Search for: piers
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    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... 

    Effect of opening dimensions on the relative flexural operation of coupled shear walls

    , Article Asian Journal of Civil Engineering ; Volume 13, Issue 3 , 2012 , Pages 417-427 ; 15630854 (ISSN) Torki Harcheganiu, M. E ; Talaei Taba, B ; Farahbod, F ; Sharif University of Technology
    AJCE  2012
    Effect of openings' dimensions on the relative flexural behavior of adjacent piers (independent or conjugate) in perforated shear walls is addressed. 384 designed models were made and exposed to lateral loads. For middle openings, in addition to the alpha parameter in the literature, the relative flexural behavior of piers in medium-rise buildings can be predicted as function of thickness-to-length ratio of the coupling beam and the ratio of the coupling beam length to the pier length; but in high-rise buildings, it is always conjugate. For corner openings, the alpha parameter must be modified with respect to the number of stories  

    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
    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... 

    Experimental and Numerical Investigation of the Flow Field around Complex Bridge Piers with and without the Scour Hole

    , Ph.D. Dissertation Sharif University of Technology Beheshti, Ali Asghar (Author) ; Ataie Ashtiani, Behzad (Supervisor)
    Local scour around bridge piers is one of the main causes of bridge failures Application of existing equations to complex flow patterns is problematic and often leads to questionable results in the field applications. A lack of understanding of the complex flow field and erosion mechanisms seems to be at least partly responsible for this state. Despite the rapid expansion of the literature on the flow around cylindrical piers, there are still challenges for flow field comprehension and estimating design scour depths around complex bridge piers. Due to geotechnical and economical reasons, bridge designs often leads to a complex foundation. Laboratory studies of local scour around complex... 

    Experimental Investigation of Flow Pattern around Pile Groups (two piles)

    , M.Sc. Thesis Sharif University of Technology Aslani-kordkandi, Abolfazl (Author) ; Ataie-Ashtiani, Behzad (Supervisor)
    The occurrence and development of scour hole around bridge pier are the main causes of bridge destruction. To predict manner, occurrence, development and final situation of scour hole around pier is the most important in the hydraulic design of bridges. A large number of studies have been performed to estimate the scour depth around piers at simplified laboratory conditions. The available equations from these studies do partly not present acceptable solutions. This issue is especially of great importance to the pile groups. For accurate determination of scour depth, it is required to get a better understanding of the flow and governing mechanism around pier. Although the flow pattern... 

    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... 

    Neural network and neuro-fuzzy assessments for scour depth around bridge piers

    , Article Engineering Applications of Artificial Intelligence ; Volume 20, Issue 3 , 2007 , Pages 401-414 ; 09521976 (ISSN) Bateni, S. M ; Borghei, S. M ; Jeng, D. S ; Sharif University of Technology
    The mechanism of flow around a pier structure is so complicated that it is difficult to establish a general empirical model to provide accurate estimation for scour. Interestingly, each of the proposed empirical formula yields good results for a particular data set. Hence, in this study, alternative approaches, artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS), are proposed to estimate the equilibrium and time-dependent scour depth with numerous reliable data base. Two ANN models, multi-layer perception using back-propagation algorithm (MLP/BP) and radial basis using orthogonal least-squares algorithm (RBF/OLS), were used. The equilibrium scour depth was... 

    Numerical Analysis of Flow Pattern around Pile Groups (Two Piles)

    , M.Sc. Thesis Sharif University of Technology Dashtpeyma, Hamed (Author) ; Ataie Ashtiani, Behzad (Supervisor) ; Beheshti, Ali Asghar (Co-Advisor)
    Numerical simulations and large eddy simulations (LES) of turbulent flow around single pile, circular tandem piles, circular and square side-by-side piles at different spacing ratios (centre to centre distance to the pile diameter) with flow Reynolds number of 105 on the fixed flat-bed are presented. The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns around single and side-by-side piles with that of the experimental measurements. At the downstream of single pile,... 

    Using Base Isolators in Bridges to Reduce the Dynamic Forces of Piers and Abutments

    , M.Sc. Thesis Sharif University of Technology Kohani Khoshkbijari, Reza (Author) ; Jahanshahi, Mohsen (Supervisor)
    In recent years, the application of base isolation as a seismic design strategy for reducing the effects of earthquake ground motion has become an advantageous method and much effort has been devoted to base isolation research and there has been a growing acceptance of this approach. In this research, the effect of using base isolators in reducing the dynamic forces of piers and abutments of bridges is studied. More specifically double-span bridges are the target of this research. After modeling a regular bridge in a typical analysis program, it is excited by different earthquake accelerograms and then the effect of using base isolators in dissipating the earthquake energy is investigated  

    Flow field around single and tandem piers

    , Article Flow, Turbulence and Combustion ; Volume 90, Issue 3 , April , 2013 , Pages 471-490 ; 13866184 (ISSN) Ataie Ashtiani, B ; Aslani-Kordkandi, A ; Sharif University of Technology
    The present study provides a comparison between the flow pattern around two circular piers in tandem and a single pier set up on a moderately rough flat bed in a laboratory flume. Velocities are measured by an Acoustic Doppler Velocimeter (ADV). The contours of the time-averaged velocity components, Reynolds shear stresses, turbulence intensities and turbulence kinetic energy at different planes are presented. Streamlines and vectors are used to study the flow features. The analysis of power spectra around the piers is also presented. The results show that the presence of downstream pier changes the flow structure to a great extent, particularly in the near-wake region. Within the gap... 

