StructurePoint - spWall Features

spWall User Interface

Start Screen

Main Window

Tables Window

Reporter Window

Print/Export Window

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Analysis & Design

Analysis Methods

Finite Element Method (FEM) of Analysis

The finite element method is used in spWall for analysis of walls. During analysis, spWall converts the object-based model into a finite element model. The user defines the mesh used in the analysis by inputting maximum allowed mesh size and maximum allowed aspect ratio. Additional meshing is automatically introduced at plate boundaries, stiffeners, and nodes with assigned properties such as restraints and point loads.

The member nodal incidences are internally computed by the program. All Nodes and members are numbered from left to right (in the positive X-direction) and from bottom to top (in the positive Y-direction).

Plate Element

The rectangular plate finite element has four nodes, one at each corner. Each node has six degrees of freedom (D_x, D_y, D_y, R_x, R_y, R_z). The rotation, R_z, is referred to as the drilling rotation. The plate element combines the membrane (in-plane) and bending (out-of-plane) actions.

Stiffener Element

Stiffener elements can be used to model beams or columns that are embedded in the wall to increase its structural capacity, e.g. lintels, pilasters, and boundary elements of shear walls. Wall piers that are required to be designed as columns can also be modeled using stiffeners.

The stiffener element used in the program has two nodes, one at each end. Each node has six degrees of freedom (D_x, D_y, D_y, R_x, R_y, R_z).

Design Methods

Flexural Design

Flexural design is performed based on the code provisions of ACI 318 and CSA A23.3. The required area of steel is calculated by trial and error. The program will try to find the least amount of A_s, between the minimum and maximum values specified by the user, which satisfies the strength requirements of all ultimate load combinations. If a value for A_s cannot be found, the program reports design failure.

Plate Element

For plate elements, it is required to calculate the area of steel in the X and in the Y directions. In both directions, the area of steel should be enough to satisfy the strength requirements under sets of extreme design forces for each ultimate load combinations.

Stiffener Element

For stiffener element, the area of steel A_s is calculated such that the strength requirements at both end nodes are satisfied for all ultimate load combinations. The design of stiffener elements has two modes: biaxial and uniaxial modes.

The biaxial mode is applied when the flange width is equal to zero. In this case, the area of steel is calculated due to P_u, M_uy, and M_uz. When the flange width is specified, the neutral axis is forced to be along the local y axis. In this case, the area of steel is calculated due to P_u and M_uy.

Wall Shear Strength

The program can calculate in-plane and out-of-plane shear strength provided by concrete of the wall horizontal cross-sections at each grid level. The calculated strength is then compared at each section to shear forces calculated from the applied loads. The option to calculate and check wall shear strength can be activated in the solver options only if the wall is solid (i.e. has no openings) and ACI code is selected.

Shear Design of Stiffener Elements

Shear design is performed based on the provisions of ACI 318 and the simplified method of CSA A23.3. For stiffener element, web reinforcement for shear and torsion A_v/S and longitudinal torsion reinforcement (A_l) are calculated such that the strength requirements at both end nodes are satisfied for all ultimate load combinations. The design of stiffener element has two modes: Biaxial and Uniaxial modes.

Additional Reinforcement for Stiffeners Due to Shear and Torsion

Procedure for calculating additional reinforcement due to shear and torsion based on CSA A23.3-04 standard. Proportioning of longitudinal reinforcement for sections subjected to combined shear and torsion in flexural regions is based on the requirement that the resistance of the longitudinal reinforcement has to be greater or equal to the axial force that can be developed in this reinforcement.

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Results Output

Graphical Output

Contours

Contour views are used to facilitate the graphical examination of the results by the user. Contour views show the results in three distinct sections, namely, Envelope, Service, and Ultimate.

Service Displacement - Envelope

This graphical view displays the contour envelopes for the maximum positive (+ve) and maximum negative (-ve) displacements (D_x, D_y, and D_z). Displacement envelopes are calculated from the results of the service load combinations. Displacements are shown in the directions of the global axes.

Plate Reinforcement - Envelope

This graphical view displays the contour envelopes for the required areas of steel for flexure in the X directions (A_sx) and the Y direction (A_sy). Half of the displayed value applies to each curtain in models with two curtain layout.

Displacement - Service & Ultimate

This graphical view displays the displacements (D_x, D_y, D_z, and D_xyz) contours for individual service or ultimate load combinations. Displacements are shown in the directions of the global axes. D_xyz displacements contour shows displacements in all 3 directions (i.e. D_x, D_y, and D_z) in the same contour. Thus, providing a holistic accurate depiction of the actual structure deflected shape.

Plate Internal Forces - Ultimate

This graphical view displays the in-plane forces (N_xx, N_yy, N_xy), the bending moments (M_xx, M_yy), and the torsional moment (M_xy) contours for individual ultimate load combinations. Forces and moments are shown in the directions of the global axes.

Diagrams

Diagram views are used to facilitate the graphical examination of the results by the user. Diagram views show the ultimate level results in three distinct sections, namely, Stiffener Internal Forces, Wall Cross-Sectional Forces, and Wall Concrete Shear Strength.

