Search for: pile-group
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    Estimation of current-induced pile groups scour using a rule-based method

    , Article Journal of Hydroinformatics ; Volume 15, Issue 2 , September , 2013 , Pages 516-528 ; 14647141 (ISSN) Ghaemi, N ; Etemad-Shahidi, A ; Ataie-Ashtiani, B ; Sharif University of Technology
    Scour phenomenon around piles could endanger the stability of the structures placed on them. Therefore, an accurate estimation of the scour depth around piles is very important for engineers. Due to the complexity of the interaction between the current, seabed and pile group; prediction of the scour depth is a difficult task and the available empirical formulas have limited accuracy. Recently, soft computing methods such as artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) have been used for the prediction of the scour depth. However, these methods do not give enough insight into the generated models and are not as easy to use as the empirical formulas. In... 

    Discussion of “Neuro-fuzzy GMDH systems based evolutionary algorithms to predict scour pile groups in clear water conditions” by M. Najafzadeh

    , Article Ocean Engineering ; Volume 123 , 2016 , Pages 249-252 ; 00298018 (ISSN) Beheshti, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
    Elsevier Ltd 
    The author utilized neuro-fuzzy based group method of data handling (NF-GMDH) to predict the local scour depth around pile groups under clear-water conditions. They collected the datasets from literature. To predict the local scour by using NF-GMDH, nine dimensional parameters were considered to define a functional relationship between input and output variables. The results of NF- GMDH networks were compared with that of the empirical equations. However, the collected datasets for pile group scouring, the method of implementing the empirical formula to calculate scour depth, and using the equation of Sheppard et al. (2004) suggested for single pier to predict local scouring around pile... 

    Investigating the Behavior of the Group Energy Pile in Unsaturated Silty Sand Soil Using Physical Modelling

    , M.Sc. Thesis Sharif University of Technology Fardin Jafarzadeh (Author) ; Jafarzadeh, Fardin (Supervisor)
    A physical model has been developed in the advanced soil mechanic lab of the sharif university of technology. This model has been used to investigate the thermo-hydro-mechanical behavior of the group energy pile, which was embedded in the unsaturated silty sand soil. This model contains a steel soil box, 4 aluminum piles, strain gauges, the total pressure cells, the thermocouples, and the mechanical load. Three sets of tests were conducted on these piles. In the first the thermal cycles were applied on 1 pile and in the second and third tests, the number of the energy piles was 2 and 3, respectively. The result has shown there was a permanent settlement at the end of the thermal cycles.... 

    Scour hole depth prediction around pile groups: review, comparison of existing methods, and proposition of a new approach

    , Article Natural Hazards ; Volume 88, Issue 2 , 2017 , Pages 977-1001 ; 0921030X (ISSN) Amini Baghbadorani, D ; Beheshti, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
    A dataset of 365 laboratory tests for scour hole depth (SHD) around pile groups (PGs) under unidirectional aligned flow is compiled, and the performances of the existing equations are comparatively evaluated on the dataset using several statistical indices. A formulation based on a correction of HEC-18 equation provides the best estimate with a correlation factor of 0.58. The test durations of the considered data ranged between 4 and 389 h. A time factor (Kt) is proposed to take into account the temporal variation of the SHD around different PGs. Among the datasets, 51 long-duration experiments are scrutinized to show the temporal variation of scour depth toward equilibrium state. The time... 

    Soil-pile Inelasticity Effect on Displacement Response of Piled Structures

    , M.Sc. Thesis Sharif University of Technology Bagheri Jeddi, Ashkan (Author) ; Mohtasham Dolatshahi, Kiarash (Supervisor)
    The common approach toward soil-pile-structure interaction phenomenon is that it will cause an increase in both effective natural period and damping ratio. Therefore, considering such a phenomenon in design and analysis of piled structures, will lead to smaller displacements. This attitude has gone far in a way that in different suggestions in various practices, this subject is neglected in a conservative manner. In this study, by investigating the response of a single degree of freedom structure founded on a pile group as the first vibrational mode of a structure, by the means of calculating several displacement ratios, has been proved that soil-pile-structure interaction can cause an... 

    E ectiveness of a vertical micropile system in mitigating the liquefaction-induced lateral spreading e ects on pile foundations: 1 g large-scale shake table tests

    , Article Scientia Iranica ; Volume 29, Issue 3 A , 2022 , Pages 1038-1058 ; 10263098 (ISSN) Kavand, A ; Haeri, S. M ; Raisianzadeh, J ; Afzalsoltani, S ; Sharif University of Technology
    Sharif University of Technology  2022
    Liquefaction-induced lateral spreading caused severe damages to pile foundations during past earthquakes. Micropiles can be used as a mitigation strategy against lateral spreading e ects on pile foundations. However, the available knowledge about the possible efficiency of this strategy is quite limited. In this regard, the present study aims to evaluate the e ectiveness of a vertical micropile system as a lateral spreading countermeasure using large-scale 1 g shake table tests on 3 x 3 pile groups. The results showed that the micropile system was not able to e ectively reduce the bending moments in piles; however, it considerably reduced the lateral soil pressures exerted on the upslope... 

