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Neal Mitchell Associates 1041 Sutton Street, Northbridge, MA 01534

Tel: 508-234-8646 Fax: 508-234-8759 e-mail: nmitchell2@aol.com

PROCEDURES FOR LATERAL LOAD ANALYSIS

Using The PRESCRIPTIVE METHODS

Of 780 – CMR (7th Edition)

The procedures that are identified in this document are presented to illustrate the requirements of 780 CMR 5602.10 Wall Bracing. The code requires an analysis for all loading, and this includes both vertical and horizontal loading. However, the code permits the use of a Prescriptive Method

for the lateral load analysis of “standard” buildings.

780 CMR 5301 DESIGN CRITERIA

5301.1 Design Buildings and structures, and all parts thereof, shall be constructed to safely support all loads, including dead loads, live loads, roof loads, flood loads, snow loads, wind loads as prescribed by 780 CMR 51.00 through 99.00. The construction of buildings and structures shall result in a system that provides a complete load path capable of transferring all loads from their point of origin through the load-resisting elements to the foundations.

The considerations for horizontal loading can be accomplished by an engineering analysis of shear walls, or by a Prescriptive Method that can be used for “standard” structures. The Prescriptive Method

provides a non-computational procedure that can be used in place of engineering computations for buildings that meet the conditions and limitations for this method that are defined by the code.

The reader should be aware that whenever the “standard” conditions that are defined by the Prescriptive Method

are not satisfied, then a more detailed engineering analysis is required. However, all buildings MUST be checked for lateral load resistance, just as they are checked for vertical loading.

The Prescriptive Method

of lateral load analysis is described in 780 CMR by Section 5601.10. This analysis procedure uses minimal computations and it is based on the sum of the Braced Panel lengths that meet a certain length requirement in clearly defined Braced Wall lines in any structure. To make it easy for you to follow this procedure, relevant sections of 780 CMR will be reproduced and inset as illustrated below. These sections will be followed by commentary to illustrate the implementation of the code requirements.

5602.10 Wall Bracing.

5602.10.1 Braced wall lines. Braced wall lines shall consist of braced wall panel construction methods in accordance with 780 CMR 5602.10.3. The amount and location of bracing shall be in accordance with 780 CMR Table 5602.10.1. Braced wall panels shall begin no more than

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12.5 feet (3810 mm) from each end of a braced wall line. Braced wall panels that are counted as part of a braced wall line shall be in line, except that offsets out-of-plane of up to four feet (1219 mm) shall be permitted provided that the total out-to-out offset dimension in any braced wall line is not more than eight feet (2438 mm).

A designed collector shall be provided if the bracing begins more than 12 feet (3658 mm) from each end of a braced wall line. 5602.10.1.1 Interior Braced Walls - Spacing. Spacing of braced wall lines shall not exceed 35 feet (10,668 mm) on center in both the longitudinal and transverse directions in each story. Exception: Spacing of braced wall lines not exceeding 50 feet shall be permitted where: 1. The wall bracing provided equals or exceeds the amount of bracing required by 780 CMR Table 5602.10.1 multiplied by a factor equal to the braced wall line spacing divided by 35 feet, and 2. The length-to-width ratio for the floor/wall diaphragm does not exceed 3:1.

Braced Wall lines are the building wall lines that are identified for lateral load resistance in a building. In the example that is used in this document, the red rectangles represent a 4’ width of Braced Wall line extents, and blue rectangles represent an 8’ width of Braced Wall line lengths. The spacing of these braced walls in a building should not exceed 35’. Braced Panels are located in the Braced Wall lines. These wall panels can be made from a variety of materials. The typical methods of residential construction that are identified in 780 CMR include wall systems and materials that are used in other parts of the country for residential construction. For Massachusetts, the most prevalent method of sheathing is Method 3 where the building is sheathed with Wood Structural Panel Sheathing

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5602.10.3 Braced Wall Panel Construction Methods. The construction of braced wall panels shall be in accordance with one of the following methods:

1 Nominal one-inch-by-four-inch (25.4 mm by 102 mm) continuous Diagonal Braces let in to the top and bottom plates and the intervening studs or approved metal strap devices installed in accordance with the manufacturer’s specifications. The let-in bracing shall be placed at an angle not more than 60 degrees (1.06 rad) or less than 45 degrees (0.79 rad) from the horizontal.

