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Concealed Fastener Steel Roof and Wall Panel
Structural Design Guide

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Table of Contents

Introduction	2-3
Concealed Fastener Panels Explained	2
Concealed Fastener Panel Systems	2
Structural Design Requirements	4-6
IBC Recognition of Roof and Wall Panels	4
Product Approval Reports	4
Section Properties	4
Panel Design Loads	6-13
Design Loads	6
Application of Design Loads	6
Deflection Limits	6
Panel Resistance to Inward (Positive) loads	7
Panel Resistance to Outward (Negative) loads	8
Roof Attachment (Point) Loads onto Metal Roofing	10
Photovoltaic (PV) Attachment Considerations	12
Drag Loads	12
How to Specify Product on Drawings	13
Design Examples	14-23

Introduction

Steel roof and wall panels with their attractive textures and finishes are able to provide the long term durability and environmental protection to resist the most powerful storms nature can hurl towards buildings. The attachment points  of concealed fastener panels are hidden, adding to the sleek, clean look of these panels. This combined  beauty and durability can easily be specified by the designer  to meet a project’s architectural and the structural perfor- mance requirements.

The structural design methods presented in this guide fol- low the International  Building  Code  (IBC)  requirements  for  steel roof and  wall panels. This document will guide  the designer through common loads applied to the panels including; dead loads, live loads, wind  and  snow  loads.  The steel panels resist these loads as a beam, acting in the plane of the roof or wall. The panel’s resisting capacity for inward loads are derived through principles of engineering mechanics as a multi-span beam using the panel’s section properties. The outward capacity of the panels is derived through a combination of full scale uplift testing and the fastener capacity that holds the panel to the substrate. In addition to the inward and outward out-of-plane loads,  drag loads are addressed to ensure the panels will not slide off the roof. All of these basic concepts are  addressed in  the following sections and culminate in detailed design examples.

CONCEALED FASTENER PANELS EXPLAINED
Steel roof and wall panels fall within two categories; con- cealed fastener or exposed fastener panels. See Figure 1  for an example of both types. Concealed fastener panels utilize hidden clips and/or fasteners to attach the panel to the substrate. The most common types of concealed fastener panels are referred to as standing seam panels.  Figure  2  shows common configurations of  concealed  fastener  pan-  els. In contrast, exposed fastener panels are attached to the substrate by driving a fastener directly through the panel surface leaving the fastener head  exposed.  Exposed  fas-  tener panels are also  commonly  referred  to  as  corrugated, or through-fastened, panels.

Concealed and exposed  fastener  panels  each  provide their own unique look and texture when selected as a

roof or wall covering. Concealed fastener panels provide very clean lines by eliminating the need for exposed fas- teners. Concealed fastener panels are also often chosen over exposed fastener  panels  where  weather-tightness  is a concern. Environmental factors driven primarily by tem- perature fluctuation, causes the panel assemblies to expand and contract. For steel panels, a 1/8” of expansion/contrac- tion per 10’ of panel length is a common rule of thumb.  With exposed fastener applications the fastener mounting hole may stretch or tear, ultimately resulting in leaks. Most concealed fastener assemblies allow for thermal expansion through the use of two-piece moveable clips, single piece clips that slide within the panel seam, or for those assem- blies without clips there are usually fastener slots that will accommodate some thermal movement.

The two most prevalent concealed fastener panel types are mechanically seamed and snap together panels. Each option offers the designer a choice depending on the project’s struc- tural and aesthetic needs. Mechanically seamed panels gener- ally have a substantially higher structural performance and bet- ter weather-tightness than snap together panels. They can be installed at very low slopes down to as low as 1/4":12. These panels require extra installation steps to produce the mechani- cal seam and the panels typically utilize two-piece clips with limited thermal movement. Snap together panels are generally preferred for the most visually demanding architectural applica- tions, and are easy to install. If a panel is ever damaged they   can often be readily replaced.  The one-piece clips used with   the snap together panels are often simple in design and provide unlimited thermal movement.

CONCEALED FASTENER PANEL SYSTEMS
Concealed fastener panels can be installed on a  wide  variety of substrates including, but not limited to: lumber, plywood, OSB, cold-formed steel such as  Cees  or  Zees, steel deck, hot rolled steel beams, and even concrete or masonry. Figure 3 shows examples of common roof panel assemblies over solid substrates and over open framing.

A critical component of a properly designed panel assembly  is specifying the fasteners that hold the panel or panel clip to the substrate. The nominal fastener size is generally defined by the necessary panel and clip fastener clearances. Nomi-

Common concealed fastener panel	Common exposed fastener panel

Figure 1: Common concealed vs. exposed fastener panels

 	 	  
Mechanical seam	Snap together seam

Integral seam	Hooked seam

Figure 2: Common concealed fastener panel configurations

nal fastener sizes approved for use with each panel type are defined within a manufacturer’s approval report, in their installation guide, or by contacting the panel manufacturer’s representative. The fastener length,  point,  and  thread  type  are defined by the underlying substrate type and thickness. Fasteners should be obtained through  the  panel  manufac-  turer when possible to ensure that the appropriate fastener is being used and the overall panel assembly capacities have
not been jeopardized.

For additional information on panel system components  and installation considerations and guidelines, it is advis- able to review the manufacturer’s installation guides and

other product literature; this information is nearly always available on the manufacturer’s website. Installation guides recommend standard roof and wall flashing details for aesthetics and weather resistance. Manufacturers often provide additional information around storage/handling, oil canning, underlayments, attachments, drag loads, thermal movement, as well as other considerations.

Designing concealed fastener roof and wall panels  under the prescriptive design provisions of the IBC and per the manufacturer’s recommended guidelines is the foundation for providing a structurally sound, and aesthetically attrac- tive, exterior that will last for decades to come.

 	

Over solid substrate	Over open framing

Figure 3: Common concealed fastener panel installations

Structural Design Requirements
IBC RECOGNITION OF ROOF AND WALL PANELS

The design basis for steel roof and wall panels is governed by the requirements of  the  International  Building   Code   (IBC).   Chapter 15 of the IBC addresses roof assemblies and roof top structures. Exterior walls are covered in  Chapter  14.  These  chapters  include the minimum provisions for the  prescriptive  design  of  roof  and wall panels. The prescriptive  design  includes  the  basis  for  mate- rial requirements, reference to design loads, and the reference to determining the resistance of these steel panels to the design loads.

The roof panel material requirements are defined by IBC Section 1507.4.3 that primarily ensures adequate corrosion resistance. For wall panels, IBC Section 1405.2 applies. Most steel roof and wall panels are manufactured from either AZ-50 aluminum-zinc alloy coated steel per ASTM A792 or G-90 galvanized steel per ASTM A653 which both satisfy the IBC material standards.

