Member Definition Dialog

Opens when Member Definition is selected in the Superstructure group.

Setting

Description

Member Group

Select the member group that the members are being defined for, from the drop-down list in the upper left corner of the dialog.

Members

This list will show the members that encompass the selected group. Member 01 is initially highlighted by default. Click on any member to make it active for member definition activities.

Fracture Critical

Fracture Critical check box is taken in consideration for Fatigue analysis.

Reset

This button will erase all beam elements for selected member.

Copy definition to

After a member has been defined, select a destination to copy the member to if all members are alike or similar. Options are to copy the current member definition to All Members or one of the other members in the group.

Flange thickness

This option will exaggerate the flange thickness for display purposes only.

Save DGN

The following button will export the Members 2D model directly and accurately to MicroStation DGN file format, including layers. Save the DGN file in the desired location and once the export is successful you can browse to file location and open/view in Micro Station.

Member element

This drop down list contains all of the elements that can be used to define the member. They are:

I-Girders:
- Standard Section
- Web
- Top Flange
- Bot. Flange
- Top Cover Plate - multiple can be defined at the same location.
- Bot. Cover Plate - multiple can be defined at the same location.
Tub-Girders:
- Bottom Flange
- Webs
- Top Flanges

Add

For the Member element selected above press the Add button to add it to the member. A line will appear in the grid where the defining data for the element will be entered. This information is described below.

Ref. Span.

From the drop down list, select the support that the left end of the element will be referenced to.

Begin

This is the start distance of the left end of the element from the reference support. Positive distances are to the right and negative distances are to the left.

Span / Fraction

Optionally, the left end of the element can be located by specifying a percent of the span length. For example, to start at the mid-point of the current span, enter .5. Note that the Start distance will automatically change accordingly.

Length

Enter the length of the element in feet.

Length / Fraction

Optionally the length of the element can be entered as a percent of the overall length of the member (including all spans that are traversed for continuous members). For example if the member is 100 feet long and .75 is entered, the element will be 75 feet long. The length field will change according to the x/L value entered.

Material

Select the material to be used from the drop-down list. The materials are those shown in the material table.

Section

If the element is Standard Section, select the standard section shape from the drop-down list of available sections.

Web(s)

Setting	Description
Thickness	If the element is web, enter the thickness of the Web plate in inches.
Max. Thick.	Enter the maximum web plate width to be used as an upper limit if design optimization is used.
Start height	If the element is web, enter the starting height of the Web plate in inches.
Variation	Select the variation method for the Web plate: None – the web plate is constant depth. Linear - the web plate varies linearly from start height to end height. Parabolic Up - the web plate varies parabolically up (hold water) from start height to end height. Parabolic Down - the web plate varies parabolically down (shed water) from begin height to end height. Circular Up - the web plate varies circularly up (hold water) from start height to end height. Circular Down - the web plate varies circularly down (shed water) from start height to end height.
End Height	If the element is Web, enter the end height in inches of the web plate. This field is active only if one of the transition options is selected.
Location Bot.	This option is only available for Tub Girders. Enter the distance from the centerline of tub girder to the bottom of web.
Location Top	This option is only available for Tub-Girders. Enter the distance from the centerline of the tub girder to the top of web.

Top Flange(s)

Setting	Description
Thickness	Enter the thickness of the plate in inches. This is considered a minimum thickness within Design Optimization.
Max Thickness	Enter the maximum plate thickness to be used as an upper limit if design optimization is used.
Start Width	Enter the start width of the plate in inches. This is considered a minimum width within Design Optimization.
Variation	If the element is Top Flange, select the variation method: None – the plate is constant width. Linear - the plate width varies linearly about its centerline.
End Width	Enter the end width in inches. This field is only active if the Variation method is linear.
Max Width	Enter the maximum plate width to be used as an upper limit if design optimization is used. This field is only active if the Variation method is None.
Web Offset	This option is only available for Tub-Girders. Enter the distance desired from centerline of the web to centerline of top flange.