2 Wood boards of 5/8” inch (15.9 mm) net minimum thickness applied diagonally on studs spaced a maximum of 24 inches (610mm). Diagonal boards shall be attached to studs in accordance with 780 CMR Table 5602.3(1). (Fastener Schedule)

3 Wood Structural Panel Sheathing with a thickness not less than 5/16 inch (7.9 mm) for 16-inch (406 mm) stud spacing and not less than 3/8 inch (9.5 mm) for 24-inch (610 mm) stud spacing. Wood structural panels shall be installed in accordance with 780 CMR Table 5602.3(3). (Stud Spacing)

4 1/2 (12.7 mm) or 25/32-inch (19.8 mm) thick Structural Fiberboard sheathing applied vertically or horizontally on studs spaced a maximum of 16 inches (406 mm) on center. Structural fiberboard sheathing shall be installed in accordance with 780 CMR Table 5602.3(1). (Fastener Schedule)

5 Gypsum board with minimum1/2-inch (12.7 mm) thickness placed on studs spaced a maximum of 24 inches (610 mm) on center and fastened at seven inches (178 mm) on

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center with the size nails specified in 780 CMR Table 5602.3(1) for sheathing and 780 CMR Table 5702.5 for gypsum board. (Fastener Schedule)

6 Particleboard wall sheathing panels installed in accordance with 780 CMR Table

5602.3(4) (Stud Spacing) 7 Portland cement plaster on studs spaced a maximum of 16 inches (406 mm) on center and installed in accordance with 789 CMR 5703.6 (Requirements for Exterior Plaster)

8 Hardboard panel siding when installed in accordance with 780 Table 5703.4. (Fastener Schedule)

Exception

: Alternate braced wall panels constructed in accordance with 780 CMR Table 5602.10.6 shall be permitted to replace any of the above methods of braced wall panels.

Building wall panels, with a length that exceeds the minimal length specified by the code, are defined by the code as Braced Panels. Therefore, any conventionally built panel can be considered as a Braced Panel if it has the proper length. The definition of a Braced Panel is any normally constructed panel that exceeds the code specified minimal panel length. In general, any panel that has a construction length that is equal or greater than 48” can be called a Braced Panel. Reductions in this dimension are possible based on the percent of window or door opening that is adjacent to the panel.

MINIMUM LENGTHS OF PANELS

5602.10.4 Length of Braced Panels. For 780 CMR 5602.10.3 Methods 2., 3., 4., 6., 7. and 8., each braced wall panel shall be at least 48 inches (1219 mm) in length, covering a minimum of three stud spaces where studs are spaced 16 inches (406 mm) on center and covering a minimum of two stud spaces where studs are spaced 24 inches (610 mm) on center. For 780 CMR 5602.10.3 Method 5 (Gypsum Panels). each braced wall panel shall be at least 96 inches (2438 mm) in length where applied to one face of a braced wall panel and at least 48 inches (1219 mm) where applied to both faces.

Exceptions:

1 Lengths of braced wall panels for continuous wood structural panel sheathing shall be in accordance with 780 CMR 5602.10.5. 2 Lengths of alternate braced wall panels shall be in accordance with 780 CMR 5602.10.6.

It should be noted that gypsum walls with a single side sheathed with gypsum wallboard must be 96 inches long to be considered as Braced Panels. However, walls with gypsum sheathing on two sides need only be 48” wide (long) to be considered as Braced Panels. Note that Braced Wall Lines can include both interior and exterior walls.

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Note that the code assumes that exterior panels, that are sheathed with gypsum on the inside face and faced with wood on the exterior, still need to be 48” wide (long) to be considered as Braced Panels. This code length limitation is based on the fact that the code considers a full height opening that is adjacent to the 48” Braced Wall Panel. However, as sheathing is added above and below the opening next to a Braced Panel this additional wall sheathing permits the length of the Braced Wall to be reduced. This reduction in required length for designation as a Braced Panel is covered in 780 CMR Table 5602.10.5.

