www.thecableconnection.com

PEDESTRIAN CABLE RAILINGS

Guardrails with Cable In-Fill

Course Number: ult05a An AIA Continuing Education Program Credit for this course is 1 AIA HSW CE Hour Please note: you will need to complete the conclusion quiz online at RonBlank.com to receive credit

© Ron Blank & Associates, Inc. 2009

The Cable Connection Inc. 52 Heppner Drive Carson City, NV 89706 [email protected] Pedestrian Cable Railings 800-851-2961 Dan Nourse, Mgr., Sales & Cust. Serv. [email protected]

An American Institute of Architects (AIA) Continuing Education Program Approved Promotional Statement:

Ron Blank & Associates, Inc. is a registered provider with The American Institute of Architects Continuing Education System. Credit earned upon completion of this program will be reported to CES Records for AIA members. Certificates of Completion are available for all course participants upon completion of the course conclusion quiz with +80%. Please view the following slide for more information on Certificates of Completion through RBA This program is registered with the 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 or Ron Blank & Associates, Inc. of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

An American Institute of Architects (AIA) Continuing Education Program Course Format: This is a structured, web-based, self study course with a final exam. Course Credit: 1 AIA Health Safety & Welfare (HSW) CE Hour Completion Certificate: A confirmation is sent to you by email and you can print one upon successful completion of a course or from your RonBlank.com transcript. If you have any difficulties printing or receiving your Certificate please send requests to [email protected]

Design professionals, please remember to print your certificate of completion after successfully completing a course conclusion quiz. Email confirmations will be sent to the email address you have provided in your RonBlank.com account.

Please note: you will need to complete the conclusion quiz online at RonBlank.com to receive credit

Course Description Discuss the unique design requirements for a railing using cable as a railing in-fill. Review the different types of cable construction methods, and explain the proper mounting and tension requirements when installing a pedestrian cable railing.

Course Objectives Upon completion of this course the designer will be able to: • Describe the unique design requirements for a railing using cable (also called wire rope or aircraft cable) as a railing in-fill. • List the different types of cable. • Explain the characteristics of different cable constructions. • Explain the construction and maintenance of a cable guardrail system.

Introduction • Most building codes require that a 4" sphere shall not pass through a guardrail at any point. This requirement has presented architects with the challenge of designing railings that can still be attractive despite the 4" rule and, where important, not obstruct the view looking through the railing. • Several in-fill alternatives are available, including glass, mesh, and cable, also known as wire rope or aircraft cable.

Introduction • RAILING DESIGN CODE NOTE • The US had several codes being used across the country that included the Uniform Building Code (UBC), the Standard Building Code (SBC), and BOCA. These codes were combined into the International Building Code (IBC) in the year 2000 and issued as a single code to be used nationally. The 2000 edition of the IBC for residential construction, known as the International Residential Code (IRC), contains a sentence in Section R316.2 that reads: Required guards shall not be constructed with horizontal rails or other ornamental patters that results in a ladder effect. This appears in no other IBC code edition. • Please note that in all subsequent editions of the IBC (2001-2003), Commercial and Residential, this sentence has been removed. Horizontal railings are allowed by the code. Check with the local code authority.

Strand vs. Cable • There is a difference between Strand and Cable, although Strand is often referred to as Cable. • Strand is two or more wires wound concentrically in a helix. They may or may not be wound around a center wire. Strand is normally referred to by the number of wires in the strand preceded by a 1. For example, 1x7 is one group of seven wires. 1x19 is one group of 19 wires.

19 individual strands make up this cable

Strand vs. Cable • Cable refers to constructions of wire rope that include multiple groups of strands. For example seven groups of 1x7 strand would be a cable referred to as 7x7. 7x19 would be seven groups of 1x19 strand. Cable is also referred to as Wire Rope. • For the purposes of this course, we will use the term Cable to apply to Strand and Cable, because both are commonly referred to as Cable in lay terms.

