Usfos Introduction

USFOS Analysis (Ultimate Strength for Framed Offshore Structures) -

A nonlinear numerical tool mainly for the analysis of space frames Pushover analysis

1

Outline • • • • •

Features of USFOS USFOS input file preparation Running analysis & post-processing Examples: simply supported beam Examples: 2D frame and jacket

2

Basic features • Ultimate Strength for Framed Offshore Structures • Beam, Shell, Solid Elements one finite element is sufficient for one physical member based on element formulation

• Nonlinearities: geometry, material and boundary conditions • Consistent Unit System N (force), m (length) N (force), mm (length)

E in Pa E in MPa 3

Add-on features • • • •

Joint Capacity Checks Spud Can Soil-Structure Interaction Hydrodynamic Loading

4

USFOS Reality Engineering

File Types Involved in And Analysis Structural input filemodel.fem

Text output file (res.out). Contains general print and error messages

Usfos

Xact

(“engine”)

(Graphical Interface)

USFOS analysis control file (named f ex head.fem)

Result Database for XACT. Name: res.raf

INPUT

OUTPUT 5

Installing software • Download from http://www.usfos.com/

6

Installing software • Replace the key file at C:\Program Files\USFOS\bin

7

Open software • Open from start  all programs  USFOS  USFOS GUI

8

Run software (1) • Open analysis control

9

Run software (2) • Input example file by clicking • Example files are available in C:\Program Files\USFOS\examples • You can edit the example file by clicking

Head_orig.fem model.fem Left empty Name the result file in the same folder

• Save the file before running. Attention: In PC cluster, drive C is protected, users can’t write any files on it. But you can write files on desktop. So before running the software, you have to copy the example files to desktop and name your result file in the same folder on the desktop. If you forget this for the first time, restart USFOS.

10

Analysis results View the node numbers and element numbers

View the animation

Try this by yourself Change load step

Drag with the left button or the right button to translate or rotate

11

P

Δ

P

A1

3 Δ

z

2B

y x

l

Step1: model structure Step2: add loading condition 12

USFOS input file - Structural file Node

Element

• Global Coordinate • Boundary Condition

• Material • Cross Section data

'

Node ID X Y Z Boundary code NODE 1 .000 .000 .000 1 1 1 1 0 1 NODE 2 10.000 .000 .000 0 1 1 1 0 1 NODE 3 5.000 .000 .000 ' ……….. ' Elem ID np1 np2 material geom lcoor BEAM 1 1 3 1 1 1 BEAM 2 3 2 1 1 1 ' ……….. ' VecID dx dy dz UNITVEC 1 .000 .000 1.000 ' ……….. ' Geom ID Do Thick PIPE 1 .24070 .0050 ' Geom ID H T-web W-top T-top W-bot T-bot IHPROFIL 5 0.4250 0.0400 0.4250 0.0400 0.8405 0.0250 ' ……….. ' matno. E v yield density therm MISOIEP 1 210E9 0.3 358E6 7.85E3 1.4E-5

Boundary Condition: x,y,z,rx,ry,rz; 0:free; 1:fixed;

Structure

Coordinate system

1

Define nodes and boundary conditions Define elements Define local z-axis coord. of beam elements Define cross section data Define material properties

3

2 13

COORDINATE SYSTEM

z 2 1

y Local Coordinate

x

Global Coordinate

14

COORDINATE SYSTEM • The global coordinate system is defined as a right-hand Cartesian system. • Local coordinate system for the beam element is also defined in right-

hand Cartesian system : the local x-axis is from the first node (i) towards the second node (j); the local y- and z-axis are perpendicular to the local x-axis.

• UNITVEC in the model file defines the local z-axis in terms of global coordinates. This vector should not coincide with the local x-axis. • If not defined, the default local z-axis is parallel to the global (X,Z) plane.

