Técnicas para evaluar los impactos ambientales

See also: CTRL,GRP,ULTI

SYST

Item Description Unit Default

TYPE Control option LT _*

* This input is not analyzed, the value is taken over from generation program. PAIN and AXIA only run with TALPA.

PROB Type of the analysis LT _LINE

LINE Linear analysis NONL Non-linear analysis

TH2 Analysis according to second or- der theory

TH3 Analysis according to thirdorder theory

TH3b Limited TH3

LIFT Analysis of plates with corners which are displaced upwards

ITER Number of iterations − 90

TOL Iteration tolerance − 0.001

The tolerance refers to the maximum load of analysis.

value multiplied with maximum nodal load generates the tolerance limit for residual forces

-value Absolute tolerance limit

TOL4 tolerance after 40 % iterations − - TOL8 tolerance after 80 % iterations − - FMAX Max. f value Crisfield method − 4.00

>_{0.1 or negative}

FMIN Min. f value Crisfield method > 0.1 − 0.25 EMAX Max. e value Crisfield method ≥ 0.0 − 0.60 EMIN Mini. e value Crisfield method ≤0.1 − -0.40 PLC Primary load case of the system − -

Item Description Unit Default FACV Factor for displacements of PLC − *

Default 1.0

for buckling eigenvalue analysis: for geometric nonlinear PLC: 1.0 otherwise for buckling: 0.0

VMAX Factor for imperfection − -

NMAT Yield criteria for QUAD and BRIC elements LT _NO

YES Yield criteria are used. NO Yield criteria are not used.

STOR Geometry update LT _NO

CHAM Magnification calculation in connection with program CSM

− -

- no magnification

1.0 magnification calculation

Non-linear analyses are not possible with the basic version of program. Further explanations to PROB:

LINE linear analysis NONL non-linear analysis

non-linear springs

tension cut off for QUAD elements non-linear pile bedding

non-linear halfspace contact material non-linearities:

- stress-strain curves for springs, beams, cables and trusses (re- quires the recordNSTR)

- concrete and steel rule for QUAD elements (SYST NMAT YES is additionally necessary)

- yield criteria for BRIC volume elements (SYST NMAT YES is additionally necessary)

TH2 = NONL + analysis according to the second-order theory for calcu- lation of columns and frames according to the second-order theory (pi-delta)

analog mode to STAR2 (the normal ASE iteration method with resid- ual forces is used for TH3 orCTRLITER 3)

TH3 = NONL + geometrically non-linear analysis contains TH2 and ad- ditionally the effects of the geometrical system modification, e.g. snape through, length modification for big deformations, behaviour after buckling

On TH2-TH3 Difference see Theoretical Background - Beam Ele- ment

TH3b = NONL + TH2 + effects of the geometrical system modification only for cables, trusses and springs (CTRL SPRI) with kinematic constraint. Beams and QUAD elements are used only according to the second-order theory.

LIFT Analysis of plates with corners which are displaced upwards A non- linear analysis is started, at which also fixed supports and elastic edges can be displaced upwards due to tension; seeCTRLSOFT Examples:

SYST PROB LINE: Input file

ASE introduction ase1_overview.dat

BEMESS slab design bemess6_design.dat

CSM prestressed bridge csm31_design.dat

SYST PROB NONL: Input file

Spring work law a1_spring_overview.dat

Beam Ship impact plastic ase_nstr_pld_pile_crash.dat

Quad concrete cracked a1_introduction_example.dat

Bric tunneling ase14_tunnel_3d.dat

SYST PROB TH2: Input file

Beam overturning ase11_girder_overturning.dat

Beam column cracked aseaqb_1_column_cracked.dat

SYST PROB TH3: Input file

Overview examples geo-nonl ase_geo_nonl_overview.dat

Suspension bridge suspension_bridge_formfinding.dat

Cable sag ase5_cable_trestle.dat

Quad geometric nonlinear ase9_quad_euler_beam.dat

Quad shell buckling ase13_shell_buckling.dat

SYST PROB LINE: Input file

Quad web buckling webblecbuckling.dat

Quad membranes tennis.dat

Bric buckling bric_beul.dat

Summary of all example overviews: Example overview see

Work laws ->Work law input

Copy loads ->LCC

Mass conversion ->MASS

Creep and shrinkage ->KRIE

Nonlinear effects ->SYST PROB ...

