Gurparam Kang
Gurparam Kang
Gurparam Kang
Gurparam Kang
Brad Crumb
Brad Crumb
Brad Crumb
Brad Crumb
Brad Crumb
This section provides in-depth detail on the steps necessary to successfully complete a shear wall design using the MASS software package.
Contents
There are four design steps necessary to complete a shear wall design:
Assemblage configuration is the first design step, where the material properties of the shear wall (and its flanges if applicable) are entered or selected. Loads input is the second design step, where the loads and moments are applied to the shear wall. Using these loads, the program determines the corresponding load combinations. Moment design is the third design step. At this stage, the program designs the shear wall such that the moment resistance of the shear wall exceeds the maximum factored moment determined at the loads input stage. Shear design is the forth design step. At this stage, the program designs the shear wall such that the shear resistance exceeds the sliding shear and shear due to the factored applied loading. This may require the addition horizontal reinforcement (bond beams or joint reinforcement). Further detailing is left to the designer.
Assemblage configuration is the first step in developing a shear wall design. The program automatically begins at this step when a new assemblage is opened, as can be seen in
Figure 5‑1: Assemblage Configuration: Web and Flanges
Within the materials tab, users can specify the masonry properties of the shear wall web. For a shear wall with no flanges, the Flange tab can be ignored. This subsection deals with the masonry properties of the web only. For entering the masonry properties of a flange, click here to view the section on
In the case of a shear wall, two dimensions must be entered: the length, and the height. A shear wall with a height of 3000 mm has been specified in
Notice that when performing the assemblage configuration design step, the Assemblage Configuration button is outlined in blue.
Figure 5‑2: Entering Shear Wall Dimensions
Note: MASS does not automatically include the mortar joint between the end of the web, and a flange. For the units to not be shaded in red indicating that cuts are required, space for a 10mm mortar joint should be included in the length of the web.
In order include this mortar joint, the length of the web can be increased by 10 mm. For instance, for a shear wall with fifteen 40 cm blocks along its length, the cumulative length of the web is 6000 mm. To include mortar, enter a web length of 6010 mm. Press Enter on the keyboard.
Partial cells along the web length are permitted but not encouraged. For walls that are not modular in web length, cut-off blocks are placed at the right side of the web of the shear wall and are outlined in red to indicate a constructability concern. The program always forces the left side of the wall to start at either the end of a unit or at the half length of a unit. Non-modular blocks are outlined in red indicating a construction concern.
When the height/length ratio is less than 1 (that is: hw<ℓw) and the shear wall is cantilevered (support condition at base is fixed and at top is free), the wall is referred to as a squat wall. MASS allows the design of squat walls. For more information on squat walls refer to Section 5.3.3.
Below the length and height textboxes is the textbox for the thickness of the web.This textbox is grey and therefore disabled. This thickness of the web depends on the masonry unit size selected. The upper limit on the web thickness is the thickness of the largest block permissible which is typically 290 mm (unless a custom size is added to the masonry unit database). The lower limit on the web thickness for a single-wythe wall is indirectly imposed for reinforced walls by the need to fit vertical steel within the block width (refer to the ‘Minimum Clearances’ heading by clicking here). The lower limit for unreinforced masonry is the smallest block size in the masonry unit database. Upon the completion of the moment design step, the masonry unit size used in the design is displayed in this textbox (as seen in
As soon as the assemblage dimensions are entered, and assemblage drawing is available, as shown in
For the shear wall module, MASS supports the use of blocks only (masonry bricks are not included). Block types with the following solidity are provided: hollow, semi-solid, solid, half-high, half-block, and bond block. The default unit types are shown in
Figure 5‑3: Entering the Dimensions of a Shear Wall
Users can also specify the unit supply of the masonry unit. This unit supply list contains default block types based on the solidity selected. For a block with a hollow solidity, the unit supplies available by default are shown in
Figure 5‑4: Choosing the Unit Supply of the Masonry Unit
The unit supply list also includes customized units if they have been entered into the masonry unit database.
Note: In addition to the available block types, users are also able to create a new unit with customized properties) using the Masonry Unit Database. For more information, click here.
For instructions on how to view the properties of a specific unit, refer to Section 2.10. The classification of concrete block properties is governed by CSA A165.1-4 Table 1 to Table 4. For additional information on masonry unit properties refer to page 144 of [1].
Nominal dimensions of a masonry unit include ½ mortar bed thickness on each surface, adding 10 mm to each actual dimension. The actual thickness of a masonry unit, t, is 10mm less than the minimal thickness. In the program, the size of the unit refers to the nominal thickness (t + 10mm mortar joint) of the masonry unit.
The strength selection pertains to the compressive strength of the unit, f’m. The compressive strength of the unit is the resistance to pressure applied to the net area of the block perpendicular to the bed plane that is applied. Therefore it depends on the compressive strength of the material, the percent solid, and the shape of the unit. This compressive strength of a unit, f’unit, contributes to the determination of compressive strength of the masonry assemblage, f’m (governed by CSA S304-14, Tables 3 and 4). The compressive strength of an assemblage takes into account the mortar and grout, as discussed in Section
The unit strengths available for design depend on the supplier, however, the values provided in the program by default are the typical values used in masonry construction. By default, the program leaves all possible sizes and strengths checked-on, as is illustrated in
The program iterates through these possible values, beginning with the smallest and weakest block, and selects the first of these that meets the engineering requirements. The default concrete block sizes available include 10, 15, 20, 25, and 30 cm units. The default block strengths include 15, 20, 25, and 30 MPa.
Note: In some locations in Canada 30 MPa blocks may not be readily available.
Other strengths are possible and are accommodated by the program through the masonry unit database (refer to Section 2.10). MASS does not support using brick units for shear wall design. Users can also select the specific size and strength of the unit, by checking-off all other unit sizes and strengths.
The support conditions should be specified prior to the application of any loads. For shear walls, the support condition permitted at the base is fixed. The possible support conditions at the top are free and fixed(R). The free condition simply refers to a shear wall that is cantilevered, as shown in
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This support condition is typically applied to a pier, where it is assumed that the heavy masonry above the prier prevents the pier’s rotation, as illustrated in
Figure 5‑7: Pier in a Perforated Shear Wall
To select the bottom end fixity of a shear wall using MASS, click on the drop-down box marked ‘Base’. To select the top end fixity of a shear wall using MASS, click on the drop-down box marked ‘Top’, as shown in
Figure 5‑8: Choosing the End Fixities of a Shear Wall
As can be seen in
Figure 5‑9: Masonry Properties Options
MASS only supports a running bond configuration in the shear wall module. Running bond configuration occurs when blocks in a higher course are placed such that the mid-section of each block is aligned with the vertical mortar joints of the lower course. Alternative alignments are also permitted in masonry, but are not supported by MASS. For instance, blocks can be laid with one-third overlap. A one-fourth overlap is however the minimum.