The performance requirements for roof panels are defined in IBC Section 1504. The most common loads applicable to steel roof panels are dead, live, snow, and wind loads. IBC Section 1504.1 states that the wind resistance of roof systems shall meet the load- ing requirements defined in IBC Chapter 16 (Structural Design).

Section 1504.3.2 states that for wind resistance, metal roof panel systems shall be tested in accordance with UL580 or ASTM E1592. An exception to this requirement is that for roofs con- structed of cold-formed steel that resist structural loads can be designed and tested per IBC Section 2210.1. Section 2210.1 specifies the use of AISI S100, North American Specification for the Design of Cold-Formed Steel Structural Members. AISI Sec- tion A3 specifies that the loads are to be in accordance with ASCE 7 where not otherwise specified within the applicable building code. It should also be noted  that  Section  D6.2  of AISI  clari-  fies and expands upon IBC’s requirements of ASTM E1592 and includes provisions for the determination of safety and resistance
factors.

Cold-formed steel wall panels are also to be designed in accor- dance with the requirements of IBC Chapter 2210 (Cold-Formed Steel) as defined in IBC Section 1404.5. Although  no provisions are defined for testing the steel wall panels for outward wind loads, ASTM E1592 test specification applies to both roof and walls and is acceptable for use as a test method for these products.

The resistance of steel roof and wall panels to meet design loads can be established through rational design, testing, or a combina- tion of both. Most concealed fastener steel roof and wall panels cannot be rationally designed for wind loads away from the structure because the performance is limited to the capacity of the panel seam and clip interface. This mode of failure is generally too complex to develop an analytical model without testing the panel assembly. Panels can generally be rationally designed to resist inward loads based on principles of engineering mechan-  ics because the panels bear on the supporting substrate and  clips, eliminating the complex failure of the panel seam and clip interface. This follows the provisions of cold-formed steel design in AISI  S100  in accordance  with  IBC  Section  2210,  as  specified

in Section 1504.3.2 for roof assemblies, and Section 1404.5 for exterior walls.

This design guide contains methods for combining panel testing and rational engineering to determine the overall outward load- ing capacity of the roof or wall panel system. Associated panel properties and performance data are generally provided by the panel manufacturer and also may be contained within a pub- lished product approval report.

PRODUCT APPROVAL REPORTS
Product approval reports issued by third party evaluation services are a great aid to engineers and building officials. The reports for steel roof and wall panels contain product performance claims based on code provisions which may include the grade of steel, section properties, summarized test results, and load tables that help expedite the design process. This independent review of product performance claims helps to expedite the design process by eliminating the difficulty and the time it takes for designers and building officials to review the manufacturer’s test data, and then to develop panel assembly capacities that may be outside their area of expertise. With product approval reports, the product claims are verified by a third party evaluation service to ensure conformance with the prescriptive provisions and performance testing requirements defined within the IBC. The approval reports may also be based on methods that are not prescribed in the IBC, which falls under ‘alternate materials, designs and methods’ in IBC Section 104.11.

Confidence in approval reports is based on the competency of  the third party evaluation service. Proper accreditation provides  a significant part of this confidence. The accreditation provides assurance that they are performing the product review in accor- dance with the applicable standards of the IBC. Three major evaluation services - International Association of Plumbing and Mechanical Officials’ Uniform Evaluation Services (IAPMO Uniform ES), International Code Council Evaluation Services (ICC-ES), and Architectural Testing Inc., are all accredited to the stringent standards of the American National Standards Institute (ANSI) per the ISO/IEC Guide 65, General  Requirements  for Bodies Operating Product Certification Systems. These and other evaluation services that have the ISO/IEC Guide 65 accreditation are widely accepted.

SECTION PROPERTIES
The published section properties are used for determining the allowable  inward  out-of-plane  loads.  The   section   properties of each panel are directly  related  to  the  panel  shape,  gage, and grade of steel. They are calculated in accordance with the American Iron and Steel Institute’s North American Specification for the Design of Cold-Formed Steel Structural Members, AISI S100-2007, Chapter B. Section properties are used to develop the bending and deflection capacity of steel panels for out-of plane loads which are typically defined by gravity or wind. The section properties are defined as either gross or effective and include the area of section, moment of inertia, and section modulus.

Effective Section Properties
For design purposes the effective properties are typically used to determine the panel’s resistance to the applied loads. The effec- tive section properties for steel panels are similar to other cold- formed steel members such as Cees and Zees; they are based  on post buckling strength. Post buckling strength is based on the concept that the compression flanges and portions of the webs will exhibit some localized buckling prior to the full capacity of the panel being reached. To account for the buckling, the flat compression elements of the panel are reduced for the purpose of determining the section properties, excluding the portion of the panel that can no longer carry compression loads due to the buckling of the element.

The effective properties are determined at the full yield stress of the steel. As the grade of steel increases, the effective section properties decrease. The moment capacity of the panel increases with the increased grade of steel because the increasing yield strength outpaces the loss of effective  compression  width  of the combined flat elements. The following table demonstrates this for AEP Span’s 16” Span-lok hp:

16” Span-lok hp	
Yield (ksi)	
Gage	Ig (in4)	Ie+ (in4)	Ie- (in4)	Se+ (in3)	Se– (in3)	Mn+ (k-in)	
33	24	.1965	.1898	.0825	.1194	.0731	3.145	
40	24	.1965	.1868	.0795	.1175	.0699	3.751	
50	24	.1965	.1815	.0765	.1132	.0665	4.519	
80	24	.1965	.1763	.0750	.1088	.06340	5.209	
Note: Span-lok hp is only offered in Grade 50 . The other grades indicated above are for informative purposes only .

Gross Section Properties
The gross section properties of the panel are based on the entire cross sectional area. To determine the gross section properties, it is assumed that there are no “ineffective” ele- ments across the section. The gross section properties are used in conjunction with the effective section properties to determine panel deflection under uniform out-of-plane loads.

Moment of Inertia
The service load moment of inertia is  used to  determine  the deflection of the steel panel for uniformly distributed out-of-plane loads. The calculated moments of inertia are determined at a working stress level of 0.6FY. Following accepted practice the hybrid moment of inertia is the  sum of two times the effective moment of inertia and the gross moment of inertia, divided by three:

Id = 2Ie  + Ig

3
This equation takes into account that throughout the length of the span, portions of the panel will have low bending stress below the onset of localized compression buckling in which the gross section properties would be valid. The other por- tions of the span will have bending stresses high enough to push beyond the onset of localized compression buckling in which the effective section properties would be appropriate.

Section Property Tables
Below is an example of a typical published section property table that contains gross and effective section properties.

