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Lateral Loads (lateral + load)
Selected AbstractsA modulus-multiplier approach for non-linear analysis of laterally loaded pile groupsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2007Chia-Cheng Fan Abstract A modulus-multiplier approach, which applies a reduction factor to the modulus of single pile p,y curves to account for the group effect, is presented for analysing the response of each individual pile in a laterally loaded pile group with any geometric arrangement based on non-linear pile,soil,pile interaction. The pile,soil,pile interaction is conducted using a 3D non-linear finite element approach. The interaction effect between piles under various loading directions is investigated in this paper. Group effects can be neglected at a pile spacing of 9 times the pile diameter for piles along the direction of the lateral load and at a pile spacing of 6 times the pile diameter for piles normal to the direction of loading. The modulus multipliers for a pair of piles are developed as a function of pile spacing for departure angle of 0, 90, and 180sup>/sup> with respect to the loading direction. The procedure proposed for computing the response of any individual pile within a pile group is verified using two well-documented full-scale pile load tests. Copyright © 2006 John Wiley & Sons, Ltd. [source] Biomechanical aspects of marginal bone resorption around osseointegrated implants: considerations based on a three-dimensional finite element analysisCLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2004Eriko Kitamura Abstract Objectives: Although bone loss around implants is reported as a complication when it progresses uncontrolled, resorption does not always lead to implant loss, but may be the result of biomechanical adaptation to stress. To verify this hypothesis, a three-dimensional finite element analysis was performed and the influence of marginal bone resorption amount and shape on stress in the bone and implant was investigated. Material and methods: A total of nine bone models with an implant were created: a non-resorption (Base) model and eight variations, in which three different resorption depths were combined with pure vertical or conical (vertical,horizontal) resorption. Axial and buccolingual forces were applied independently to the occlusal node at the center of the superstructure. Results: Regardless of load direction, bone stresses were higher in the pure vertical resorption (A) models than in the Base model, and increased with resorption depth. However, cortical bone stress was much lower in the conical resorption models than in both the Base and A models of the same resorption depth. An opposite tendency was observed in the cancellous bone under buccolingual load. Under buccolingual load, highest stress in the implant increased linearly with the resorption depth for all the models and its location approached the void existing below the abutment screw. Conclusions: The results of this analysis suggest that a certain amount of conical resorption may be the result of biomechanical adaptation of bone to stress. However, as bone resorption progresses, the increasing stresses in the cancellous bone and implant under lateral load may result in implant failure. Résumé Bien que la perte osseuse autour des implants soit considérée comme une complication quand elle progresse de manière incontrôlée, la résoption ne se termine pas toujours par la perte de l'implant, mais peut être le résultat de l'adaptation biomécanique au stress. Pour vérifier cette hypothèse, une analyse d'éléments finis en trois dimensions a été effectuée et l'influence de l'aspect et de la quantité de résorption osseuse marginale au stress dans l'os et l'implant a été analysée. Neuf modèles osseux avec un implant ont été créés : un modèle (Base) sans résorption et huit variations dans lesquelles trois profondeurs de résorption différentes ont été combinées avec des résorptions verticales ou coniques (verticale-horizontale). Des forces axiales et vestibulo-linguales ont été appliquées de manière indépendante en occlusal au centre de la superstructure. Quelle que soit la direction de la charge, les stress osseux étaient plus importants dans la résorption verticale pure (A) que dans le modèle de base et augmentaient avec la profondeur de résorption. Cependant, le stress osseux cortical était beaucoup plus faible dans les modèles à résorption conique que dans les modèles Base et A de même profondeur de résorption. Une tendance opposée était observée dans l'os spongieux sous charge vestibulo-linguale. Sous charge vestibulo-linguale, le stress le plus important dans l'implant augmentait linéairement avec la profondeur de résorption pour tous les modèles et sa localisation approchait l'espace existant en-dessous du pilier. Les résultats de cette analyse suggèrent qu'une certaine quantité de résorption conique pourrait être le résultat d'une adaptation biomécanique au stress osseux. Cependant, quand la résorption osseuse progresse les stress s'amplifiant dans l'os spongieux et au niveau de l'implant sous une force latérale peuvent résulter en un échec implantaire. Zusammenfassung Ziel: Auch wenn ein Knochenverlust um Implantate, der unkontrolliert fortschreitet, als Komplikation beschrieben wird, führen solche Resorptionen nicht gezwungenermassen zu einem Implantatverlust. Sie könnten aber Ausdruck einer biomechanischen Adaptation auf die Belastungen sein. Um diese Hypothese zu überprüfen, führte man eine dreidimensionale "Finite-Element"-Analyse durch. Man untersuchte die Zusammenhänge von Ausmass und Form der marginalen Knochenresorption und den entstehenden Kräften im Knochen und Implantat. Material und Methode: Die Arbeitsgrundlage waren 9 Modelle mit je einem Implantat: eines diente als Kontrolle (ohne Resorptionserscheinungen), die anderen acht zeigten drei