1 X 19 Strand

7 X 7 Cable

7 X 7 Cable

Why Cable? • Cable is a good choice where the architect wants to minimize the obstruction of the view through the railing or where a high tech look is desired. • It is virtually maintenance free, is very strong in tensile strength and quite suitable for railings. A cable diameter of as little as 3/16" is satisfactory for most pedestrian railings. Because the 3/16" diameter of the cable is relatively small, the view through the railing is virtually unobstructed. In applications where a high tech look is desired, cable railings are often a preferred choice.

Why Cable? Typical guardrail applications include office buildings, shopping centers, sports complexes, auditoriums, warehouse conversions, residential interiors, mezzanines, decks, and viewing platforms.

Applications Cable

Applications Cable

Cable Material Generally, cable railings use type 316 stainless steel cable. Type 316 stainless steel cable is bright, shiny and will not rust in most outdoor applications. Galvanized steel cable is also used but is not nearly as popular as stainless steel. Bright steel cable is seldom used, because of rusting.

Cable Construction Cable is very strong in tensile strength and is a suitable material for pedestrian railings. Most cable is flexible for going over pulleys or thimbles or for going around corners. For use in railings, however, one wants rigidity, not flexibility, because the cable needs to be as tight (rigid) as possible to minimize deflection and meet the 4" code requirement when a load is applied. Cable that is flexible also stretches, but for railings, as little stretch as possible under tension is important. The longer the cable run, the more a cable will stretch, which can present installation problems with long cable spans which stretch. Flexible cable constructions stretch more than constructions intended to hold static loads. Therefore, for most guardrail applications, we want to use a cable construction designed to hold static loads.

Cable Construction The following are common cable constructions. Note the characteristics of each. 1 x 19 Strand

Very rigid. Lowest stretch under load. 1 x 19 is the preferred cable construction for cable railings under most circumstances.

7x7 Cable

Less rigid and more stretch than 1 x 19

7 X 19 Cable

Less rigid and more stretch than 7x7

(May have application where sharp bends are involved and on shorter runs where stretch is a negligible factor.)

Under most circumstances, 1 x 19 construction is preferred for pedestrian railings.

Cable Breaking Strengths Following are breaking strengths in Lbs. of type 316 stainless steel cable for the above three cable constructions. Cable Diameter

Cable Construction 1X19

7X7

7X19

1/8”

1,780

1,360

1,300

3/16”

4,000

3,300

2,900

¼”

6,900

5,500

4,900

5/16”

10,600

7,600

7,600

3/8”

14,800

11,700

11,000

Tensile strength in pounds

Cable Sizes & Guardrail Applications Following are cable diameters up to 3/8". Unjacketed (Uncoated) Cable DIA.

Typical Applications

1/8”

Can be used on horizontal railings where there is little or no public pedestrian traffic or where railing does not need to meet code requirements (such as where there is little or no drop off). 1/8” diameter cable can be vulnerable to failure under shock loans caused by abuse, such as a heavy person applying a downward load on the cable. Can be used on vertical railings, which are not as susceptible to heavy shock loads as horizontal railings.

3/16”

Quite satisfactory for pedestrian railings. 3/16” and larger cable diameters have significantly higher load ratings than 1/8” and are, therefore, not as susceptible to failure. Relatively small diameter minimizes visual obstruction.

¼” 5/16” 3/8”

Diameter larger than 3/16” can be used where a larger diameter is desirable from a visual/aesthetic standpoint or where the application calls for a higher cable breaking strength than smaller diameter cable.

