LECWall - Precast Concrete Wall and Column Design Program
This software has become a standard in the industry for concrete sandwich wall panel design.
- Complete handling analysis with two or four point pick and user specified form and impact factors.
- Partial composite action between wythes, user specified from 0% to 100%.
- Hollow-core and double tee wall panels supported.
- Multiple openings or notches accomodated at any location.
- Multiple horizontal or vertical reveals can be specified (Section properties are calculated at 100 points.)
- P-Delta slenderness and temperature effects combined with wind, earth pressure and gravity load analysis under service conditions or at ultimate strength.
- Loads can be applied at any point. Up to 10 floors/connections are allowed.
- Cracked section analysis
- Automatic prestress loss calculations
- Will handle wall panels or tied columns with any combination of mild reinforcing and/or prestressing strand.
- Easy to use graphical interface with diagrams, graphs and on-line help screens. Graphical printouts
- Choice of English or Metric units.
- A free trial version is available. Sign and fax or mail back the Evaluation License Agreement and we will send it to you. Note that the trial period expires after 30 days and that the software has to be erased if a license is not purchased. The trial version functions identically to the licensed version.
View some screen captures of the program in action
- Section Properties
- Openings and Reveals
- Strand Development Length
- Prestress Losses
- Handling Analysis
- P-Delta Analysis
- Calculation of Bow
- Ultimate Capacity Interaction Curves
Section properties of multi-wythe composite members are calculated using the modulus of elasticity of the main structural wythe (as designated by the user in the Section Dimensions window). If the modulus of elasticity of the secondary wythe differs from the main wythe, the secondary wythe area and moment of inertia is multiplied by the modular ratio between the two wythes. See the % Composite section for a description of how partially composite properties are determined. Section properties are calculated at 100th points along the member.Back to Methodology Menu
Openings and Reveals:
Section properties are automatically modified at opening and reveal locations. Openings are cut all the way through one or both wythes, while reveals are depressions in either the front or back face of the member. To ensure accurate section properties, openings should not overlap with other openings or reveals, and reveals should not overlap with other reveals or openings. The program will not check for overlaps. That needs to be done manually by examining the plan views provided in the Opening and Reveal design windows (be sure to update the views first by clicking the Update button).
Any strands, bars or WWF that cross through openings are cut and development lengths are adjusted automatically. Click on the Section button in the Capacity Check window to verify the strand, bar or WWF areas at 100th points. The bar or stand areas are reduced accordingly if the reinforcing is not fully developed at the section in question.Back to Methodology Menu
Strand Development Length:
The calculated development length can be altered by using a multiplier, if desired. To do this, click on Setup, select Defaults and change the values at the bottom of the screen accordingly. We recommend a value of 1.0 at ends and 2.0 at openings, to account for the differing strains near the opening.Back to Methodology Menu
The PCI 7th Edition Handbook is used for calculation of initial and final prestress losses in the member (Section 5.7).Back to Methodology Menu
Vertical lift lines with two cranes or a spreader beam are assumed to be used for stripping members from the bed. Note: If inclined lines are used for lifting, you need to manually calculate the additional moment generated by the angle of the inclined lines and account for it in the member design.
The center of gravity of the panel is listed near the top of the Handling window. Use the C.G. to assist in specifying the lift point locations to provide a more equal distribution of lift forces, if desired.
Potential panel tilt is also displayed. Tilt can occur when rollers are used for lifting to equalize the left and right reactions An ultimate capacity check for handling forces is also provided. Statically calculated unfactored moments are first multiplied by the user-specified handling (or impact) factor, then multiplied again by an ultimate load factor. This ultimate load factor is initially set to 1.4, but can be changed by clicking on the Setup menu and selecting Defaults. Strain compatibility is used to determine the member's ultimate capacity in the horizontal position.
1.2 times the theoretical cracking moment can also be displayed, per ACI 318, section 18.8.2. By keeping the member capacity greater than 1.2MCr, additional capacity will be present after cracking, which should provide a "warning" deflection before failure occurs. According to ACI, if member flexural strength is at least twice the applied factored load, then the ultimate capacity can be less than 1.2MCr. Note that this criteria only applies at the point where the member is likely to crack first, not along the entire length. Also, the ACI code provision is meant for in-place loadings, not temporary handling forces. Therefore, it is up to the engineer's discretion as to whether this criteria needs to be applied for handling loads.Back to Methodology Menu
The program does an iterative second-order analysis of the member under each of the six specified load cases. The PCI 7th Edition Handbook procedure (Section 5.8.5) is used to calculate bow and P-Delta forces. The member is considered to be pinned at both ends for the analysis (a conservative assumption when rigid floor ties are used).
If stresses exceed the modulus of rupture (user specified as the "Cracking stress coefficient") at any point along the member, the section is assumed to be cracked and the analysis is repeated using cracked section properties. Gross EI is used to compute deflection up to cracking load. Additional deflection beyond the cracking load is computed using the cracked EI. Click on the Show Stresses button to check for cracking anywhere along the length for a specific load case. As a general rule, cracking should be avoided under service load cases for prestressed members.
Forces and deflections due to eccentric gravity loads, earth pressure and wind are calculated using the slope-deflection method. The force in the optional floor tie is the total of effects from the eccentric gravity load moment, earth pressure, wind forces and restraint of predicted thermal bow. The floor connection is considered to be a first floor, at grade connection. Wind loads are applied above the floor connection only (a conservative assumption), therefore it would not be valid to use the floor connection for an upper floor (above grade). Floor tie forces can be somewhat unpredictable (they have been known to pull out occasionally). Therefore, a ductile design for the floor ties is recommended to avoid a brittle failure if over-stressed.Back to Methodology Menu
Calculation of Bow:
Member bow is calculated based on differential temperature strains, wind load deflection and member bow due to applied gravity and earth pressure loads. Note: Bow due to non-concentric prestress force is not included. Compression members are usually stressed so as to minimize bow and such bow is hard to predict accurately in real life situations due to other factors such as humidity, storage methods, etc.
The Bow & Temperature section of the Capacity form allows manual input of the predicted initial bow, based on the designer's experience. If non-concentric stressing is used, this value should be adjusted to account for the predicted bow.Back to Methodology Menu
Ultimate Capacity Interaction Curves:
The member ultimate capacity is calculated at a point along the member length selected by the engineer. The strain compatibility method is used to plot the points along the interaction curves. The equations used are from the PCI 7th Ed. Handbook, Fig. 5.9.1. A straight line is plotted from the transition point of PhiPn = 0.10f'cAg, where Phi = 0.7, to PhiPn =0, where Phi = .9. For composite members (with two wythes), only one wythe is used for the compression block.
1.0 times the theoretical cracking moment can also be displayed, per ACI 318, Section 188.8.131.52. It shows up as a small red circle on the Interaction Curve diagram. By keeping the member capacity greater than 1.0MCr, additional capacity will be present after cracking, which should provide a "warning" deflection before failure occurs. According to ACI, if member flexural strength is at least twice the applied factored load, then the ultimate capacity can be less than 1.0MCr. Note that this criteria only applies at the point where the member is likely to crack first, not along the entire length.
Partially composite capacity is found by first computing the capacity at 0% composite and again at 100% composite, then finding a ratio based on the percent composite specified (see % Composite). The 0% and 100% capacity curves are plotted along with the partially composite curve for comparison purposes.Back to Methodology Menu