Bot. Flange

Setting	Description
Thickness	If the element is Bot. Flange, enter the thickness of the plate in inches. This is considered a minimum thickness within design Optimization.
Max Thickness	Enter the maximum plate thickness to be used as an upper limit if Design Optimization is used.
Start Width	Enter the start width of the plate in inches. This is considered a minimum width within Design Optimization.
Variation	If the element is Bot. Flange, select the variation method: None – the plate is constant width. Linear - the plate width varies linearly about its centerline.
End Width	Enter the end width in inches. This field is only active if the Variation method is linear.
Max Width	Enter the maximum width of the plate in inches to be used in Design Optimization. This field is only active if the Variation method is None.

Top Cover

Setting	Description
Thickness	If the element is Top Cover plate, enter the thickness of the plate in inches.
Width	If the element is Top Cover plate, enter the start width of the plate in inches.

Bot. Cover

Setting	Description
Thickness	If the element is Bot. Cover plate, enter the thickness of the plate in inches.
Width	If the element is Bot. Cover plate, Enter the start width of the plate in inches.

Delete

Highlight the line in the grid and press this button to delete it from the member definition.

Insert

Highlight the line in the grid that comes after the element to be inserted. A line will be added to the grid to define the element to be inserted.

Generate Plates

The Generate Plates option provides an automated method of establishing initial top, bottom and web flange plates for a member, or members, based on parameters described below in the Generate Plates Methodology section below. From the dropdown list, select one of the three options:

Selected Member - plates will be generated for the selected member only
Members in Selected Group - plates will be generated for all members in the currently selected Member Group
Members in All Groups - plates will be generated for all members in all member groups associated with the bridge

When Generate Plates is accepted the user is presented with a dialog showing the initial plates sizes that will be used (see below). Any of these values can be changed by the user.

Design Optimization

The Design Optimization commands provide tools to automatically size the member plates based on iterating through the appropriate AASHTO code articles. Design optimization considers both flange and web plates (web plates are optimized for thickness and/or stiffener spacing as described below). See the section Overview of Design Optimization process for more information on the optimization process. Initial plate sizes must be entered for the flanges and web before the optimization process can be initiated. The Generate Plates command can be used to establish initial plates sizes that the optimization process will start with. Design optimization only increases plate sizes so it is best to start with plates that are smaller rather than large. The Design Optimization Process can be repeated after and changes are made without reanalyzing the bridge.

Design Optimization - From the drop down list select one of the following options:
- Selected Member - selecting this option will initiate design optimization for the currently selected member
- Members in Selected Group - selecting this option will perform design optimization on all members in the member group
- Members in all Groups - selecting this option will perform design optimization on all members in all member groups
  Pressing the Auto Design button will update the plates in the Member Definition dialog using the largest flange/web plate size (see Plate No. column).
  
  Pressing the Show Report button will generate separate reports for the top flange, bottom flange and web for the member (or members) being optimized.
  
  See the section Design Optimization Results for more information on the design optimization process.
Design Results - Press this button to view the results of the Design optimization. The Design Optimization results are displayed in a dialog on a POI by POI basis as shown below. The dialog includes three tabs that allow viewing of Top Flange, Bottom Flange and Web results
Width Increment - Enter the value (in inches or mm) to be used to increment flange plate widths during the design optimization process. The default is 1.0 inch (25.0 mm)
Plot Results in Elevation View - Check this box to show:
- Flange areas for the top and bottom flange (if top or bottom flange is the active member Element) as provided based on the user input thickness and width and the required flange area based on the design optimization process.
- The web shear demand (Vu) and required resistance (ΦVn) if web is the active Member element as determined by the design optimization process.

OK

Press this button to save all changes and exit the dialog.

Cancel

Press this button to exit the dialog without saving changes.

