The paper presents a parametric study on the seismic response of bridge piers founded on gravity caissons. Despite the wide use of caissons in bridge engineering, until a few years ago this ...foundation typology has been less investigated than piles and shallow foundations in both static and dynamic field. In most of the published studies, the seismic design of bridge piers was carried out without accounting for soil-structure interaction or by means of an uncoupled approach in which the superstructure was solved independently from the soil-caisson subsystem. In this study, coupled systems made of soil, caisson, pier and deck were analyzed in the time domain by a 3D finite element approach, considering rigid and massive caissons embedded in linear viscoelastic soils. In addition to unravelling the contribution of kinematic and inertial interaction to the total response of the caisson-bridge-pier systems, the study focuses on a particular aspect of kinematic interaction, overlooked in practical design and in most of previous studies, represented by the kinematic bending arising in the bridge pier due to the pier-to-deck joint rigidity. For some critical combinations of soil compliance, caisson geometry, pier height and input motion characteristics, the pier-deck constraint could induce kinematic bending moments in the pier as important as the inertial ones. A closed-form equation was finally proposed to predict the maximum kinematic moment in the bridge pier as a function of the key model parameters identified through the parametric study.
•3D direct analyses of caisson-supported bridge piers on viscoelastic soil were performed in the time domain.•Bending moments arising in bridge piers due to Soil-Structure-Interaction (SSI) were computed.•The kinematic constraint imposed at pier head by the bridge deck was accounted for.•Kinematic bending moments in bridge piers could be as important as the inertial ones.•A closed-form equation to compute the kinematic bending moments in bridge piers was suggested.
Advances in dynamic numerical analyses and investigation techniques nowadays allow to simulate the seismic behavior of structures through increasingly detailed models, calibrated on in-situ dynamic ...surveys. The different factors affecting the calibration procedure should, however, be well identified and properly represented in the model. Usually various forms of interaction may influence the building response (i.e. soil-structure, surrounding buildings, etc.) and so their single contribution on the overall response of the coupled system should properly be ascertained. In the paper, the results of numerical analyses and on-site dynamic identification are compared, to quantify the role exerted by the structure, the foundation, the soil and the adjacent buildings on the overall dynamic behavior of the highest tower in Napoli (Italy). The experimental frequencies and the corresponding deformed shapes were reproduced through a simplified model on springs, simulating the soil-foundation impedance. The inferred dynamic behavior of the tower was observed to be significantly influenced by the restraint exerted from adjacent buildings and by the interaction with the soil.
The results were corroborated by the more refined predictions provided by a complete 3D Finite Difference model of soil, foundation and structure. In addition, a frequency detected from field records, which has not been identified in previous analyses on fixed base models, was found to be associated to the rocking response of the foundation.
•Equations of the dynamic impedance of flexible foundations are reported;•Results of uncoupled and coupled soil-structure analyses are compared to field records;•The effect of adjacent buildings and foundation embedment and flexibility is studied;•A novel procedure is proposed for the dynamic identification of coupled SFS models;•The frequency associated to the foundation rocking is recognized.
In the geotechnical field, the risk related to slope instabilities or collapse of geotechnical structures are increasingly being faced by early warning systems, capable of: (1) predicting the ...incipient collapse based on the interpretation of a continuous monitoring of the structure and (2) spreading alarm promptly to reduce people exposure. Compared with structural approaches, early warning systems have two important advantages: a faster, simpler and less expensive implementation and environmental compatibility. Past experience indicates that vulnerability of earth dams is generally low under both static and seismic loading conditions. In spite of this, earth dams are characterized by a high-risk level, due to the high exposure factor. Nowadays, the application of early warning systems to dams is fully supported by the technological progress achieved in the telecommunication field, since it is possible to install and automate recordings and transmission of all physical variables significant to check dam safety: accelerations, displacements, pore-water pressures, total stresses, seepage flows. A considerable lack still arises in the predictive models for interpreting monitoring data and providing indicators on dam safety soon after a strong earthquake. The present work illustrates the basic concepts of an earthquake early warning (EEW) system for earth dams and the main features that should characterize a predictive model to such a scope. An application to a real case is finally provided, enhancing the role played by each monitored physical variable for the aims of EEW.
The dynamic identification of a historical masonry palace located in Benevento (Italy) has been carried out. The case study is representative of many buildings located in historic Italian centres. ...Since the building has been instrumented by the Department of Civil Protection with a permanent dynamic monitoring system, some of the recorded data, acquired in various operating conditions have been analysed with basic instruments of the Operational Modal Analysis in order to identify the main eingenfrequencies and vibration modes of the structure. The experimental results have been compared to the numerical outcomes provided by a detailed three-dimensional Finite Element (FE) model of the building where Soil–Structure Interaction (SSI) has been taken into account. The comparison of experimental vs. numerical frequencies and vibration modes of the palace evidenced the role exerted by the subsoil on the dynamic response of the building.
•Vibration frequencies of a masonry building detected by in-situ dynamic monitoring.•Numerical predictions against experimental data are presented.•SSI on the main natural frequencies of a masonry building is quantified.
