Silicon Structural Glazing

Structural Glazing of 30 1

Dow Corning.

Silicone Structural Glazing.

Structural Glazing 2

Silicone Structural Glazing.

What is Silicone Structural Glazing ?

Why use Silicone Structural Glazing ?

Basic Designs and History ?

Structural component considerations.

What is the Dow Corning approach ?


What is Silicone Structural Glazing.

A type of Curtain Wall, that adhesively bonds glass, IG units, panels of metal, panels of stone.

To a structural frame of a building with medium to high modulus silicone sealants specifically developed, tested and qualified for structural glazing.


Structural Loads.

Live Load.

- negative and positive wind pressure.

- intermittent tensile stress.

Dead Load.

- Due entirely to the weight of the panel.

- Load is constant and generally in shear.


Why Use Silicone Structural Glazing ?

Historically. - Aesthetics, Upgrading of existing facades.

Today.

Aesthetics, Upgrading of existing facades.

Simplified CW

Improved acoustic performance

Allows even heating and cooling of the glass.

Improved weather sealing performance.


Basic Designs and History.

All Glass or T.V.S = total vision system.

First system erected 1966

2 sided SSG or Ribbon window.

First system erected 1970

4 sided SSG or Total Wall

Supported 1971 (live load)

Unsupported 1979 (Live and dead load)


Structural Glazing Component Considerations.

The substrates.

The supporting frame.

The glazing.

The silicone structural sealant.


Authorized Substrates.

Anodized aluminum.

Polyester Powder coated aluminum.

PVDF coated aluminum.

Stainless steel.

Glass

Stone


Forbidden Substrates.

Mill finish aluminum.

Mild steel, Galvanized steel.

PVC.

Wood.


The Supporting Frame.

The curtain wall manufacturer is responsible for the structural integrity of the support frame.


The Supporting Frame - Coatings.

Anodized Aluminum. - The degree of sealing has an impact on the adhesion of the structural sealant. We recommend that the degree of sealing should be between 1 and 2 according to ISO 2143.

Polyester Powder Coating and PVDF coating. This is dependent upon the adhesion of the coating to the aluminum. In Europe QUALICOAT certification required.


The Glazing.

Single Panes - no problem.

Insulating Glazing - special considerations required.


The Glazing - Insulating Glass Units.

The hermetic sealant is often a structural seal.

Dead load support usually required.

Deflection of the glass can be significant with changing air pressure and symmetry of unit.

Water accumulation must be avoided.

Only silicone edge seals with a primary butyl seal can be used.


Silicone Structural Sealants.

Why Silicone ?

Unsurpassed weather-ability and UV resistance.

High level of adhesion and good movement capability.

Wide service temperature range. -40 to +150 degrees Celsius.


Dow Corning products for SSG.

STRUCTURAL GLAZING SEALANTS.

1 Part - DC 895.

2 Part - DC 983 and DC 993.

INSULATING GLASS SEALANTS.

1 Part - DC 3793

2 Part - DC 3362

WEATHER SEALANTS.

DC 797 AND DC 897.


Dow Corning 895 structural sealant. One part - easy to use

Neutral curing.

Generally no primer required.

Compatible with laminated glass.

Compatible with most coated glass.

Ideal for re-glazing.

The Disadvantage is moisture curing- Long cure times.


Dow Corning 993 structural sealant.

2 part

Neutral curing

Suitable for factory glazing

compatible with laminated glass

compatible with most coated glass

Fast cure time - faster turn around of units.

Curing depth not limited.

High resistance - therefore less material required.

Disadvantage - mixing equipment required.


The Dow Corning Approach.

Project Check List.

Drawing Review.

Designing the Joints - Calculations.

Adhesion and Compatibility testing.

Prepare Method Statements.

Quality Control.

Factory / Site Visits.


Project Check List.

Required for warranty purposes.

Identifies who s involved in the project.

Gives details of wind loads etc.


Drawing Review.

Dow Corning will make comments and suggestions on all sealant details.

Identifies components required for testing.


Designing the Joints.

Thickness of the SG sealant

Bite of the SG sealant

Height of the IG secondary seal.


Designing the Joint - Calculations

Designing the Structural silicone bite. - live load

only.

Based upon Timoshenko’s plate theory.

Bite = Wind (Pa) x shortest side of panel x 0.5

Design Load of the sealant.

Wind is given as Max wind load in a given time period.

Design strength of DC sealant is 140,000 Pa


Example of live load.

4 sided supported design where :

Glass size = 1.2 x 1.8 metres

Wind load = 2,000 Pa

Bite = 0.5 x 1200 x 2000

140,000

= 9 mm


Designing the Joint - Calculations.

Dead Load

Silicone is supporting the weight of the panel.

Assume that the support frame is rigid.

Bite = ______Weight of Glass__________

( perimeter of glass x sealant design strength)

Design strength for DC 895 is 7,000 Pa

Design strength for DC 993 is 15,000 Pa


Designing the joint. - safety factors.

Dow Corning silicone , safety factor is 8

Taking into account all elements SF is 6

Standard curtain wall system SF is 3


Adhesion Tests.

Samples tested to a modified ASTM C794 - 93

Initial testing.

Aging test.

Takes 3 weeks in total.


Compatibility Test.

Need to check all materials that the sealants comes into contact with i.e. gaskets, setting blocks, etc.

There must be NO loss of adhesion of the sealant to the glass, and NO dis-coloration of the sealant.

Takes 21 days of UV exposure.


Method Statements

Surface Preparation.

Priming.

Sealant type.

Adhesion.

Compatibility.


Quality Control.

The applicator of the structural sealant MUST carry out his own internal tests as the project is being carried out and to RECORD the results.

These include adhesion tests, record lot numbers of

sealants used with what frame, dates, cure times of

the sealant etc.


Conclusion.

Structural Glazing is a partnership between the Designer, the Curtain Wall company, the Glass manufacturer and Dow Corning.

If we all work together the outcome will be a successful project.

Silicon Structural Glazing

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