QAnchor Manual

8/14/2019 QAnchor Manual

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QUICKNCHOR

Users Manual

Version 1.1.5

334 East Colfax Street, Unit E, Palatine, IL 60067

Main Office: West Coast Office (Laguna Niguel,Ph: (847) 991-2700 Fax: (847) 991-2702 Ph: (949) 249-3739 Fax: (949) 249

www.skghoshassociates.com

S. K. Ghosh Associates Inc.Seismic and Building Code Consulting


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REVISION HISTORY

Version 1.1.51. Corrected an error where the program was calculating the value of h,vwrongly for

concrete breakout in shear in Y-direction under certain conditions.

Version 1.1.42. Fixed a bug so that the program now automatically revises the futavalue of ASTM A 449

Grade 1 Steel based on anchor diameter when the anchor diameter is changed AFTERselecting the anchor material.

3. License information can now be seen from the About page of the program.

Version 1.1.34. Both "Simple Output" and "Detailed Output" have been revised to clearly indicate the

alternative options available to a designer when the ductile anchor failure requirement ofACI 318 Section D.3.3.4 cannot be met.

5. "Detailed Output" now indicates the directions of input shear forces in X- and Y-directionsfor easy reference.

6. Printer margins of the outputs are reduced to accommodate more text on a single page.

7. Interface to Open/Save input files is made more user-friendly.

8. Fixed a bug that was calculating incorrect value of the bearing area of the head (Abrg) ofan 1

1/4inch diameter anchor with Heavy Hex head.

Version 1.1.2

1. New feature added in order to enable a user to select the direction of the applied shearforces in X- and Y-directions.

Version 1.1.1

1. Separate input for supplementary reinforcement for tension is added.

2. A calculator is added to facilitate the calculation of the effective area of anchor (Ase) aswell as, for headed anchors, the bearing area of the head (Abrg).

3. The way the program was handling input and output files is revised completely. In thefuture, this will enable the users to directly import their old input files into the newerversions of Quick Anchor.

**NOTE**Due to this change, users will not be able to use the input files that they havecreated using Version 1.1.0 once they install the updated version.

4. A check for minimum spacing and cover requirements of ACI 318 Section D.8 is added.


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5. Output now includes a summery of all the strength calculations, where the governingdesign strengths in tension, shear in the X-direction, and shear in the Y-direction arelisted.

6. A display problem is fixed, where users were unable to see some of the input boxes ofthe program when the DPI setting of their monitor was set at higher than 96 DPI.


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INPUT INTERFACE

Data input in Quick Anchor is done on a single page. The input fields are mostly self-explanatory. However, a short description of each input field is provided below for better

clarity. Different input fields are marked by item numbers, as shown below in Figure 1.

Figure 1. Data input page of Quick Anchor

Item 1: Total number of anchors, n. For a group of anchors (n> 1), anchors need to bearranged in a regular rectangular fashion in rows and/or columns. Anchors that are not

1

2

3

4

6

5

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

2829

30


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arranged in a regular rectangular pattern are not addressed by this program. Pleaseread an additional important note on Page 10 regarding n.

Item 2: Number of rows in which the anchors are arranged. This is automatically set as1 when n= 1.

Item 3: Number of columns in which the anchors are arranged. This is automatically setas 1 when n= 1.

Item 4:Nominal strength of concrete in psi.

Item 5: Click if concrete is uncracked under service load. By default, the programassumes concrete to be cracked under service load.

Item 6: User can select a supplementary reinforcement configuration for tension as wellas for shear. When supplemental reinforcement is provided for tension loading, it onlyincreases the value of the strength reduction factor associated with concrete breakout intension and concrete side-face blowout. When supplemental reinforcement is provided

for shear loading, it increases the value of the strength reduction factor associated withconcrete breakout in shear. Further, the shear supplemental reinforcement configurationselection has an effect on strength calculations when concrete is selected as cracked inItem 5. Three options are provided:

I) ACI 318 D.6.2.7 Paragraph 3 This option is selected when there is nosupplementary reinforcement present between the anchors and the edge ofconcrete, or when supplementary reinforcement comprises of bars smaller thanNo. 4.

