“see-through” bridge rails shannon post/ greg kaderabek caltrans division of engineering...

“See-Through” Bridge Rails

Shannon Post/ Greg Kaderabek

Caltrans

Division of Engineering Services

August, 2011

Agenda:

1. Introduction

Bridge Barriers and Railings

2. Development of See-Through Rails

Applications

Desired Features

3. See -Through Alternatives

4. Cost Comparison

5. FAQs

6. Next Steps

7. Your Questions..

Bridge RailsClasses of Railings

Railing Types Functiona.) Vehicular Barrier Railings Retain and redirect errant vehicles

b.) Combination Vehicular Barrier and Pedestrian Railings

Dual function of retaining both vehicles and pedestrians on the bridge. Consist of two parts: concrete parapet, generally with a sidewalk and a metal hand railing or fence-type railing

c.) Pedestrian RailingsPrevent pedestrians from accidentally falling from the structure

d.) Bicycle Railings

Retain bicycles and riders on the structure. May be a combination type consisting of a vehicular railing surmounted by a fence or metal handrail

Bridge RailsDesign and Crash Criteria

Criteria SpecificationStructural

DesignAASHTO LRFD Bridge Design Specifications, 4th Edition with California Amendments

Crash TestingNCHRP Report 350 (six test levels)

NEW! AASHTO Manual for Assessing Safety Hardware (MASH)

a.) Test Level 2

(TL-2)

Local and collector roads with favorable site conditions

Roadways with speeds up to 45 mph

Crash test with a small car and pickup truck at 45 mph

b.) Test Level 4

(TL-4)

High speed highways, freeways, expressways and Interstate

Roadways with vehicle speeds greater than 45 mph

Crash test with small car/pickup at 62 mph, medium size truck at 50 mph

Bridge Rails“See-Through” Alternatives

Applications:

•California Coastal Commission/ Local Coastal Program

•Context Sensitive Solutions (CSS)

•Bridge or Roadside


Desired Features:

•Visibility: minimize impairment of views from the bridge; aesthetically pleasing view of the bridge from public areas

•Rail Height: consistent with minimum required height for anticipated users (vehicle, bicycle and/or pedestrians)

•Aesthetics: enhance visual appeal by applying color, texture and other treatments


Metal Bridge Rails Concrete BarriersTL-4 TL-4

California ST-10 Concrete Barrier Type 80

California ST-20S Concrete Barrier Type 90

California ST-30

California ST-70

TL-2 TL-2California ST-40 Concrete Barrier Type 80SW

California ST 10 Bridge Rail

• Description: See through 2-bar curb-mounted steel bridge rail• Test Level: TL-4 • Standard Plans: B11-68, B11-69, B11-70• Height: 33” above bridge deck (27” steel rail plus 6” curb)• Comments: Requires additional rail for use as a pedestrian/bicycle rail

to increase height to a minimum of 42”.• Successfully used on past projects in the Coastal Zone.


• California ST-10 Bridge Rail with Bicycle Rail offset 15” from rail face

• California ST-10 Bridge Rail separated from the Pedestrian Handrail by a Walkway.

California ST-20S Bridge Rail

• Description: See through 5-bar curb-mounted steel bridge rail • Test Level: TL-4 • Bridge Standard Detail Sheets: see website• Height: 54” above bridge deck (48” steel rail plus 6” curb) • Comments: The rail is 12” higher than the minimum required

Bicycle Rail or Pedestrian Rail height of 42”.

California ST-20S Bridge Rail

Van Duzen River Bridge

Humboldt County

California ST-30 Bridge Rail

• Description: See through 2-bar curb-mounted steel bridge rail• Test Level: TL-4 • Standard Plans: Standard Plan B11-65• Height: 32” above bridge deck (25” steel rail plus 7” curb)• Comments: Requires additional rail for use as a

pedestrian/bicycle rail to increase height to a minimum of 42”.


South Fork Dibble Creek, Tehama County


• Description: See through 4-bar curb-mounted steel bridge rail • Test Level: TL-4• Bridge Standard Detail Sheets: see website• Height: 46.5” above bridge deck (40.5” steel rail plus 6” curb) • Comments: Rail is similar to California ST-20S Bridge rail except that

the top 7.5” high handrail has been removed. This rail is 4.5” higher than the minimum required Bicycle Rail or Pedestrian Rail height of 42”.


• Description: See through 4-bar sidewalk mounted steel bridge rail. • Test Level: TL-2 • Standard Plans: Standard Plans B11-66, B11-67 • Height: 42”above sidewalk. 8” high sidewalk/curb next to traffic (9” at

edge of deck).• Constraints: Cannot be used on bridge decks with vehicular traffic

signed for greater than 45 mph.


Renderings of California ST-40

Concrete Barrier Type 80

• Description: See through concrete barrier.• Test Level: TL-4 • Standard Plans: Standard Plans B11-60, B11-61, XS Sheet website• Height: 32” above bridge deck.• Comments: Requires addition of steel rail on top to increase height to

a minimum of 42” as well as modification of the clear opening for use as a pedestrian/bicycle rail.

Successfully used on past projects in the Coastal Zone.


• Photo of Concrete Barrier Type 80 - Modified with Architectural Treatment and with Bicycle Rail Offset 15” from Rail Face.


Sheffield Drive Bridge

Santa Barbara County


• Description: Concrete barrier with see through steel rail on top.• Test Level 4: TL-4 • Bridge Standard Detail Sheets: See website.• Height: 32” above bridge deck.• Comments: In order to also be used as a pedestrian/bicycle rail,

requires additional steel rail mounted at least 15” behind the rail face to increase height to a minimum of 42” as well as modification to reduce the clear openings.

