USE OF HEADED REINFORCEMENT IN BEAM - COLUMN JOINTS John W. Wallace, Ph.D., P.E. Associate Professor, UCLA Scott W. McConnell, M.S., P.E. Structural Engineer, Schoor-DePalma, NJ National Science Foundation Headed Reinforcement Corporation ERICO Incorporation

HEADED REINFORCEMENT ? Plate Anchor Rectangular/Round Threaded/Friction Weld Area = 5 to 10 Bar Area Beam-Column Joints Standard Hooks Ease of Fabrication & Placement

WHY HEADED REINFORCEMENT ? Congestion/Fabrication/Placement

AVAILABLE INFORMATION Anchorage/Beam-Column Joints l UCLA & Clarkson University Wallace, McConnell, Gupta Reports/ACI Papers (1994, 1997, 1998) Also Yu (2001) l University of Texas, Austin Jirsa, Devries, Bashandy Ph.D. Dissertations (1996), ACI Paper (1999) l University of Kansas McCabe, Wright, Wu (Reports, 1997)

PROJECT OVERVIEW EXTERIOR ROOF & CORNER JOINTS EXTERIOR INTER- STORY JOINTS

TEST SETUP Exterior Roof Connections

SPECIMEN DETAILS Exterior Roof Connections

DESIGN REQUIREMENTS Exterior Roof Connections Strong Column - Weak Beam (352-01) Joint Confinement Reinforcement (352-01) Joint Shear Stress Limits (352-91)   2 (1.1 Test).1 / beamcolumn MM (test) 51.1/ f/f )1/(3.0 ',, y ' c   dreqshprovidedsh chgcsh AA AA A 0.1 to 5.0 / kips 140 to 75P ) 60)(25.1)( ( kips 140)"5.13)("16((psi) 4000 )12)(85.0( 2    nu beamsu n VV ksiinAV V  

DESIGN REQUIREMENTS Exterior Roof Connections l Anchorage Requirements – Tension (318 Eq. 21-5, ) – Compression (318 S12.3) 1.55 to )/14.23 to (18 / 23.14(psi) f/ 900 (0.75) (psi) f/ 1200 (psi) f/f 02.0 ' c ' c ' cy    dprovided bddbd db ll ddll ddl 1.5 to /22) to 18( / 14.6 (psi) f/925 (psi) f 65/ f ' c ' c   bbdh provided bbbydh ddll dddl

LOAD HISTORY Exterior Roof/Inter-Story Connections

Specimen Damage Exterior Roof Connections KJ16 - Top Bar Pull-out

REINFORCING DETAILS Exterior Roof Connections Top ViewSide View Restraint Bars

Moment-Rotation Response Exterior Roof Connections

MEASURED REBAR STRAINS Beam Top Bars Within the Joint

TEST SETUP Exterior Inter-Story Connections

SPECIMEN GEOMETRY Exterior Inter-Story Connections

DESIGN REQUIREMENTS Exterior Inter-Story Connections Strong Column - Weak Beam (352-01) Joint Confinement Reinforcement (352-01) Joint Shear Stress Limits (352-91)   2 (1.7 Test).1 / beamcolumn MM (test) 17.1/ f/f )1/(3.0 ',, y ' c   dreqshprovidedsh chgcsh AA AA A 80.0/ kips 207 ) 60)(25.1)( 79.04( kips 260)"18)("18((psi) 4000 )15)(85.0( 2    nu columnu n VV VksiinxV V  

DESIGN REQUIREMENTS Exterior Inter-Story Connections l Anchorage Requirements – Tension (318 Eq. 21-5, ) – Compression (318 S12.3) 352)per ( /13 / 14.6 (psi) f/925 (psi) f 65/ f ' c ' c   bbdhprovided bbbydh ddll dddl /14.23 / 23.14(psi) f/ 900 (0.75) (psi) f/ 1200 (psi) f/f 02.0 ' c ' c ' cy    dprovided bddbd db ll ddll ddl

Beam End Rotation Exterior Interstory Connections BCEJ1 - Drift Level 6% Potentiometer

MOMENT-ROTATION Exterior Inter-Story Connections

Specimen Damage Exterior Interstory Connections BCEJ1 - Drift Level 6% Bottom Bar 6%

Compression Bar Push-Out Exterior Inter-Story Connections l Beam Moment Capacity Compression Steel l Slight Pushout Occurs Redistribution From Steel to Concrete l Minor Reduction in Beam Moment Capacity l Note - Compression l d Satisfied by Checking Tension l d

Summary Observations Headed Bars in Beam-Column Joints Required Embedment Length Kansas Study:l d = 0.60 l dh Texas Study: l d = ( ) l dh UCLA/Clarkson Large-Scale Study: l d = 0.82 l dh Other Design Requirements Flexural Strength Ratio: M column /M beam > 1.2 Joint Shear Emdedded Bars Must Be Shoved To Back of Joint Practical Recommendation for Emdedment l d = 0.75 l dh

CONCLUSIONS Beam-Column Joint Tests – Six Specimens (3 Exterior, 3 Roof) – Small Cover/Need for Transverse Steel – Push-Out of Compression Bars ACI Committee 352 Draft Report – Modified to Allow Use of Headed Bars Research Needs - Cyclic Loading – Cover/Transverse Reinforcement – Multiple Layers of Reinforcement