II) ACI 318 D.6.2.7 Paragraph 4 This option is selected when No. 4 or largerbars are present between the anchors and the concrete edge.

III) ACI 318 D.6.2.7 Paragraph 5 This option is selected when No. 4 or largerbars are present between the anchors and the concrete edge AND the bars areenclosed within stirrups spaced not more than 4 in.

Item 7: Specify whether grout pads are provided or not. This affects the calculation ofsteel strength of anchor in shear.

Item 8: Select anchor typeheaded studs, headed bolts or hooked (J- or L-) bolts.

Item 9: Select the grade of anchor steel from 9 built-in options or select Other to use adifferent material. When one of the 9 built-in options is selected, the steel tensilestrength, futa, is automatically selected by the program, which appears in Item 10. All

these 9 options are also considered to be ductile as per the definition of ductile steelelement given in ACI 318 D.1. When Other option is selected, user needs to specifyfuta in Item 10. Additionally, when Other is selected, user is presented with two moreinput parameters (Figure 2) that need to be specified one to select if the user-definedanchor steel is ductile as per ACI 318 D.1, and the other to specify the yield strength ofthe anchor steel.


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Figure 2.Additional input parameters for user-defined anchor material

Not all grades of steel are available for all types of anchors. For example, ASTM A 307Grade C is for hooked bolts only, and not for headed bolts or studs. User should becareful when selecting anchor material for a certain type of anchors.

Item 10: Tensile strength of anchor steel in psi. Please read the description of Item 9above for more details.

Item 11: Spacing between anchor columns in inches. Columns are assumed to beuniformly spaced. When the number of columns is 1 (Item 3), spacing is automaticallyset to zero.

Item 12: Spacing between anchor rows in inches. Rows are assumed to be uniformlyspaced. When the number of rows is 1 (Item 2), spacing is automatically set to zero.

Items 13 through 16: Edge distances, in inches, on all four sides of the anchor or theanchor group.

Item 17: Specify concrete depth, ha, in inches.

Item 18: Specify anchor diameter, do(da in ACI 318-08), in inches. User can also clickon the Help button to choose a standard diameter from a drop-down menu (See Item19 for more detail).

Items 19 and 20: Specify the effective cross-sectional area of a single anchor, Ase, andbearing area of the head of a headed anchor,Abrg, in square inches. When hooked (J- orL-) bolts are used, the bearing length of the hook (eh) is specified, in inches, in Item 20.

Effective cross-sectional area is calculated from the following formula:

Ase= (do0.9743/nt)2/4

where nt is the number of threads per inch of the anchor.

A calculator has been provided to facilitate the computation of Ase. Click on the Helpbutton to open the calculator, which appears in a separate window (Figure 3). In thecalculator, user can type in a diameter (in inches) in the box provided or simply choosefrom a list of standard diameters from a drop-down menu. When a standard diameter isselected, the value of nt is obtained automatically based on the selected thread type(Coarse Thread or Fine Thread). However, whenthe user chooses to enter a customdiameter, the value of ntalso needs to be specified.


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Figure 3.Calculator for determiningAseandAbrg

When headed studs or bolts are used, Abrgis calculated by simply subtracting the grossshank area of the anchor from the area of the head. The same calculator that ismentioned above can also be used to calculate Abrg. This option, however, does not

appear when a hooked bolt is being used. To calculate Abrgof one of the listed anchordiameters, the user simply needs to choose the anchor head type (Hex, Heavy Hexor Square). When using a custom diameter, the user also needs to specify thedimension F of the head.

Once Ase and Abrg have been calculated, click OK to import the values into thecorresponding boxes (19 and 20, respectively) in the main window of the program.

Item 21: Specify the effective embedment depth of the anchor(s) in inches.

Item 22: Select if the strength calculation should be done in accordance with ACI 318-05or ACI 318-08. Even though the anchorage provisions of the two editions of ACI 318 are

mostly the same, some differences do exist.

