Introductory Tutorial for Structural Steel Design Part 2

7/27/2019 Introductory Tutorial for Structural Steel Design Part 2

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Introductory Tutorial for Structural Structural

Steel Design Part 2

Design of Analyzed Structure

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Design of Analyzed Structure

To begin the design, select the "STAAD-PRE" option from the STAAD-III Main Menu. This will open the

graphics window. When the graphics window opens, the analyzed structure should be shown.

To complete the figure of this structure, select the "Icons" button, ninth button from the left on the toolbar. The

surface of this button shows a red pinned support, a blue I-beam, and a black horizontal line at the bottom. From

the Icons menu, turn on the "Joint#, Member#, Prop Name, Shape, Support, and Release" options by clicking

the mouse button when the cursor is on a particular option. Shut off the "Axis" option if it was previously

activated, by selecting it. Click on the "Accept" button to accept your Icon selections. View the structure in the

graphical screen of the Staad Pre Window to make certain that you have the correct input file.
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From the Staad Pre Window, select the "Design" option. When the Design Menu opens, move the cursor to the

"Steel" option

to open the Steel Design Codes Menu. From this menu, select the "LRFD" option to open the LRFD Steel

Design Menu.


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To change the current units for entering the steel design parameters in the more conventional units, select the

"Modify Length & Force Units" Icon (the first button on the left of the toolbar). The surface of this button shows

a yellow weight and a white ruler. The Units Window will open. Select the proper units (for U.S. Customary

units use inches and kips.) To confirm the units, press the "Accept" button in the Units Window.


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After returning to the LRFD Steel Design Menu, the steel design parameters need to be specified. Select the

"Parameter" option on the LRFD Steel Design Menu to open the parameter menu. All of the LRFD parameters

for structural steel design are listed in this menu. To specify the yield strength of the steel, select the "Fyld"

parameter

to open the Parameter FYLD Window. For A36 steel type 36 from the keyboard for the yield strength of the

steel in the current units of inches and kips. Press the "Accept" button in the FYLD window to confirm yourchoice of yield strength. The Select Member window will open.

Since all members have the same yield strength press the "All" button under the "Commands" heading. The

graphic screen in the Staad Pre window will show all members highlighted and the Select Member window will

reappear. Press the "Return" button in the Select Member window to confirm your choice and return to the

LRFD Steel Design Menu.


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To specify another parameter, select the "Parameter" option in the LRFD Steel Design Menu. To specify a

distance along a member length between points of a transverse restraint for column-type flexural buckling aboutthe member local Y-axis select the "LY" parameter to open the Parameter LY window.

Since some members have a transverse restraints distance equal to 180 in., type 180 from the keyboard for this

braced length in the current units of inches. Press the "Accept" Button in the Parameter LY window to confirm

this distance.


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To specify this braced length for a particular member, press the "Object" button under the "Commands" heading

in the Select Member Window. Click on Members 1 and 3 that are shown in the graphic screen in the LRFD

Steel Design Window. Both members should now be highlighted. Click the right mouse button to return to the

Select Member Menu. Press the "Return" button in the Select Member Window to confirm your choice and to

return to the LRFD Steel Design Menu. Repeat this procedure to specify LY for Member 2 as 240 inches.

After returning to the LRFD Steel Design Menu select the "Parameter" option in the LRFD Steel Design to

access the Parameter Menu again to specify a distance along a member length between points of transverse

restraint for column-type flexural buckling about the member local Z-axis, select the "LZ" parameter to open the

Parameter LZ window. Following the same procedure that was discussed for the "LY" parameter, input LZ=180

in. for Members 1 and 3 and LZ = 240 in. for Member 2.


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After returning to the LRFD Steel Design Menu, select the "Parameter" option to reopen the Parameter Menu.

To specify a distance along a member length between points of Internal support of the compression flange or

points of torsimal restraint of the member cross section for beam-type lateral-torsionsal buckling, select the

"UNL" parameter to open the UNL Parameter Window. Following the same procedure that was discussed for

the "LY" parameter, input UNL = 180 in. for Member 1 and 3 and UNL = 240 in. for Member 2.


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After returning to the LRFD Steel Design Menu, select the "Parameter" option in this menu to specify another

parameter. The "UNF" parameter provides an alternate approach to establish an unbraced length for lateral-

torsional buckling. The "UNF" parameter is the ratio of the unbraced length to the total member length. When the

"UNL" parameter is specified, do not use the "UNF" parameter.

To input another steel design parameter, select the "Parameter" option on the LRFD Steel Design Menu to open

the Parameter Menu. To specify a maximum depth for a member cross section, select the "MAX" parameter to

open the Parameter Max Window.

Since the minimum cross-section depth of some members is equal to 14 in., type 14.0 from the keyboard for this

depth in the current unit of inches. Press the "Accept" button in the Parameter Max window to confirm your

choice for this maximum member depth. The Select Member Window will open.

Press the "Object" button in the Select Memeber Window under the "Command" heading. Click on Members 1

and 3 shown in the graphic screen fo the LRFD Steel Design Menu. Both members should be highlighted. Click


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the right mouse button to return to the Select Member Window. Press the "return" button in the Member Select

Window to confirm your choice and to return to the LRFD Steel Design Menu.

To specify another parameter, select the "Parameter" option on the LRFD Steel Design Menu to open the

Parameter Window. To specify a minimum depth for a member crosssection, select the "MIN" parameter to

open the MIN Parameter Window. Following the same procedure that was discussed for the "Max" parameter,

input MIN = 10.0 in. for Members 1 and 3.

Note that both the "MAX" and "MIN" commands will need to be modified in the full-screen editor to DMA and


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DMI, respectively.