Handrails on Ramps The minimum clear width of a ramp shall be 36 in (915 mm). Ramps shall have level landings at bottom and top of each ramp and each ramp run. Landings shall have the following features: (1) The landing shall be at least as wide as the ramp run leading to it. (2) The landing length shall be a minimum of 60 in (1525 mm) clear. (3) If ramps change direction at landings, the minimum landing size shall be 60 in by 60 in (1525 mm by 1525 mm). (4) If a doorway is located at a landing, then the area in front of the doorway. Excerpt from 28 CFR Part 36: ADA Standards for Accessible Design

Handrails on Ramps • Handrails shall be provided along both sides of ramp segments. The inside handrail on switchback or dogleg ramps shall always be continuous. • If handrails are not continuous, they shall extend at least 12 in (305 mm) beyond the top and bottom of the ramp segment and shall be parallel with the floor or ground surface. • The clear space between the handrail and the wall shall be 1 - 1/2 in (38 mm). • Gripping surfaces shall be continuous. • Top of handrail gripping surfaces shall be mounted between 34 in and 38 in (865 mm and 965 mm) above ramp surfaces. • Ends of handrails shall be either rounded or returned smoothly to floor, wall, or post. • Handrails shall not rotate within their fittings. Excerpt from 28 CFR Part 36: ADA Standards for Accessible Design

Accessibility Requirements for Handrails

A handrail or grab bar and any wall or other surface adjacent to it shall be free of any sharp or abrasive elements. Edges shall have a minimum radius of 1/8 in (3.2 mm).

Excerpt from 28 CFR Part 36: ADA Standards for Accessible Design

Accessible Stairs Treads & Risers

Excerpt from 28 CFR Part 36: ADA Standards for Accessible Design

Accessible Stairs Treads & Risers

• On any given flight of stairs, all steps shall have uniform riser heights and uniform tread widths. Stair treads shall be no less than 11 in (280 mm) wide, measured from riser to riser • The undersides of nosings shall not be abrupt. The radius of curvature at the leading edge of the tread shall be no greater than 1/2 in (13 mm). Risers shall be sloped or the underside of the nosing shall have an angle not less than 60 degrees from the horizontal. Nosings shall project no more than 1-1/2 in (38mm) Excerpt from 28 CFR Part 36: ADA Standards for Accessible Design

Cane Detection Area

Ground and floor surfaces along accessible routes and in accessible rooms and spaces including floors, walks, ramps, stairs, and curb ramps, shall be stable, firm, slip-resistant. Excerpt from 28 CFR Part 36: ADA Standards for Accessible Design

Cable Coatings • Cable can be coated. It is common to use P.V.C. coating with UV inhibitors in clear or in colors. Due to the eventual UV breakdown in the compound over several years, it is not advisable to use P.V.C. coated cable in outdoor applications. • The cable diameter is increased when coated. A 1/16" increase in diameter is common. In some cases mounting and tensioning hardware may have to be altered to accommodate the coated cable. • Cable coatings tend to attract dust and dirt, which can present a cleaning problem. Some wish to coat cable because it will create a smooth surface. However, 1x19 construction, type 316 stainless steel cable is smooth to begin with, so coating this type of cable to make it smoother is not necessary.

Cable Lay The lay of the cable is the direction that the cable is wound during manufacturing. The tensioning device being used should be turned in the same direction as the lay of the cable to prevent unwinding ("birdcaging") of the cable. Therefore, right or left hand lay should be specified, depending upon the tensioning hardware used. If in doubt about the direction the tensioning device is turned, check with the manufacturer of the hardware.

Cable Spacing To meet the 4" code spacing requirement, cable needs to be spaced vertically less than 4" apart on the support posts. Cables must be centered vertically less than 4" apart, so that under load the cable will not flex enough to exceed 4" in open space at any point in the railing. Assuming properly designed end posts are being used (see Railing Frame Construction below), vertical spacing of the holes depends upon the length of cable run between frame elements that support the cable (such as intermediate posts). The closer the vertical spacing on the end post, the longer the run can be between supporting frame elements along the run.

