New SEAOC Documents on the Structural Design of Rooftop Sol PowerPoint Presentation, PPT - DocSlides

Slide1

New SEAOC Documents on the Structural Design of Rooftop Solar Arrays

November 1, 2012

Ronald

LaPlante

, S.E.

Division of State Architect – State of California

Slide2

New SEAOC PV Committee Reports

Available for free download for members at:

http

://

www.seaoc.org/seasecure/member.html

Slide3

Outline

PV Committee and Scope

SEAOC Solar PV Wind Report

SEAOC Solar PV Seismic Report

Next

steps

What is DSA doing?

Slide4

PV Committee and scope

Slide5

Formation of Committee

Formed in September 2011 as subcommittee of SEAOC Wind Committee

Composed of:

Structural Engineers

Code Enforcement Agencies

Wind Tunnel Experts

Solar PV Industry Members

NCSEA & ASCE 7 Wind Committee Members

SEAOC Seismology Members

Slide6

Solar Photovoltaic Arrays Types

Flat Roofs

Carports

Ground Mount

Sloped Roofs

Parking Garages

Slide7

Which Wind Loading Provisions Apply?

What about other installations?

ASCE

7-05

Open

Buildings (ASCE 7-05 Figure 6-18,19)

Enclosed Buildings –

C&C

(ASCE 7-05 Figure 6-11)

ICC AC 428

Slide8

Which Wind Loading Provisions Apply?

Flat Roofs – not flush mounted

Ground Mount - Sheltering

Parking Garages

Pitched Roofs – not flush mounted

Slide9

Wind Tunnel Procedure

ASCE 7

Wind Tunnel Procedure (WTP)

What’s an appropriate wind tunnel study?

ASCE 7 WTP is written for specific building modeling, not generalized buildings with solar panels.

Should the WTP be peer reviewed?

Is there a minimum wind load?

Does building need to be modeled?

Roof zoning?

Etc…

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PV2

report on wind design

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Goals for Solar PV Wind Report

Develop report to address wind design provisions for low-profile solar PV arrays on flat roofsEstablish wind design coefficients similar to those in ASCE 7 figures

Slide12

Goals for Solar PV Wind Report

Define Effective Wind Area for unique aspects of solar PV arraysDefine minimum Wind Tunnel Procedure modeling requirements and minimum design loadsExample Problem

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SEAOC Solar PV Wind Report

Understanding wind flow environment on roof

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SEAOC Solar PV Wind Report

Wind tunnel data from CPP & UWO

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SEAOC Solar PV Wind Report

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SEAOC Solar PV Wind Report

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SEAOC Solar PV Wind Report

Roof zoning for open elements on roof different than C&C

Components & Cladding

Solar PV Arrays

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SEAOC Solar PV Wind Report

Geometry selected based on most common application and supported by data

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SEAOC Solar PV Wind Report

Defined roof zones similar to ASCE 7Clarified steps, angled corners, reentrant corners

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SEAOC Solar PV Wind Report

GCrn curves similar to ASCE 7 methodologyUses normalized wind area instead

Interpolate

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SEAOC Solar PV Wind Report

Factor to increase loads at perimeter of array

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SEAOC Solar PV Wind Report

Wind

t

unnel model requirements

Promote consistency

Model array on building, must consider:

Roof zones, effective wind area, panel geometry, tilt angle, spacing, height above roof, roof shape

ASCE 49-07

“Wind Tunnel Testing for Buildings and Other Structures

”

Minimum design wind loads from wind tunnel

50% of values in

Figure (no arbitrary 10

psf

minimum)

65% of values in Figure if doesn’t meet geometry in Figure

Lower values allowed if qualified peer review

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SEAOC Solar PV Wind Report

Example Problem in Appendix

Aid in interpretation and application of method

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SEAOC Solar PV Wind Report

Example Problem in Appendix

Provides wind pressures on each panel of the array

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PV1

report on seismic design

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Contents

Performance objectives

Building SFRS

Attached arrays

Unattached arrays

Seismic displacement

Prescriptive displacement

Friction testing

NLRH analysis or shake-table testing

Slide28

Performance Objective

Life Safety per IBC 101.3Stay on the roofStay on supporting membersDo not block roof drainageDo not cause electrical fireDo not impede fire-fighter roof accessOther damage that would endanger life

Slide29

Existing Building Structures

Represent 95%+ of commercial solar installationsDesign per IBC chapter 34Increase lateral loads by no more than 10%Increase gravity loads by no more than 5% (concentrated loads)Where panels are placed, roof live load is not assumed to act.

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Attached Arrays

Use ASCE 7-05 Chapter 13 for seismic demand (Fp)How to establish ap and RpSome frictional resistance may be permitted to contribute in combination with attachment strength.

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Unattached Arrays

Installation option that has no attachments to roof structure.

Array is free to slide on roof during seismic event

Need to provide seismic separation around roof and objects

How to go about it?

