Barrier & Railing Construction

Similar to floor construction in importance, is the choice of railing you as a bridge owner or engineer will specify. The selection of a railing or barrier has an effect on many dimensions and details for construction. The different railing specifications we follow provide for an array of solutions addressing safety, aesthetics, costs and longevity.

W Beam

The W-Beam Rail is a basic 12 ¼” steel guardrail shape attached to steel posts or truss girders. It is a simple railing that usually is accompanied by a block out between it and its supporting element. It can be strengthened by doubling it, sometimes called “nested rail”. It also can be strengthened by backing it up with continuous tubular steel elements. Standard rail lengths (12’-6”) and hole-locations (patterns are 6 ¼” from the end) are usually used across the bridge in an attempt to economize the fabrication costs. Many times these are adjusted accordingly by custom cutting and punching the rail pieces to coordinate with truss members or designed post spacings. The rail pieces have slotted holes for their final adjustment when attaching to their posts and any terminal pieces. The height specified for this railing is commonly 27” from the top of the rail to the pavement. This translates to a dimension of 1’-9” to the mounting bolts. US Bridge will supply any standard or custom fabricated W-Beam Rail that is needed for your bridge project.

Thrie Beam

Steel Thrie-Beam Rail is similar in nature to the W-Beam Rail except it is deeper (20” tall) than the W-Beam. It is considered a more robust section and used where higher traffic volumes are expected with a traffic mix trending toward heavier trucks. Like the W-Beam, it comes in standard rail lengths of 12’-6” and is similarly mounted and spliced except that it has two rows of mounting bolts instead of one. US Bridge will supply any standard or custom fabricated Thrie-Beam Rail that is needed for your bridge project.

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Some thrie beam rail standards we fabricate:

State Agency  Standard Name or Drawing
    Top Mount Side Mount
Missouri MoDOT  THB 1A N/A
New York  NYSDOT BD-RL2E N/A
Oregon ODOT  N/A BR233
Wisconsin WisDOT  30.02 N/A
Indiana InDot N/A TS-1

Tubular

One of the most common steel railing constructions in use today by State Departments of Transportation is a multi-element tubular rail system.  Built alone or in combination with a concrete curb or low barrier wall, this post and beam rail type has demonstrated great strength and utility both as a traffic barrier and as a combination barrier.  Many different crash-tested standards exist among the different state DOT’s and their heights above pavement varying as well.  Each is able to be accommodated in our design and planning, if the standard to follow is designated.  Please make sure your plans or your scope of work references the particular standard you are requiring.  Some common rail standards we fabricate include:

 

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 Some Tubular rail standards we fabricate:

State Agency Standard Name or Drawing
    Top Mount Side Mount Curb/Sidewalk Mount Wall Mount
Ohio ODOT N/A  TST-1-99 N/A  BR-2-98
Pennsylvania PennDOT N/A   N/A Type 10M N/A
New York NYS DOT BD-RS-1E
BD-RL3E
N/A  BD-RS1E N/A
Virginia VDOT N/A  N/A  BIR-1 thru 5 N/A
Massachusetts MassDOT N/A  N/A  S3-TL4 N/A
Texas TxDot N/A N/A  T1W T401
Oregon ODOT N/A  BR226 BR206 & BR208 BR214
Indiana InDOT N/A  N/A  Type CF-1 Type TF-2
Wyoming WyDOT N/A  N/A  TL3 & TL4 N/A
Wisconsin WSDOT 30.16 N/A 30.01 30.17 & 30.18

 

Concrete Safety Shape

Simply put, a poured concrete barrier, integrally attached to a concrete deck slab, is a very robust and resistant bridge railing. It is common for higher speed roadways and places where run-off the road accidents are prevalent. It of course, is not always specified by bridge owners, because for one, it is expensive to construct and two, it is a barrier to open viewing. In essence, it is not always warranted or preferred. As mentioned above, wall barriers are sometimes combined with tubular rail systems and this provides a nice compromise between robust construction and visibility. Any of these walls or barrier designs can be specified and constructed with all of our beam or truss bridge styles.

