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FAQs


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What is the difference between spWall and pcaWall?

pcaWall, also formerly known as PCA Wall and PCA TILT, was renamed spWall to better relate and support the registered trade name of the publisher, StructurePoint, formerly the PCA's Engineering Software Group.

Does this program consider in-plane and out-of-plane shear?

In-plane and out-of-plane shear is calculated by spWall and for solid walls it is compared with the shear strength provided by the concrete. More information about this topic can be found in Section 2.14 in spWall Manual.

How does spWall perform a stability check?

Second-order analysis is implemented by spWall during analysis to account for the increased deflections due to PΔ effects. This is an alternative to the moment magnification method permitted in the ACI 318 where the secondary-to-primary moment ratio 1.4 was chosen as the upper limit of 1.33 ratio which is equivalent to the maximum stability coefficient θ (0.25). This limit was set based on literature that showed that at this limit, the PΔ effects will eventually introduce singularities into the solution to the equations of equilibrium, indicating physical structural instability. Finite Element Analysis (FEA) used by spWall allows the user to detect any stability concerns with a model and the analysis is terminated automatically by singularities in the matrix analysis (equations of equilibrium). This indicates that the analysis cannot continue and the wall stability must be reexamined. Where a successful analysis is completed, spWall does not perform any further stability checks. The user can compare manually the second-order moment effects to ensure that they meet the relevant ACI 318 stability provisions.

What are cracking coefficients in spWall input?

The user-specified cracking coefficients are reduction factors that are applied to the gross moment of inertia to obtain cracking moment of inertia (Icr/Ig). The exact value of the cracking coefficient must be calculated by the user in an iterative manner after the initial value is used to run the model for the first time. Then, using an equation such as equations in section 6.6.3.1.1 of ACI 318-14, you may calculate the Icr/Ig of the wall at the critical section and then enter the corresponding cracking coefficient into spWall. You may then run the program using this new cracking coefficient and repeat the process until the value of the cracking coefficient converges. More information about this topic can be found in "Effective Flexural Stiffness for Cracked Moment of Inertia of Concrete Walls" technical article, in Section 13 of "Reinforced Concrete Tilt-Up Wall Panel with Opening Analysis and Design (ACI 551)" design example, and Section 2.7 in spWall Manual.

I have two layers of reinforcement and the program tells me Asx and Asy after design. What is the area of rebar in each of the layers in X and Y direction, respectively?

Reinforcement area for each layer in X direction: Asx/2; Reinforcement area for each layer in Y direction: Asy/2 (in other words the reported As should be divided in half for each layer).

How can the program help with design in accordance with ACI Chapter 14 (Chapter 11 in 318-14)?

spWall is a Finite Element Method for the structural modeling and analysis of slender and non-slender reinforced concrete walls subject to static loads and provide internal forces for each element. In addition, however, it also calculates and graphs internal forces for each horizontal section along the entire height of the wall to support calculations by empirical methods.

Which code procedure is used by spWall?

Walls can be designed using simplified methods such as the empirical design method and alternative method provided in ACI 318 and CSA A23.3 standards. Such methods are limited to specific wall geometry, loading, and support conditions. Walls that do not meet these limitations are required to be designed as compression members and slenderness effects in them can be accounted for by performing second-order analysis. This general approach is implemented in spWall to allow for a wider range of wall configurations and applications. The Code Provisions that spWall considers are given in the Appendix A.1 of spWall Manual. The Code provisions outside the scope of spWall (i.e. reinforcement spacing limits etc.) require to be checked by the engineer. More information about this topic can be found in "Commentary on Multi-Story Tilt-Up Panel Design Using ACI 551.2R-15" technical article.

What method does this program use?

Finite Element Method with Kirchoff thin plate theory. More information about spWall method of solution can be found in Chapter 2 in spWall Manual.

Which design codes does this program support?

For information on supported design codes please visit spWall features.

I checked Show Node Numbers and Show Element Numbers, but I still cannot see the numbers on grid view. Why?

You don't have any finite elements (concrete). Please assign thickness to grid cells in the grid view first to create some finite elements.

Using version 2.0, I get error message "Application Error: floating-point error: overflow" when I was trying to view contours and results. What should I do?

Please upgrade to version 3.0 or higher.

What units are supported?

English and Metric. More information about spWall features can be found in Section 1.2 in spWall Manual.

How can I show node, element or stiffener numbers on my grid view?

Select menu View | Preferences. Check Show Node Numbers or Show Element Numbers or Show Stiffener Numbers. More information about customizing display settings can be found in Section 4.24.3 in spWall Manual.

What is the relationship between grid lines and finite elements?

A grid line cell (rectangular empty space surrounded by grid line) is a potential finite element. Assigning a thickness to a grid cell turns it into a finite element. More information about this topic can be found in Sections 2.3 and 2.4 in spWall Manual.

