Book•
Foundation analysis and design
01 Jan 1968-
TL;DR: In this paper, Fondation de soutenagement et al. presented a reference record for Dimensionnement Reference Record created on 2004-09-07, modified on 2016-08-08.
Abstract: Keywords: Fondation ; Mur de soutenement ; Pieux ; Capacite portante ; Ancrage ; Dimensionnement Reference Record created on 2004-09-07, modified on 2016-08-08
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Dissertation•
01 Jan 1998
TL;DR: In this paper, the bearing capacity of ring footings on a dense sand under vertical loads was investigated by means of centrifuge modelling, the method of characteristics and the finite element technique. But the results of the analysis were limited to a small area of 15 cmµ and with ring radii ratios from 0 to 0.9.
Abstract: Ring foundations are often adopted for large and tall structures to resist lateral loads and to increase the stability against overturning. They have been used worldwide under various structures, including telecommunication towers, liquid storage tanks, bridges and offshore structures. However, the behaviour of these foundations has not been well understood. An accepted method for estimating the bearing capacity is not available. In the design of ring foundations, very crude simplifications have to be made. Therefore, developing a rational and practical procedure for estimating the bearing capacity of ring foundations is of great importance. -- This thesis presents research on the bearing capacity of ring footings on a dense sand under vertical loads. The effects of footing size, ring radii ratio and load eccentricity have been investigated by means of centrifuge modelling, the method of characteristics and the finite element technique. To support the research, triaxial and oedometer compression tests have been conducted to determine the soil friction angles, in situ stress ratios, and plastic and elastic behaviour of the sand. The peak and critical state friction angles of the sand from triaxial tests are reduced by 4° to 5° with a log-cycle increase of confining pressure. -- Over 40 centrifuge tests of ring footings have been conducted at acceleration levels from 10 to 160 gravities. High quality sand test samples with density index of 90% were prepared using a developed raining technique. The aluminum model footings with a constant area of 15 cm² and with ring radii ratios from 0 to 0.9 were tested under load eccentricity ratios from 0 to 0.375. Test results indicate that the bearing capacity is significantly affected by footing size, ring radii ratio and load eccentricity. It is found that The bearing capacity of circular footings increases linearly with footing diameter in a double-log scale diagram. The bearing capacity of a vertically loaded ring footing can be expressed in terms of a bearing capacity ratio (Br), a reduction factor (Re) and the bearing capacity of an axially loaded circular footing with the same area. Test results show that the value of Br is related only to the ring radii ratio (n)T independent of footing size; when n is from 0 to 0.35, Br increases slightly with n. Further increase of n beyond 0.35 results in significant decrease of Sr. The value of Re decreases with load eccentricity and is independent of ring radii ratio. The procedure presented for evaluating the bearing capacity of ring foundations is very practical. -- Circular footings under axisymmetric conditions have been analyzed by the method of characteristics to further study the effect of footing size on bearing capacity. In the analysis, the soil friction angle can be variable or assumed to be constant. The bearing capacities calculated also increase linearly with footing diameter in a double-log scale diagram and are close to the centrifuge test results. The compatibility of bearing capacities obtained from both variable and constant friction angle analysis provides a basis for the FE analysis using an equivalent constant friction angle for each footing. -- The FE technique has been applied to circular and ring footings on the dense sand under axial vertical loads. In the analysis, a footing is represented by a rigid body consisting of rigid surface elements. Interface elements are used to model the interaction between the footing and soil. The elasto-plastic behaviour of soil is simulated by the Drucker-Prager/Cap constitutive model. Compared with centrifuge test data, the analytical results regarding the effect of footing size and ring radii ratio on bearing capacity are satisfactory. When calibrated with experimental data, the FE technique is very useful for analysis of very large foundations or for cases when experimental data are not available or difficult to obtain.
18 citations
01 Apr 2017
TL;DR: In this paper, the authors used the plane-strain bulge test to study the mechanical and thermal behavior of the micro circular diaphragm (MCD) in both the elastic and plastic regimes.
Abstract: The Micro circular diaphragm (MCD) is the mechanical actuator part used in the micro electro-mechanical sensors (MEMS) that combine electrical and mechanical components. These actuators are working under harsh mechanical and thermal conditions, so it is very important to study the mechanical and thermal behaviors of these actuators, in order to do with its function successfully. The objective of this paper is to determine the thermo-mechanical behavior of MCD by developing the traditional bulge test technique to achieve the aims of this work. The specimen is first pre-stressed to ensure that is no initial deflection before applied the loads on diaphragm and then clamped between two plates, a differential pressure (P) and temperature (Tb) is leading to a deformation of the MCD. Analytical formulation of developed bulge test technique for MCD thermo-mechanical characterization was established with taking in-to account effect of the residual strength from pre-stressed loading. These makes the plane-strain bulge test ideal for studying the mechanical and thermal behavior of diaphragm in both the elastic and plastic regimes. The differential specimen thickness due to bulge effect to describe the mechanical behavior, and the temperature effect on the MCD material properties to study the thermal behavior under deformation were discussed. A finite element model (FEM) can be extended to apply for investigating the reliability of the proposed bulge test of MCD and compare between the FEM results and another one from analytical calculus. The results show that, the good convergence between the finite element model and analytical model.
18 citations
TL;DR: In this article, the effect of the soil subgrade modulus on bridge pile bent buckling and pushover capacity was investigated and it was shown that the buckling capacity and stability of these bents vary inversely with the square of the bent height.
Abstract: A common design/construction procedure for highway bridges that are over marshes, small creeks, and shallow bodies of water is to have the bridge superstructure supported on pile bents During major flood events, the volume and velocity of flood waters can cause considerable scouring to occur at the bents As the elastic buckling capacity and stability of these bents vary inversely with the square of the bent height, a scour of 46 m (15 ft) at a bent that was originally 46 m (15 ft) in height will reduce its elastic buckling capacity by a factor of 4 Also the correct buckling load of such bents is somewhat questionable because of the unknown degree of fixity afforded by the soil at the pile ground line This paper summarizes an investigation of the effect of the soil subgrade modulus on bridge pile bent buckling and pushover capacity Analysis results indicate that bent pile buckling and pushover loads are not very sensitive to the soil subgrade modulus, k0 , unless the value of k0 is very small, ie,
18 citations
TL;DR: In this article, four different wind turbine (WT) foundations were designed and optimised in Ireland, which include the small-scale onshore, large-scale offshore monopile and offshore gravity-based foundation.
18 citations
TL;DR: In this paper, various methods for determining depths to fixity as required in an equivalent cantilever pile model, including the current practical method (LRFD method) and the proposed method with a comprehensive numerical procedure, are described and discussed.
18 citations