Quad nonlinear ->NMAT YES

Membranes ->MEMB

Ultimate load iteration ->TRAG

Incremental launching ->TAKT

Contact Moving Springs ->MOVS

Dynamic time steps ->STEP

Halfspace analysis ->HASE

Plot - diagrams ->PLOT

An overview over all examples can be found in TEDDY menue file - examples in folder ASE-english. Then look further e.g. to folder ’nonlinear_quad’. Or you go over the SOFiSTiK installation folder to

c:/program...sofistik/2014/ANALYSIS_30/ase.dat/english/nonlinear_quad Further input remarks:

The value of PLC defines a global primary load case. This is used subsequent- ly as default for the primary load case of all group inputs. Furthermore the displacements of the primary load case are added then and only then to the dis- placements of the current load case, if the PLC has been defined in the SYST input. In the case of geometrical non-linear analysis the stiffness is calculated for the deformed structure.

A predeformation with PLC and FACV effects the internal forces moments only for PROB TH3, see Chapter 2: Non-linear Analyses and Chapter

5: example Buckling Mode Shapes in Supercritical Region. The applica- tion of a non-stressed predeformation is explained in the school example

ase9_quad_euler_beam.dat.

The stresses of the primary load case are used withGRPFACL=FACP=1. If the loads of the primary load case are applied simultaneously, then the system is in equilibrium and no additional displacements arise (if no changes are made in the system).

If a primary load case with TH3 is defined for an eigenvalue determination, one obtains the eigenfrequencies of the system under the stresses of the primary load case (accompanying eigenvalue analysis).

With GRP FACL=FACP=0 the deformation of a load case can be defined here as non-stressed scaled predeformation (see Chapter 5: example Buckling Mode Shapes in Supercritical Region).

The inputs ITER to EMIN are evaluated only for non-linear analysis. Such an analysis is allowed only for a single load case.

Buckling eigenvalues on a deformed structure can be requested with explicit SYST...FACV 1.0.

Explanations to the non-linear iteration method: Residual forces

New displacements and thus stresses are determined after ev- ery iteration step. It is checked, whether plasticising, cracks or any other non-linear effects have occurred at any elements. The plasticized elements generate different nodal loads compared to those of the linear analysis. These nodal loads which were gen- erated by the elements are not anymore in equilibrium with the external nodal loads (after the first iteration step). The remaining residual forces are applied as additional loading during the nex- t iteration step. Additional deformations and a new stress state which in general is closer to equilibrium result. The maximum residual force is printed for every iteration. If all residual forces should be output, this can be controlled with the option ECHO

RESI.

Graphical control of the residual forces

If an iteration ends with residual forces, a picture of the residual forces can be requested in the program WING with NODE SV.

Since unbalanced residual forces are stored as supported reac- tions, the problem zone can be localized with that. Here the real support areas should not be printed. Often, it is advisable to fade out the real support areas with BOX and to draw only the interior of the structure.

Tolerance limit of the iteration

The tolerance limit can be defined with the record SYST. Here the reference value is the largest nodal value which is available in the system. E.g. for a maximum nodal load of 200 kN the tolerance limit for the residual forces is = 200 ·0.001 = 0.2 kN (for TOL=0.001). In this case all loads of the system are used including the inherent stress nodal loads of the elements.

The tolerance for non-linear analysis can be input also absolutely with SYST PROB NONL TOL -value.

Example: With the input SYST PROB NONL TOL -0.5 the itera- tion is interrupted, if the maximum residual force is smaller than the value 0.5 kN.

Iteration method

The default method for problems according to the second-order theory is the Linesearch method with the update of the tangen- tial stiffness (see record CTRL). The load increment is reduced here internally according to the available residual forces. If an iteration step proceeds into the right direction, i.e. in the direc- tion of an energy minimum, then a new tangential stiffness which enhances the further iteration’s behaviour is generated, if neces- sary. Cracked elements are considered here also with a reduced stiffness. The Crisfield method is the default (CTRL ITER 0) for non-linear calculations according to the first-order theory. For convergence problems the user should attempt also the in each case other method (CTRLITER 0 orCTRLITER 1).

