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University of Illinois Contribution

Seismic Simulation and Design of Bridge Columns under Combined Actions, and Implications on System Response. University of Illinois Contribution. Jan. 23, 2009 Amr S. Elnashai Sung Jig Kim Curtis Holub. Analytical Investigation. Effect of V/H Ratio. Shear Demand. 595%. LP-COR-L

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University of Illinois Contribution

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  1. Seismic Simulation and Design of Bridge Columns under Combined Actions, and Implications on System Response University of Illinois Contribution Jan. 23, 2009 Amr S. Elnashai Sung Jig Kim Curtis Holub

  2. Analytical Investigation

  3. Effect of V/H Ratio Shear Demand 595% LP-COR-L NO-SCS-L Shear Capacity LP-COR-L NO-SCS-L • 16 V/H ratios per earthquake record (5 stations) • Axial force variation increases noticeably by up to 600% due to vertical ground motion • The slight increases in shear demand and noteworthy reductions in shear capacity of up to 30% as V/H ratio increases.

  4. Effect of Time Interval Shear capacity Axial Force Variation • 11 cases of arrival time intervals for each record • Results were compared against the response with coincident horizontal and vertical peaks. • The contribution of vertical ground motion to the axial force variation tends to be reduced as time interval increases. • The effect was relatively small when compared to the effect of V/H ratio. • Although no clear correlation exists between the shear demand or capacity and the time lag, noticeable changes are noted up to 20%

  5. Large Scale Experiments

  6. Prototype and Test Matrix • Prototype: FHWA Bridge #4 • Half scale pier (D=610mm, H=3048mm) • Rebar ratios: 2.79% for long.; 0.84 and 0.50% for spiral • Test Matrix • Hybrid Simulation: IPH and IPV

  7. Prototype and Test Matrix Dx Fy • Prototype: FHWA Bridge #4 • Test Matrix • Hybrid simulations : IPH and IPV • Cyclic Static Tests: ICT and ICC • Consideration of the observed axial force levels obtained during the second hybrid simulation • Displacement Control for Lateral and Rotational displacements • Force Control for Axial Forces

  8. Hybrid Simulation Ground Motions Sylmar Converter Station, Northridge Earthquake (Mw 6.7) V/H ratio: 1.2 (ah=0.61g and av=0.73g) No notable change in lateral displacement and moment Significant effect on axial force variation (increases of up to 100%) Fluctuation of lateral stiffness Axial tension force (390 kN) IPH and IPV

  9. Crack and Strain Crack Longitudinal strain and curvature – No significant effect Spiral strain Significant increase up to 200% when vertical ground motion is included IPH IPV Blue: IPH Red: IPV IPH IPV Left Right Front IPH and IPV

  10. Cyclic Tests ICC ICT 56% ICT and ICC • Loading Scenario • Positive cyclic lateral displacement with constant axial load • ICT: 222 kN (50 kips), ICC: -1112 kN (250 kips) • ICT: ductile behavior and strength increase by 4% • ICC: brittle shear failure and strength degradation by 56%

  11. Conclusions • The hybrid simulations results confirmed that the vertical motion can significantly affect pier behavior • Significant increase (up to 100%) of axial force variation leads to more severe cracking and damage • Spiral strains increased by 200% when vertical ground motion is included • The cyclic tests confirmed that the different axial load level can impact the pier behavior and change the failure mode

  12. Small Scale Experiments

  13. Small Scale Testing Program Experimental Setup (1/10 Scale)

  14. Small Scale Testing Program Test Matrix • 28 specimens • 1/10 scale of ICC and ICT • Various lateral and vertical loading patterns and magnitude

  15. Small Scale Testing Program Preliminary Test • 30% axial compression • Cyclic lateral loading

  16. Publications • Journal • Kim, S. J., Holub, C., and Elnashai, A., “Analytical Assessment of the Effect of Vertical Earthquake Motion on RC Bridge Piers”, ASCE Journal of Structural Engineering, (in review) • Holub, C., Kim, S. J., and Elnashai, A., “Aspects of Multi-Axial Pseudo Dynamic Testing of RC Members”, Earthquake Engineering and Engineering Vibration, (to be submitted) • Holub, C., Kim, S. J., and Elnashai, A., “Behavior of RC Bridge Piers Subjected to Vertical Earthquake Motion—Part 1: Experimental Framework”, Engineering Structures, (to be submitted) • Kim, S. J., Holub, C., and Elnashai, A., “Behavior of RC Bridge Piers Subjected to Vertical Earthquake Motion—Part 2: Experimental Results”, Engineering Structures, (to be submitted) • Conference • Elnashai, A., Kim, S. J., and Holub, C., “Assessment of RC Bridges under Horizontal and Vertical Earthquake Motion”, 3rd International Conference on Concrete & Development, Tehran, Iran, April, 2009 • Kim, S. J., Holub, C., and Elnashai, A., “The Analytical and Experimental Investigation of the Effect of Vertical Ground Motion on RC Bridge Pier”, 14th World Conference on Earthquake Engineering (14WCEE), Beijing, China, Oct, 2008 • Report • Kim, S. J. and Elnashai, A., “Seismic Assessment Of RC Structures Considering Vertical Ground Motion”, Mid-America Earthquake Center, Report No. 08-03, 2008. Download url: http://hdl.handle.net/2142/9454

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