Structures Design Guidelines | Jan 2008
10 - Pedestrian Bridges |

# 10 - Pedestrian Bridges

## 10.1 General (01/07) Added Chapter per TDB C06-07 except that Ramps and ADA information references have been added to the PPM.(01/08) 2008 Jan - added "aluminum" to C. and D.

A. The criteria covers engineered steel and concrete pedestrian bridge superstructures, including proprietary trusses, and the associated substructures, ramps, stairs, etc. crossing over FDOT roadway or placed on FDOT right-of-way.

B. Minor timber or aluminum structures associated with boardwalks, docks or fishing pier projects are not covered by these policies except that the loading shall meet requirements defined herein.

C. Wooden trusses or timber beam structures may not cross over FDOT roadway facilities.

D. Aluminum or Fiber-reinforced polymer (FRP) (i.e. plastic, carbon fiber, or fiberglass) pedestrian bridges are not allowed.

E. Comply with ADA requirements for ramps and railings. See SDG 1.1.6
(ADA on Bridges)

## 10.2 Referenced Standards

Reference Standards are in accordance with Section 8.2 of the PPM (Volume I).

## 10.3 Designer Qualifications

A. All design calculations and design details or any design changes must be signed and sealed by a Professional Engineer licensed in the State of Florida.

B. For FDOT projects, engineering design firms working directly for the FDOT or designing a Contractor initiated proprietary pedestrian bridge span option must be pre-qualified in accordance with Rule 14-75.

C. Engineering firms designing private, permitted bridges crossing FDOT roadway facilities need not be pre-qualified in accordance with Rule 14-75, but must comply with Rule 14-75 for minimum personnel and technical experience.

## 10.4 Design

A. Design all engineered and proprietary pedestrian bridge structures in accordance with the AASHTO LRFD Bridge Design Specifications, the FDOT Plans Preparation Manual, and the FDOT Structures Design Manual.

B. Pedestrian bridges must be:

1.) Fully designed and detailed in the plans.

2.) Non-proprietary generic designs.(See Section 10.19
for contractor options).

3.) Designed for a 75-year design life.

C. The minimum clear width for new FDOT pedestrian bridges is:

1.) On a pedestrian structure - 8 feet.

2.) On a shared use path structure - 12 feet.

3.) If the approach sidewalk or path is wider than these minimums, the clear width of the structure should match the approach width. The desirable clear width should include additional 2-foot wide clear area on each side.

D. Vertical clearance criteria shall be as per the current FDOT PPM Volume I Table 2.10.1. Horizontal clearances shall take into affect future widening plans of the roadway below.

E. Camber DL/LL Deflections – Expand AASHTO LRFD Specification Section 2.5.2.6.2 as follows:

1.) Pedestrian Load.......................................................... | Span/500
2.) Truck Load.................................................................. | Span/500
3.) Cantilever arms due to service pedestrian live load.......... | Cantilever Length/300
4.) Horizontal deflection due to lateral wind load.................. | Span/500
5.) The bridge shall be built to match the plan profile grade after all permanent dead load has been applied.

## 10.5 Loading

A. See AASHTO LRFD Specifications for Load Combinations.

B. See AASHTO LRFD Bridge Design Specifications [3.6.1.6] for pedestrian Live Loading.

C. Design pedestrian/bicycle bridges and ramps for an occasional single maintenance vehicle load whenever access is possible. If not otherwise specified, use the following criteria:

1.) Clear Deck width from 8 ft. to 10 ft. 10,000 lb (AASHTO Standard H-5 Truck.)

2.) Clear deck width greater than 10 ft. 20,000 lb (AASHTO Standard H-10 Truck.)

3.) Do not place an H-Truck live load in combination with pedestrian live load.

D. Modify AASHTO LRFD Bridge Design Specifications Section 3.8.1.2 as follows:

Wind Loads - A wind load of the following intensity shall be applied horizontally at right angles to the longitudinal axis of the structure. The wind load shall be applied to the projected vertical area of all superstructure elements on the leeward truss.

1.) For Trusses and Arches: 75 pounds per square foot (90 pounds per square foot for Broward, Collier, Escambia, Indian River, Martin, Miami/Dade, Monroe, Santa Rosa, St. Lucie and Palm Beach counties )

2.) For Girders and Beams: 50 pounds per square foot (60 pounds per square foot for Broward, Collier, Escambia, Indian River, Martin, Miami/Dade, Monroe, Santa Rosa, St. Lucie and Palm Beach counties.)

3.) For open truss bridges, where wind can readily pass through the trusses, bridges may be designed for a minimum horizontal load of 35 pounds per square foot (42 pounds per square foot for Broward, Collier, Escambia, Indian River, Martin, Miami/Dade, Monroe, Santa Rosa, St. Lucie and Palm Beach counties) on the full vertical projected area of the bridge, as if enclosed.

