SPECIFYING STOCK COMPONENTS for ARCHITECTURAL METAL WORK
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SPECIFYING STOCK COMPONENTS for ARCHITECTURAL METAL WORK
Architectural Metals, Railing Systems, and Engineering Information
This Online Learning Seminar is available through a professional courtesy provided by:
Julius Blum & Co., Inc. P.O. Box 816 Carlstadt, NJ 07072 Toll‐Free: 800‐526‐6293 Tel: 201‐438‐4600 (local NJ) Fax: 201‐438‐6003 Email: [email protected] Web: www.juliusblum.com
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©2013 Julius Blum & Co., Inc. The material contained in this course was researched, assembled, and produced by powered by Julius Blum & Co., Inc. and remains its property. Questions or concerns about the content of this course should be directed to the program instructor. This multimedia product is the copyright of AEC Daily.
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SPECIFYING STOCK COMPONENTS for ARCHITECTURAL METAL WORK
Presented by: Julius Blum & Co., Inc. P.O. Box 816. Carlstadt, NJ 07072.
Description: The course includes a discussion on: how to choose the best material for your job; available systems and their components; engineering data and the formulas to provide safe installations.
To ensure the accuracy of this program material, this course is valid only when listed on AEC Daily’s Online Learning Center. Please click here to verify the status of this course. If the course is not displayed on the above page, it is no longer offered.
The American Institute of Architects ∙ Course No. AEC659 ∙ This program qualifies for 1.0 LU/HSW Hour.
AEC Daily Corporation is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non‐AIA members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
This course is approved by other organizations. Please click here for details.
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How to Use This Online Learning Course
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Learning Objectives
At the end of this program, participants will be able to:
• Explain the reasons why stock components benefit high quality building projects and are cost effective.
• Detail how to choose a railing system and material to suit the needs of the project and surrounding.
• Discuss the importance of effective packing and handling measures for material shipping and storage as well as their ecological benefits.
• Discuss the reasons why metal suppliers should provide independent product testing and engineering information for their products.
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Table of Contents
An Overview of Architectural Metals, Alloys, and Finishing 6
Railing Systems and Components 19
Engineering Data: Elements of Sections, Railing Formulas, Problems and Solutions 52
In Summary 69
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An Overview of Architectural Metals, Alloys, and Finishing
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Trade Background and Information
For more than 100 years, architectural metal service centers have played an important role in stocking pre‐ engineered components used in the fabrication of handrails and other decorative elements of structures. Because of their established relationships with foundries and mills, these distributors can make sure that high quality parts are available from stock for immediate shipment. And, by providing data on the structural properties of this material, the architect is able to design in conformance with national and local code requirements.
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The Benefits of Purchasing Stock Components
There are numerous reasons why stock components are commonly used and/or specified by architects, contractors, fabricators, and building project teams.
• Large quantities available “off the shelf”. • Quality products meet quality control. • Products are designed and engineered to meet current codes. • Complete systems aid in ease of design and installation (by an experienced miscellaneous metal fabricator). • Installation drawings and details are supplied for all products . • Cost advantages to purchasing prefabricated and pre‐ engineered items .
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Packing and Handling
A high quality prepared surface is important for the best visual properties, architectural performance, and long‐term durability. For these reasons, it is important that the selected supplier takes the measures listed below. Customers should expect:
In the warehouse: • Suppliers should use paper leaving to protect metal surfaces. • Stacked bundles are wrapped and crated for general protection.
For transport: • Heavy tri‐wall bundle wrapping protects the individual bar stock . • Steel strapping eliminates the possibility of bending. • Paper wrapping protects the surface from scratches and deflection.
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Environmental Awareness
Metals: Recycled and Recyclable. The ever‐growing importance of protecting the environment and reducing waste extends to the metal industry as well. Architectural metals are largely composed of recycled material. Information on the recycled content of the material should be available for those that require LEED® certification.
Packing: Eco‐Conscious Packing. Using old newspapers as packing material, reusing storage boxes and bins, and recycling unused business forms into memo pads are examples of the small ways a business can continue to keep the environment in mind.
