PGSuper  3.0
Precast-prestressed Girder Bridges
Shear Design

Parameter settings on this tab control the outcome of the automated shear design algorithm for this girder type.

NOTE: there are also settings on the Transverse Reinforcement tab that affect design outcome.

Available Bar Sizes/Legs and Spacing

Use the grid to input the bar size / number of legs combinations that the design algorithm will choose in the order given. The algorithm will select the first bar/legs combination that provides adequate shear capacity for the analyses in question. Hence, always order values in the grid from the smallest to largest Av.

Item Description
Order # The preference order number
Bar Size Size of the transverse bar
# of Bars (Legs) Number of vertical transverse bars cross the shear failure plane
[Insert Row] Insert a bar/legs combination into the grid
[Delete Row] Removes the selected bars/legs combination from the grid
Bar Spacing Values Available to the Design Algorithm Enter a list of comma, or space-delimited stirrup spacing to be used by the design algorithm for laying out stirrup zones along the girder. The list must contain at least one value and is ordered from the smallest to largest spacing.

Note that the relative spacing in this list must abide to the layout rules defined in the next section.

Rules for Layout of Transverse Reinforcement Zones

Transverse reinforcement zones are defined from the ends of the girder toward the middle. These rules describe the possible changes in stirrup zone layout geometry and allowable bar spacing between adjacent zones.

Item Description
Maximum change in bar spacing between zones This length measurement defines the maximum change in stirrup spacing between two adjacent zones. For example, if the maximum change value is 6", the algorithm cannot change spacing values from 12" to 24" from one zone to the next.
Maximum change in shear capacity between zones This percentage value defines the maximum change in shear capacity (i.e., stirrup area / spacing) between adjacent zones that can be made by the design algorithm.
Minimum zone length These two values together define the minimum length of stirrup zones that can be created by the design algorithm.

Design Control Options

Item Description
Extend primary shear bars into deck for horizontal interface shear capacity Select this check box to extend primary shear bars into the deck to provide horizontal interface shear capacity (LRFD 5.8.4)
Primary shear bars act as confinement reinforcement Select this check box if primary shear stirrups provide confinement capacity (LRFD 5.10.10.2)
When designing for longitudinal reinforcement for shear, increase capacity by: If existing prestressing strands and longitudinal rebar do not provide adequate capacity for longitudinal reinforcement for shear requirements (LRFD 5.8.3.5), the design algorithm will attempt to increase capacity using one of two methods:
  1. Add longitudinal mild steel reinforcement. This will add full-length #5 rebars into the bottom flange of the girder
  2. Add prestressing strands. Prestressing strands will be added using the order defined on the permanent strands tab. This can only be done if a flexural design is being run in addition to shear design and will restart the flexural design algorithm.