By Alejandro Amaris, Stefano Pampanin, Des Bull, Athol Carr.

Transcription

1 NUMERICAL INVESTIGATIONS ON THE SEISMIC RESPONSE OF MULTI-STOREY HYBRID PRECAST CONCRETE FRAMES WITH NON-TEARING FLOOR CONNECTIONS By Alejandro Amaris, Stefano Pampanin, Des Bull, Athol Carr. New Zealand Society of Earthquake Engineering. Christchurch, 9

2 Introduction Problems associated with Beam sidesway Mechanism of Plastic deformation (fib Bulletin 7, ) Sidesway Mechanism and beam elongation effects for precast frame systems.

3 Alternative innovative solutions to reduce damage in the floor SOLUTION A Gapping frame system (traditional Jointed ductile connection) + Articulated (jointed) floor SOLUTION B Non-gapping frame system (recently proposed) + Standard floor solution

4 SOLUTION B Non-Gapping frame System nnovative no-gapping and no-tearing jointed ductile connection + standard floor solution External energy dissipaters T-Shape steel plate Tendon profile Top Mono Hinge Corbel External Dissipater Experimental investigations

5 Numerical Investigations on a Multistorey, multi-bay Hybrid Precast Frame Systems. m Storeys at.8 m, total height 19. m Building Description PRESSS Design Handbook (NZCS, 9) Building Description Building Location: Wellington Soil type: C (shallow soil) Importance level: Return period: year Near fault effects within km Design: DBD procedures for Monolithic system Target interstorey drift:.%

6 Numerical Investigations: Monolithic Beam Column Models excluding and including beam elongation. Elastic column Mon model The plastic hinge is modeled as a rotational spring using a Takeda hysteresis behaviour. M (knm) F (kn) q (1/m) Elastic Beam Mon_ beam-elong model Beam elongation is modeled as series of inelastic truss elements representing the concrete and reinforcing steel Concrete element (Multi-spring element) F (kn) D D Reinforcing steel (compound element)

7 Numerical Investigations: Hybrid Beam Column Models with nontearing connection. M (knm) Elastic column Elastic Beam Hy_non-tear model The connection is modeled with the combination of moment rotation contributions of two springs in parallel. q (1/m) Linear elastic M (knm) q (1/m) - Bi-linear inelastic

8 Numerical Investigations: Hybrid Beam Column Models excluding and including beam elongation. Elastic column Elastic Beam Hy model Hybrid Connection is modeled as combination of the moment rotation contributions of two springs in parallel M (knm) q (1/m) Bi-Linear elastic F (kn) M (knm) q (1/m) Bi-linear inelastic F (kn) Hy_ beam-elong model Beam elongation is modeled as series of inelastic truss elements representing the concrete, reinforcing steel and post-tensioned tendons D Concrete element (Multi-spring element) F (kn) Reinforcing steel (compound element) Post-tensioned tendons (Linear elastic) D D

9 Lateral Force (kn) Numerical Investigations Adaptive Push over Analysis Roof Displacement (mm) 1 1 Adaptive push over analysis with an initial inverted triangular shape Roof Drift (%) Hy_ Hy Hy_ Mon Mon_ non-tear beam-elong beam-elong

10 Storey Storey Numerical Investigations-Time History Analysis: Mean and maxima interstorey drift ratio Storey Storey Storey Storey Hy-non-tear 1 Mean Max Interstorey Drift, % Hy-beam-elong 1 Mean Max Interstorey Drift, % Mon-beam-elong 1 Mean Max Interstorey Drift, % Far field Hy-non-tear 1 Mean Max Interstorey Drift, % Hy-beam-elong 1 Mean Max Interstorey Drift, % Mon-beam-elong 1 Mean Max Interstorey Drift, % Near field

11 Storey Numerical Investigations-Time History Analysis: Mean and cumulative storey shear Storey Mon Mon_beam-elong Hy Hy_beam-elong Hy_non-tear Mon Mon_beam-elong Hy Hy_beam-elong Hy_non-tear Storey Shear (kn) Mean and cumulative storey shears for far field set of Earthquakes 1 1 Cumulative Shear (kn)

12 Conclusions In general, the response of the hybrid system using non-tearing connection was very satisfactory under push-over and THA. Push over analysis indicates that lateral stiffness was lower for the hybrid with non-tearing connections when compared with the traditional hybrid systems. However, the total base shear (for the same imposed drift level) was similar. Additionally, push over analysis indicate that beam elongation were higher in the nd floor of the frames were plastic hinge was 7.1% and.1% of the beam depth for the monolithic and hybrid systems respectively.

13 Conclusions THA indicate that no excessive increase on inter-story drift response when compared to the targeted % of drift was found for all the models except the set of near field earthquakes which were more severe for the Hybrid with non-tearing connections. Beam elongation effects change the distribution of moments, shears and inter-storey drifts throughout the frames specially the first two storeys. For the hybrid with non tearing solution the storey shears remain constant. A series of numerical investigations are under-going to provide further confirmations of the behaviour of this type of systems using non-tearing connections.

14 Acknowledgments The financial support provided by the New Zealand Foundation of Research, Science and Technology (FRST) under the Future Building System research project is greatly appreciated.