PSI - Issue 44

Stefano Bracchi et al. / Procedia Structural Integrity 44 (2023) 442–449 Stefano Bracchi, Maria Rota, Andrea Penna / Structural Integrity Procedia 00 (2022) 000–000

448

7

i tot , ∆ ∆ − ∆ wall i , N N

N

i tot ,

(1)

= η

where ΔN i,wall is the variation of axial load on the i

th pier belonging to the single wall model, and ΔN

i,tot is the

same quantity, this time calculated on the model of the entire building. Fig. 6 shows the results obtained for the West wall of Building 2, in terms of values of η as a function of flange length (from zero to half of the length of the transversal walls of the real building). Increasing the flange length, the value of η tends to zero, reaching a value approximately equal to zero for a flange’s length equal to half of the length of transversal wall of the entire building when the refined macroelements of Penna et al. (2014) and Bracchi et al. (2021) are used. The same behavior is not taking place with the bilinear element, having larger value of residual η .

Bilinear

Penna et al. (2014)

Bracchi et al. (2021)

Fig. 6. Efficiency parameter for West wall (Building 2 – STD geometry – negative direction).

As regards the second case study, characterized by the presence of openings in the transversal direction, this time the reference length of the flange is assumed equal to the length of the transversal wall in the entire building up to the adjacent opening (i.e. equal to 1.44 m for the considered building). Fig. 6 shows the results obtained for West wall of Building 3 with MOD geometry and analyzed in the negative direction in terms of values of η as a function of flange’s length. Also in this case, increasing the flange’s length, the η values tend to the zero; moreover, the values of η corresponding to the length of 1.44 m are sufficiently near to zero when using the two macroelements, and significantly different when using the bilinear element. Differently from the first case study, this time the residual difference is larger (around 20%).

Bilinear

Penna et al. (2014)

Bracchi et al. (2021)

Fig. 7. Efficiency parameter for West wall (Building 3 – MOD geometry – negative direction).

5. Conclusions This paper presents a comparison among nonlinear static analyses performed on single walls and entire buildings and adopting different modelling strategies, both code-compliant and refined, with the aim of studying the single wall analysis, which is commonly used when flexible floors are present. First, a strategy to carry out nonlinear static analyses of single walls was defined, with the goal of finding a modelling strategy leading to results fully consistent to ones obtained for the same walls analyzed as belonging to an entire building. Then, two case study buildings, derived from URM prototypes subjected to shake table tests, were considered. Two configurations, fully symmetric