FAQs

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 spWall 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 Sections 2.4.5. and 2.7.2. 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 (I_cr/I_g). 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 I_cr/I_g 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 "Cracking Coefficient and Effective Flexural Stiffness of Concrete Walls" technical article, in Section 13 of "Reinforced Concrete Tilt-Up Wall Panel with Opening Analysis and Design (ACI 318-14 - ACI 551)" design example, and Section 2.3.4. in spWall Manual.

I have two layers of reinforcement and the program tells me A_sx and A_sy 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: A_sx/2; Reinforcement area for each layer in Y direction: A_sy/2 (in other words the reported A_s should be divided in half for each layer). More information about Element Reinforcement can be found in Section 2.3.5.2. in spWall Manual.

How can the program help with design in accordance with ACI 318-11 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. A detailed comparison between hand solution and analysis results of spWall engineering software program from StructurePoint can be found in "Reinforced Concrete Tilt-Up Wall Panel Analysis and Design (ACI 318-14 - ACI 551)" design example.

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 Section 2.7. 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 (ACI 318-14 - 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?

More information about supported design codes and other program features can be found in Section 1.1. in spWall Manual.

Why can't I see all nodes and elements in results tables and Reporter?

The Ranges feature, in results tables and reporter, allows you to explore the results for a selected range of plates, stiffeners, and/or nodes. By default, these ranges are set from 1 to 100 for nodes and plates, and from 1 to 12 for stiffeners. To view plate, stiffener, and nodal results for the entire model, simply check the ALL checkbox. More information about Ranges feature can be found in Sections 3.3. and 3.4. in spWall Manual.

What units are supported?

English and Metric. More information about spWall features can be found in Section 1.1. in spWall Manual.

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

You can use the Display Options in the Left Panel, of Solve or Results Scopes, to show node and element numbers. More information about Contours and Diagrams Display Options can be found in Sections 7.2.1.4. and 7.2.2.4. in spWall manual, respectively.

What is the relationship between objects, physical structural members, and finite elements?

In spWall, reference is often made to objects, members, and elements. Objects represent the physical structural members in the model. Elements, on the other hand, refer to the finite elements used internally by spWall to generate the stiffness matrices. In many cases, objects and physical members will have a one-to-one correspondence, and it is these objects that the user draws in the spWall interface. Objects are intended to be an accurate representation of the physical members. Users typically need not concern themselves with the meshing of these objects into the elements required for the mathematical, or analysis finite element model. For example, a single area object can model an entire plate, regardless of the number of spans and variety of loads. With spWall, both model creation, as well as the reporting of results, is achieved at the object level. More information about Physical Modeling Terminology can be found in Section 4.1.1. in spWall Manual.

What M_xx and M_yy denote for?

Unlike in beams and columns, the traditional plate and shell theory convention is that M_xx denotes the moment along (not about) the X-axis and M_yy denotes the moment along the Y-axis. More information about Plate Internal Forces can be found in Sections 7.1.5.2., 7.1.4.3., and 2.4.1. in spWall manual.

What are the directions of rebar A_sx and A_sy?

Asx refers to the rebar in X direction (parallel to X axis). Asy refers to the rebar in Y direction (parallel to Y axis). More information about the Required Area of Steel can be found in Section 2.4.2. in spWall manual.

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 Element Design Forces can be found in Section 2.4.1. in spWall Manual.

For one curtain reinforcement, what are BH and BV on the Plate Design Criteria dialog box?

Looking at the positive X direction:

1) BH (Back Curtain Horizontal) is the distance from the left surface of the wall to the center line of the reinforcing bars that are positioned in X direction.

2) BV (Back Curtain Vertical) is the distance from the left surface of the wall to the center line of the reinforcing bars that are positioned in Y direction.

More information about Plate Design Criteria can be found in Section 5.2.3.2. in spWall Manual.

For two curtain reinforcement, what are BH, BV, FH, and FV on the Plate Design Criteria dialog box?

Looking at the positive X direction:

1) BH (Back Curtain Horizontal) is the distance from the left surface of the wall to the center line of the closest reinforcing bars that are positioned in X direction.

2) BV (Back Curtain Vertical) is the distance from the left surface of the wall to the center line of the closest reinforcing bars that are positioned in Y direction.

3) FH (Front Curtain Horizontal) is the distance from the right surface of the wall to the center line of the closest reinforcing bars that are positioned in X direction.

4) FV (Front Curtain Vertical) is the distance from the left surface of the wall to the center line of the closest reinforcing bars that are positioned in Y direction.

More information about Plate Design Criteria can be found in Section 5.2.3.2. in spWall Manual.

How can I export my results to a file?

You can export results using the Reporter Module in 5 different format options:

1) WORD: produces a Microsoft Word file with .docx extension.

2) PDF: produces an Adobe Acrobat file with .pdf extension.

3) TEXT: produces a Text file with .txt extension.

4) EXCEL: produces a Microsoft Excel file with .xlsx extension.

5) CSV: produces a Comma Separated file with .csv extension.

More information about the Reporter Module can be found in Section 3.4. 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 A_s (A_s,n+1) is greatly differs from the estimated value of A_s (A_s,n), the analysis should be performed again with new values of A_s and cracking coefficient until A_s,n ≈ A_s,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 318-14 - ACI 551)" design example and Section 2.3.4. 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, liquid-containing 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", also known as "Alternative Method for Out-of-Plane Slender Wall Analysis", 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.