Item 23: Select which load combination equations were used to calculate the tensionand shear demands on the anchor or anchor group. Strength reduction factors

( factors) are calculated based on this selection.


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Item 24: Click if the anchor(s) are part(s) of a structure that is assigned an SDC of C orabove. Depending on which version of ACI 318 is being followed, a factor of 0.75 isapplied to the strengths in all failure modes or only the concrete failure modes.

Items 25 and 26: Specify the direction of applied shear forces in the X- and Y-Directionshere. By default, both options are set to Automatic , so that the program assumes thatthe shear force is directed towards the smaller edge distance. This is appropriate whenthe applied shear is caused by seismic activities. However, for non-seismic applications,users can choose if the shear along the X-axis is directed towards the right edge or theleft edge, and if the shear along the Y-axis is directed towards the top edge or thebottom edge. If there is no shear applied in any direction, leave it at automatic.

Items 27: For a group of anchors, specify eccentricities (in inches) of applied tensionalong X- and Y-axes. Eccentricities are measured from the center of the anchor groupand are always positive.

Items 28: For a group of anchors, specify eccentricities (in inches) along X- and Y-axesof applied shear (Figure 4). Eccentricities are measured from the center of the anchor

group and are always positive.

Figure 4.Eccentricities of applied shear

Item 29.Click on the Check for Splitting Failure button to check if the anchor spacingsand the edge distances specified in the input conform to the requirements of ACI 318

Section D.8. This check is optional in Quick Anchor and does not need to be done forthe purpose of strength calculation. However, it is strongly recommended that the userdo this check in order to make sure that the requirements of ACI 318 Section D.8 aresatisfied. The user needs to first specify the anchor diameter as well as all four edgedistances and the anchor spacings (for a group of anchors) for the checking tool to runproperly.

The checking tool opens in a separate window (Figure 5). When Anchors will betorqued option is selected, the checking tool simply displays if the anchor spacings in X-

Eccentricity along Y-axis

Eccentricity along X-axis


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and Y-directions (for a group of anchors) as well as all the edge distances meet theminimum values specified in Section D.8 for the anchor diameter being used. The userhas the option of either selecting a smaller diameter anchor or increase the distance(spacing and/or edge distance) that failed the check.

Figure 5.Checking tool for splitting failure

When the option Anchor will not be torqued is selected, the user also needs to selectthe type of place where the anchors will be used. If any of the anchor spacing or edgedistance fails the check, depending on the place where the anchors will be used, theuser may get an option of using a smaller diameter just for the purpose of calculation(ACI 318 Section D.8.4). When this option is available, it is shown at the bottom of thewindow and the smaller diameter that can be used in accordance with Section D.8.4 isalso mentioned. The user can choose to use this smaller diameter for the purpose of thestrength calculations by clicking on Revise Diameter button, or simply click on OK toclose the checking tool without changing anything. If the user chooses to revise thediameter, the suggested smaller diameter will be displayed in the corresponding box inthe main program window. The program also revises the value of Ase based on thisrevised diameter. The revised Ase is the gross cross-sectional area calculated from therevised diameter. However, if this value is greater than the originalAse, then the originalvalue is retained. The value ofAbrgis not changed.


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COMPUTATIONAL BACKGROUND

Important Note:

In computing the strength of a group of anchors, this program assumes that all theanchors that have been included in the input are in tension when the group is subjectedto a tensile load. However, when there is an applied moment on an anchor group,because of an eccentricity or an imposed bending moment, some anchors may developnet compression. User needs to determine if such a condition exists, and if it does, inputonly those anchors that are in net tension.

Similarly, the program assumes that all the anchors that have been included in the inputare subjected to shear force in the same direction. If this is not the case (due to atorque), user needs to input only those anchors that carry shear force in the samedirection.

Thus, it is possible that a user may need to use different subgroups out of the samegroup of anchors to compute the tensile and shear strengths of the group.

