PRESTRESSED GIRDER BRIDGES

BSE Bridge Structural Engineering Software

BSE SOFTWARE
PRESTRESSED GIRDER BRIDGES

Adding the BSE PRESTRESSED GIRDER BRIDGES application allows the user to perform the analysis and design of beams pre-stressed by pre-tension.

The program performs the verification of pre-stressed beams with a minimum user effort. Once the geometric data and the materials are defined, the program takes care of generating the bridge model automatically.

Through a set of simple and appropriate forms, the analysis and design of precast concrete bridge girder with pre-tension is carried automatically by the BSE BRIDGE program.

TECHNICAL SPECIFICATIONS

•Supported standard codes are CAN/CSA-S6-88 and CAN/CSA-S6-06.
•Standard AASHTO, NEBT, NBPS and CPCI sections and custom precast sections.
•Automatic and custom transverse strands layouts.
•Straight strands with one or two raised points.
•Standard and custom moving load envelopes for truck and/or lane loads.
•Pre tension losses calculated with specified code or through a step-by-step method.
•Design of precast girders for multiple span bridges with composite slab action near piles.
•Design of stirrups along girders and design of steel reinforcement at supports.
•Accounts for thermal effects.
•Accounts for the secondary effects from creep and shrinkage.
•Deflection of girder according to time.
•The results obtained for the highway live load can be combined with other types of loads applied to a structure (dead weight, additional dead loads and live loads) to obtain a global solution as well as the corresponding envelopes.

•Custom precast section predefined shapes include the narrow top flange, the wide top flange and the bulb tee sections.
•Transverse strands layouts for any standard or custom precast sections.
•All standard sections have built-in strands layout that can be overridden.
•The transverse strands layouts must be defined for custom precast sections.
•The transverse strands layout is defined for the maximum number of strands in the section.
•When the actual number of strands used is lower than the number defined in the layout, each row of strands is filled completely before filling the next row.
•When a standard section is selected, the default built-in layout for this section is automatically fetched to ease simple modifications.
•A custom layout does not overwrite the default layout, this default layout is still be available.
•The maximum number of straight and inclined strands for standard sections are specified.

•Spacing of strands : the center to center spacing between the strands.
•Inclined strands : Number of strands per row, maximum number of rows, minimum distance to side.
•Straight strands : Minimum distance to side.
•Number of straight strands per row : a maximum of 12 rows of straight strands is allowed.

PARAMETERS TO DEFINED A
TRANSVERSE STRAND LAYOUT

•The moving standard loads as well as all custom moving loads available are:
– CL-625 (CAN/CSA S6-06)
– CL-625-ONT (CAN/CSA S6-06)
– QS660 (Quebec)
– MTQ-340 (Quebec)
– CS600 (CAN/CSA-S6-88)
– OHBDC (Ontario)
– Egyptian Loads
– AASHTO (USA)
•The lateral distribution coefficients wizard calculates the lateral distribution coefficients with respect to the CAN/CSA S6-06 requirements

•The concrete slab is cast in place during the construction of the bridge.
•The reinforcing steel in the slab and in the stiffener beams at supports ensure the continuity of the deck at interior supports for the additional dead loads, as well as for the live loads.
•The required dimensions of the concrete slab are defined by the user.

SLAB
PARAMETERS

•The stiffener beams are added between the longitudinal beams.
•They enhance the lateral stability of the bridge and allow for a better distribution of forces on the width of the bridge.
•These stiffener beams are not designed by the program, their dimensions and material properties are required solely for determining their self weight.
•The number of stiffener beams between the supports can vary from one span to another.

•The stirrups diameter and the yield stress of the stirrups material are defined.
•The spacing of the stirrups required to resist the shear forces is calculated .
•The stirrup spacing calculated by the program accounts for anchoring zones.
•The horizontal shear between the beam and the slab will be taken by the stirrups which will be extended in the slab.

