PSI - Issue 61

Adil Ziraoui et al. / Procedia Structural Integrity 61 (2024) 171–179 Adil Ziraoui et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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As far as material characteristics are concerned, our choice of values is based on a combination of practical considerations and compliance with current design standards. The compressive strength of concrete, noted f ck , was set at 25 MPa. This value was selected to reflect a strength typical of concrete used in civil engineering structures, thus ensuring a certain robustness while remaining in line with current practice. The yield strength of steel reinforcement, noted F e , was set at 400 MPa. This value is in line with quality standards for steels used in reinforced concrete structures. High yield strength steel reinforcement is essential to provide the necessary resistance to tensile loads in the structure, which is particularly important in seismic conditions.

Fig. 2. View in three dimensions of the 8 - storey and 10-storey fixed-base structures that were taken into consideration for the analysis.

Table 1. The dimensions of the carrier system element. Model

8-Storey 300 x 300 300 x 400

10-Storey 300 x 300 300 x 400

Beam Elements (mm × mm) Column Elements (mm × mm)

Slab Elements (mm)

150

150

The modeling features are clearly demonstrated in Figure 3. In this representation, the essential components of the LRB isolator, namely the elastomeric rubber material and the lead core, have been modeled as a non-linear spring of zero length, as shown in Figure 3a. In parallel, the cover plate was modeled as a rigid element. This modeling approach enables us to accurately represent the behavior of the LRB isolation system in seismic analysis. Indeed, the behavior of the LRB isolator can ideally be characterized by a bi-linear stiffness model based on three essential parameters: initial stiffness (K e ), yield strength (F 1 ), and post-yield stiffness (K p ). These parameters, as shown in Figure 3b, provide a complete and accurate description of the isolator's response to various loads and deformations during an earthquake. Initial stiffness (K e ) reflects the strength of the isolator prior to any significant deformation, while yield strength (F 1 ) represents the limit at which the isolator begins to undergo elastic deformation. Beyond this limit, the isolator's behavior changes, and this is where post-strain stiffness (K p ) comes into play. The latter characterizes the isolator's response when plastic deformation occurs (Chen et al. 2009, Mazza et al. 2018). The use of a bi-linear stiffness model with these three key parameters provides a realistic representation of the behavior of the LRB isolator under varying seismic loads. This modeling is essential for understanding how the isolator reacts to seismic shocks and how it contributes to reducing the seismic response of buildings, which is at the heart of our study.