The mortar type in a shear wall module can be changed using the drop-down box shown in
Figure 5‑10: Choosing the Mortar Type
In general, there are five grades of masonry mortar (Types M, S, N, O, and K) that are distinguished by their proportions of lime, cement, and sand, and the resulting properties in terms of compressive strength, ductility, and workability. Only Type S and Type N are currently recommended for structural work, and therefore are the only two mortar types available within the program. Type S is a high compressive strength mortar recommended for structural applications. Type N is a more workable but lower compressive strength mortar used for low-stress bearing and veneer applications. Although strong, Type M has high vapour porosity and poor workability. Type O and Type K are primarily for restoration work.
Note: Types M, S, N, O, and K are arbitrary letters, every other letter taken from the words Mason Work and have no meaning in terms of the mortar properties.
In the shear wall module, the grouting pattern is selected using drop-down box shown in
Figure 5‑11: Choosing the Grouting Pattern
The grouting pattern depends on the masonry unit type selected by users. For hollow concrete blocks, the grouting patterns permitted are: not grouted, partially grouted, and fully grouted. For semi-solid concrete blocks, the grouting patterns permitted are: not grouted, partially grouted, and fully grouted. For solid concrete blocks, the grouting patter permitted is: not grouted. The grouting patterns permitted for each block type are summarized in
Not grouted simply means the shear wall does not contain any grout. This grouting pattern is applicable for shear walls composed of hollow block, semi-solid block, or solid block.
Note: Grout is required for all reinforced cells. By selecting not grouted, users exclude the possibility of a shear wall with vertical and/or horizontal reinforcement.
Partially grouted refers to some cells being grouted, as shown in
Figure 5‑12: Partially Grouted Shear Wall Web
This grouting pattern is applicable for shear walls composed of either hollow block or semi-solid block. In the case of partially grouted walls, only cells that contain reinforcement are grouted. Therefore, the grouted cell spacing is equal to the reinforcement spacing. Partial cells (which are always placed at the right end of the web) are assigned the grouting condition of its neighbouring cell.
In fully grouted masonry, all cells must be grouted, independent of the presence of reinforcement or its spacing. This grouting pattern is applicable for walls composed of hollow block, or semi-solid block.
Note: Fully grouting a semi-solid concrete block wall provides the same fire resistance as a fully grouted hollow block wall, but typically provides less strength and is more difficult to construct.Consider using a hollow concrete block instead of a semi-solid concrete block in this instance.
Note: Choosing a partially grouted or fully grouted pattern does not necessarily result in a reinforced shear wall. MASS design routine begins by attempting to design a shear wall without reinforcement, because this type of wall configuration is typically cheaper and faster to construct. It is possible to choose to detail a wall that is specifically reinforced in the moment design step (refer to the ‘Vertical Steel’ heading in Section
To change the grout strength enter the new grout strength into the textbox, as shown in
Since CSA A179 allows the designer to specify grout either by proportion specification or by property specification, the program allows users to change the grout compressive strength value, as indicated above.
The program uses a default value for the compressive strength of grout of 15 MPa. This value is based on the expected compressive strength of in-situ grout, as indicated in Clause 12.4.1.2 of CSA S304-14.
The compressive strength of grout by proportion specification, in accordance to CSA A179: 7.1.2.3, is in the order of 10 to 12 MPa. However, the strength of in-situ grout is higher than the strength of cylinders cast in non-absorbent moulds because suction from the masonry units reduces the water content in the grout. CSA S304-14: 12.4.1.2 indicates that the in-situ grout strength shall be taken as 1.5 times the 28 d grout cylinder strength test; hence, when using proportion specification the compressive strength for in-situ grout is in the order of 15 to 18 MPa.
Note: Stronger grout (compressive strength above 20 MPa) tends to have lower water content, and thus is less fluid. As a result, it is often difficult to fill the necessary cells or cavities, resulting in poorer performance. For this reason, using a stronger grout to match the compressive strength of the masonry units, or to satisfy development length requirements is not recommended. For more information on grout strength, refer to CSA A179: 7.2.3.
The compressive and tensile strength values of an assemblage are calculated automatically within the program using Table 3 and Table 4 in CSA S304, and depend on the masonry unit type selected and the grouting conditions. Upon the completion of the moment design step, (or as soon as users select only one masonry unit size and strength), the compressive and tensile strength used in the design are displayed in the textbox (as seen in
Users are permitted to override selected compressive and tensile strength values. Depending on the type of unit selected (hollow, solid or semi-solid), and the grouting conditions specified (not grouted, partially grouted, fully grouted), users are permitted to enter only certain types of assemblage compressive strengths. This relationship is summarized in
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Masonry Unit Type |
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User Override of Compressive Strengths |
User Override of Tensile Strengths |
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Hollow
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Not Grouted |
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| Partially Grouted |
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| Fully Grouted |
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Semi-Solid |
Not Grouted |
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| Partially Grouted |
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| Fully Grouted |
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Solid |
Not Grouted |
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Notice in
To override a compressive strength value, uncheck the ‘Auto’ box next to the value to be entered, and enter the compressive strength value into the textbox. Press Enter on the keyboard. For example, for a hollow wall, fully grouted, users are permitted to enter prism test values for f’m solid, f’m hollow, ft grouted, and ft hollow. Uncheck the ‘Auto’ check-box next to each value. Then enter appropriate compressive strength and tensile strength values. Press Enter on the keyboard.
Note: The compressive strength values used in the program are limited to 40 MPa. The tensile strengths used in the program are limited to 2 MPa. For more information, refer to pages 196 and 197 of [1].
For the remainder of this chapter, the ‘Auto’ check-box is checked-on.
At this stage, the only steel property users are permitted to specify is the steel yield strength. There are three popular grades of steel: 300, 400, and 500. Only the 400-grade is widely available and is used in the vast majority of applications. 300-grade reinforcement bars are available in 10 mm and 15 mm sizes. 500-grade reinforcement bars in all sizes are available through special order to steel mills. The yield strength is defaulted to 400 MPa, as shown in
Other vertical steel properties (for example, bar size, bar spacing, etc.) can only be altered once the moment design step has been completed. Refer to Section
The program has the capability of ‘smearing’ the grout in a partially grouted web. This is, rather than treating each cell in the web discretely, an average weighted strength can be determined, and applied to the length of the web, as shown in
Figure 5‑14: Applying Smearing Effects to a Partially Grouted Web
The weighted average compressive strength (effective compressive strength, f’m,eff) is determined by averaging the compressive strengths of the grouted cells (f’m,grouted) and the ungrouted cells (f’m,hollow) with respect to the relative areas:
Where Agrouted is the grouted cross-sectional area of the wall, and Ahollow is the hollow cross-sectional area of the wall. The effective tensile strength can be calculated using the same principles.
Note: This feature only affects the engineering calculations for partially grouted webs. For webs that are not grouted, Agrouted = 0 therefore f’m,eff = f’m,hollow. For webs that are fully grouted, Ahollow = 0, therefore f’m,eff = f’m,grouted.
