Dec. 02, 2024
Occasionally a guardrail system must be strengthened to reduce the design deflection distance. For example, a transition section is needed where a guardrail attaches to the approach end of a rigid concrete bridge rail (See the HKP article, Barrier Classifications (coming soon)). A guardrail must be stiffened if a rigid object obstacle is present within the design deflection distance. Standard installations can be modified using the following techniques to strengthen the guardrail:
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&#; Add a rubrail
&#; Install additional posts (reducing the post spacing) (See MGS Working Width Table in Section 3.11.)
&#; Use extra length posts (e.g., 7-foot or 9-foot posts, not the standard post length of 6 feet)
&#; Use thicker gauge posts (e.g., 10-gauge posts instead of 12-gauge posts)
&#; Double nest the rail
&#; Bolt a W-beam to back of the posts
For extra length posts and nested guardrail, quantities should be measured and bid items provided. Consult Section 719 of the Standard Specifications for Road and Bridge Construction for additional information. Where extra strength is needed different methods may be combined (e.g., when the area of concern is near the back of rail).
A guardrail is classified as a semi-rigid barrier due to its deflection distance upon crash impact (see the HKP article, Roadside Safety (coming soon), for a discussion on barrier categories). A transition section is needed when a guardrail connects to a rigid barrier (e.g., bridge railing or concrete barrier) or rigid object (e.g., bridge pier or sign structure). The transition should provide a gradual, continuous stiffening of the guardrail system from a less rigid to more rigid system. This reduces or prevents a vehicle from snagging or punching through the barrier. Use of a cast-in-place anchor or through-bolt connection is recommended to ensure the connections are as strong as the barrier itself.
Use TL-2 or TL-3 Thrie-Beam Guardrail Transitions to connect W-beam guardrail to concrete bridge rails, rigid barriers, or rigid objects. The TL-2 railing transition should be used when speeds are 45 mph or less. The TL-3 railing transition must be used when speeds are over 45 mph. For more details, see Standard Drawings Nos. BHS-013 and BHS-014.
Historically, the Guardrail Connector to Bridge End Type A was used on both bridge ends on undivided highways and on the approach bridge ends of divided highways. A Guardrail Connector to Bridge End Type A1 was used on the exit bridge ends of divided highways. A Guardrail Connector to Bridge End Type D was applied on each end of a bridge on which a sidewalk was present or its installation was proposed on the structure (and not on the roadway). This only applied to rural structures having two-direction traffic with a sidewalk.
Type A, A1, and D connectors are no longer installed on new highway construction. When repairing or restoring existing concrete barrier wall and these guardrail connectors, see Standard Drawings RBC-004, RBC-005, RBC-05N, and RBC-006. Refer to the RBB and RBC series of Standard Drawings in the HKP article, Bridge Railings and Transitions (coming soon), for more details.
On some retrofit projects use of standard guardrail connectors may not be appropriate. Contact Central Office Division of Maintenance for guidance.
Delineators must be installed on new guardrail. Standard Drawing No. RBR-055 (Delineators for Guardrail) illustrates delineator elements, placement, and spacing. Section 830 of the Standard Specifications addresses retroreflective requirements for guardrail delineators.
The District is responsible for deciding (1) whether to install new delineators on existing guardrail systems which lack delineation or (2) whether it is necessary to replace existing guardrail delineation due to non-reflective and/or missing delineators. High-priority locations for guardrail delineation include curves and ramps on freeways and expressways, as well as guardrail sections located in the median. The District may elect to place delineation to indicate openings at entrances on highways.
Where a guardrail end treatment adjacent to the roadway is marked, a Type 3 object marker is typically used. Alternating stripes of Type 3 object markers should slope downward, toward the side on which traffic is to pass. Generally, the end treatment manufacturer supplies Type 3 object markers. Use retroreflective sheeting that conforms to the size of the approach end.
Double-faced guardrail has two W-beam rails configured as a single beam on each side of post. It is typically used in the median in place of concrete barriers, particularly when the required shielding length is relatively short. Double-faced guardrail is also used when a guardrail may be exposed to impacts from either side. When installed near the pavement edge, it is critical for the area between the posts to be free of asphalt.
On longitudinal guardrail installations, double blockouts (up to 16 inches deep) may be used to increase the post offset to avoid obstacles such as curbs. There is no limit on the number of posts that can have double blockouts installed.
Do not employ double blockouts for transitions and terminals, unless approved by the manufacturer. Under special circumstances (e.g., avoiding buried obstacles that are not relocated), additional blockouts may be installed to obtain up to 24 inches of clearance (three 8-inch blockouts or two 12-inch blockouts) for one or two posts in a section of guardrail. Standard Drawing RBR-031 (Guardrail End Treatment Type 3 Pipe Drainage Detail) offers an example of using extra blockouts.
Omit a post only under special circumstances and only on a standard run of guardrail. Omitting a post requires the construction engineer&#;s approval.