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Some common barrier standards for review:

State Agency  Standard Name or Drawing
    Safety of F Shape Single Slope Corral or Balustrade
 Ohio  ODOT BR-1 SBR-1-99  N/A 
New York NYS DOT BD-RC1E BD-RC11E N/A
Massachusetts MassDOT CF-PL2 N/A CT-TL2
Texas TxDOT TSS1 SSTR N/A
Michigan MDOT 6.29.09 N/A N/A
Indiana InDOT TYPE FC N/A N/A
Arizona AZDOR SD 1.01 N/A N/A
Florida FDOT 420 420 424
Oregon ODOT BR200 N/A BR212
Wisconsin WSDOT 30.12 30.30 30.19

Ornamental

Ornamental or architectural steel railings for pedestrian ways are not a part of every bridge we build, but when they are, they can be a beautiful addition to the bridge and bring attention to the bridge for viewers on and off the bridge. Many times these are included on bridges entering a town area where aesthetic treatments are being highlighted and visual impact is important. Your rail design is important. If you have an idea or would like to see some options, we are available to help with ideas, or help visualize what is possible.

More About Railings

We will build your bridge around whatever railing or barrier you specify. If you’re having trouble making this choice, please give us a call. Chances are we’ve designed something similar to what you’re considering.

Two types of construction exist to separate traffic from the edge of the deck: barriers and railings. Barriers are made from poured concrete and integrally attached to a concrete deck slab. They are also called parapets or parapet walls. They can be shaped in various ways to deflect errant vehicles back into the traveled lanes. The second construction is called post and beam “railings” and is made from vertical steel posts and horizontally oriented steel beams. The posts can be made from many different steel elements to support the rail members. The rail members also vary in number and shape ranging from a simple w-shaped
guardrail to multiple lines of tubes, plates or channels. Just keep in mind, railings are important as they can be designed to blend in to the bridge mass, or they can be designed to highlight a bridge’s aesthetics and show off both the view from the bridge, or show off its form from the bank edge.

An excellent discussion about railings that include examples and details can be found at:

1: Online Guide To Bridge Railings
2: U.S. Department of Transportation, Bridgeway Guide
3: U.S. Department of Transportation,
FHWA Safety

Railings alongside sidewalks are used to protect pedestrians from the drop off at the edge of the bridge and sometimes used to separate pedestrians from traffic.

They are known as either inboard or outboard to the sidewalk, and either pedestrian or combination (traffic & pedestrian) railings. Depending on the traffic volume and design speed, a bridge owner may want to separate the traffic from the pedestrians. If this is the case, the inboard railing will be designed as a combination rail and the outboard railing can be designed as a pedestrian railing. If traffic is not separated, the sidewalk will be elevated and the outboard railing will be designed as a combination railing. Pedestrian rails look different than traffic or combination railings as they commonly provide a rub rail and hand rails and they tend to be more ornamental or aesthetic. Traffic or combination rails are heavy, robust construction made from poured concrete or heavy steel post and beam members, or both.
Commonly Used Terms:
Railing

Railing is a general bridge term that means barrier or element that protects vehicular traffic or pedestrians from the drop off at the edge of a bridge or elevated structure. Railings have many forms and construction types.

Barrier

Barriers are made from poured concrete and are integrally attached to a concrete deck slab through reinforcing steel. It is commonly referred to as a Jersey barrier which was developed in the 1950’s by the New Jersey State Highway Department. Other common barrier names throughout the country include the Kansas Corral Barrier, the Iowa Concrete Open Rail (Barrier) and the 42″ Single Slope Concrete Barrier.

