Structural Design of Light Gauge Steel

Structural design of Light Gauge steel/Cold formed steel

Since the light gauge steel members are usually so thin, these thin elements may buckle at stress levels less than the yield point if they are subjected to compression, shear, bending or bearing. Local buckling of these thin elements is one of the major design criteria.

Light gauge steel software:

1-RISA, the fastest. But, it can only design member made of single section. No two sections such as back to back or box beams is available at the present time. Also, RISA dose not check crippling.

www.risatch.com

2-CFS, the most sophisticated software for Light Gauge steel. It does design almost any shape of Light gauge/ cold=formed steel shape. Also, it does check web crippling.

RSG Software, Inc. 2803 NW Chipman Road Lee's Summit, MO 64081

1-For simple residential homes, the International Residential Code, IRC, provide a prescriptive Method for light gauge steel/ cold formed steel.

Section R603.1 General:

The provisions of this section shall control the construction of exterior steel wall framing and interior load-bearing steel framing for buildings not more than 60 feet long perpendicular to the joists or truss span, not more than 40 feet wide parallel to the joist or truss span, and not more than two stories in height. All exterior walls installed in

accordance with the provisions of this section shall be considered as load-bearing walls. Steel walls constructed in accordance with the provision of this section shall be limited to sites subjected to a maximum design wind speed of 110 miles per hour, Exposure A, B, or C and a maximum ground snow load of 70 psf.

2- For big residential homes or commercial, The International Building code, call for the Cold-Formed Steel Design, AISI Manual, by

American Iron and Steel Institute

The 2002 edition of the Cold-formed Steel Design Manual consists of six parts:

Part I, Dimension and Properties for cold formed steel Part II, Beam Design, Cold formed steel.

Part III, Column Design, Cold formed steel. Part IV, Connections, Cold formed steel

Part V, Supplementary Information, for cold Formed steel Part VI, Test Procedures, for cold formed steel.

Light Gauge/ Cold Formed steel 7-50 GENERAL

a- There is free Technical Assistance from the Steel Framing Alliance. 1140 Connecticut Avenue, NW, Suite 705, Washington, D.C. 20036

7-52-Light Gauge Steel connections.

a- Simpson has a special catalog for light gauge steel, please use it. Do not use the Simpson wood catalog for light gauge steel unless you call the technical support of Simpson company and they say it will work.

7-53 -Light Gauge Steel studs.

A-The top of wall track in a light gauge steel wall cannot support loads therefore wall studs MUST be lined up with joist/rafters/trusses or any load from above AT ALL FLOORS.

B-Most contractors like the spacing between the studs to be 24 inches not 16 inches. This is also good because it matches the trusses spacing which is usually spaced at 24 inches on center.

C-To increase capacity of studs: 1. Increase gauge of studs.

2. Double studs @ spacing required by framing members above. For example: If the floor spacing is 24" O.C. and stud spacing is required to be 12" O.C. to achieve the loads required you cannot space studs @ 12" O.C. instead you use double studs @ 24"o.c. to match framing members above.

D-If spacing of studs does not match framing members above use an appropriate header such as L-Shape header to transfer the load to studs.

E- Multiple studs can be used as a column to support loads from beams or girder trusses above provided:

1. If the multiple studs are stacked parallel to the length of the beam or the length of the truss, the length of the beam or the truss must be extended to span over the entire number of studs needed to support the beam or the truss.

2. If the multiple studs are stacked perpendicular to the length of the beam or the length of the truss, the width of the beam or truss can not be more the total width of the beam or the total width of the truss.

3. To calculate the capacity of multiple studs, just use the capacity of single studs multiplied by the number of studs. Do not use the combined moment of Inertia to count for the composite section. Just simple

calculation.

If the above conditions cannot be met, use PACO column or steel tube column instead of multiple studs. F- When you are using the light gauge straps as bracing, Studs

lateral bracing shall be provided by bridging only. From the basic details, keep the bridging details only and remove the blocking/strapping and the sheathing details that are used to laterally brace the studs.

7-54 Showing up wall size on plane:

Wall shall be shown by a line with two arrows specifying the start and end of wall. The line shall have a wall designation mark such as W1 or W5. A table showing wall designation with the size of the studs shall be shown on the floor plan. See project from John hanson.

Be Careful. If you use Pre-engineered products such as Hardy panel or PACO steel or other products, You cannot use the entire wall length at garages. This is because the rough openings for garage doors are 4 inches wider than the garage door size shown on the architectural drawings.

A-Not used.

B- Joist spacing shall be 24 inches on center to match studs spacing which is 24 inches on center. Please do not deviate from the 24 inches on center unless you have a strong reason to do so. For any reason, if the joist spacing is different from stud spacing, you need a header between the studs to support the joist. You can use L- Shape header .

At the tub area, do not reduce the joist spacing as we do on wood construction. Instead, double up the joist at the same spacing so the double joist is supported by a stud. Do not double too many joists. About three double joist at the tub are is enough.

For phoenix steel, they use joist track. Please refer to their file in the client preferences. C- Method to increase joist strength to stay within the 24 inches spacing are:

1. Increase the joist gauge; 2. Increase the joist depth;

3. Or double the joist up at long span location 4. Add beam to reduce joist’s span;

5. Switch the joist direction 90 degrees. You may get shorter span. 6. Use PACO beams.

D- If a light gauge steel brace start at a beam, this beam must be a W-shape not a PACO beam. This is because: 1. The strap causes bending moment on the top flange of the beam. W-Shapes are better because it

has thicker flanges.

2. The calculation is under our control. We do not have to wait for PACO to do the calculation. E- Do not use multiple studs ( Built up stud column )under beams that support the light gauge bracing because of the uplift. Use PACO column or regular tube steel. Either one of these columns will have two blot to connect to the beam to resist the uplift forces from the brace.

F – For projects with 1/8 scale, show the first and last joists only. These two joists shall be connected with a line with two arrows, one arrow shall be pointing to the first and the second arrow will be pointing to the last joist. The line shall contain the joist designation.

7.56 Number of braces per wall ( one side or two sides of the wall:

A- For the following buildings

1. For single story house 2. Two story house 3. Shops.

4. Two story apartment complex and hotels.

Brace on exterior side of the wall only ( two total per wall in a cross configuration) is preferred by most of contractors. This is especially possible for area of low seismic load and or when wind control

This is because the inside brace interfere with the sheet rock on the inside face of the wall.