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Metal Alloys for Architectural Metal Work
A number of common metal alloys are described as architectural metal. Each offers unique performance properties and visual characteristics, and is suitable for specific applications. Some of the most common architectural metal alloys include:
• Aluminum: 6063‐T52, 6063‐T832, 6061‐T6.
• Stainless Steel: Alloy 304.
• Nickel‐Silver: Alloy C79800.
• Steel: Alloy C1010.
• Malleable Iron.
• Cast Iron.
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Metal Alloy Interactions
When specifying a metal type for a job, the specifier should be aware of any possible interactions a metal will have with another metal, between metals and cement/lime mortar, and between metals and the environment.
• Aluminum should be coated with either a mechanical or chemical coating and should not be left unfinished against cement/lime mortar.
• Bronze/nickel‐silver left untreated will develop a patina, e.g. the Statue of Liberty. The speed at which the metals will patina is dependent on both the bronze alloy and the environment.
• Stainless steel is not affected by contact with other metals or by the environment.
• Steel will corrode if not properly protected by paint or other coatings.
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Types of Metal Finishes
The finishes that are most commonly used on architectural metals can be classified into the following types:
• Mill Finishes: These are finishes applied by a basic rolling mill, the extrusion press, or a casting mold.
• Mechanical Finishes: These finishes are applied by the fabricator, and are the result of physically affecting the surface of the metal by some mechanical means.
• Chemical Finishes: These finishes (usually a pre‐finish) are applied by the fabricator, and they may or may not have a physical effect upon the surface of the metal.
• Coatings: These finishes are either formed by the metal itself by a chemical or electrical conversion process, or formed by application of added material applied by the fabricator or specialist.
NAAMM/NOMMA 500‐06, Metal Finishes Manual for Architectural and Metal Products is an excellent reference for metal finishes and can be found here: http://www.naamm.org/amp/amp_technical_literature.aspx Accessed May 2013.
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Types of Metal Finishes
The following table references the previous two slides and further matches metals with their finishing options.
Carbon Steel Finish Aluminum Copper Alloys Stainless Steel and Iron Mill (as supplied) X X X X Mechanical X X X ‐ Chemical X X ‐‐ Coatings X X X X
Source: NAAMM/NOMMA 500‐06, Metal Finishes Manual for Architectural and Metal Products, p.V. http://www.naamm.org/amp/amp_technical_literature.aspx Accessed May 2013.
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Selecting the Best Material for Your Job
When designing and selecting material for your project, there are a few criteria to consider:
1. Job location: As metals interact with the environment, the location (e.g. coastal, indoors, outdoors) of the job is important in determining the type of metal specified.
2. Fabricator expertise: Every job, with the exception of a non‐weld system (slide 26), requires an experienced miscellaneous metal fabricator. It is important to check with them first to make sure they have worked with/can handle the material you have specified.
3. Cost: The relative price of specific metals may be one of the determining factors in choosing the metal for a specific application. Metal prices are constantly fluctuating, and prices are determined by market values.
4. The look: Regardless of the information above, the architect or owner may wish to pick the metal based on color to suit the look and feel of the job.
*Always make sure there is an experienced metal fabricator on the job. Your material supplier can suggest the names of fabricators to ensure quality of work.
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Architectural Metals and Alloys
The photos below illustrate two stainless steel jobs, completed by an experienced metal fabricator. It is always important to make sure the fabricator designated to the job is capable of producing the desired product.
Dylan’s Candy Store, New York, NY. Office Building, Scarsdale, NY. Stainless Steel: Alloy 304. Stainless Steel: Alloy 304.
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Architectural Metals and Alloys
The photos below illustrate two jobs, aluminum and a nickel‐silver, completed by an experienced metal fabricator. It is always important to make sure the fabricator designated to the job is capable of producing the desired product.
Library, Phoenix, AZ. Hospital, Huntsville, AL. Aluminum: Alloy 6063‐T52 & Alloy 6061‐T6. Nickel‐Silver: Alloy C79800.
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Architectural Metals and Alloys
The photo, lower left, illustrates a bronze job completed by an experienced metal fabricator. The photo, lower right, is an example of a high quality (note the detail in the casting) malleable iron component. It is always important to make sure the fabricator designated to the job is capable of producing the desired product.
