Compose cross-section data model
Through this design function the pipeline data model is extended with additional data necessary to perform the cross-section calculations.
The function elaborates in a similar way as the sub-functions of design function 3 the data from the polygon shaped data lines along the selected axis, which are attached to the mid-sections of the elements where the cross-section calculations might be performed in the next sub-function. The cross-section model may be considered as an extension of the soil model as it has been defined in sub-function 3.2. If there is no soil there cannot exist overburden loads. If there is soil there shall be an overburden load, but this load may be specified =0. Cross-section data provided are collected in the output data table CROSDAT.
When settlements are specified and the pipeline does not follow due to its stiffness or when - without settlements - the pipeline moves upwards, so that a gap results beneath the pipeline, and the existing top (soil) load exceeds the downward soil reaction from output table SOILREA, additional bending moments, reactions, displacements and possibly support forces resulting from the loading difference are collected in output tables ADDCROS and ADDSUP, if the Loading redistribution has been applied. If not, output tables ADDCROS and ADDSUP remain empty. Resulting spans with a gap under the pipe are reported in table SPANS.
In case the R module is available, the function has the option of redistribution of cross-sectional deformations. The successive cross-sections at mid-elements are loaded each with the calculated soil reaction force from the relative pipe/soil displacement together with the overburden load specified in SOILNB and possibly TOPLOAD.
The soil loading over the circumference is split into 4 main directions:
|2.||a subsoil load at the pipe bottom acting upward, balancing the top soil load,|
|3.||a horizontal soil supporting load (from LAMBDA and SOILSUP) acting both at the left hand side and at the right hand side of the section in the inward direction,|
|4.||a soil reaction R-LAT resulting from the displacement of the pipe cross-section relative to the soil (from SOILREA and ADDCROS).|
Each load component has its own specific angle of action on the cross-section. The subsoil load angle is specified in the input table SUPANG. The top soil load angle is 180 degrees, the horizontal load angle 120 degrees. The load angle B for R-LAT depends on the reaction angle PHI-LAT:
B = value from SUPANG if 225deg < PHI-LAT < 315deg,
B=120 deg if 135deg < PHI-LAT < 225deg or 315deg < PHI-LAT < 45deg,
B=180 deg if 45deg < PHI-LAT < 135deg.
These loads together deform the cross-section. In case 'Ovalisation Redistribution' is disabled (None), the successive cross-sections deform independently. In case that option is enabled (Allowed), the redistribution of deformations due to the shell behaviour of coupled adjoining cross-sections is taken into account. The redistribution function is different for 2nd, 3rd and 4th harmonic deformations, depending on the characteristic wave length of the disturbance. If the element length is equal to or larger than the specific characteristic length, the program generates a finer element distribution internally in order to be able to perform the redistribution.
Redistribution results of TOPLOAD loads together with the other loadings as taken into account in the W-REDIS table, are provided in the T-REDIS table. Redistribution results of bend ovalisations are provided in table B-REDIS, if the 'Section Model' option has been set to 'Ovalising'.
The redistribution is performed for all cross-sections, independent of the choice of elements to be calculated in design function 6.2.
If all wall bending stresses are ignored by means of table SWEIGH, redistribution has no effect and is useless.
H6103, last changed: 14/09/2016