Cable Spacing • Not wishing to space cables too close together, nor wanting to place too many support elements in the railing frame, the designer faces a compromise between the two. Following are suitable maximum spacings that balance the two elements using 1/8" through 3/8" diameter (unjacketed/uncoated) diameter 1 x 19 cable: –

–

Center-to-center hole spacing on posts and braces: 3" of free space between cables. For example, if you are using 1/4" diameter cable, add 1/4" to 3", to arrive at a center-to-center hole spacing of 3-1/4". Length of unsupported run between posts and braces: 42"

Cable Tensioning When tensioning cable, it is best to grasp the cable with locking pliers near the tensioning device as the cable is tensioned. This will prevent the cable from turning during the tensioning process. To avoid scarring the cable, locking pliers with special aluminum (or other soft metal) jaws are recommended.

Cable-Effects of Temperature Changes • Temperature changes can effect cable tension which, in turn, can effect cable flex. Frame elements, such as end posts and top and bottom rails, also expand and contract as temperature changes, which can offset to some extent the change in cable tension. • The diameter of the cable is a major factor in considering the effects of temperature changes on a cable in-fill railing. The larger the diameter of the cable, the greater the effect of temperature changes.

Cable-Effects of Temperature Changes The following chart illustrates the temperature change necessary to cause a total loss of 400 lbs. of initial pre-stress (tension) on cable in conditions where the railing frame is restrained from expanding and where it is free to expand. TEMPERATURE INCREASE vs. PRESTRESS LOAD TO CAUSE A TOTAL LOSS OF 400 lbs. PRESTRESS CABLE DIA.

CABLE IN FRAME REFRAINED FROM EXPANDING (1)

CABLE IN FRAME FREE TO EXPAND (1)

1/8”

+208 ºF

+315 ºF

3/16”

+ 93 ºF

+140 ºF

¼”

+ 52 ºF

+ 79 ºF

5/16”

+ 33 ºF

+ 50 ºF

3/8”

+ 23 ºF

+ 35 ºF

(1)Increase in temperature above temperature at cable installation or re-tightening. Where temperature variations are large, you should consider building expansion joints into the railing frame.

Railing Frame Construction

• In all cases, it is recommended that any metal framed railing using cable be engineered to be certain it will support the tension of the cables under load. You can check with your cable hardware supplier for available engineering data to use in designing your guardrail. • All railings need to be engineered to meet code requirements. Some additional considerations are necessary in designing a guardrail with cable in-fill that are not evident within building codes. Following are some of the design considerations you will want to take into account in designing a railing using cable.

Railing Frame Construction It is important to remember that cables must be tensioned when they are installed, to minimize cable flexing. Properly tensioned, each cable will exert between 400 and 600 pounds of tension on each end post. If there are ten cables being strung on the railing, a total of between 4,000 pounds and 6,000 pounds of tension will be applied to each end post. A properly constructed cable railing frame is extremely important to prevent the end posts from deflecting when the cables are properly tightened/tensioned.

Railing Frame Construction While cable runs between terminating end posts can be quite long, the cable must be supported with intermediate posts and/or cable braces frequently to prevent cable flexing. For structural purposes, the distance between posts/intermediate posts will depend upon the construction of the frame and the frame material used. In most cases, to minimize cable flex under load, the cable must be supported in some fashion much more frequently than the distance between posts for structural purposes.

Railing Frame Construction A strong top rail is essential, unless the end post to which tensioning hardware is attached is otherwise supported by means of guy-wires running from the post to the ground or some structure, securely fastened to a structure, or a deep core mount with a very heavy end post. Otherwise, when tensioned, the end posts will bend and it will not be possible to properly tension the cables.

Strong Top Rail

Deep Core Mount

Guy Wires Support

Mount To Structure

Railing Frame Construction There are three commonly used frame styles satisfactory for horizontal railings: Round Pipe, Rectangular Tube, and Square Tube. Flat bar is generally not recommended for end posts to which tensioning hardware is attached, unless it is very thick in the direction of the cable, reinforced with a tee, or secured firmly to a structure. Otherwise, it will bow when the cables are tensioned. Carbon steel (powder coated or painted) or stainless steel can be used.