Variation of iteration factors

For convergence difficulties an improvement of the convergence behaviour can be achieved often via reduction of the maximum f value, e.g. FMAX 1.5. If the system still not converges, F- MAX can be reduced until 0.7. However, many iteration steps are needed then.

of the convergence modifies the displacement increments of the current and of the last iteration step with the two factors f and e. f values which become alternately larger and smaller than 1.0 are an indication of serious problems. The method can be influ- enced in such cases by specifying maximum and minimum val- ues of factors. A negative value for ITER switches off this method completely. By contrast, it may occur for tensile failure of stiff ele- ments that the residual forces change very slowly. Here it is use- ful to select large values for e and f (e.g. EMIN = -9999., EMAX = 9999. , FMAX = 1000.). Generally applicable recommendations can not be given here. It has been observed, however, that the limit values of e should be defined essentially more generously, even if FMAX has to be limited.

The values FMAX to EMIN are increasingly limited during the iteration process. Thereby the convergence is improved for many iterations.

The FMAX value is decreased automatically during the iteration process with the input of a negative value for FMAX.

Failed foundation and tensile springs

For analyses without consideration of tensile support reactions (non-linear foun- dation or springs) the basic foundation values should not be defined too large, because the program reduces gradually these values until the foundation fails. For too large initial values for the foundation the iteration converges extremely slowly.

For tensile failure in large regions the residual forces of the non-linear analysis can not be redistributed anymore. The iteration becomes divergent. Additional elements with a small stiffness parallel to the failing ones may be helpful here. Imperfection

The imperfection can be scaled automatically with the item VMAX. The inputs -1, -2, -3 for SYST ... FACV control then the direction of the scaling, if desired. SYST PLC 101 FACV - VMAX 0.05 defines the imperfection of the primary load case 101 with a three-dimensional deformation of 5 cm.

SYST PLC 101 FACV -1 VMAX 0.5 defines the primary load case 101 with a maximum imperfection u-X of |5 cm|. All other deformations are scaled with the same factor.

SYST PLC 101 FACV -1 VMAX -0.05 as before, however, the imperfection figure is defined with a negative sign.

Failure Mode Shapes

With a special control it is possible to get a more precise iteration process for the failure mode shapes in ASE. An analysis according to the second-order and third-order theory does not converge in many cases and it is unknown which fail- ure mechanism will occur. At first a smaller stable load step should be calculated in advance. Then the following input should be startet:

PROG ASE

HEAD delivers the failure in the iterations load cases 9001-9009.

$ Method: $

$ - new total stiffness after every step, $

$ - then continuation of the calculation without manipulation of the residual $

$ force $

CTRL ITER 2 W2 1 $ new total stiffness after every step $

SYST PROB TH3 ITER -30 PLC 15 $ !!minus!! -30 $

LC 201 FACT ... $ Factor, that will cause failure $

In the same way dynamic eigen mode shapes with the last stable load case may give an information about failure problems, because the critical natural vibration shapes in the natural frequency are clearly smaller with increasing load. See example ase9_quad_euler_beam.dat

Geometry-Update

With SYST STOR the system which was displaced with the displacements of the load case PLC can be stored with the updated nodal coordinates. A calculation does not occur then.

SYST STOR=YES: The new local coordinate systems of the QUAD elements are twisted by the rotations of the load case PLC. They, however, keep the di- rection defined in the input. Beam lengths are nor updated for loading .

SYST STOR=NEW: The local coordinate systems of the QUAD elements are defined again, despite their definition in the input. Beam lengths are updated for loading .

SYST STOR=XX,YY,ZZ and NEGX,NEGY,NEGZ: The direction of the local x axis is preset for the new installation of the coordinate system of the elements, cf. program SOFIMSHA/SOFIMSHC. Beam lengths are updated for loading. STOR=NEW to STOR=NEGZ acts only to QUAD elements. The local coordinate systems of beams are twisted generally with the PLC displacements.

Caution:

date. Therefore the data base must be saved absolutely before! With the input STOR=NEW to STOR=NEGZ all other results are extinguished too, because the local directions are twisted. With the input STOR=YES it is possible to use the old stresses via the recordGRP, if no beam elements are available.

With SYST STOR UZ only the z displacements are corrected. For the x or y displacements are also possible STOR UX and STOR UY.

In document TRANSPENINSULAR-SANTA ROSALIÍTA (página 100-105)