Stability of a Mast Foundation: A Case Study

2019

The Argentinian National Commission of Atomic Energy (CNEA) developed the RA-10 project, an experimental multipurpose nuclear reactor with a power of 30 MW, located in the Ezeiza Atomic Center, in Buenos Aires, Argentina. The foundation of the reactor is a reinforced concrete mat placed on a sedimentary pile including Pleistocene indurated fine soils and deep Miocene clays. The paper presents various aspects of the design of this foundation, including the calibration of numerical models for the 3D ground-structure interaction analysis and the structural optimization of the mat in terms of stresses, deformations and interaction among adjacent buildings.

2004

The design and installation of safe and economic foundation solutions for large projects is of great importance in contributing to commercial success. On four recent power projects in the U.K., a variety of foundation solutions have been adopted, driven largely by the particular ground conditions encountered at each location. All four projects were gas fired combined cycle power station facilities and each location provided unique challenges in both the design and installation of the foundations. The variety of foundation soils encountered was diverse; soft alluvial peat and clay, loose to medium dense silty sands and moderately weak to moderately strong Triassic rock. Foundation solutions included shallow spread options, reinforced earth/rock fill, ground improvement and bearing piles. Various technical difficulties were overcome at each of the sites and important lessons have been learnt from these. All four power stations are similar in their design and bearing pressure requirements. The foundation solutions are all different and were selected to suit local ground conditions.

Design for a large refinery expansion was undertaken at a site reclaimed from a lake about 40 years ago. The natural soils consist of sand deposited on normally consolidated, compressible post glacial lacustrine clay followed by silty clay till on limestone bedrock found at about 25 m to 30 m depth below existing grade. The site will be raised an additional 1.5 m, which will cause long-term settlement. Some of the new units are 30 m to 70 m in height and will be supported on piles—several thousand in all. In anticipating negative skin friction to develop, the initial design called for subtracting the drag load from the allowable load determined from the pile capacity. Initial design also expected the piles to be constructed to bedrock. However, a review of the design made clear that a drag load is a problem for the axial structural strength of a pile and should not be subtracted from an allowable load based on bearing capacity. Moreover, analysis of the results of full-scale static ...

Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2017

Offshore wind energy towers are dynamically loaded by waves and wind. Pile foundations provide stiffness and damping and should be properly calculated. A combined finite-element boundary-element method for the dynamic interaction of flexible structures and the soil has been developed. The flexible structures such as single piles or complete wind energy towers are modeled by the finite element method whereas the homogeneous or layered soil is modeled by the boundary element method which uses the Green's functions for interior loads in the layered half-space to establish the dynamic stiffness matrix of the soil. Soils with a stiffness that is continuously increasing with depth can be modeled as multi-layer soils with step-wise increasing stiffness. The effects of different parameters such as the stiffness of the soil, the axial and bending stiffness of the pile, and the radius of the cylindrical contact area will be analysed for the different components of excitation (vertical, horizontal, rotation and coupling). The results can be determined as specific power laws which are different for the different load cases and for the different soil models (Winkler support, homogeneous continuum, continuum with increasing stiffness). The dynamic effect of radiation damping will be analysed by the frequency-dependent compliance functions. A clear layering of the soil can cause noticeable changes in the dynamic compliances as reductions of the stiffness and the damping in certain frequency ranges (below and around layer resonance frequencies). The distribution of the displacements along the pile help to explain the observed laws. An example of an offshore wind energy tower has been modeled and calculated for wind, wave and weight loads. The resonances of the tower are usually limited by the radiation damping which is strongest for a soft soil.

IRJET, 2023

Before the actual construction process starts, it is important to conduct a site investigation and soil exploration to acquire vital information about the soil and site conditions. In a construction site investigation is the first and crucial step. These are outlined in the project to ensure that the site is appropriate for the proposed construction and to offer recommendations on the design and construction processes. Following soil investigation based on the soil report, further geotechnical design of a shallow foundation was performed; however, the results indicated that the load coming from the structure was less than the results of the shallow foundation, so we opted for the geotechnical design of a pile foundation, which resulted at an end bearing capacity greater than the load coming from the structure. The geotechnical design of the pile consists of recommending the size of the pile and calculating the safe working load of each pile.

Optimization of Design for Better Structural Capacity

The design of foundations constitutes a major step for each civil engineering structure. Indeed, the stability of those structures relies on cost-effective and adequately designed foundation solutions. To come up with an optimized design of a foundation, the geotechnical study passes several steps: the geotechnical survey including in situ and laboratory tests, the synthesis of geotechnical parameters to be considered for the design, and the suggestion of foundation solution avoiding over estimated cost and ensuring suitable method of execution. In this chapter, the three currently practiced categories of foundation are briefly introduced. Then, two illustrative Tunisian case histories are analyzed to explain, first, when the practiced foundation solution was inadequately chosen how a non-cost-effective solution can be avoided, and second, why an unsuitable foundation solution can lead to the stopping of the structure functioning and then how to proceed for the design of retrofit so...

1994

1970

The evaluation of the response of reinforced concrete buildings subjected to seismic attacks, wind excitation or other dynamic loading types is essentially affected by the behaviour of the soil surrounding the foundation of the building. Many researchers have been studying the effect of soil structure interaction (SSI) over the last century, but there is still a controversy about the role of soil structure interaction (SSI) and its effect on changing the behaviour of structures. Commonly, designers assume that the base of the structure is fixed, but this approach is certainly not appropriate, for the reason that the stiffness and the damping of the soil are essential for a better designing of a structure. In this paper, the authors will discuss some proposed methods on taking account of soil-structure interaction that must be considered from the very beginning of the design process. In addition, an investigation about the dynamic response of a reinforced concrete structure subjected to seismic loads and designed by assuming the base coupled with discrete spring and dashpot elements, will be carried out.