Crash Tested

It is very important to know whether the railing or barrier system on the bridge needs to be designated as “Crash Tested”. The answer to this question usually can be determined by understanding how the project is being funded and whether your state department of transportation has any review authority over the project. If they do, you will need to find guidance or seek advice about crash test levels required for different highway facilities. If you can’t find it, just give us a call and we will do our best to find out. Crash Test Railing Systems are defined by FHWA. According to the FHWA, they “… require all bridge railings used on the National Highway System (NHS) to meet full-scale crash criteria. The test criteria are documented in the AASHTO Manual for Assessing Safety Hardware (MASH), which is a 2009 update of NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. The FHWA reviews test results and issues acceptance letters for each bridge rail that is tested according to the evaluation criteria. The acceptance letters are available on the FHWA web site at: Bridge Railings - FHWA Safety Program

Fascia Mounted

This refers to railing posts connected to the outermost steel framing members through the use of bolted connections. The railing can be blocked out or attached directly to the post.

Truss Mounted

This refers to the horizontal railing elements being connected to the vertical or diagonal members in the truss girders. The railing attachment can vary between a bolted and welded connection. Many times this connection is built off of a steel bracket or it can be blocked out using a neoprene, timber or steel spacer, all being attached directly to a truss member.

Curb Mounted

This refers to vertical posts being anchored into the concrete curb of a bridge deck slab. The deck drains along the gutter formed by the curb. Usually the post has a steel base plate that is attached using four heavy anchor bolts.

Slab Mounted (Top)

In a very similar way to the Curb Mounted rail, this connection refers to vertical posts being anchored onto the top of the concrete bridge slab. The deck drains over the side of the bridge slab. Usually the post has a steel base plate that is attached using four heavy anchor bolts. The base plate can be mounted directly to the slab or it can be held slightly above the slab and filled with a grout pack.

Slab Mounted (Side)

This connection refers to vertical posts being anchored onto the side of the concrete bridge deck and requires a poured down slab edge that is deeper than the internal slab thickness. The deck drains over the side of the bridge slab and over the anchorage unless a splash guard is installed at each post location. The post usually connects to heavy anchor bolts that connect to embedments with coil insert.

National Highway System (NHS)

According to FHWA’s website, “The National Highway System consists of roadways important to the nation's economy, defense, and mobility. The National Highway System (NHS) includes the following subsystems of roadways: Interstate System, Other Principal Arterials, Strategic Highway Network (STRAHNET), Major Strategic Highway Network Connectors, and Intermodal Connectors.”

Maps of each state’s NHS routes

Pickets

Pickets are tightly spaced vertical or horizontal elements connecting parts of the railing to prevent small children or objects from falling through.

Embedments

A steel element, usually a plate, that is cast into the concrete that is designed to allow steel members to be connected to it and thus to the supporting concrete. These can be galvanized plates with welded, headed studs. They can be backed with coil inserts or sleeve nuts to receive anchor bolts through the embedment plate.

Approach Guardrail Transition Region

Known also as bridge terminal assemblies, these details provide for a transition that smoothly changes the bridge railing shape to a typical ground-mounted guardrail or guide rail system. They also transition the stiffness between the more flexible ground mounted system and the stiffer bridge railing to prevent vehicle pocketing and wheel snags. Bridge transitions or assemblies are very specific, crash tested constructions that are standardized by state DOT’s. Familiarity of these standards is encouraged.

Calculated Equivalent

At the direction of an approving bridge owner, a barrier or railing assembly may be accepted as having “calculated equivalency” with a predetermined crash test level by way of, and in accordance with the guidance shown in AASHTO LRFD Bridge Design Specifications, Appendix A13 of Section 13. This Section outlines a process for designing a crash test prototype that, when analyzed per this Section, has been accepted in many states as equivalent to a Crash Test Level.

Block Out

A spacer made from steel, timber or rubber that extends the railing element outward away from the supporting post to lessen the potential for wheel snag.

Rub Rail

Also sometimes called a toe rail, this lower railing element is added to the system to function like a curb, protecting against wheel snag.