Stiffener Internal Forces

This graphical view displays the internal forces (N_x, V_y, and V_z), the internal bending moments (M_y and M_z) and the torsional moment (T_x) diagrams for individual ultimate load combinations. Forces and moments are shown in the directions of the local axes of the stiffener element.

Wall Cross-Sectional Forces

This graphical view displays the cross-sectional forces (N_uy, V_ux, and V_uz) and moments (M_ux, M_uy, and M_uz) diagrams for individual ultimate load combinations. Forces and moments are shown in the directions of global axes.

Wall Concrete Shear Strength

This graphical view displays the In-Plane and Out-of-Plane Wall Concrete Shear Strength. This portion of results is only available for solid walls designed in accordance with the ACI codes and when the user selects the option to check concrete shear strength.

Tabular Output

The Tabular output can be found both in the Tables Module and the Reporter Module. The Tables Module may be utilized to view and export the model output at any model development stage. The Reporter Module may be utilized to create, export and print customized reports when the design is finalized. Both modules have the same output sections. The differences being that of the Reporter Module contains the cover & contents, and screenshots sections. The Tables Module contains the Solver Messages section. The tables may be fully or partially output for all or for only selected nodes and elements.

Tables Module

Reporter Module

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Advanced Features

Second Order Analysis

spWall can perform second-order analysis in which the effect of in-plane forces are taken into account on the out-of-plane deflections. If second order analysis is requested (the default setting), a complete analysis cycle is done for each load combination. In each cycle, the basic stiffeness terms of plate elements are modified to account for the effect of membrane forces. For stiffener elements, the basic stiffness matrix is modified to account for the effect of axial forces.

Reactions

spWall reports the restraint and Nodal Spring reactions for individual service load and ultimate load combinations for nodes with specified restraints or nodal springs. Nodal translational reactions F_x, F_y, and F_z and rotational reactions M_x, M_y, and M_z are output. Positive translational reactions are in the direction of the positive axes and positive moment reactions are determined using the right-hand rule. The program also reports sum of forces and moments (with respect to wall center of gravity) for applied loads and reactions.

Stiffener Element

Stiffener elements can be used to model beams or columns that are embedded in the wall to increase its structural capacity, e.g. lintels, pilasters, and boundary elements of shear walls. Wall piers that are required to be designed as columns can also be modeled using stiffeners. Additionally, isolated stiffener elements placed outside of the wall can model rigid frame structures attached to the wall. The program will calculate internal forced in the stiffener elements and calculate the area of reinforcement required for axial action combined with biaxial bending as well as shear and torsion.

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Modeling with Templates

Utilizing Templates is a quick and simple option for new models in spWall. The user can select from a set of pre-defined templates and edit their properties for simple and quick model generation.

Each template focuses on a particular structural shape with a specific loading pattern. The user can edit the geometric dimensions of the shape, applied loads, boundary conditions, and material properties. Other shape specific options may also be available for some templates.

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Reinforced Concrete Tilt-Up Wall Panels Analysis and Design

Tilt-up is a form of construction with increasing popularity owing to its flexibility and economics. Tilt-up concrete is essentially a precast concrete that is site cast instead of traditional factory cast concrete members.

The construction of tilt-up walls involves pouring the walls horizontally on the building's floor slab at the job site. A crane hoists the panels into a place where steel braces temporarily secure the panels until workers can weld permanent fasteners into the panel's joints, footing, and roofline.

Reinforced Concrete Tilt-Up Wall Panels

Tilt-Up Wall Structural Analysis

The design guide for tilt-up concrete panels, ACI 551, states that tilt-up concrete walls can be analyzed using the provisions of ACI 318 - Alternative Analysis (Design) Method. Most walls, and especially slender walls, are widely evaluated using this method. The method is applicable when the conditions summarized below are met:

The cross section shall be constant over the height of the wall
The wall can be designed as simply supported
Maximum moments and deflections occurring at midspan
The wall must be axially loaded
The wall must be subjected to an out-of-plane uniform lateral load
The wall shall be tension-controlled
The reinforcement shall provide design strength greater than cracking strength

ACI 318 provides the alternative design method as a simple and accurate option for analysis and design of simple walls meeting the method conditions. ACI 551 allows the use of this method for some cases even though some of the method limitations are not satisfied as long as the results obtained are still within acceptable ranges. However, some walls with complex geometries (multi-span continuous walls with the presence of openings) bring a lot of challenges accompanied with the use of the alternative analysis (design) method.

To understand the wall behavior and adequately address strength and stability requirement, other methods such as finite element analysis, utilized in spWall, can be used. Many other issues arise with panels not meeting the method limitations (continuous and cantilevered walls, variable thickness and width, wall with openings, non-standard boundary conditions, walls with high compressive loads, in-plane lateral loads, non-standard concentrated load position from attachments of piping, racking etc., concentrated out of plane loads).

Tilt-up Wall Panel Analysis and Design Using spWall

spWall uses the Finite Element Method for the structural modeling, analysis, and design of slender and non-slender reinforced concrete walls (including tilt-up walls) subjected to static loading conditions. The wall is idealized as a mesh of rectangular plate elements and straight line stiffener elements. The program calculates the required amount of reinforcement in the plate elements and stiffener elements based on the design code selected by the user. For solid walls, spWall can also compare cross sectional shear forces with calculated in-plane and out-of plane shear strength provided by concrete.