LARSA: Post-Tensioning with 3D Tendons

Tendons are modeled as three-dimensional curves and take into account the time-dependent properties of their materials, including creep, shrinkage, and relaxation.

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Tendons Paths

Tendons in LARSA 4D take any arbitrary path in three dimensions, whether they be internal or external. The path is determined through control points at which a location and curvature type are specified. The path of tendons between control points are autmatically computed as straight lines or second/third-order curves, depending on the curvature type.

Curvature is defined using angle of inclination from the members that it passes through, or using a radius of curvature in one or two planes. The positions of control points are given as relative to the members they are in, from the centerline of the members or based on the member's extents. Curvature and offsets can give tendons three-dimensional paths.

Tendons are presented in a 3D view that is updated in real time so that its geometry can be visually verified. Members are displayed with their actual shapes and dimensions.

Side View of a Tendon Passing Through a Girder

Tendon Properties

Tendon properties include the number of strands and material type, the wobble and curvature frictional losses, and the anchor set. Based on peak stress limits and a proposed jacking force, the applied jacking force and resulting elongations are automatically computed.

Short-Term Losses

Short-term prestress losses due to friction and anchorage slip are immediately calculated while entering tendon geometry. Anchor set and the forces along the tendon are quickly verifiable numerically and in a force versus distance graph.

Long-Term Losses

Long-term prestress losses include relaxation, elastic shortening, creep, shrinkage, and superimposed loads. CEPFIP-78 and 90 are supported, using preset and user-provided material curves. See Staged Construction Analysis for more information on time-dependent material effects and cumulative/incremental results reporting.

Staged Construction Analysis

Tendon stressing is applied during the construction of a structure with the use of Staged Construction Analysis, allowing results from before and after stressing each tendon to be analyzed just in one run.

Creep, steel relaxation, superimposed loads, and other PT losses are computed and affect the LARSA 4D tendon.

Reports

Tendon force reports and graphs are available at any stage and these are used to track the effect of tendons.