The current PSE criteria is that if horizontal force can be resisted by a single 3 inches wide gauge 16 strap, then use one strap on the exterior side of the wall only.

If the force need more than one 3 inches wide gauge 16 strap, then the force is big and we are worried about the studs to be twisted. In this case, use two straps, one each side wall better

B-For larger structures and /or three stories buildings, Braces on both sides of the wall ( Two on each side on the wall in a cross configuration, four braces total per wall ), is recommended. This is because brace on one side of the wall produce eccentric axial force on the studs.

If the contractor object to braces on both sides of the wall. And if there are enough walls in the building, one idea is increase the number of braces in the lower stories and less number of braces on the top story with braces on the exterior side of the walls only.

Another idea is to keep the top story braces on the exterior side of the wall only. While for the lower story the straps can be on both sides of the wall.

7-57 Roof:

7-57-20 Roof framing with rafters and purlins:

a- Z section is better than C section because you can easily lap the Z section at support with the Z section face to face. If you lab the C section they have to back to back. This require the seam lines of the roof metal deck to be shifted between panel which is impossible to achieve.

b- Rigid insulation above the roof deck is better and more economical than the pat insulation below the metal deck between the purlins and or rafters.

7- 59-10 Mixed System of Red-Iron and light gauge steel.

a- It was very difficult if not impractical to design a connection for stacked red-iron braced frame in a floor by floor plate form fashion of construction. However, stacking light gauge steel braced frame in the upper top stories over red-iron braced frames in the lower story is promising. Be cupful, the low R factor for the light gauge steel will be

applicable for both the red iron and the light gauge steel. So this mixed use of light gauge steel is doable for slab on grade project.

For project when the steel starts on concrete parking garage below, the mixed system will produce high reactions that require huge concrete beams in parking structure roof.

7-60 Connection between floors when using light gauge steel bracing.

"Connection of the diagonal bracing member, top chord splice, boundary members and collectors shall be designed to develop the full tensile strength of the member OR sigma times the otherwise prescribed seismic forces."

However in the seismic design Manual example 3, they ignored the second option of designing for the full strength of the member which in many cases may be smaller than the Amplified seismic forces.

1. The example just multiply the uplift forces by the Seismic Amplification factor. In this case, the seismic forces is at the allowable stress level.

2. The example for boundary elements ( multiple studs or steel post) , used the seismic amplification factor above to increase the load. However, the example increased the allowable load the member can carry by 1.7 . I recommend this way.

For compression member, the full capacity is defined as the allowable axial load Fa multiplied by the 1.7 factor. Remember that Fa could be less than the yield strength Fy based on the buckling stress. Please refer to UBC Page 2-255. Also, refer to Steel manual ASD.

For studs the easiest way to get the allowable axial compression load is from the stud tables. For any other member such as PACO column get it from PACO Tables.

For other members, you can use RISA software very easily.

1. For tension straps, the example used the Seismic amplification factor above to increase the load. However, they did not increase the capacity by the 1.7 factor. I recommend this way.

If you cannot use the above method for any reason, instead of using the amplified seismic load, you can use the full capacity of the diagonal brace to design the strap. For tension member, the full capacity of the member is defined as area of steel multiplied by the yield strength . Then, calculate the vertical component of the diagonal brace to choose the strap.

Note that for Los Angeles, they reduce the capacity of every thing. So. Please check LARR( Los Angles research reports)

The most economical way to resist the uplift forces is to use straps. It could be used on one side only or on both sides of the wall for big forces.

Also, Holdowns like S/Htt22 or S/ HD8 or 10 could be used.

If you have a wall start on the top of a steel beam at the second or third story, straps will not work and Holdowns will be the best. This is because the contractor can wild the threaded rod to the beam in the shop and connect the holdown in the field.

7-61 Chord and Chord Splices when using light gauge steel bracing. Seismic amplification factor = 2.2 for braced framed.

"Connection of the diagonal bracing member, top chord splice, boundary members and collectors shall be designed to develop the full tensile strength of the member OR sigma times the otherwise prescribed seismic forces."

However in the seismic design Manual example 3, they ignored the second option of designing for the full strength of the member which in many cases may be smaller than the Amplified seismic forces.

1. Must multiply the seismic forces by the Seismic Amplification factor In this case, the seismic forces is at the allowable stress level.

2. For chord member , use the seismic amplification factor above to increase the load. However you can increase the allowable load the member can carry by 1.7

3. For chord splices, Use the Seismic amplification factor above to increase the load. However, do not increase the capacity by the 1.7 factor. Or you can use the full capacity of the chord to design the splice.

If you can not use the above method for any reason. instead of using the amplified seismic load, you can use the full capacity of the chord to design the chord splice. For tension member, the full capacity of the chord is defined as area of steel multiplied by the yield strength factor.

Note that for Los Angeles, they reduce the capacity of every thing. So. Please check LARR( Los Angles research reports)

7-62 Connection at foundation when using light gauge steel bracing. Seismic amplification factor = 2.2 for braced framed.

1- "Connection of the diagonal bracing member, top chord splice, boundary members and collectors shall be designed to develop

the full tensile strength of the member OR sigma times the otherwise prescribed seismic forces."

However in the seismic design Manual example 3, they ignored the second option of designing for the full strength of the member which

in many cases may be smaller than the Amplified seismic forces. 2-

a- Must multiply the uplift forces from wind or seismic by the

Seismic Amplification factor In this case the seismic forces is at the allowable stress level. b- For Holdowns,

1. When seismic control, use the Seismic amplification factor above to increase the seismic uplift forces. However, do not increase the capacity of the holdown by the 1.7 factor.

2. When wind control, use the Seismic amplification factor above to increase the wind uplift force. Also, increase the capacity of the holdowns by the 1.7 factor.

3. Remember to add a holdown at each corner of the building even if the calculation does not require it.

4. Also, add a note on plan that "At braced frame provide anchor bolts per braced frame schedule. At other locations where wall is on concrete provide 5/8" diameter anchor bolt at 6'-" on center and within one feet of the beginning and the end of wall."