4.) Submit wind pressures for bridges over 75 feet high or with unusual structural features to FDOT for approval.

5.) For cable stayed pedestrian bridges, see AASHTO LRFD Bridge Design Specifications Section 3.8.1.2. Increase wind pressures for Broward, Collier, Escambia, Indian River, Martin, Miami/Dade, Monroe, Santa Rosa, St. Lucie and Palm Beach counties by 20 percent.

E. During design, evaluate the structure for temporary construction load conditions including checks prior to and during deck casting.

## 10.6 Materials

A. Require that all materials be in compliance with the applicable FDOT Specifications.

B. Careful attention shall be given in selecting combinations of metal components that do not promote dissimilar metals corrosion.

C. Specify ASTM A500 for structural tubing: Minimum thickness shall be 1/4” for primary members and 3/16” for verticals and diagonals.

D. Do not specify weathering steel unless approved by the Department.

E. In the design of Steel HSS (Hollow Structural Section), use a design wall thickness of 0.93 times the nominal wall thickness to ensure safety.

F. Aluminum is allowed only for railing and fence enclosure elements. Isolate aluminum from concrete components at the material interface.

G. Design and detail cast-in-place concrete decks. See SDG 1.4 Table 1.2
for concrete cover requirements.

H. Comply with SDG 1.3
Environmental Classification.

## 10.7 Steel Connections

A. Field welding is not allowed.

B. Welding - Meet the requirements of FDOT Specifications, Section 460.

C. Bolting Criteria:

1.) Require that all structural field connections be made with ASTM A325 Type 1 high-strength bolts with ASTM A563 nuts and ASTM F436 washers.

2.) Design bolted connections per AASHTO, LRFD.

3.) Design slip-critical bolted connections for a Class A surface condition.

4.) Bearing type connections are permitted only for joints subjected to axial compression or on bracing members.

D. Tubular Steel Connections:

1.) Open-ended tubing is not acceptable.

2.) Require that tubular members be capped and fully sealed before field sections are bolted together.

3.) Require that all field splices be shop fit.

4.) Require that all tubes be fully sealed at time of fabrication.,

5.) Specify or show field sections bolted together using splice plates.

6.) Direct Tension Indicators (DTI) are prohibited in bolted connections.

7.) Avoid through bolted field sections where possible. When through bolting is necessary, stiffen the tubular section to ensure the shape of the tubular section is retained after final bolting.

## 10.8 Vibrations

A. The fundamental frequency without live load should be greater than 3.0 hertz (Hz) to avoid the first harmonic. If the fundamental frequency cannot satisfy this limitation, or if the second harmonic is a concern, a dynamic performance evaluation should be made.

B. In lieu of the above requirement, the bridge may be proportioned so that the fundamental frequency is greater than f>2.86 ln (180/W) where “ln” is the natural log and W is the weight (kips) of the supported structure, including dead and live load.

C. Alternatively, the minimum supported structure weight (W) shall be greater than W>180e(-0.35f) where f is the fundamental frequency (Hz).

D. Check vibration frequency under temporary construction conditions.

## 10.9 Fracture Critical Members

A. Require ASTM A709 Charpy V-Notch testing for all structural steel tension members.

B. Require Impact testing requirements as noted below:

1.) Test non-fracture critical tension members in accordance with Table 9 (Zone 1) of ASTM A709 (latest version).

2.) Primary tension chords in a two truss bridge may be considered non-fracture critical due to frame action.

3.) Test fracture critical tension members in accordance with Table 10 of ASTM A709 (latest version).

4.) Cross frames, transverse stiffeners, and bearing stiffeners not having bolted attachments and expansion joints do not need to be tested.

## 10.10 Cable-Stayed Pedestrian Bridges

A. Design stay systems to meet the same durability and protection requirements as FDOT post-tensioning systems for anchors, tendons or P.T. bars. See SDG 4.5
.

B. Design cable-stay structures for stay removal and replacement such that any one stay can be removed.

## 10.11 Painting/Galvanizing

A. Specify Paint systems in accordance with the FDOT Specifications, Section 560 and 975. See SDG 5.12
.

B. Coatings are not required for the interior of tubular components.

C. Consider the suitability of the fabricated component for galvanizing. Hot-dip galvanizing may be used where entire steel components can be galvanized after fabrication and where project specific aesthetic requirements allow.

