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Cable railings, or wire rope railings, are safety rails that use horizontal or vertical cables in place of spindles, glass and mesh for infill.
Cable railings are often desired in place of traditional pickets to achieve nearly unobstructed views as the cable is much thinner than traditional pickets. It is also a more modern aesthetic and is often chosen for that reason.
You can install cable assemblies into an existing railing system (called cable infill [1] ) and eliminate many of the maintenance headaches.
Due to the excessive load requirements [2] of this type of railing system, post construction is critical to the success of cable railings.
Cable railing requires very rigid frames compared to many other types of railings due to the forces applied to the end posts by tensioning the cables. Cables must be tensioned to provide minimum cable deflection using 4-inch sphere, to satisfy building code requirements. [2] Manufacturers use different methods to achieve the same result, one manufacturer uses a thicker wall and a webbed post in their aluminum systems, while using only thicker side walls in their stainless systems. Common frame types are constructed of steel, stainless steel, extruded aluminum or wood.
The total minimum height required varies per building codes depending on the area and target use of either residential or commercial. Local city codes supersede state, national and international code. In most states, the residential code is 36 inches high. There are some exceptions, though, like in California [3] the required height for residential railing is 42 inches. On the other hand, the commercial International Building Code requires the railing to be at a minimum of 42-inch height. Posts can be floor-mounted or fascia/side-mounted, but the height of the railing is measured from the floor to the top of the railing.
Guidelines for spacing between cable components are straightforward and simple. According to international building codes ICC, [4] openings between cables should not exceed 4". Moreover, a 4" sphere should not be able to pass through the openings. Spacing between posts should be kept consistent (when possible) along the assembly. For 36” posts or 42" posts, 4 feet of spacing (center to center) is recommended to minimize deflection between the cables when pushing a 4" ball in between two cables. To accommodate such standards, railing projects may incorporate 3 ½" or less of spacing between cables taking into account the cable deflection caused by the posts spacing. This configuration would streamline compliance with the 4" sphere requirement.
Cable is very strong in tensile strength, with a breaking strength in excess of 1000 lbs for these types of uses, and is a suitable in-fill material for a railing ("guard" in ICC codes). Typical diameters are 1/8", 3/16" for residential and 3/16" and 1/4" for commercial applications. [5] There are many different types cable and strand (also referred to as wire rope). Cable and strand is available in galvanized carbon steel, type 304 stainless steel, or the highly corrosion resistant, type 316 stainless steel (best for coastal areas). The most common cable construction is 1x19 type construction strand, which is 19 cables twisted in a single bundle, whereas for example, 7x7 would be 7 cable bundles of 7 cables twisted. This type of stainless strand is designed to have limited stretch, as compared to galvanized, [6] making it a good long term cable railing solution. It has long been used for yacht stays and guy wires, proving its outdoor durability and strength.
Cable flexibility is an important consideration in designing a cable railing. The old UBC (Uniform Building Code) and newer ICC (IBC and IRC) [4] codes state that a 4” sphere shall not pass through any portion of a barrier on a guardrail. In a horizontal or vertical cable rail, the cables, once tensioned must be rigid enough to prevent a 4-inch sphere passing through it. Factors influencing this rigidity are: the tension of the cable, intermediate posts (or cable spacers) spacing, the diameter of the cable, top rail cap material and the cable to cable spacing. [7] The application of the 4" sphere test is usually at the discretion of a code enforcement official who will interpret the force behind the 4" sphere so it is advised that cable spacing not be more than 3" over a 48" space between post.
Cable tension: An incredible amount of tension is generated on the end posts when ten or more cables, each tensioned at 200-400 lbs. over a height of 36" to 42” exists. Underestimating the tension of cables applied to end poles can cause a safety hazard. Cable can have too much deflection allowing body parts to slip through, or cables can merely "pull out" of the end fittings, causing the cable rail to fail. Poorly designed end posts will result in a railing where the cables cannot be properly tensioned without an unacceptable amount of cable deflection. End posts to which the tensioning hardware attaches must be constructed so that they will not deflect perceptibly.