7-70 Modeling the building on RISA when using light gauge straps (please see models created for KF204-369)

7-70-1 General:

I have created a worksheet to guide you through the calculations required to design a "light gage steel tension only braced frame". The worksheet covers most any situation you may encounter when designing this type of system. You can find the worksheet in the project package / Engineering worksheets / LA Braced Frame Worksheet (final

version). A sample copy is also attached in this chapter’s appendix.

We had some difficulty with running the RISA model. We shared these difficulties with RISA technical staff through several e-mails. Their answers to these challenges are collected in the Pink Binder titled " RISA Technical Support ". Please refer to this binder before you star modeling on RISA so you do not faces these tough challenges.

7-70-10 Short walls at garages:

There are three options at garages doors.

1. If you have four feet of wall or so, use light gauge steel brace. 2. If you have shorter walls, you have two options:

1. PSCO frame, or 2. Hardy panel

Our experience showed that PACO frame work better in RISA model.

Be careful. If you use Pre-engineered products such as Hardy panel or PACO steel or other products, You cannot use the entire wall length at garages. This is because the rough openings for garage doors are 4 inches wider than the garage door size shown on the architectural drawings.

7-100 Strap Bracing for lateral loads, wind and Seismic for Light gauge steel wall construction. 7-100-1 General:

Uniform Building Code sections 2219 and 2220

1. Light gauge steel building is a wall system not a braced frame system. That is why the two stories limit of the braced frame with tension member only of UBC 2213.8.2.3 and UBC 2213.8.5 does not apply. 2. Building shall not be over five story height. UBC.

3. R, Over strength/ Ductility factor, = 2.8

International Building Code:

a- Building height limitation is 65 feet. b- R, Over strength/ Ductility factor, = 4.0

7-100-10 Diagonal Bracing Design

The Code section will be mentioned followed by comments by Precision Structural Engineering, inc. UBC 2220 Special Requirements In seismic zones 3 and 4

( Diagonal strap, stud or cables)

1- "The L/r of the brace may exceed 200 and is unlimited."

Comments: Any thickness and width that satisfy the force requirements will be used. We usually use gauge 16.

1. "All boundary members, chords and collectors shall be designed and detailed to transmit the induced axial forces."

4- See connection section below.

1. "Both flanges of studs in a bracing panel shall be braced to prevent lateral tensional buckling. Wire tied bridging shall not be considered to provide such restraint."

Comments: Bridging screwed to the metal studs are provided at 4’-0". In addition:

1. For exterior wall, the exterior side of the studs are laterally braced by the wire mesh screwed to the studs and the interior face of the studs are laterally brace by the sheetrock that is screwed to the studs. 2. for interior walls, both sides of the studs are laterally brace by the sheetrock that is screwed to the studs.

7-100-11 Brace Connections:

The Code section will be mentioned followed by comments by Precision Structural Engineering, inc. UBC, 2001, Section 2220

2- See Section 7=100-10 above

3—"Connection of the diagonal bracing member, top chord splice, boundary members and collectors shall be designed to develop the full tensile strength of the member or sigma times the otherwise prescribed seismic forces." Comments:

1. All connections are designed to develop the maximum capacity of the brace. In addition we add a few more screws.

2. Capacity of the screws are obtained from Part IV of the American Iron and Steel Institute. Please see copy attached with this calculation.

4-"Vertical and diagonal members of the braced bay shall be anchored so the bottom tack is not required to resist uplift forces by bending or track web."

Comments: The Brace force is transferred to the Gusset plate then to studs and the holdowns without transferring any force to wall track. Please refer to section 7-100-30 for full descriptions of load

transfer. 5- See Section 7=100-10 above.

6- " Screws shall not be used to resist lateral forces by pullout resistance." Comments: Screws are only used in shear.

7- "Provision shall be made to pre-tensioning or other methods of installation of tension bracing to guard against loose diagonal

straps."

Comments: This project is design build. Our contractor does apply pre-tension on the strap. We will make sure of that during our inspection.

2220.2 Boundary Members and Anchorage.

"Boundary members and the uplift anchorage thereto shall have the strength to resist the forces determined by the load combination in section 2213.51"

UBC 2213.5. Column Strength:

"--- In addition , in seismic Zones 3 and 4, columns in frames shall have the strength to resist the axial loads resulting from the load combination in Items 1 and:"

1. Axial compression: 1. -Pdl + o.7 Pll + Aumiga Pe

Comments: This formula is used to check the Two- double studs back to back (four studs total at each end of the brace subjected to exception 1 below).

1. Axial tension: 1. Pdl +- Aumiga Pe

Comments: This formula is used to check the Two- double studs back to back( four studs total at each end of the brace subjected to exception 1 below).

"Exception:

The load combination as outlined in Item 1 and 2 above:

1. Need not exceed either the maximum force that can be transferred to the column, by elements of the structure, or the limit as determined by the overturning uplift which the foundation is capable of resisting."

7-100-15 Lateral Forces, Wind and Seismic:

Lateral forces are calculated according to the Uniform building Code or International Building Code based on the Jurisdiction where the building is located.

7-100-16 Vertical distributions:

Vertical distributions of lateral forces between floors is done according to the Uniform building Code or International Building Code based on the Jurisdiction where the building is located.

7-100-17 Horizontal distribution of lateral forces at each floor:

The distribution is done using the tributary width. Assuming the wood floor diaphragms is flexible.

7-100-18. Distribution of lateral force among braces on the same grid line, same vertical plane, on the same floor:

The distribution is done according to the stiffness of each brace. Since all braces are axial tension members and have the same cross section at each grid line, the stiffness is directly proportion to the brace cosine of the angle with the horizontal.

Hi= T cosine A, where

Hi is the Horizontal force to be resisted by brace number i. T is Tension on the brace

A is cosine of the brace angle with the horizontal.

So the total horizontal force at specific grid line is divided by the summations of the cosines of angles of all braces. Then multiplied by the cosine of the angle of the particular brace.

Hi= Ht x Cosine Ai / Sum ( Cosine Ai) Where i= 1 to n ( n is number of braces along the same grid line)

Ht is the total horizontal force along this gird line

Special case, pre-engineered

a- Hardy Panel

The stiffness of Hardy Panel is calculated as a cantilever. Them the distributions are done as above. 1- Hardy braced frame.

