Discussion: View Thread

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

Hi, Ron.
I would be most appreciative if you would run the attached figure by Cole Graveen and ask him if this is a reasonable application of loading of guardrails for residential occupancy.

Regards,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

The code being the design minimum, there is nothing to prevent the designer from applying a load that exceeds 50 plf or 200 lbf.  The issue arises when the architect has a specific look in mind for the railing.  Increased loads require reduced post spacing, thicker material, and substantial anchorage.  This adds to cost as well... the architect and owner have to be on board to accept the additional performance requirements.  In Massachusetts there is a code 780 CMR 1607.7 requirement for stadiums and grandstands that is 100 plf and 300 lbf.  I would cite this code for such an application regardless of jurisdiction.

Hi, Ron.
I would be most appreciative if you would run the attached figure by Cole Graveen and ask him if this is a reasonable application of loading of guardrails for residential occupancy.

Regards,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

I believe you missed my point. It appears to me that the 200 lbs concentrated force is quite excessive for residential occupancies. ASCE 7 excludes the 50 PLF force. IMO, the concentrated load should be reduced to 100 lbs or 200/1.6 = 125 lbs.

------------------------------
Bill Allen P.E., S.E., M.ASCE
Principal
Allen Designs
Mission Viejo CA

Original Message:
Sent: 05-17-2023 07:51 AM
From: Chad Morrison
Subject: Guardrail, Handrail Concentrated Load

The code being the design minimum, there is nothing to prevent the designer from applying a load that exceeds 50 plf or 200 lbf.  The issue arises when the architect has a specific look in mind for the railing.  Increased loads require reduced post spacing, thicker material, and substantial anchorage.  This adds to cost as well... the architect and owner have to be on board to accept the additional performance requirements.  In Massachusetts there is a code 780 CMR 1607.7 requirement for stadiums and grandstands that is 100 plf and 300 lbf.  I would cite this code for such an application regardless of jurisdiction.

------------------------------
Chad Morrison P.E., F.ASCE
Professional Engineer
Greenville RI

Original Message:
Sent: 05-12-2023 10:47 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Hi, Ron.
I would be most appreciative if you would run the attached figure by Cole Graveen and ask him if this is a reasonable application of loading of guardrails for residential occupancy.

Regards,

------------------------------
Bill Allen P.E., S.E., M.ASCE
Principal
Allen Designs
Mission Viejo CA

Original Message:
Sent: 05-10-2023 02:18 PM
From: Ronald Hamburger
Subject: Guardrail, Handrail Concentrated Load

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

#ASCE7-16
#LiveLoads

------------------------------
Bill Allen P.E., S.E., M.ASCE
Principal
Allen Designs
Mission Viejo CA
------------------------------

The loads in the chart appear to be uniform, given as lbf/ft.  Excessive to the point where the design becomes offensive to the architect or owner?  Often it is the base material or superstructure that is insufficient.  Deck/Rail collapses are common during parties.  I do not see a benefit for designing for less in the residential setting.  We accept many existing conditions in houses, but new construction should be robust.  When I questioned my nationally known insurance company about the issue, they directed me to the town building official.  Rules in a municipality vary greatly if they even have any.

------------------------------
Chad Morrison P.E., F.ASCE
Professional Engineer
Greenville RI

Original Message:
Sent: 05-17-2023 11:25 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

I believe you missed my point. It appears to me that the 200 lbs concentrated force is quite excessive for residential occupancies. ASCE 7 excludes the 50 PLF force. IMO, the concentrated load should be reduced to 100 lbs or 200/1.6 = 125 lbs.

------------------------------
Bill Allen P.E., S.E., M.ASCE
Principal
Allen Designs
Mission Viejo CA

Original Message:
Sent: 05-17-2023 07:51 AM
From: Chad Morrison
Subject: Guardrail, Handrail Concentrated Load

The code being the design minimum, there is nothing to prevent the designer from applying a load that exceeds 50 plf or 200 lbf.  The issue arises when the architect has a specific look in mind for the railing.  Increased loads require reduced post spacing, thicker material, and substantial anchorage.  This adds to cost as well... the architect and owner have to be on board to accept the additional performance requirements.  In Massachusetts there is a code 780 CMR 1607.7 requirement for stadiums and grandstands that is 100 plf and 300 lbf.  I would cite this code for such an application regardless of jurisdiction.

------------------------------
Chad Morrison P.E., F.ASCE
Professional Engineer
Greenville RI

Original Message:
Sent: 05-12-2023 10:47 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Hi, Ron.
I would be most appreciative if you would run the attached figure by Cole Graveen and ask him if this is a reasonable application of loading of guardrails for residential occupancy.

