Nonlinear Dynamic Behaviour of Hollow Piles Based on Axial Harmonic Loading (original) (raw)
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Nonlinear Field Response of Piles Under Horizontal Harmonic Excitations
Proceedings of International Structural Engineering and Construction
Harmonic excitation of pile foundation is a typical dynamic phenomenon occur during machine vibration. In many cases, it has been found that the horizontal excitations are the critical ones which governs the design for machine-based pile foundations. In order to comprehend the horizontal frequency-amplitude responses of pile foundation under various harmonic excitation forces, forced vibration tests on several sets of small-scale single and pile groups have been carried out. According to the test results, there are two resonant peaks within the operational frequency range shown by the dynamic frequency-amplitude responses, where the first peak is found to be more dominant as compared to the second peak. Additionally, as resonant frequencies are lowered and resonant amplitudes grow for an increase in excitation forces, the response curves demonstrate the nonlinear patterns of pile groups. The basic dynamic characteristics of all soil-pile setups are found to be similar to each other....
Response of Tapered Piles under Lateral Harmonic Vibrations
International Journal of Geomate
This paper presents a new method for analysis tapered piles under lateral harmonic vibration. The behavior of tapered piles is assumed to be as elastic and linear. The soil consists of some elastic horizontal layers that they are homogeneous, isotropic, and linearly visco-elastic. The pile is divided to some segments and the differential equation for a given desirable segment is obtained and solved. Then the dynamic complex stiffness parameters are derived for the pile head. Parametric studies have been performed to investigate the influence of pile geometry, soil properties, and loading details on pile-soil system amplitudes. It has been found that under lateral harmonic vibrations, with increasing the pile taper angle, the resonant amplitude decreases. In addition, it has been concluded that under lateral harmonic vibrations, a tapered pile experiences lower amplitude than a cylindrical pile of the same length and material volume.
Response of tapered piles to axial harmonic loading
Canadian Geotechnical Journal, 2008
This paper presents a new mathematical approach for the analysis of a harmonically vibrating, linear, elastic, tapered pile. The soil consists of a number of horizontal elastic strata that are homogeneous, isotropic, and linearly viscoelastic. The governing differential equation for an arbitrary pile segment is obtained and solved. The solution starts from the pile toe and ends up with the pile head. It will be shown that when the taper angle is increased, the resonant amplitudes of piles decrease. It will also be demonstrated that the resonance amplitudes and resonant frequencies of the floating tapered pile and a uniform pile of the same volume and length vary slightly. However, the resonant amplitude of an end-bearing tapered pile is significantly less than that of the equivalent uniform pile. It will generally be concluded that the use of tapered piles subjected to axial harmonic vibrations is superior to the use of cylindrical piles of the same length and volume. This is very a...
Dynamic Analysis of Piles under Lateral Harmonic Vibration
2010
This paper presents a new mathematical approach for the analysis of harmonically vibrating horizontal, linear, elastic uniform pile. The soil properties may vary from layer to layer. No separation is allowed at the soil-pile interface. The pile is modeled as a number of cylindrical segments connected by rigid nodes. The length of each segment is chosen such that the effects of the soil inhomogenity are accounted for. The governing differential equation for an arbitrary pile segment is obtained and solved. According to the pile support types such as pinned, fixed and free conditions, first an arbitrary appropriate value for either toe force, bending moment, rotation, or displacement is assumed. The governing differential equation is then solved from the lower pile segment to the top one. The stiffness of the whole pile-soil system will then be computed. It is shown that the slenderness ratio, the stiffness ratio and toe fixity are the governing parameters affecting the stiffness of the soil-pile system. The new analytical model, which is verified using existing numerical and analytical solutions, is more efficient than the equivalent numerical solutions for example finite eminent methods.
Analysis of pile groups under vertical harmonic vibration
Computers and Geotechnics, 2005
In this paper, a simple method is proposed for the analysis of vertically loaded pile groups under dynamic conditions. The method makes use of the closed-form stiffness matrices derived by Kausel and Roësset [Kausel E, Roësset JM. Stiffness matrices for layered soils. Bull Seismol Soc Am 1981;71(6):1743-61] to simulate the response of layered soils. These matrices are incorporated in a calculation procedure that is essentially analytical. Further computational advantages of the procedure derive from the fact that, under the simplified assumptions of free-field soil displacements and symmetry of the pile-soil interaction forces, the analysis of a pile group may be achieved simply using the solution for the single pile. Moreover, the soil layering effect is reliably accounted for. The accuracy of the method is assessed by comparing the results with those deduced from other existing theoretical solutions. The method is also used to predict the experimental measurements from dynamic tests on pile groups documented in literature.
