Design Of Foundations For Structures Research Articles

지반-구조물 상호작용을 고려한 기초모델링

지반-구조물의 상호작용은 구조물의 동적 해석 및 기초 설계에 있어 지대한 영향을 미침에도 불구하고 그 중요성이 간과되어 왔다. 이는 모델링 과정의 복잡성으로 인해 실무자를 위한 적절한 절차가 미비 하다는 점에서 상당부분 그 이유를 찾을 수 있을 것이다. 본 연구에서는 먼저 구조물의 동적 해석이 필수적으로 요구되는 강진지역인 미국 캘리포니아에 위치한 Cal(IT)2 건물을 대상으로 지반 경계조건을 달리했을 시 해석상의 차이가 어느 정도 나는지를 검토해 보았다. 기초 모델링 기법의 하나인 Beam on Nonlinear Winkler Foundation Model을 Linear Matrix Inequalities Model Reduction 기법을 활용하여 보다 간략하게 사용할 수 있도록 하였다. 이렇게 하여 만들어진 대상 건물의 유한요소 모델과 실재 얻어진 가속도 데이터를 비교하여 제시된 방식을 통해 매우 우수한 해석 결과를 얻을 수 있음을 보였다. Even with its significant influence on the dynamic analysis and foundation design of structures, sometimes the soil-structure interaction has been ignored during the design process. One of the reasons is due to the fact that the modeling procedures are too complicated to meet the requirements in practice. In this study, using the Cali(IT)2 building in California with high and frequent seismic activities, the analysis differences for different boundary conditions are reviewed. The Beam on Nonlinear Winkler Foundation Model, one of the foundation modeling methods, is modified for easy use by the Linear Matrix Inequalities Model Reduction Technique. The product of the proposed process is applied to create the Finite Element Model. The results show fairly good agreement with the real data acquired from the Cal(IT)2 building.

Imaging Systems and Algorithms for the Numerical Characterization of Three-Dimensional Shapes of Granular Particles

The shear properties of natural granular particles such as sand are significantly dependent on the shapes of the particles in the mixture. This is important from a practical viewpoint, because a measurement and characterization technique for the 3-D shapes of such particles can lead to an improved understanding of soil stability and influence the design of structural foundations. Previous techniques that have been developed for this purpose have proven to be complex, and the associated instrumentation has proven to be expensive. Furthermore, conventional 2-D shape measurement and description methods do not readily lend themselves to parsimonious 3-D representations. The situation is further complicated by the fact that, to parameterize the relationship between shape and shear characteristics, a single numerical descriptor is required to model the 3-D shapes of multiple particles in a natural sand particle mixture. This paper describes an optical tomography technique for the measurement of particle data that is then characterized using statistical 3-D shape descriptors. The algebraic reconstruction technique (ART) is used to synthesize 3-D particle shapes from 2-D tomography projections. It is shown that the measurement and characterization techniques used can provide distinct features for differently shaped particle mixtures and can be used to synthesize 3-D composite particles representative of the entire mix. The novelty of the technique described in this paper is that numerical shape descriptors can be obtained for not only a single 3-D object but also an entire collection of 3-D objects. Furthermore, the statistical nature of the 3-D shape descriptor of a particle mixture can be used to synthesize a mixture containing an arbitrary number of particles that have similar but not identical shapes. Results demonstrating the efficacy of the method on a set of natural sand particle mixtures are presented.

Resolving Overburden Characteristics Via Shear Wave Propagation

In shallow site investigations information is often required on both the thickness of overburden material and its physical properties prior to drilling the site. While conventional compressional wave methods may resolve the former, shear wave refraction shooting can also provide information on the sediment's shear deformation characteristics. Furthermore, in some instances the shear wave is more suited to resolving depth to bedrock due to its characteristically large velocity contrast at a sediment/rock interface and thus shear wave methods should be given due consideration when planning any geophysical site survey. Data from a research exercise on a potential opencast coal site clearly illustrate the case for shear wave refraction shooting. However, the accuracy of bedrock depth determination is shown to be dependent on interpretation procedures, the input of a shear wave velocity gradient function for the overburden being essential to the interpretation. Given the availability of shear wave velocity data other engineering applications become apparent. In reconnaissance surveys such as the above they may be used in assessing the rippability of the overburden, while in more comprehensive site investigations, the geophysically-derived parameters from crosshole shooting may be used in the design of structural foundations.