Presentation on theme: "PEER 2002 PEER Annual Meeting PEER 2002 Annual Meeting Ian Robertson University of Hawaii."— Presentation transcript:
PEER 2002 PEER Annual Meeting PEER 2002 Annual Meeting Ian Robertson University of Hawaii
Objective Development of a load-deformation hysteretic model for slab-column connections of varying dimensions, reinforcement arrangements, gravity loads, and lateral loading routines. Specific reference to non-ductile specimens with discontinuous slab reinforcement.
Punching Shear Failure No Continuity Reinforcement
Approach Task 1: Assemble Web Database Task 2: Fabricate and test 6 non-ductile interior connections Task 3: Develop backbone curve parameters Task 4: Develop hysteretic model Task 5: Validate hysteretic model
Non-Ductile Specimen tests Six specimens fabricated Three tested with varying gravity load levels V g /V o = 0.2, 0.28, 0.47 Three with varying slab reinforcement ratios = 0.3, 0.5 & 0.8% top reinforcement One specimen with bent-up bars
FEMA 273: –Based on flexural capacity, M n, of c 2 +5h slab width, divided by f where c 2 is the column width perpendicular to the applied lateral load h is the overall slab thickness f is the portion of unbalanced moment transferred by flexure according to the ACI 318 design approach.
Peak Lateral Load Capacity Proposed: –Based on flexural capacity of c 2 +5h slab width using 1.25f y, divided by f –Overestimated for heavily reinforced slabs –Neglect reinforcement in excess of = 0.0065 –Discontinuous bottom reinforcement included proportional to development length beyond face of column.
Drift Capacity FEMA 273: –Specify Plastic Rotation Angle beyond Yield point, a
Drift Capacity FEMA 273: –Plastic Rotation Angle, a, depends on V g /V o V g = Gravity shear acting on slab critical section as defined by ACI 318 V o = direct punching shear strength as defined by ACI 318
Maximum Drift Level Proposed Model: –Based on proposal by Hueste and Wight –Maximum drift level related to V g /V o –Based on prior test results for connections failing in punching shear Slab Shear Reinforcement –Connections with adequate shear reinforcement will not experience shear failure –Gradual strength decay after peak lateral load
Residual Strength FEMA: –20% of peak lateral load strength Proposed: –20% of peak lateral load strength for connections with continuity reinforcement –0 for connections without continuity reinforcement
Model Verification Comparison with data from tests performed at other universities Comparison with data from PEER non- ductile tests Verification of the models predicted energy dissipation to the measured energy dissipation
Summary Pre-1970 non-ductile specimens more appropriately referred to as non-continuity connections. Propose conservatism in estimating drift limit for punching shear of such connections. High gravity shear ratio produces non-ductile response. Develop backbone and hysteretic model for interior and exterior connections, both perpendicular and parallel to edge, including various connection parameters. Propose revised limit states for FEMA 273 (356) slab- column connection response.