Seismic Fragility for a Masonry-Infilled RC (MIRC) Building Subjected to Liquefaction

Abstract

Historical earthquakes have documented that lateral spread and settlements are the most significant damages induced by soil liquefaction. Therefore, assessing its effects on structural performance has become a fundamental issue in seismic engineering. In this regard, the paper proposes to develop analytical fragility curves of a Masonry-Infilled RC (MIRC) structure subjected to liquefaction-induced damages. In order to reproduce the nonlinear cyclic behavior (dilation tendency and the increase in cyclic shear strength) due to liquefaction, nonlinear hysteretic materials and advanced plasticity models were applied. The findings herein obtained in terms of seismic fragility of the MIRC building subjected to liquefaction may be implemented as guidelines or code provisions.

Numerical Assessment of the Loading Factors Affecting Liquefaction-Induced Failure

“…Each BrickUP element is constructed with 20 nodes describing the solid translational degrees of freedom and 8 nodes (at the corners) that represent the fluid pressure. For each node, the first, second, and third degrees of freedom (DOF) represent solid displacement (u), and DOF 4 describes fluid pressure (p), which are recorded using the Node Recorder [50][51][52] at the corresponding integration points. The dimensions of the element increase from the centre of the model to the lateral boundaries, in order to guarantee convergence and avoid problems of instability.…”

“…In order to reproduce the infinite domain of the real soil, lateral boundaries were modelled with the penalty method to reproduce transmitting boundary conditions. A tolerance of 10 −4 was chosen as a compromise; it is large enough to ensure strong constraint conditions without introducing instability problems [50][51][52]. Base boundaries (depth of 38 m) are considered elastic to allow wave filtering.…”

“…In this context, liquefaction has been studied primarily through two different approaches: (1) laboratory tests, and (2) site observations of past earthquakes. Only a few contributions [47][48][49][50][51][52][53][54][55] proposed advanced numerical simulations that assess liquefaction potential. This paper targets this gap through focused numerical simulations that study the factors that affect liquefaction, specifically concentrating on those connected with the input motion characteristics.…”

Numerical Simulations of the Seismic Response of a RC Structure Resting on Liquefiable Soil

“…Moreover, the lateral nodes were constrained to simulate pure shear by applying period boundaries and to ensure free field conditions. At the lateral nodes, the penalty method (tolerance = 10 −4 ) was adopted to avoid problems with equation system conditions [15,16]. In addition, the soil deposit was simulated using the multi-surface plasticity constitutive model [17].…”

“…The rigid concrete slab was modelled by applying equal degrees of freedom to connect the nodes at the base of the columns with those of the soil domain [18]. In order to simulate the interface between the columns and the slab, horizontal rigid links were defined, following Forcellini [10,16]. The foundation slab was modelled elastically with an equivalent material that simulated concrete.…”