One-Dimensional Nonlinear Seismic Response Analysis Using Strength-Controlled Constitutive Models: The Case of the Leaning Tower of Pisa’s Subsoil

Abstract

Abstract:The Leaning Tower of Pisa was built between 1173 and 1360 and began to lean at the beginning of its construction. Extensive investigations to reveal the causes of the tilting only began in the early 20th century. Although few earthquakes have been recorded, there is a renewed interest in the seismic behavior of the tower triggered by the availability of new data and technologies. This paper highlights the influence of using new strength-controlled constitutive models in case of 1D nonlinear response analysis. This is an aspect that has been poorly investigated. Most of the computer codes currently available for nonlinear seismic response analysis (SRA) of soil use constitutive models able to capture small-strain behavior, but the large-strain shear strength is left uncontrolled. This can significantly affect the assessment of a 1-D response analysis and the Leaning Tower's subsoil can be useful for this study as it represents a well-documented and well-characterized site. After a geological and geotechnical description of the subsoil profile and a synthesis of available data, the seismic input is defined. One-dimensional SRAs were carried out by means of a computer code which considers an equivalent-linear soil modelling and two codes which assume nonlinear soil response and permit to use strength-controlled constitutive models. All the parameters were calibrated on the basis of the same soil data, therefore allowing for a direct comparison of the results.

Implementation and Use of a Mechanical Cone Penetration Test Database for Liquefaction Hazard Assessment of the Coastal Area of the Tuscany Region

“…where v and 'v are the total and effective geostatic stress, respectively; as is the free-field peak ground acceleration at the ground surface of the site of interest; g is the gravity; and rd is a stress reduction factor accounting for the distribution along depth of the shear stress amplitude (soil flexibility). On the whole, both as and rd should be inferred from site-specific true nonlinear seismic response analysis, accounting for soil strength [48][49][50]. This is difficult in the case of liquefiable deposits and out of the scope of the present paper.…”

Application of Conditional Mean Spectrum in Nonlinear Response History Analysis of Tall Buildings on Soft Soil

“…It should be noted that SHAKE2000 uses a one-dimensional equivalent linear site response analysis, in which the nonlinearity of soil deposits is taken into account by equivalent linear soil properties represented by stiffness and damping values adjusted through an iteration procedure until they are compatible with the effective strains induced by the earthquake loading in each soil layer. Due to assumptions in SHAKE2000, its accuracy is not perfect, and the accuracy of site response analysis could be improved by using nonlinear seismic response analysis of soil deposits [32][33][34][35].…”

Pile-Head Kinematic Bending of Fixed-Head Long Piles in Homogeneous and Layered Soils Considering Pile and Soil Material Nonlinearities in Case of Moderate to Strong Earthquake Motions

“…Single pile kinematic analysis with the code KIN SP is performed using as input the seismic response analysis (SRA) results obtained with the code ONDA [20,21,22]. SRAs with ONDA are carried out in the time domain and the nonlinear soil behaviour is accounted via the Ramberg-Osgood [23] constitutive model.…”