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Code Equivalence

ASCE-7 Section 13.4 : “Components and their supports shall be attached (or anchored) to the structure … Components and their attachments shall be bolted, welded, or otherwise positively fastened without consideration of fractional resistance produced by the effects of gravity.”

IBC Section 104.11 permits alternate (non-prescriptive)

methods…..need to meet

life safety

objective…..

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Restrictions for Unattached Arrays

Prescriptive displacement≤ 3 degree roof slopeIp = 1.0Friction tests for SDC D, E, and F

All unattached arrays≤ 7 degree roof slopeHeight of C.M. ≤ 2x base and 3’

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Required Separation

Between arrays -- 0.5IpDMPVBetween array and a fixed object on the roof -- IpDMPVBetween array and roof parapet -- IeDMPVBetween array and roof edge without parapet -- 1.5IeDMPV

D

MPV

is the maximum inelastic displacement expected in the design basis earthquake

Slide35

Seismic Displacement (DMPV)

Compute seismic displacement by one of the following 3 methods:Prescriptive formula Nonlinear response-history analysisShake-table testing

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1. Prescriptive Displacement

DMPV = (SDS – 0.4)2(60 inches) ≤ 6 inchesSeismic Design Categories A, B, C DMPV = 6 inchesFriction testing not required if common roof type

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2. Nonlinear Response-History Analysis

Design-basis roof motions consistent with ASCE-7 Chapter 13 demands.Account for friction and roof slope

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Input roof motions

Option ASpectrally matched roof motionsPer ICC AC 156 with additional requirements; include motions with T > 0.77 seconds, taken proportional to 1/T.

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Input roof motions

Option BApply ground motions to a building model and extract roof motionsRecommended to bracket the assumed properties of the building model.

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3. Shake-Table Testing

Vertical motion to be includedMinimum filtering of motionsIf motions are high-pass filtered, supplemental analysis required.2D tests require 3D supplemental analysis.

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Structural Interconnection

Required interconnection strength within an array

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Friction Testing

Per ASTM G115, and:Worst case conditions for each roof surface, e.g., wet or dryIndependent test agencyMeasured under continuous movement of at least 3 inchesLoading velocity 0.1 to 10 inches per second, adjust to minimize stick-slip

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Next steps

Slide44

SEAOC Solar PV Reports into Code

ATC, NCSEA, CBC Amendments

What’s next?

Slide45

Next Steps for SEAOC Solar PV Committee

Roof live load

Special Inspection

PV tracking systems

Impacts on MWFRS

Wind loads for high profile systems on roofs

Existing building issues

Airflow effects on PV around rooftop equipment

Provide a simplified alternate for low profile systems

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Acknowledgements

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What is DSA doing?

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Authority of DSA

DSA has the

authority for plan review and supervision of construction for:

Elementary and secondary schools (K-12)

Community

Colleges

Essential Service Buildings

Plan

review and construction oversight by licensed CA Structural Engineers

Emphasis on Seismic Safety

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DSA Offices

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DSA IR 16-8

Updated in October 2012 to incorporate SEAOC PV reportsAvailable at: www.dgs.ca.gov/dsa

Slide51

DSA IR 16-8

DSA IR

16-8

addresses:

Dead load

– Check roof, keep mass increase below 10%

Live load

– No need to include where covered by panels < 24” or signs

Wind

– SEAOC PV paper, Wind tunnel requirements, peer review

Seismic

– ASCE 7 loading, unrestrained systems per SEAOC PV paper

Load combinations

– Apply load combo’s when checking uplift

Rack design

– ICC AC 428

PV Installations on

Standing Seam Metal Roofs

BIPV

systems – ICC AC 365

Fire Life Safety

requirements

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What is DSA doing?

IR 16-8 accepts both SEAOC papers with some

exceptions

:

Does not

allowing friction

concurrent

with anchorage

to resist seismic loads unless

testing and analysis performed.

Maximum slope for unattached systems is limited to 1:12 (

4.8

degrees

) instead of

7

degrees

to be consistent with 2015 IBC and 2013 CBC HCD

Amendment (following slides).

A

q

ualifying parapet

, which is used to reduce the separation distance around the perimeter of the roof, must be

checked

for the PV sliding impact load concurrent with out-of-plane wall inertial load. SEAOC PV paper does not require any structural check.

No need to check parapet if ignoring it and using

1.5

I

e

D

MPV

separation

distance.

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2013 CBC

2013 CBC Amendment to 2012 IBC Section 1509.7Effective wind area should NOT be based on effective wind area of a single unit frameDSA and HCD co-adopt Exception

Slide54

2013 CBC

2013 CBC Section 1613.5 – amendment to modify ASCE 7-10 Section 13.4 to allow unrestrained solar arrays.

Next Slide

Slide55

2013 CBC

2013

CBC Section 1613.5 (continued).

SEAOC Solar PV Paper indicates how to do this

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THANK YOU

r

on.laplante@dgs.ca.gov