verschiedene Resortionstiefen in Kombination mit rein vertikalen oder konischen (vertiko-horizontal) Defektformen. Dann liess man, unabhängig von der Okklusionsgestaltung, axiale und buccolinguale Kräfte auf die Mitte der Suprastruktur auftreffen. Resultate: Unabhängig von der Belastungsrichtung war die Knochenbelastung bei den rein vertikalen Resorptionsmodellen (A) grösser als beim Kontrollmodell und sie nahmen mit der Tiefe der Resorption zu. Die Belastung im kortikalen Knochen war aber in den Modellen mit konischen Resorptionen viel geringer als beim Kontrollmodell und den A-Modellen mit denselben Resorptionstiefen. Eine genau umgekehrte Tendenz konnte man im spongiösen Knochen unter buccolingualer Belastung feststellen.Bei einer buccolingualen Belastung nahm die Belastungsspitze beim Implantat bei allen Modellen linear mit der Resorptionstiefe zu und der Ort dieser Belastungsspitze lag im Bereich des Leerraumes genau unterhalb der Schraube des Sekundärteils. Zusammenfassung: Die Resultate dieser Analyse lassen vermuten, dass die konische Resorption bis zu einem gewissen Ausmass das Resultat einer biomechanischen Adaptation auf die Belastung des Knochens ist. Wenn aber die Knochenresorption fortschreitet, können die zunehmenden Belastungen im spongiösen Knochen und im Implantat bei einer lateralen Belastung zum Implantatmisserfolg führen. Resumen Objetivos: Aunque la pérdida de hueso alrededor de los implantes se informa como una complicación cuando progresa incontroladamente, la reabsorción no siempre lleva a la pérdida del implante, pero puede ser el resultado de la adaptación biomecánica al estrés. Para verificar esta hipótesis, se llevó a cabo un análisis tridimensional de elementos finitos y se investigó la influencia de la cantidad de reabsorción de hueso marginal y la forma en el estrés en el hueso y el implante. Material y métodos: Se crearon un total de 9 modelos de hueso con un implante: Un modelo sin reabsorción (Base) y 8 variaciones, el las que se combinaron tres diferentes profundidades de reabsorción con reabsorciones verticales o cónicas puras (vertical,horizontal). Se aplicaron fuerzas axiales y bucolinguales independientemente al nodo oclusal en el centro de la superestructura. Resultados: A pesar de la dirección de la carga, los estreses óseos fueron más altos en los modelos de reabsorción vertical pura (A) que en los modelos Base y se incrementaron con la profundidad de reabsorción. De todos modos, el estrés cortical fue mucho menor en los modelos de reabsorción cónica que en los modelos Base y A con la misma profundidad de reabsorción. Se observó una tendencia opuesta en el hueso esponjoso bajo carga bucolingual. Bajo carga bucolingual, el estrés mas alto en el implante se incrementó linealmente con la profundidad de reabsorción para todos los modelos y su localización se aproximó al espacio existente bajo el tornillo del pilar. Conclusión: Los resultados de este análisis sugieren que cierta cantidad de reabsorción cónica puede resultar de la adaptación biomecánica del hueso al estrés. De todos modos, al progresar la reabsorción ósea, los estrés crecientes en el hueso esponjoso y en el implante bajo carga lateral puede resultar en un fracaso del implante. [source] Numerical Model for Biaxial Earthquake Response of Reinforced ConcreteCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2007Cemalettin Dönmez The model is tested using data from two types of experiments with reinforced concrete elements: (1) elements subjected to varying pseudo-static biaxial lateral loads and (2) elements that responded biaxially to simulated earthquake motions. The goal for the model was not only to help determine the absolute maxima for earthquake response but also to enable calculation of the entire waveform, including the ranges of low- and moderate-amplitude response. The comparisons of measured and calculated results and sensitivity of the proposed model to variations in the input parameters are discussed. The output was found to be insensitive to the changes in input parameters related to concrete and sensitive to input parameters related to reinforcing steel. The results of the calculations were tested using experimental data. [source] Shaking table model test on Shanghai World Financial Center TowerEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2007Xilin Lu Abstract The height of 101-storey Shanghai World Financial Center Tower is 492m above ground making it possible the tallest building in the world when completed. Three parallel structural systems including mega-frame structure, reinforced concrete and braced steel services core and outrigger trusses, are combined to resist vertical and lateral loads. The building could be classified as a vertically irregular structure due to a number of stiffened and transfer stories in the building. Complexities related to structural system layout are mainly exhibited in the design of services core, mega-diagonals and outrigger trusses. According to Chinese Code, the height 190 m of the building clearly exceeds the stipulated maximum height of for a composite frame/reinforced concrete core building. The aspect ratio of height to width also exceeds the stipulated limit of 7 for seismic design intensity 7. A 1/50 scaled model is made and tested on shaking table under a series of one and two-dimensional base excitations with gradually increasing acceleration amplitudes. This paper presents the dynamic characteristics, the seismic responses and the failure mechanism of the structure. The test results demonstrate that the structural system is a good solution to withstand earthquakes. The inter-storey drift and the overall behaviour meet the requirements of Chinese Design Code. Furthermore, weak positions under seldom-occurred earthquakes of seismic design intensity 8 are found based on the visible damages on the testing model, and some corresponding