Regards,

------------------------------
Bill Allen P.E., S.E., M.ASCE
Principal
Allen Designs
Mission Viejo CA

Original Message:
Sent: 05-10-2023 02:18 PM
From: Ronald Hamburger
Subject: Guardrail, Handrail Concentrated Load

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

#ASCE7-16
#LiveLoads

------------------------------
Bill Allen P.E., S.E., M.ASCE
Principal
Allen Designs
Mission Viejo CA
------------------------------

The code being the design minimum, there is nothing to prevent the designer from applying a load that exceeds 50 plf or 200 lbf.  The issue arises when the architect has a specific look in mind for the railing.  Increased loads require reduced post spacing, thicker material, and substantial anchorage.  This adds to cost as well... the architect and owner have to be on board to accept the additional performance requirements.  In Massachusetts there is a code 780 CMR 1607.7 requirement for stadiums and grandstands that is 100 plf and 300 lbf.  I would cite this code for such an application regardless of jurisdiction.

Hi, Ron.
I would be most appreciative if you would run the attached figure by Cole Graveen and ask him if this is a reasonable application of loading of guardrails for residential occupancy.

Regards,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

Chad,

I see the 100/300 stadium loading in 780 CMR seventh edition (circa 2008) but I don't see it in the more recent editions.  As best I can tell, it was dropped by the eighth edition (2013).  It appears to me that the CMR currently agrees with ASCE/IBC loading of 50/200.  Do you know if the 100/300 is current? 

Many thanks,

Keith

The code being the design minimum, there is nothing to prevent the designer from applying a load that exceeds 50 plf or 200 lbf.  The issue arises when the architect has a specific look in mind for the railing.  Increased loads require reduced post spacing, thicker material, and substantial anchorage.  This adds to cost as well... the architect and owner have to be on board to accept the additional performance requirements.  In Massachusetts there is a code 780 CMR 1607.7 requirement for stadiums and grandstands that is 100 plf and 300 lbf.  I would cite this code for such an application regardless of jurisdiction.

Hi, Ron.
I would be most appreciative if you would run the attached figure by Cole Graveen and ask him if this is a reasonable application of loading of guardrails for residential occupancy.

Regards,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

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Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,

Hi, Ron.
I would be most appreciative if you would run the attached figure by Cole Graveen and ask him if this is a reasonable application of loading of guardrails for residential occupancy.

Regards,

Bill, Cole Graveen, chair of the ASCE 7 Live Loads task committee provides the following insights:

The ASCE 7-22 commentary states that the single concentrated load represents load from one person or object, or a small number of people, and the uniform load represents distributed loads such as from a group of people. A specific basis for the values of the concentrated and uniform loads, such as test data, engineering judgement, calculations, or a combination thereof, is not indicated.

A review of historical standards and codes indicates that design load values for guards have varied over the years, and prior to the International Building Code, varied between the various model building codes. The requirement for guards to resist a uniform load appears to pre-date the requirement to resist a concentrated load. For example, the 1945 edition of ANSI A58.1, the predecessor to ASCE 7, required stairway and balcony railings to resist a horizontal thrust of 50 pounds per linear foot, no concentrated load was specified.

While not specifically referenced in the ASCE 7-22 commentary, guardrail performance research was conducted in the 1970's under the direction of the U.S. Department of Commerce and the National Bureau of Standards. This research is described in three publications, NBSIR76-1131, NBSIR76-1132, and NBSIR76-1139, which can be found on the NIST publications website.

------------------------------
Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger

Original Message:
Sent: 05-10-2023 11:05 AM
From: Bill Allen
Subject: Guardrail, Handrail Concentrated Load

Background:
In ASCE 7-16, paragraph 4.5, a concentrated load of 200 lbs. applied in any direction is specified. Further, for anything other than one- and two-family dwellings, factory, industrial and storage occupancies, a 50 PLF is also specified, not concurrent with the 200 lbs. concentrated load. Obviously, this case will govern when the guardrail/handrail posts are spaced greater than 4 feet on center. This has been in the ASCE 7 as well as the IBC/UBC for a long time. In the past, rightly or wrongly, I, like many other engineers would apply a 1.33 factor to the resistance side of the equation back in the old days when we would apply this to transient loads such as wind or seismic. More recently, this load was clarified to be a live load with no increase in allowable resistance (although wind loads got a boost to 1.6 and seismic loads got a boost to 1.4).

For many years, too many to count, I've taken this load at face value. This load is particularly onerous especially when attaching to wood framing members. I'm quite aware of the need to design these railings for life safety. Here in California, we have Senate Bills 721 and 326 which are requiring apartment building owners and condominium HOAs to have their exterior elevated elements inspected. Most of the focus is on dry rot and corrosion. Little, if any, mention is made to the design practice back in the 70s and 80s.

Question:
What is the basis of this (200 lbs/50 PLF) criteria? Is it scientific or arbitrary?

Thank you,