Post spacing: Intermediate posts are posts which provide mounting for the top rail and have a vertical row of holes to support the cable as it passes through them. Since the post to post spacing is a primary driver of cable rigidity, the post to post spacing is very important. It is generally recommended that post spacing be no more than 5 ft on center Some manufacturers require as little as no more than 3 ft on center. The reason for post spacing is more about the cable end fittings' machine thread loading capacity (how much tension can be put on the threads before they fail), than anything else. The more cable drop in the middle, the more weight on the tensioning device, ergo the more load on the threads. Proof strength must be greater than load.
Cable diameter and properties: The next variable is the diameter of the cable. Cables can be any wire rope, which meets load strength requirements by the ICC. [7] The most available types are 1x19 1/8", 1 x 19 5/32", 1x19 3/16", 7x7 3/16" and 1x19 1/4". 1 x 19 cable is the most rigid cable available and per the first paragraph above will have greater resistance to the 4" sphere test and likewise have a lesser chance of allowing objects 4" and over to slip through the cable. 316 Stainless Steel is preferred, due to its inherent nature against stretching, keeping long term maintenance down, as well as having anti-corrosive properties. [8]
Top rail: Top rail material must be strong as it is being compressed by the combined cable forces. Common top cap materials are the stronger species of wood or metal. Composite lumber can be used if a support rail is used along with it. The support rail is used between the posts to lend strength to the system, both between the posts, and to the Top Rail.
Cable to cable spacing: Spacing of the cables vertically is critical to minimize deflection of the cables. Most manufacturers recommended maximum vertical spacing of no more than 3-inch free opening between cables when they are installed to meet cable deflection requirements as stated above.
All of the above factors work together to minimize the deflection of the cable to prevent a 4” sphere from passing between the cables when they are properly tensioned in a well-designed frame. This is a requirement according to a number of building codes. Among the more stringent, including that of California, [9] this requirement may be used in conjunction with a weight being hung from the cable.
Cable end fittings [10] are the pieces that tie the system together. The cable attaches into one side of the fitting, while the other side attaches to the post (frame structure). Cable ends may tension, or just attach to the frame, depending on the individual needs of the project. [11] The requirements needed to decide whether to use tensioning or non-tensioning fittings are generally dependent upon the manufacturer's system requirements, your local building codes, and ICC requirements. To determine the type of cable end fittings needed, you'll need to know the distance you expect a single piece of cable to run without stopping, and the amount of tensioning ability of the fitting you expect to use. Individual manufacturers will help you to determine the rest. Most cable end fittings are made by type 316 stainless steel to avoid rust. [12]
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridges, which lack vertical suspenders, have a long history in many mountainous parts of the world.
Rebar, known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar's surface features a continuous series of ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage.
Standing rigging comprises the fixed lines, wires, or rods, which support each mast or bowsprit on a sailing vessel and reinforce those spars against wind loads transferred from the sails. This term is used in contrast to running rigging, which represents the moveable elements of rigging which adjust the position and shape of the sails.
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire- and tube-drawing machines, printing presses, cars, motorcycles, and bicycles. It consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket. It is a simple, reliable, and efficient means of power transmission.
A beam is a structural element that primarily resists loads applied laterally to the beam's axis. Its mode of deflection is primarily by bending. The loads applied to the beam result in reaction forces at the beam's support points. The total effect of all the forces acting on the beam is to produce shear forces and bending moments within the beams, that in turn induce internal stresses, strains and deflections of the beam. Beams are characterized by their manner of support, profile, equilibrium conditions, length, and their material.
A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.
Prestressed concrete is a form of concrete used in construction. It is substantially "prestressed" (compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service.
A curtain wall is an outer covering of a building in which the outer walls are non-structural, designed only to keep the weather out and the people in. Because the curtain wall façade carries no structural load beyond its own dead load weight, it can be made of lightweight materials. The wall transfers lateral wind loads upon it to the main building structure through connections at floors or columns of the building.