1. Steel strength of anchor in tension:

Design tensile strength of a single anchor is calculated as

Nsa= stAsefuta

If the SDC of the structure involved is C or above and ACI 318-05 is being followed, afactor of 0.75 is applied to the above value. When ACI 318-08 is followed, this factor isnot required to be applied in this mode of failure.

For a group of anchors, this strength needs to be compared against the maximumtension demand that occurs on a single anchor in the group. Conversely, this strength ofa single anchor can also be converted into the strength of the whole group by dividingthe above strength by the fraction of the total tension demand that the most heavilyloaded anchor resists. For example, if the maximum tension demand on a single anchoris 40% of the total tension demand Nu, then the above design strength can be divided by0.4 to compute the maximum tension demand that the group can accommodate.However, if there is no eccentricity (along X-axis and along Y-axis) in the applied load, it

can be assumed that all anchors accommodate the demand in equal proportions, andthe above strength can simply be multiplied by the total number of anchors present inthe group, n, to obtain the strength of the whole group.

2. Concrete breakout strength of anchor in tension:

Design concrete breakout strength is calculated as:


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Ncb= bN,cpN,cN,ednco

ncct NA

A , for a single anchor, and

Ncbg= bN,cpN,cN,edN,ecnco

ncct N

A

A , for a group of anchors.

Also, if the SDC of the structure involved is C or above, a factor of 0.75 is applied to theabove value.

In calculating ec,N to account for the eccentricity of load application with respect to thecentroid of the bolts loaded in tension, eccentricities in X- and Y-directions (eNxand eNy,respectively) are considered separately and the product of the two factors is considered.

Edge distances on the four sides of the anchor or anchor group are compared against1.5hef and if three or more edge distances are less than 1.5hef then hef is reduced in

accordance with ACI 318 Section D.5.2.3.

The modification factor for concrete that is uncracked under service load is applied inaccordance with ACI 318 Section D.5.2.6.

Since, the program does not address the post-installed anchors at this time, factor cp,Nis assumed to be 1.0.

In addition, for a group of anchors, three cases are considered:

Case 1. sx> 3hefand sy 3hef: In this case, anchor columns act in a group but eachcolumn act independent of others (Figure 6).

Figure 6.Column spacing more than 3hef

In this case, concrete breakout strength of each column is calculated separately. Thestrengths of the intermediate columns would be the same, while the strengths of the rightand left columns could be different if the modification factor for edge effect is less than1.0. Because only one column is considered at a time, eccentricity in X-direction, eNx, is


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not considered in computing the eccentricity factor, and only eNy is used. The effect ofeNxneeds to be accounted for while calculating the tension demand on each column.

The program presents the strengths of individual columns in the output. The user needsto divide the strength of each column by the fraction of the total tension demand that thecolumn carries, to obtain the total tension demand that the whole anchor formation can

accommodate. For example, if a certain column supports 40% of the total demand, itsstrength needs to divided by 0.4 to get the total strength of the whole formation based onthe strength of that column. It should be noted that the column of anchors with the loweststrength may not produce the governing strength for the whole anchor formation if thedemand on that column is also low. As a result, when the user is not certain whichcolumn would be the governing one, strength of the whole anchor formation needs to becomputed based on each column separately and the minimum value should beconsidered as the governing design strength. However, if eNx = 0, then it can beassumed that the total tension demand is distributed uniformly to each column, and as aresult, the strength of the weakest column can be simply multiplied by the total numberof columns in order to calculate the strength of the whole anchor formation.

Case 2. sy> 3hefand sx 3hef: Same approach as in Case 1. Strengths of individualrows are calculated and presented in the output. Strength of the whole formation needsto be calculated by dividing the strengths of the individual rows by the fraction of the totaldemand each of them is carrying.

Case 3. sx> 3hefand sy> 3hef: In this case, all anchors act on their own without anygroup action in either direction. Thus, strength of each anchor needs to be calculatedseparately. The program does not do this automatically. Instead, it asks the user to inputthe critical anchors one by one and then divide their strengths by the fractions of totaltension demand on the respective anchors to obtain the governing total strength.