Generate Plates Methodology:

This feature provides a means of quickly generating flange and web plates of steel plate girders as an initial trial size. This feature does not currently apply to standard shapes. When using "Generate Plates", the minimum values for Thickness, Start Width, and End Width will be filled based on the rules listed below, and the Max Thickness and Max Width values are filled based on a 4-inch x 96-inch maximum-sized plate. The following rules apply when setting minimum dimensions:

Depth of Web (D) = Maximum Span Length (all girders in a span) (L) /X rounded up to nearest multiple of 2 in. with a minimum of 24 in.
X is based on the following:
- Curved span: X = 25
- Straight simple span: X = 30
- Straight Continuous Span: X = 35
For example, straight continuous beam with L = 148 ft:

D = 148x12/35 = 50.74 in => 52 in.

Use maximum web depth required for all spans and all girders (constant depth throughout).
Thickness of Web (tw) = D/150, rounded up to nearest multiple of 1/16th in. with a minimum of 1/2 in. For example, D = 52 in: tw = 52/150 = 0.35 => 1/2 in.
If web thickness changes are due to different span lengths, use the thicker web to 25% of the length of the adjacent span with the thinner web (do not change web thickness at pier)
Width of Flanges, bf = D/6 rounded up to the nearest user specified width increment, with a minimum of 12 in. For example, D = 74 in: bf = 74/6 = 12.33 in. => 13 in. (for width increment = 1 in.)
Thickness of flanges, tf = maximum of [ Width of Flange (bf)/24] and [tf >= 1.1*Web Thickness tw ], rounded up to nearest multiple of 1/8 in. with a minimum of 1/2 in. For example, bf = 13 and tw = 0.5: tf= max( 13/24 = 0.542 and 1.1*0.5 = 0.55) => 5/8 in.
If flange dimensions change due to different span lengths, use the larger area flange to 25% of the length of the adjacent span with the smaller flange area (do not change flange dimensions at pier).
Use Grade 50 as a default material.
Automatically place "cuts" in flange plates at 25% of span on either side of interior supports, even if plates do not change.

Overview of Design Optimization

The Design Optimization process will start with the member definition as described in the Member Definition dialog. In the case of top and bottom flanges this will be the thickness and start width. These can be thought of as the minimum thickness and minimum width respectively. Two additional fields on the same dialog, max thick and max width, will set the upper bounds for each dimension as the Design Optimization process sizes the plates.

Webs starting information will be the web height and thickness plus any transverse and/or longitudinal stiffeners that may have been added to the model.

Flange Plate Optimization-

The general process used by the flange plate Design Optimization process is as follows. Note that internally LEAP Bridge Steel generates a master available plate list that is sorted by area. All plates in the list satisfy specification b/t ratios.

At each POI:

Perform code checking for each load combination defined in the Loads dialog. The code checking will be based on the Articles/equations listed in the Specification Checks table below.
If a Specification failure occurs for an article/equation, flag the failure type as described in the table below and perform the specified action.
- Leap Bridge Steel will eliminate all plates in the master plate list that fall outside the plate width and thickness and maximum width and maximum thickness that are entered for the respective flange plates. This adjusted plate list is again sorted by plate area.
- Using the recomputed plate area look up a new plate in the adjusted plate list. The new plate will be the first one in the list with area that is greater than or equal to the previously computed area

Repeat this process until a satisfactory top and/or bottom flange plate is obtained or the maximum size of the top and/or bottom flange plates are reached.

Flange Specification Checks:

This table shows the specification articles and equations that are checked as part of the design optimization process along with the action that the process takes for each when the check fails.