For a uniform web (no end zones) for example, the effective thickness of the web of the wall is calculated as follows:
Where tgrouted is the thickness of the web, for a grouted cell, and thollow is thickness of the face shells for a hollow cell (or 2 times tf).
MASS contains a ‘Smear grout’ check-box, which allows users to specify smearing the grout in the engineering calculations performed by the program. By default, this check-box is checked-off, treating each cell discretely provides more accurate results (
Figure 5‑15: Choosing to Smear Grout
With the ‘Smear grout’ check-box checked-on, designers can readily compare quick hand-calculations with the calculations obtained by the program. Since however, treating each cell individually provides a more accurate solution, MASS also allows users to check-off the ‘Smear grout’ check-box and obtain the more accurate solution. Both modes provide similar answers. However, using the discrete mode may provide an increase in capacity. For instance, in cases where the compression zone of the wall extends to several ungrouted cells in the web, as shown in
Figure 5‑16: Compression Zone Extends One Grouted Cell into the Shear Wall Web
In this case, in the web, using f’m,grouted rather than using f’m,eff, along with the actual web thickness t rather than the reduced web thickness teff, may provide a notable increase in the moment capacity of the shear wall.
Note: This feature affects how the web is treated only. Checking-off the ‘Smear grout’ check-box has no impact on how partially grouted flanges are treated.
Because the compression zone does not move along the length of the wall cell-by-cell in the flanges, but rather, includes the entire effective length of a flange, whether the cells are treated discretely, or using smearing effects typically has a negligible effect on the capacity of the shear wall.
Note: The opportunity to smear grout is only available for masonry unit types that allow for the presence of grout: hollow blocks and semi-solid blocks.
In the remainder of the examples discussed in this page, the ‘Smear grout’ check-box is disabled to use discrete properties.
Constructability concerns are warnings of potential problems or details that require attention on the construction site based on the design selected. These constructability concerns are conveyed in the form of notes that are printed using output textbox, and in the shear wall assemblage drawings.
During the assemblage configuration step, a textbox provides users with constructability concerns that may arise based on the selected shear wall properties. A sample constructability concern is shown in
Figure 5‑17: Sample Constructability Concern (Non-Modular Length) for 6050 mm Length
The constructability concerns are not displayed in the textbox until at least the moment design step has been completed. Full constructability concerns are not provided until the shear design step is complete.
Note: The success or failure of a design does not depend on the presence of constructability concerns, they are only warnings, and it is up to the designer to adjust the final design to guarantee that it is practical.
At this time, users can proceed to the specifying the properties of flanges (if applicable), otherwise proceed to the loads input design step (Section
Assemblage configuration is the first step in developing a shear wall design. This step allows users to enter the material properties of the shear wall. For the shear wall module only, the assemblage configuration step contains two tabs: the Materials tab, and the Flanges tab, as shown in
Within the flange tab, users can specify the masonry properties of the shear wall flanges. Flange properties must be fully specified. The program does not design for the flanges, as it assumes the walls have already been designed. That is, it does not iterate through possible flange configurations, it simply utilizes the properties specified by users and includes them in the shear wall capacity calculations. Only the web is truly designed by MASS.
For a shear wall with no flanges, the Flange tab can be ignored. This subsection deals with the masonry properties of the flanges only. For entering the masonry properties of a web, refer to Section
Note: MASS does not design for flanges. MASS accounts for the presence of flanges but they must be fully specified.
To specify the properties of a shear wall flange:
This version of the program allows the designer to specify boundary elements on both ends of the shear walls. These boundary elements are traditionally called flanges if they are intersecting masonry walls or boundary elements if they are masonry columns or pilaster units. Boundary elements can also be other materials like concrete or steel, however, this software package does not support other materials.
MASS supports the following boundary element or flange styles: none, T-shape, L-shape (up), L-shape (down), and custom. The left and right boundary element styles can be paired in any combination.
To specify flange properties, click on the Flanges tab, shown in
Figure 5‑18: Choosing the Flange Style
A shear wall can be constructed using any combination of the styles listed in
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An L-shaped (up) right flange consists of a flange leg that placed above the web, on the right side. The bottom block in the flange is aligned with the bottom of the web, as shown in
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For the current version of MASS, customized boundary elements are represented with a single rectangular box, and a single reinforcement area (if applicable).
The shear wall flange dimensions that are required are dependent on the flange style chosen. If none is the flange style chosen, all flange input fields are disabled. For a T-shape flange style, users can select the length of the flange. The thickness of the flange is based on the masonry unit size selected. The T-shaped flange is automatically centered and aligned about the web of the shear wall, and the offset is automatically provided to users. For example, if 30 cm units are used in the web, and a left flange length of 2400 mm is entered, the program centers the left flange, resulting in a left offset value of 1055 mm.
The resulting flange configuration is shown in
Figure 5‑23: Entering a Left Flange Length
Depending on the flange length provided users may wish to remove the need to cut units by adjusting the offset. For instance, for the shear wall shown in
Note: The flange length provided by users may not be the flange length that is used in the engineering calculations. For the engineering calculations, the program uses an effective flange length. This is discussed in greater detail in Section 5.3.3.
Figure 5‑24: Altering the Left Flange Offset
A right flange is specified in the same manner as the left flange. A shear wall with two T-shaped 2400 mm flanges (with offsets of 1200 mm) is illustrated in
Figure 5‑25: Shear Wall with a Left T-Shaped Flange and a Right T-Shaped Flange
Notice that with the addition of the right flange, the masonry unit at the right end of the wall is outlined in red, indicating the design requires cut units. To avoid using cut units, adjust the length of the web by clicking on the Materials tab and entering a new length as shown in
5990mm+20mm = 6010 mm
The program allows for a 10 mm variance. A length of up to 6020 mm can be entered before the program highlights units in red.
Figure 5‑26: Shear Wall (Modular) with a Left T-Shaped Flange and a Right T-Shaped Flange
For the L-shape (up or down) flange style, users can enter in only the length. The thickness of the flange is based on the masonry unit size selected. There is no offset to be entered, since the flange is automatically adjusted to align with the bottom of the web (for L-shape (up)) and the top of the web (for L-shape (down)), as is illustrated in
For a custom boundary element, users are required to enter a thickness and a length. All dimensions in the program are entered in millimeters. Custom flanges are centered about the web (the offset textbox is disabled for custom flanges). A sample right flange with a length of 800 mm, and a thickness of 400 mm has been specified in
Figure 5‑27: Entering the Dimensions of a Custom Flange
For all flange styles, a minimum limit of 290 mm is placed on the length of the flange. This limit ensures that the flange is larger than then web thickness, t, no matter what masonry unit is chosen for the web (a 290 mm unit (30 cm nominal) being the largest of the default units).
The type of masonry unit selected for each flange is selected in the same manner as for the shear wall web. The masonry unit type for each flange is selected independently of one another, and independently of the type of masonry unit type used within the shear wall web.
Shear wall flanges can be constructed using block types with the following solidity: hollow block, semi-solid, solid, half-high, half-block, and bond block. The default unit types for a flange placed to the left of the web are shown in
Figure 5‑28: Choosing the Masonry Unit Type (Left Flange)
Note: T-Shaped flanges are typically constructed using mechanical fasteners. This is difficult to do when using solid units.