D. Specify galvanizing in accordance with the FDOT Specifications, Section 962-7.

E. Galvanizers must be on the State Materials Office Approved Materials/Producers list.

F. Welding components together after galvanizing is not acceptable.

## 10.12 Erection

A. Design and detail pedestrian bridge plans to minimize the disruption of traffic during bridge erection.

B. Include a note on the plans that erection over traffic is prohibited.

C. Include a note on the plans that the Contractor’s Specialty Engineer is responsible for designing a falsework system capable of supporting portions of the superstructure during erection.

D. The erection of pedestrian structures will be inspected per FDOT Specifications 460 or 450.

## 10.13 Railings/Enclosures (01/08) 2008 Jan. C.2 Changed "Bicycle railing" to "Special Height Bicycle railing."

A. Design pedestrian railings in accordance with AASHTO LRFD with the exception that the clear opening between elements shall be such that a 4.0-in diameter sphere shall not pass through.

B. Provide ADA compliant handrails as required. Occasional use of the bridge by maintenance or emergency vehicles generally does not warrant the use of a crash tested combination pedestrian / traffic railing.

C. Provide railings options as directed by the District as follows:

1.) 42” Pedestrian/Bicycle railing (minimum).

2.) 54" Special Height Bicycle railing.

3.) Open top fence / railing combination.

4.) Full enclosure fence / railing combination.

5.) Open top cladding / railing combination (glass, steel panel, concrete panel, etc.).

6.) Full enclosure cladding / railing combination.

D. Utilize FDOT standard fence designs or connection details from FDOT Design Standards 810, 811, and 812 where applicable.

## 10.14 Drainage

A. Design and detail drainage systems as required. See SDG 6.6

B. Provide curbs, drains, pipes, or other means to drain the superstructure pedestrian deck. Drainage of the superstructure onto the underneath roadway is not allowed.

C. Conform to ADA requirements for drainage components.

## 10.15 Corrosion Resistant Details

A. Provide designs such that water and debris will quickly dissipate from all surfaces of the structure.

B. See SDG 5.12 Corrosion Protection

## 10.16 Fabricator Requirements

A. Steel Structures

1.) Require that fabricators be qualified in accordance with FDOT Specifications, Section 6-8 and Section 460.

2.) Require that pedestrian bridge fabricators hold a current AISC Quality Certification for Major Steel Bridges except an AISC Quality Certification for Simple Steel Bridge Structure is sufficient for pedestrian bridges consisting of un-spliced rolled beams or if fabricating minor bridge components.

B. Concrete Structures

1.) Require that precasters be qualified in accordance with FDOT Specifications, Section 6-8 and Section 450.

2.) Require that pedestrian bridge precasters be PCI certified.

C. All pedestrian bridges will be fully inspected using FDOT inspection procedures for typical steel and concrete structures.

## 10.17 Lighting/Attachments

A. Design lighting levels per the latest edition of the Illuminating Engineering Society of North America Lighting Handbook (IES). Use the requirements for pedestrian walkways.

B. For tubular structures, design any attachment, including electrical wiring, signs, signals, etc., strapped to the bridge. The tapping of holes into the structural tubular members is not allowed.

C. For wind loads, design lighting attachments as per AASHTO LRFD and the Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals.

## 10.18 Maintenance and Inspection Attachments

A. Inspections will be performed in accordance with the Department’s current procedure and criteria and the FDOT maintenance guidelines.

B. The inspection and maintenance criteria of private permitted bridges for the spans that cross FDOT roadway facilities are the same as for public bridges.

## 10.19 Proprietary Structures

A. Contractor proposed proprietary substitutions must meet the requirements of this Chapter.

B. Include the following plan notes into all pedestrian bridge Contract Documents. Include any project specific restrictions that must be incorporated into any redesigns or substitutions (Tubes – round or square, span/depth relationships, etc.)

“The Contractor may propose an alternative proprietary pedestrian bridge from the generic system presented in the Contract Documents. Any Contractor initiated proprietary pedestrian bridge span option shall meet all of the requirements of Chapter 10 of the Structures Design Guidelines and be in compliance with and constructed in accordance with Section 460. Proprietary pedestrian bridges shall meet all project specific restrictions and all aesthetic requirements of the project”.

“The Contractor shall submit signed and sealed calculations, revised plans and fully detailed shop drawings for the proprietary span option to the Engineer for approval. The Contractor may initiate the alternates described herein without following the VECP process. All costs associated with the Contractor proprietary option shall be borne by the Contractor”.

## 10.20 Permit Structures

A. Only spans crossing FDOT roadway facilities and the supporting piers and foundations will be reviewed by FDOT.

B. Design, fabrication, and erection of non-FDOT structures placed over FDOT roadways or on FDOT right-of-ways will comply with the requirements of this chapter and Chapter 8 [Section 8.7] of the Plans Preparation Manual (Volume I).