9. Precast Concrete Bearing Wall Panel Analysis and Design - spWall Software

spWall is a program for the analysis and design of reinforced concrete shear walls, tilt-up walls, precast wall and Insulate Concrete Form (ICF) walls. It uses a graphical interface that enables the user to easily generate complex wall models. Graphical user interface is provided for:

• Wall geometry (including any number of openings and stiffeners)

• Material properties including cracking coefficients

• Wall loads (point, line, and area loads)

• Support conditions (including translational and rotational spring supports)

spWall uses the Finite Element Method for the structural modeling, analysis, and design of slender and non-slender reinforced concrete walls subject to static loading conditions. The wall is idealized as a mesh of rectangular plate elements and straight line stiffener elements. Walls of irregular geometry are idealized to conform to geometry with rectangular boundaries. Plate and stiffener properties can vary from one element to another but are assumed by the program to be uniform within each element.

Six degrees of freedom exist at each node: three translations and three rotations relating to the three Cartesian axes. An external load can exist in the direction of each of the degrees of freedom. Sufficient number of nodal degrees of freedom should be restrained in order to achieve stability of the model. The program assembles the global stiffness matrix and load vectors for the finite element model. Then, it solves the equilibrium equations to obtain deflections and rotations at each node. Finally, the program calculates the internal forces and internal moments in each element. At the user’s option, the program can perform second order analysis. In this case, the program takes into account the effect of in-plane forces on the out-of-plane deflection with any number of openings and stiffeners.

In spWall, the required flexural reinforcement is computed based on the selected design standard (ACI 318-14 is used in this example), and the user can specify one or two layers of wall reinforcement. In stiffeners and boundary elements, spWall calculates the required shear and torsion steel reinforcement. Wall concrete strength (in-plane and out-of-plane) is calculated for the applied loads and compared with the code permissible shear capacity.

For illustration and comparison purposes, the following figures provide a sample of the input modules and results obtained from an spWall model created for the reinforced concrete wall in this example.

In this model the following modeling assumptions have been made to closely represent the example:

1. 5’ wide section of wall is selected to represent the tributary width effective under each of the double tee beam ribs.

2. Idealized continuous wall boundaries using a symmetry support along the vertical edges

3. Pinned the base of the wall assuming support resistance is provided in the X, Y, and Z directions

4. Roller support was used to simulate the diaphragm support provided by the double tee roof beams

5. The load is applied as a single point load under the double tee rib. This can also be applied as a line load or multiple point loads if the complete wall is modeled.

Figure 3 - spWall Interface

Figure 4 - Assigning Dead Loads for Bearing Wall (spWall)

Figure 5 - Assigning Live Loads for Bearing Wall (spWall)

Figure 6 - Assigning Wind Loads for Bearing Wall (spWall)

Figure 7 - Solve and Mesh Options (spWall)

Figure 8 - Factored Axial Forces Contour Normal to Precast Wall Panel Cross-Section (spWall)

Figure 9 - Precast Wall Panel Lateral Displacement Contour (Out-of-Plane) (spWall)

Figure 10 - Precast Wall Panel Axial Load Diagram (spWall)

Figure 11 - Out-of-plane Shear Diagram (spWall)

Figure 12 - Bearing Wall Moment Diagram (spWall)