Users can also specify the unit supply of the masonry unit. This unit supply list contains default block types based on the solidity selected. For a block with a hollow solidity, the unit supplies available by default are shown in
Figure 5‑29: Choosing the Unit Supply (Left Flange)
The unit supply lists also includes customized units if they have been entered into the masonry unit database (refer to Section 2.10).
The type of masonry unit selected for each flange is selected in a similar manner as for the shear wall web. The important difference is that only one masonry unit size and masonry unit strength can be selected at a time. This is because MASS requires that flanges be fully specified, assuming the flanges are walls that have been successfully designed at a previous time.
In the program, the size of the unit refers to the nominal thickness (t + 10mm mortar joint) of the masonry unit. The strength selection pertains to the compressive strength of the unit, f’m.
The default concrete block sizes available include 10, 15, 20, 25, and 30 cm units. The default block strengths include 15, 20, 25, and 30 MPa. By default, the program selects a masonry unit with the smallest size and the lowest strength, as shown in
A shear wall with flanges designed using 20 MPa, 20 cm units is shown in
Figure 5‑30: Choosing the Size and Strength of the Masonry Units in Left and Right Flange
Note: The size and strength of the unit for each flange is selected independently of one another and independently of the type of masonry used within the shear wall web. For example, a 20 cm unit can be used in the web, and a 30 cm unit can be used in the right flange.
The end fixities of the flanges are assumed to be the same as the end fixity of the web (refer to Section
The masonry properties (bond pattern, mortar type, grout strength, and yield strength) selected in Section
The grouting patterns of the flanges, as well as the compressive and tensile strengths of the flanges can be selected independently of the web.
The grouting pattern in the left flange is changed using drop-down box shown in
The choices for the grouting pattern of each flange depend on the masonry unit type selected by users. For hollow concrete blocks, the grouting patterns permitted are: not grouted, partially grouted, and fully grouted. For semi-solid concrete blocks, the grouting patterns permitted are: not grouted, partially grouted, and fully grouted. For solid concrete blocks, the grouting patter permitted is: not grouted. If not grouted is selected, the ability to place vertical steel is disabled for all masonry unit type. If partially grouted is selected, the grouting pattern is governed by vertical steel placement.
The compressive and tensile strength values of an assemblage are calculated automatically within the program using Table 3, Table 4 and Table 5 in CSA S304 and depend on the masonry unit type selected and the grouting conditions. Upon the completion of the moment design step, (or as soon as users select only one masonry unit size and strength), the compressive and tensile strength used in the design are displayed in the textbox.
To override a compressive strength value, uncheck the ‘Auto’ box and enter the compressive and tensile strength values into the corresponding textbox. For example, for a hollow wall, fully grouted, users are permitted to enter prism test values for f’m,solid, f’m,hollow, ft,grouted, and ft,hollow. Uncheck the ‘Auto’ check-box next to each value. Then enter appropriate compressive strength and tensile strength values, as shown in
Figure 5‑32: User Override of Compressive and Tensile Strengths (Left Flange)
For custom flanges, the compressive and tensile strength of the flange must be provided by users.
Figure 5‑33: Entering Compressive and Tensile Strengths of Custom Flanges
It is common to perform prism tests to gain additional capacity. Because masonry typically fail under compression, designers primarily perform prism tests to determine compressive strength values. However, if users check-off the ‘Auto’ box, the program requires users to provide both the compressive and tensile strengths. It is acceptable to use compressive strength values determined using prism tests, but enter tensile strength values using Table 5 from CSA S304-14.
The compressive and tensile strength values shown in
The steel property (yield strength) selected in Section
As discussed at the beginning of Section
Note: All other flange properties (the style, dimensions, unit type, size, strength, grouting pattern and compressive and tensile strengths) should be entered prior to specifying the vertical steel configuration in the flanges. Changing these flange properties reloads the number of bars per cell to zero (default).
To specify the vertical reinforcement in a T-shape or L-shape flange:
MASS numbers the cells in a flange from the bottom to the top, as shown in
Figure 5‑34: Flange Cell Count
The cell range, by default, includes the entire length of the flange. To change the cell range, use the up or down arrows, or type the cell number into the textbox. This is shown in
Figure 5‑35: Cell Range for Entire Length Flange (Left Flange)
To alter the property of a specific cell (for example, cell 2), enter the cell number in the first textbox and the second textbox, as shown in
Figure 5‑36: Cell Range for a Specific Cell (Left Flange)
Note: The vertical steel configuration for a new cell range overrides a previously entered vertical steel configuration if the new cell range overlaps with a previously specified cell range. In other words when a new vertical steel configuration is entered for a cell range, this new configuration governs over that previously entered for that cell range. The original vertical steel configuration still applies for any cells outside this range.
By default, the number of bars per cell is ‘None’ for the entire length of a flange. The ‘Size’ check-boxes and the ‘Strength’ check-boxes in this case are grey to indicate they are disabled. To activate the ‘Size’ or ‘Strength’ check-boxes for a particular cell range chosen users must select either ‘1’ or ‘2’ bars per cell, rather than ‘None’. The number of bars per cell can be selected under the ‘Configuration’ heading.
To select 1 bar per cell, click on the ‘1’ check-box. To select the bar size desired for the particular cell range chosen, check-on the desired bar size check-box. To select the bar spacing desired for the particular cell range chosen, check-on the desired bar size check-box. For example, click on the ‘No. 20’ check-box to place No. 20 bars along the length of the left flange, at a spacing of 600 mm, as shown in
Figure 5‑37: Selecting the Vertical Reinforcement in the Flanges
Note: The program does not allow users to reinforce a flange without providing reinforcement within the web. This is enforced through minimum reinforcement required in the web.
If there are two bars placed in one cell, MASS requires that the bars be of the same size. It is not possible for users to select the specific size of the two bars independently. The location of the vertical reinforcement bars within the cells cannot be altered by the user: the bars are automatically placed in the centre of the cells.
If users select one bar per cell, the bar is automatically placed at the centre of the cell. If users select two bars per cell, the bars are placed at the centre of the cell, with a bar separation 25 mm (A371-14: 8.2.5.4.9.1).
Note: Flange properties must be fully specified by the designer. It is up to the designer to ensure that cover and spacing requirements of the vertical steel in the flanges is met.
If there are two bars placed in one cell, MASS requires that the bars be of the same size. It is not possible for users to select the specific size of the two bars independently.
For a bar size not specified in the check-box list, enter the bar diameter into the neighbouring textbox and press Enter. The ‘Custom diameter’ check-box then checks-on automatically. A custom diameter of 22.225 mm is specified in
This diameter specified as 22.2225 in millimeters is equivalent to 0.876=7/8 inches. Following the American reinforcement bar sizes, this is the diameter of a No. 7 bar.
Figure 5‑38: Entering a Custom Bar Diameter
Note: Imperial bar sizes must be entered in metric units in the custom diameter textbox.