This table permits interpolation between standard building floor heights. This table permits interpolation between 8 feet to 10 feet. Wall heights shorter than 8 feet and taller than 10 feet require more exact procedures because they do not fall within the code defined “standard” limits. This table illustrates that the standard Braced Panel is defined as a 48” wide panel for an 8 foot high wall with 100% opening. Higher walls require wider panels. As the adjacent opening is decreased then a Braced Panel can be as short as 24”. This occurs in an 8 foot high wall with an adjacent small window. In some Braced Wall lines the requirement length of Braced Panels is not sufficient so the code permits proper strengthening of shortened panels so that they can be considered as Braced Panels. Therefore, a panel that does not qualify as a normal Braced Panel can be made into a Braced Panel with proper stiffening. These modified panels use their actual length and the method of supplemental stiffening must be identified. These short panels can be stiffened with metal “X” brace strapping, thicker skins, gluing the skins to the studs, and with proper nailing. Generally these panels utilize double studs on all four sides as well as a nail spacing that is reduced to 3” with nails staggered into both of the members on all four sides. (See illustration on the next page)

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PANEL STRENGTHENING PROCEDURES The code also sets limitations on the sum of the Braced Wall Panel length in any selected section of the building that has been designated as a Braced Wall. This requirement is identified in 780 CMR Table 5602.10.1 Wall Bracing. A partial Table is illustrated below with the addition of the Design Case,

so that the designer can identify the section of the Table used for the analysis. Note that as the wind speed increases the length of Braced Panel increases so that the code reflects the specialized location and its code specified wind speed.

It should be noted that this table contains more information for different wind speeds and conditions, but these two cases have been separated out for this presentation because they

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reflect the wind speeds and the conditions that are normal in Central Massachusetts. The reader is urged to review 780 CMR and become familiar with all of the options.

Note that for Design Cases 1,2,3, with Method #3, the requirement is 16%, and for other materials the requirement is increased to 25%.

It is my opinion that the Prescriptive Method

recognizes the Exposure Designation B as the basis for design. It is clear from 780 CMR Table 5611.7.4 that as the exposure changes, so does the wind load. A 100 mph wind with Exposure B has the same pressure of 19 psf, as does an 85 mph wind with Exposure C. The 120 mph wind with Exposure B has the same pressure (27 psf.) as a 100 mph wind with exposure C. A 140 mph wind with Exposure B has the same pressure (37 psf.) as a 110 mph wind, with Exposure D.

In general the difference in pressure suggests that the Exposure C wind speeds exceed the Exposure B wind speeds by 20 mph. The Exposure D wind speeds exceed the Exposure B wind speeds by 30 mph. The best way to reflect these increases in pressure is to increase the required length of Braced Panels. Using 780 CMR Table 5602.10.1 the Braced Panel length is 16% of the Braced Wall for winds that are less than 100 mph and this length must be increased to 25% for winds that are less than 110 mph. The increased pressure, due to exposure, should probably be reflected in an increase in the required Braced Panel Length along any Braced Wall Line. The increased pressure from 19 psf to 26 psf would then be reflected in an increase of the required Braced Panels in a Braced Wall by 37%. From 26 psf. to 31 psf. represents another increase of 19% Therefore, a type B Exposure would require 16% length of Braced Panels in any Braced Wall length. A type C Exposure for the same wind speed would require 22% length and a type D Exposure would then require 26% length of Braced Panels in any Braced Wall Length to meet the requirements of the Prescriptive Method. Generally these increased loads require stiffening modifications to the panels to meet the requirements of the increased pressure.

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It is also possible to reduce the required Braced Panel length requirements in a Braced Wall. Section 5602.10.5 sets the criteria for this reduction.

5602.10.5 Continuous Structural Panel Sheathing. When continuous wood structural

panel sheathing is provided in accordance with 780 CMR 5602.10.3 Method 3. on all sheathable areas of all exterior walls, and interior braced wall lines, where required, including areas above and below openings, braced wall panel lengths shall be in accordance with 780 CMR Table 5602.10.5. (Below)

Wood structural panel sheathing shall be installed at corners in accordance with 780 CMR Figure 5602.10.5. The bracing amounts in 780 CMR Table 5602.10.1 for 780 CMR 5602.10.3 Method 3 shall be permitted to be multiplied by a factor of 0.9 for walls with a maximum opening height that does not exceed 85% of the wall height or a factor of 0.8 for walls with a maximum opening height that does not exceed 67% of the wall height. Multiply by (0.9) When the opening does not exceed 85% of the Wall Height Multiply by (0.8) When the opening does not exceed 67% of the Wall Height

