Seismic Performance of Architectural Precast Panel Systems Drift Compatibility of Corner Joints
Seismic Performance of Architectural Precast Panel Systems Section Objectives Panel System Seismic Drift Behavior Code Provisions and Current Practices for Designing Corner Joints Proposed Ductile Fuse Connection to Allow Reduced Joint Size Experimental Results
Panel System Drift Behavior FLOOR LEVEL FLOOR LEVEL FLOOR LEVEL FLOOR LEVEL FLOOR TO FLOOR PUNCHED WINDOW PANELS A WINDOW HEAD TO WINDOW HEAD WALL PANELS TYPICAL CLADDING CONFIGURATIONS B SPANDRELS WITH COLUMN COVER INFILLS C
Panel System Drift Behavior BUILDING CORNER WITH LARGE JOINT PERPENDICULAR PANEL AT CORNER COLUMN PANELS WRAP CORNER PERPENDICULAR PANEL AT CORNER FLOOR TO FLOOR PUNCHED WINDOW PANELS A WINDOW HEAD TO WINDOW HEAD WALL PANELS B SPANDRELS WITH COLUMN COVER INFILLS C
Panel System Drift Behavior LOCATIONS OF PANEL BINDING COLUMNS TILT TO FOLLOW SUPPORTS DIFFERENTIAL MOTION BETWEEN PANELS AND SUPPORTING STRUCTURE AT LATERAL CONNECTIONS A B C
Panel System Drift Behavior LOCATIONS OF PANEL BINDING COLUMNS TILT TO FOLLOW SUPPORTS A DIFFERENTIAL MOTION BETWEEN PANELS AND SUPPORTING STRUCTURE AT LATERAL CONNECTIONS B C
Panel System Drift Behavior REFLECTED CEILING PLAN PANEL CONFIGURATION A (PANEL CONTACT) COULD BE 3 OR MORE! ARCHITECTS DON T LIKE THIS SEISMIC JOINT
Panel System Drift Behavior REFLECTED CEILING PLAN PANEL CONFIGURATION A (PANEL CONTACT) WE CAN ALLOW MOVEMENT BY BENDING OF STEEL IN THE CORNER CONNECTION
Panel System Drift Behavior REFLECTED CEILING PLAN PANEL CONFIGURATION A (PANEL CONTACT) WHEN THE PANELS CONTACT THE PLATE BENDS
Consequences of Panel Collisions Structure motion does not stop at first binding continues on with or without panel Non-ductile connections may fail jeopardizing panel stability and attachment to structure. Induced connection forces may torque connected beams or columns Result is not simply aesthetic concrete spalls of panels
Code Provisions for Panel Joints ASCE 7-10 Section 13.5.3 (SDC C, D, E, or F)
Current State of Practice Corner Joints Size Joint to avoid collision under full inelastic drift, Dp (or Dpi) Disregard effects of sealant/caulking. (Assume compresses to zero width) Design connections for inertial forces only Take advantage of geometry of miter joints to reduce miter joint width
Current State of Practice Corner Joints Butt Joint Miter Joint
Current State of Practice Corner Joints Dp = Seismic Relative Displacement due to full inelastic story drift Inelastic drift = 5 to 5.5 times drifts calculated from elastic analysis of building
Performance Based Approach Ductile Fuse Connection 1. Intentionally undersize joint as follows: Minimum size = maximum of: 0.50 (13.5.3) Wind Deflections Dp(elastic) = Dp/Cd Precast constructibility (tolerances) usually ¾ minimum 2. Design connection with a ductile yielding element in the load path Weak axis flexure of steel elements ideal 3. Design Connection elements for traditional inertial forces. 4. Calculate expected plastic capacity of fuse. 5. Verify fuse capacity is weaker than all elements in connection load path.
Ductile Fuse Connection Load Path 1. Headed Stud Anchors 2. Headed Stud Welds 3. Embedment Plate with Nut 4. Threaded Rod 5. Plate Washers 6. Cantilevered Plate with oversized holes (Ductile Fuse) 7. Welds to stand off plates and embed 8. Embed plate in column 9. Welds to headed studs. 10. Headed Stud Anchors
Inertial Force Requirements: Body Force and Fastener Force Fasteners = non-ductile attachments, welds, anchorages Body of connections = ductile elements such as plates, angles, steel shapes, yielding rebar. Fastener force = 3.13 x Body force
Inertial Force Requirements: Body Force and Fastener Force Sds = 1.0. Example Force Summary Component Component Name Type F p # 1 Headed Stud Fastener 1.50 W p 2 Stud Weld Fastener 1.50 W p 3 Embed Plate Body 0.48 W p 4 Threaded Rod Fastener 1.50 W p 5 Plate Washer Body 0.48 W p 6 Cantilever plate (ductile fuse) Body 0.48 W p 7 Plate Welds Fastener 1.50 W p 8 Embed Plate Body 1.50 W p 9 Stud Welds Fastener 1.50 W p 10 Headed Stud Fastener 1.50 W p
Ductile Fuse Design 1. Determine Mp-Expected (expected plastic moment capacity) Mp-expected = 1.1 Ry Fy Z Plastic Modulus Ratio of Expected Yield to Specified Yield Stress = 1.5 for A36 Steel Strain Hardening Coefficient 2. Determine P-expected from fuse Verify P-expected < φrn (all other elements)
Ductile Fuse Design Pmax (fuse) = 5.85 kips Failure Check Component Demand Capacity mode Results Concrete P breakout u =P max =5.85 kips ϕp n =16.0 kips OK Anchor P tension u =P max =5.85 kips ϕp n =39 kips OK Panel embed Headed stud P weld fracture u =P max =5.85 kips ϕp n =14.3 kips OK ϕm Plate flexure M u =P max L/4=8.78 kip-inch n =14.1 OK kip-inch Rod Tension P u =P max =5.85kips ϕp n =25.8 kips OK Plate weld P u =P max (16/4.5)= ϕp fracture 20.8 kips n =27.8 kips OK Column Embed Concrete breakout Anchor tension T u = P max (16/6)=15.6 kips ϕp n =17.3 kips OK T u = P max (16/6)=15.6 kips ϕp n =42.9 kips OK
Experimental Results
Findings Fuse Connections performed very well Measured forces from load-cell were in the expected range Mitered joint panels engaged both panel cracking and fuse flexure Butt joint (return) panels were stiffened by the return leg and activated the fuse for more of the drift Under-sized joints with a ductile fuse connection are a viable tool in the designer s toolbox.
Thank you Elide Pantoli will discuss the Design Guide that will be published soon