suggestions are proposed for the engineering design of the structure under extremely strong earthquake. Copyright © 2006 John Wiley & Sons, Ltd. [source] A displacement-based seismic design procedure for RC buildings and comparison with EC8EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2001T. B. Panagiotakos Abstract A procedure for displacement-based seismic design (DBD) of reinforced concrete buildings is described and applied to a 4-storey test structure. The essential elements of the design procedure are: (a) proportioning of members for gravity loads; (b) estimation of peak inelastic member deformation demands in the so-designed structure due to the design (,life-safety') earthquake; (c) revision of reinforcement and final detailing of members to meet these inelastic deformation demands; (d) capacity design of members and joints in shear. Additional but non-essential steps between (a) and (b) are: (i) proportioning of members for the ULS against lateral loads, such as wind or a serviceability (,immediate occupancy') earthquake; and (ii) capacity design of columns in flexure at joints. Inelastic deformation demands in step (b) are estimated from an elastic analysis using secant-to-yield member stiffnesses. Empirical expressions for the deformation capacity of RC elements are used for the final proportioning of elements to meet the inelastic deformation demands. The procedure is applied to one side of a 4-storey test structure that includes a coupled wall and a two-bay frame. The other side is designed and detailed according to Eurocode 8. Major differences result in the reinforcement of the two sides, with significant savings on the DBD-side. Pre-test calculations show no major difference in the seismic performance of the two sides of the test structure. Copyright © 2001 John Wiley & Sons, Ltd. [source] Vertical stress distributions around batter piles driven in cross-anisotropic mediaINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2009Cheng-Der Wang Abstract This work presents analytical solutions to compute the vertical stresses for a cross-anisotropic half-space due to various loading types by batter piles. The loading types are an embedded point load for an end-bearing pile, uniform skin friction, and linear variation of skin friction for a friction pile. The cross-anisotropic planes are parallel to the horizontal ground surface. The proposed solutions can be obtained by utilizing Wang and Liao's solutions for a horizontal and vertical point load acting in the interior of a cross-anisotropic medium. The derived cross-anisotropic solutions using a limiting approach are in perfect agreement with the isotropic solutions of Ramiah and Chickanagappa with the consideration of pile inclination. Additionally, the present solutions are identical to the cross-anisotropic solutions by Wang for the batter angle equals to 0. The influential factors in yielded solutions include the type and degree of geomaterial anisotropy, pile inclination, and distinct loading types. An example is illustrated to clarify the effect of aforementioned factors on the vertical stresses. The parametric results reveal that the stresses considering the geomaterial anisotropy and pile batter differ from those of previous isotropic and cross-anisotropic solutions. Hence, it is imperative to take the pile inclination into account when piles are required to transmit both the axial and lateral loads in the cross-anisotropic media. Copyright © 2008 John Wiley & Sons, Ltd. [source] Lateral load distributions on grouped piles from dynamic pile-to-pile interaction factorsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2009Der-Wen Chang Abstract The load distributions of the grouped piles under lateral loads acting from one side of the pile cap could be approximately modeled using the elasticity equations with the assumptions that the underground structure is rigid enough to sustain the loads, and only small deformations of the soils are yielded. Variations of the soil,pile interactions along the depths are therefore negligible for simplicity. This paper presents the analytical modeling using the dynamic pile-to-pile interaction factors for 2,×,2 and 2,×,3 grouped piles. The results were found comparative with the experimental and numerical results of other studies. Similar to others' findings, it was shown that the leading pile could carry more static loads than the trailing pile does. For the piles in the perpendicular direction with the static load, the loads would distribute symmetrically with the centerline whereas the middle pile always sustains the smallest load. For steady-state loads with operating frequencies up to 30 Hz, the pile load distributions would vary significantly with the frequencies. It is interesting to know that designing the pile foundation needs to be cautioned for steady-state vibrations as they are a problem of machine foundation. However, for transient loads or any harmonic loads acting upon relatively higher frequencies, the pile loads could be regarded as uniformly distributed. It is hoped that the numerical results of this paper will be helpful in the design practice of pile foundation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Numerical analysis of pile behaviour under lateral loads in layered elastic,plastic soilsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2002Zhaohui Yang This paper presents results from a finite element study on the behaviour of a single pile in elastic,plastic soils. Pile behaviour in uniform sand and clay soils as well as cases with sand layer in clay deposit and clay layer in sand deposit were analysed and cross compared to investigate layering effects. Finite element results were used to generate p,y curves and then compared with those obtained from methods commonly used in practice. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||