On the Distribution in Height of Base Shear Forces in Linear Static Analysis of Base-Isolated Structures

Abstract

Although base isolation is nowadays a well-established seismic-protection technique for both buildings and bridges, and several issues are still open and attract the interest of the research community. Among them, the formulation of computationally efficient and accurate analysis methods is a relevant aspect in structural design of seismic-isolated buildings. In fact, codes and guidelines currently in force in various parts of the world generally include the possibility for designers to utilize linear-elastic analysis methods based on equivalent linearization of the non-linear force-displacement response of isolators. This paper proposes a formula for defining the force distribution in height that should be considered in linear-static analyses to obtain a more accurate approximation of the actual structural response, supposedly simulated by means of non-linear time history analysis. To do that, it summarizes the results of a wide parametric analysis carried out on a batch of structures characterized by three different heights and various properties of base isolators. The reported results highlight that the equivalent static force distribution provided by both Italian and European codes tend to underestimate the actual seismic lateral forces acting on base-isolated buildings, whereas the inverted triangular distribution, proposed in various American codes and standards, is often conservative.

Buckling vs unilateral constraint for a multistable metamaterial element

“…Elastic metamaterials represent a blowing-up research field, finding crucial applications in vibration control, wave filtering and conditioning [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. However, meta-materials exhibit extraordinary mechanical properties even when subject to quasi-static loading, particularly when large deformations are involved [19,20,21,22,23,24,25,26]. Examples are numerous, including cloaking [27], extreme stiffness [28], shape morphing [29], auxeticity [30,31], negative thermal expansion [32], and multistable architectures [33,34,35,36,37].…”

Buckling versus unilateral constraint for a multistable metamaterial element

“…Elastic metamaterials represent a growing research field, finding crucial applications in vibration control, wave filtering and conditioning [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, metamaterials exhibit extraordinary mechanical properties even when subject to quasi-static loading, particularly when large deformations are involved [19][20][21][22][23][24][25][26]. Examples are numerous, including cloaking [27], extreme stiffness [28], shape morphing [29], auxeticity [30,31], negative thermal expansion [32] and multistable architectures [33][34][35][36][37].…”

Vertical distribution of seismic design load for seismically isolated buildings corresponding to diversity of seismic isolation devices

“…There have been many proposals for seismic load for designing SIBs, both in Japan and abroad 7‐9 . In addition, the main previous studies are summarized, and several standards and codes are compared 10 . The following equation, which expresses the amplification of seismic load according to building height as an inverted triangular distribution, is representative in foreign countries 11 :where : shear force of the SI interface, : weight of the ith story, and : height of ith story from foundations.…”

“…[7][8][9] In addition, the main previous studies are summarized, and several standards and codes are compared. 10 The following equation, which expresses the amplification of seismic load F i according to building height as an inverted triangular distribution, is representative in foreign countries 11 :…”