FDOT Standard Plans Index 450-450: Series Florida Slab Beams

Design Criteria

Design Criteria AASHTO LRFD Bridge Design Specifications ; Structures Design Guidelines ( SDG ) ; Structures Detailing Manual ( SDM )

Design Assumptions and Limitations

Design Assumptions and Limitations Standard Plans Index 450 - 450 is the lead standard for the 12", 15" and 18" Florida Slab Beams (FSBs) Standard Plan s Indexes 450 - 450 , 450 - 451, 450 - 452 and 450 - 453 , respectively. FSBs are the basis for the Florida Slab Beam Superstructure System. FSBs are designed to act as simple spans under both Dead Load and Live Load.

The abbreviated FSB designation for depth and width is FSB "depth" x "width", e.g. FSB 12 x 48. FSBs must be of the same depth within a given span.

FSBs of different depths may be used in different spans of the same bridge. FSBs vary in width from 4' - 0" to 5' - 0" in 1 - inch increments. For a given bridge or multiple similar bridges on a given project, FSBs should be of the widest constant width possible except where geometric constraints preclude this, e.g.

locations of phase construction joints or significant changes i n cross slope.

Commentary

Commentary: The use of constant width FSBs is recommended when possible for economy of fabrication. The use of the widest width FSBs possible is recommended for efficiency of the pretensioned beam design. The FSB standards are applicable for spans with skewed end conditions less than or equal to 30 degrees.

For spans with skewed end conditions greater than 30 degrees, develop custom FSB designs and details using the Standards as a basis. The skew may be dif ferent at the two ends of a given span. FSBs must be used with a cast - in - place (C - I - P) reinforced concrete topping that extends across the full length and width of the span and integral pockets between each adjacent FSB.

The concrete for the C - I - P topping must include a shrinkage reducing admixture per Specification Section 346 and 924. For design purposes, the C - I - P topping must be a minimum of 6" thick for Short Bridges and a minimum of 6½" thick for Long Bridges (prior to planing). See SDG 4.2 for the definitions of Short and Long Bridges.

A single mat of reinforcing steel consisting of longitudinal #5 bars at 9" centers and transverse #5 bars at 6" centers is required within the C - I - P topping. An additional mat of reinforcing steel is required if the C - I - P topping thickness is greater than 10". Closed #5 bar stirrups with longitudinal #5 bars are required within the pockets at locations matching all Bars 5E extending from the sides of the FSBs.

The C - I - P topping and pockets are considered to act composite with the FSBs under Live Load and Composite Dead Loads. Instructions for Standard Plan s Topic No. 625 - 010 - 003 Index 450 - 450 Series Florida Slab Beams Commentary: The minimum topping thicknesses of 6" for Short Bridges and 6½" for Long Bridges are to be used for design purposes.

These topping thicknesses already include the ½" tolerance for beam camber variability that is shown on Standard Plans Indexes 450 - 199 and 450 - 299. As - constructed topping thicknesses of 5½" for Short Bridges and 6" for Long Bridges (prior to planing) with their associated minimum covers to the top layer of reinforcing are acceptable. Index 458 - 110 Poured Joint with Backer Rod Expansion Joint System is required to seal the expansion joints between adjacent FSB spans.

Either Standard Plans Index 458 - 110 , an armored elastomeric strip seal, a modular joint or a finger joint may be used as necessary between an FSB span and an adjacent span with a different superstructure type. See the

General Notes

General Notes Sheet. Include the following note on the General Notes sheet: C - I - P TOPPING: Thoroughly saturate the top surface of the FSBs with water in accordance with Specification 400 for 12 hours immediately prior to placing the C - I - P topping. Remove standing water prior to placing the C - I - P topping.

Cure the C - I - P topping in accordance with the Specification 400 requirements for bridge decks. Prepare a Superstructure Plan View and Section T hrough Superstructure in accordance with Structures Detailing Manual Chapter 15 and include them in the plans. Label both the coping to coping dimension and the out - to - out dimension as shown in the Detailing Manual Example .

Include cross references to traffic and pedestrian railings and dimensions, reinforcing bar callouts and spacings for raised sidewalks (if present). On the Superstructure Plan View, include language similar to the following in the dimension ing for both the longitudinal and transverse #5 reinforcing bars in the C - I - P topping: Shift as required to clear Bars [insert actual bar mark for #5 closed stirrups here] and FSB Bars 4K. For skewed spans, show the transverse reinforcing bars to be placed parallel to the skew if the skew is less than or equal to 15 degrees.

If the skews are different and/or in Instructions for Standard Plan s Topic No. 625 - 010 - 003 Index 450 - 450 Series Florida Slab Beams opposite directions at opposite ends of a span, the transverse reinforcing bars may be fanned with the maximum spacing not to exceed 6", or may be placed perpendicular to the centerline of the span. If the skew at either end of a span is greater than 15 de grees, show the transverse reinforcing bars to be placed perpendicular to the centerline of the span.

When the transverse reinforcing bars are placed perpendicular to the centerline of the span, include three additional No. 5 bars that extend the full widt h of the bridge placed parallel to the skew at 6 - inch spacings adjacent to each end of the span. Include the following details on the Superstructure or Superstructure Details Sheet(s): • Detail at Begin/End Bridge as shown in Figure 6 if a spread footing or a pile or drilled shaft supported end bent is used.