This reduction is permitted when the adjacent paneling, above and below the opening in the wall is limited. In the case of the 16% requirement for Braced Panel length the reduction is to (16% x 0.9 = 14.4%) in walls with doors and to (16% x 0.8 = 12.8%) when the wall only contains windows. This reduction in Braced Panel requirements can also be complimented by converting shorter in width panels into Braced Panels by stiffening these narrow panels with reinforcement. Properly modified panels can be used as Braced Panels. Modified panels use their actual length in the compilation of Braced Panel Length in a Braced Panel Wall line. Some designers use these strengthening procedures on normal Braced Panels in special conditions. For example, increasing the skin thickness increases the panel’s carrying capacity for both horizontal and vertical loads. Double studs, metal cross bracing, proper closely spaced nailing, and gluing the skins increases the lateral load resistive capability. Generally these strengthening procedures are used by designers to increase the specific wall panel capacity at specific locations. The minimal requirements for Braced Wall lengths and the ability to strengthen non compliant panels to make them compliant insures that most residential structures that are built in New England easily meet the lateral resistance requirements of the code. Therefore, most buildings can be analyzed and validated by the Prescriptive Method

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Buildings that do not comply with the requirements of the Prescriptive Method should be analyzed using normal engineering shear wall procedures.

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REVIEW

The Prescriptive Method of lateral load analysis, as defined by the code, is both simple and straightforward. It can only be used for “standard” buildings. If the building does not “fit” the requirements of the Prescriptive Method then it must be properly engineered by a professional. The Prescriptive Method

is provided in the code so that the engineering analysis of lateral loads on buildings can be significantly simplified and reduced in the costs that are needed for analyzing “standard” buildings.

Every building should have Braced Wall Lines that are between 20’ to 25’apart. These Braced Wall Lines must be identified on the Architect/Designers plans. The lateral loads on a building are assumed to be resisted by these Braced Wall Lines. The flooring of a building is assumed to act like a diaphragm that transmits the lateral loads to the Braced Walls that are in the Braced Wall Line. Walls of standard construction, with lengths of 48” (with revised lengths that are dependent on opening size and story height) are called Braced Walls. Shorter walls can be converted into Braced Walls with proper modifications and stiffening. Generally these shorter walls also require positive connections to the foundation. Depending on wind speed the percentage of Braced Panels in every Braced Wall Line is defined by the code. Generally the Braced Wall Panels must compose more than 16% or 25% of the overall Braced Wall Length but reductions in this requirement are provided by the code. These simple rules do not require computations, but 780 CMR requires that the designer verify that any submission for a Building Permit contain both visual and written verification that the building complies with the lateral load requirements of 780 CMR

. Therefore, this method only requires the designer to check and consider dimensions to validate the building for appropriate lateral resistance.

The key to a proper submission for a Building Permit requires a clear and simple presentation that can be used to verify code compliance. The sample submission illustration that follows is a simple example of how we prepare and present drawings for submission to a Building Inspector. This submission is designed to verify proper code compliance.

THE PROCESS

To be certain that we are using the proper plans we take the first floor and, when necessary, the second floor plan of the design submission and use these actual drawings as a base drawing for lateral load evaluation. We then overlay the code conditions on this plan so that we can visually illustrate the considerations for building compliance with the code. Our final report is in PDF (Portable Document Format) so that the Report can be printed on any printer in normal letter sized paper.

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We work in a variety of countries around the world, so we transfer all information between people working on any project using the Portable Document Format

(PDF) of Adobe Systems. Readers for this format are available on the Adobe Web Page for downloading, at no cost to the user.

The designer’s paper plans can be scanned to get them into PDF format or the designer can provide the plans in PDF format directly from their drawing systems. This PDF format is a compressed format so the drawings are quickly transferred using the internet. In general, most professional offices now transfer all drawing information using this format and the internet. Our process starts by cropping the designers plan (in PDF Format) so that only the plan and dimensions remain. We crop the drawing to remove title blocks and any irrelevant information. We then save this cropped file in a JPEG image format. The goal of this initial work is to get a clear image of the floor plan that preserves the dimensions, walls, windows and other plan features of the building as defined by the building designer. We import this JPEG image, at normal size, into our drawing program as the first layer. By maintaining the drawing size we maintain the drawing scale, and this permits us the added advantage of scaling the drawings on the computer screen. All of our ongoing drawing is done on a different drawing layer so that the designers plan serves as the base for our study. A sample of such a cropped plan is illustrated below.