Weight of Panel
Section per sq/ft

Gross Section Properties
are Identified by the Subscript, g

Panel Gage

Base Metal Thickness (without coating)

Effective Section Properties
are Identified by the Subscript, e

Hybrid Moment of inertia fo Uniform Load Condition Only

Effective Net Area
of Section

Positive and Negative Effective Moment of Inertia for Non-uniform Load Conditions

DESIGN LOADS

Panel Design Loads

Design loads applied to steel  roof  and  wall  panels  should  be in accordance with ASCE 7. Inward and outward wind loads, and the internal building pressure due to wind loads, are resisted by the roof and wall panels. Roof panels are also subject to gravity loads including dead, live, and snow. The following are the load combinations from ASCE 7-10 that apply to roof and wall panels that include wind.

ASD
D + 0 .6W
D + 0 .75L + 0 .75(0 .6W) + 0 .75(Lf  or S or R) 0 .6D + 0 .6W

LRFD 
1 .2D + 1 .6(Lf  or S or R) + 0 .5W
1 .2D + W + L + 0 .5(Lf  or S or R)
0.9D + W

For load combinations  that  include  wind,  the  wind  loads can be multiplied  by  0.67  for  roof  panels  satisfying  spe-  cific requirements in Appendix A, Section D6.2.1a of AISI S100-07.  Conditions  (b)  and  (c)  are   the   responsibility  of the engineer of record. Conditions (a) and (d-g) can be con- firmed  by  the  metal  roof  panel  manufacturer.   These  can be confirmed via the manufacturer’s approval report, or by verifying with the metal roof panel representative directly. Refer to the AISI excerpt below:

D6.2.1a Strength [Resistance] of Standing Seam Roof Panel Systems
In addition to the provisions provided in Section D6.2.1, for load combinations that include wind uplift, the nominal wind load shall be permitted to be multiplied by 0.67 provided the tested system and wind load evaluation satisfies the following conditions:
The roof system is tested in accordance with AISI S906.
The wind load is calculated using ASCE/SEI 7 for com- ponents and cladding, Method 1 (Simplified Procedure) or Method 2 (Analytical Procedure).
The area of the roof being evaluated is in Zone 2 (edge zone) or Zone 3 (comer zone), as defined in ASCE/SEI 7, i.e. the 0.67 factor does not apply to the field of the roof (Zone 1).
The base metal thickness of the standing seam roof panel is greater than or equal to 0.023 in. (0.59 mm) and less than or equal to 0.030 in. (0.77 mm).
For trapezoidal profile standing seam roof panels, the dis- tance between sidelaps is no greater than 24 in. (610 mm).
For vertical rib profile standing seam roof panels, the dis-

tance between sidelaps is no greater than 18 in. (460 mm).
The observed failure mode of the tested system is one of the following:
The standing seam roof clip mechanically fails by sepa- rating from the panel sidelap.
The standing seam roof clip mechanically fails by the sliding tab separating from the stationary base.

APPLICATION OF DESIGN LOADS
The application of design loads to the steel roof or wall panels is dependent upon the substrate that supports the panels. The panels may be installed on solid  substrates such as plywood, OSB, steel deck, or concrete. Panels may also be installed over open framing such as joists, purlins, beams, and skip sheeting. These loads should be applied using the load combinations defined in ASCE 7.

Panels installed over solid substrates do not carry all of the design loads. It is assumed that the solid substrate carries all inward loads including the external wind loads acting inwards, and the dead, live, and snow gravity loads. Panel clips may raise the panel up to ½” above the solid substrate but the flat pan of the panel will deflect under the maxi- mum design loads, transferring these loads directly to the substrate. Any influence of the panel’s strong axis bending capacity is ignored with this assumption. External wind loads acting outwards (wind uplift) is resisted by the panel and the loads transferred to the substrate through the panel fasteners. The internal building pressure (acting outward) is resisted by the solid substrate. This assumption is based on the premise that in the short duration of the design wind gust, the internal pressure will not have time to build and infiltrate through the solid substrate and pressurize the underside of the steel roof or wall panels. See Figure 4.

When installed over open framing the panel will carry all of the design loads and transfer these loads to the support fram- ing members. The panel must support the gravity loads which include dead, live, and snow loads. The panels must also carry the net inward and outward wind loads. See Figure 4.

DEFLECTION LIMITS
Roof and wall panels deflect under inward and outward loads. These deflections are generally restricted  to  the L/60 limit as defined in the International Building Code (IBC), Chapter 16, Table 1604.3. See Figure 5. The IBC prescribes deflection limits to address the fact the roof assemblies are comprised of several materials that have varied stiffness and to limit the possibility of perceivable vibrations. For structural roofing and siding  panels  the table indicates a recommended deflection limit of L/60 for combined dead and live loads. Since steel roof and wall panels generally do not directly support brittle or vibra- tion/ deflection sensitive interior finish materials, an L/60 deflection limit is appropriate in most cases.

Summary of applied loads

Panels over open framing

Panels over solid substrate (Panel loads)	Panels over solid substrate (Substrate loads)
Figure 4: Application of design loads

Figure 5: IBC deflection limits

PANEL RESISTANCE
TO INWARD (POSITIVE) LOADS
The panel’s inward loading capacity is determined by equations of mechanics using the calculated section properties. The meth- ods for developing section properties and member capacities (bending, shear, combined bending and shear, and web crip- pling, and combined bending and web crippling) for all cold- formed steel structural members, including steel roof and wall panels, are prescribed in AISI S100.

To aid in the selection of steel roof and wall panels, AEP Span publishes inward uniform load tables which are based upon the overall inward panel capacity. The tables also include common service load deflection limits typically dictated by code require- ments. Where no deflection limit value is listed in the table, the panel strength governs for the particular span and deflection limit combination. An example is shown in Figure 6 on next page.

Figure 6: Inward uniform load capacity table

PANEL RESISTANCE TO OUTWARD (NEGATIVE) LOADS
For concealed fastener roof and wall panels that require
testing to determine the resistance to the design loads, they should be tested in accordance with ASTM E1592, Test Meth- od for Structural Performance of Sheet Metal Roof and Siding Systems by Uniform Static Air Pressure Difference. IBC Sec- tion 1504.3.2 allows for the use of ASTM E1592 or UL 580.     It should be noted that the results of UL 580 testing provides a UL rating which is only used to evaluate the comparative resistance of one roof system to another and does not report the ultimate capacity of the roof panel system. For example, a UL90 rating doesn’t indicate an ultimate or allowable capac- ity of 90psf. On the other hand, ASTM E1592 reports the ulti- mate performance of the roof panel system that can then be used to develop the factored or allowable capacity using the resistance and safety factors prescribed in AISI S100 Section D6.2 in accordance with IBC Section 2210.

The ASTM E1592 test utilizes  a  static  air  pressure  differential to create a uniform load across the panels to simulate uplift forces on the roof system. The test cycles the panels through increasing loads until the panel assembly can no longer  sup- port loads or no longer functions as a weather-tight membrane. The test’s uniform pressure loads the entire load path from the panel surface to the seam, the seam/clip interaction, clip, clip/ fastener interaction, fastener, and fastener/substrate interac- tion as shown in Figure 7. The uplift  capacity  of  the  entire panel assembly is thoroughly evaluated with this test method.