The distribution is done according the each member stiffness using RISA computer model 2- Paco Frame:

The distribution is done according the each member stiffness using RISA computer model

7-100-30 Force transfer between structural elements when using tension straps:

1. At roof level

Source of force From To Means of delivery Detail Number

Roof diaphragm to walls perpendicular to trusses

Roof diaphragm blocking Diaphragm screws to top of blocking

Blocking Wall top track Screws at the bottom of blocking per details

Roof diaphragm to trusses parallel to wall

Diaphragm Drag Truss top chord

Diaphragm screws shown on plan

Drag Truss bottom

chord

Wall top track Screw at truss bottom chord per details

Horizontal component of brace force

Wall top track Gusset plate Shear screws per brace schedule.

Vertical component of force

Gusset plate Wall studs Uplift screws per brace schedule.

Gusset plate Brace Brace screws per brace

schedule.

2- At second or third floor level:

Source of Force From To Means of delivery Detail

Number

Upper floor brace Brace Gusset plate Brace screws

Horizontal component of upper brace force

Gusset plate Upper wall bottom track Shear screws per brace schedule.

Upper wall track Wood floor sheathing. Bottom Track screws per brace schedule Note must use the capacity of the screw in the wood floor sheathing

Floor sheathing Lower wall top track Bottom Track screws per brace schedule.

Vertical component of upper brace force

Gusset plate Wall studs Uplift screws per brace schedule.

Top track of lower wall Gusset plate Shear screws per

brace schedule.

Gusset Plate Brace Brace screws per

brace schedule.

Horizontal component of lower brace force

Wall top track Gusset plate Shear screws per brace schedule.

Vertical component of lower brace force

Gusset plate Wall studs Uplift screws per brace schedule.

Additional forces from this floor diaphragm

Floor structural sheathing

Top track of lower wall Diaphragm screws per plan

Uplift forces upper wall studs lower wall studs One groups of upside up holdowns at the upper floor studs connected to a second group of upside down holdowns at the lower floor studs

3- Special case for discourteous brace on top of floor beam:

Horizontal component of the brace force

Gusset plate

Wall bottom track Shear screws per brace schedule.

Beam Floor diaphragm Bottom track screw to beam per brace

schedule.

Vertical component of the brace force Gusset plate

Beam Welding of gusset plat to beam per detail.

Beam Studs or post

below

Strap at each end of beam, per plan.

4- At foundation:

Source of Force From To Means of delivery Remarks/Detail Number

Brace Brace Gusset Plate Brace screws per

brace schedule.

Horizontal component of the brace force

Gusset Plate Wall bottom track Shear screws per brace schedule.

Wall bottom Track Foundation Anchor bolts per brace schedule.

Vertical component of the brace force

Gusset Plate Directly to Foundation Holdowns per foundation plan, typical

7-100 Source of information, Software, Details and Sample Projection

1 Related Section in the Engineering Manual

2 Pink Binder Light Gauge steel Binder has pre-designed braces and brace connections

3 Software RISA3-D CFS

4 Sample picture source

5 Hardcopy details 6 AutoCAD details 7 8 9 10 11 12

13 Sample Projects, Name and Number

1- KF204-266, 52 Unites

2- KF204-369, Athens 41 unites complex.

3- KF205-1004 Heathwood Acres/ residence, North Carolina.

4- KF205 – 1044 Darel Tedder Shop. 5-

14 References

15 Articles Binders, for licensed engineers only.

7-100-50 Shear wall systems:

a-When seismic control, only structural sheathing such as OSB or Plywood can be used. If wind control, gypsum boards could be used.

b- Structural Sheathings:

There is a very good concrete non-compatible sheathing produced by Fortacrete Structural Panels. Please use it whenever you can. It can resist both vertical loads as well as diaphragm shear forces. We have their web and brochure/ binder

7-100-80 Bracing with SureBoard

a- Must Design Boundary elements Per xxx. The manufacturer recommended configuration for the boundary elements are multiple studs face to face, boxed configuration.

b- Aspect ratio allowed by the manufacturer is 2 ¼:1 . IBC allowed to violate this aspect ration when you apply the reduction factor in IBC table.

c-Top chord connection. For the mixed light gauge steel walls and wood roof and floor, we have one 2x wood plate and the wall steel track. Must call out the connection on the Roof Framing Plan and Floor Framing Plan.

d- Shear values for sureboard panels can be found in the CEMCO binder.

7-100-80-50 Hold-downs:

a- Must provide hold down at end of wall.

b- Also, add hold downs at building corners any way, typical.

50- Connections:

b- Increase number of screws by 25 % to account for rotations that may arise because we assumed the diagonal joint to be pure hinge and it is not.

7-400 Buildings with Standing Seam roof such as storage facilities:

7-400-1 General

7-400-10 Top wall connection to roof:

a. Since Standing seam roof has diaphragm shear value of Zero, The wall must be supported by other means such as:

1-The bond beam at the top of the wall could provide horizontal support to the wall. The bond beam shall span between partition walls.

1. For long wall, Design a horizontal strap truss inside the roof the act as a beam to support the top of the wall. In this case, the bond beam has to span between the truss points. Angle at mid span to connect to the wall is used

2. At parapet provide ―cap channel‖ at roof elevation. Usually this is a Z on it’s side fastened the masonry wall using sleeve anchors or Kwik bolts at 1’- 6‖ to 2‖-0‖ O.C. and screwed to the supporting columns. The roof deck is then fastened to the cap channel.

3. At partition wall, provide 2-3/4 inch diameter expansive bolt to tie the masonry wall to the per perpendicular metal shear wall. Refer to detail 8/S4.2.

7-400-20 Z purlin design:

A- Since the standing seam does not have a shear capacity it does not provide lateral bracing for the purlin design. B- Provide strap cross bracing at half or one third points to provide lateral bracing. Refer to the AAA Secured storage pictures for an example. Also, refer to KF205-1158 Pear Tree self Storage.

Box headers:

1- Contractors prefer box headers because it is easier to build than back to back. Also, it does not require blocking. 2- Box beam or columns could be wider than the two flanges of the studs. By using bigger track, the two studs could be separated apart by 2 or 4 inches to form a stronger box.

3- Options for two box headers:

a-side by side at the same elevation: You can install two box headers side by side if you install the screws of the header to the studs on the second box header from the inside instead of from the out side. b-Side by side with one shifted higher above the other.

c-On top of each other.