3. Pullout strength of anchor in tension:

Design tensile strength of a single anchor is calculated as

1. For headed studs and bolts, Np= cpt8Abrgfc

2. For J- or L-hooks, Np= cpt0.9fc ehdo

If the SDC of the structure involved is C or above, a factor of 0.75 is applied to the abovevalue.

The modification factor for concrete that is uncracked under service load is applied inaccordance with ACI 318 Section D.5.3.6.

For hooked (J- or L-) bolts, if bearing length, eh, is less than 3do, pullout strength is notcalculated due to insufficient bearing length. If eh is more than 4.5do, then the pulloutstrength is calculated assuming eh= 4.5do, neglecting the excess bearing length.

For a group of anchors, this strength needs to be compared against the maximumtension demand that a single anchor in the group is subject to. Conversely, this strength


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of a single anchor can also be converted into the strength of the group by dividing theabove strength by the fraction of the total tension demand that the most heavily loadedanchor resists. For example, if the maximum tension demand on a single anchor is 40%of the total tension demand Nu, then the above design strength can be divided by 0.4 tocompute the maximum tension demand that the group can accommodate. However, ifthere is no eccentricity (along x-axis and along y-axis) to the applied load, it can be

assumed that the demand is distributed uniformly, and the above strength can simply bemultiplied by the total number of anchors in the group, n, to obtain the strength of thewhole group.

4. Concrete side-face blowout strength of a headed anchor in tension:

For a single headed bolt or stud, if the minimum edge distance, c a1is less than 0.4hef,then strength is calculated as

Nsb= ct(160ca1Abrg).fc (only normal-weight concrete is considered)

Also, if ca2< 3ca1, then an edge distance correction factor (1+ca2/ca1)/4 is applied to theabove strength, where ca2is the minimum edge distance orthogonal to ca1.

If the SDC of the structure involved is C or above, a factor of 0.75 is applied to the abovevalue.

For a group of anchors, possible side-face blowout failure is investigated in both X- andY-directions. For example, if in the X-direction, ca1< 0.4hef, side-face blowout strength iscalculated in that direction considering the anchors that are in the column nearest to anedge, where ca1 is the smallest edge distance along the X-axis. Similarly, for the Y-direction, if ca1 < 0.4hef, side-face blowout strength is calculated in that direction

considering the anchors that are in the row nearest to an edge, where ca1is the smallestedge distance along the Y-axis.

In case side-face blowout is possible in both X- and Y-directions, the minimum value istaken as the governing strength.

While computing strength in any direction, two scenarios are considered as describedbelow. Even though the description below illustrates failure in the X-direction only, thesame is applicable to a failure in the Y-direction as well.

Case 1. sy 6ca1: The whole column acts as a group (Figure 7). Strength of this columnis calculated as

Nsbg= ct(160ca1Abrg).fc (1+s/6ca1)

The design strength calculated above relates to the anchor column nearest to an edge(the right edge is the governing one in this case). This needs to be compared against thetension demand on that column only. Conversely, the above design strength can bescaled up by dividing by the fraction of the total demand that this column resists tocalculate the strength of the whole anchor group based on the side-face blowout in X-direction. For example, if the tension demand on a the column shown is 40% of the total


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tension demand Nu, then the above design strength can be divided by 0.4 to computethe maximum tension demand that the group can support. However, if there is noeccentricity in the applied load along X-axis, it can be assumed that the demand isdistributed uniformly over all columns, and the above strength can simply be multipliedby the total number of columns present in the group to obtain the strength of the wholegroup.

Figure 7.Side-face blowout as a group

Case 1. sy > 6ca1: The whole column does not act as a group (Figure 8). Rather,individual anchors can undergo side-face blowout failure.

