JEI Structural Engineering

Delegated Design of Glazing Systems

Stewart Jeske, MS, P.E.5/21/21

Learning Objectives

1. Importance to design for building structural movement.

2. Understand design requirements for and limitations of glazing systems.

3. Know some important overlooked areas and what is not working in the delegated design process.

Delegated Design Legal Definition

Is the shifting by contract law of various design responsibilities from the Architect/Engineer of record to the General Contractor.

Who is Delegating? – Structural Engineer of Record

90% of Façade Engineers have little to no understanding/experience in designing a building structure.

What does Delegated Design Include?

Weather Sealant Included?

What does Delegated Design Include?

Vertical Deflection at the bottom of beams

Problematic with stick-built curtain wall limitations

Splice

DL

Structural movement – Live Load Deflection of Spandrel Beams

Columns

SectionElevation

Curtain wallSpandrel

Beams

Spandrel

Beams

30’-0”

ΔLL

DL

WL

DL

Splice

Splice

Dead Load

Anchor

Good reference: https://www.kawneer.com/kawneer/united_kingdom/catalog/pdf/brochures/kawneer_curtain_wall_systems_brochure_p10_p11_april_19.pdf

Dead Load Anchors vs Wind Load Anchors

Dead Load (DL) Anchor – supports weight of curtain wall and wind loads.

Wind Load (WL) Anchors – only supports Wind loads. Has vertical slots.

DL anchor WL anchor

Movement splice

Structural Beam Live Load (LL) Movement

Beam LL Movement= L/360 = (30’x12)/360 = 1.0”

IBC allows Structural Engineers to design building beams for

Live Load Movement of:

• L/360 for Floor beams

• L/240 for Roof beams

Actual beam live load movement is rarely given

in the structural drawings and requires an RFI

Structural Drawings sometimes gives movement info

Most often they give only L/360 or nothing for vert movement.

Dead Load

Anchor

1” Beam LL

Movement

What Vertical Structural Movement Can be Handled? (Manufactured Standard)

Glass Pocket

Maximum

Movement

Potential?

Mullion splice

Dead Load

Anchor

1” Beam LL

Movement

What Vertical Structural Movement Can be Handled? (Stick Built)

Glass Pocket –

1/4” Max

Movement

Potential

What LL Movement Can be Accommodated by Manufacturer Standard Systems?

Manufacturer

Quote

What LL Movement Can be Accommodated by Manufacturer Standard Systems?

1/4” Max Allowed

Manufacturer

Shop Drawing

What LL Movement Can be Accommodated by Manufacturer Standard Systems?

1/4” Max Allowed

Manufacturer

Shop Drawing

What LL Movement is Assumed by manufacturers delegated design engineer?

Assumed??!!

Question: Are Manufacturers doing full delegated structural design required by specs?

Solution 1 -Stacking Stick Built CW- Low Rise (3 or 4 stories)

Movement joints in green

DL at base

Roof Line

2nd FloorWind Load anchors at

Floors

Large joint at Roof Line

for expansion & Structure

movement

Solution 2 – Horizontal w/ Silicone Sheet at each floor line

Silicone Sheet

Large Site Line! –

3” to 4”

What Vertical Structural Movement Can be Handled? (Unitized Curtain Wall)

Chicken Head

– ¾” to 1 ½”

Movement Potential DL Anchor

1” Beam LL

Movement

Stool Trim Detail – WL anchor

Wind load

anchor

movement

Structure

moves

What about sealant failure?

Who has responsibility to design the joint & sealant?

Possible solutions:

Tremco ETA

Joint sealant can

crush only 50%

Head Joint Design For Movement

Design of joints is critical and should not be left for the end of the project during construction!

Ref. Dow Cornings website for sizing formula

Also Reference AISC Design of Façade Connections

Solution Head Detail – Silicone Membrane

Silicone Sheet

EMSeal joint for Curtain Wall

What about Storefront and Structural Movement?

What about Storefront Head Joints

Is this a

movement

joint?

21’- 4”

What about Storefront Head Joints?

CF Steel

framing

Header

spans up

to 16-18 ft

What about Storefront and Structural Movement?

AE SHOWS FIXED/SHIMMED

JOINT – 0” MOVEMENT!

1” Beam LL

Movement

Cold Formed Steel Deflection Track/Slip Track

(only where openings are less than ~ 18’)

Studs w/no slip track (Hung from Structure)

Roof Snow/LL/Wind

Dedicated Wind Girt (Steel Tube – column to column)

(no vertical floor or roof movement)

Dedicated Wind Girt

Structural

Movement?

Roof Snow/LL/Wind

Floor LL

Roof Snow/LL/Wind

Watch out for Canopys

How can you know if you need a receptor head for SF?

1/2” Max Allowed

Some rules of thumb for storefront/receptor need:

If a canopy is overhead – vert. movement likely

Openings longer than 18’ – vert. movement likely

If dedicated wind girts – no vert. movement

Precast tilt up walls – likely no vert. movement

Get an engineer who knows structures

International Building Code:

Story Drift – (lateral movement of building)

BIG ISSUE in Seismic Regions

Typ seismic drift allowed

is about H/50 or .02 x H

So for H= 12’

.02 H = 2.88” of Drift

H

Story Drift – (lateral movement of building)

So say H = 14’, then Drift is = 14’x 12 x .02 = 3.36” Seismic story drift

1) Check delta fall out (clearance)

ASCE 7 min Design Loads for Buildings:

What is fallout:

1) Check delta fall out (clearance)

2) Check for system AAMA

501.6 testing3) Check EOR for actual

Seismic calcs & location

AAMA 501.6 Testing:

Unitized stack joint does well for lateral

Dead load

anchor

movement

At punched openings!

Receptors needed Movement Joint

Fins – care should be taken.

Lateral deflection issues due to wind!

Lateral movement

Must maintain 75% bite

Wind

Corners should be modeled – return loads

Return can pull

away from wall

Wind

Wind

Corners should be modeled

+ and – load combination

+ Wind

- Wind

Jamb Mullion Movement

50% Movement Sealant

100% Movement Sealant

.56 in

Mullion

Moves

Careful!

Running Horizontals

Through

Structural Engineer of

Record may not have

accounted for load at the

jambs

088000 Specifications – IGU’s

Should require submittal based off of ASTM E-1300

Important for SSG systems!

Window Glass

Design Software

088000 Specifications – SSG Systems

SSG (Structural Sealant Glazed Systems)

Structural Silicone “Bite” needs engineering design

Secondary Sealant in IGU needs to be designed – ASTM C1249

Framing Layouts to Avoid

Beam behind

system

required

Differential Movement in Curtain Wall

Cantilever Area

Moves (LL)

Double Mullion

Required with

Movement Joint

Connections to Avoid

A brace is required to

connect to the bottom

½ of a structural beam

Sunshades – care should be taken. Snow loads and ice considered

Snow drift!

Canopies and Handrail Point Supported Analysis showing holes is required

Show difference

Delegated Design of Manufactured Systems

Building Structural Movement Limitations

Lateral Load Limitations

Design of Insulated Glass Units

Delegated Design of Structural Glass

Recommendations for Delegated Design

Questions?

Façade Design/Engineering Services

Curtainwall & Storefront

Structural Glass Systems (Fins)

Glass Stairs & Floors

Glass Railings

All-Glass Entry/Walls

Glass Canopys & Skylights

Zoo/Aquarium Exhibit Glazing

Façade Panel Systems

J-Edge Anchor System – Tech Rep.

New Pour Stop with Anchor

Eliminates Field welding

Eliminated slab embeds

Saves Time & Costs

Free presentation!