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    Numerical Study of Ground Vibrations due to Pile Driving and Effect of Trench on Reduction of Amplitude of Vibrations

    , M.Sc. Thesis Sharif University of Technology Khoubani, Ali (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Abstract
    Ground vibration during pile driving is one the most important factors that limits usage of this kind of piles. It is of great importance to estimate the level of vibration prior to the beginning of pile driving to avoid structural damage or disturbance of building occupants. In this study, an axisymmetric finite element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code ABAQUS, to simulate the full penetration of a pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particles velocity with those measured in the field. The results indicate that the peak... 

    Experimental investigation of clear-water local scour of compound piers

    , Article Journal of Hydraulic Engineering ; Volume 136, Issue 6 , June , 2010 , Pages 343-351 ; 07339429 (ISSN) Ataie Ashtiani, B ; Baratian Ghorghi, Z ; Beheshti, A. A ; Sharif University of Technology
    2010
    Abstract
    Local scour around complex piers under steady clear-water condition was studied experimentally for a variety of configuration, including different sizes and shapes of complex piers. A total of 70 experiments were carried out. Three sets of experiments were performed over the entire range of possible pile cap elevations for complex piers with different geometrical characteristics. The collected data are used to quantify the pile cap elevations that maximize or minimize the local scour depth. Some of the available methodologies to estimate the maximum local scour depth around such complex piers are evaluated. The predictions of the scour depths improved by using the revised methods of... 

    Numerical Pile Driving Analysis by FLAC2D (With special issue on quake parameters)

    , M.Sc. Thesis Sharif University of Technology Hashemi, Saeed (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Abstract
    Nowadays, pile usage in construction of deep foundations has increased significantly, instead of shallow foundation in areas that shallow foundations doesn’t provide enough bearing capacity and measuring the velocity and acceleration due to pile driving is very important. Because, all responses of building and individuals located near the pile driving site influenced by these three parameters: pile vertical displacement, peak particle acceleration (PPA) and peak particle velocity (PPV). One can estimates these important parameters by numerical analysis of pile driving process in different distances and depths to determining the effect of pile driving. Compared values obtained from numerical... 

    Prediction of current-induced local scour around complex piers: Review, revisit, and integration

    , Article Coastal Engineering ; Volume 133 , 2018 , Pages 43-58 ; 03783839 (ISSN) Amini Baghbadorani, D ; Ataie Ashtiani, B ; Beheshti, A ; Hadjzaman, M ; Jamali, M ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    Complex piers (CPs), consisting of a column, pile cap and pile group, are commonly built as foundations for hydraulic and marine structures. Scour-hole development around CPs is studied in this paper. A total of 52 tests is carried out on 4 CP models, with experiments durations ranging from 24 to 120 h. All of the available experimental data for clear-water scour around CPs including the collected data of the present study and those previously published are reviewed and combined into a database. A special case of bridge piers with deep foundation or caisson instead of pile caps is also considered, which is herein called compound piers. The database contains 367 experiments for CPs and 162... 

    A numerical approach on side resistance of drilled shafts embedded in sandy soils

    , Article International Journal of Geotechnical Engineering ; Volume 14, Issue 6 , 2020 , Pages 644-652 Jazebi, M ; Ahmadi, M. M ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs... 

    Numerical study of ground vibration due to impact pile driving

    , Article Proceedings of the Institution of Civil Engineers: Geotechnical Engineering ; Vol. 167, issue. 1 , August , 2014 , p. 28-39 ; 13532618 Khoubani, A ; Ahmadi, M. M ; Sharif University of Technology
    Abstract
    Ground vibration due to pile driving is a long-lasting concern associated with the foundation construction industry. It is of great importance to estimate the level of vibration prior to the beginning of pile driving, to avoid structural damage, or disturbance of building occupants. In this study, an axisymmetric finite-element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code Abaqus, to simulate full penetration of the pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particle velocities with those measured in the field. The results indicate that the... 

    Estimation of current-induced scour depth around pile groups using neural network and adaptive neuro-fuzzy inference system

    , Article Applied Soft Computing Journal ; Volume 9, Issue 2 , 2009 , Pages 746-755 ; 15684946 (ISSN) Zounemat Kermani, M ; Beheshti, A. A ; Ataie Ashtiani, B ; Sabbagh Yazdi, S. R ; Sharif University of Technology
    2009
    Abstract
    The process of local scour around bridge piers is fundamentally complex due to the three-dimensional flow patterns interacting with bed materials. For geotechnical and economical reasons, multiple pile bridge piers have become more and more popular in bridge design. Although many studies have been carried out to develop relationships for the maximum scour depth at pile groups under clear-water scour condition, existing methods do not always produce reasonable results for scour predictions. It is partly due to the complexity of the phenomenon involved and partly because of limitations of the traditional analytical tool of statistical regression. This paper addresses the latter part and... 

    Experimental study of three-dimensional flow field around a complex bridge pier

    , Article Journal of Engineering Mechanics ; Volume 136, Issue 2 , 2010 , Pages 143-154 ; 07339399 (ISSN) Beheshti, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
    2010
    Abstract
    In this paper, three-dimensional turbulent flow field around a complex bridge pier placed on a rough fixed bed is experimentally investigated. The complex pier foundation consists of a column, a pile cap, and a 2×4 pile group. All of the elements are exposed to the approaching flow. An acoustic-Doppler velocimeter was used to measure instantaneously the three components of the velocities at different horizontal and vertical planes. Profiles and contours of time-averaged velocity components, turbulent intensity components, turbulent kinetic energy, and Reynolds stresses, as well as velocity vectors are presented and discussed at different vertical and horizontal planes. The approaching...