Deconstructable Steel Concrete Shear Connection for Sustainable - - PowerPoint PPT Presentation

Deconstructable Steel‐Concrete Shear Connection for Sustainable Composite Floor Systems

Lizhong Wang, Jerome F. Hajjar Department of Civil and Environmental Engineering Northeastern University Clayton Brown, Mark D. Webster Simpson Gumpertz and Heger, Inc.

“Mechanics for Sustainable and Resilient Systems”

Introduction DfD Floor System Conclusions Clamp Connector Behavior

Image from US Energy Information Administration (2011)

Introduction

Green buildings

• Material manufacture
• Environmentally friendly, renewable and low

embodied energy materials

• Use phase
• Efficient heating, ventilating and lighting

systems

• Adaptation or reconfiguration
• End of life
• Minimum amount of waste and pollution
• Reusable and recyclable materials

Material flow of current buildings

Extraction Manufacturing Construction Operation Deconstruction Design for Deconstruction Disposal

End-of-life of Construction Materials

End-of-life of construction materials

Image from SteelConstruction.Info

Introduction DfD Floor System Conclusions Clamp Connector Behavior

Composite Floor System in Multi-Story Frames

• Conventional composite floor systems are cost-effective solutions for multi-story buildings.
• The integration of steel beams and concrete slab prevents separation and reuse of the

components.

Precast concrete plank Cast-in channels

Steel beam

Deconstructable composite beam prototype Clamps Tongue and groove side joint Bolts a) Plank perpendicular to the steel beam 24'' 6'' 12'' 6'' 6'' b) Plank parallel to the steel girder

12'' 12'' 12'' 12'' 12'' 6''

Precast concrete plank cross section Introduction DfD Floor System Conclusions Clamp Connector Behavior

Design for Deconstruction: Prototype Structural System

Introduction DfD Floor System Conclusions Clamp Connector Behavior

30' 30' 30' 30' 30' 30' 10' 10' 10' 10' 10' 10' 10' 10' 10'

Typical floor plan for DfD system Gravity column Girder Beam Beam plank Girder plank

Design for Deconstruction: Experimental Testing Program

• Pushout test: evaluate a wide range of parameters and formulate strength design equations
• Beam test: study the clamp connector behavior in a realistic manner
• Precast connector test: test the strength and ductility of the plank connectors under tensile

and shear loading

• Diaphragm test: investigate the in-plane seismic behavior of the composite floor system

Beam test Diaphragm test Introduction DfD Floor System Conclusions Clamp Connector Behavior Pushout test Precast connector test Fixed side Free side

Pushout Tests: Experimental Test Setup

Concrete block Concrete strong floor Reaction angle L8x6x0.5 Embedded channel Clamp 24'' 36'' Stiffeners WT 4x17.5 Steel base plate Teflon sheet 6''

Elevation view

24'' 8'' Reaction angle Embedded channel Clamp Anchor 12'' 24'' 12'' 48'' 7'' 54'' 3'' 4'' 40'' 4'' 3'' 6'' 3'' 9'' Steel plate 8'' 7'' Short-slotted holes

Plan view Introduction DfD Floor System Conclusions Clamp Connector Behavior

Limit States for Cast-in Channels

• Tensile loading
• Shear loading

Introduction DfD Floor System Conclusions Clamp Connector Behavior Bolt failure Local flexure of channel lips Concrete cone failure Bolt failure Concrete edge failure Local flexure of channel lips

Pushout Tests: Experimental Test Matrix

Name Number

• f

channels Rebar configuration Loading Pretension Shim Intended Failure modes 2 3 Light Heavy Monotonic Cyclic Small Large Yes No Concrete failure Channel lips failure Slip of clamps 2-RH-LM- PS-SN       2-RL-LM- PS-SN       2-RH-LM- PL-SN       2-RH-LM- PS-SY       2-RH-LC- PS-SN       2-RH-LC- PS-SY       3-RH-LM- PS-SN       3-RH-LM- PS-SY      

Introduction DfD Floor System Conclusions Clamp Connector Behavior

Pushout Tests: Computational Simulation

Boundary conditions and load application

Reaction angle surfaces Concrete strong floor Symmetric BC Loading surfaces Restrained from

• verturning

Loading process

• Pretension in the bolt is obtained by assigning thermal coefficient to the shank and

decreasing the temperature.

• The steel beam is then loaded in the axial direction using displacement control.

Introduction DfD Floor System Conclusions Clamp Connector Behavior

Interaction

• Frictional coefficient: 0.3, except for the contact between the plank and the concrete strong

floor, which is frictionless

• Rebar: embedded in the concrete plank

Pushout Tests: Constitutive Relations

• Concrete damaged plasticity model
• Failure mechanism: tensile cracking and compressive crushing
• Capture stiffness recovery due to crack opening and closing under cyclic loading
• Steel beam, rebar and cast-in channels: elastic-perfectly-plastic material
• Bolts: A325 bolts (Grade 8.8 bolts)

Material constitutive model

Introduction DfD Floor System Conclusions Clamp Connector Behavior

C30 concrete compressive behavior Bolt material stress-strain curve

100 200 300 400 500 600 700 800 0.05 0.1 0.15 0.2 0.25 Stress (MPa) Strain 5 10 15 20 25 30 0.005 0.01 0.015 0.02 Stress (MPa) Strain

Pushout Tests: Computational Simulation Results

Introduction DfD Floor System Conclusions Clamp Connector Behavior

• 200
• 100

100 200 300 400 500 600

• 15
• 10
• 5

5 10 15

2-RH-LM-PS-SN 2-RL-LM-PS-SN 2-RH-LM-PL-SN 2-RH-LM-PS-SY 2-RH-LC-PS-SN 3-RH-LM-PS-SN

Displacement (mm) Load (kN)

Bolt bearing Bolt bearing Concrete crushing Bolt bearing Slip Bolt bearing

Pushout Tests: Limit States Observed in Computational Simulation

Slip of clamp and shim Local yielding of channel lips Compressive damage in the concrete plank with three channels Bolt bearing against the channel Introduction DfD Floor System Conclusions Clamp Connector Behavior

Conclusions

• A new deconstructable composite floor system, consisting of steel framing, precast

concrete planks and clamping connectors, is presented.

• The clamping connector has a relatively high ultimate strength and behave ductile;

therefore, they can be used as connectors in composite beams.

• Using shims for thin flange sections reduces the frictional strength slightly.
• As a result of damage accumulation in concrete, the strength of the connector reduces

under cyclic loading. Three channel configuration fails by concrete crushing.

Introduction DfD Floor System Conclusions Clamp Connector Behavior

Acknowledgement

• National Science Foundation
• American Institute of Steel Construction
• Northeastern University
• STReSS Laboratory at Northeastern University
• Simpson Gumpertz and Heger, Inc.

Questions?