Rigidity Of Foundation Research Articles

Evaluation bearing capacity of ring footings on reinforced loose sand

Ring footing represents a significant structural member in different applications such as fuel or water storage tanks in addition to other structures. The advantage of this type of footing is related to the ability to reduce the weakness of some soils that may affect the safety of structures. An experimental testing program was conducted by using a small-scale model in the laboratory of the college of engineering at the university of Al-Mustansiriyah which consists of twelve ring footing models resting on loose sand reinforced by geogrid layers. The parameters that studied in this research are the diameter of ring footing, thickness of ring, the position placed of one reinforced layer and vertical spacing between two reinforced layers. The findings of this research shown that the optimum percentage of diameter ratio of ring footing is (0.25) and when the depth-ratio increases, the bearing-capacity of ring footing begin decreases. In general, the increase in ring thickness causes the bearing-capacity and the rigidity of ring foundation to increase. The optimum of the depth-ratio of the first reinforced layer is (0.25) and the optimum value of vertical-spacing bounded by layers is around (0.25) which produces a maximum value of the bearing-capacity. Its noticed that when these percentages exceeded value 0.25, the bearing-capacity of the ring foundation drops eventually.

Investigation on the dynamic response of porous FGM beams resting on variable foundation using a new higher order shear deformation theory

In this work, the dynamic response of functionally graded beams on variable elastic foundations is studied using a novel higher-order shear deformation theory (HSDT). Unlike the conventional HSDT, the present one has a new displacement field which introduces undetermined integral variables. The FG beams were assumed to be supported on Winkler-Pasternak type foundations in which the Winkler modulus is supposed to be variable in the length of the beam. The variable rigidity of the elastic foundation is assumed to be linear, parabolic and sinusoidal along the length of the beam. The material properties of the FG porous beam vary according to a power law distribution in terms of the volume fraction of the constituents. The equations of motion are determined using the virtual working principle. For the analytical solution, Navier method is used to solve the governing equations for simply supported porous FG beams. Numerical results of the present theory for the free vibration of FG beams resting on elastic foundations are presented and compared to existing solutions in the literature. A parametric study will be detailed to investigate the effects of several parameters such as gradient index, thickness ratio, porosity factor and foundation parameters on the frequency response of porous FG beams.

Steel Sheet Piles – Applications and Elementary Design Issues

High-intensity housing having been carried out in town’s centres causes that many complex issues related to earthworks and foundations must be resolved. Project owners are required to ensure respective number of parking bays, which in turn demands 2-3 storeys of underground car parks. It is especially difficult to fulfil in dense buildings of old town areas where apart from engineering problems, very stringent requirements of heritage conservator supervision are also raised. The problems with ensuring stability of excavation sidewalls need to be, at the same time, dealt with analysis of foundations of neighbouring structures, and possible strengthening them at the stages of installing the excavation protection walls, progressing the excavations and constructing basement storeys. A separate problem refers to necessity of constructing underground storeys below the level of local groundwater. This requires long-term lowering of water table inside excavation while at possibly limited intervention in hydrological regime beyond the project in progress. In river valleys such “hoarding off” the excavation and cutting off groundwater leads to temporary or permanent disturbances of groundwater run-off and local swellings. Traditional way to protect vertical fault and simultaneously to cut-off groundwater inflow consists in application of steel sheet pilings. They enable to construct monolithic reinforced concrete structures of underground storeys thus ensuring both their tightness and high rigidity of foundation. Depending on situation, steel sheet pilings can be in retrieving or staying-in-place versions. This study deals with some selected aspects of engineering design and fabrication of sheet piling for deep excavations and underground parts of buildings.

Dynamic Characteristics of Saturated Silty Soil Ground Treated by Stone Column Composite Foundation

A shaking table model test was carried out to develop an understanding of the performance improvement of saturated silty soil ground using stone column composite foundation as reinforcement. It is found that at less than 0.161 g loading acceleration, soil between piles has not yet been liquefied, the response acceleration scarcely enlarges, and the shear displacement almost does not appear in silty soil. At 0.252 g loading acceleration, as a result of liquefaction of soil between piles, the response acceleration increases rapidly and reaches its peak, and the shear displacement of silty soil increases significantly. At 0.325 g loading acceleration, the integral rigidity of foundation decreases greatly, which reduces its capability of vibration transmission and result in the response acceleration amplification coefficient is less than that at the former loading acceleration, but the shear displacement of silty soil further increases. The stone column composite foundation can greatly reduce both the shear displacement and the settlement of ground compared with untreated foundation. Under the condition of 7-degree seismic fortification, the design meets seismic resistance requirements.

