Masonry Wall - Design Rules

The masonry wall panel element allows you to easily model, analyze and design masonry walls for in plane and out of plane loads. In this section, we will explain the masonry specific inputs and design considerations. For general wall panel information, see the Wall Panels topic. For masonry wall modeling procedures, see the Masonry Wall - Modeling topic. For masonry calculation considerations and code references, see the Masonry Wall - Design topic. For masonry wall results interpretation, see the Masonry Wall Results topic.

Note: All code references in this topic refer to the TMS 402-16 specification unless noted otherwise.

Unity Check

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Setting a maximum Bending Check (Axial & Bending) or a maximum Shear Check controls the rebar which the program chooses for the wall design. A value of 1.0 denotes that the program may choose a rebar layout that is at 100% of capacity.

Note: For the Max Shear Check for in plane design, the program will only optimize the spacing of reinforcement. It will not optimize the grout spacing. If you want to adjust grout spacing, review the Masonry Out tab.

Masonry Wall General

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Masonry Wall Parameters

Parameter	Description
Block Nom Width	Block Nominal Width is the nominal thickness of masonry walls. The program will subtract 3/8" from this value to get the actual thickness. This value is used, along with the value of grout / bar spacing, to determine the effective thickness of the wall. The effective thickness is based on table B3 of the Reinforced Masonry Engineering Handbook, by Amrhein, Copyright 1998.
Block Grouting	Block Grouting defines how the wall is grouted. If "Partially Grouted" is chosen, then the spacing of grout will be based on the bar spacing defined on the Masonry Out tab.
Reinforced	Reinforced defines whether the wall is reinforced or not.
Wall Area Method	Wall Area Method defines where the wall area is taken from. The NCMA option pulls the "A_n" value from the NCMA TEK 141B document. The RMEH option pulls the "Equivalent Solid Thickness" value from Table B-3a and B-3b from the Reinforced Masonry Engineering Handbook, James Amrhein, 5th edition copyright 1998. In doing research on these two methods of calculating the area for a masonry wall, the two methods produce very different results. The NCMA values assume face-shell mortar bedding and web bedding around grout-filled cells. The RMEH values assume full mortar bedding (both face-shells and all webs). The Amrhein values also appear to average in the area of horizontal bond beams as well. This would make the area conservative for a self-weight calculation, but unconservative for stress calculations. With these considerations in mind we are defaulting the behavior to use NCMA by default. See the Masonry Wall - Design topic for the specific calculations regarding NCMA or RMEH. Note: In version RISA-3D V10.0.1 and older the program used both methods in different circumstances. Now the program is consistent with this usage. If you open an existing model from RISA-3D V10.0.1 and older the program will default to the RMEH option. If you start a model from scratch the program will default to the NCMA option. For self-weight the program will ALWAYS use RMEH, as the presence of bond beams in the wall is realistic and this is a conservative value.

Masonry Wall In Plane Design

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Masonry Wall In-Plane Parameters

Parameter	Description
Vert Bar Size	The Vertical Bar Size column lets you define the vertical bar size for the boundary zones.
Bars Per Cell	The Bars Per Cell columns lets you define one or two bars per cell in the boundary zones.
Min/Max Boundary Zone	The Min/Max Boundary Zone column lets you give maximum and minimum boundary zone widths. The program then designs the width based on 8” increments (1/2 of a block length).
Horz Bar size	The Horizontal Bar Size column lets you define horizontal bar size to be used if horizontal reinforcing is required.
1.5x Shear Inc	The 1.5x Shear Inc checkbox has been moved to the Seismic Design Rules spreadsheet in the Masonry Walls tab. Please see Masonry Wall - Seismic Design.
Transfer Load	The Transfer Load option transfers in-plane loads from regions above and below openings into the regions adjacent to the openings. Note that the design of regions above and below openings are omitted.

Masonry Wall Out of Plane Design

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Masonry-Wall-Out-of-Plane Parameters

Parameter

Description

Bar Size

Bar Size is the main vertical bar size to be used for axial/out of plane design.