 Connection:

Amount of Steel Required for light gauge/ cold-formed

steel homes

The attached documents include a material estimate for Model B and Model C of the Paulani Estates in Hawaii. These Estimates include:

 Trusses

 Exterior wall sheathing (outside only)

 Roof Sheathing

 Floor Joists (if applicable)

 Floor Sheathing (if applicable)

 Glulam beams

 Headers

Anything not listed above is not included in the estimate. Nabil Taha, Ph.D., P.E.

Executive Summary for Model C, (Second story) Total Steel used:

Length 470 ft of 16 gauge 428 ft of 18 gauge 4016 ft of 20 gauge Weight 664 lb of 16 gauge 484 lb of 18 gauge 3555 lb of 20 gauge Total: 4703 lbs

Steel per sq. ft of second story: 8.4 lb/ft2

Beams Still used:

5 1/8‖x 10 1/2‖ Glulam - 42 FT 3 1/8‖ x 10 1/2‖ Glulam- 28 FT 3 1/8‖ x 12 1/2‖ Glulam- 16 FT 5 1/8‖ x 16 1/2‖ Glulam- 8 FT 4 x 12 DF-L- 13 FT

Roof Sheathing Used:

1,135 ft2 of sheathing

Floor Sheathing Used:

600 ft2 of sheathing

Exterior Wall Sheathing (outside) Used:

873 ft2 of sheathing

Executive Summary for Model C, (First story)

Total Steel used:

Length

53 ft of 18 gauge 3876 ft of 20 gauge Weight 149 lb of 16 gauge 60 lb of 18 gauge 3431 lb of 20 gauge Total: 3640 lbs

Steel per sq. ft of first story: 3.12 lb/ft2

Roof Sheathing Used:

1256 ft2 of sheathing

Exterior Wall Sheathing (outside) Used:

1164 ft2 of sheathing

Executive Summary for Model C, (First and Second story) Total Steel used:

Length 575 ft of 16 gauge 481 ft of 18 gauge 7892 ft of 20 gauge Weight 813 lb of 16 gauge 544 lb of 18 gauge 6986 lb of 20 gauge Total: 8343 lbs

Steel per sq. ft of building footprint: 6.95 lb/ft2

Beams Still used:

5 1/8‖x 10 1/2‖ Glulam - 42 FT 3 1/8‖ x 10 1/2‖ Glulam- 28 FT 3 1/8‖ x 12 1/2‖ Glulam- 16 FT 5 1/8‖ x 16 1/2‖ Glulam- 8 FT 4 x 12 DF-L- 13 FT

Roof Sheathing Used:

2391 ft2 of sheathing

Floor Sheathing Used:

600 ft2 of sheathing

Exterior Wall Sheathing (outside) Used:

2037 ft2 of sheathing



References:

1. Prescriptive Method for Residential Cold-Formed Steel Framing, NAHB Research Center prepared for U.S. Department of Housing and Urban

Development, HUD, Co-sponsored by American Iron and Steel Institute, AISI and National Association of Home Builders.

2. Commentary on the Prescriptive Method for Residential Cold-Formed Steel Framing. 3. International Residential Code, IRC, for One and Two family dwellings.

4. Shear Resistance of walls with steel studs by American Iron and Steel Institute, AISI. 5. Steel Deck Institute Diaphragm Design Manual by the Steel deck Institute, SDI. 6. Cold-Formed Steel Design, AISI Manual, by American Iron and Steel Institute, AISI.

7. North American Specification for the Design of Cold-formed Steel Structural Members, AISA Standard, by American Iron and Steel

Institute, AISI.

8. Commentary on North American Specification for the Design of Cold- formed Steel Structural Members, AISI Standard, by American Iron

and Steel Institute, AISI.

9. Cold-Formed Steel Framing Design Guide, by American Iron and Steel Institute, AISI. 10. Cold-Formed Steel Connectors for Residential and Mid-Rise construction by Simpson. 11. Steel-Frame, House Construction by Tim Waite, NAHB Research Center.

12. Residential Steel Framing Handbook by Robert Scharff and the editors of Walls & Ceilings Magazine. 13. Steel Stud Brick Veneer Design Guide by American Iron and Steel Institute, AISI.

14. Floor vibration criterion for Cold-Formed C-shaped supported Residential Floor System. Prepared for U.S. Department of Housing and Urban Development, HUD.

15. Steel Framed Residential construction: Demonstration Homes, prepared for U.S. Department of Housing and Urban Development, HUD.

16. Innovative Residential floor construction: Horizontal Diaphragm Values for Cold-formed steel Framing, prepared for U.S. Department of

Housing and Urban Development, HUD.

17. Design Guide for Cold-formed Steel Trusses by American Iron and Steel Institute, AISI. 18. Light Gauge Steel Engineers Association, LGSEA magazine/Newsletter.

19. North American Standard for Cold-Formed steel Framing, Truss Design, American Iron and Steel Institute, AISI.

20. North American Standard for Cold-Formed Steel Framing, Header Design, American Iron and Steel Institute, AISI.

21. X-Standard for Cold-Formed Steel Framing, Lateral Design, American Iron and Steel Institute, AISI. 22. Cold Formed Steel Design by Wei-Wen Yu.

23. Jordan Commons, Cold-Framed Steel Training Manual, by American Iron and Steel Institute , AISI, Residential Steel construction Program.

24. Field Evaluation and Recommendations for Steel Framed Homes, Jordan commons Project, prepared for U.S. Department of Housing

and Urban Development, HUD.

25. Steel Framing, Erection Manual and Standard Details. 26. Vulcraft, Steel Roof and Floor deck.

27. Product Data, Dietrich Industries, Inc., www.dietrichindustries.com 28. SCAFCO Product Data.

29. Clark, Steel Framing system, www.clarksteel.com

30. Light Steel Framing Manual by Metal Framing .org, www.steelnetwork.com

1-For simple residential home, the prescriptive method could be used in the International Residential code, IRC. Section R603.1 General:

The provisions of this section shall control the construction of exterior steel wall framing and interior load-bearing steel framing for buildings not more than 60 feet long perpendicular to the joists or truss span, not more than 40 feet wide parallel to the joist or truss span, and not more than two stories in height. All exterior walls installed in

accordance with the provisions of this section shall be considered as load-bearing walls. Steel walls constructed in accordance with the provision of this section shall be limited to sites subjected to a maximum design wind speed of 110 miles per hour, Exposure A, B, or C and a maximum ground snow load of 70 psf.

