Bridge design codes require that each component of a bridge be designed for the traffic load arrangement that produces the most adverse moments, shears, etc.

The majority of structural programs available today require the bridge designer to anticipate the "worst" locations of the traffic load by "moving" a load at a certain increment along the bridge structure. By doing this you hope to hit all critical load locations. This method works fairly well for simple structures, although handling multiple load cases (in some cases hundreds of them) becomes quite cumbersome.

Bridge designers know that to do it right, and to truly comply with the code requirements, means calculating influence lines for each result type at every point along the bridge. You can then easily decide where to place the load. For structures with complex geometry, such as the arch bridge and parking garage ramp shown at right, the amount of work required to calculate all of the influence lines is staggering.

AutoBridge enables the engineer to define lanes and vehicle loads in accordance with local design codes for any STRAP bridge model. The program automatically generates and solves the many vehicular load cases needed to calculate the worst effects everywhere on the bridge. For any result at any location it also gives the influence line, the max-min results and the loading pattern which generated them.

AutoBridge is seamlessly integrated with STRAP, giving the user access to all options for processing and displaying results. Other load types, such as wind and seismic loads, may be defined on the same model and the results may be combined with the envelope generated by AutoBridge. The bridge may then be designed according to local steel and concrete codes.

 Features:

• Lanes
  • Lanes may be curved
  • Multiple lanes of variable widths may be defined
  • The user may create multiple loadings on different lanes (with permutations)
   
• Loads
  • The program contains a library of vehicles according to the following codes: AASHTO, BS5400, TMH7, BD37. The user can also define additional vehicles.
  • The user may define a group of different vehicle types (e.g. of varying lengths) and the program will check, for any location in the model, which vehicle causes the worst effect.
  • The user may define any uniform, vehicle or knife-edge load.
  • The program checks and determines by itself which segments in each lane should be loaded by uniform loading to get the max and min effect for each result type at any point on the bridge.
  • The program automatically decreases the uniform load according to the length of the loaded section, according to the following design codes: AASHTO, BS5400, TMH7, BD37. The user may also define a factor table.
   
• Results
  • The influence lines and the max and min results can be separately requested for each of the result types, including moments, reactions, deflections, etc. The influence line also shows the effect of the adjacent lanes on the element being checked.
  • The user can instantly obtain influence lines for any position on the bridge.
  • Load locations for the worst case effects may be displayed for any location on the bridge.
  • Full tabular and graphic display of results, including envelopes.
     

Next: Found Design

• Design for axial force and biaxial moments (in same load case)
   
• Eccentric column allowed in both directions
   
• "Quick design" of multiple footings
   
• Multiple load cases (up to 25)
   
• Additional loads options :
  self - weight of the footing
  weight of soil above footing
  additional distributed load on top of footing
   
• Limiting uplifting in footings loaded with moments
   
• Automatic design of base dimensions and reinforcement according to Code requirements
   
• Automatic design of height for punching and shear, including sloped upper surface
   
• Automatic design and detailing of reinforcement
   
• User defined dimensions may be checked
   
• Design units may be specified by the user
   
• Graphic output of footing - plan and section - to scale and in color
   
• DXF file of graphic output may be created
  
   

• The reactions for all STRAP load combinations at these nodes (force and moments)
   
• the column dimensions (if possible) from the section of the member attached to the node.

Also available as a stand-alone program - FOUND.

All / several footings:

Single footing:

• Revise parameters for the individual footing.
  
   
• Add, revise or delete load cases.
  
   
• Check any dimensions.

The user has full flexibility in defining the number of the cables and their shape. The program provides him easy to use tools for determining the number of the cables and their location in the cross section of the beam within the range of the allowable stresses.

Losses

The program calculates accurately all the types of the losses including the effect of the stressing of a certain beam on other beams that have been prestressed at an earlier stage. The losses along the time are calculated at time intervals.

Deflections and ultimate moments

For beams the program calculates the exact deflections. For beams and slabs the program calculates the ultimate moments and compares them with the actual moments in the model.

Shear

The program calculates the actual shear and checks it against the allowable shear stresses.

Time points

The user can define a table of time points and assign the posttensioning of certain cables to certain time points and also the effect of certain loads to certain time points.

Construction at stages

For such structures, the user can create few models and combine them by the COMBINE command of STRAP. The posttensioning program enables him to assign certain models that have been defined by the COMBINE command to certain time points. The program will calculate the prestressing stresses for the corresponding model.

Codes

The program is with accordance to the following design codes: EURO CODE, BS 8110, BS 5400, ACI, CSA, AASHTO, IS 466

• A unique feature of STRAP enables you to draw section lines through a group of elements and display diagrams of moments, shear, forces, stresses etc. along or perpendicular to the line. 
• STRAP enables you to extract and assign names to certain parts of the model (e.g. West Wing) and display or print their graphical or tabular results at any stage by referring to these names. 
• In addition to the regular result types, STRAP enables you also to display special results needed for the design stage e.g. reinforcement area in concrete elements and design moments in slabs, accounting also for the Mxy moments.  
• The reactions and the column dimensions can be automatically transferred to the FOUND program for footings design. 
• Design of concrete structures retaining liquids according to BS8007. The module enables the design of the reinforcement so that the crack widths from applied loads are limited to acceptable values (optional module).

See also: Combinations results 

Next: Steel Design