Nonlinear response of pile-soil system under harmonic lateral loading
2012
This paper presents a new model to analyze the nonlinear interaction between a vertical cylindrical pile subjected to lateral harmonic loading and its embedment soil. The pile toe is either pinned or clamped to idealize its support on bedrock. The soil mass is decomposed into an inner soil zone around the pile where soil nonlinearity is portrayed by a hyperbolic model and a linearly elastic outer soil zone. A numerical solution is obtained using the finite difference method. The results obtained by the suggested approach are then compared with those derived from an analytical approach developed by Nogami and Novak (1977).
ABSTRUCT Foundations supporting reciprocating engines, radar towers, turbines, large electric motors, and generators, etc. are subject to vibrations caused by unbalanced machine forces as well as the static weight of the machine. If these vibrations are excessive, they may damage the machine or cause it not to function properly. In the case of block foundation, if changes in size and mass of the foundation do not lead to a satisfactory design, a pile foundation may be used. In this study, the dynamic response of piles and pile Groups in dry sand is investigated experimentally. The analysis involves the displacement response under harmonic excitation. In addition, a numerical modeling by using finite element method with a three-dimensional formulation is adopted to simulate the experimental model. The results of the numerical model showed that a good agreement is achieved between the predicted dynamic response and that measured from the experimental model.
2010
Piles are normally constructed in groups such that they are located in the vicinity of each other. As a result, the response of piles is different from that of an isolated pile. In this paper, the interaction between two piles with unequal lengths in the group is investigated using an analytical solution. The elastic theory model and dynamic winkler model are use to characterise vertical isolated prismatic piles subjected to vertical harmonic vibrations. The results obtained for pile-soil-pile interaction from this solution account for unequal lengths for the two piles. In addition, it has been found that upon loading the first pile (called source pile), the presence of the neighbouring pile (called receiver pile) is important, leading to lesser ground movement at the receiver pile head location. The results also indicate that pile-pile spacing and the soil type are important. The general finding in this research indicates that ignoring the presence of the second pile in the calculation of the interaction between a pair of piles can significantly overestimates the pile-soil-pile interaction, resulting in underestimation of the group stiffness.
Dynamic Pile-Soil-Pile Interaction, Part I: Analysis of Axial Vibration
Simple methods of analysis are developed for computing the dynamic steady-state axial response of floating pile groups embedded in homogeneous and non-homogeneous soil deposits. Physically-motivated approximations are introduced to account for the interaction between two individual piles. It is found that such an interaction arises chiefly from the 'interference' of wave fields originating along each pile shaft and spreading outward. For homogeneous deposits the wave fronts originating at an individual pile are cylindrical and the interaction is essentially independent of pile flexibility and slenderness. For non-homogeneous deposits the wave fronts are non-cylindrical and ray-theory approximations are invoked to derive pile flexibility-dependent interaction functions.
Investigation of Non-Uniform Pile Behaviour Under Torsional Harmonic Vibration
2010
Pile foundations for machines and structures are often subjected to horizontal or vertical harmonic vibrations. However, in some situations, piles also experience torsional harmonic vibrations. While there are some research work on tapered piles imposed to horizontal or vertical harmonic vibrations, the response of such piles till now is lacking. In this study, the elasto-dynamic theory has been used to derive the governing differential equation on a tapered pile experiencing torsional harmonic vibration. In this approach, the pile is assumed the pile has circular cross sectional area and consists of elastic material. It is further assumed that there is sufficient connection between the pile and the soil, so that the slippage cannot occur at the pile-soil contact surface. By using the developed method, the effect on the pile dynamic torsion amplitudes of the taper angle has been investigated. It has been found that the twist angle of the pile decreases with increasing the taper angle while the length and volume of the pile is kept constant. This reveals that the use of tapered piles leads to a better performance for foundations compared with the case of using straight-sided piles of the same length and volume.