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In this block, you enter all information that sets the base pile concrete properties. The inputs for this section are:
Header | Description | ||
|---|---|---|---|
Strength at Transfer, fci | Concrete compressive strength at time of release of the prestress in the casting yard, or at time of stripping of members without prestressing. The release strength cannot exceed the final compressive strength. This is used for all stripping and handling analysis. It may also be used for erection (user input). | ||
28-Day Strength, fc | Final compressive strength of the pile concrete. | ||
Stripping Strength | The strength required for the pile to withstand the stresses it will experience during stripping.
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Unit Weight, wc | Density of the concrete used in the pile. |
Ultimate Compressive Strain, εcu | Concrete ultimate compressive strain. |
Stress Stain Curve
The concrete stress strain curve comes from Collins, Michael P. and Mitchell, Denis, Prestressed Concrete Structures. This curve is used anytime the stress strain curve needs to be evaluated for the concrete, which can happen for flexure capacity.
Strand Properties
Input | Description |
|---|---|
Elastic Modulus, Eps | Modulus of elasticity of prestressed reinforcement. |
Ultimate Strength, fpu | Ultimate tensile strength of prestressing steel. |
Stress Strain Curve
The prestress stress strain curve uses a modified power formula which can be found in the PCI Journal, Devalapura, R. K., and Tadros, M. K., "Stress-Strain Modeling of 270 ksi Low-Relaxation Prestressing Strands". This equation is calibrated to be used for both 270 ksi and 300 ksi strands.
Mild Properties
Input | Description | ||
|---|---|---|---|
Elastic Modulus, Es | Modulus of elasticity of the rebar / wire. | ||
Yield Strength, fy | Yield strength of the rebar / wire.
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Prestress Loss Computation
Depending on which of the section types are selected, the input content will change.
Input | Description |
|---|---|
Loss | Loss may either be calculated using the equations from AASHTO LRFD Article 5.9.3.3, or may be user defined percentages. |
At Release | Initial loss percentage as a function of the jacking stress of the strands. |
At Final | Total loss percentage as a function of the jacking stress of the strands. |
Strand Type | Specifies if the strand is of type low-relaxation or stress-relieved. |
Humidity | Relative humidity (percent). |