Single posts may be omitted along runs of MGS W-beam guardrail without the system needing modification (i.e., no weakened posts, no nested rail elements, no special posts). Always consider the following issues before taking this step:
1. At least 50 feet is required between omitted posts, a terminal, or other special design.
2. Omitted posts cannot be used within transitions, terminals, or special designs.
3. No curbs are present where guardrails are installed.
4. Additional deflection resulting from the omitted post.
Occasionally, an intersecting side road or driveway is located so close to a side obstacle that installing a minimum length MASH TL-3 guardrail is infeasible. This most occurs often at bridge ends. A short radius curved guardrail installation may accommodate this situation. See Standard Drawing RBI-001 for more details.
Keep the following in mind when designing a short-radius curved guardrail:
&#; Installations at intersections and driveways can create nuisance hit problems for turning traffic (e.g., tractor trailers turning off of or onto side roads, farm implements turning into and out of field entrances). Check turning patterns to ensure a guardrail installation will not significantly affect turning movements.
&#; Installations at intersections and driveways can obstruct motorist sight, especially if the side road or entrance is at or near the crest of a vertical curve. Perform sight distance analysis for both plan and profile views to determine what effects guardrail installation may have on motorist line-of-sight.
On roadways where the design speed is between 30 and 45 mph and there is a curb adjacent to the traveled way (e.g., urban and suburban roadways), keep the border area free of obstacles. Any decision to use a guardrail within the border area should be informed by careful evaluation. A guardrail used in the border area should present less of a hazard than the obstacle it shields. See Chapter 10 of AASHTO&#;s Roadside Design Guide for further guidance on clear zones in urban areas.
Use the appropriate omitted-post design (as discussed above) if rock is present where a single guardrail post is to be installed. If rock is present at several points where posts will be installed, place the posts in cored holes (see Section 719.03.01 of the Standard Specifications for Road and Bridge Construction).
When shales are used in embankment fill sections, acidic shale is generally encased inside the embankment. At least 4 feet of nondurable shale or clay soil should be placed atop the embankment to control the corrosion of guardrail posts. It may be appropriate to install corrosion-resistant guardrail posts. See Special Note 8N Corrosion Resistant Guardrail and the Geotechnical Guidance Manual GT-609-5 on Acid-Producing Shales.
Horizontal lagging walls are often used for temporary or permanent retention of soil material and other backfill. Lagging may consist of wood, guardrail, or geogrid. When backfill is placed or compacted behind the guardrail wall, it is imperative that rails not to be damaged.
Lagging has traditionally been designed based on experience or empirical methods. (e.g., the Federal Highway Administration uses the Goldberg Zoino chart). Contact the Geotechnical Branch for more information.
&#;Everyone goes home.&#;
While it is one of the mantras of the National Fallen Firefighters Foundation and their safety campaigns, &#;Everyone goes home&#; easily correlates to fall prevention measures for workers performing their duties at height.
The goal for every employee working at height is to make it home safely at the end of every shift. Mazzella FHS Fall Protection Specialists utilize many different systems to help accomplish this task.
Whether you&#;re working on scaffolding, rooftops, or walking surfaces, guardrails are an option for fall prevention.
In this article, you&#;ll learn about the:
According to OSHA (Occupational Safety and Health Administration) Publication , there are nearly 6,000 workplace fatalities in the United States and 50,000 deaths due to workplace-related illnesses each year. Also, there are 5.7 million non-fatal workplace injuries, which cost U.S. businesses over $125 billion annually.
Falls are the leading cause of deaths in the construction industry, and most fatalities happen when employees fall from open-sided floors and through floor openings. Falls from as little as 4&#; to 6&#; can cause long-term time away from work, and in the most severe cases, death, which means all open-sided floors and platforms 6&#; or more in height must be guarded.
Guardrails serve as passive fall protection in the Hierarchy of Fall Protection. The standard guardrail system features a toprail, intermediate (or mid) rail, and support posts.
To add more layers of protection, screens, mesh, or balusters could be utilized in tandem with the guardrails.
Guardrails need to have a minimum breaking strength of 200 lbs. in any direction per OSHA .29(b)(3)(4)(5). A guardrail consists of a top rail 42&#; + or &#; 3&#; no less than 39&#;, mid rail at 21&#; and toe board 3.5&#; high. Guardrails should be inspected per the manufacturer specifications or a qualified person&#;s requirements.
Midrails are halfway between toprail and walking / working surface, and must stand up against a downward and outward directional force of at least 150 lbs.
If wire-rope guardrail systems are utilized, highly visible tape or flags must be placed every 6&#; to increase visibility.
Toe boards shall be provided when employees below could be exposed to falling objects such as tools. Toe boards shall be at least 3.5&#; (8.9 cm) in height from top edge to floor level, and be capable of withstanding a force of 50 lbs. (222 N) applied in any direction.
Guardrail requirements are listed in the OSHA .451(g)(4) standard.