Office Building. Malleable Iron Component. Bronze: Alloy 385.
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Railing Systems and Components
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Glass Railing System and Components
Glass railing is a system comprised of metal railing components for use with ½" or ¾" tempered glass panels as structural balusters.
A readily available system complete with the shoe mouldings, a variety of top rails/mouldings (in different metals) and components has been designed for use with glass.
**It is always important to make sure the system has been load tested by an independent contractor and that a test report can be supplied.
Glass rail installations, as well as many other railing applications, require that a guardrail have a handrail included as well. Most building codes differentiate between handrail and guardrail. Handrails are generally defined as being used for guidance and support, while the purpose of guardrails is to resist accidental falls.
*It is always important to check with your local codes authorities.
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Glass Railing System and Components
Readily available with stock components for glass railing:
Glass Mounting: Resilient setting blocks support and Handrail Assembly: Vinyl insert protects the top edge cushion glass panels as they are inserted in the shoe. of the glass panel and fits closely inside the handrail Space is allowed for plumbing and setting of glass. moulding. The specifier selects the sealant.
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Glass Railing System and Components
Readily available with stock components for glass railing:
Handrails and Tubing: Top mouldings are available in Corner Bends, Miter Corners, End Caps: End caps are several shapes and sizes, and are suitable for finishing available, and different styles of elbows can be and polishing. Mechanical connections may be attached to the handrail and used as wall connectors. preferred to avoid reductions in allowable design stresses that are caused by welding joints.
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Glass Railing System and Components
The photos below illustrate two stainless steel jobs, completed by an experienced metal fabricator. It is always important to make sure the fabricator designated to the job is capable of producing the desired product.
Chronicle Books, San Francisco, CA. American Girl, Natick, MA. Stainless Steel: Alloy 304. Stainless Steel: Alloy 304.
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Glass Railing System and Components
The photos below illustrate two stainless steel jobs, completed by an experienced metal fabricator. It is always important to make sure the fabricator designated to the job is capable of producing the desired product.
Boston World Trade Center, Boston, MA. Corporate Headquarters, Scottsdale, AZ. Stainless Steel: Alloy 304. Stainless Steel: Alloy 304 .
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Pipe Railing System (fabricated without welding)
There are a variety of pipe railing systems available. One type of pipe railing system is easy to assemble and can be fabricated quickly, often on‐site, without welding. Components slip together and are joined by concealed mechanical fasteners at intersections and by epoxy structural adhesive at splice joints. Pipe and fittings may be provided in a variety of metals. Mechanical connections avoid the reduced allowable design stress effect that welding would have on the material.
*It is always important to make sure that the material installed meets local and national safety standards and guidelines when installed in accordance with data and Office Building, Scarsdale, NY. instructions provided by the supplier. Stainless Steel: Alloy 304.
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Pipe Railing System (fabricated without welding)
Continuous Posts and Rails: Posts and top rails run in continuous lengths, providing a system that is inherently stronger than one with cast tee and cross connections.
Mechanical Connections: Structural adhesive, stainless steel machine screws with lock washers, and threaded tubular rivets provide positive connections at joints.
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Pipe Railing System (fabricated without welding)
Mounting Options: Posts may be embedded in floor slab with a cover flange, surface mounted with a heavy‐duty floor flange, or side mounted on fascia or stringer by means of a fascia flange. A reinforcing insert is used at the base of the post for added strength and stiffness.
Range of Fittings: A suitable fitting is available for practically any stair or ramp railing condition. Adjustable handrail brackets and ramp rail tees are recommended for unusual ramp or stair angles.
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Pipe Railing System (fabricated without welding)
A non‐weld pipe railing system can be an effective, durable rail type for commercial and institutional buildings. It can be assembled quickly, on‐site, and is relatively cost effective.
ASCAP Building Entrance, Nashville, TN.
Commercial Building Entrance, Wilmington, DE. United Center for Cerebral Palsy, Islip, NY.
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Pipe Railing System
Sun Valley Music Pavilion, Sun Valley, ID.
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Post and Panel System (no welding required)
Other non‐weld railing systems are also available that do not have circular shapes. One of them is often called a post and panel system.
