Introduction The current state of practice adopts Rankine/Coulomb theory to estimate static passive pressure and Mononobe-Okabe (M-O) method to determine seismic passive pressure. As you know, each of these approaches were formulated based on some assumptions that may not apply to all of our daily engineering problems. For instance, the M-O method was originally developed… Read More
Verification and validation are the essential procedures required to assess accuracy and credibility of numerical analyses. The terms “verification” and “validation” are often used interchangeably in the current engineering practice. However, the two procedures have entirely different meanings and applications. The differences are outlined below: Verification is meant to identify and remove programming errors in a… Read More
Per the current state of practice, a pile design is typically completed by checking the following design items: Static settlement which includes elastic compression of pile, immediate and consolidation settlements of soil; Structural and geotechnical bearing capacity of pile in static and seismic conditions; Seismic settlement under downdrag forces induced by the surrounding soil during… Read More
Due to the complexity of finite element programs, performing a finite element analysis may seem unattractive for some geotechnical engineers. Interestingly, they may prefer to alternatively use simple traditional semi-empirical methods which are generally formulated based on some assumptions that may not be even applicable for the problem in hand. Nonetheless, the engineers rather use… Read More
This article intends to shed light on application of Rayleigh and numerical damping in finite element and finite difference analyses. As you all know, there are two types of damping in a system subjected to dynamic loads; (1) material damping, and (2) radiation damping. Material damping is the dissipated energy due to the yielding of… Read More
This article outlines the common design procedures used to evaluate the performance of geotechnical systems that are proposed for mitigation of lateral spreading. The design of any type of retaining structure generally includes; (i) global stability analysis, and (ii) internal stability analysis. In the former, general mass movement of a retaining structure as well the… Read More
Current state of practice in North America to evaluate the performance of slopes during earthquake loading is to use one of the following approaches: 1. Limit Equilibrium Approach This approach uses horizontal and vertical seismic coefficients ( and ) to estimate seismic loads and performs a traditional limit equilibrium analysis to evaluate factor of safety… Read More
Boundary condition at base of a finite element/difference model can significantly affect outputs of a seismic analysis. The key to find out what base boundary condition suits our numerical model is to find out whether the earthquake motion to be applied at the base of our model is “outcrop motion” or “within motion”. Outcrop motions… Read More
The worldwide state of practice for simulating static and seismic soil-pile interaction is to use a set of one-dimensional springs along pile shafts. This approach is also referred to as Beam on Nonlinear Winkler Foundation (BNWF). Due to its simplicity, the method is widely used in almost all engineering firms around the world for the… Read More
A few months ago, I was involved in a very interesting and challenging project in Bay Area, California. A portion of this project was to evaluate seismic performance of an existing wharf structure located at the project site. The subsurface soil consisted of loose silty sand fill underlain by up to 25ft deep soft young bay… Read More