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
Subgrade reaction modulus is the ratio of soil pressure to deflection. This modulus is widely used in structural design of mats and slabs. The structural design is completed by structural engineer of record (SEOR) where he/she utilizes the concept of Beam on Nonlinear Winkler Foundation in order to estimate the pressure of soil as well… Read More
ASCE 7-10 – Section 20.3.1 requires performing site response analysis when site class is F and fundamental vibration period of structure is greater than 0.5 seconds. In this article we want to achieve a clear understanding of this important requirement of the Code. Building Codes of almost all countries, including ASCE 7-10, provide site amplification… Read More
Structural engineers often ask geotechnical engineers if the insitu liquefiable soil (site class F) in a project site can be improved so that the foundation soil is classified as E or D. In order to answer this question, the geotechnical engineer should evaluate the soil condition and find a method to mitigate liquefaction. There are… Read More
In the current state of practice, any soil settlement other than consolidation settlement is often called elastic settlement. It is also referred to as immediate settlement in some geotechnical reports. The question is: which one of these terminologies is more appropriate and better represents the nature of soil deformations. Unlike steel or aluminium, soil exhibits… 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
Geotechnical engineers use footing allowable bearing pressure as the input load for the estimation of consolidation settlement, a.k.a long-term settlement. It is to be noted that the allowable bearing pressure includes 100% of dead load (D) and 100% of live load (L) . However, ASCE 7-10 allows to use smaller loads for calculation of long-term… Read More