The Influence on Bundled Tube Structure of Super-High Building Caused by Changing-Rigidity of the Ground or the Foundation

With the rapid development of the subgrade or the foundation over recent years in China, there is a growing tendency for tall building to orient its directions to the more numbers of plies, much higher and more complex in plane layout. Moreover, some buildings adopt tube structure or bundled tube structure and so on to diversified development. The changing-rigidity of ground or foundation has obvious effects on superstructure when the buildings act on much higher and huge type. Therefore, in view of this, taking the bundled-tube structure of super high building for example in the paper, the method, equal the bundled tube structure of super high building and its foundation to stiffening-thin wall-combination, is adopted, then based on the three-dimensional model, the rigidity of subgrade and foundation’s effect on superstructure are given by calculation with semi-analysis. The calculated result indicated that there exist remarkable influence on sideway of the top end, the sideway between layers, the warp of the tube and the stresses between the subgrade and the bottom of the foundation.

Experimental study on settlement of model piles in frozen soil under dynamic loading

Test results show that the settlement process of model piles is mainly the rheological process of fmzen soil under shear loading. The settlement rate of model piles increases with increasing temperature of frozen soil, decreasing royghness of pile surface and increasing rigidity of pile foundation. As the water content of frozen soil reaches its saturation value, the settlemerrt rate is the least. When the level of loading is higher, the settlement rate under dynamic loading is less than that under static loading. With the level of loading lowering, the effect between dynamic and static loading on the settlement rate becomes close gradually. Under the present test conditions, the settlement rate of model piles is independent of the frequency of dynamic loads.

Determination of the parameters of a model of a base from engineering-geologic survey data

The authors present a mathematical model that aids in the design of foundations of hydroelectric power plants. The semi-infinite linearly deformable elastic solid model, SIE model, allows calculation of the effect of the shape in plan and rigidity of foundation, the mutual effect of foundations, etc. Engineering-geologic surveys are used to establish analogues for the SIE model.

Effects of foundation size on Fourier spectrum amplitudes of earthquake accelerations recorded in buildings

Hypotheses that typical building foundations attenuate amplitudes of incident earthquake motions by scattering mechanism has been investigated. By analysis of normalized spectra of motions recorded inside building foundations it is found that the effect of size of building foundation if present is much smaller than the inherent variance of the data so far recorded in 57 building. Through comparison with theoretical results for vibration of rigid hemispherical and the disk foundation it is concluded that the relative rigidity of foundation may play a major role in influencing the degree to which foundation size influences strong motion recorded in building basements.

ディーゼル機関用歯車, 弾性継手およびクラッチについて

In marine application the medium speed diesel engine requires gears to adapt its operational speed to the speed with which the propeller performs highest efficiency. There are many configurations of marine gears. They depend on kind and number of engines as well as on the engine room installation. Reverse reduction gears of very different design, single input reduction gears, vertical or horizontal offset or coaxial, twin or multiple input form the main groups of this section of gear designing. The single stage gear unit of today shows very compact design and a high load carrying capacity. This is due to the surface treatment of the tooth flanks by hardening processes. Outstanding experience has been collected with carburised teeth, which have been ground for accuracy achievement. Effective profile modification for the purpose of high bending resistance, protuberance milling to keep the roots of the teeth untouched by the grinding wheel result in utmost resistance against wear and rupture. So the specific loading agreed to by the classification societies are fully justified.The required accuracy of those gears even at their low circumferential velocity is to compare with the precision of turbine gears manufactured according to BSS 1807. Important are full contact areas between the teeth, this requires careful observation of shaft deflection, bearing clearance, thermal distortions and rigidity of housing, thrust block and foundation in the hull. Another important condition to be observed satisfactory performance of marine gears is the absence of major torsional vibrations producing overload torque or even torque reversal. With diesel engines as power sources excitations of torsional vibrations are very likely to interfere with one or another of the natural ferquencies of the propulsion system. The fundamental connections required to calculate torsional vibration and the rise of torques caused by them are well known. With increasing familiarization of computer technique the calculation procedure has been refined to handle even manifold systems easily and practically reliable.The necessary over-all-elasticity of the torsional vibrating system thus can be calculated and realised. More and more there are used torsionally elastic couplings to dislocate the natural frequencies to the region of low speed. Good performance showed rubber couplings with metal bonded contact surfaces of special design, which allows a prestressing of the bonded surfaces. Their high torsional elasticity and damping property assures an overcritical operation. At the same time they allow for misalignment without any maintenance trouble. In some cases where it is advisable to avoid the turbulence zone at low speed at all, there are torsional elastic clutches available. They consist of the same elastic rubber elements combined with a clutching device with friction cones and pneumatically operated ring cylinder. Thus, it is possible to engage the whole propulsion system only after having reached the engine service speed. With disengaging and re-engaging the clutch great advantage is obtained during “crashstop”-manouvre, because the time for propeller reversal is much reduced. In any case torsionally elastic clutches are required for twin or multiple engine installations, where they have been applied originally and have proven an ample reputation of reliability. Nowadays, the tedency to install unmanned engine rooms leads to immediate measuring of engine torque : this is relatively easy with highly elastic couplings of linear characteristic, the torsional angles of which are large enough to furnish significant values for the purpose of measurement.The lecture points out the recent development which has been achieved on the side of Gearing and Couplings adequate to the development of the medium speed diesel engines.