After returning to the LRFD Steel Design Menu, select the "Parameter" option in this menu to specify another

parameter. To specify an effective length factor, KY, for column-type flexural buckling about the member local

Y-axis select the "KY" option.

The program then prompts for a K- value to be entered. Since bracing is provided in the direction that is

proportional to the plane of the structure and if the web element for a member in a vertical plane, the ends of that

member can be assumed to be pinned. These member end conditions are represented by an effective length

factor equal to unity. Therefore, type 1.0 from the keyboard. Press the "Accept" button in the Parameter KY

window to continue this function. The Select Member Window will open.


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To specify that both ends of all members are pinned for local Y-axis flexural buckling, select the "All" option

from under the "Commands" heading in the Select Member Window. The graphic screen in the LRFD Steel

Design Window will show all members highlighted and the Select Member window will reappear. Press the

"Return" button in the Select Member Window to confirm the members that have the K-factor and return to the

LRFD Steel Design Menu.

To specify the next design parameter, select the "Parameter" option on the LRFD Steel Design Menu. To specify

an effective length factor, KZ, for column-type local Z-axis, select the "KZ" option.


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The program then prompts for a K-value to be entered. Since the structure is an unbraced frame and since the

web element for each member is in a vertical plane, the columns will have a KZ-value equal to or greater than

unity. Since the ends of the horizontal member in the frame are vertically restrained against translation and since

the web of that member is in a vertical plane, the beam will have a KZ-valve equal to unity. One column has a

fixed base, a top that is relatively restrained by the flexural stiffness of the beam, and is subjected to side sway.These end conditions can be approximated with a KZ-value equal to 1.2; therefore, type the value as 1.2 from

the keyboard and press the "Accept" button in the Parameter KZ window. The Select Member Window will

open.

Select the "Object" option from under the "Commands" heading in the Select Member Window. Click on

Member 1 in the graphic screen of the LRFD Steel Design Window with the left mouse button to highlight

Member 1. Now click the right mouse button to return to the Select Member Window. To confirm the member

choice and to return to the LRFD Steel Design Menu press the "Return" button in the Select Member Window.


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Repeat the same procedure to input KZ=1.0 for Member 2 and KZ=2.0 for Member 3 which is similar to

Member 1, except that the bottom of the member is pinned.

After returning to the LRFD Steel Design Menu, select the "Parameter" option in that menu to open the

Parameter Menu again. The parameter NSF is used for net section calculations in tension members, and it has a

default value of 1.0. Do not use this parameter for this example.

To specify a moment gradient factor, Cb, for lateral-torsional buckling of a member, select the "CB" option from

the Parameter Menu.


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The Parameter CB Window will appear. The program will then prompt for a keyboard entry. To have STAAD

compute the Cb factor for a member, type 0 and press the "Accept" button in this window. The Select Member

Window will open.

Press the "Object" button under the "Commands" heading in the Select Member Window. Select Members 1

and 3 in the graphic screen of the LRFD Steel Design Menu. Both members should be highlighted. Click the righ

mouse button to return to the Select Member Window. Press the "Return" button to confirm your choice and to

return to the LRFD Steel Design Menu.

Repeat the same procedure to input Cb = 1.0 for Member 2. After returning to the LRFD Steel Design Menu,

the next design parameter can be specified.

To obtain a printout of the design of each member, select the "Parameter" option in the LRFD Steel Design

Menu to open the Parameter Menu. Then select the "Track" option from the Parameter Menu to open the

Parameter Track Window.


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Move the cursor to the small circle to the left of the description "(1.0) Print All Critical Member Stress" and click

the left mouse button. A dot will appear in the circle to show the chosen option. Then press the "Accept" button

in this window. The Select Member Window will open. Select the "All" button under the "Commands" heading in

the Select Member Window.

All members should be highlighted in the graphic screen of the LRFD Steel Design Window and the SelectMember window will reappear. Press the "Return" button in the Select Member window to confirm the member

choice and to return to the LRFD Steel Design Menu press the "Return" button in this window.


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To specify another design parameter, select the "Parameter" option in the LRFD Steel Design Menu to open the

Parameter Menu. The "Ratio" parameter can be used to specify a ratio, of the required factored-level strength to

the design strength for member design. A default value of unity exists for the "Patio" parameter. Do not use this

parameter for this example.

To calculate the member strength requirements at the one-twelth points along the member length, select the

"Beam" option from the Parameter Menu.

Move the cursor to the circle just to the left of the description "Calculate Moments at 12th, Max for Design."

Click the left mouse button. A dot will appear in the circle to show chosen option. To confirm this selection of

design functions press the "Accept" button. The select Member Window will open.

Press the "All" button under the "Commands" heading in the Select Member Window. All members should be

highlighted in the graphic screen of the LRFD Steel Design Window and the Select Member window will


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reappear. Press the "Return" button in the Select Member Window to confirm member choice and return to the

LRFD Steel Design Window.

To specify another design parameter, select the "Parameter" option in the LRFD Steel Design window to open

the Parameter Menu. The "DFF, DJ1, and DJ2" parameters can be used to specify a deflection criteria. These

parameters will not be used for this example. To close the Parameter Menu, select the "Parameter" option in the

LRFD Steel Design Window Menu.


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After all of the design parameters have been established, the units should be changed back to the previous units

that were used during the geometry and load generation. Select the "Modify Length & Force Units" Icon to open

the Units Window. Select the proper units (for U.S. Customary units use feet and kips.) To confirm the units,

press the "Accept" button in the Units Window.

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Click here to access the Structural Steel Design Introductory Tutorial Part 1 of 6

Click here to access the Structural Steel Design Introductory Tutorial Part 3 of 6

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Introductory Tutorial for Structural Steel Design Part 2