The custom diameter size is limited to a 25 mm diameter bar. This feature was introduced to allow for imperial reinforcement bar sizes, which are used in some locations in Canada, particularly those in close proximity with the United States border.
Note: MASS provides a lot of versatility and allows for users to change the vertical steel configuration for each cell. Because of this, it is possible for users to specify some rather exotic or difficult to construct flanges. For instance, a designer could specify a flange with a varying number of bars per cell, and varying bar sizes all within one flange. In most cases however, flanges with uniformly distributed vertical steel tend to perform better, are easier to construct and design, and are thus recommended.
The ability to place vertical steel is disabled if the grouting pattern selected is not grouted, because grout is required to anchor vertical steel.
To specify the vertical reinforcement in a custom flange, enter the total area of vertical steel used within the boundary element. The vertical steel is placed at the centre of the boundary element, as shown in
Figure 5‑39: Entering Vertical Steel in a Custom Flange
Horizontal steel properties (joint reinforcement or bond beam reinforcement) can only be altered once the shear design step is completed. Refer to Section
In addition to fully specifying the properties of the flange(s), the designer must also specify the distance from the critical section (where the moment has the largest value) of the shear wall being designed to the top of the web (
Figure 5‑40: Entering the Distance from Critical Section to Top of Web
This is because for the load case and end fixities shown in Figure 5 41 the critical section occurs at the bottom of the shear wall.
Figure 5‑41: Distance from Critical Section to Top of Web
However, if the shear wall is part of a larger structure, the distance from the critical section to the top of the web includes the larger structure above the critical section, as shown in
Figure 5‑42: Distance from Critical Section to Top of Web in a Multi-Storey Structure
For additional information on designing multi-story loadbearing masonry buildings, refer to page 703 of [1].
Note: The distance from the critical section to the top of the web is used to determine the effective flange length(s), as required by CSA S304-14: 7.6.1 and 10.6.2.
Note: If users enters zero, or leaves the default zero value in the distance from the critical section to top of web textbox, the program is not able to use the effects of the flanges, resulting in an effective length of the flange that is equal only to the width of the shear wall web.
At this time, users can proceed to the loads input design step (Section
Added with the release of MASS Version 4.0, boundary elements can be added to either end of a masonry shear wall. The entire process of how they are created, specified, and edited can be found on a dedicated shear wall boundary elements page (click to open).
Loads input is the second step in developing a shear wall design. This step allows users to enter the loads that are applied to the assemblage. Loads are applied in a similar manner for all assemblage types.
, or on the Loads tabThere are two ways to begin the loads input design step: click on the Loads Input button or the Loads tab. Notice that when performing the loads input design step, the Loads Input button is outlined in blue, as shown in 
Figure 5‑43: Loads Input Design Step
Notice that when performing the loads input design step, the Loads Input button is outlined in blue. During this design step, the material and flange properties should not be changed.
The importance category is selected using the drop-down box under the heading ‘Importance category’, shown in
To add a load, click on the Add Load button shown in
The program allows for the selection of the following loads for the shear wall assemblage: dead, live, snow, wind, hydrostatic, earthquake, storage, controlled fluid, and soil. These can be selected using the drop-down box found under the ‘Type’ column.
Figure 5‑44: Choosing Load Types
Similarly to choosing a load type, users can choose the load distribution using the drop-down box found under the ‘Distribution’ column. Load distributions that can be applied to a shear wall include: point loads, axial loads, and moments.
Note: MASS does not allow for eccentric loading in the vertical direction, that is, the centre of loading in the y-direction is considered to be in the centre of the wall section. Instead, eccentricity of the vertical loads can be taken into account indirectly, by applying a moment to the shear wall.
The loads input design step in the shear wall module is more restrictive than in the beam module or the out-of-plane module. For the shear wall module, the location of the load cannot be specified by users. In all cases the load is applied at the height of the shear wall, as shown in 
Figure 5‑45: Point Load, Axial Load and Moment on a Shear Wall
The unfactored magnitude of the selected load is entered in the textbox, under the ‘Magnitude’ column. Negative axial loads (uplift) are permitted. Negative point loads (in east-west direction) or negative moments (in the counter-clockwise direction) however, cannot be applied. To design the wall in the reverse direction click on the ‘Apply loads in both directions’ check-box shown in
A shear wall, experiencing an unfactored dead shear (point) load of 500 kN, an unfactored axial dead load of 1500 kN, an unfactored axial live load of 200 kN, and an applied unfactored dead moment of 100 kN-m is illustrated in
Figure 5‑46: Entering Several Load Magnitudes
Note: According to MASS sign convention, a left-to-right load is considered a positive load, as is a downward axial load. A moment applied in the clockwise direction is considered a positive moment.
The units of the load can be specified using one of the following units (kN/m, N/m, lb/ft, or kip/ft) simply by selecting the drop-down box under the ‘Load units’ column.
Unlike the beam and out-of-plane modules, the percentage of the load sustained is not included in the loads input design step. This is because MASS does not perform any deflection calculations for shear walls.
A specific applied load can be viewed under the Loads tab by clicking on ‘Selected Load’ box of that particular load. Multiple loads can be viewed by holding down Shift key, and selecting the loads to be displayed.
With each new load added, the program uses the Importance category selected in order determine the corresponding factored load combinations based on CSA S304-14: 4.2.2. In order view all applicable load combinations click on the Critical Load Envelope drop-down box, as shown in
Figure 5‑47: Choosing a Load Combination
Notice that the drawings under the Reactions, Moment, and Shear tabs, reflect the selected load combination.
To the left of the ‘Importance category’ drop-down box is the ‘Include self-weight’ check-box. The self-weight is included in the load calculations by default. To exclude the self-weight of the assemblage check-off the ‘Include self-weight’ check-box, as shown in
Figure 5‑48: Including the Self-Weight
The self-weight of a wall depends on the masonry unit size, the unit density, and the grouting condition. It is therefore likely that the self-weight of the wall will change during the moment design step, while the program iterates through all the selected masonry and vertical steel properties. In reinforced, partially grouted walls, for example, the grout is only placed at the location of vertical reinforcement. As a result, the self-weight of the wall will be affected each time the spacing of the reinforcement is changed. Notice, a partially grouted wall with a vertical bar spacing of 1200 mm contains less grout then the same partially grouted wall with a vertical bar spacing of 800 mm.
The self-weight of the wall may also change during the shear design step, while the program iterates through all the possible bond beam configurations. In reinforced, partially grouted walls, for example, the grout is placed at the location of vertical reinforcement and the location of a bond beam. As a result, the self-weight of the wall will be affected each time the spacing of the reinforcement is changed. Notice, a partially grouted wall with a bond beam spacing of 1200 mm contains less grout then the same partially grouted wall with a bond beam spacing of 800 mm.
The program calculates an initial self-weight based on the masonry properties selected in the assemblage configuration design step. The self-weight is included as a dead load.
