5. Solving the mechanical problem#

The final step is to fix the mechanical problem. It takes place differently depending on the method used and the taking into account of phasing. This chapter details how to proceed with each of the choices, specifying the loads to include (keyword EXCIT) when calling CALC_PRECONT or STAT_NON_LINE.

5.1. Adherent cables tensioned with CALC_PRECONT#

Three scenarios are possible:

The user wants to tension simultaneously all the pretension cables as well as instant loading, without further loading beforehand. In this case, you only need to call the CALC_PRECONT macro command once. The load consists of the boundary conditions and any instant loads (no load concerning the cables). Under the keyword CABLE_BP, we’ll include all DEFI_CABLE_BP concepts (see scenario 3 in the appendix).

The user wants to do calculations before putting the cables into tension. In this case, it is appropriate to: * or to deactivate the cables in the model by assigning them the law of behavior RELATION =” SANS “under the keyword COMPORTEMENTde STAT_NON_LINE. In this case, the stiffness of the cables is zero. It is also essential to add kinematic relationships between cable and concrete to the loads (load obtained by writing AFFE_CHAR_MECA (RELA_CINE_BP =_F (RELA_CINE =” OUI “)))) (see scenario 1 and 3 in the appendix). * or not to include the cables in the model used to do the calculations before the cables are tensioned (which is more tedious since you have to work with 2 models).

The user wants to tension the cables sequently. In this case, call CALC_PRECONT as many times as necessary. CABLE_BPcontiendra the DEFI_CABLE_BPassociés concepts to the cables we are in the process of extending during this call to CALC_PRECONT. CABLE_BP_INACTIFcontiendra those that we want to extend later. In this way, it is the macro-command that is responsible for assigning a SANSà law of behavior to these cables and including the kinematic links associated with these same cables. For loading, it is a question of always including boundary conditions as well as any instant loads. From the second call to CALC_PRECONT, it is necessary to include in addition, the kinematic links linked to the cables already energized in the previous steps (see scenario 1 in the Annex).

In any case, for the STAT_NON_LINE that follow the tension of the cables, it is important not to forget all the kinematic links related to the cables.

5.2. Adherent cables tensioned with STAT_NON_LINE#

If the user does not want to use CALC_PRECONT to tension pretension cables, it is possible to use the old cable tension method despite its drawbacks [R7.01.02].

The voltage is carried out simply by including in the loads the concept AFFE_CHAR_MECA defined by RELA_CINE_BP = F (RELA_CINE = “OUI”, SIGM_BPEL =” OUI “). At the end of this calculation, the voltage in the cables is no longer equal to that prescribed by BPEL. However, it is possible to determine a multiplicative coefficient (of the order of about ten percent) to be applied to the initial tensions applied to the cables (at the level of the declaration of operator DEFI_CABLE_BP) making it possible to globally compensate for the losses due to instantaneous deformation of the structure. Once the control file has been modified by these correction coefficients, the modeling of the prestress cables is completed.

Attention, in the case of a sequence of STAT_NON_LINE, starting from the second call, it is advisable to include in the load only the kinematic relationships and not the tension in the cables, otherwise this tension will be added to each calculation (see scenario 2 in the annex). This therefore requires creating a second AFFE_CHAR_MECA with the operand RELA_CINE_BP = F (RELA_CINE = “OUI”, SIGM_BPEL =” NON “) (cf. scenario 2 in the Appendix).

5.3. Non-adherent cables tensioned with CALC_PRECONT#

The instructions are identical to the case of adherent cables. However, two specificities should be noted.

  1. The law of behavior for the cable is no longer simply elastic but:

    • RELATION = “KIT_CG”, RELATION_KIT =( “ELAS”, “CABLE_GAINE_FROT”),

“ELAS”, can be replaced by “SANS” when the cable should not be used as a step in the calculation.

  • Once the cables have been put in tension, the load must be added, which blocks the sliding of the anchor nodes (see § 4.6.2). It is advisable to rely on test case SSNV164D.