Figure 8.Side-face blowout of individual anchors

In this case, the strengths of individual anchors are calculated as

Nsb= ct(160ca1Abrg).fc

Also, for anchors at the top and bottom of the column (two corner anchors), if theirrespective ca2< 3ca1, then an edge factor (1+ca2/ca1)/4 is applied, where ca2 is top andbottom edge distances for top and bottom anchors, respectively. The ratio c a2/ca1 is nottaken less than 1.0.

ca1

s

ca1


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Once the strengths of individual anchors have been determined, they can be divided bythe fraction of the total demand that each anchor resists to calculate the governingstrength of the whole anchor formation. In case the load eccentricities in both X- and Y-directions are zero, then the minimum anchor strength can simply be multiplied by thetotal number of anchors to calculate the design strength of the whole formation.

5. Steel strength of anchor in shear:

Design shear strength of a single cast-in headed stud is calculated as

Nsa= svAsefuta

Design shear strength of a single cast-in headed bolt or hooked bolt is calculated as

Nsa= sv0.6Asefuta

If the SDC of the structure involved is C or above and ACI 318-05 is being followed, a

factor of 0.75 is also applied to the above values. When ACI 318-08 is followed, thisfactor is not required to be applied in this mode of failure.

For a group of anchors, this strength needs to be compared against the maximum sheardemand that occurs on a single anchor in the group. Conversely, this strength of a singleanchor can also be converted into the strength of the whole group by dividing the abovestrength by the fraction of the total shear demand that the most heavily loaded anchorresists. For example, if the maximum shear demand on a single anchor is 40% of thetotal shear demand Vu, then the above design strength can be divided by 0.4 to computethe maximum shear demand that the group can support. However, if there is noeccentricity in the applied load (along Y-axis), it can be assumed that all anchors carrythe same demand, and the above strength can simply be multiplied by the total number

of anchors present in the group, n, to obtain the strength of the whole group.

6. Concrete breakout strength of anchor in shear:

Shear in X-direct ion

Design shear strength of a single anchor or a group of anchors in X-direction iscalculated as

Vcbx= bV,cV,edvco

vc

cv VA

A

, for a single anchor, and

Vcbgx= bV,cV,edV,ecvco

vccv VA

A , for a group of anchors.

Also, if the SDC of the structure involved is C or above, a factor of 0.75 is applied to theabove values.


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In calculating ec,V to account for the eccentricity of the load application with respect tothe centroid of the bolts loaded in shear, load eccentricity along Y-axis (eVy) isconsidered.

A modification factor for edge effects, ed,V= 0.7 + 0.3ca2/1.5ca1, is applied if ca2< 1.5ca1,where ca1is the edge distance in the direction of the applied shear (see Items 25 and 26

of the program input above), and ca2 is the minimum edge distance in the orthogonaldirection.

Modification factor for concrete that is cracked under service load is applied inaccordance with ACI 318 Section D.6.2.7.

Since, the program does not address the post-installed anchors at this time, factor cp,Vis assumed to be 1.0.

When design is done in accordance with ACI 318-08, modification factor h,V is alsoapplied as per Section D.6.2.8.

If there is ncolnumber of columns in a anchor group, ncolfailure modes, as shown belowin Figure 9, are considered separately, and the governing strength is taken as theminimum from all modes.

Figure 9. Different failure modes in concrete breakout in shear in X-direction

In all failure modes, two edge distances in Y-direction and concrete depth, ha, of theanchor or anchor group is compared against 1.5ca1. If, in a certain mode, all three areless than 1.5ca1then ca1is reduced in accordance with ACI 318 Section D.6.2.4, and therevised ca1is used for all calculations in that mode.

In all failure modes, it is also checked if the row spacing sy 3ca1, where ca1 is thegoverning edge distance for a particular mode, so that all anchors can act as a group.

Vcbgx/3 2Vcbgx/3 Vcbgx

ca1 ca1 ca1

Mode 1 Mode 2 Mode 3


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If for any mode sy> 3ca1, then each row is considered separately (Figure 10). Strengthsof the intermediate rows would be the same, while the modification factor for edgeeffects may need to be applied to the top and the bottom rows based on their respectiveedge distances in Y-direction. Also, because only one row is considered at a time,

eccentricity factor ec,V is not required to be applied. Instead, the effect of eVyneeds tobe accounted for while calculating the shear demand on each row.