Bar Space Min/Max

Bar Space Min/Max lets you give a maximum and minimum bar/grout spacing. If you give a range between the max and min, then the program optimizes the reinforcement spacing according to strength requirements (code checks).

Bar Placement

Bar Placement defines how the reinforcement is placed in the wall region. Possible placement is:

Center - puts a single bar centered in a given cell.
Non-Center puts a single bar non-centered in a given cell.
Each Face puts reinforcement on both faces of a given cell.
Staggered alternates the bars on either face along the length of the region.

Note: When using the staggered option, you are selecting to space the bars at each face at double the bar/grout spacing defined above. For example, if you have a staggered spacing at 24" oc you have a bar on the outside face at 48" oc and a bar on the inside face at 48" oc. These bars are staggered, thus you have grout filled cores at 24" oc.

Cover

Allows you to specify the distance from the exterior of the masonry block to the extreme fiber of the reinforcement. The default cover value is defined as Min. The Min input will use whichever governs between these two sections of the specification:

Section 6.1.3.5 states a minimum distance between the inside of the face shell and the reinforcement . RISA is conservative and always assumes this to be 1/2". Thus, the cover calculated in this fashion = t_faceshell + 1/2"
Section 6.1.4 requires a cover dimension = 1-1/2" or 2" depending on bar size and whether the masonry is exposed to weather. In the program this is always assumed to be 1-1/2".

Thus, the Min term will create a cover equal to the maximum of t_faceshell + 1/2" OR 1-1/2".

For any other cover you wish to impose simply overwrite the Min value with your value. If using the Non-Center option then the cover will always be from the +z local axis face of the wall.

For example, let's assume the wall shown below is using the "Non-Centered" reinforcement and the cover is set to 2.5". The image below shows exactly where this bar is then located in the wall (d = 7.625" - 2.5" - 3/8" = 4.75").

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The actual "d" used in design will depend on the governing direction of loading. If load is applied in both out-of-plane directions to the wall then it is possible that a lower level of loading can produce a higher code check because the "d" is smaller in one direction than the other.

If a non-sensical value is defined (i.e. one where the bar does not fall inside of the block core then the program will give an error in the results and place the reinforcement just inside the faceshell of the block.

Note: For the Center bar placement this field is ignored.

Mortar/Cement Types

Mortar/Cement Types lets you specify the type of mortar/cement in the wall. This affects the modulus of rupture (flexural tensile stresses) from Tables 8.2.4.2 and 9.1.9.2.

Transfer Load

Transfer Load lets you transfer out of plane loads from regions above and below openings into the regions adjacent to the openings. Note that the design of regions above and below openings will be omitted.

Masonry Wall Lintel Design

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Masonry Wall Panel Lintel Parameters

Parameter	Description
Depth	Depth is the total depth of your lintel.
Bar Length	Bar Length is the bearing length at either end of the lintel. This is used to calculate the effective length of the lintel.
Bar Size	Bar Size is the reinforcement size for your main reinforcing in the lintel.
Min/Max # Bars Per Layer	Min/Max # Bars Per Layer is the number of bars you wish to have in a given layer of reinforcement. If you give a range between the max and min, then the program will optimize the reinforcement spacing based on geometry of the section and also the number of layers that you have defined.
Num of Layers	Num of Layers is an option if you require multiple layers of reinforcement in the lintel.
c/c Sp of Layers	c/c Spacing of Layers is the distance between layers (if there is more than one).
Dist to Bot	Distance to Bottom defines the distance from the centerline of the lowest-most bar to the bottom fiber of the lintel.
Stirrup Size	Stirrup Size is the size of stirrup that will be added to the lintel if required.
Analysis Method	Analysis Method is the is the lintel analysis method that determines the design of the masonry lintel. The Simply Supported analysis method produces lintel reinforcement design results, which can be seen in the masonry lintel detail report. The FEA analysis method only displays shear and moment diagrams in the detail report for the masonry lintel based on the results of finite element analysis.