2-For members in residential projects where the material presented in the IRC don’t give an answer and for commercial projects, the International Building Code, IBC must be used. The IBC reference the Cold-Formed Steel Design, AISI Manual, by American Iron and Steel Institute.

Light Gauge/ Cold-Formed Steel Standards:

 ASTM a653: grades 33, 27, 40 & 50( Class 1 and 3)

 ASTM A792: Grades 33, 37, 40, 50A.

 ASTM A875: grades 33, 27, 40 & 50

Universal Designation for Light gauge/ Cold-formed Steel:

The steel stud Manufacturers Association ( SSMA) has Published a catalog using a new designator system called "The right STUF".

The intent of the new designators is to make steel framing products easier to use and to accelerate their acceptance in new markets.

 S: Stud or joist section with flanges stiffeners/lips, C-shapes.

 T: track sections.

 U: cold-rolled channel or channel studs, without the stiffeners/lips.

 Standard shapes Light gauge/ Cold-formed Steel:

The C-shaped is used the most for the structural members such as studs, floor joists, roof rafters, roof trusses etc. The C-shaped section must have stiffeners/ lips with specified length/width to prevent local buckling. Please see the figure below

3. SECTION DESIGNATION AND PROPERTIES:

THE Right STUFF:

Universal Designator System for Light Gauge Steel Framing Members

The Right STUFF will identify any common light gauge steel framing member using: Web Depth (D), expressed in 1/100th inches.

Flange Width (B), expressed in 1/100th inches.

Minimum Base Metal Thickness (T), expressed in mils (1/1000th inches), and the following designators, S= Stud or Joist Sections with Flange Stiffeners (C-Shapes)

T = Track Sections

U = Cold-Rolled Channel or Channel Studs (w/o Flange Stiffeners)

EXAMPLES:

Designation for a 5-1/2"-16 gauge C-shape with 1-5/8" flanges and 1/2" stiffening lip = 550S162-54 54 Minimum bas metal thickness in mils (.054in = 54 mils) 162 1-5/8" flange in 1/100th inches S Stud or joist with flange stiffeners

550 5-1/2" member depth in 1/100th inches (outside to outside dimension)

Designation for a 3-1/2"-20 gauge Track with 1-1/4" flanges = 350T125-33

-33 Minimum bas metal thickness in mils (.033in = 33 mils) 125 1-1/4" flange in 1/100th inches

T Track section

350 3-1/2" member depth in 1/100th inches (inside to Inside dimension)

 Fasteners and connections for Light gauge/ cold formed steel.

4. FASTENERS AND CONNECTIONS

a. All fasteners shall be installed according to the manufacturer's approved product evaluation report [ICBOapproval].

b. Refer to fastener schedule and shearwall schedule per plan. c. Screws

1. All screws shall be a minimum size of #8 unless otherwise specified. All screws shall be corrosion resistant and shall be spaced such that the minimum center-to-center or edge distance of three screw diameters is maintained. Self in -drilling tapping screws shall conform to SAE-J78. A minimum of three exposed threads shall extend through the supporting steel member. Screws shall penetrate individual components of connections without causing

holes are not stripped. Head styles, threads, and point types for screws shall be selected based on application conditions and manufacturer recommendations.

2. Screw Diameter Size Guidelines Based on Total Thickness of Steel.

For SI: 1" = 25.4 mm.are in

1. Greater thickness' are possible, consult screw manufacturer.

2. Self-drilling trapping screws are required when total thickness of steel exceeds 0.033 inches. Sharp point screws are acceptable for steel thickness' of 033 inches (0.84 mm) or less.

c- Bolts shall meet or exceed the requirements of ASTM A307.

Bolts shall be installed with nuts and washers. Center to center spacing of bolt holes, connecting sheet metal material to concrete, shall be a minimum of three bolt diameters. Distance from the center of the bolt hole to the edge of the connecting member shall not be less than 1-1/2 bolt diameters. Bolt hole diameter shall not exceed the bolt diameter by more than 1/16 inch.

d. Using pneumatically driven pins to attach floor, roof, and walls. Structural sheathing are allowed, provided:

1. Pin diameter shall be 0.10 inch or more.

2. Pins shall penetrate the steel framing a minimum of 1/4 inch. 3. Minimum distance between pins and panel edges shall be 3/8 inch. 4. Use adhesive between sheathing and floor joists.

5. Submit manufacturers design values for approval to the engineer of record.

 Structural notes for Light gauge/ cold formed steel.

5. COLD FORMED STRUCTURAL FRAMING (LIGHT GAUGE STEEL):

1. GENERAL

a. The structural framing and its installation shall meet the following standards:

 American Iron and Steel Institute (AISI) "Cold Formed Steel Design Manual", latest edition.

2.American Society for Testing and Materials (ASTM) Standard C- 955 - Standard Specification for Load Bearing (Traverse and Axial) Steel Studs, Runners (Tracks), and Bracing or Bridging for Screw Application 0f Gypsum Board and Metal Plaster Bases.

 ASTM Standard C-1007-Standard Specification for Installation of

Load Bearing (Traverse and Axial) Steel Studs and Related Accessories. b. Manufacturer of Light Gauge Framing:

1. Company specializing in fabrication of structural framing components with five years minimum experience.

 Certified by the Light Gage Structural Institute, meeting current Inspection Guidelines.

c. Temporary bracing shall be provided until permanent bracing has been installed.

d. Punchouts, Cutting, Notching, and Hole Stiffening Flanges of joists, studs, headers, and other structural members shall not be cut or notched without an approved design. Web holes closer than 12 inches from center of hole to joist bearings, shall be reinforced with a solid steel plate, stud, joist, or track section of an equivalent thickness to the member it reinforces, provided that the following limitations are met:

exceed half the depth of the web, and

 The length of the hole (along the web) does not exceed

4 inches or the depth of the web, whichever is greater. Reinforcement shall extend at least 1 inch beyond all edges of the hole and shall be attached to the web with #8 screws (minimum) spaced no greater than 1 inch on center along the edges of the reinforcement.