In order to include the effect of grout on the self-weight of the wall, the grout density is required. In MASS, a grout density of 2350 kg/m3 is assumed. For additional information on self-weight of masonry assemblages, refer to Table B.1 in Appendix B of [1].
For more details on calculating the self-weight of shear walls, refer to Section 8.3 of the Appendix.
To design the wall in the reverse direction check-on the ‘Apply loads in both directions’ check-box shown in
Figure 5‑49: Applying Loads in Both Directions
For this version of the program, the unfactored magnitude of the selected load that is entered in the textbox (under the ‘Magnitude’ column) must result in a positive moment. That is, negative axial loads (uplift) are permitted, however, negative point loads (in east-west direction) or negative moments (in the counter-clockwise direction) cannot be applied (refer to
Figure 5‑50: Original Shear Wall Configuration
The right side of the wall is typically the side in compression
, while the left side of the shear wall is typically in tension. The flange on the right side of the wall is deemed flange 1 and the flange on the left side is deemed flange 2.
Figure 5‑51: Reverse Loading Shear Wall Configuration
Applying the loads in both directions is also permitted in the absence of any flange, particularly if the shear wall web configuration is not symmetric about the vertical axis. This feature does not have an impact on the design if the shear wall is symmetric.
Upon the completion of the loads input design step, users can proceed to the moment design step.
Moment design is the third step in developing a shear wall design. In this step the program iterates through the selected parameters and designs a shear wall such that the total moment resistance due to masonry and all steel reinforcement is greater than or equal to the largest moment at the critical section of the shear wall, for any combination of input loads. The moment resistance is calculated for each load combination by setting the factored axial load equal to the axial resistance and solving for the corresponding moment resistance. For shear walls that are not symmetric, and when users have selected to ‘Apply the Load in Both Directions’ (
In order run the moment design:
, as shown in 
Figure 5‑52: Moment Design Step
Notice that when performing the moment design step, the Moment Design button is outlined in blue. Notice, also, that prior to running the moment design step, the ‘Minimum Clearances’ box is disabled, and there is no location where users can specify the vertical reinforcement properties. Users are required to run the moment design step before specifying any changes.
Highlighted in green are the masonry unit properties and the steel properties that provide a successful design, as can be seen in
Figure 5‑53: Moment Design (Successful)
Note: The ability to place vertical steel is disabled if the grouting pattern selected is not grouted because grout is required to anchor vertical steel.
Notice that upon moving into the moment design step, the program automatically displays the Simplified Results → Moment tab in the bottom window. The ‘Moment Design Summary’ page as well as the status bar at the bottom of the page informs users whether or not a successful design is found. To achieve
Figure 5‑54: Moment Design Summary (Successful Design)
For a partially grouted or fully grouted wall, by default, the number of bars per cell is none. That is, the program attempts to design an unreinforced shear wall first. If the wall does not provide enough capacity, or does not meet seismic reinforcement requirements, then vertical reinforcement is placed in the web of the shear wall, beginning with the smallest number of bars per cell available, the smallest bar size available, and the largest spacing available. For more information on the design strategy of the program, refer to Section 5.5.1.
Note: Due to the large number of iterations the program performs, it may take up to several minutes to reach a successful design. If the program requires more than several seconds to reach a solution, the smaller weaker blocks, or larger bar spacing and smaller bar sizes do not provide enough capacity. In this case, users can easily de-select some of the early iterations in the midst of the design process. This will significantly speed up the program. Refer to Section 5.5.1 for further details.
Upon the completion of a successful or unsuccessful moment design, users may wish to alter the design provided by the program. Under the Materials tab, users can change any of the material properties previously entered or selected. The program automatically re-triggers the moment design step if any of the check-box material selections are altered. For new values that are entered into a textbox (for instance, the height of the shear wall) press Enter on the keyboard to re-trigger a design.
Note: To add new loads, click on the Loads tab. This returns the program to the loads input design step. It will be necessary to repeat the moment design step.
Users can now also change the vertical steel properties used in the design, shown in
Notice that by default the program does not take into account any seismic effects (the seismic hazard index, IEFaSa(0.2), is 0.0). To enter a new seismic hazard index, type the new value into the ‘Seismic index’ textbox shown in
Figure 5‑55: Entering a New Seismic Hazard Index
The seismic hazard index primarily affects the minimum and maximum limits on the area of reinforcement permitted and the permitted spacing (CSA S304-14: 16.4.5).
Note: Seismic design of masonry includes ductility design requirements (conventional, limited, and moderately ductile shear walls). CSA S304-14: 4.6.3, 4.6.4, 4.6.5, and 4.6.6 give the requirements for the design of shear walls of limited and moderate ductility.
For information on calculating the seismic hazard index, refer to the provisions on seismic loading and design in the National Building Code of Canada. Additional information is also provided on page 61 in [1].
With the seismic hazard index entered, users can move on to choosing the vertical steel design mode. A shear wall web can be designed in three ways: by placing steel at a uniform spacing along the length of the wall (‘Uniform steel spacing’ mode), by allowing the program to include additional steel at each end of the shear wall web (‘Concentrated end steel’ mode), or by specifying the steel properties in each cell individually (‘Cell-by-cell design’ mode).
The ‘Uniform steel spacing’ mode is the default design mode in the shear wall module. The first design performed by the program always uses the ‘Uniform steel spacing’ mode. Using this mode, the program places vertical reinforcement at equal spacing along the length of the web. For example, a wall containing one No. 10 bar per cell, spaced at 200 mm is shown in 
Figure 5‑56: Uniform Steel Spacing Mode (150 mm unit, 15 MPa, 1 bar/cell, No. 10 bars, 200 mm spacing)
One way to change to ensure a fully grouted wall is to select a 200 mm. Even if a partially grouted grouting pattern is selected in the assemblage configuration design step, the 200 mm spacing results in a wall that is fully grouted.
A better way to ensure a fully grouted wall is the change the grouting pattern directly (using the grouting pattern drop-down box indicated in
Notice, the program has selected a smaller masonry unit size (100 mm) with a larger strength (30 MPa).
Figure 5‑57: Altering Masonry Properties AFTER the Moment Design Step
The current version of the program only allows for a reinforced web if the flanges are reinforced (and vice versa). Thus, if users remove all reinforcement from the web, the whole shear wall must be designed as unreinforced (i.e. the flanges must be treated as unreinforced as well).
