Design Criteria
Project Information
Input | Description |
---|---|
Project | Project name |
Location | Location of the project |
Date | Date printed on the report (defaults to current date) |
Client | Name of the client |
Designer | Name of the designer |
Job Number | Job number for the project |
Design Number | Design number for the design |
Spec | Let the user select the given specification. Options are ACI 318-19 and ACI 318-14. |
Description | Long form description for the project. Shift+Enter adds a new line. |
Material Properties
Concrete
Input | Description |
---|---|
f’c | Final compressive strength of the wall concrete (often referred to as the 28-day strength). |
f’ci | 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). |
wc | Density of the concrete used in the wall. |
Ec | Modulus of elasticity of the wall concrete at final. This value will be calculated and updated when f’c or the unit weight of the beam are changed. |
Eci | Modulus of elasticity at time of release of the prestress in the casting yard, or at time of stripping of members without prestressing. This value will be calculated and updated when f’ci or unit weight are changed. |
Type | Wall concrete type can be designated as normalweight, sand-lightweight, or all lightweight. |
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.
Rebar
Input | Description |
---|---|
fy | Yield strength of the rebar. |
Es | Modulus of elasticity of the rebar. |
Stress Strain Curve
The mild stress strain curve assumes linear elastic behavior up until yield. At that point the stress always returns the yield stress. Strain hardening is not accounted for and rupture strain is not checked.
Strand
Input | Description |
---|---|
fpu | Ultimate tensile strength of prestressing steel. |
Ep | Modulus of elasticity of prestressed reinforcement. |
Stress Strain Curve
The prestress stress strain curve uses the equations found in the PCI Design Handbook 8th Edition Design Aid 15.2.3. Note that in these equations, the coefficients found in the equation are solved for to account for the user defined material properties. The yield stress in the strand is assumed to be 90% of the ultimate stress.
Prestress Losses
Input | Description |
---|---|
Method | Losses can be user defined, calculated using the lump sum method present in the PCI Design Handbook, or calculated using the time dependent method in the PCI Journal. |
Humidity | Relative humidity (percent). |
Include LL Regain | Indicate whether to include the effects of live load in your losses. |
Time at… | Release: Time when release happens. Used in the loss calculation for transfer. Erection: Time when erection happens. Used in the loss calculation for erection and construction. |
For more information on how prestress losses are calculated, see the prestress losses page.
Load Combinations
Load combinations can be enabled and disabled by using the include check box. Auto select load combinations will turn on only the combinations which match your load input’s load types.
Strength Combinations
Import default strength and service combinations from the currently selected specification. You need at least one strength combination to run the analysis.
Service Combinations
Import default strength and service combinations from the currently selected specification. You need at least one strength combination to run the analysis.
Analysis Options
Flexure Options
Header | Description |
---|---|
Method | Whitney Stress Block: Use an approximate volume of the concrete compression zone known as the Whitney stress block to calculate the compression force. Stress-Strain Integration: Integrate the area under a concrete stress strain curve to calculate the compression force. Eriksson Wall uses the concrete stress-strain curve contained in Collins/Mitchell. |
Resistance Factors
Header | Description |
---|---|
Tension | Strength reduction factor for tension controlled flexure. You can define separate reduction factors for use within the transfer length and past the transfer length. An option exists for fully developed and strand that is transferring. |
Compression | Strength reduction factor for compression controlled flexure. |
Shear | Strength reduction factor for shear. |
Development Multipliers
Header | Description |
---|---|
Strand | Normal: This multiplier is applied to the development length of prestressing strand, except for debonded and cut strand (see below). Debonded: This multiplier is applied to debonded prestressing strand only. Cut: This multiplier is applied to cut prestressing only (at openings). |
Mild | This multiplier is applied to all mild reinforcement. |
Shear Options
Shear Depth, d
Header | Description |
---|---|
Reinforcement CG | By using the centroid of the reinforcement, you are considering the distribution and position of the reinforcing bars within the column cross-section. This approach provides a more accurate estimation of the effective depth, especially when dealing with irregular or non-uniform reinforcement arrangements. |
CG of Tension Force | Considering the centroid of tension force allows for a more accurate determination of the effective depth, as it takes into account the distribution and position of the tension reinforcement, which directly influences the transfer of forces within the column. |
0.8 h | Simplified Method (for columns without transverse reinforcement): The effective depth is taken as the overall depth of the column reduced by a factor of 0.8. Mathematically, it can be expressed as D = 0.8h, where D is the effective depth and h is the overall depth of the column. |
Largest d | The largest effective depth (D value) |
In Place Stress
Header | Description |
---|---|
Modulus of Rupture | Factor multiplied by the square root of the concrete strength and used for calculating the cracking stress |
Allowable Compression | Factor multiplied by final concrete strength and used for calculating final compressive stress limit. |
Handling Stress Limits
Header | Description |
---|---|
Tension | Factor multiplied by the square root of the initial concrete strength and used for calculating initial tensile stress limit. |
Compression | Factor multiplied by initial concrete strength and used for calculating initial compressive stress limit. |
Axial Capacity Options
Header | Description |
---|---|
Use span’s average properties for buckling load | When computing buckling, the average section properties for the span will be used. |
Deflection Limits
Header | Description |
---|---|
Total deflection limit: L / | Sets the limit for deflection multipliers for both total and live load deflections. The deflection limit is always L, as defined above, divided by the inputted value. |
Structural Analysis
Header | Description |
---|---|
Slenderness Effects | The user can select from P-Delta, Moment Magnification, or None. See the Engineering Theory for a discussion of these analysis procedures. |
Cracking Behavior | No Cracking: This option assumes no cracking occurs during the analysis. Assume Cracked: Selecting this option assumes that cracking has occurred. Crack at Rupture: Opting for this mode triggers a stress check to determine if the design exceeds 7.5 sqrt (f’c). |
Cracking Method | The user can select from the ACI Table 6.6.3.1.1(b) method or the Robert F. Mast’s procedure from the PCI Journal. |
Effective Length Factor, k | Effective length factor k will be used when computing the slenderness limit and the buckling load. |
Slenderness limit, kl/r | Slenderness limit will be used to check if slenderness effects can be ignored. This input will only be visible when Slenderness Effects is set to ‘None’. |
βds method
| Determines if beta d sway should be computed by the analysis or user defined. |
βdns method | Determines if beta d non-sway should be computed by the analysis or user defined. |
Development Options
Header | Description |
---|---|
Ktr | Value to fine tune development length calculations. |
Bar Confinement Provided | The bar confinement input is used for computing both the development length of hooked bars in tension and headed bars in tension. This determines if development lengths should be increased through the use of the confining reinforcement factor and the parallel tie reinforcement factor respectively. |
Load Patterning
If checked, all live loads will be patterns. See the live load patterning page for more information.