Dynamics of structures


 The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

Statistics: Methods and Applications.

http://ssu.ac.ir/cms/fileadmin/user_upload/Moavenatha/Mposhtibani/Mdaftar_fani/KhadamatKarkonan/Articles/EN/Tust_Vol_16_4_247-293.pdf

Seismic design and analysis of underground structures

http://www.jlakes.org/config/hpkx/news_category/2015-05-10/1-s2.0-S0883292714002212.pdf

Mine tailings dams: Characteristics, failure, environmental impacts, and remediation

Non-linear one-dimensional seismic ground motion propagation in the Mississippi embayment

Damping formulation for nonlinear 1D site response analyses

Accurate prediction of ground-surface settlement adjacent to an excavation is often difficult to achieve without using accurate representation of small-strain nonlinearity in a soil model within finite-element analyses. In this paper a simplified semiempirical model is proposed for predicting maximum wall deflection, maximum surface settlement, and surface-settlement profile due to excavations in soft to medium clays. A large number of artificial data are generated through finite-element analyses using a well-calibrated, small-strain soil model. These data, consisting of wall displacements and ground-surface settlements in simulated excavations in soft to medium clays, provide the basis for developing the proposed semiempirical model. The proposed model is verified using case histories not used in the development of the model. The study shows that the developed model can accurately predict maximum wall deflection and ground-surface settlement caused by braced excavations in soft to medium clays.

Simplified Model for Wall Deflection and Ground-Surface Settlement Caused by Braced Excavation in Clays

Neural network (NN) based constitutive models can capture non-linear material behaviour. These models are versatile and have the capacity to continuously learn as additional material response data becomes available. NN constitutive models are increasingly used within the finite element (FE) method for the solution of boundary value problems. NN constitutive models, unlike commonly used plasticity models, do not require special integration procedures for implementation in FE analysis. NN constitutive model formulation does not use a material stiffness matrix concept in contrast to the elasto-plastic matrix central to conventional plasticity based models. This paper addresses numerical implementation issues related to the use of NN constitutive models in FE analysis. A consistent material stiffness matrix is derived for the NN constitutive model that leads to efficient convergence of the FE Newton iterations. The proposed stiffness matrix is general and valid regardless of the material behaviour represented by the NN constitutive model. Two examples demonstrate the performance of the proposed NN constitutive model implementation.

Youssef M. A. Hashash

Papers

Seismic design and analysis of underground structures

Non-linear one-dimensional seismic ground motion propagation in the Mississippi embayment

Damping formulation for nonlinear 1D site response analyses

Simplified Model for Wall Deflection and Ground-Surface Settlement Caused by Braced Excavation in Clays

Numerical implementation of a neural network based material model in finite element analysis