A complete selection of fittings is available for this type of system. Self‐aligning wall, post, and mounting brackets are usually recommended for unusual ramp or stair angles. Handrails may be mounted using flat bars and channels, joined with non‐welded corner bends, or closed with end caps. A wide range of cover flanges, fascia flanges, reinforcing bars, and post caps are also available.
Business School, Jackson State University, Jackson, MS.
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Post and Panel System (no welding required)
A full range of components are available in aluminum, bronze, nickel‐silver, and stainless steel to meet virtually any installation requirement. Posts and handrails may be combined with a variety of post, wall, and fascia brackets to achieve a wide range of design alternatives, while meeting code and other regulatory requirements.
• Handrails. • Precut Posts. • Extensions. • Brackets. • Flanges. • Plugs. • Caps.
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Weld‐Free Post and Panel Railing System
Handrails and Tubing: Top mouldings are available in Full Range of Fittings: A complete selection of fittings are several shapes and sizes. Check with the supplier. available. Self‐aligning brackets are recommended for unusual ramp or stair angles. A wide range of cover flanges, fascia flanges, reinforcing bars, and post caps are also available.
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Weld‐Free Post and Panel Railing System
The photos below illustrate completed jobs utilizing the weld‐free post and panel system.
Library, Phoenix, AZ. High School, Wilder, KY.
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Weld‐Free Post and Panel Railing System
The photos below illustrate completed jobs utilizing the weld‐free post and panel system.
Indiana Wesleyan University, Greenwood, IN. High School, Leander, TX.
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Traditional Railing Components
Traditional systems can be ornate or simple. Major profiles are commonly extruded or drawn, while fittings are machined or cast. It requires a high level of fabrication expertise to join a casting to an extrusion and not show any joint seams.
Handrail mouldings and components are carried in stock in a variety of metals. Railing components include posts and spindles, volutes, lateral scrolls, lamb’s tongues, post caps, collars and finials. The system is designed to mix and match fittings and mouldings. While the handrail must meet local codes and engineering regulations, architects and fabricators have many options in the design.
The following slides showcase stock components in traditional shapes and profiles, which help make intricate, classical metalwork the most cost effective option.
Private Residence.
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Traditional Railing Components
Handrail Mouldings
Muttontown Golf & Country Club, Golf & Country Club, Newport Beach, CA. East Norwich, NY.
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Traditional Railing Components
Handrail Fittings
Beverly Hills Montage Hotel Golf & Country Club, Newport Beach, CA. Pennsylvania Judicial Center, Harrisburg, PA. Beverly Hills, CA.
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Traditional Railing Components
Post Caps, Collars, Finials, Balusters, Bases, Flanges, Post and Spindle Fittings
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Traditional Railing Components
Starting Posts.
Ornamental Valences. Spindles.
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Traditional Railing Components
Beverly Hills Montage Hotel Pool and Spa, Beverly Hills, CA.
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Traditional Railing Components
Private Residence. Private Residence.
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Treillage and Ornamental Railing Panels
Malleable iron railing panels are used to provide architectural details on both stairs and straight runs. Panels should be designed to meet current code requirements.
Treillage panels are double faced and superbly detailed. Because they are malleable iron, they may be welded and bent cold and will not break or shatter in the course of normal handling.
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Treillage and Ornamental Railing Panels
Ornamental collars are a cost effective way of providing details to a stair, fence, or gate. A wide variety of design options are possible using a combination of ornamental collars.
Aluminum castings are recommended where it is important to keep weight at a minimum, as in gates or removable screens. Otherwise, malleable iron castings are preferred for their strength and resistance to breakage.
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Treillage and Ornamental Railing Panels
Ornamental Railing Panels. Treillage and Ornamental Railing Panels.
Ornamental Collars. Ornaments.
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Treillage and Ornamental Railing Panels
Private Residence. Private Residence.
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Handrail Brackets
Handrail brackets are used in many rail applications. They are designed for use as wall brackets, post brackets, center rail, and vertical mounting brackets.
Handrail brackets are designed to meet or exceed accepted safety standards and have been laboratory tested. Test reports should be available upon request from your supplier.
Center Post Bracket: Stainless Steel.