WIND UPLIFT

FASTENER REACTIONS
PANEL
SEAM STRENGTH & CLIP-PANEL INTERFACE

CLIP STRENGTH
CLIP-FASTENER INTERFACE

FASTENER
FASTENER SUBSTRATE INTERFACE

Figure 7: Panel to substrate load path

To generate test results with the widest applicability, some test variables are eliminated as possible modes of failure. Fastener strengths and pull-out resistance from the substrate can be obtained through fastener testing or through prescriptive fas- tener design methods. The clip capacity, clip-seam interface,

PANEL	S = SPECIFIED CLIP SPACING

panel and seam strengths cannot be rationally designed using engineering mechanics for most concealed fastener panels. To ensure that the test’s mode of failure is related to the panel/clip assembly and not the fastener, the fasteners and substrates are intentionally overd esigned to ensure they do not fail in the test.

The load path for the  outward  uniform  wind  load  is  distributed to the  panel  attachments  based  on  the  panel’s  tributary  area  to the  clip  and/or  fastener.    Figure  8 depicts  this  tributary  area.

TRIBUTARY AREA OF CLIP

S⁄2	S⁄2

W⁄2 W⁄2

W = TYPICAL PANEL WIDTH

For clip attached panels the load applied to the clip is then transferred to the  substrate through the  clip fasteners. It  is important to consider the increase in  fastener  loading due to the eccentricity of the fasteners relative to the panel seam. See Figure 9 which shows the typical eccentric load- ing of the on panel clip fasteners.

TRIBUTARY AREA OF CLIP

Figure 8: Tributary area

Clip with one fastener, or multiple fasteners in a line parallel to panel seam.

Clip with a line of 2 fasteners perpendicular to panel seam.

P	P

R1	R2

b

a

R

b

a

c

Sum M  0	Sum M  0

P a  R b  0

P a  R1 b  R2 c  0

Using , R1     R2
b	c

R 	P a	

R  P(a) 

R  P(a)(c) 

b# fasteners

1	(b  c2 b)

2	(b2  c2 )

Figure 9: Eccentric load of panel clip fasteners

To assist in specifying clip and fastener attachment  pat- terns to resist the outward wind design loads, AEP Span publishes attachment schedules for common fastener and substrate combinations. See Figure 10. These tables allow the user to quickly select a clip and/or fastener spacing based on the allowable or factored resistance of the panel and the attachment to the substrate based on the outward

wind load requirements. The attachment schedules for AEP Span’s panels are based on a combination of testing, prin- ciples of engineering mechanics, and connection strength. The methods used to develop these tables can be extended to other substrates or fasteners for the panels. Design Examples #2 and #3 at the end of this document provide insight on how this process works.

Figure 10: Fastener attachment schedule

ROOF ATTACHMENT (POINT) LOADS ONTO METAL ROOFING
Prior discussion of  design loads within this guide focused  on uniform loads. Roof attachments, including loads from solar racking, induce concentrated point  loads  that  must be appropriately accounted for. The guidance  that  fol- lows evaluates applications where the roof attachments are made directly to the panel seam, which is the predominate method for the attachment of these point loads.

Figure 7 showed us uniform loads and their associated load path back to the substrate. Figure 11 shows typical load paths for point loads applied in-line with the panel attach- ment clips and for loading conditions where the load is applied between the clips.

LOAD PATH ANALYSIS

Roof attachment (seam clamps)
Roof attachments are commonly fastened to  metal  roof- ing via roof seam clamps. S-5!® and AceClamp® are two popular solutions. The S-5! website provides some design guidance as well as a rather extensive list of clamp options and clamp capacities for both longitudinal (drag) loads and perpendicular (wind uplift) loads.

It must be noted that the capacities listed with S-5! only evaluate  the  clamp-to-panel  connection.   The   test  results do not take into consideration the entire  load  path  which  also includes panel bending  strength,  clip-panel  interface, clip strength, and fastener-to-substrate capacities.

For roof clamps that do not have capacities listed, tests will need to be conducted to develop  capacities unless the  connec- tion can otherwise be rationally evaluated.

Loads through Panel Seam
For applications where  point loads are applied between roof panel clips, the bending capac- ity of the roof panel should be evaluated. Standard engineer- ing mechanics and panel sec- tion properties provided by the metal roofing manufacturer will assist the user in determining if the roof attachment loads are acceptable for this segment of the load path. This design guide assumes that the applied point load is within a roof panel array and the subsequent beam anal- ysis uses fixed ends; see Figure
This approach relies on the position that  the surrounding panel array does not allow the beam ends to rotate. If a more

Figure 11: Roof attachment load path

thorough load analysis is required for a particular project, then the design professional may extend beyond this basic analysis   as needed.

In applications where the roof attachment clamps  are  installed directly over the roof panel clips (or panel-to- substrate attachment), the bending capacity of  the  panel  does not need to be evaluated.

Figure 12: Point load analysis

Clip/Panel Capacities
The clip-to-panel capacities can be derived from the panel assem- bly uplift tests, or from subsequent panel attachment tables. This method is generally conservative as it uses system limits not just the clip-to-panel capacities. Beyond this, clip-to-panel capacities can also be developed from dedicated clip pull testing.

Example: 16in wide panel tested at a 5ft attachment spac- ing has an allowable system capacity  of 50psf.  In looking at the tributary area of each clip, 1.33ft x 5ft = 6.65ft, the clip-to-panel allowable capacity is at least 6.65ft x 50psf = 332.5lbs.

When evaluating roof attachments, it is also important to under- stand what panel clips are being utilized:

One piece clips: Some roof panel assemblies utilize a one- piece clip design in which thermal movement is managed by the clip sliding within the panel seam. These designs require that the roof attachments not be located over the panel clip, or within a couple inches of the panel clip as these roof attachments could interfere with the ability of the panel assembly to address thermal movement.

Sloped PV on sloped roofs: There are no industry approved analytical methods for evaluating. Wind tunnel testing is recommended for the proper review of these applications.

Other PV wind design resources that exist, but have not been verified for appropriateness or accuracy (use with caution):

UniRac design tool: http://design.unirac.com/tool/

Center   For   Environmental   Innovation   In    Roofing    about PV Racking Criteria for Low-Slope Metal Roof Systems: http://roofingcenter.org/main/Initiatives/pv 

Two piece clips: Panel assemblies that utilize a two-piece clip design generally employ a clip that manages thermal movement between the upper and lower clip portions. For these applications it is best to locate roof attachments directly over the clip to avoid having to analyze the bending capacity   of the metal roof panel. Thermal  movement  is not  hindered by the location of the roof attachments. The load path goes directly from the roof attachment clamps, through the panel clip, and into the panel substrate.