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Certainly it is possible to just duplicate the designer’s base floor plans and do the review using these documents. However, by using the PDF format we can insure that our Report can be printed on any 8 ½” x 11” color printer to produce a document that can be easily inserted into the Building Inspectors file for the project. Once we have a proper plan we add the identification of the Braced Wall Lines. Note that the 4’ wide rectangles that define some Braced Wall Lines are in Red and the 8’ wide Braced Panel Wall lines are in Blue. The special considerations for a chimney are in Orange, the wall with the garage doors is in Lavender and any covered porch area would be in Green. (The Green is not used in this example). The idea is to use color to greatly simplify the both the identification and the review of the submission by the Building Inspector. Also note that whenever possible the 4’ rectangular strip is used to further simplify the colored overlay for the Braced Wall identification. Each rectangular section is labeled with a letter for easy identification.

SAMPLE PLAN WITH BRACED WALL LINES IDENTIFIED

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This colored overlay greatly simplifies the identification of Braced Wall Lines, and they represent a clear identification of the Braced Wall Lines that are being considered for the analysis for code compliance. The drawing is put on a page with a title block that clearly designates this submission as a lateral load study. Once the Braced Wall Lines are identified and labeled the length dimensions of the Braced Wall Lines are added in both feet and inches in the Yellow ovals. These ovals are illustrated on the following drawing.

Then the green ovals are located on the walls that are considered to be Braced Panels. (See Drawing on next page). The actual dimension of the walls, as measured from the plans, are the numbers in the green ovals.

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The resulting plan has the Braced Wall Lines clearly identified and the Braced Wall Panels are also clearly identified with their locations. This presentation makes the submission easy to check and the assumptions of the Prescriptive Method

are easy to evaluate.

The fact that the drawing is in PDF format permits it to be printed using the 8 ½” x 11” format, on a colored printer or on any other printer and plotter. On occasion we have presented these drawings at the original size, but this scale and large format really don’t make much sense considering the fact that this document is best kept with its supporting documentation in normal letter format. The information from this Final Submission Plan

is then entered into a standard spreadsheet that consolidates the plan information into a format that directly relates to the sections of the code that serve as the control. Note that the relevant code references on the spreadsheet are in Red.

This spreadsheet requires identification of the Exposure and Design wind speed, as well as the Bracing Method that was selected for the analysis. The key dimensions and code defined considerations are generated from the information that is entered. This structured format simplifies the mathematical review of the information on the plan as it relates to the code.

FINAL SUBMISSION DOCUMENT

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The second page on this spreadsheet permits the entry of the Braced Panel Lengths in the columns for the various Braced Wall Lengths that relate to the Braced Wall identifications that have been added to the plan for the final drawing submission. Although the Braced Panel reductions are provided in 780 CMR Table 5602.10.5, this illustration assumes that only panels of 48” or above are considered. The minimum length panel is only for reference. It should be noted that no panels shorter in length than 48” were used in this analysis. It is important to note that on the analysis plan, panels are identified down to 40”. When the longer panels do not meet the Braced Wall Length percentages required by the code then the shorter panels that are permitted by 780 CMR Table 5602.10.5 are considered. In most

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buildings with sheathed walls the longer panel lengths meet the requirement of the code in terms of required Braced Panel length in any Braced Wall. This assumption certainly simplifies the Review by the Building Inspector, and if the code requirements are not met, the designer has the ability to reduce the Braced Wall requirements, (780 CMR 5602.10.5). In addition the shorter length panels permitted by CMR TABLE 5602.10.5) can be included in the analysis by adding these additional Braced Walls. Further Braced Panels can be added by stiffening some of the shorter panels with procedures that stiffen these non-compliant panels in a way that makes them compliant. It is rare for a building not to comply when everything available to the designer is considered. It is important to note that on the Presentation Plan that panels are identified down to 40”. However, in the analysis phase only the longer panel lengths needed to be considered in order to meet the requirements of the code so it was not necessary to consider these shorter panels. Most residential units that are built in New England have sufficient lengths of Braced Panels so that the requirements for Braced Panels can easily be met. Residential requirements for proper Bracing Wall lengths are usually only a problem in designs with multiple large wall offsets on any elevation, or where multiple windows are present. In cases like this, an internal portal frame can be used to provide proper lateral stiffness. The Braced Wall considerations usually have issues when considering the garage face-walls. Putting garages under living units is a practice in New England, but the CMR 780 Table 5602.10.5 actually reflects the standard building practices that are used in both Florida and California. Special considerations are required when the garage is placed under living units.

