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New Technologies in Steel Buildings

Review of material presented by Dr G Charles Clifton

Canterbury Earthquakes Royal CommissionMarch 14th 2012

Sean Gledhill

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Design Focus Previously Life Safety, not building continuity

Current Practice Member design for between 1/6 and 1/3 of theexpected earthquake. Ductility = damage.

Structural damage Not addressed in design. Damage = repair

Non structural damage Need to limit drifts, keep ductility low

Code Compliance Doesnt control or limit damage

Reality Some damage / demolition / repair / losses?

Owner perception Need to gain some certainty on asset performance?

Cost 1 - 4% additional capital cost

Steel structures Few buildings built with damage mitigation features

Solution Change philosophy to apply latest research

Why move to low damage steel buildings

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Cast Study Low Damage Design of Te Puni Student Village

Victoria University of Wellington requested inclusion of damage mitigationdesign in new student accommodation project.

Three Buildings, up to 11 storeys in height

Structural system consists of steel frame construction with concrete floors, clad ina lightweight-faade with lightweight roofs

Lateral bracing systems consist of Moment frames in longitudinal direction andCoupled Concentric braced frames in transverse direction

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The building during construction

Tower Building (foreground) and Edge Building

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Project goals

Drivers for low damage selection:

Facility to function as a disasteradministration centre with nominal repair

Suitability to multi storey steel buildings

Speed of construction / buildability

Economy of damage mitigation system Limit primary structural member damage

Availability of components

Sustainability for the future

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Research: Basis of innovative ideas

University of Auckland, University ofCanterbury research papers

Moment Frames - Sliding Hinge Joints

Rocking Steel Frames - CBFs A tensionlimited hinge

Coupled in plane concentric Braced Frames

Localised and controlled damage in jointsrather than in primary members

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The innovation

Transverse (short direction system) Bracing System (Innovation 1)

Rocking coupled concentrically braced steel frames (CBFs) with a tension limitedfoundation hinge, consisting of prestressed Ringfeder Springs and friction plates.

Longitudinal (long direction) bracing System (Innovation 2 & 3)

Steel Moment Resisting Frames (MRFs) with sliding hinge joints, a new verticallyorientated friction plate joints to provide base column hinge protection.

We developed and refined a new system for damage mitigation system for multistorey steel framed buildings, including:

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Innovation 1: Transverse Bracing System

Before/After During

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Innovation 1: Ringfeder / Friction Plate Hinge

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Site photo

Coupled CBF Frames with central SHJ

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Site photo

CBF Frame / Ringfeder Housing at foundation connections

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Site photo

Installed Ringfeder Springs work in progress

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Innovation 2: Longitudinal Bracing System Sliding Hinge Joints

Moment Frame with Sliding Hinge Joints Sliding Hinge Joint

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Sliding hinge joints Limits floor slab from damage

Sliding Hinge Joints Invented

by Dr Charles Clifton(UOA) whilst at

HERA

Pivots at flange/beam connection via gap

Isolates frame movement from crackingconcrete floors

Reduces foundation uplift loads

Tendency to self-center after design

earthquake

20mm isolationaround columns

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Site photo

Moment Resisting Frame Column with Sliding Hinge Joint

G G 000 5

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Innovation 3: Longitudinal Bracing System Column Protection Feature

Column Hinge Protection in MRFs Columns

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Photos

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Photos

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Photos

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Photos

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Photos