Clip-To-Substrate Capacities
The clip-to-substrate capacities are often the primary constraint in the roof attachment load path. Fastener capacities into vari- ous substrates can be evaluated based on industry standards, per testing, or per approved evaluation or acceptance report for the fastener. Refer to Section 5.2 of the IAPMO-UES Evaluation Criteria #EC 011 for further guidance on the development of these capacities. Increase in fastener loading due to the eccen- tricity of the fasteners relative to the panel seam shall also be taken into account. Refer to page 9 for an explanation of this.

PHOTOVOLTAIC (PV) ATTACHMENT CONSIDERATIONS

DRAG LOADS

Figure 13: Drag loads

Code Direction (2012 IBC)
With the introduction of the 2012 IBC, specific language has been added around the evaluation of solar structures although the building code provides little direction on the specific evalu- ation of these structures.

Calculation of PV Design Loads
The following are the four common types of PV installation configurations and the currently available (at the release of this design guide) consensus standards for evaluating them for wind loads:
Flush mounted PV on flat roofs: Use ASCE-07. PV is parallel to roof surface and within 10in.

Flush mounted PV on sloped roofs: Use ASCE-07. PV is parallel to roof surface and within 10in.

Sloped PV on flat roofs:  SEAOC-PV2 design guide.  Limited   to roof slopes ≤ 7°, and mean roof heights ≤ 60ft.

Drag loads are forces on a sloped roof panel caused by grav- ity loading (dead, live and snow). There exists a component  of the gravity force that acts down the roof slope. This  loading is depicted in Figure 13. This drag load causes the panels to want to slide off the roof. Panels must be properly fixed to the substrate to overcome these drag loads. This is typically accomplished by through-fastening  the  panel  to  the substrate under the ridge cap flashing. The number of fasteners required per panel is rationally calculated using principles of engineering mechanics and fastener properties. For evaluation purposes, the interaction between the panel and the underlayment is assumed to be frictionless (worst case). In heavier snow climates it may be necessary to have more than 10 fasteners per panel to keep the panels in place. Also note that it is very important to only have one point of fixity on a concealed fastener roof or wall panel. This allows the panels to naturally expand and contract which assists in preventing any thermal movement issues.

HOW TO SPECIFY PRODUCT ON DRAWINGS
Correctly specifying steel roof and wall panels on the design drawings is important to ensure that the desired panel is speci- fied and attached to the structure in a manner that will resist   the required design loads.

Traditionally panels have been selected by the architect and then the manufacturer or specialty engineer provides engi- neering services to determine the panel attachment to the structure as a deferred structural submittal. Some jurisdictions such as the California Division of the State Architect are now requiring the steel roof and wall panels to be fully engineered and submitted for design review prior to construction permits being issued.

Deferred engineering submittals can create problems if the selected steel roof or wall panel assembly is not capable of meeting the project’s load requirements. This can lead to addendums being issued to adjust the specified panel which may lead to costly changes during the project’s construction phase. If the correct panel and attachment schedule is speci- fied and clearly shown on the contract drawings, the risk of these costly changes can be reduced by ensuring the desired panel is capable of meeting the structural requirements.

Attachment Zones
The primary requirement that defines the attachment of steel roof and wall panels is outward wind loading. It can be dif- ficult to describe the clip and fastener spacing for a particular building area within the specifications, therefore conveying the information on the architectural or structural design draw- ings is a useful and effective option.

To provide the least installed cost to the building owner, the attachment spacing should vary based on the design loads.    A zone map of the roof and/or building elevations showing the uplift pressure zones is a good basis for providing the

C	B	C	

B	A

SLOPE	
B	
C	B	C	
C	B	C	

B	A

SLOPE	
B	
C	B	C	

ROOF ZONE PLAN
Figure 14: Wind zone map

Attachment Schedule
The attachment schedules for steel roof and wall panels should use an optimized clip and fastener spacing for each building wind zone. The attachment spacing should be defined by the outward panel loading but not exceed the support spacing required for the inward panel loads. The schedule should include the following information:
Clip type and spacing.
Fastener type and spacing.

See Figure 15 for an example of panel attachment schedule. Optional information would be to include drag load fastener requirements. The drag load attachment could also be con- veyed in the details on the plans if the project does not require different zones for drag load fasteners. Drag load require- ments would include:
Drag fastener type and quantity.

C	B	B
C
B	A	A

attachment spacing optimized for each zone. Figure 14 is an example of a gable roof plan with clearly identified zones. On simple projects the zones may be numbered 1, 2 and 3 follow- ing the zone designations outlined in ASCE-7 for wind loads. For complex roof configurations with more than three zones, the designer will need to provide an alternate numbering or lettering system to describe all the zones on the building.

H
H

MEAN HEIGHT

B	  

C	B	B
C
L2

L1

Steel Roof Panel Schedule	
Zone	Panel	Clip	Clip Fasteners	Drag Fasteners	
	Manufacturer	Type	Width, in	Gage	Type	Spacing, in	Type	Quantity	Type	Quantity	
A	AEP Span	Span-Lok hp	16	24	2-1/2” Std	60	#12	2	#14	3	
B	AEP Span	Span-Lok hp	16	24	2-1/2” Std	36	#12	2	#14	3	
C	AEP Span	Span-Lok hp	16	24	2-1/2” Std	12	#12	2	#14	3	

Figure 15: Panel Attachment schedule

DESIGN EXAMPLES
The following are several design examples to show what steps are necessary to design in a steel roof or wall panel. Examples will be evaluated:

Installations over Solid Substrates
#1 - Over 19/32” plywood (using published fastener attachment tables)
#2 - Over 19/32” plywood (using calculations) #3 - Over 20ga steel deck (using calculations)

Installations over Open Framing
#4 - Over 16ga steel purlins (using published fastener attachment tables)
#5 - Over 16ga steel purlins (using calculations)

Other Considerations
#6 - Drag loads over plywood
#7 - Drag loads over steel purlins
#8 - Thermal movement (clips and joggle cleats) #9 - Roof attachment (point load)

Common Parameters:
Panel: AEP Span 16” Span-lok hp, 24ga (0.0232)
Fastener: #12 (ø0.216 nominal diameter as defined in 2005 NDS Table 11.3.2A and in 2007 AISI S100 Commentary, Table C-E4-1)

Notes:
Roof panels are evaluated in these examples. Wall panel evaluation is similar using applicable wall design loads.
All examples use Allowable Stress Design (ASD)
The example calculations are for one roof zone only.
Only uniform loads are evaluated.
Positive(+) loads indicate towards the surface, (-) indicates away from.
Installations over open framing are evaluated as a triple span condition.