Figure 10.Concrete breakout in shear of individual anchors

The program presents the strengths of individual rows in the output. The user needs todivide the strength of each row by the fraction of the total shear demand that the rowcarries, to obtain the total shear demand that the whole anchor formation can support.For example, if a certain row supports 40% of the total demand, its strength needs todivided by 0.4 to get the total strength of the whole formation based on the strength ofthat row. It should be noted that the row with the lowest strength may not produce thegoverning strength for the whole formation if the demand on that row is also low. As a

result, when the user is not certain which row would be the governing one, strength ofthe whole anchor formation needs to be computed based on all rows separately and theminimum value should be considered as the governing design strength. However, if eVy= 0, then it can be assumed that the total shear demand is distributed uniformly over allrows, and as a result, the strength of the weakest row can be simply multiplied by thetotal number of rows present in order to calculate the strength of the whole anchorformation.

Shear in Y-direct ion

Design shear strength of a single anchor or a group of anchors in Y-direction is

calculated through the same approach as described above.

Concrete breakout strengths of a single anchor or a group of anchors are calculated inboth X- and Y-directions separately. However, there are a few exceptions:

Exception 1. ca1,y> 1.5ca1,x: This is applicable to a single anchor or a group of anchors.Notations ca1,xand ca1,yare the edge distances in the X- and Y-directions, respectively, inthe direction of applied shear (see Items 25 and 26 of the program input above). In this

ca1

sy> 3ca1


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case, breakout strength is calculated only in X-direction, and the strength in Y-direction

is assumed to be twice the strength in X-direction after taking ed,V= 1.0, as shown inFigure 11. This is in accordance with ACI 318 Section D.6.2.1(c).

Figure 11.Application of the provision of ACI 318 Section D.6.2.1(c)

Exception 2. ca1,x> 1.5ca1,y: This is applicable to a single anchor or a group of anchors.In the same way as above, breakout strength is calculated only in Y-direction, and thestrength in X-direction is assumed to be twice the strength in Y-direction after taking

ed,V = 1.0, as shown in Figure 12. This is in accordance with ACI 318 SectionD.6.2.1(c).

Figure 12.Application of the provision of ACI 318 Section D.6.2.1(c)

Exception 3. ca1,x1.5ca1,yor ca1,y1.5ca1,x: This is applicable to a single anchoronly. A single anchor is considered to be at a corner when the governing edge distancein any direction is less than 1.5 times the governing edge distance in the orthogonaldirection (Figure 13). In this case, shear strength of the anchor is calculated in both X-and Y-directions separately. Design strength in X-direction is taken as the minimum of

ca1,x > 1.5ca1,y

ca1,y

Vcbgy

Vcbgx= 2Vcbgy

ca1,y > 1.5ca1,x

ca1,x

Vcbgx

Vcbgy= 2Vcbgx


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the calculated strength in X-direction and twice the calculated strength in Y-direction.Design strength in Y-direction is obtained similarly. This is in accordance with ACI 318Section D.6.2.1(d).

Figure 13.Application of the provision of ACI 318 Section D.6.2.1(d)

7. Concrete pryout strength of anchor in shear:

Design pryout strength of one anchor is calculated as

Vcp= cpvkcpNcb

Design pryout strength of a group of anchors is calculated as

Vcpg= cpvkcpNcbg

Ncband Ncbgare the nominal strengths in concrete breakout in tension.

kcp= 1 for hef< 2.5 in. andkcp= 2 for hef 2.5 in.

In case of multiple anchors, when (a) the whole anchor formation does not behave as asingle group in concrete breakout in tension, and (b) there is a eccentricity in tensionload application, the program is not able to calculate Ncbg (it only provides the designstrengths of individual rows/columns in those cases). Thus, Vcpg cannot be calculatedeither. This is stated in the output.

ca1,x

ca1,x ca1,y 1.5ca1,x

Vcbgx= Min(Vcbgx, 2Vcbgy)

Vcbgy= Min(Vcbgy, 2Vcbgx)

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