Spec Failure	Description	Resulting Action
6.10.1.6-1	Tension Flange Lateral Bending Stress Check	Increase Size of Tension Flange
6.10.1.6-1	Compression Flange Lateral Bending Stress Check	Increase Size of Compression Flange
6.10.2.2-1	Compression flange width/thickness ratio	Increase Size of Compression Flange
6.10.2.2-1	Tension flange width/thickness ratio	Increase Size of Tension Flange
6.10.2.2-2	Compression flange min width	Increase Size of Compression Flange
6.10.2.2-2	Tension flange min width	Increase Size of Tension Flange
6.10.2.2-3	Compression flange min thickness	Increase Size of Compression Flange
6.10.2.2-3	Tension flange min thickness	Increase Size of Tension Flange
6.10.2.2-4	Flange Moment of Inertia Ratio	Increase Size of Tension Flange
6.10.3.2.1-1	Compression flange yielding	Increase Size of Compression Flange
6.10.3.2.1-2	Compression Flange Strength Limit State	Increase Size of Compression Flange
6.10.3.2.1-3	Web Bend-Buckling	Increase Size of Compression Flange
6.10.3.2.2-1	Tension flange yielding	Increase Size of Tension Flange
6.10.3.2.3-1	Compression flange yielding	Increase Size of Compression Flange
6.10.3.2.3-1	Tension flange yielding	Increase Size of Tension Flange
6.10.3.2.4	Stress in Concrete Deck	Warning Message
6.10.4.2.2-1	Composite top flange stress	Increase Size of Top Flange
6.10.4.2.2-2	Composite bottom flange stress	Increase Size of Bottom Flange
6.10.4.2.2-3	Non-composite top flange stress	Increase Size of Top Flange
6.10.4.2.2-3	Non-composite bottom flange stress	Increase Size of Bottom Flange
6.10.4.2.2-4	Compression Flange Stress Requirement	Increase Size of Compression Flange
6.10.7.1.1-1	Tension flange Strength Limit State	Increase Size of Tension Flange
6.10.7.2.1-1	Compression flange check	Increase Size of Compression Flange
6.10.7.2.1-2	Tension flange check	Increase Size of Tension Flange
6.10.7.3-1	Ductility	Increase Size of Top Flange
6.10.8.1.1-1	Compression Flange Strength Limit State	Increase Size of Compression Flange
6.10.8.1.2-1	Tension flange Strength Limit State	Increase Size of Tension Flange
6.10.8.1.3-1	Continuously Braced Compression Flange Check	Increase Size of Compression Flan

Plate Library:

This table shows the thicknesses that the design optimization process progresses through when incrementing top and bottom flange plates.

English Plate Thickness	Decimal	Soft Conversion Metric Plate Thickness
5/16	0.3125	8
3/8	0.375	10
7/16	0.4375	11
1/2	0.5	13
9/16	0.5625	14
5/8	0.625	16
11/16	0.6875	17
3/4	0.75	19
13/16	0.8125	21
7/8	0.875	22
15/16	0.9375	24
1	1	25
1-1/8	1.125	29
1-1/4	1.25	32
1-3/8	1.375	35
1-1/2	1.5	38
1-5/8	1.625	41
1-3/4	1.75	44
1-7/8	1.875	48
2	2	51
2-1/4	2.25	57
2-1/2	2.5	64
2-3/4	2.75	70
3	3	76
3-1/4	3.25	83
3-1/2	3.5	89
3-3/4	3.75	95
4	4	102

Flange Design Optimization Results:

Flange optimization results are shown in both graphical and report form. Graphical results will appear if the Plot results in elevation view box is checked ( )when the Member element is set to Flange. A description of the graphic results display is shown below. The adequacy of the flanges is represented by the flange area. Plate sizes that correspond to the flange areas are shown in the flange optimization report. In cases where the required area exceeds the actual area either the plate thickness or width can be changed.

If it is desired to use the computed top and bottom flange results in the model definition, the Auto Design button () on the Results dialog can be used. This will cause the flange plate sizes (width and thickness) in the Member definition grid to be updated.

The results of the design optimization process are shown in the report shown below that is generated when the Design results button is pressed.

The report shows, on a POI by POI basis, the flange area based on the plate sizes entered on the member definition screen. The required flange plate area based on the design optimization process is shown next. The required area, width and thickness are shown in red for Instances where the input flange plate did not satisfy demand. The performance ratio for the optimized design is also shown.

Given the information in the Design Optimization Report, the model can be updated with revised plate sizes and re-optimized until an acceptable design results.

The required area is optionally plotted in the elevation view if the "Plot results in elevation view" option is checked.

Web Plate Optimization-

The general process used by the web plate design optimization process is as follows.