DESIGN EXAMPLE #1: Installation over 19/32” Plywood (tables)
The only design loads that are applied to the roof panel are the outward loads and drag loads (drag loads addressed in Design Examples #6 and #7)

Conditions:
The ASCE7-10 load combinations produce the following loads:
Outward loads = -40psf

Span at which fastener and substrate combination meets or exceeds 40psf uplift. Per published panel attachment table:

16" Span-lok hp & SpanSeam, 24ga, with Std. Clip	

Substrate	Fastener	Attachment Spacing, (ft-in)	
	#
per clip	
Size	1' - 0"	1' - 6"	2' - 0"	2' - 6"	3' - 0"	3' - 6"	4' - 0"	4' - 6"	5' - 0"	
			Panel / Clip Negative (Outward) Uniform Load Capacity, (lbs/ft2)	
			190	298	174	273	158	248	142	223	126	198	110	173	94	148	77	123	61	98	
			Panel System Negative (Outward) Uniform Load Capacity, (lbs/ft2)	
			ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	ASD
W/W	LRFD
φW	
	12ga	2	#10	190	298	174	273	148	223	119	178	99	149	85	127	74	111	66	99	59	89	

	2	#14	77	104	52	70	39	52	31	42	26	35	22	30	19	26	17	23	15	21	
19/32"	2	#10	78	106	52	71	39	53	31	42	26	35	22	30	20	26	17	24	16	21	
	2	#12	89	120	59	80	44	60	36	48	30	40	25	34	22	30	20	27	18	24	
	2	#14	98	132	65	88	49	66	39	53	33	44	28	38	24	33	22	29	20	26	
23/32"	2	#10	95	128	63	85	47	64	38	51	32	43	27	36	24	32	21	28	19	26	

Plywood & OSB

Clips will need to be installed at a 2’-0” spacing to meeting 40psf design loads.

DESIGN EXAMPLE #2: Installation over 19/32” Plywood (using calculations) Conditions:
The ASCE7-10 load combinations produce the following loads:
Outward loads = -40psf

Span at which panel/clip capacity exceeds the 40psf uplift requirement per published allowable outward load capacities (independent of fastener/substrate) via product sheets, manufacturer representative, or similar.

Gage	Allowable Outward Loads (lbs/ft2) per Span (ft.-in.)	
	1-0	1-6	2-0	2-6	3-0	3-6	4-0	4-6	5-0	
24	189.9	177.0	163.2	148.5	132.8	116.2	98.7	80.3	61.0	
22	249.1	219.2	191.7	166.7	144.1	124.1	106.6	91.5	78.9	

Panels installed at 5’-0” exceed 40psf design loads (panel capacity, not fastener/substrate capacity), taken from product sheet.

Next, span at which fastener and substrate combination exceeds 40psf uplift requirement. Fastener pullout strength per NDS Equation 11.2-2: 2850  G2  D
G = 0.45 (Plywood and OSB) as specified in The Engineered Wood Association APA #TT-051C

2850  0.452  0.216  124.6lbs / in

ASD Adjustment factors per NDS Table 10.3.1:

Ctot  CD  CM  Ct  Ceg  Ctn
Ctot  1.6 1.0 1.0 1.0 1.0  1.6

Fastener pullout capacity =

124.6 lbs 1.6  19 in  118.4lbs

in	32

Fastener capacity per square foot =

(# fasteners × fastener tension capacity ÷ fastener load adjustment) panel width × clip spacing

Determine fastener load adjustment using engineering mechanics (refer to design guide) and clip dimensions.

         

 		R2
R1

 P(a)(c) (b2   c2 )

(b  c2 b)

	P(a)

 0.64(P)
 1.36(P)

where a=1.56, b=0.94, c=0.44
Combined fastener adjustment = 1.36+0.64 =2.0

Fastener capacity per square foot =

(2 118.4lbs  2.0)  89.0lbs / ft 2
(1.33 ft 1.0 ft)

Maximum clip spacing based on fastener/substrate capacity = 89.0 psf  40 psf  2.22 ft  2 ' 3"
Overall capacity is the minimum of the panel/clip capacity, 5’-0” and fastener/substrate capacity, 2’-3” Max span is 2’-3” to meet outward wind load requirements.
Note: This design example shows usage of the Span-Lok hp Standard Clip although applications over solid substrate often utilize the Low Profile Clip with its lower standoff (not shown).

DESIGN EXAMPLE #3: Installation over 20ga Steel Deck (using calculations)

Conditions:
The ASCE7-10 load combinations produce the following loads:
Outward loads = -40psf

Span at which panel/clip capacity exceeds the 40psf uplift requirement per published allowable outward load capacities: At 5’-0” attachment spacing, panel/clip capacity exceeds 40psf design loads (taken from Design Example #2).

Next, span at which fastener and substrate combination exceeds 40psf uplift requirement. Nominal fastener pullout strength based on 2007 AISI S100, Equation E4.4.1-1:
Pnot  0.85  tc  d  Fu 2
tc  Substrate thickness  0.0359in
d  Nominal screw diameter  0.216in

Fu 2

 Tensile strength, substrate

 45, 000lb / in2 , taken from product sheet

Pnot

 0.85  (0.0359in)(0.216in)(45, 000lb / in2 )
 296lb

Fastener pullout capacity, ASD

P   Pnot
a	

where   3.0

 296lb  98.6lb 3.0

Fastener capacity per square foot = (2 fasteners  98.6lbs  2.0 fastener load adjustment)  74.1lbs / ft 2
(1.33 ft 1.0 ft)

Maximum clip spacing based on fastener/substrate capacity = 74.1psf  40 psf

 1.85 ft  1' -10"

Overall capacity is the minimum of the panel/clip capacity, 5’-0” and fastener/substrate capacity, 1’-10” Max span is 1’-10” to meet outward wind load requirements.

DESIGN EXAMPLE #4: Roof Installation over 16ga Purlins (tables)
The design loads that are applied to panels over open framing are gravity loads, external inward and outward acting loads, internal loads acting outwards, and drag loads (drag loads addressed in Design Example #6).

Conditions:
The ASCE7-10 load combinations produce the following loads:
Outward loads = -60psf Inward loads = +40psf

Panel outward load capacities:
Span at which fastener and substrate combination meets or exceeds 60psf uplift. Per published panel attachment table:

16" Span-lok hp & SpanSeam, 24ga, with Std. Clip	

Substrate	Fastener	Attachment Spacing, (ft-in)	
	#
per clip	
Size	1' - 0"	1' - 6"	2' - 0"	2' - 6"	3' - 0"	3' - 6"	4' - 0"	4' - 6"	5' - 0"	
			Panel / Clip Negative (Outward) Uniform Load Capacity, (lbs/ft2)	
			190	298	174	273	158	248	142	223	126	198	110	173	94	148	77	123	61	98	
			Panel Sys tem Negative (Outward) Uniform Load Capacity, (lbs/ft2)	
			ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	