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In this standard, OSHA says: &#;Guardrail systems shall be installed along all open sides and ends of platforms. Guardrail systems shall be installed before the scaffold is released for use by employees other than erection / dismantling crews.
&#;The top edge height of toprails or equivalent member on supported scaffolds manufactured or placed in service after January 1, , shall be installed between 38&#; (0.97 m) and 45&#; (1.2 m) above the platform surface. The top edge height on supported scaffolds manufactured and placed in service before January 1, , and on all suspended scaffolds where both a guardrail and a personal fall arrest system are required shall be between 36&#; (0.9 m) and 45&#; (1.2 m). When conditions warrant, the height of the top edge may exceed the 45&#; height, provided the guardrail system meets all other criteria of paragraph (g)(4).&#;
&#;Shall&#; is defined as mandatory, according to OSHA .32(q).
When midrails, screens, mesh, intermediate vertical members, solid panels, or equivalent structural members are used, they shall be installed between the top edge of the guardrail system and the scaffold platform.
When midrails are used, they shall be installed at a height approximately midway between the top edge of the guardrail system and the platform surface. When screens and mesh are used, they shall extend from the top edge of the guardrail system to the scaffold platform, and along the entire opening between the supports.
OSHA states that guardrails shall be surfaced to prevent injury to an employee from punctures or lacerations, and to prevent snagging of clothing.
According to the standard, steel or plastic banding shouldn&#;t be used as a toprail or midrail. Also, manila or plastic (or other synthetic rope) being used for toprails or midrails shall be inspected by a competent person as frequently as necessary to ensure that it continues to meet the strength requirements of a minimum 200 lb. capacity.
Cross-bracing is acceptable in place of a midrail when the crossing point of two braces is between 20&#; and 30&#; above the work platform or as a toprail when the crossing point of two braces is between 38&#; and 48&#; above the work platform. The end points at each upright shall be no more than 48&#; apart.
Guardrails are commonly used for walkways / working areas inside factories, and they are important components of scaffold platforms.
For adequate fall protection while using scaffolds 10&#; or more above a lower level working surface, workers must be protected with a personal fall arrest system or guardrail system.
Depending on the type of scaffold being utilized, a guardrail system AND personal fall arrest system may be required.
On scaffolding, guardrails are mandated to be installed along all open ends and sides of the platform before the systems are fit for use.
Like other fixed guardrails, workers on scaffolds must be protected by a toprail, midrail and toe board to prevent objects that are kicked off the deck from falling down and injuring workers on lower levels of projects.
When exiting the top of the ladder to climb onto a surface, such as a roof, do you have unguarded edges?
If the answer to that question is yes, fall protection must be maintained. Guardrails or a personal fall arrest system would be your best options.
Scissor lifts are considered a mobile scaffold, and you may be required to wear a personal fall restraint system. However, it is important to remember to connect to the manufacturer&#;s designed anchorage point. You never want to use a guardrail as an anchor point.
Also known as boom lifts or articulating boom lifts, aerial work platforms support workers on an elevated surface. Aerial work platforms allow employees to work freely with both hands and prevent falls, but you always want to wear a full body harness while in use.
The full body harness must be attached with a lanyard to the manufacturer&#;s designed anchor points.
If you&#;re working on a suspended scaffold system, like window washers, having vertical lifelines fixed to the roof or another structural surface would be the preferable option.
It is important to remember guardrail systems are designed and installed to adhere to ASME and OSHA safety standards.
Guardrails are designed and built to specific safety regulations and should not be modified in any way. If there is damage to a guardrail, the fall prevention system must be repaired promptly. Also, guardrails should not be used as an anchor point for fall protection systems, Should a guardrail section be removed for the delivery of materials, fall protection systems need to be in place.
While considered a fall prevention measure, guardrails are a part of Mazzella&#;s warehouse solutions division.
Mazzella FHS has designed and implemented material handling and storage solutions for a variety of industries focusing on warehousing and manufacturing applications, and many of those solutions include guardrails. This vast experience has provided us with a deep understanding of our clients&#; most challenging requirements.
We are driven by a highly experienced team of experts working closely with our clients to develop the most viable solutions for their needs. Our designers, engineers, sales engineers, and project managers are experienced professionals, and as such, strive daily to provide our products and services to our clients &#;On-Time and &#;On-Budget&#;.
In addition to providing guardrail solutions, Mazzella FHS also offers a full range of services such as site audits and surveys, repairs, full installation services, and fall protection systems.
Call us at 800.362. or click here if you think a guardrail system would be a good option for your company&#;s fall prevention and / or warehouse solutions needs, or to schedule training for your workers at height!
We are a leading supplier and installer of engineered fall protection systems in the U.S., as well as a distributor of soft goods like harnesses, lanyards, self-retracting lifelines, scaffolding and netting. All of our engineered systems and products meet or exceed the federal criteria required by OSHA and ANSI and can be customized with your individual fall protection and financial needs in mind.
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