What Mxx and Myy denote for?

Unlike in beams and columns, the traditional plate and shell theory convention is that Mxx denotes the moment along (not about) the X-axis and Myy denotes the moment along the Y-axis.

What are the directions of rebar Asx and Asy?

Asx refers to the rebar in X direction (parallel to X axis). Asy refers to the rebar in Y direction (parallel to Y axis).

Does this program support in-plane (X-Y wall plane) forces?

Yes. The plate element used in spWall combines the membrane (in plane) and bending (out of plane) actions. More information about this topic can be found in Section 2.5 in spWall Manual.

In version 2.0, for one curtain reinforcement, what are the X-left and Y-left on the Design Criteria dialog box?

Looking at the positive X direction, X-left is the distance from the left surface of the wall to the center line of the reinforcing bars that are positioned in X direction. Y-left is the distance from the left surface of the wall to the center line of the reinforcing bars that are positioned in Y direction.

In version 2.0, for two curtain reinforcement, what are the X and Y on the Design Criteria dialog box?

The two curtains are assumed to be symmetric to the center plane of the wall. The X value is the distance from the center line of the reinforcing bars in X direction to the closest wall surface. The Y value is the distance from the center line of the reinforcing bars in Y direction to the closest wall surface.

It seems that my contours are wrong and they do not match the text results. Why?

Please upgrade to version 3.0 or higher.

Version 2.0 freezes when designing stiffeners. What should I do?

Please upgrade to version 3.0 or higher.

How can I export my results to a file?

Select menu File | Print Results. Select Output to File rather than Output to Printer. Type in a path and file name for the output file (i.e. C:\MyResults\Wall_1.out). Check the results you would like to output. Press the Print button. The saved file is a plane text file that can be opened and edited by any word processing software (i.e. Wordpad). More information about this topic can be found in Section 4.7 in spWall Manual.

How to optimize reinforcement and cracking coefficient for tilt-up wall design?

Run the first model in spWall using the initial cracking coefficient. After analysis and design, if the computed value of As (As,n+1) is greatly differs from the estimated value of As (As,n), the analysis should be performed again with new values of As and cracking coefficient until As,n ≈ As,n+1. More information about this topic can be found in Section 13 of "Reinforced Concrete Tilt-Up Wall Panel with Opening Analysis and Design (ACI 551)" design example, and Section 2.7 in spWall Manual.

What type of walls spWall can analyze and design? What kind of structural elements can be analyzed and designed using spWall?

The following are examples for structural members that have been analyzed and designed over decades by spWall users: reinforced concrete shear walls, precast concrete bearing wall panels, reinforced concrete one-story tilt-up wall panels (with and without openings), reinforced concrete multi-story tilt-up wall panels (with and without openings), Insulating Concrete Forms (ICF) walls, concrete tank walls, reinforced concrete cantilever retaining walls, reinforced concrete deep beams, and reinforced concrete corbels and brackets. More information about spWall applications can be found in StructurePoint Case Studies Page and StructurePoint Design Examples Page.

Can I analyze and design tilt-up wall panels using spWall?

Yes, spWall uses Finite Element Method (FEM) which is a valid method for the analysis and design of reinforced concrete tilt-up wall panels particularly useful for multi-story walls with variable thicknesses, openings, and other features that limit the use of the "alternative design of slender walls" provisions in ACI 318 and ACI 551. Using FEM requires critical understanding of the relationship between the actual behavior of the structure and the numerical simulation since this method is an approximate numerical method. FEM is based on several assumptions and the engineer has a great deal of decisions to make while setting up the model and applying loads and boundary conditions. The results obtained from FEM models should be verified to confirm their suitability for design and detailing of reinforced concrete tilt-up wall panels. More information about this topic can be found in StructurePoint Tilt-Up Wall Panels Page.

Can I analyze and design deep beams using spWall? Why spWall is being used in the analysis and design of deep beams?

spWall uses Finite Element Method (FEM) which is a valid method for analyzing reinforced concrete deep beams, particularly useful for irregular beams and walls with variable thicknesses, openings, and other features that limit the use of Strut-and-Tie Method (STM) or significantly complicate the STM truss and calculations. Using FEM requires critical understanding of the relationship between the actual behavior of the structure and the numerical simulation since this method is an approximate numerical method. FEM is based on several assumptions and the engineer has a great deal of decisions to make while setting up the model and applying loads and boundary conditions. The results obtained from FEM models should be verified to confirm their suitability for design and detailing of reinforced concrete deep beams. More information about this topic can be found in "Design of Deep Beam (Transfer Girder) Using Strut-and-Tie Model (ACI 318-11)" design example.