PSI - Issue 50

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Dmitry Parshin et al. / Procedia Structural Integrity 50 (2023) 320–326 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. Contact stress distribution evolvement for the structure constructed at a very low pace with pre-stretching additional material elements.

4.2. Brief discussion of results for stress controlling by structural elements pre-stretching If we do not have the opportunity to increase the pace of construction, we can influence the stress state of the structure being constructed by using pre-stretched structural elements. Let the forced initial hoop stress ,0   in the new material layers being added to the internal surface of the structure during the construction process be given depending on the radius  of the current layer to be added by the formula

(8)

k  ,0

 



where k is the dimensionless constant parameter considered as an influence factor in the process under modeling. Note that here selected linear dependence (8) provides a mathematically simple way to set non-zero initial hoop stresses in the used model by Manzhirov and Parshin (2015). We consider the slow construction mode, with 0.04  A , of the arched structure under modeling. In this mode of construction, the peak of positive stresses (peeling the structure from the foundation) does not decrease at all due to the addition of new material (see Fig. 1a). For this situation, we try to apply in the constructing process the elements pre-stretch according to formula (8) with setting 24  k in it. The results of calculations for such a construction variant are illustrated by the graphs in Fig. 2. As it can be seen, we manage to reduce the peeling (positive) contact stress steady-state level compared to the one that occurs in the situation shown in Fig. 1a. At the same time, it should be marked that the peeling stress will act now at the internal edge of the bottom surface, both at  t and during constructing. Besides, in the here discussed construction variant, there is no any decrease in the level of the initially encountered pressing (negative) stresses in the structure workliece part. If we increase the pre-stretching factor k to values greater than the value corresponding to Fig. 2, then the peak of steady-state positive contact stress in the workpiece part will be more reduced, but at the same time the analogous peak at the internal edge of the bottom will reach a greater value. Thus for the chosen constructing pace, the variant shown in Fig. 2 can be considered close to optimal from the view point of minimizing the level of peeling contact stresses acting at  t on the bottom surface of the constructed thin-walled arched structure. 5. Conclusions Large-sized structures experience the effects of gravity throughout the entire construction process. Consequently, taking into account these effects already in the final structure geometry cannot give correct ideas about the achieved stress-strain state of the structure. This is due to the fact that each new material element added to the structure has an additional impact on it with its own weight, causing additional strains in the entire structure. If, in a process of layerwise construction a large-sized structure on a foundation, there is a technological opportunity to influence the