Cold Formed Steel (Gr 55
min.)	12ga
(.1050)	2
2
2	#10
#12 1/4"	190
190
190	298
298
298	174
174
174	273
273
273	148
158
158	223
248
248	119
135
142	178
203
223	99
112
126	149
169
195	85
96
110	127
145
167	74
84
94	111
127
146	66
75
77	99
113
123	59
61
61	89
98
98	
	14ga
(.0700)	2
2
2	#10
#12 1/4"	190
190
190	297
298
298	132
150
174	198
225
261	99
112
130	149
169
195	79
90
104	119
135
156	66
75
87	99
113
130	57
64
74	85
96
112	49
56
65	74
84
98	44
50
58	66
75
87	40
45
52	59
68
78	
	16ga
(.0590)	2
2
2	#10
#12 1/4"	167
190
190	250
284
298	111
126
146	167
190
220	83
95
110	125
142
165	67
76
88	100
114
132	56
63
73	83
95
110	48
54
63	71
81
94	42
47
55	62
71
82	37
42
49	56
63
73	33
38
44	50
57
66	
	18ga
(.0470)	2
2
2	#10
#12 1/4"	133
151
175	200
227
263	89
101
117	133
151
175	66
76
87	100
113
131	53
60
70	80
91
105	44
50
58	67
76
88	38
43
50	57
65
75	33
38
44	50
57
66	30
34
39	44
50
58	27
30
35	40
45
53	

Clips will need to be installed at a 3’-0” maximum spacing to meet 60psf outward design loads.

Panel inward load capacities:
Span at which fastener and substrate combination meets or exceeds 40psf inward loading. Per load table on published panel product sheet:

16” Width Span-Lok hp & SpanSeam	

Gage	
Span	
Cond.	Allowable Inward Loads (lbs/ft2) per Span (ft.-in.)	
			2-0	2-6	3-0	3-6	4-0	4-6	5-0	

24	
SS	f	486	327	233	174	135	107	88	
		L/180	-	-	-	-	-	-	-	
		L/60	-	-	-	-	-	-	-	
	
DS	f	303	200	142	104	80	63	52	
		L/180	-	-	-	-	-	-	-	
		L/60	-	-	-	-	-	-	-	
	
TS	f	368	244	174	129	99	79	65	
		L/180	-	-	-	-	-	-	-	
		L/60	-	-	-	-	-	-	-	

Clips will need to be installed at a 5’-0” maximum spacing to meet 40psf outward design loads. Conclusion: Maximum span for roof zone evaluated is 3’-0”.

DESIGN EXAMPLE #5: Roof Installation over 16ga Purlins (calculations)

Conditions:
The ASCE7-10 load combinations produce the following loads:
Outward loads = -60psf Inward loads = +40psf

Span at which panel/clip capacity exceeds the 60psf uplift requirement per published allowable outward load capacities (independent of fastener/substrate) via product sheets, manufacturer representative, or similar.

Gage	Allowable Outward Loads (lbs/ft2) per Span (ft.-in.)	
	1-0	1-6	2-0	2-6	3-0	3-6	4-0	4-6	5-0	
24	189.9	177.0	163.2	148.5	132.8	116.2	98.7	80.3	61.0	
22	249.1	219.2	191.7	166.7	144.1	124.1	106.6	91.5	78.9	

Panels installed at 5’-0” exceeds 60psf design loads (panel capacity, not fastener/substrate capacity).  Next, span at which fastener and substrate combination exceeds 60psf uplift requirement.
Nominal fastener pullout strength based on 2007 AISI S100, Equation E4.4.1-1:

Pnot  0.85  tc  d  Fu 2
tc  Substrate thickness  0.0590in
d  Nominal screw diameter  0.216in

Fu 2

 Tensile strength, substrate

 70, 000lb / in2

Pnot

 0.85  (0.0590in)(0.216in)(70, 000lb / in2 )
 758lb

Fastener pullout capacity, ASD

P  Pnot

where   3.0

a	
 758lb  252lb 3.0

Fastener capacity per square foot =

(2 fasteners  252lbs  2.0(fastener load adjustment))  189 psf
(1.33 ft 1.0 ft)

Maximum clip spacing based on fastener/substrate capacity = 189 psf  60 psf  3.15 ft  3 ' 2"

Overall capacity is the minimum of the panel/clip capacity,  5’-0”  and  fastener/substrate  capacity,  3’-2” Max span is 3’-0” (rounded) to meet outward wind load requirements.

Positive loads:

Check for uniform inward (positive) loads using engineering mechanics:
Deflection Limit,   L  36in  0.6in
60	60
()(E)(I  )	(29.5x106 lb/ in2 )(0.1865in4 / ft)(0.6 in)(12 in/ ft)

W 	
.0069(L4 )

.0069(36in)4

 3418 psf

Inward flexural strength:



F (S  )	50000 lb in2 (0.1132 in3

	

ft)  1 ft 

W       b	
0.08(L)2

0.08(3 ft)2

 12in   655 psf

	

	F (S  )	50000 lb in2 (0.0665 in3 ft)  1 ft 

W       b	
0.10(L)2

0.10(3 ft)2

 12in   308 psf

Limiting condition for positive loading = negative flexural strength = 308psf Maximum span based on flexural loading = 308 psf  40 psf  7.7 ft  7 ' 6"

DESIGN EXAMPLE #6: Drag Loads over Plywood Substrate

Conditions:
Panel: 16in wide Span-lok hp 24ga Substrate: 19/32” plywood Combined  gravity  load:  20psf Roof Slope: 3:12
Panel Length: 30ft Determine Drag Load

Psnow  snow load × panel length × panel width

	

 20 lbs  30 ft 16in  1 ft   800lbs

ft 2

 12in 

snow

Drag  sin(14 )  P
 0.242  800lbs
 194lbs

Allowable Fastener Capacities:
Substrate lateral (shear) capacity per 2005 NDS Section 11.3.1 Nominal capacity is the minimum of the following yield modes:

Mode Im

Z  D(lm )(Fem )
Rd

(Eq 11.3-1), where

D  Diameter  Dr (per 11.3.6)  0.171in (Table L3)
lm  Dowel bearing length  19 / 32"  0.593in *

Fem

 Member dowel bearing strength  3350 lb in2 (Table 11.3.2B)

R d  Reduction term  Kd  10(D)  0.5 (Table 11.3.1B)
= 10(0.171)+0.5 = 2.21

(0.171in)(0.593in)(3350 lb in2 )

Z 	 153.7lbs
2.21
* NOTE: Since the substrate thickness provides less than the required 6D screw penetration
(as specified in NDS Section 11.1.4.6), the substrate will require support blocking at drag fastener locations to meet this minimum penetration requirement.

