1,721,174 research outputs found
Kinematic Bending Moments in Square Pile Groups
No full textThis paper describes kinematic seismic interaction analysis of square pile groups in homogeneous soil deposits, focusing on bending
moments induced by the transient motion. Analyses were performed by means of a three-dimensional (3D) numerical procedure able to
account for both pile–soil–pile interaction and radiation damping. The seismic motion was defined by an artificial accelerogram at the outcropping
bedrock, and one-dimensional (1D) propagation analyses were performed to define the free-field motion within the deposits. An extensive
parametric study was conducted to determine the effects of different variables, such as the soil properties, the bedrock location, the number of
piles, and the pile spacing, on the dynamic response of pile-group foundations. Bending moments obtained from the analyses of the pile group,
both at the pile head and at the interface separating soil layers, were normalized with respect to the single-pile bending moments, allowing for
the proposal of a new design formula for the estimation of the kinematic bending moments in the most stressed pile of the group, starting from
the knowledge of the single-pile response. The proposed formula was used, in conjunction with some simplified approaches that allow estimation
of the single-pile response, to evaluate bending moments in the analyzed pile groups. The adequacy of the formula for design purposes is
demonstrated
L'EFFETTO DEL CORDOLO SULLA RISPOSTA CINEMATICA E SULLE FUNZIONI DI IMPEDENZA DI FONDAZIONI MONOPALO
No full text
Dynamic behavior of soil-foundation-structure systems subjected to scour
No full textEarthquake and scouring are the leading causes of bridge failure worldwide, resulting not only in casualties and fatalities but also in enormous societal and economic losses. A great number of bridges in earthquake-prone countries cross rivers and have shallow foundations, which renders them highly vulnerable to the combined effects of earthquake and flood-induced scour. Thus, the research on the dynamic response of bridges with shallow foundations under scour and earthquake hazards is timely and imperative. This study investigates the problem through the development of a numerical model for evaluating the effect of scour on the impedance functions of a massless rigid strip foundation resting on a homogenous elastic half-space. The developed impedance functions are then used in an extensive parametric study analyzing the changes of the fundamental frequency of bridge piers for different combinations of the geometrical and mechanical properties of the soil-structure-foundation system. The study results shed light on the effects of scour on the dynamic properties and fundamental frequency of vibration of bridges with shallow foundations and have important implications on the development of inverse techniques for scour identification based on the evaluation of the changes in the bridge modal properties
Soil-structure interaction in the seismic response of the isolated overcrossings of the A14 Motorway section Cattolica-Senigallia
No full textStatic equivalent method for the kinematic interaction analysis of pile foundations
No full textThis work presents a simplified procedure for the evaluation of the kinematic stress resultants in single piles
subjected to earthquake soil displacements. The procedure is applicable to single piles embedded in
homogeneous as well as horizontally layered soil profiles overlaying a rigid formation. By neglecting radiation
damping the evaluation of the effects induced in the piles by the propagation of seismic waves in the soil is
studied by means of a static equivalent procedure, without the use of dynamic analyses. Piles are modelled as
elastic beams on Winkler restraints and are pushed by the earthquake soil displacements provided by a response
spectrum analysis of the soil profile oscillating. The soil is assumed to be homogeneous with constant shear
modulus and density and to behave elastically. A validation of the method is carried out comparing results with
those furnished by more sophisticated dynamic soil-pile interaction analyses
Risposta Sismica di Pile da Ponte Fondate su Gruppi di Pali Inclinati.
No full textQuesto lavoro indaga la risposta sismica di pile da ponte fondate su gruppi di pali inclinati tenendo conto dell’interazione terreno-struttura e considerando gruppi di pali con differente geometria e diverse inclinazione dei pali. Le analisi di interazione sono eseguite ricorrendo al metodo per sottostrutture ed utilizzando, per le analisi di interazione cinematica delle palificate a pali inclinati, un modello numerico 3D agli elementi finiti sviluppato dagli autori in cui la non linearità del terreno è tenuta in conto con un modello lineare equivalente. I risultati delle analisi permettono di esprimere delle prime considerazioni circa l'influenza della configurazione della palificata e dell'inclinazione dei pali sul comportamento strutturale delle pile sulla risposta delle fondazioni
Dynamic performance of a full-scale micropile group: Relevance of nonlinear behaviour of the soil adjacent to micropiles
Full text linkAn extensive experimental in-situ campaign of dynamic tests carried out on a full-scale 2 x 2 group of inclined injected micropiles in alluvial soils is described in this paper. The campaign includes ambient vibration and impact load tests to investigate the dynamic behaviour of the soil-micropile system in the small strain range, and forced vibration tests to investigate the performance of the system in the nonlinear field. Accelerometers and geophones are adopted to acquire the dynamic response on the cap and the soil nerby the cap, while strain gauges are installed along the shaft of one micropile to capture the local curvatures and deflections. The influence of the micropile inclination on the translational and rotational behaviour of the group is evaluated. Moreover, the evolution of degradation phenomena such as the gap opening and slippage at the soil-micropile interface and the radial cracking of soil surrounding micropiles, are recognized, critically commenting the relevant effects on the fundamental frequencies and damping ratios of the system
Soil-structure interaction effects on the seismic response of multi-span viaducts
Full text linkThe paper focuses on the effects of soil-structure interaction in the seismic response of multi-span viaducts on pile foundations. Analyses are performed by means of the substructure approach: the soil-foundation systems are studied in the frequency domain to obtain the foundation input motion and the dynamic impedance functions; inertial interaction analyses are carried out in the time domain accounting for the material nonlinear behaviour.
Suitable lumped parameter models are introduced to simulate the frequency dependent behaviour of the soilfoundation system. A specific procedure for selecting and scaling real ground motions is proposed and used for the definition of the spatial seismic input. The seismic response of bridges on compliant base is compared with that obtained from fixed base analyses discussing the significance of soil-structure interaction effects
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