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Self‐Aligning Wall Brackets
Wall Brackets:These are available in a variety of finishes and also self‐ align to any slope when wall mounted. Once the concealed wall attachment is made, the bracket yoke which attaches to the handrail rotates freely until the chosen handrail is properly aligned. Various styles are available to coordinate with different handrail styles and with pipe railings.
Post Brackets:These are available in a selection of metals and self‐align to any slope when post mounted. They are adaptable for drywall when the post screw is replaced with a lag screw and used with proper backup.
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Handrail Brackets
Cast/Stamped/Extruded Brackets: These brackets have a more traditional style and are used in a multitude of applications. The various styles allow for concealed fastening or attachment with a single mounting bolt through the wall flange center. Specify this bracket for an attractive and durable finish.
Vertical Mounting Brackets:The mounting brackets are useful for mounting handrails vertically as in an elevator cab or hospital corridor. These brackets are also used with wood handrails. They are suitable for mounting handrails on top of a parapet or knee wall. Adapters are available to permit attachment to pipe or round tube.
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Tubing, Bars, Shapes and Elevator Cab Components
A large selection of tubing, bars, and shapes are sold in aluminum, bronze, stainless steel, nickel‐silver and steel. The stock sizes of tubing bars and shapes are selected to especially meet the requirements for ornamental and miscellaneous metal work. Material is sold mill finish and is suitable for polishing.
Shapes are extruded to high tolerances and have the sharp corners required for architectural work. Angles and tees are used frequently in dropped ceilings and are also used in areas of elevator cabs. It is important that all extrusions are handled with great care to assure that the product is well suited for architectural finishing.
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Elevator Cab Components
An entire group of components are available for use in the assembly of elevator cabs. These include, but are not limited to, door thresholds and saddles, single and double speed sills, mouldings, handrail brackets for vertical use, and tubing bars and shapes. These items are typically available in aluminum, bronze, nickel‐silver, and stainless steel in a variety of sizes for many elevator applications.
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Elevator Cab Components
Tubing Bars and Shapes. Elevator and Door Saddles.
Elevator Cab Handrails and Brackets. Thresholds and Door Saddles.
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Engineering Data: Elements of Sections, Railing Formulas, Problems and Solutions
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Engineering Data
Availability of complete structural information enables architects and designers to make proper use of a manufacturer’s component systems to provide safe, durable, handrail installations. The designer can engineer installations to conform to specific building code loading criteria or can establish design requirements for a given installation on the basis of anticipated traffic exposure and types of use. The following slides illustrate the types of pertinent engineering data and information necessary for installation of safe railings. This information should all be available in hard copy through the manufacturer.
The five major considerations for the structural designs of handrails are:
1. Structural loading criteria as established by governing building codes or special design requirements.
2. Properties of railing materials and allowable stresses for design.
3. Elements of sections for railing components.
4. Load, stress, and deflection relationships expressed as formulas for engineering design.
5. Proper attachment and sound supporting structure.
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Structural Requirements
Structural requirements for railings are usually expressed in one of two ways, depending on governing codes and regulations. Some of these specify an applied loading distributed uniformly along the rail while others specify loading concentrated on the top rail. The designer should consult the governing codes, local ordinance, project specifications, and regulatory authorities to determine specific structural requirements for compliance.
An excellent source of design load requirements can be found in ASCE/ANSI 7 Minimum Design Loads for Buildings and Other Structures, published by the American Society of Civil Engineers.
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Allowable Stresses
To provide adequate safety factors, the engineering profession assigns to each material an allowable design stress which is usually expressed as a specific fraction of minimum yield, or as a smaller fraction of minimum ultimate strength. Allowable stresses vary with the composition and temper of the material and also, to some degree, with the kind of shape and the direction of stress.