To increase the spacing of the vertical bars shown in
Figure 5‑58: Steel Spacing Mode (150 mm unit, 20 MPa, 1 bar/cell, No. 10 bars, 400 mm spacing)
Notice that at the centre of the wall, the spacing of the two bars is not 400 mm. This is because MASS begins by placing bars at the two ends of the web, and then places consecutive bars at the specified spacing, moving inwards towards the centre of the wall. It is therefore possible for the spacings, when meeting at the centre from either end, to overlap. For a more detailed explanation, refer to Section 5.5.1. The program provides the option of altering the configuration of the wall on a cell-by-cell basis (so this configuration can be readily altered). This is discussed further under the heading ‘Cell-by-cell design’ mode, in Section
The ‘Concentrated End Steel’ mode is selected by clicking on the corresponding radio button shown in
Figure 5‑59: Concentrated End Steel Mode
Using the ‘Concentrated end steel’ mode, the program places vertical reinforcement at equal spacing along the length of the web. In addition, the program places additional steel at each end of the web which can provide more moment capacity. Notice, however, that MASS places a limit on the amount of steel that is placed at the ends. It is advisable to limit the amount of steel placed at the ends, in order limit the size of the cracks and improve the overall performance of reinforced masonry shear walls. In the program, limiting the amount of additional end steel typically increases the amount of uniformly distributed steel along the web, especially for longer shear walls. For more information on concentrating steel at the ends of a web, refer to page 461 of [1].
The maximum amount of steel (by area) permitted at the ends is specified by users as a percentage of the total steel in the web. This maximum amount is applied only when adding steel to the ends. The default percentage is 50% (or 25 % per end), as shown in
Note: Additional end zone steel will not be placed if a successful design is found without applying end zone steel. MASS™ always checks designs without using end zone steel before adding end zone steel in an effort to minimize reinforcement used for a successful design.
The ‘Cell-by-cell design’ mode is selected by clicking on the corresponding radio button shown in
Figure 5‑60: Cell-by-Cell Design Mode
The program must first perform a design using the ‘Uniform steel spacing’ mode. The starting point for a design using the ‘Cell-by-cell design’ mode is the resulting configuration from the previous steel placement mode (whether it is the uniform steel spacing mode or the concentrated end steel mode). Using this mode, users can alter the previous configuration, or specify an entirely new configuration by changing the vertical steel properties in each cell.
Note: When returning to the ‘Concentrated end steel’ mode or the ‘Uniform steel spacing’ mode, the vertical steel configuration specified in the ‘Cell-by-cell design’ mode will be lost.
The vertical reinforcement in a web for the ‘Cell-by-cell design’ mode is specified in a similar manner as vertical reinforcement is specified in the flanges. The only important difference is that vertical reinforcement changes cannot be made to a whole range of cells. This is why the ‘Spacing’ check-boxes are shaded in grey, and therefore disabled (
Note: All properties selected outside of the ‘Vertical steel’ box cannot be specified on a cell-by cell basis. These properties apply to the entire length of the web.
To alter the vertical reinforcement in a cell:
MASS numbers the cells in a web from left to right. A sample shear wall cross-section with six cells is shown in
Figure 5‑61: Flange Cell Count
The default cell number is 1. To change the cell number, use the up or down arrows, or type the cell number into the textbox. This is shown in
Figure 5‑62: Cell Number in Web
To alter cell number 11, for example, type in 11 into the cell number textbox (
Figure 5‑63: Altering the Vertical Steel Properties of Cell Number 11
Notice that because this cell is originally ungrouted, and ‘None’ is selected in the ‘No. of bars’ check-box, the ‘Size’ check-boxes and the ‘Spacing’ check-boxes in this case are grey to indicate they are disabled. To activate the size or strength check-boxes for a particular cell number chosen users must select either ‘1’ or ‘2’ ‘No. of bars’, rather than ‘None’.
Note: If there are two bars placed in one cell, MASS requires that the bars be of the same size. It is not possible for users to select the specific size of the two bars independently.
To select the bar size desired for the particular cell number chosen, check-on the desired bar size check-box. Notice that only one of each can be selected for a single cell. The program does not iterate through the number of bars in a cell, or the bar size when in the ‘Cell-by-cell design’ mode.
For a bar size not specified in the check-box list, enter the bar diameter into the ‘Custom diameter’ textbox, and press Enter. The ‘Custom diameter’ check-box is automatically checked-on. A custom diameter of 22.225 mm is specified in cell number 10, as exemplified
Figure 5‑64: Entering a Custom Bar Diameter
Note: Imperial bar sizes must be entered in metric units in the custom diameter textbox.
The custom diameter size is limited to a 30 mm diameter bar. This feature was introduced to allow for imperial reinforcement bar sizes, which are used in some locations in Canada, particularly those in close proximity with the United States border.
Note: MASS provides a lot of versatility and allows for users to change the vertical steel configuration for each cell. Because of this, it is possible for users to specify some rather exotic or difficult to construct shear walls. For instance, a designer could specify a web with varying bar sizes. The use of different bar sizes inside the same cell is not practical and can lead to confusion during installation. In most cases, webs with uniformly distributed vertical steel tend to perform better, are easier to construct and design, and are thus recommended.
In all reinforced walls there must be at least two bars in the web in order to compare their spacing to the minimum spacing requirements. If a user manually alters the design such there is only one bar in the web, the minimum spacing requirements are not met and thus the design fails. In the case of multiple spacings, the minimum spacing requirements are compared to the largest spacing found in the web. For more information on spacing requirements refer to CSA S304-14: 10.15.1.2 and 16.4.5.3.
MASS places limitations on the possible vertical steel configurations. These possible configurations are based on the current block size as well as the bar separation and side cover. The bar separation and side cover can be manipulated using the ‘Minimum Clearances’ box shown in
Figure 5‑65: Entering Minimum Clearances
The bar separation entered in
The bar separation and side cover are used to determine the location in the cell where the vertical reinforcement steel can be placed, and should meet the requirements for coarse grout. Refer to CSA A371: 8.2.5.7.1 and CSA A165.1-14: 6.2 and 6.3.
For the shear wall module, the vertical steel bars are centred within the width of the block, and placed at the specified bar separation. The side cover does not play a direct role in the placement of the vertical steel. It merely provides a minimum distance between the outer surfaces of the face of the block to the outer surfaces of the nearest reinforcing bar.
For example, a 20 cm unit, with two bars per cell (size No. 10), with a default minimum bar separation of 25 mm, and a minimum side cover (the value entered into the textboxes) is 55 mm as is shown in
Figure 5‑66: Minimum Clearance
Observe, however, that the minimum side cover is not the same as the actual side cover, as shown in
Figure 5‑67: Actual Side Cover
The actual side cover is determined using the bar separation as follows:
Internally, the program checks to ensure that the actual side cover is larger than the minimum side cover entered by the user.
The user is not permitted to enter a side cover smaller than the minimum. The minimum side cover must be at least the face shell thickness plus an additional distance of 13 mm to any surface of masonry (spacing required for coarse grout from CSA A371: 8.2.5.7.1).
Note: Minimum clearances cannot be specified for each cell. The bar separation, and side cover specified applies to all reinforced cells along the length of the web.
Figure 5‑68: Moment Design (Unsuccessful)
Notice that many parameters that were checked-on in Figure 5‑53: Moment Design (Successful) have been de-selected (by the user), meaning these properties are not to be included as possible parameters for the design. The selected properties did not result in a wall that could resist the applied loads (Figure 5‑68: Moment Design (Unsuccessful)).