Complete the detail by deleting either the "End Bent Cap" callout or the "Spread Footing" callout as appropriate and by replacing var iables K1 and K2 with project specific dimensions. Figure 6 Detail at Begin/End Bridge with End Bent or Spread Footing Instructions for Standard Plan s Topic No. 625 - 010 - 003 Index 450 - 450 Series Florida Slab Beams • Detail at Begin/End Bridge as shown in Figure 7 if a GRS abutment is used.

Complete the detail by replacing variables K1 and K2 with project specific dimensions. Figure 7 Detail at Begin/End Bridge with a Spread Footing and GRS Abutment Instructions for Standard Plan s Topic No. 625 - 010 - 003 Index 450 - 450 Series Florida Slab Beams • Detail at Intermediate Bents/Piers as shown in Figure 8 if a pile or drilled shaft supported intermediate bent is used.

Complete the detail by deleting either the "Intermediate Bent Cap" callout or the "Pier Cap" callout as appropriate and by replacing var iables K1 and K2 with project specific dimensions. Figure 8 Detail at Intermediate Bents/Piers • Detail at Pockets, Backer Rod Detail and Notes, and the Section along Centerline Pocket at Span Ends as shown in Figure 9. Complete the Section along Centerline Pocket at Span Ends by deleting either the "End Bent Cap", "Pier Cap" or "Spread Footing" callo uts as appropriate.

Instructions for Standard Plan s Topic No. 625 - 010 - 003 Index 450 - 450 Series Florida Slab Beams Figure 9 Detail at Pockets, Backer Rod Detail and Notes, and Section along Centerline Pocket at Span Ends Instructions for Standard Plan s Topic No. 625 - 010 - 003 Index 450 - 450 Series Florida Slab Beams • Detail at Copings as shown in Figure 10.

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What your plans must show

Plan Content Requirements for this index — the SPI's checklist for designers.

• - P topping thickness along the length and across the width of the span. A significant superelevation transition must be accommodated by varying the grade at which adjacent FSBs are pla ced in combination with varying the C
• - P topping thickness along the length and across the width of each individual FSB, i.e. the way superelevation transition is accommodated on I
• - girder superstructures. Provide a substructure transverse keeper block on the low side of the superstructure for the following two conditions:
• 1. If the superstructure cross slope is greater than or equal to 3% and the cross section is not crowned.
• 2. If the cross section is crowned, the superstructure is constructed in phases and the cross slope of the first phase is greater than or equal to 3%. Provide substructure transverse keeper blocks on both sides of the superstructure if there are significant transverse forces acting on the superstructure that must be resisted, e.g. forces from wave action or water flow. Otherwise, do not use substructure transverse keeper blocks. To minimize horizontal splitting forces, limit the maximum bonded prestress force at the FSB ends from fully bonded strands to the following:
• Instructions for Standard Plan s Topic No. 625
• - 450 Series Florida Slab Beams Index No. FSB Depth Maximum Bonded Prestress Force 450
• - 453 18" 1460 kips Do not apply losses and use the jacking force of all the strands located in the bottom half of the beam when calculating the bonded prestress force. Do not modify the reinforcing in the ends of FSBs without the approval of the State Structures Design Engineer. Permanent traffic and pedestrian railings shown in the Standard Plans may be used as
• - is when their vertical reinforcing steel is required to be embedded 6" into the supporting deck (the C
• - P topping for FSBs). Permanent traffic and pedestrian railings shown in the Standard Plans with vertical reinforcing steel that is required to be embedded more than a 6" into the supporting deck, e.g. Standard Plans Index 521
• - 42 8 , may be used if project specific reinforcement details are provided in the plans. Permanent traffic and pedestrian railings shown in the Standard Plans that utilize post
• - installed anchors may be used only with adhesive bonded anchor bolts. Standard Plans Index 102
• - 110 Temporary Concrete Barriers may be used freestanding with keeper pins or may be bolted down using adhesive bonded anchor bolts only. Provide a raised sidewalk that is integrally reinforced with the C
• - P topping in conjunction with Standard Plans Indexes 521
• Instructions for Standard Plan s Topic No. 625
• - 450 Series Florida Slab Beams Figure 1 Span Length Schematic Plan Establish bearing locations as shown in Figure
• 2. Use an open joint width of 2" in conjunction with Standard Plans Index 458
• - 110 Poured Joint w ith Backer Rod Expansion Joint System unless a larger expansion joint is necessary.
• Instructions for Standard Plan s Topic No. 625
• - 450 Series Florida Slab Beams Figure 2 Bearing Location Schematic Plan Use the following equation and Figure 3 to determine the width and number of FSBs, and the width of the gaps between them, for a given bridge width: W G = [ ( W C + 1" ) √ 1 + Cross Slope 2 ]
• - ( N FSB x W FSB ) ( N FSB
• - 1 ) W G = Uniform width of gaps between FSBs measured along the cross slope at the bottom of the FSBs (¾" ≤ W G ≤ 1½" preferred, 1¾" maximum) [inches] W C = Horizontal dimension between coping lines measured perpendicular to the stationing line; or for horizontally curved spans, measured perpendicular to a line tangent to the stationing line at the centerline of the span [inches] Cross Slope = Average percent cross slope; averaged along the length of the span [ft/ft] N FSB = Total number of FSBs used for a given bridge width W FSB = Width of a single typical FSB; 4'
• - 0", in 1" increments [inches]
• Instructions for Standard Plan s