Typical Yield strength is the point of stress (in pounds per Ultimate square inch) at which material fails to return to its Minimum Ultimate original position after the stress has been removed, Typical and takes a permanent set. Minimum yield is defined Yield as the test value exceeded by 99% of a large number Minimum Yield of specimens. For non‐ferrous metals, the yield point is arbitrarily defined as the point of stress at which Allowable Stress permanent set is a specific fraction of 1% of the length of the test piece (0.2% offset as shown to the right or 0.5% elongation). Ultimate strength is considerably STRESS (lbs./sq.in.) higher (see graph). 0.2% of STRAIN (inches/inch) GAUGE LENGTH
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Loading Diagram and Symbols
Familiarity with these standard w* = Uniform horizontal loading, perpendicular to the rail (lb/ft). symbols and design variables will L = Span between centerlines of posts or brackets (in.). enable architects, fabricators, and P = Horizontal force, perpendicular to rail applied at top of post (lb). contractors to better specify and FH = Horizontal force, perpendicular to rail at any point along the railing (lb). install safe, durable railings. FV = Vertical force, perpendicular to rail at any point between posts (lb). h = Height of post. Distance from point of load application above top of attachment (in.).
h1 = Distance from top of post attachment to top of reinforcing insert (in.). M = Bending moment (in.‐lb). f = Unit stress (psi).
fs = Allowable fiber stress for design (psi). 3 Sx & Sy = Section modulus about the x‐ or y‐axis respectively (in ). 4 lx & ly = Moment of inertia about the x‐ or y‐axis respectively (in ). k = Stiffness of member. K = Bending moment constant. c = Distance from the neutral axis to the extreme fiber of any section (in.). E = Modulus of elasticity (psi × 106). Δ = Deflection (in.). R = Stiffness ratio.
Pf = Load proportion factor.
Fr = Reaction factor (psi). * Values for w (uniform load in lb/ft) converted to lb/in by dividing by 12
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Key Terms
Section Modulus ‐ a geometric property for a given cross‐section used in the design of beams or flexural members.
Allowable Design Stress ‐ a design philosophy civil engineers use to ensure the stresses developed in a structure due to service loads do not exceed the elastic limit.
Applied Bending Moment ‐ exists in a structural element when a moment (the perpendicular distance from a point to a line or a surface) is applied to the element so that the element bends.
Moment of Inertia ‐ a measure of an object’s resistance to changes to its rotation.
Moduli of Elasticity ‐ the mathematical description of an object or material’s tendency to be deformed elastically when a force is applied to it.
Maximum Allowable Deflection ‐ the maximum permissible deflection value where no reinforcement is necessary.
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Bending Moments and Stresses
Determination of bending moments and stress in structural railing members follows conventional engineering design procedures. The resisting moment—calculated from the Section Modulus (S, which equals I/c) and
Allowable Design Stress (fs)—must equal the Applied Bending Moment (M).
This translates into railing formulas as described on the next two slides.
Please remember the exam password FORMULAS. You will be required to enter it in order to proceed with the online examination.
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Bending Moments and Stresses: Rails
Connections between posts and rails are assumed to be free to pivot, although in practice the rail post connection is normally not a pivot. Distribution of loads through multiple spans decreases maximum bending moment in horizontal members. The effect of different numbers of spans may be taken into account by varying the Bending Moment Constant (K). Calculation of Unit Stress (f) and Length of Span (L) are accomplished by using the following formulas:
1. For uniform vertical or horizontal loads (w): 2. For concentrated loads (F) applied at mid‐span:
Note: Values of K are defined based on the maximum bending moment developed under various numbers of spans.
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Bending Moments and Stresses: Posts
Posts act as vertical cantilever beams in resisting horizontal thrust applied at the top rail. Bending moment produced by horizontal thrust normally controls design, and post spacing may be calculated using the following equations.
1. For uniform horizontal loading (w):
2. For concentrated horizontal loading (Fh): When concentrated loading is specified, the horizontal load on the top rail is distributed among several posts adjacent to the point of loading. The load distribution is a function of the relative stiffness of post and
top rail and of the number of spans in the railing. This calculation will show what proportion (Pf) of the total load any one post may have to sustain. To the extent that it is less than 100%, it will justify the use of lighter and more economical construction. The following equations applies:
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Internally Reinforced Posts
P The load‐carrying capacity of a post with reinforcing insert is limited by the allowable fiber stress at one of three points.