Figure 5‑69: Moment Design Summary (Unsuccessful Design)
The ‘Moment Design Summary’ page as well as the status bar at the bottom of the page informs users whether or not a successful design is found. Notice in the status bar, that the moment design has been performed, notice also, that there are no masonry unit or vertical steel selections that are highlighted in green (
In general, an unsuccessful design is altered in the same manner as a successful design. For example, check-on the No. 10 bar size, and allow for a smaller bar spacing by checking-on the ‘400’ mm spacing check-box.
The program now provides a successful design, as shown in
It may come as a surprise that the parameters selected in
Note: If the program produces a successful design using a No. 10 bar it is likely that the shear wall is compression-controlled (thus, requiring more grout). This is typically a consequence of the design strategy employed by the program. For more information on the design strategy, refer to Section 5.5.
The unsuccessful design exemplified in
Upon the carrying out a successful or unsuccessful moment design, the shear wall drawing is available (displaying the masonry and vertical steel properties used in the design). The simplified and detailed results for the moment design are also available. The moment design step is not fully completed until the shear design step is completed. This is because the shear design step may warrant use of additional vertical steel. Additional steel will impact the existing moment calculations. Refer to Section
Shear design is the forth step in developing a shear wall design. In order run the shear design:
, as shown in 
Figure 5‑71: Shear Design Step
Notice that when performing the shear design step, the shear design button is outlined in blue.
Using the shear wall configuration from the moment design step, the program calculates the in-plane shear resistance and the in-plane sliding shear resistance of the wall. It then compares the shear resistance and the sliding shear resistance to the factored shear at the critical section (where the factored shear value is the largest along the height of the shear wall).
The design provided in
Figure 5‑72: Moment Design (Unsuccessful)
Using the shear wall configuration from the moment design step, the program calculates the in-plane shear resistance and the in-plane sliding shear resistance of the wall. If the factored shear at the critical section (where the shear value is the largest along the height of the wall) is larger than the shear resistance (Vf > Vrd) the current shear design iteration fails.
If the factored shear at any course height is larger than the sliding shear resistance at any course height (Vf,i > Vr,sliding), the current shear design fails.
If all the possible horizontal steel iterations are exhausted, the program increments the block size/strength and redesigns for the moment and then the shear. For more information on the design strategy used in the shear wall module, refer to Section 5.5.2.
Since the program begins with the parameters that resulted in a successful moment design, it does not change the shear wall design unless the original design did not provide enough shear capacity.
The program automatically re-triggers the moment design step if any of the check-box material selections are altered. For new values that are entered into a textbox (for instance, the height of a shear wall) press Enter on the keyboard to re-trigger the moment design.
If the program does not highlight in green any of the masonry properties, the shear design failed. The selected properties did not result in a wall that could resist the applied loads. The status bar at the bottom of the page informs users of a failed design, and the Simplified Results → Shear tab shows a red ‘X’. An unsuccessful design can be altered by checking-on more masonry properties (if they are available).
The masonry unit properties and the vertical and horizontal steel properties that provide a successful design, are typically highlighted in green. A sample shear wall that successful passes in shear is shown in
Figure 5‑73: Shear Design (Successful)
Upon moving into the shear design step, the program automatically displays the Simplified Results → Shear tab in the bottom window. Upon the carrying out a successful shear design, the shear wall drawing is available, displaying the masonry, the vertical steel, and the horizontal steel properties used in the design. Also, a successful design status is shown in the ‘Shear Design Summary’, as well as, in the status bar. The horizontal steel properties used in the shear wall assemblage are not highlighted in green because the properties may change along the length of the assemblage. The horizontal steel used is however displayed in the shear wall drawing.
Notice, users cannot alter the horizontal steel properties until the shear design step has begun.
Upon the completion of a successful or unsuccessful shear design, users may wish to alter the design provided by the program. Under the Materials tab, users can change any of the masonry properties previously entered or selected. The program automatically re-triggers the moment design step and the shear design step if any of the check-box material selections are altered.
Users can now also change the horizontal steel properties used in the design. Horizontal reinforcement is used to resist diagonal shear stresses. CSA S304-14 permits the use of horizontal reinforcing bars (bond beams) and joint reinforcement (wire installed in the mortar joint), individually or in combination with each other.
Bond beams are one course high beams with reinforcing bars placed along the length of the wall, as shown in
Figure 5‑74: Horizontal Reinforcement (Bond Beams)
To alter the bond beam reinforcement along the height of the shear wall:
There are restrictions placed on the maximum bond beam spacing. For bond beams alone, the maximum non-seismic reinforcement spacing permitted is 2400 mm (CSA S304-14: 10.15.1.3), and the maximum seismic reinforcement spacing permitted is 1200 mm (CSA S304-14: 16.4.5.4). For a shear wall with bond beams and joint reinforcement, the maximum spacing permitted by CSA S304-14: 10.15.1.3 and CSA S304-14: 16.4.5.4 is 2400 mm for the bond beams and 400 mm for the joint reinforcement
The program allows a maximum of two bars in a bond beam. The horizontal bars are placed at a knockout depth of 100 mm (from the top on the bond beam). The bar sizes are limited by the unit size (space in a cell). To simplify the bar size limitation, the program assumes that the same bars that fit in the vertical direction fit in the horizontal direction.
Note: If a user selects ‘not grouted’, the walls must be unreinforced in both the vertical direction and the horizontal selection. Vertically unreinforced walls are permitted to have bond beams or joint reinforcement, so long as the ‘partially grouted’ or ‘fully grouted’ condition was selected by users. Adding bond beams in a partially grouted wall may increase its self-weight, since bond beams are fully grouted courses of masonry. Refer to Section
Joint reinforcement consists of thin wires placed within the horizontal (bed) joint of the masonry wall, as shown in
Figure 5‑75: Horizontal Reinforcement (Joint Reinforcement)
In practice, there are two main types of joint reinforcement; ladder (
Figure 5‑76: Joint Reinforcement: a) Ladder and b) Truss)
To alter the joint reinforcement along the height of the shear wall:
There are restrictions placed on the maximum joint reinforcement spacing. For joint reinforcement alone, the maximum non-seismic reinforcement spacing permitted is 600 mm for 50% running bond and 400 mm for other patterns (CSA S304-14: 10.15.1.3). For shear walls, only running bond is allow in MASS. The maximum seismic reinforcement spacing permitted is 400 mm (CSA S304-14: 16.4.5.4). For a shear wall with bond beams and joint reinforcement, the maximum spacing permitted by CSA S304-14: 10.15.1.3 and CSA S304-14 16.4.5.4 is 2400 mm for the bond beams and 400 mm for the joint reinforcement.
The program does not show bends or hooks at the end of the reinforcing bars. For this version, the program assumption is that the bar configuration input extends for the entire height of the wall.
Upon the carrying out a successful or unsuccessful shear design, the shear wall drawing is available (displaying the masonry and vertical steel properties used in the design). The simplified and detailed results for the shear design are also available. Refer to Section 5.3 for a complete discussion on the shear design results.
Upon the completion of the shear design step, the shear wall design is complete.
Continue Reading: A Complete Shear Wall Design
