Advanced Precast Concrete Dual-Shell Steel Columns

Transcription

1 Advanced Precast Concrete Dal-Shell Steel Colmns Gabriele Gerrini Gradate Stdent Researcher Jose' I. Restrepo Professor, Principal Investigator Universit of California, San Diego Strctral Engineering Department Otline Literatre Review Project Description Dal-Shell Technolog Self-Centering Behavior Energ Dissipation Design Principles Prototpe Bridge & Specimen Project Schedle 2 1

2 Literatre Review Gebman, M., Ashford, S. and Restrepo, J.I. (2006), Mechanical Axial Force Transfer within Cast-In-Steel-Shell Piles Verification throgh Fll-Scale Experimentation and Finite Element Analsis, Proceedings of the Fifth National Seismic Conference on Bridges and Highwas, San Francisco, California, USA. Hewes, J.T., and Priestle, M.J.N. (2001), "Experimental Testing of Unbonded Post-Tensioned Precast Concrete Segmental Bridge Colmns", Proceedings of the 6th Caltrans Seismic Research Workshop Program, California Deptartment of Transportation, Engineering Service Center, Sacramento, California, USA. Mander, J.B., and Cheng, C-T. (1997), "Seismic Resistance of Bridge Piers based on Damage Avoidance Design", Tech. Rep. No. NCEER , National Center for Earthqake Engineering Research, Deptartment of Civil and Environmental Engineering, State Universit of New York, Bffalo, New York, USA. Marriott, D., Pampanin, S., and Palermo, A. (2008), Qasi-static and Psedo-dnamic Testing of Unbonded Post-tensioned Rocking Bridge Piers with External Replaceable Dissipaters", Earthqake Engineering and Strctral Dnamics, John Wile & Sons. Palermo, A., and Pampanin, S. (2010), Enhanced Seismic Performance of Hbrid Bridge Sstems: Comparison with Traditional Monolithic Soltions", Jornal of Earthqake Engineering, Vol. 12, No. 8, pp to 1295, Talor & Francis, London, UK. Priestle, M.J.N. and Tao, J.R.T. (1993), Seismic Response of Precast Prestressed Concrete Frames with Partiall Debonded Tendons, PCI Jornal, 38(1), Rahman, A. and Restrepo, J.I. (2000), Earthqake Resistant Precast Concrete Bildings: Seismic Performance of Cantilever Walls Prestressed sing Unbonded Tendons, Research Report , Department of Civil Engineering, Universit of Canterbr, Christchrch, New Zealand. Sakai, J. and Mahin, S. (2004), Mitigation of residal displacements of reinforced concrete bridge colmns, Proceedings of the 20th US-Japan Bridge Engineering Workshop, Tskba, Japan. Tobolski, M.J. (2010), Improving the Design and Performance of Concrete Bridges in Seismic Regions, Ph.D. thesis, Department of Strctral Engineering, Universit of California - San Diego, La Jolla, California, USA. Toranzo-Dianderas, L.A. (2002), The Use of Rocking Walls in Confined Masonr Strctres: a Performance-Based Approach, Ph.D. thesis, Department of Civil Engineering, Universit of Canterbr, Christchrch, New Zealand. 3 Project Description Goals Accelerated Bridge Constrction (ABC - FHWA, Caltrans) Improved bridge pier seismic performance Main featres precast bent cap Dal steel shells Postensioning / recentering Energ dissipation Fiber-reinforced mortar dal steel shells fiber-reinforced mortar energ dissipator PT bar PT bar energ dissipator dal steel shells fll height bolt (Marriott, Pampanin, Palermo) 4 2

3 Dal-Shell Technolog Advantages Precast constrction w/ permanent formworks Redced colmn weight (hollow section) No reinforcing cage Redced constrction time 5 Self-Centering Behavior Advantages Limited strctral damage compared to monolithic sstems Small residal displacements compared to monolithic case Operabilit right after strong shakes Added energ dissipation Monolithic sstem Self-centering sstem Shear-wall test reslts (Restrepo, Mander, Holden) 6 3

4 Self-Centering Behavior Post-tensioning Details Top view Open possibilit of replacing PT bars No anchoring wedges (tendon failre) Additional flexibilit at PT anchorage 7" x 7.5" x 1.75" steel anchor plate (DSI) 5" x 5" x 1.25" steel anchor plate (DSI) 0.9 in^2 hole Section A-A 5" x 5" x 1.25" steel anchor plate (DSI) 7" x 7.5" x 1.75" steel anchor plate (DSI) 8" x 8" x 1" steel plate A A 8" x 8" x 1. 5" polrethane bearings 8" x 8" steel and polrethane plates, stacked 8" x 8" x 0.25" steel plates 7 Energ Dissipation Internal Aestheticall ok Hard to repair/replace Unbonded length Mild reinforcement (Tobolski) External Eas to repair/replace Aesthetic mitigation needed 8 (Marriott, Pmapanin, Palermo) 4

5 Design Principles Ensre Flag-shaped Response FED, Limit the energ dissipation ratio: Λ = P + F + F Prevent PT Bars from Yielding PS, ED, Check the most-tensile bar at ltimate rotation (θ j, ): where: θ j, θ ( ) 0.25 PS PS B FPS = n j j, dps c LUPS Λ B + n j E 1 simple cantilever = 2 fixed-fixed ends KB Λ B = E A L PS PS UPS F = F + F F A PS PS, i PS PS, Λ 1 c K B = bearing compressive stiffness d PS 9 Design Principles Ultimate Moment Ultimate Displacement = f, + v, + j, Confined concrete stress-block Oter shell in compression Dissipators provide tensile force 10 Elastic flexral component 3 Vb, H f, = 2 3n E I Elastic shear component Vb, H 3V b, H v, = G A E A Joint rigid rotation = θ H j, j, j c g c s c g where θ j, is the target ltimate drift ratio, tpicall 4%. 5

6 Design Principles Nominal Yield Moment Nominal Yield Displacement = f, + v, + j, Elastic flexral component 3 Vb, H f, = 2 3n E I j c g Unconfined concrete stress-block Oter shell in compression Dissipators provide tensile force 11 Elastic shear component Vb, H 3V b, H v, = G A E A c s c g Joint rigid rotation = θ H j, j, where θ j, is the drift ratio when half of the dissipators have ielded. Prototpe Bridge & Specimen Prototpe Bridge (Tobolski) 12 6

7 Prototpe Bridge & Specimen W/ External Dissipators W/ Internal Dissipators 13 Project Schedle Ma 2011 Polrethane cclic material test Energ dissipators cclic material test Opensees model of prototpe and test nit Jne 2011 Constrction of colmn nit Opensees model of prototpe and test nit Jl 2011 Cclic, qasi-static test of nit w/ external dissipators Cclic, qasi-static test of nit w/ internal dissipators Agst September 2011 Experimental data processing Refinement of Opensees models October December 2011 Report writing and sbmission 14 7

8 Project Schedle Polrethane Pad Test Steel plates Polrethane Pad 15 THANK YOU 8