1. The post at the top of the insert, above which it is not reinforced. h 2. The insert at its base, at the highest point of its attachment to the
Floor 1 supporting structure. h
3. The post at the same point of attachment.
The lowest of these three loading limits controls design for the Point of Insert combined post and reinforcing insert. Attachment
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Internally Reinforced Posts
1. Post at top of insert:
Moment in post (top of insert) : Fiber stress in post (top of insert): Loading limit:
At the point of contact between the railing post and the reinforcing insert, the deflection of each is assumed to be the same, but the resisting force of each is a function of its Moment of Inertia (I) and
Modulus of Elasticity (E). The resultant combined Reaction Factor (Fr) at the top of the insert is determined as follows:
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Internally Reinforced Posts
The loading limits for points 2 and 3 are then determined as follows:
2. Insert at base:
Moment in insert: Fiber stress in insert: Loading limit:
3. Post at base:
Moment in post: Fiber stress in post: Loading limit:
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Combined Handrail Sections
When two sections of the same metal are combined by being fastened together to form a handrail (e.g. a steel moulding mounted on a steel channel), the sections develop the same deflection under load but act independently about their respective neutral axes.
Steel handrail with steel channel.
Ia and lb are the moments of inertia of the two sections. Since the Section Modulus (S) equals I/c, the combined value for S of the two sections would be:
In the railing formulas, substitute the above equation for the value of S whenever combined sections of the same material are used.
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Combined Sections of Dissimilar Materials
To compute the loading of combined sections of dissimilar materials (e.g. a bronze handrail mounted on a steel channel) calculations involve the determination of the relative portion of the load carried by each section. The load distribution is a function of the relative stiffness of the two sections, which is determined by the Moments of Inertia (I) and their Moduli of Elasticity (E). The distribution of the total load between two sections is determined as follows:
1. Load carried by A: y
xa A c xa
xb B c
xb 2. Load carried by B: y
B Total Load Total Load Carried by A
Individual calculation to determine the fiber stress for each material, using the load portion of each section, will then determine which section controls design: namely, the section giving the lesser result.
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Deflection Considerations
Excessive deflection of a railing under load, even though it meets strength requirements, will give the user a feeling of insecurity and may cause tripping or stumbling. Lateral deflection of posts or vertical deflection of horizontal rails under load are computed as follows—these formulas must be used with caution:
1. For posts without reinforcing insert:
2. For posts with reinforcing insert of similar or dissimilar material:
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Deflection Considerations
3. For rails (concentrated load, F):
4. For rails (uniform load, w):
There are few, if any, regulations or code requirements limiting deflection in a railing, but ASTM has put forth the following criteria regarding Maximum Allowable Deflection (Δmax) in their specification E985.
For horizontal load at For horizontal load at top For vertical load at mid‐span: of post: mid‐span:
In many instances, the anchorage of the railing to the floor, tread or fascia is subject to a degree of rotation which will add an indeterminate amount to the deflection on the post and rail. Anchorage and supporting structure must be as secure and rigid as possible.
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Sample Problem and Solution
Determine required section modulus of post requirements: • Concentrated load, F = 200 lbs. • Railing height, h = 42 in.
Material specified: • Post: Steel tubing
• Allowable stress, fs = 16,800 psi
Determine: • Section modulus, S, and select a suitable section
• Resisting bending moment, M(resisting) = fs × S
• Applied bending moment, M(applied) = F × h
• M(resisting) must equal M(applied)
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In Summary
The stock component architectural metal supplier should be able to provide material properties, elements, structural loading criteria, and other engineering design information for all of their products. This information should be sufficient for the engineering and fabrication team to show compliance with governing building codes or special design requirements.
As reiterated throughout the course: It is always the responsibility of the designer/architect to acquaint themselves and comply with the various codes and regulations that govern each product. The supplier should be able to provide test results, engineering data, and installation instructions for their material.
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Conclusion
If you desire AIA/CES, state licensing or CE credits for another organization, please click on the button to commence your online examination. A score of 80% or better will allow you to print your Certificate of Completion; you may also go to your AEC Daily Transcript to see your completed courses and certificates. ©2013 Julius Blum & Co., Inc. The material contained in this course was researched, For additional knowledge and post‐seminar assembled, and produced by Julius Blum & Co., Inc. and remains its property. assistance, click on the Ask an Expert link above. Questions or concerns about the content of this course should be directed to the program instructor. This multimedia product is the copyright of AEC Daily.
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