Railing Frame Construction To reduce costs and minimize visual obstruction, braces with holes for the cable to pass through, attached to the top rail and to the bottom rail or mounting surface, can be used between intermediate posts to support the cables. ¼” x 1” flat bars are commonly used for this purpose.

Railing Frame Construction Round Pipe Construction. End posts should be constructed from schedule 80 OR XXS pipe, depending upon the diameter of the pipe and the height of the railing. Top rails, bottom rails (if applicable), and intermediate posts can generally be constructed from schedule 40 pipe. See the illustration below.

Railing Frame Construction Rectangular Tube Construction. End posts can be constructed from 3”x1” steel tubing with a .120” wall, using a double end post construction with round spacers between the tubes, as illustrated below. 3”x1”x.120” structural steel tubing can be used for top rails, bottom rails (if applicable) and intermediate posts.

Railing Frame Construction Square Tube Construction. End posts can be constructed using 2”x2” or larger structural steel tube with a minimum wall thickness of .250”. 2”x1”x.120” structural steel tubing can be used for top rails, bottom rails (if applicable) and intermediate posts. See illustration below.

Railing Frame Construction • Vertical Railings. Cables running vertically may be desired or, in some jurisdictions, required to avoid the ladder effect inherent in horizontally run cables. Vertical railings can be conveniently constructed using minimum schedule 80 1-1/4” or larger diameter pipe or square or rectangular structural steel tubing with a minimum wall thickness of .250”. For exterior applications, stainless steel should be specified, to inhibit rust in the holes drilled in the frame. • Using 1/8” or 3/16” diameter 1 x 19 construction cable, cables should be mounted on maximum 3.25” centers on railings up to 42” high.

Railing Frame Construction A convenient means of constructing a vertical railing is to drill and tap the holes on the under side of the top rail to accept threaded swaged studs on the upper end of each cable. Tabs can be welded to or (with some mounting tabs now available) screwed into the bottom rail, to accept some styles of tensioning hardware or, with hardware designed to be hidden inside the rail, holes are drilled in the bottom rail to accept that style of tensioning hardware. Steel bars or tubes are welded between the top and bottom rails at approximately 26” intervals to prevent the top and bottom rails from bending enough under the tension of the cables to be visually undesirable.

Railing Frame Construction • Vertical Railings.

Means of Preventing Rust (other than stainless steel frames) • It is generally best to paint or powder coat the railing prior to installation of the cables. When the cables are run through the posts and braces, however, the coating may be damaged. In exterior applications, that can introduce a rust problem. • To overcome the rust problem, where offered by the railing/hardware manufacturer, UV resistant grommets can be inserted into the holes (drilled oversize to accept the grommet), so the cable will run through the grommets rather than over the unprotected powder coated or painted surface.

Cleaning Stainless Steel Cable and Hardware Stainless steel cable and hardware can be cleaned with soap and water or commonly available stainless steel cleaner. A light wax coating where extremely severe corrosive environments are present will help keep the cable from discoloring.

Mounting and Tensioning Hardware Until the past few years, cable railing hardware choices were limited to products designed for industrial and marine uses. These products included various combinations of toggles, turnbuckles, eyes, and similar devices to attach and tension the cable the railing frame. Problems inherent in many of these devices can include unattractive or clumsy looking fittings, exposed threads, nuts, pins and other fasteners that collect dirt and grease, or have sharp edges which can catch on clothing, etc.

Mounting and Tensioning Hardware • More recently, hardware designed for cable railings has been developed to overcome the problems inherent in products that are designed for other uses. Following are some of the hardware items that have been designed especially for cable railings. • Tensioning devices, which are hidden inside, end posts, with only a small end cap visible from the back side of the railing, such as INVISIWARE® Receivers.