 Unreinforced punchouts in webs of structural

members shall not exceed 1-1/2 inches wide x 4 inches long located along the centerline of the web at a minimum center to center spacing of 24 inches.

e. The framing members shall have ends squarely cut by shearing or sawing, be installed plumb, square, true to line and securely fastened per the contract documents or approved connection details.

f. Submit shop drawings and product data. Indicate on shop drawings component details, framed openings, anchorage, loading, type and location of fasteners and accessories or items required for other related work. 2. MATERIAL

a. The cold-formed structural framing and accessories shall be manufactured from structural quality steel having minimum yield strength of 33 KSI, for all design thickness' and have minimum protective coating equal to G-60 galvanized finish (ASTM A653M-95, Z180). The steel shall conform to one of the following ASTM Standards: ASTM A653.

b. Structural framing members shall conform to ASTM C955 and have engineering properties calculated in conformance with the AISI "Cold Formed Steel Design Manual", latest edition.

c. Load bearing steel framing members shall have a legible label, stamp, stencil, or embossment, at a minimum of 48 inches on center, with the following information as a minimum:

1. The manufacturer's identification. 2. The minimum uncoated steel thickness. 3, Minimum yield strength in kips per square inch. 4. "ST" for structural members.

5. Metallic coating weight (mass). 3. WALL FRAMING

a. Building paper and sealer, or equivalent, shall be provided between the underside of the tracks when fastened directly to concrete.

b. All load bearing studs shall be aligned with trusses, joists, and other horizontal or vertical load carrying members above or below the wall stud. Top and bottom wall tracks shall be of equal or greater thickness than that of the studs.

c. Studs shall have full bearing against inside track web (1/16 inches max. gap), prior to stud and track attachment. d. Load bearing steel studs shall be laterally braced. Refer to 1/S2 for construction details.

 Gypsum board or structural sheathing (i.e. APA or

plywood) fastened to wall studs in accordance with fastener schedule and shear wall schedule shown on plans. Sheathing shall cover the full-height of the wall from the bottom track to the top track. All edges and interior areas of the structural sheathing panels shall be fastened to a framing member and tracks. Provide blocking or strapping for unsupported panel edges.

 In addition to number 1, one of the following methods shall be used:

o Horizontal steel strapping installed at mid-height for 8- foot walls, and 1/3 points for 9 and 10-foot walls.

o Wall-stud bridging installed in a manner that provides resistance to both minor axis bending and rotation. Bridging rows shall be equally spaced at 4- foot on centers for axial loading.

e. Load bearing steel studs shall not be spliced without an approved design. Splicing of wall tracks only shall be conform with sheet S2.1. Wall tracks shall not be spliced within 3 inches of studs or anchor bolt locations. f. Corner

studs and the wall intersections shall be installed in accordance with sheet S2.1. g. Stud deflection due to wind load shall not exceed L/360

 Light gauge/ Cold-formed steel Fire Ratings:

Fire rating are expressed in terms of hours. Fire rating refer to the length of time it takes a fie to burn through a wall. A 1-hour fire rating can be achieved for both load bearing and nonbearing steel walls from 5/8 inch drywall on both sides of the stud wall with no insulation in the cavity.

The United States Gypsum company (USG) has tested fire and sound ratings for many different wall assemblies using USG products and ASTM standards. The results are published in USG’s Construction Selector ( United States Gypsum company, Chicago, IL,, publication No. SA100/3-99) Web: wwww.usg.com,

Benefits of Light Gauge/ Cold-formed Steel Framing

Design for Home Construction

In addition to the environmental benefits, light gauge/ Cold-formed steel offers other benefits that are appealing to every homeowner. For instance:

 Lower maintenance costs

 Decreased utility bills

 Higher resale value

 Fire resistance  Mold free  Pest/termite free  Durable  Weather resistant  100 % recyclable/ sustainable From these Comes these

Fabrication Walls, Floors, and Trusses from One Machine

Steel is North America’s #1 recycled material.

In short, light gauge steel/Cold formed steel outperforms wood from virtually every angle.

Building a light gauge steel framed house will be faster than using wood. That time efficiency will equate to savings in your wallet too.

Here are more benefits to using light gauge/cold formed steel framing: Providing a Competitive Edge:

The Many Advantages to light gauge/ cold formed steel framing give the builders of the contractor an edge over the competition such as:

 Consistent Material Costs: Light gauge/ cold-formed steel framing is constantly available which means little fluctuation in price. In fact, cold-formed steel often cost less than lumber.

 Consistence Quality: Light gauge/ cold formed steel enjoy uniform manufacturing tolerances. Cold-formed steel is always dimensionally correct and does not contain the knots, twists, or warps commonly found in wooden framing materials.

 Greater strength: Light gauge/ cold-formed steel components with same outside dimensions as

their wooden counterparts are lower in bulk and provide greater strength for many applications. The inherent strength of steel also usually translates into a need for fewer members and in many cases smaller members. For example steel strength for tension is about twenty times stronger than the most wood species.

 Design Flexibility:

A variety of products thickness, size and arrangement of light gauge/ cold-formed steel members enable engineers to meet big verity of owner demand for bigger and larger open space. Also, Light gauge/ cold formed steel can go higher than wood. Five and six stories high are common with light gauge/ cold formed steel framing.

o Ease of Installation:

Light gauge/ cold-formed steel framing installed quickly. The components of a lightweight, steel-framed assembly, including studs, track, joists, etc., can be assembled quickly and easily into prefabricate panels or assemblies.

Scenario A

Scenario B

Panelized wall made in the shop and shipped to site ready for installation.

Scenario C:

Modular construction. This is the fastest type of construction where the house is fabricated in the factory and shipped to site about 90% finished with fixtures.

 Time and Cost Saving:

260 Lin. Ft. Per Min.

Since construction financing is expensive, its time duration must be minimized. Light gauge/ cold formed steel construction takes less time to construct and so, save money to builders and homeowners.

One of the additional advantages of using Cold-steel framing is that a group of homes can be more cost –effectively framed in a controlled penalization area in a factory. Also, if time is of the essence, modular buildings and homes made from light gauge/ cold formed steel framing could be the best solution for your project.

 Ease of Modifications:

Since light gauge/ cold formed steel are strong, it could accept modification and alteration much easier than wood. Hiring a licensee engineer to design the modifications is always recommended.

 Superior Sound control:

The resilient nature of the light gauge/ cold formed steel studs helps walls absorb sound.

 User Friendly Technology:

Light gauge/ cold formed steel is a proven, user-friendly-technology that allows for a mouser transition form other materials.

