BRIDGE DESIGNER II (BD2 version 4)
is a versatile Bridge Design software package, which addresses the varied requirements of Pre-stressed Concrete Bridge Analysis and Design.

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BD2v4 uses basic matrix structural analysis formulation combined with time-dependent material properties, to carry out a Time Simulation of Bridge Designs under construction. During this process, all stress conditions are checked at every construction step as well as in service.

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Displacement Method The current release includes a standard plane-frame, two-dimensional displacement method. The field of unknowns is the vertical plane (coordinates x and y, and rotation r). Various stiffness components may be inserted in the global stiffness matrix, such as support stiffness and restraint stiffness (boundary conditions).

Specific Concrete Segmental Bridge Design Features:

• Time Dependent Material Properties – BD2 v 4 assembles and re-assembles the structure stiffness at every time step of the construction schedule and automatically accounts for concrete creep and shrinkage as well as steel relaxation in order to compute time-dependent deflections and stress redistributions.
• Unlimited number of components (nodes, segments, post-tensioning tendons, spans, construction phases, etc…) – BD2 generates and analyzes bridge models without memory constraints or limitations on model size.
• 3D Post-Tensioning Geometry with automatic initial and long term PT losses (Tendon stress, de-stress and grout) – For optimal Post-Tensioning Layout by quickly evaluating primary vs. secondary effects and factor accordingly in service.
• Non-Linear Cable-Stay Analysis (Stay stress, de-stress, re-stress) – BD2 tackles complex cable-stay bridge construction sequences. Stressing, de-stressing or re-stressing stays taking into account geometric non-linearity due to stay sags as well as girder and pylon deflections or differential temperature changes in the stays.
• User defined boundary conditions and Construction Phases
• Temperature Effects (Linear and Non-Linear Gradients) – All Design codes require evaluation of stresses generated by temperature changes in girders.  BD2 has the ability to automatically create an apply differential linear or non-linear thermal gradients.  The corrections stresses generated (self-equilibrating stresses) are available for combinations in the Service Module.
• Service Loads – Stress Combinations – The BD2 Service Module allows complete re-definition of live loads and traffic/moving loads and rules of application and combinations based on any service code.  The default service code is AASHTO LRFD (Load and Resistance Factor Design).
• Autocad (DWG), Microstation (DGN), and RISA-3D CAD file exports

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Time Simulation of Construction Sequence The construction of a structure may be simulated in great details. Concrete segments may be poured in-place or pre-cast and assembled. Tendons and stays may be stressed or de-stressed. External loads (concentrated or distributed) may be applied at any time, anywhere on the structure, moved on various sections, or removed. The construction time steps account for the correct concrete age throughout the construction, as well as proper evaluation of time-dependent strains.

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The analysis performed by Bridge Designer is a two-dimensional displacement method based on the assumption of linear elasticity and the condition of static equilibrium. Under any loading condition, a structure may be broken down into elementary pieces that behave in accordance with the Theory of Elasticity. In addition in the range of small displacements and assuming that the material remains elastic, this behavior is linear, and the Principle of Superposition of the deformations and stresses applies

Long Term Redistributions
Time dependent effects are evaluated during and after construction. Creep is handled as an internal load-case to simulate the effect of restrained long term strains. Shrinkage is also applied as an internal load, although it is independent of the stress level in the material

Composite Sections
In composite structures such as “Spliced-Girders” (a construction methodology that is becoming a standard in the US to accommodate longer span lengths with precast pre-stressed beams), evaluating stress corrections due to differential creep in shrinkage in the beam and slab has become important during the design stage.  Again, this redistribution is time-dependent and varies greatly depending on the static equilibrium during construction stages.  BD2 has no limitations on the configuration and number of construction stages and performs an exact stress computation of these effects.

Service Module
The new Bridge Designer Service Module was developed to check bridge structures under different service codes. It provides a flexible user defined live load generator, as well as a service code definition language (macro instructions). This user-driven environment lets you use the US AASHTO code as well as redefine service codes as complex as the British Standards 5400 or the LRFD code for the United States.