15

USFOS input file - Control file -Static load • Load case: pressure, CF, etc Usually in structural file • Load Magnitude • Load control parameters: Lfact Minstp nstep etc • Control node displacement • Other information: Joint check Saved information P z

A1

3 Δ

y

2B

x

l

16

USFOS input file - Control file -Static load P z

A1

3 Δ

y

2B

x

l ' load case NODELOAD 1

node ID load intensity 3 0.0000E+00 0.0000E+00 -1.0000E+04

' CUSFOS '

nloads npostp mxpstp mxpdis 10 10 1 1.00 lcomb lfact mxld nstep minstp 1 0.1 1 10 0.1

' CNODES '

ncnods 1 nodex idof dfact 3 3 -1

Define a concentrated load Load control for static analysis Different lines refer to the sequence of load applications

Specify the control displacement of the structure 17

• Running USFOS analysis • If the results are not satisfactory, go back to analysis control to adjust the parameters

18

19

Output file

• Binary output file: *.raf file : opened in Xact • Text output file: *.out file : records the structural input and every incremental steps. *_status.text file: records the occurrence of yielding, plastic hinges, and member buckling in the analysis.

20

.out file •

OUT file summarizes the structural data both in terms of user definition as well as the USFOS internal treatment of some of the input (e.g. spring properties). The .OUT also summarizes the numerical results in each step, as exemplified in the following. The symbols at the end of element indicates 0: a yield hinge is inserted +: position checked for plasticity *: plastic hinge removed at element mid-span. Internally, the element is divided into two sub elements. 0-0-0: plastic tension failure. The axial tension has reached the plastic capacity and a membrane element is inserted. ELEM 1 2

ES

Node1

2 -1.00(-1.00) 1 0.00( 0.00)

--------

NODE 1 2 TOTAL:

Midspan

Node2

-0.49(-0.36) -0.49(-0.36)

0.00( 0.00) -1.00(-1.00)

G L O B A L

X-for -3.806E-10 0.000E+00 -3.806E-10

R E A C T I O N

Y-for

Z-for

0.000E+00 0.000E+00 0.000E+00

1.948E+04 1.948E+04 3.897E+04

+---+---O O---+---+ F O R C E S

X-mom

Y-mom

--------

Z-mom

0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 , Vector_Sum XY : 3.806E-10

21

_status.text file • The _status.text file lists the nonlinear events during the analysis: first yielding, plastic hinges and buckling. • The time step at which the nonlinear event occurs provides a hint to view the fringe plots. --

Yielding Status (hinge introduced)

Elem ID 1 2

Position node 2 node 1 --

Elem ID 1 2

Position node 2 node 1

Cross sect. utilization 0.79 0.79

--

Comb No 1 1

Step No 50 50

Load level 2.90 2.90

Plastic hinge Status (fully developed) --

Cross sect. utilization 1.00 1.00

Comb No 1 1

Step No 101 101

Load level 3.77 3.77

22

2D frame analysis(1) 1.

2. 3.

4.

5.

Input the existing control file and structure file. Check the structure file . Press F1 to add comments to an existing command. Press F2 to select and insert another command. For more information, go to help\USFOS input commands and search.

For command description

View the model without running

23

2D frame analysis(2) 1. 2. 3. 4.

5.

Check the control file . Check the control parameters Press F1 to add comments. Press F2 to select and insert another command. For more information, go to help\USFOS input commands and search.

24

2D frame analysis(3)

To choose a nodal/element result, click here and use CTRL + Left click the member you want to see

25

2D frame analysis(4) 1. 2.

Left empty

The default joint is rigid joint. CHJOINT: the capacity of the tubular joint will be checked!

26

2D frame analysis(5)-MSL Due to deformation limitation of MSL just click OK

Right click

Load factor times the basic load

27

HELP Help is also available online at http://www.usfos.com/, where you can find: -Online manuals -Related publications -USFOS setup download

28

Jacket(1) • Wave loading can be interpreted as static loading or dynamic loading . • For static loading USFOS will step through the actual wave and identify the worst wave position(the position causing the highest base shear or overturning moment) • For dynamic loading, some may be implemented: Marine growth; buoyancy; current…… 29

Jacket(2) • Identify the worst wave phase to be used in the static pushover analysis.

30

Jacket(3) 1. 2.

Find the load level Find the baseshear and overturning moment

31