At each POI:

Perform code checking for each load combination defined in the Loads dialog. The code checking will be based on the Articles/equations listed in the Specification Checks table below.
Start with the specified web height and web thickness, iterating the thickness in 1/16 in increments up to the maximum web thickness. Additionally, any transverse or transverse/longitudinal stiffeners are taken into account.
Determine if the demand (Vu) exceeds the resistance (ΦVn)
- If so, increment the web thickness and repeat the process
If demand is less than the resistance and the web thickness has not exceeded the input maximum thickness, the solution is reported as the Required solution (tw and d0) in the Design Optimization Results dialog. If the computed web thickness also qualifies as an unstiffened web no required stiffener spacing (d0) is reported. Otherwise a required stiffener spacing to satisfy demand is reported.
In addition to generating the required result with respect to the input data, the web optimization process will also compute and report the following as additional information for the user:
- the web thickness that will work as unstiffened
- whether longitudinal stiffeners are required (i.e. 150 < D/tw 300)
- the web thickness that will work for the maximum transverse stiffener spacing for transverse stiffening only
- the web thickness that will work for the maximum transverse stiffener spacing if the web is longitudinally stiffened.

Web Specification Checks:

This table shows the specification articles and equations that are checked as part of the web design optimization process along with the action that the process takes for each when the check fails.

Table 1.
Spec Failure	Description	Resulting Action
6.10.2.1.1-1	Min thickness of web without longitudinal stiffeners	Add longitudinal stiffener (last iteration ?)
6.10.2.1.1-2	Min thickness of web without longitudinal stiffeners	No solution - web fails (last iteration)
6.10.3.3-1	Shear in stiffened webs	Increase web thickness
6.10.5.3-1	Shear check Strength limit state	Increase web thickness
6.10.9.1-1	Shear check Strength limit state	Increase web thickness

Web Design Optimization results

Web optimization results are shown in both graphical and report form. Graphical results will appear if the Plot results in elevation view box is checked () when the Member element is set to Web. A description of the graphic results display is shown below. Note that the results shown are for the Required results as described in the report section below.

If it is desired to use the computed required results in the model definition, the Auto Design button () on the Results dialog can be used. This will cause the web plate sizes (thicknesses) in the Member definition grid to be updated.

Reported results for the web optimization process are described below. The report is generated when the Show Report button is pressed on the Design Optimization Results dialog.

The report shows the following information on a POI by POI basis:

POI distance
Flag indicating the POI is in an end or interior stiffener panel
Shear demand Vu
Input
- User input web thickness
- User input stiffener spacing (note that the design optimization process will not automatically consider cross frame locations as stiffener locations.
- A flag indicating a user input longitudinal stiffener has been entered
- The computed resistance (Vn) based on user input
Required
- Final web thickness (tw) produced by the optimization process
- If a web must be stiffened, the required stiffener spacing (d0) based on the final web thickness. If the web thickness works as unstiffened, this field will be blank
- If a longitudinal stiffener is required relative to the top flange, the distance from the top flange to the stiffener (ds) will be shown. If no longitudinal stiffener is required, this field will be blank
- If a longitudinal stiffener is required relative to the bottom flange, the distance from the bottom flange to the stiffener (ds) will be shown. If no longitudinal stiffener is required, this field will be blank.
- The computed required resistance (ΦVn)

The following portion of the report is informational

Unstiffened (informational)
- This is the web thickness (tw) that will work for an unstiffened web
Trans Stiff (transversely stiffened)
- This is the computed web thickness (tw) based on using the maximum stiffener spacing for transversely stiffened girder (3D or 1.5D) shown in the next column
- This is the maximum allowable stiffener spacing 9d0) to qualify a web as stiffened when no longitudinal stiffener is present (computed as 3.0D for interior panels and 1.5D for exterior panels).
Long Stiff (longitudinally stiffened)
- This is the computed web thickness (tw) the based on using the maximum stiffener spacing for longitudinally stiffened girder (1.5D) in the next column.
- This is the maximum allowable stiffener spacing (d0) to qualify a web as stiffened when a longitudinal stiffener is present (computed as 1.5 D for both interior and exterior panels)