LECWall 3 - Tilt-up or Precast Concrete Insulated Wall Panel and Column Design Program
The industry standard for concrete insulated "sandwich" wall panel design handles multi-story columns as well. LECWall 3 can analyze prestressed and/or mild reinforced wall panels with zero, partial, or full composite action. Flat, hollow-core and stemmed configurations are supported. Complete handling analysis is also included. A free 15 day trial version is available.
- 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%, or use the new Partial Composite Calculator.
- Five manufacturer plug-in modules are included, with more on the way: Icon-X, Sigma DG, HK-Ties, Thermomass and Thin-Wall.
- Hollow-core and double tee wall panels supported.
- Multiple openings or notches accommodated 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 and graphs. Graphical printouts
- Choice of English or Metric units (Canadian Code is supported).
- A free trial version is available. Email the filled Evaluation License Agreement and we will send it to you. Note that the trial period expires after 15 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 screen captures of the program
LECWall 3 Methodology
- Section Properties
- Openings and Reveals
- Strand Development Length
- Prestress Losses
- Handling Analysis
- P-Delta Analysis
- Calculation of Bow
- I-Effective and I-Cracked
- Ultimate Capacity Interaction Curves
Section Properties:
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.
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 MenuStrand Development Length:
The standard ACI method is used. 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.
Prestress Losses:
The PCI Design Handbook is used for calculation of initial and final prestress losses in the member (Section 5.8).
Back to Methodology MenuHandling Analysis:
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.
1.0 times the theoretical cracking moment can also be displayed, per ACI 318, Section 11.8.1.1c. 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 the PCI Insulated Wall Panel Design Standard, 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 requirement only applies at the location along the length of the panel where the onset of cracking is expected, not along the entire length.
Back to Methodology MenuP-Delta Analysis:
The program performs an iterative second-order analysis of the member under each of the fourteen specified load cases. The PCI 8th Edition Handbook procedure (Section 5.10.3.1) 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. Cracked I is taken as 0.35Ig, per ACI 318 Table 6.6.3.1.1a. Alternately, an I-effective is used for the Beam-Spring analysis, per ACI 318-19 24.2.3.9. There is also an option to use a pre-cracked section, as is common with slender tilt-up panels. I-cracked is calculated using ACI 318 Eqn 11.8.3.1c.
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 a built-In frame analysis module. 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 can be set to be a first floor, at grade connection. 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. Use the Spring Constant option to model the deformation of the tie connections.
Back to Methodology MenuCalculation 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. Bow due to non-concentric prestress force is included. Compression members are usually stressed so as to minimize bow. 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.
I-Effective and I-Cracked:
For single-wythe panels and dual wythe panels using the ISBT method or manually input percent composite, I-cracked is used when fr exceeds 7.5 Sqrt F'c. I-cracked is set as 0.35 * I-gross, per ACI 318 Table 6.6.3.1.1a.
The Beam-Spring method calculates I-cracked for each wythe separately, using ACI 318 Eqn 11.8.3.1c. I-effective for mild-reinforced panels is calculated using ACI 318-19 Table 24.2.3.5. I-effective for prestressed panels is calculated using ACI 318-19 24.2.3.9. The Capacity screen has an option for analyzing a pre-cracked section (Beam-Spring method only). This is useful for the P-Delta analysis of mild-reinforced, slender, load-bearing tilt-up panels, or precast panels that have a risk of cracking prior to erection. When checked, I-cracked is substituted for the middle 2/3 of the panel, starting at 1/6 times the length from each end.
Incremental cracked section analysis: The Beam-Spring method uses an incremental approach to determine I-effective for each wythe at 100 points along the member length. Multiple frame analyses are performed, with the loading increased from onset of cracking until full load is applied. I-effective for each point is adjusted after each run to account for the stress (and stiffness) redistribution that occurs as the load increases and the cracked area spreads along the member. This provides a more realistic model of the stiffness variations present along the panel length for each load case. For example, when a tie-back connection is present, cracking at the tie-back could create a plastic hinge, altering moments and stresses.
Back to Methodology MenuUltimate 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. 5.10.1. A straight line is plotted from the transition point of PhiPn = 0.10f'cAg, where Phi = 0.7, to PhiPn =0, where Phi = .9. Alternately, if the Use Canadian material resistance factors option is checked, the program will use factors specified by the Canadian code, CSA A23.3. 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 11.8.1.1c. 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 the PCI Insulated Wall Panel Design Standard, 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 requirement only applies at the location along the length of the panel where the onset of cracking is expected, not along the entire length.
For insulated wall panels, if percent composite is input manually, partial composite capacity is estimated by first computing the capacity at 0% composite and again at 100% composite, then finding a ratio based on the percent composite specified. The 0% and 100% capacity curves are plotted along with the partially composite curve for comparison purposes.
If the ISBT or Beam-Spring method is selected, percent of ultimate capacity is found by summing the connector resistances from the closest member end to the point selected. Maximum connector slip/strain is assumed at the end connectors. The percentage of tension reinforcement that can be transferred between wythes by the wythe connectors is then found by using a bi-linear connector strain distribution at each point along the panel. This then becomes the % composite for Ultimate value.
Back to Methodology Menu