Invisible Receiver Tension Device • Invisible Receiver – Tension Device • A tensioning device hidden inside the end post, with only the head of the Receiver exposed on the outside of the post. The inside is female-threaded to accept the male-threaded Swaging Stud that is attached to the cable. The head of the Receiver is broached for an Allen wrench. To tension the cable, insert the Allen wrench and rotate the Receiver around the male threads on the Swaging Stud. This will draw the Swaging Stud further inside the Receiver, as you continue to turn it with the 'H' HEX Allen wrench.

Invisible Receiver Tension Device • Invisible Receiver – Tension Device • Pipe ends are counter bored, so the full perimeter of the head of the Receiver will rest on a flat surface in the pipe. The head rests on the outside wall of a flatsided post. A plastic washer is included and acts as a scratch resistant barrier between the Receiver head and the post. Post Receiver

Swaged Stud

Invisible Receiver Tension Device

Adjustable Tensioner Tensioning devices, which attach to the outside of the end posts, such as the fitting illustrated below:

Adjustable Tensioner The adjustable tensioner is a precision machined, sleek, streamlined tensioning device that is used where a "hightech" look is desired. It is suitable for level runs or stair pitches. The clevis portion of the fitting attaches to the end post with a button head socket screw that threads directly into a tapped hole on one side of the clevis fitting.

Adjustable Tensioner • Unlike common turnbuckles, the adjustable tensioner has no sharp edges, no crevices to collect dust and dirt, no large areas of exposed threads or exposed swaged shanks, and nothing that will scratch or snag.

• The clevis has a male thread that mates with the female thread within the body. The Invisible Swaging Ferrule is swaged onto the cable and holds the cable inside the body. The body rotates on the cable and provides a considerable amount of take-up during tensioning with an opened wrench. After tensioning, the lock nut locks the assembly in place.

Invisible Radius Ferrule For use on the fixed, non-tensioning end of the cable, often in combination with the receiver on the tensioning end, when installed, the fitting is hidden inside the end post, with only the head exposed on the outside of the end post.

Invisible Radius Ferrule Pipe ends are counter bored, so the full perimeter of the head of the radius ferrule will rest on a flat surface in the pipe. The head rests on the outside wall of a flat-sided post. A plastic washer is included and acts as a scratch resistant barrier between the radius ferrule head and the post.

Fixed Jaw Similar in appearance, the muff Jaw is about one-half the price of the clevis style tensioner. Where you do not need a tensioner on both ends of your cable run, the economical Fixed Jaw is frequently used on the fixed, non-tensioning end of the cable with the clevis-style tensioner on the tensioning end.

Fixed Jaw Fixed jaw makes a very attractive fitting where a "hightech" look is desired on level runs as well as on pitches. The swaging ferrule is swaged onto the cable and holds the cable inside the clevis.

Summary This course discussed design requirements for a railing using cable (also called wire rope or aircraft cable) as a railing infill. It also covered the different types of cable, the characteristics of different cable constructions, construction of the railing frame to prevent distortion when cables are properly tensioned, means of protecting against rust, and mounting and tensioning hardware alternatives to consider in designing a railing.

Course Summary The designer will now be able to: • Describe the unique design requirements for a railing using cable (also called wire rope or aircraft cable) as a railing in-fill. • List the different types of cable. • Explain the characteristics of different cable constructions. • Explain the construction and maintenance of a cable guardrail system.

www.thecableconnection.com

PEDESTRIAN CABLE RAILINGS

Guardrails with Cable In-Fill

Course Number: ult05a An AIA Continuing Education Program Credit for this course is 1 AIA HSW CE Hour Please note: you will need to complete the conclusion quiz online at RonBlank.com to receive credit

© Ron Blank & Associates, Inc. 2009

The Cable Connection Inc. 52 Heppner Drive Carson City, NV 89706 [email protected] Pedestrian Cable Railings 800-851-2961 Dan Nourse, Mgr., Sales & Cust. Serv. [email protected]