Footnote (b) restricts the use of this Table to one story garages that have a minimal of added dead load on the roof. In addition, this table restricts consideration to walls that are between 8’ and 10’. Unfortunately it seems that many people try to use this Table improperly by interpolating dimensions below the standard 8’ dimension. When there is living space above the garage, this Table cannot be used, and the complying Braced Wall dimension is 48”.

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The common use of thin face panels on the face of a garage usually requires special detailing. The Prescriptive Method sets the limits of the panel length to 48”, and few garage face-panels offer this dimension. To address this issue the APA developed a design and then conducted a series of tests to validate this design. Many garages are now framed using this Portal Frame Design

and the details of this design are also often used in large houses with multiple window openings.

The APA design for Portal Frame openings permits face-panel width reductions down to 16” for an 8’ height and 20” for a 10’ height. This is based in a 6:1 ratio rather than the code specified 4:1 ratio. The real key to the APA design is the nailing and anchor bolt requirements that are designed to increase the joint fixity at both the base and the beam wall connection. The use of a continuous LVL permits the designer to accommodate this design to spans over large window openings. Commercially available shear panels can be used to provide shear resistance in buildings but they are not the most efficient way to resolve large openings. When large openings are framed by face-walls that have widths between 16” to 20” the more conventional nailing procedures used by the APA Portal Frame seem to be as structurally efficient as well as being more cost competitive. The real key to the APA design is the requirement for proper nailing. Whenever these designs are used it is critical to make certain that the nailing patterns are properly implemented. The goal

THE APA PORTAL FRAME

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of the nailing is to create a fixed connection between the vertical panel and the foundation, as well as between the vertical panel and the LVL beam. To achieve this with nails requires the extensive nailing pattern that was used for the APA testing program. This same APA detail, although specifically developed for garages, can also be effectively used in building walls to increase rigidity within a wall. The use of this detail over a large window-gang opening has provided an effective solution in walls where it made sense to stiffen the walls because of the opening size. Again the use of the LVL header and properly nailed sheathing to create the proper connection provides a good solution that is within the capability of normal framing. This APA Portal Frame is also an ideal solution for garage openings where living floors are added over the garage. Therefore, this design goes beyond the one story limitations of 780 CMR Table 5602.10.5. With suitable increases in the face panel thickness, this design is also appropriate for garages with two floors of living above the garage. This design solution appears to be appropriate for most design situations, and its cost and construction requirements are both reasonable cost as well as being within the capabilities of most framers. This APA Portal Frame design brings the face-panel widths of garages from 43” down to 16” to 20” depending on the wall height. This dimension reduction appears to be appropriate for most garage face-panels. However, many designers want even thinner face-panels, so there was a need to develop another design with an even smaller face panel width. To meet this need the Koopman Team has developed a 3 x 5x ¼” steel tube column design that permits face wall widths as low as 10”. This design was checked for lateral deflection, and these computations illustrated that this steel column structure was even more rigid to lateral load deformation than the computation of an idealized APA Portal Frame.

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At the present time the team has standardized this design so that a single solution can be used for variable heights. This structure can also carry up to two additional living floors. This solution has also been value engineered so that its use should prove to be the most time and cost effective way to frame the face-panels of garages. When the analysis is completed this documentation is delivered to a Building Inspector. Generally this analysis also requires an appropriate explanation and certification letter. The designer should provide the Building Inspector with a basic narrative that describes the considerations that were used in developing the solution. It is important for the designer to provide a written statement as part of any submission. A typical letter for the lateral load submission has been included for your review. This is presented as an example of the way that we address the issue of proper communication of this process to the Building Inspector. It is obvious that this letter can take a number of forms to be satisfactory. Please also note that the final Report for the Building Inspector and the entire Report itself can be transmitted by e-mail in PDF format, so that it can easily be conveyed over the internet.

EXAMPLE LETTER

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Proper lateral load evaluation of a building is part of 780 CMR. The Prescriptive Method

permits a non-computational approach to this certification. If your building doesn’t comply with the limitations of this method then a more detailed engineering analysis is required. Be aware that the reports from ongoing testing often permit the use of test results to validate considerations that are not covered in the code. The test information that is used for lateral load design of wood structures is constantly changing with upgrades based on actual full scale test results.