The paper illustrates theoretical and experimental procedures adopted to characterize the seismic response of earth dams by performance-based criteria. The study refers to a real case, the Camastra ...Dam, a zoned earth dam with vertical clay core, placed in a highly seismic zone of Southern Italy. At first, the analysis objectives have been identified along with the physical quantities needed to achieve them for characterizing dam seismic performance. A theoretical approach, consistent with the identified analysis objectives, has been later selected. The adopted approach is based on continuum mechanics and accounts for coupling between soil skeleton and pore water phase. It is also able to describe the main features of soil response under cyclic loading conditions since it implements an advanced constitutive law for the soil skeleton. Big effort has been paid to the mechanical characterization of the dam materials. In addition to data coming from the interpretation of the laboratory tests performed at the time of dam construction, in situ tests (SASW, Down Hole, DMT) have been recently carried out on the embankment and foundation soils and interpreted consistently with the requirements of the selected theoretical model. Preliminarily, the static stages of the dam lifetime have been numerically simulated to reproduce the behaviour observed in terms of cross-arm settlements and pore water pressures, in order to obtain or verify some soil parameters and initialize the state variables for the simulation of the seismic stages. A seismological study of the dam site provided the expected seismic scenarios in terms of time histories of acceleration, needed as input for the dynamic analyses. The seismic response of the Camastra Dam was finally investigated and discussed in the light of performance-based criteria.
Chronic encapsulated intracerebral hematoma (CEIH) is a rare solid mass characterized by the presence of a fibrotic capsule that can present a variety of signs and symptoms due to the mass effect and ...hydrocephalus. It may be caused by post-traumatic or spontaneous bleeding as related to an adjacent aneurysm, angiomas or neoplasms. Differential diagnosis must be applied in order for it to mimic neoplasm or a vascular malformation. Several cases of CEIH have been reported but only a few of them have an intraventricular localization. A forensic autopsy of a 50-year-old male who died suddenly while driving is discussed. Gross analysis, histology and toxicology were performed and a CEIH of the right lateral ventricle was found in a case of acute coronary death.
In recent years kinematic interaction of piled foundations under seismic loading has been extensively researched from both an experimental and a numerical viewpoint. With regard to numerical aspects, ...most literature studies implement simplified constitutive models to describe soil and pile behaviour despite current availability of sophisticated constitutive models for both materials. The use of advanced constitutive models is limited in practice due to the difficulty in calibrating several constitutive parameters and the high computation demand which is generally required, particularly if a 3D continuum approach is selected for the analysis. To overcome some of the difficulties above and achieve a better understanding on kinematic response of piles under strong earthquakes, the capability of an advanced but still user-friendly kinematic hardening constitutive soil model has been investigated. The model derives from the classical Von Mises failure criterion with the addition of isotropic and kinematic hardening components to better represent soil response under cyclic loading.
Dynamic 3D finite element (f.e.) analyses were performed in the time domain through a simple scheme of a single pile embedded in a soil deposit made of two cohesive layers. The parametric study elucidates the role of soil nonlinearity (stiffness degradation, hysteresis, soil plasticization) on pile kinematic bending response in respect of the adopted input signal, mobilized transient and permanent shear strain developed in the soil layers. For some accelerometric inputs the diffuse plasticization of the soil around the pile leads to compute high kinematic bending moments especially in soil deposits with the upper layer made of low-plasticity index soft clay. Finally, pile nonlinearity has also been considered by implementing bending moment-pile curvature relationships typical of reinforced-concrete piles.
•Kinematic pile bending is explored accounting for soil and pile nonlinearity.•Soil nonlinearity is modelled by an advanced kinematic hardening constitutive law.•Comparisons with previous literature data are presented.•Soil nonlinearity affects more ground motion than pile-soil interplay.•Pile yielding and failure may be achieved in layered subsoil.
The paper deals with the influence of past loading history on the seismic response of earth dams by interpreting the static and dynamic behaviour of a real case-history: the El Infiernillo Dam. ...Settlements, pore water pressures and accelerations measured during different stages of the dam lifetime have been interpreted by using a coupled dynamic approach derived from the
u–
p formulation of the Biot consolidation theory. The approach is solved numerically with the finite element method. The study firstly investigates the effectiveness of the adopted model to predict the observed dam behaviour. Following, a parametric study has been performed to examine what effects, additional loading histories, have on the prediction of seismic-induced freeboard loss. The study brings out soil hardening effects induced by the past seismic history, and investigates to what extent earth dam response to a given earthquake may be affected by previous seismic events.
The paper illustrates and compares simplified approaches to interpret the mechanisms of damage observed on rigid bodies in the cemetery of Amatrice, after the main shock (August 24, 2016, MW=6.0) of ...the Central Italy earthquake. The final goal of the work is to link the observed movements of the fallen objects to specific characteristics of the ground motion occurred at the specific site.
A multidisciplinary approach for assessing the seismic vulnerability of heritage masonry buildings is described throughout the paper. The procedure is applied to a specific case study that represents ...a very common typology of masonry building in Italy. The seismic vulnerability of the examined building was assessed after the following: (a) historical investigation about the building and the surrounding area, (b) detailed geometrical relieves, (c) identification of materials by means of surveys and literature indications, (d) dynamic in-situ tests, (e) foundation soil characterization, (f) dynamic identification of the structure by means of a refined Finite Element (FE) model. After these steps, the FE model was used to assess the safety level of the building by means of non-linear static analyses according to the provisions of Eurocode 8 and estimate of the q-factor. Some parametric studies were also carried out by means of both linear dynamic and non-linear static analyses.
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