API RP 2A-WSD (21th, 2007)

API RP 2A-WSD (21th, 2007) edition - recommended practice for planning, designing and constructing fixed offshore platforms released December 2000 (Errata and supplement 3, October 2007).

The standard supports calculations for circular tubes only.

To add API RP WSD Standard execute Standard - API - API RP 2A-WSD (21st, October 2007) from the main menu. Alternatively, use the Standard context menu:

It is possible to edit Safety Factors and Selection.

Safety Factors are set to Standard default values. It is not necessary to change them.

According to the calculation procedure a Beam Length for Y and Z direction is required. Data from The Beam Member Finder is used automatically:

If beam members are not recognized press .

Formulas (3.3.1-5) and (3.3.1-6) should be applied to cylindrical piles. By default, the calculations are skipped and a user should define when a member is treated as a pile.

API_WSD_add_el_char

Formulas of the API RP 2A WSD standard use Yield Stress from materials. It is important to set this value for each material. Standard checks if the values are defined for all materials:

Material_with_yield_and_tensile

If count > 0, then press to edit Yield Stress:

Edit_yield_stress

By default, selection is set to Circular Tube Shapes. If not all circular members should be checked, then the selection can be modified.

When all settings are defined, press OK to create standard.

Standards_menu_api_WSD

Standard contains 6 checks: 1 and 2 geometrical pipe dimensions and limits, 2-5 - stress checks for different directions, 6 - overall check (axial and bending).

Result of Overall check is Utilization Factor = Stress / Allowable Stress. If Utilization Factor is < 1, the check is OK.

The value 12345678 is used when the calculations cannot be performed due to geometrical limitations or calculations are out of scope.

Joint Check

Joint Check Check is a part of the API RP 2A-WSD standard. To create a new Joint check in Custom Standard perform Checks - Add - Joint Check WSD (2st, 2000) from context menu:

joint_check

Press to automatically highlight single Connection selected in the table.

Maximum distance from joint nodes of one connection on the chord - include joints that are formed by multiple nodes:

It is possible to set the Custom distance or use the distance that equals D/4 where D - chord diameter so that each connection has its own distance to check.

Angle between braces treated as in one plane - defines allowable angle between braces of one connection that are located in different planes:

Chord maximum curvature angle - Not always chord elements form a straight line. To include inclination in a chord default angle = 3 degree is used.

Set Connection ID and press Navigate to display connection in the table.

Joint check is based on connections. Each connection is a set of elements near joint node (see Joints Finder). Connections consists of Chord and braces. Brace contains only 1 element with ID defined in brackets (#). Connection can contain braces from the both sides of the chord. Information is displayed in second brackets: U- upper braces; L- lower braces;

Press to find all connections of the model. Window with connections that are recommended to be checked manually will be displayed:

Connection has to be checked when:

- D1 = D2 = d3 = d4, T1 = T2 = t3 = t4

- D1 = D2 = d4, T1 = T2 = t4, d3 > D1

- D1 = D2 = d3 = d4, T1 = T2 = t4, t3 > T1 according to the following image

- Add new connection manually:

- edit selected connection;

- preview highlight selected connection;

- preview only selected connection;

- remove selected connection;

- plot all connections values in colors + Labels with IDs;

- show information about all connections;

- hide information of all connections.

Edit Connection

Joint_edit_connection_iso

Pick Chord elements and braces (each brace consist of 1 element) and press to preview connection properties.

- swap chord and brace selections

Press to preview and highlight connection in Simcenter.

Set Braces Overlapping - open window to set the overlapping brace. Is enabled only if one brace overlaps another one in connection:

Joint_set_overlapping

Resistance Coef. - AISC resistance factor for the weld (Φsh).

Set Overlapped (Yes) / (No) - set to the selected braces if they are overlapped.

Press to open check table for calculations:

Joint_check_table

Show Results:

Utilization factors only - axial and bending capacities, combined load, overlapping and can capacities;

Intermediate Results - geometrical factors, brace forces, allowable stresses + utilization factors;

All results - - Intermediate results + calculation factors (chord/brace dimensions, fiber stresses, effective length, Qa, overlapping percentage, etc.)

Display Parameters in:

Rows - display parameters in rows and connections info in column headers;

Columns - display parameters in column headers and connections information in rows.

Filter and sort results using Filter / Sort By control.

- Plot Axial force and Projected force of all braces of selected connections:

- Plot gaps of all braces of selected connections:

- Plot braces types of selected connections:

Press to open criteria window:

Set plot options, define selection and and press :

display plot with all the settings;

- display plot with current view settings (ignore view from plot options);

Note: The results are displayed only for braces.

Press to open an expand flow table for check:

Joint_check_expand_flow_table_api

Show:

Show Load Results - display results for each selected load per brace.

Show Min/Max - display only minimum and maximum results among the loads for each brace.

Show Load Results and Min/Max - combines two previous options.

Skip rows without maximum - do not display loads that do not contain any extreme results among all parameters.

Filter and sort results using Filter / Sort By control.

Connections are taken from selection (one element is enough to include connection).

Press Fill Table to display the results.

- set resistance coefficient for overlapped braces:

Select Is Critical and press Apply to set if all selected braces are critical or non-critical.

Fill Ub and press Apply to set Ub parameter to all selected braces.

Fill Resistance a factor and press Apply to set a factor to all selected braces.

Note: Ub and Resistance factor are applied only to critical braces.

- set if use can calculations (section 14.3.5) and effective length:

Joint_check_set_connection_parameter

All overlapped braces are displayed in the list with the related connection ID.

Fill Resistance coef. and press Apply to set the coefficient to all selected braces.

If no overlapped braces are found, a message will be displayed:

Joint_check_overlap not found

- display a window to set Load transfer (section E.3.4 in standard) for braces of connections which contain:

Joint_check set_brace_load_transfer.

If load transfer is set to "No", formula (E.3.4-1a) will not be applied to the calculations, even if it matches the conditions.

It is possible to change the Effective Length manually. Set value to Effective Length field and press Apply button to set value to the selected braces.

According to standard, joint types are defined by the following rules:

Joint type is based on type of loading. By checking if forces of connection are balanced joint types are classified on K, TY and X (Cross).

K - tension and compression loads are balanced.

TY - tension or compression load goes as a shear force in a chord.

X (Cross) - Connection has to contain braces from the both sides to check on a cross joint. If balanced forces of all braces on one side and balanced forces of all braces of other side are equal then all braces are classified as X (Cross).

Interpolation - the order of joint type recognition is following: K -> X (Cross) -> TY. Each brace can have all 3 types of the joint type taken as a percentage of the axial load of a brace to a summation of all braces loads.

Note: If brace has 0 force joint type for such brace is set to TY.