Concrete Barrier Type 80SW

• Description: See through concrete barrier with a raised sidewalk.• Test Level: TL-2 • Standard Plans: Standard Plans B11-62, B11-63, B11-64• Height: 42” above sidewalk (32” See-through concrete barrier plus

10” of handrail). 8” high sidewalk/curb next to traffic (9” at edge of deck).

• Comments: Cannot be used on bridge decks with high speed vehicular traffic (greater than 45 mph).


Canal Street BridgeEl Dorado County

See-Through Bridge RailsCost Comparison

Bridge Rail Estimated

Cost/LF

Cost/Cost 732

Concrete Barrier Type 732 $88/LF 1.00

California ST-10 $204/LF 2.32

California ST-20S $297/LF 3.37

California ST-30 ---- ----



Concrete Barrier Type 80 $264/LF 3.00

Concrete Barrier Type 90 ---- ----


$313/LF 3.55


Summary

Metal Bridge Rails Concrete BarriersTL-4 TL-4

California ST-10 (H=33”) +, ^ Conc Barrier Type 80 (H= 32”) +, ^,#

California ST-20S (H= 54”) ++ Conc Barrier Type 90 (H= 32”) ++,^, #

California ST-30 (H=32”) +,^

California ST-70 (H= 46.5”) ++

TL-2 TL-2California ST-40 (H=42”) + Conc Barrier Type 80SW (H=42”) +, #

Notes:

+Standard Plans ++ Bridge Standard Detail Sheet

^ Requires additional rail for use as a pedestrian/bike rail to increase height to 42”

# Can apply architectural treatment

“See-Through” Bridge RailsFrequently Asked Questions….

1. What is the recommended minimum rail height for bridge bicycle rails? AASHTO says 42” but the Highway Design Manual says 54”.

• AASHTO lowered the minimum required rail height for bicyclists from 54” to 42” at their 2006 annual meeting.

• The Caltrans initiated a bicycle rail height study that concluded that a 42” minimum bicycle rail offset 15” from the face of the vehicular rail is sufficient for most situations.

• The Department issued a memorandum on November 26, 2008 lowering the height from 54” to 42” for most applications.

• Caltrans recommends a minimum height of 48” where a combination of high bicycle speeds and high crash impact angles are anticipated. See AASHTO Bridge Design Specifications for more details


2. What is the Type Selection process for an aesthetic bridge rail?

• The Project Development Team (PDT) shall evaluate the need for a CSS rail early in the project.

• A Conceptual Bridge Rail Plan needs to be reviewed/approved by the PDT and used in the environmental process.

• During the Design phase, need to ensure that the aesthetic bridge rail meets all project requirements as well as structural/crash test requirements.

• Projects in the coastal zone may require special consideration.


3. Are there any special considerations where barriers are placed on a structure with a high super-elevation?

• All bridge barriers are to remain vertical regardless of the super-elevation.

• If the super-elevation is 6% or greater, a higher bridge rail is required on the outside of the curve. Issues regarding super-elevation should be discussed as early in the design process as possible.


4. Can see-through rails developed for bridges be used in other applications?

• The see-through rails were developed for bridge applications, but can be modified for other uses by special design.

a) For example, a see-through rail can be used on the roadside by mounting the rail on a reinforced concrete trench footing or on a trench footing on CIDH piles.

b) See-through rails can also be used with earth retaining systems, however the design of the earth retaining system needs to consider vehicular impact loads.


5. Are there any limitations on the type of aesthetic treatment that can be applied to these bridge rails?

• Any color can be added as architectural treatment.

• There are limitations on the architectural texture that can be applied to the surface of rails. Drawings and reports detailing the texture relief limits on rail can be found at the Caltrans Landscape Architecture website:

http://www.dot.ca.gov/hq/LandArch/barrier_aesthetics/index.htm

http://www.dot.ca.gov/hq/LandArch/barrier_aesthetics/index.htm


6. Can these rails be used to support other roadway appendages, such as sign structures or lighting standards?

• In high speed locations (posted speeds over 45 mph), rails can support roadway appendages without any further crash testing, if the appendage is offset 15” behind the front face of the rail. This applies to bicycle rail, sign posts, sign structures, light standards, etc.

• In low speed locations (posted speed of 45 mph or less) rails without a sidewalk may have roadway appendages if the appendage is offset 8” behind the front face of rail. Rails with a sidewalk in low speed locations do not require an offset for appendages, but special attachment details may apply depending on the rail type.

• Contact Caltrans/DES when there is a need for any roadway appendage to be attached to top or backside of rail.


Bridge Standard Detail Sheets (aka XS Sheets) website:

http://www.dot.ca.gov/hq/esc/techpubs/manual/bridgemanuals/bridge-standard-detail-sheets/




“See-Through” Bridge RailsNext Steps



August, 2011

Guidance•DRAFT Design Information Bulletin (DIB), Bridge Rail Development, Design and Selection Guidelines

•Update Highway Design Manual

•Bridge Rails and Barriers: A Reference Guide for Transportation Projects in the Coastal Zone

Crash Testing/ Development of additional alternatives




August, 2011

Questions????

“see-through” bridge rails shannon post/ greg kaderabek caltrans division of engineering...

Documents

bridge rail slide

bridge rail california

bridge standard

bridge deck

bridge rails design

s bridge rail description

rail face california

steel rail