Mode Is

Z  D(ls )(Fes )
Rd

(Eq 11.3-2), where

ls  Dowel bearing length  19 / 32"  0.0232in *

Fes

 Member dowel bearing strength  65000 lb in2 (Table 11.3.2B)

Mode II

Z 	 116.7lbs

(0.171in)(0.0232in)(65000 lb in2 )

2.21

Z  k1D(ls )(Fes )

R  2R 2 (1  R  R 2 )  R 2 R 3  R (1  R )

e	e

t	t	t	e	e	t

Rd

(Eq 11.3-3), where

k1 

Re  Fem Rt  lm

(1  Re )
Fes  3350 65000  0.051
ls  0.593 0.0232  25.56

, where

k1  0.53

0.53(0.171in)(0.0232in)(65000 lb in2 )

Z 	 61.8lbs
2.21
Z '  Z  Adjustment Factors (Table 10.3.1)
 61.8lb  Cd  61.8lb 1.15 (Table 2.3.2)
 71lb

Drag load/Fastener capacity = #fasteners required
194lb / (71lb fastener)  2.73  3 fasteners

DESIGN EXAMPLE #7: Drag Loads over Steel Substrate Conditions:
Same as #6 except using 20ga steel substrate

Drag  194lbs (per Example #6)

Allowable Fastener Capacities;
t1  Panel thickness  0.0232in
t2  Substrate thickness  0.0359in
d  Nominal screw diameter  0.216in

Fu1

 Tensile strength, panel

 65, 000lb / in2

Fu 2

 Tensile strength, substrate

 45, 000lb / in2

Shear Resistance:
Per AISI S100 Section E4.3.1, t2
Tilting of Panel:

t1  0.0359in 0.0232in  1.55

P  4.2(t 3d )1 2 (F )
ns	2	u 2
 4.2(0.0359in3 x0.216in)1 2 x45000 lb in2
 597lbs

Bearing of Panel:
Pns  2.7(t1 )(d )(Fu1 )
 2.7(0.0232in)(0.216in)(65000 lb in2 )
 879 lbs

Bearing of Substrate:
Pns  2.7(t2 )(d )(Fu 2 )
 2.7(0.0359in)(0.216in)(45000 lb in2 )
 942 lbs

Because

1.0  t2

t1  2.5 , Pns

is calculated by linear interpolating between min(a,b,c) and the min(b,c):

Pns

 597lb  (879lb  597lb)(1.55 1)
2.5 1
 700lb

Pallow  700lb   700lb 3.0  233lb

Drag load/Fastener capacity = #fasteners required
194lb / (233lb fastener)  0.83  1 fastener

NOTE: Although example shows that one fastener has the capacity to withstand drag loads (233lb  194lb),
it should be noted that manufacturer installation guides generally specify (3) fasteners minimum to pin each panel.

DESIGN EXAMPLE #8: Thermal movement
This example calculates thermal movement of the steel roof or wall panel to evaluate proper clip and joggle cleat clearances.

Conditions:
150° maximum anticipated change in panel temperature
Change panel length  L    T  L, where
  Coefficient of linear expansion, in in per F
 6.7 106 in in per F for steel
L  Panel length, in
T = Maximum anticipated change in panel temperature, F

6.7x106 in
L 	150F  30 ft 
inF
 0.36 in thermal movement

12in 1 ft

DESIGN EXAMPLE #9: Roof Attachment (point loads)
This example calculates the allowable outward (negative) point load evaluated at mid-span.

Conditions:
Panel: 16in wide Span-lok hp 24ga Clip: Low profile clip
Fastener: #12 pan head Substrate: 19/32” plywood Panel attachment spacing: 4ft
Roof attachment device: S-5! #S-5-U Mini roof clamp Solar roof attachment evaluated at mid span (worst case)

Following the Load Path:

Roof attachment (S-5! roof clamp):

Allowable capacity loaded normal to panel seam is 849lbs (per S-5! online test results).

Evaluate bending capacity of roof panel using equations of mechanics:

M MAX

M MAX

 P(l) 8

F (Span-lok hp) S
   b	


l  Span  48in

b

F  Failure bending  50, 000lb / in2
S   Negative section modulus  0.0665in3 / ft (per Span-lok hp product sheets)
  1.67 (per AISI S100, Chapter C)
F  S-  (8)	50, 000lb / in2  0.0665in3 / ft (8)
P	=   b	

allowable

(l)	1.67 (48in)

Pallowable = 331.8lb

16" Span-lok hp & SpanSeam, 24ga, with Std. Clip	

Substrate	Fastener	Attachment Spacing, (ft-in)	
	#
per clip	
Size	1' - 0"	1' - 6"	2' - 0"	2' - 6"	3' - 0"	3' - 6"	4' - 0"	4' - 6"	5' - 0"	
			Panel / Clip Negative (Outward) Uniform Load Capacity, (lbs/ft2)	
			190	298	174	273	158	248	142	223	126	198	110	173	94	148	77	123	61	98	
			Panel Sys tem Negative (Outward) Uniform Load Capacity, (lbs/ft2)	
			ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	ASD
W/W	LRFD
W	

Clip/panel capacity:

Clip capacity derived from panel attachment table.

For a 4ft attachment spacing, the panel/clip capacity is 43lbs/ft2.
Clip tributary area = 4ft x 1.33ft (panel width). 43lbs/ft2 x 5.33ft2 = 229lb capacity

Clip-to-substrate capacities:
Fastener pullout strength per NDS Equation 11.2-2: 2850  G2  D
G = 0.45 (Plywood and OSB) as specified in The Engineered Wood Association APA #TT-051C
2850  0.452  0.216  124.6lbs / in
ASD Adjustment factors per NDS Table 10.3.1: Ctot  CD  CM  Ct  Ceg  Ctn
Ctot  1.6 1.0 1.0 1.0 1.0  1.6
Fastener pullout capacity = 124.6 lbs 1.6  19 in  118.3lbs
in	32
Determine fastener adjustment factor using engineering mechanics and clip dimensions.

P a 
R   b

Fastener adjustment factor = 1.625P

Clip-to-substrate capacity per tributary area =

where a=1.56, b=0.96

(# fasteners × fastener pullout capacity) prying factor

= (3118.3lbs)  218.4lbs (1.625)

To summarize the capacity of the load path segments:
S-5! roof attachment = 849lbs
Panel bending = 331lbs
Clip/panel = 229lbs
Clip-to-substrate = 218lbs

Based on this analysis, roof attachments (point loads) attached mid-span  are limited to 218lbs of negative (outward) loading.

MANUFACTURING FACILITIES:

AEP Span
10905 Beech Avenue
Fontana, CA 92337
800-733-4955

AEP Span
2141 Milwaukee Way
Tacoma, WA 98421
253-383-4955
800-733-4955

CORPORATE HEADQUARTERS:

ASC Profiles LLC
2110 Enterprise Boulevard West Sacramento, CA 95691 800-360-2477

Visit us at:
www.aepspan.com

S-5!® is a registered trademark of Metal Roof Innovations, Ltd .
AceClamp® is the registered trademark of Innouative Medical products Inc .

©2014 ASC Profiles LLC All rights reserved. July 2014 2M (BRXXX)