The problem of structural isolation from ground transmitted vibrations by open or infilled trenches under conditions of plane strain is numerically studied. The soil medium is assumed to be linear elastic or viscoelastic, homogeneous and isotropic. Horizontally propagating Rayleigh waves or waves generated by the motion of a rigid foundation or by surface blasting are considered in this work. The formulation and solution of the problem is accomplished by the boundary element method in the frequency domain for harmonic disturbances or in conjunction with Laplace transform for transient disturbances. The proposed method, which requires a discretisation of only the trench perimeter, the soil-foundation interface and some portion of the free soil surface on either side of the trench appears to be better than either finite element or finite difference techniques. Some parametric studies are also conducted to assess the importance of the various geometrical, material and dynamic input parameters and provide useful guidelines to the design engineer.

Vibration isolation using open or filled trenches

Rectangular open or in‐filled trenches (wave barriers) are often used in engineering practice to reduce the ground vibrations caused by propagating surface (Rayleigh) waves of relatively small wavelengths. This paper presents simple design expressions for estimating the vibration screening effectiveness of rectangular wave barriers in homogeneous soil deposits. The design formulas are developed by conducting an extensive numerical investigation on the influence of various geometrical and material parameters on the vibration screening effectiveness of the barriers. An advanced direct Boundary Element Method (BEM) incorporating higher‐order isoparametric elements and a sophisticated self‐adaptive numerical integration scheme is used for this study. Dimensionless parameters that govern a barrier's performance are then identified, and models are developed taking these parameters into account in a simplified way. Through some comparisons with results from the rigorous BEM code and available experimental data, ...

Simplified design for vibration screening by open and in-filled trenches

Full scale experimental study on vibration scattering using open and in-filled (GeoFoam) wave barriers

Vibration isolation by a row of piles using a 3‐D frequency domain BEM

Reduction of train-induced building vibrations by using open and filled trenches

The isolation of structures from ground transmitted waves by open and infilled trenches in a three-dimensional context is numerically studied. The soil medium is assumed to be elastic or viscoelastic, homogeneous and isotropic. Waves generated by the harmonic motion of a surface rigid machine foundation are considered in this work. The formulation and solution of the problem is accomplished by the boundary element method in the frequency domain. The infinite space fundamental solution is used requiring discretization of the trench surface, the soil-foundation interface and some portion of the free soil surface. The proposed methodology is first tested for accuracy by solving three characteristic wave propagation problems with known solutions and then applied to several vibration isolation problems involving open and concrete infilled trenches. Three-dimensional graphic displays of the surface displacement pattern around the trenches are also presented.

Vibration isolation using open or filled trenches Part 2: 3-D homogeneous soil

Computation of vibration levels in underground space

The commercial nuclear power plant industry initiated the licensing modernization project (LMP) to enhance the risk-informed and performance-based (RIPB) regulatory basis for advanced nuclear power reactors. The LMP framework relies heavily on RIPB concepts and approaches that together integrate the defense-in-depth philosophy. One example approach for seismic design is to align the LMP concepts with the performance targets described in the American Society of Civil Engineers (ASCE) standard, ASCE 43-19. The underlying strategy of this approach is to consider the performance of individual structures, systems, and components (SSCs) in seismic design, as well as the role they play in an accident event sequence. This approach contrasts with current regulations, in which every individual safety-related SSC is designed to the same seismic criteria irrespective of the role the SSC plays in the overall system performance. This new philosophy envisions more flexible seismic design options for each SSC, such that the overall seismic design can meet system-level acceptability criteria as well as plant-level acceptability criteria. The objective of this paper is to illustrate the flexibility and benefits of this proposed approach to the seismic design of SSCs in terms of reduced SSC demands (by reducing the design ground motions for SSCs) and improved SSC capacities (by allowing for alternative damage state limits). A simple shear wall was designed using ASCE 43-19 for a hard rock site in the Central Eastern United States considering alternate seismic design category and limit state combinations to examine the physical designs and functional fragilities of these combinations and their impact on seismic performance. The flexibility of this proposed approach is illustrated by an example that shows reduced SSC demands, while the SSC capacities and margins remain consistent with the required safety performance without any loss in overall plant safety. 

B. Dasgupta

Papers

Vibration isolation using open or filled trenches

Vibration isolation using open or filled trenches Part 2: 3-D homogeneous soil

Computation of vibration levels in underground space

Proposed Enhancements to the Risk-Informed and Performance-Based Regulatory Framework for Seismic Hazard Design at NRC-Regulated Nuclear Power Plants