STIRRUP
PARAMETERS

•Thermal gradients must be considered in the design of a multi-span bridge where there is continuity at the supports.
•Thermal gradients can generate non-negligible forces in the structure.
•Thermal gradient: This value indicates the maximum temperature difference between the top of the slab and the bottom of the beam.
•The program assumes a linear temperature gradient on the depth of the composite beam.

•The calculation of pre-stress losses is an important part of the calculation of pre-stressed beams.
•The losses of pre-stress during the life of the bridge beginning with the transfer of the pre-stress to the concrete can be over 20% of the initial strand tension.


•Calculation method : Two calculation methods of the losses are supported. The first is the method proposed by the selected design code (CAN/CSA-S6-88 or CAN/CSA-S6-06). The second method is a step-by-step approach which determines the losses over time.
•Relative humidity : The average annual relative humidity in the surrounding of the bridge. This value has an influence on shrinkage and creep.


•Area of ordinary steel bars (As) : The area of ordinary steel bars influences the losses caused by shrinkage in the step-by-step approach. When the As is not equal to zero, the step-by-step approach tends to predict lower losses caused by shrinkage.
•Concrete cure method: A normal concrete cure is made at room temperature. An accelerated steam cure is a thermal treatment of the concrete allowing to accelerate its hardening cycle.

LOSSES
PARAMETERS

•The production of precast pre-stressed beams is made in several steps. T4 time is the reference time and is always equal to zero. Thus, the times T1 to T3 times are negative and the times T5 to T7 times are positive.
•Tensioning of strands (T1) :The pre-stressing steel is put in tension and is retained by jacks and other mechanisms of steel retention. At this step, no concrete is present. The losses by relaxation starts at this time.
•Concrete casting (T2) : The concrete is cast in place and the concrete cure begins. This data is considered in the calculation of concrete age for the calculation of creep losses.

End of cure, beginning of shrinkage (T3) : When the cure is stopped, the surrounding humidity drop provokes the start of the shrinkage of concrete. The shrinkage occurring between time T3 and time T4 will not induce pre-stressing losses.


•Transfer of pre-stress (reference time) (T4): At this step, the concrete is sufficiently resistant to support the pre-stressing forces. The pre-stressing strands are released and transfer the forces to the concrete beam. Due to the arrangement of the strands in the beam, the beam tends to camber under the effect of the pre-stressing forces. From this time, the losses caused by creep and remaining shrinkage begins.
Casting of slab and stiffener beams (T5): At this time, the loads induced by the self weight of the slab and the stiffener beams are held by the pre-stressed beam only. Once hardened, the slab acts in a composite manner with the beam to support the additional loads added later to the structure. Once the concrete slab has hardened, the program assumes the continuity at the interior supports which affects the effect of additional loads.


•Add. dead loads 1 (edges, sidewalks and curbs) (T6): The time at which the additional loads are applied to the structure has an effect on the losses. The intensity of these loads are specified for each span.
Add. dead loads 1 (asphalt) (T7): The time at which the additional loads are applied to the structure has an effect on the losses. The asphalt is considered as a dead load which has a load factor larger than other dead loads. It has thus been separated from other additional dead loads. The intensity of these loads are specified for each span.

All span data that vary from one span to another are defined by the user. The following data is to be defined: Geometry, loads, beam material, strands and supports.

SPAN DATA

•The summary of the input data contains the following tables: General, Strands, Moving Load, Slab, Stiffener Beams, Stirrups, Thermal Gradients and Losses.
•The summary of the output results includes : unfactored envelopes, factored envelopes, losses results, stresses of sections, ultimate flexural strength, continuity effects, stirrups design and deflection results.

CONTACT

  • SAFI Quality Software, Inc.
  • CANADA CORPORATE OFFICE
    3393 Sainte-Foy Road, Quebec City
    QC, G1X1S7
    CAN
  • [email protected]
  • (USA&CAN) 1 800.810.9454
  • + 1 418.654.9454
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