 Multiple Finishes:

Light gauge/ cold for med steel framing accommodates all types of commonly used finishing materials. Variety of finishing materials, textures and shapes that can be selected is virtually unlimited.

 Availability:

Light gauge/ cold formed steel components are available throughout the country. They can be purchased in stock lengths, custom cut dimensions or in pre-engineered, panelized systems. Because of the growing use of light gauge steel in residential construction, local lumber yards and commercial building-supply warehouses are selling cold-formed steel components.

Foundation details for Light gauge/ cold-formed Steel.

First Floor detail drawings for Light gauge/ cold-formed Steel.

Second Story detail drawings for Light

gauge/cold-formed Steel

7-300 Light Gauge Steel Trusses:

1- General:

a- Contractors prefer that we use 3 ½ CS-sections instead of 5 ½ sections whenever possible. 1. For roof with Hip and Valley Roofs:

Options:

A-We prefer not to design the trusses. The client will hire one of the truss manufacturers with special software to design the trusses.

B-If item A did not work, one idea that the client will draw the truss profile for us in AutoCAD so we can export it to the software. Then, PSE will design the first last and one in the middle. Then we add to the drawings

that"contractor/Truss manufacturer to fabricate the trusses in between the shown trusses with same cross section and same connection but with geometry/ dimension shown on the roof plan/Roof framing plan."

C-If tem A and /or B above did not work, give very high separate fee for trusses design to entice the client to hire truss manufacturer. Or have enough of a fee to cover our time.

a- Refer to live and snow load in chapter two of the Engineering Manual. b- Must consider wind load.

c- Must consider snow load on one side only of the truss, unsymmetrical loading. d- Roof live load and snow load must be reduced for the roof slope.

e-If there is tile on the roof, additional load of the tiles must be added to the roof. Call the Architect or designer for the tile load since they vary based on the tile type.

6-Chords:

a- Top chord are usually continuous except at ridge. So, do not add moment release ( hinge except at ridge)

b- If the top chord of truss is unsafe, we could add additional C-section to the top chord only to make the top chord

double C-section back to back with small 3 ½ section rather than going to the 5 ½ section.

c- Bottom chord is usually continuous. If it is too long and it may be in two or more pieces, you must show splice detail.

7- Length of trusses:

a- Always write on the drawings "All dimensions shown are for Bidding purposes only. Contractor to verify all dimensions from the Architectural drawing and from field."

This is to avoid someone fabricating the trusses for the length you specified which turned to be few inches longer or shorter than it should be. One time, we had to pay for dimension error.

8- Girder Trusses:

a -All girder trusses shall be two ply face to face or three or four plies as needed. Show the two plies on plan. The table and details shall be the normal for single ply truss.

b- Include the detail that shows how the two trusses are connected face to face on your plan.

9- Attic Trusses:

a- Minimum size for all members of Attic trusses is 5 ½ inches. Gauge 18 is the minimum. b- Double the number of screws for all joints to help prevent distortion due to unsymmetrical loading. No other increase is applicable.

10-Step down trusses:

If the top chord of the stem down truss is unsafe, we could add additional C-section to the top chord only to make the top chord double C-section back to back with small 3 ½ section rather than going to the 5 ½ section.

20-Truuses for Mechanical units:

a- Some of the diagonal members may have to be shifted to accommodate the mechanical units. If shifting the diagonal did not work, may be we have to eliminate one diagonal.

b- After doing step a above, trusses will be designed to support the loads imposed on the trusses. Then on the roof framing plan, show them as double trusses back to back. In other words, you provide trusses to support double of the loads. This is due to

distortion of the trusses caused by the shifting/ elimination of some of the diagonal members to accommodate the mechanical

units.

Sample Apartment Complexes

52 Units

Athens Terrace 41 Units ,Three story 1200 South Broadway, Los Angeles, California

Green Housing

Steel Is Green

Steel is the #1 recycled material in North America. There is more steel recycled every year than aluminum, plastic and glass combined. Each year approximately 10 million vehicles are recycled (enough to circle the earth about 1 and 1/2 times). Each ton of recycled steel saves 1400 lbs. of coal and 2500 lbs. of iron ore (with 98% of mined ore used for making steel). And every year the recycling of steel saves the energy equivalent of electrically powering 1 out of 5 US households for one year.

Why Build With Light Gauge

Steel?

Steel is Fire Resistant

Steel is stronger. More than twenty times stronger than wood. Steel is straighter, stronger, safer.

Steel Avoids Mold:

Building demands in the last 20 years have lead to increased levels of sugar in lumber supplies, creating a diminished quality of wood that promotes an increase of mold problems in new homes. Hard to avoid moisture when you build on the open/ on-site. One-third to one-half of all structures have damp conditions that may encourage development of mold.

Source: U.S. EPA Eliminates outside air infiltration, leaks, drafts, and dust and quiet.

Lower Maintenance Costs

Steel has lower maintenance costs. Experience substantial savings over long term.

Less expensive because steel can save up to 60% on utility costs.. You will save $75,000.

For example:

 If you save $50/month, at 8% interest rate, how much do you think you

will accumulate in 30 years.

 Lower insurance costs due to upgraded safety factors.

 Lowered maintenance costs due to material’s durability and resilience.

 Higher resale values

 Steel is dimensionally stable, so it’s not affected by temperature, humidity and climatic changes. And not only because of steel’s strength, but its resiliency and construction techniques as well, light gauge steel, unlike stick framed homes, can be engineered to the highest seismic rating available for residential buildings.

“We have no choice

but to go green.”

Nabil Taha,

Steel Offers Peace of Mind.

Terminate termites (and other damaging pests) and fight fire with steel. Steel doesn't rot, is fire-resistant, air-tight and not chewable.

For decades steel has been the structure of choice for schools, hospitals, large apartment and commercial buildings. Relatively rare in single-family homes, steel’s superior quality, durability, strength and safety is now affordably available in your own neighborhood.

Faster and ease of

construction

Steel trusses are much stronger than wood and Steel houses resist wind and seismic forces.

How will your house look?

You can dress up your steel building with any material that you use with traditional wood stick framing such as:

 Any kind of siding Stucco/Plaster or any other material.

Commercial Light Gauge Steel

Remax office building Medford, Oregon

Precision Structural Engineering, Inc.

250-A Main Street, Klamath Falls, OR 97601 Telephone: (541) 850-6300

Fax: (541) 850-6233