    , M.Sc. Thesis Sharif University of Technology Padash, Hadi (Author) ; Haeri, Mohsen (Supervisor)
    During the past earthquakes in all over the world, the piles have had serious damages in soils with liquefaction potential. During an earthquake, liquefaction occurs in some parts of ground with mild slope and saturated and soft granular soil. Afterwards lateral spreading induced by liquefaction incurs irreparable damages on structures and piles particularly. Observing these damages, the researchers and engineers have conducted more surveys and investigations to studying the behavior of piles in granular soils with liquefaction potential and also interactions between  soil  and pile.  In  these  researches,  they have  modeled  the  interactions between  soil  and pile.  However  there are ... 

    Study of the behavior of pile groups during lateral spreading in medium dense sands by large scale shake table test

    , Article International Journal of Civil Engineering ; Vol. 12, Issue. 3 , 2014 , pp. 374-391 ; ISSN: 17350522 Kavand, A ; Haeri, S. M ; Asefzadeh, A ; Rahmani, I ; Ghalandarzadeh, A ; Bakhshi, A ; Sharif University of Technology
    In this paper, different aspects of the behavior of 2×2 pile groups under liquefaction-induced lateral spreading in a 3-layer soil profile is investigated using large scale 1g shake table test. Different parameters of the response of soil and piles including time-histories of accelerations, pore water pressures, displacements and bending moments are presented and discussed in the paper. In addition, distribution of lateral forces due to lateral spreading on individual piles of the groups is investigated in detail. The results show that total lateral forces on the piles are influenced by the shadow effect as well as the superstructure mass attached to the pile cap. It was also found that... 

    Investigation on the Effect of Liquefaction-Induced Lateral Spreading on a Flexible Pile Group and Mitigation Measures for These Effects by Physical Modeling

    , M.Sc. Thesis Sharif University of Technology Raisianzadeh, Javad (Author) ; Haeri, Mohesn (Supervisor)
    Liquefaction-induced lateral spreading is a known cause of severe damages to deep foundations during past earthquakes. Lateral spreading often takes place in gently sloping grounds which consisted of saturated loose cohesionless soil deposits. Several researchers during recent years have been studying the behavior of piles and soil-pile interaction under lateral spreading but there are still many unknowns in this regard. Also with observing catastrophic damages during past earthquakes caused by lateral spreading, developing proper mitigation measures for existing vulnerable piles against this phenomenon is a necessary act. In the present research, the behavior of a 3x3 flexible pile group... 

    Effect of Lateral Spreading Due to Liquefaction on Piles, Numerical Simulation with OpenSees

    , M.Sc. Thesis Sharif University of Technology Ghasemi Fard, Ali (Author) ; Haeri, Mohsen (Supervisor)
    Lateral spreading due to liquefaction and resulting destruction of buildings is important in Iran because of high seismicity and important infrastructure near south and north coasts of Iran. Lateral spreading is vast lateral movement of sloping ground or level ground ending in an opening like river which is caused by earthquake inducedliquefaction. For considering the effects of lateral spreading during design of deep foundations of structures in a susceptible area, one needs to determine the lateral loads on piles under lateral spreading. Present study investigates the behavior of a 3x3 pile group against lateral loads due to lateral spreading with numerical methods using OpenSees software.... 

    Numerical Study of Pile Behavior under Seismic Loading

    , M.Sc. Thesis Sharif University of Technology Mashinchian, Mohammad Javad (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of... 

    Numerical Modeling of Pile Bearing Capacity and Group Efficiency under Axial Loading

    , M.Sc. Thesis Sharif University of Technology Mahvelati Shams Abadi, Siavash (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Bearing capacity of piles depends on many factors among which geometrical properties of piles, soil type, and strength properties of soil are of great importance. Based on these parameters, several approaches have been developed in order to overcome the uncertainty in the prediction of pile bearing capacity. Studies carried out in this area or research can be divided into two main categories: first, laboratory based approaches, and second, numerically based approaches. The research followed in the present study is based on numerical modeling. In this study, a single pile is initially modeled in the axisymmetric configuration and its bearing capacity is determined. The results of the model... 

    Prediction of Scour Depth Around Complex Piers Using Classification Methods

    , M.Sc. Thesis Sharif University of Technology Amini Baghbadorani, Danial (Author) ; Ataie-Ashtiani, Behzad (Supervisor) ; Jamali, Mirmosaddegh (Co-Advisor)
    In this study, existing prediction methods of maximum scour depth around complex piers are studies using available experimental data and a new relationship for scour prediction is presented. Complex pier consists of a column, pile cap and pile group and is frequently used for foundation of bridge piers in hydraulic and marine structures. The results of 52 clear-water scour experiments on 4 CP models are reported which can be valuable to hydraulic design of a CP. The 4 models had different values of pile cap thickness and number of piles inline with the flow and were tested at different pile cap elevations. The duration of experiments ranged from 24 to 120 hours. Then a database of laboratory... 

