PRECAST CONCRETE CONNECTIONS - US PRACTICE

Larbi Sennour, PhD, SE President Consulting Engineers Group, Inc. SPEAKERS

Precast Connections 3 General Types Wet Connections Semi Dry Dry

Wet System - Definition SPLICED REINFORCING P/C P/C PIP

Wet System - Connection

Semi Dry System - Definition SPLICED REINFORCING P/C P/C PIP CAVITY IN PRECAST

Semi Dry - Definition Emulation of CIP Forming using precast Self supported Cast in-situ

Semi Dry Beam/Column Joint COLUMN SHEAR KEY AREA THAT CAN BE USED FOR MOMENT FRAME ANALYSIS BEAM TROUGH

Semi Dry Beam/Column Joint SLIM SLEEVE SLIM SLEEVE

Semi Dry Beam/Column Joint SLIM SLEEVE

Semi Dry Beam/Column Joint MOMENTS SHEAR TENSION/COMP.

Semi Dry Beam/Column Joint SLIM SLEEVE

Dry System - Definition MECHANICAL CONNECTION P/C P/C

Dry System - Definition Spliced Sleeved Welded Bolted

Dry Spliced Procedure Cast splice sleeve with precast Cast bar in foundation at proper location Erect precast element with projected bar in the sleeve Pump grout from bottom port to upper port

Spliced - Example

Spliced - Design Design considerations Fully emulates CIP Develops 150% f y Tested for cyclic loading Same design and requirements as CIP Used in all seismic zones

Moment Resistance Spliced - Design P DL T u M u C u d T u M d u P ( 0.9 0.2S ) DL DS 2

Spliced - Design Design Spectrum Used in the US S DS S a S T D1 S a S T 2 T D1 L S D1 T o T s 1.0 Period T T L

Moment Resistance Spliced - Design P DL V u V u mj(a s f y + P DL ) m Shear Friction Coefficient f Shear Strength Reduction Factor

Spliced - Architectural Wall

Spliced - Framing

Principal Dry Sleeved

Dry Sleeved Procedure Cast rebar spliced or extend bar in precast element Cast bar sleeve in connecting member or core drill Fill sleeve with grout Erect Panel

Dry Sleeved

Dry Bolted Procedure Base plate is cast into precast element Base plate is anchored to develop tension force Bolts are cast into the lower element Connection is achieved by bolting

Dry Bolted Limited Fixity Can be modeled by calculating the rotation stiffness Depends on soil capacity Usually assumed pinned except for erection as semi fixed.

Dry Welded

Dry Welded Transfer diaphragm loads to walls Transfer shear to increase capacity Transfer loads to each other and foundations

Dry Welded - Analysis Diaphragm Shear Out of plane lateral loads

Dry Welded - Analysis Out of plane lateral loads Uplift tension or compression from overturning moment Diaphragm shear

Dry Welded - Analysis Horizontal shear also known as VQ/I

Connections - Resources Resources for Welded Connections PCI Design handbook 7 th Edition Has the theoretical background on the macro level PCI Connections Manual Has the design example of almost every type. Deals with the practical aspect of design fib Connections Has the theory for connection behavior down to the micro level

CONNECTION DESIGN METHODOLOGY

Shear friction Shear Friction Dowel Effect Combination c s w s s

Strut & tie models

DESIGN & MODELING Design assumptions Design for worst case scenario Satisfy load resistance in all its aspects Limit displacements and allow movements Modeling Determine and use actual Behavior Testing results if available should be incorporated Remember: You assumptions should always reflect a conservative behavior to give you a reasonable factor of safety.

Design Assumption DESIGN ASSUMPTIONS

ACTUAL BEHAVIOR Actual Behavior Determine the spring constant K factor

TYPICAL HARDWARE USED IN THE US PRACTICE

Hardware Steel Shapes A36 Plate A283 Tubes A500 Stainless A666 Type 304 Governed by AISC

Hardware Anchors Provide anchorage into concrete Headed studs HCA Deformed bar anchors DBA Rebar Governed by ACI 318 Appendix D Also PCI Design Handbook

Headed Concrete Anchors Specify AWS D1.1 Type A or B Automatic welding process Can be stick welded Shallow anchorage 100mm, 150mm common 200mm maximum length Diameters 6mm to 20mm 12mm most common

Headed Concrete Anchors Failure modes Steel yield Concrete breakout Supplemental reinforcement Enhances performance

Deformed Bar Anchors Similar to short lengths of rebar AWS D1.1 Type C Weldable Automatic weld process or stick weld Deeper anchorage into concrete Rebar A706 is weldable A615 can be welded have to know chemistry

Hardware Bearing Pads Chloroprene AASHTO grade Random Oriented Fiber No ASTM Reinforced Cotton Duck AASHTO

Hardware Shims Generally High Density Plastic No ASTM Thicknesses 1.5 to 12mm Slide bearings Steel Add if stack > 40 to 50mm Tack weld

Hardware Bolts Generally A307 Not well defined mechanical properties A36 Threaded rod Better mechanical properties Used in sliding connections Snug tight Upset threads Be careful with tack welds

Bolts Sliding connections Volume change Drift Field tolerances Slotted holes Oversize holes

Bolts A325 Bolts high strength bolts Generally used in structural steel construction Generally pretensioned in steel construction Rarely used in precast connections

Hardware Welding AWS D1.1 Structural Welding Code AWS D1.4 Structural Welding Code Reinforcement Weld types Matching metals

Welding Low hydrogen weld rod Sensitive to moisture Ovens on site E7018 common weld rod

Welding AWS D1.1 Environmental conditions No welding if Rain or surface moisture High wind velocities Inclement conditions Preheat below 32 F Lehigh Welding Study Surface moisture driven off by weld heat Acceptable profiles to 35 mph wind No preheat to 0 F

Proprietary Inserts

Post-installed Anchors Expansion bolts Depend on mechanical action Design by ACI 318 Appendix D Requires qualification by ACI 355.2

Post-installed Anchors Adhesive anchors Depend on chemical bond Currently depend on Manufacturers ACI 318-11 added adhesive anchors Will be Qualification standard Will be certified installer program Will be inspection requirements

Adhesive Anchors Fire resistance Overhead installations Resin creep with sustained loads Age of concrete

Connections - Summary Summary Wet connections are mostly based on emulation very useful for moment connections and splicing Semi dry connections are also based on emulation but eliminate the need for forming Dry connections are the most widely used connections. They have limited capacity on multidirectional force systems

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