A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the subfloor sheathing, allowing it to function as a horizontal diaphragm. Joists are often doubled or tripled, placed side by side, where conditions warrant, such as where wall partitions require support.
A utility pole is a column or post typically made out of wood used to support overhead power lines and various other public utilities, such as electrical cable, fiber optic cable, and related equipment such as transformers and street lights. It can be referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, telegraph pole, or telegraph post, depending on its application. A Stobie pole is a multi-purpose pole made of two steel joists held apart by a slab of concrete in the middle, generally found in South Australia.
Falsework consists of temporary structures used in construction to support a permanent structure until its construction is sufficiently advanced to support itself. For arches, this is specifically called centering. Falsework includes temporary support structures for formwork used to mold concrete in the construction of buildings, bridges, and elevated roadways.
A fly system, or theatrical rigging system, is a system of ropes, blocks (pulleys), counterweights and related devices within a theater that enables a stage crew to fly (hoist) quickly, quietly and safely components such as curtains, lights, scenery, stage effects and, sometimes, people. Systems are typically designed to fly components between clear view of the audience and out of view, into the large opening, known as the fly loft, above the stage.
A handrail is a rail that is designed to be grasped by the hand so as to provide safety or support. In Britain, handrails are referred to as banisters. Handrails are usually used to provide support for body or to hold clothings in a bathroom or similar areas. Handrails are commonly used while ascending or descending stairways and escalators in order to prevent injurious falls or to hold necessities. Handrails are typically supported by balusters or attached to walls.
Guard rail, guardrails, or protective guarding, in general, are a boundary feature and may be a means to prevent or deter access to dangerous or off-limits areas while allowing light and visibility in a greater way than a fence. Common shapes are flat, rounded edge, and tubular in horizontal railings, whereas tetraform spear-headed or ball-finialled are most common in vertical railings around homes. Park and garden railings commonly in metalworking feature swirls, leaves, plate metal areas and/or motifs particularly on and beside gates.
In the electrical wiring of buildings, a cable tray system is used to support insulated electrical cables used for power distribution, control, and communication. Cable trays are used as an alternative to open wiring or electrical conduit systems, and are commonly used for cable management in commercial and industrial construction. They are especially useful in situations where changes to a wiring system are anticipated, since new cables can be installed by laying them in the tray, instead of pulling them through a pipe.
Traffic barriers keep vehicles within their roadway and prevent them from colliding with dangerous obstacles such as boulders, sign supports, trees, bridge abutments, buildings, walls, and large storm drains, or from traversing steep (non-recoverable) slopes or entering deep water. They are also installed within medians of divided highways to prevent errant vehicles from entering the opposing carriageway of traffic and help to reduce head-on collisions. Some of these barriers, designed to be struck from either side, are called median barriers. Traffic barriers can also be used to protect vulnerable areas like school yards, pedestrian zones, and fuel tanks from errant vehicles.
Grab bars are safety devices designed to enable a person to maintain balance, lessen fatigue while standing, hold some of their weight while maneuvering, or have something to grab onto in case of a slip or fall. A caregiver may use a grab bar to assist with transferring a patient from one place to another. A worker may use a grab bar to hold on to as he or she climbs, or in case of a fall.
A cable barrier, sometimes referred to as guard cable or wire rope safety barrier (WRSB), is a type of roadside or median safety traffic barrier/guard rail. It consists of steel wire ropes mounted on weak posts. As is the case with any roadside barrier, its primary purpose is to prevent a vehicle from leaving the traveled way and striking a fixed object or terrain feature that is less forgiving than itself. Also similar to most roadside barriers, cable barriers function by capturing and/or redirecting the errant vehicle.
Deck railing is a guard rail to prevent people falling from decks, stairs and balconies of buildings. Over time, many different styles of deck railing have been developed.
An electrical conduit is a tube used to protect and route electrical wiring in a building or structure. Electrical conduit may be made of metal, plastic, fiber, or fired clay. Most conduit is rigid, but flexible conduit is used for some purposes.
