsional Effect on Bridge Pier

  16. Proto-type Bridge FHWA No.4 Skew Bridge (FHWA-SA-97-009, 1996)

  17. Parametric Study with Various Skew Angles Fundamental Vibration Modes 1st Mode: Longitudinal F1 : 1.99 (Hz) 2nd Mode: Transverse F2 : 2.40 (Hz) Parametric Skew Angles 3rd Mode: Rotational F3 : 2.96 (Hz) 4th Mode: Bending F4 : 3.34 (Hz)

  18. Effect of Skew on Natural Frequencies • Up to 30 degree, effect of skew angle is slightly small on the fundamental frequencies. • Effect is more significant on deck bending modes than any other modes.

  19. Parametric Study with Span Length Ratios Parametric Model Span Length Configurations Asymmetric Span Ratios Symmetric Span Ratios

  20. Effect of Span Length Ratios • Rotational and Bending modes are sensitive to the variation of span length ratios. • Effect of the skew angle in any span length ratio configuration are negligible on the natural frequencies.

  21. Effect of Span Length Ratios Torsional effect is higher than any other piers in any configurations. Torsional Effect on RC Piers Torsional / Transverse Ratio in Transverse Mode Symmetric Span Ratios Asymmetric Span Ratios • In symmetric span length configurations, torsional effect on any piers are somewhat similar regardless of skew angle. • With skew angle and asymmetric span length configuration, torsional effect in fundamental modes can be significantly different depends on the location of the piers.

  22. Selection of Bridge Configurations Case 1 Skew Angle: 0 (degree) Span Length Ratio: 1/1.2 : 1.0 : 1/1.2 Case 2 Skew Angle: 30 (degree) Span Length Ratio: 1/1.2 : 1.0 : 1/1.2 Case 3 Skew Angle: 30 (degree) Span Length Ratio: 1/1.2 : 1.0 : 1/2.0 1/2.0 1/1.2 1/1.2 1 1 1 1/1.2 1/1.2 1/1.2 • In order to see the effect of skew angle, two bridge configurations, straight and 30 degree skew angle, are selected for further detail study. • For the evaluation of extreme torsional effect within regular bridge category, configuration with span length ratio, 1/1.2-1.0-1/1.2, is also selected for further study.

  23. Advanced Bridge Analysis with Soil-Structure Interaction

  24. Advanced Bridge Analysis with SSI Background • Effect of soft soil deposit on structural response • SSI, detrimental or beneficial.…? • Ground motion amplification • Displacement redistribution • Force redistribution • Input motion change • Structural period elongation • Radiational and hysteretic damping • Permanent soil deformation  Neglecting SSI can be highly inaccurate Soft Soil Bedrock

  25. Introduction – MRO Bridge Wing wall and abutment Embankment 26 13 9 7 5 3 11 24 Accelerometer channel # Timber pile foundation • Meloland Road Overcrossing Bridge

  26. Introduction – MRO Bridge • Recorded Ground Motions Note 1. B: Bridge array records, D: Downhole array records

  27. Pile Foundation Model Concrete pilecap Timber piles E = 2480 MPa, v = 0.2 . E = 1240 MPa, v = 0.2 0 m Medium clayG = 60 MPa, B = 300 MPa, Cohesion = 35.9 kPa, ρ = 1.5 t/m3 -0.46 m -1.01 m -2.13 m -3.53 m Medium sandGr = 75 MPa, B = 200 MPa, = 33°,Pr = 80 kPa, ρ = 1.9 t/m3 -5.49 m Stiff clay G = 150 MPa, B = 750 MPa,Cohesion = 76.6 kPa, ρ = 1.8 t/m3 17 m -10.06 m Medium sandGr = 75 MPa, B = 200 MPa, = 33°,Pr = 80 kPa, ρ = 1.9 t/m3 -12.50 m -14.63 m Stiff clay G = 150 MPa, B = 750 MPa,Cohesion = 86.2kPa, ρ = 1.8 t/m3 z 48 m -16.77 m y x • Material properties and FE model geometry

  28. Embankment-Abutment Model • FE Model Geometry and Material Properties z Concrete abutment Timber piles E = 2480 MPa, v = 0.2 . E = 1240 MPa, v = 0.2 7.9 m Gravely clayG = 19 MPa, B = 90 MPa, Cohesion = 20kPa, ρ = 1.6 t/m3 (Vs = 110 m/sec, v = 0.4) x 0.0 m Medium clayG = 60 MPa, B = 300 MPa, Cohesion = 35.9 kPa, ρ = 1.5 t/m3 -7.5 m Stiff clay G = 150 MPa, B = 750 MPa,Cohesion = 76.6 kPa, ρ = 1.8 t/m3 -15.0 m -18.0 m -60 m 0.0 m 45 m

  29. Multi-Platform MRO Bridge Model Mass defined in UI-SimCor Structural modelin Zeus-NL Geotechnical model in OpenSees z y x Note: Dimension of bridge is exaggerated. • System configuration

  30. Multi-Platform MRO Bridge Model Ch 26 Ch 13 Ch 9 Ch 7 Ch 5 Ch 3 Ch 11 T1 = 0.341 sec • System identification from recorded ground motions and comparison with analytical model

  31. MRO Bridge Analysis with SSI • Damping evaluation from GM03 Impact-type earthquake loading Maximum response Subsequent peaks from near-free vibration

  32. MRO Bridge Analysis with SSI • Time history analysis and comparison with recorded motion

  33. Summary • The MRO Bridge, which was heavily instrumented and studied, is modeled with two analysis platforms. • Each components of the soil-foundation-bridge system is verified through comparison with previous researches • Multi-Platform analysis is applied to combine two different platforms. • The modal properties is close to the properties identified from measured records. • The time history analysis result showed good correspondence with measured records.

  34. Future Work

  35. Future Work Selection of Strong Motion Records and Loading Protocol • FHWA No. 4 Bridge was selected as the prototype for experimental investigation • Using Zeus-NL with strong motion records, the effect of vertical ground motion on bridge pier will be investigated • 2~3 strong motion records will be selected from the analyses above • Loading protocol from analyses will be provided to pier analysis with DIANA for more extensive analysis

  36. Future Work Verification by DIANA and Computational PSD simulation • The selected loading protocol will be verified using DIANA • Using UI-SimCor, the computational simulation will be conducted • Deck will be simulated using Zeus-NL • Piers will be analyzed using DIANA • The obtained result will be provided to experimental investigation

  37. Thank you &Questions?

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