    Numerical Modeling of the Dynamic Behavior of Piles and Pile Groups Due to Liquefaction- Induced Lateral Spreading

    , M.Sc. Thesis Sharif University of Technology Pakzad, Amin (Author) ; Haeri, Mohsen (Supervisor)
    The phenomenon of lateral spreading occurs as a consequence of earthquakes induced liquefaction in grounds with mild slopes or ending to an opening. This phenomenon has caused many damages to deep foundations and associated structures. Therefore, it is necessary to study and estimate the forces which may be induced by lateral spreading to these structures. Due to the complex mechanism of the effect of lateral spreading on the piles, various tests have been carried out in the form of shaking table as well as centrifuge tests. According to the results of these tests, the forces applied to the piles are significant and can cause crucial damages to deep foundations. On the other hand, because... 

    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
    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... 

    A case study on the soil–pile–structure interaction of a long span arched structure

    , Article Structure and Infrastructure Engineering ; Volume 12, Issue 12 , 2016 , Pages 1614-1633 ; 15732479 (ISSN) Kildashti, K ; Dolatshahi, K. M ; Mirghaderi, R ; Sharif University of Technology
    Taylor and Francis Ltd  2016
    Different concepts for modelling of soil-foundation in complete dynamic interaction analysis for a 110-m height 70-m span arched structure on 180 piles were investigated in this paper. The modelling approaches consisted of a sophisticated procedure to account for soil compliance and foundation flexibility by defining frequency-dependent springs and dashpots; namely, flexible-impedance base model. The results of this model were compared with those of the conventional modelling procedures; namely, fixed base model and flexible base model by defining frequency-independent springs. In the flexible-impedance base model, the substructure approach was employed through finite element modelling. To... 

    Effects of Liquefaction on 2×2 and 3×3 Stiff and Flexible Pile Groups

    , M.Sc. Thesis Sharif University of Technology Goudarzi, Anahita (Author) ; Haeri, Mohsen (Supervisor)
    Liquefaction has a profound effect on buildings, bridges, buried pipes and other engineering structures. This phenomenon can lead to the sliding of huge earth masses, submersion and bending of substantial structures, uplift of buried light structures and collapse of retaining walls. In recorded earthquakes, liquefaction has caused major damage to structures and deep foundations, proving that pile foundations are not designed to withstand at liquefaction condition. Considerable damages in pile foundations due to liquefaction in destructive earthquakes has called for extensive study and research concerning the behavior and response of piles under the influence of liquefaction, resulting in... 

    Numerical Simulation of Effect of Lateral Spreading Due to Liquefaction on Piles and Estimate Soil Lateral Displacement Pattern by Image Processing

    , M.Sc. Thesis Sharif University of Technology Sayaf, Hiva (Author) ; Haeri, Mohsen (Supervisor)
    In recent earthquakes piles have been severely damaged due to liquefaction-induced lateral spreading. Liquefaction causes lateral spreading in gently sloped saturated soft granular soils, leading to significant damage in structures and deep foundations. Although in recent years many studies have focused on different aspects of this phenomenon, the complex nature of the dynamic interaction between piles and liquefied soil is not yet fully understood. This potential damages are of high degree of importance in southern and northern coastal areas of Iran where several ports and critical facilities are located. The present study focuses on the behavior of a 2x2 pile group against lateral loads... 

    An Investigation On The Effects Of Liquefaction Induced Lateral Spreading on a 3×3 Pile Group Using Shake Table Test and Laminar Shear Box and Consideration of Boundary Conditions on Physical Model Results

    , M.Sc. Thesis Sharif University of Technology Salaripour, Saman (Author) ; Haeri, Mohsen (Supervisor)
    Lateral spreading is defined as finite lateral displacement of mildly sloping grounds or those ending in free faces induced by liquefaction. Severe damages of pile groups due to lateral spreading in past earthquakes has been reported. Since earthquake is unavoidable, it is necessary to study the response of piles, especially pile groups, to liquefaction induced lateral spreading. Until now, a number of methods have been developed by researchers for design of deep foundations against lateral spreading, but reported failure of piles in last earthquakes indicates that these methods are associated with high uncertainties. This is due to the lack of laboratory and experimental data to evaluate... 

    Investigation of Group Pile Behavior under Lateral Loads in Clayey Soils

    , M.Sc. Thesis Sharif University of Technology Koohsari, Ali (Author) ; Pak, Ali (Supervisor)
    Piles are usually used in groups. The complicated interaction between piles on the one hand and between piles and their surrounding soil on the other hand, have made it difficult to recognize mechanisms that influence the pile group behavior and analyze it accurately. In this research, three dimensional models in ABAQUS software were used to investigate response of single piles and pile groups under lateral loading in clayey soils. Configuration of piles in a group, connection of piles to the pile cap, pile spacings, and pile cross section were taken into consideration as some important factors affecting response of pile groups. All the modeled piles were categorized as long piles. In order...