    Influence of unsteady flow hydrograph shape on local scouring around bridge pier

    , Article Proceedings of the Institution of Civil Engineers: Water Management ; Volume 165, Issue 9 , October , 2012 , Pages 473-480 ; 17417589 (ISSN) Borghei, S. M ; Kabiri-Samani, A ; Banihashem, S. A ; Sharif University of Technology
    ICE Pub  2012
    Accurate estimation of scour depth is needed for economic and safe determination of bridge pier foundation depth. Most design criteria are based on maximum scour depth due to the steady design discharge without flow time limit. In this paper, the results are presented of an experimental investigation on local scouring around a single bridge pier under steady and unsteady flow regimes. For unsteady flow, triangular shape hydrographs with repeatable peaks have been chosen. Results show that both sharp and flat increases to the peak of hydrographs have a negligible effect on scour depth for the same base time. An equation is obtained to compute the scour depth due to a specific triangular... 

    Bearing Capacity and Settlement Analysis of Intermediate Foundation (Short Rammed Aggregate Piers)

    , M.Sc. Thesis Sharif University of Technology Dashtara, Sadegh (Author) ; Pak, Ali (Supervisor)
    Using short rammed aggregate piers (RAP) is one of the ground improvement methods that is suitable for loose sands and soft clays. In this method, gravel or crushed stone is placed in layers with specific thickness in a pre-drilled cavity and each layer is fully compacted with impacts of a hammer. The basic advantages of these piers are increasing soil lateral stresses due to aggregate ramming and increasing the consolidation rate due to high permeability of aggregates. The main application of RAPs is soil improvement underneath shallow foundations, in order to increase the bearing capacity and reduce settlement of foundation. Regarding the usual height of 1.5 to 5m of these piers, a... 

    Comparison between Performance of Stone Columns and RAPs from the Bearing Capacity and Settlement Reduction Viewpoints

    , M.Sc. Thesis Sharif University of Technology Golestani Dariani, Ali Akbar (Author) ; Pak, Ali (Supervisor)
    Out of several ground improvement techniques available, stone columns have been widely used. This technique has been successfully applied to increase the bearing capacity and to reduce the settlement for foundation of structures like liquid storage tanks, earthen embankments, raft foundations, etc., where a relatively large settlement is permissible. This technique has, generally, been proven successful in increasing the stiffness of weak soils, upgrading their safe bearing capacity, and reducing their total and differential settlements, as well as speeding up their consolidation process. The beneficial effects of stone column installation in weak deposits is manifested in the form of... 

    Identification of Damage Type and Location in Reinforced Concrete Piers of Slab– Beam Bridges Using Numerical Methods

    , M.Sc. Thesis Sharif University of Technology Hemmati, Omid (Author) ; Ahmadizadeh, Mahdi (Supervisor)
    Bridges are among the crucial elements of transportation networks, and play an important role in facilitating emergency relief efforts following earthquakes. For this reason, it is emparative to monitor their damages to ensure about their performace in earthquakes. The structure of a bridge is divided into two parts, namely the superstructure and substructure. Due to the relatively high rigidity and strength of superstructures, most of structural damage is usually concentrated in substructures, which may ultimately affect the overall stability of the bridge. Therefore, assessing the level of damage in the substructure is of utmost concern. This research attempts to evaluate the damage in the... 

    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
    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... 

    Numerical investigation and field monitoring of karun bridge abutment

    , Article 33rd CSCE Annual Conference 2005, Toronto, ON, 2 June 2005 through 4 June 2005 ; Volume 2005 , 2005 , Pages GC-253-1-GC-253-8 ; 1894662091 (ISBN); 9781894662093 (ISBN) Bayat, A ; Sadaghiani, M. H ; Sharif University of Technology
    Karun Bridge is part of a national highway project underway in southern Iran. The bridge is a 336 m steel arch structure that weighs more than 2500 tons and crosses the Karun River 270 meters above the river valley. The bridge will be the largest suspended bridge in the Middle East. Cantilever construction is to be used to construct the bridge from both sides simultaneously. The weight of the bridge is to be carried by two abutments and four piers that are anchored to exposed weathered rock mass. Loads on the abutments and piers include significant cantilever loads and moments during bridge erection and wind loads. Daily rapid temperature changes also will impart significant thermal loads on... 

    Scour hole influence on turbulent flow field around complex bridge piers

    , Article Flow, Turbulence and Combustion ; Volume 97, Issue 2 , 2016 , Pages 451-474 ; 13866184 (ISSN) Beheshti, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
    Springer Netherlands 
    Experimental results of detailed flow measurements using an Acoustic-Doppler Velocimeter (ADV) around a complex bridge pier (CBP) are presented. The pier consists of a column, a pile cap (PC) and a 2×4 pile group. The time-averaged velocities, turbulence intensities, and Reynolds stresses are studied and presented at different horizontal and vertical planes. Streamlines obtained from the velocity fields are used to show the complexity of the flow around the pier. It is shown that the main feature of the flow responsible for the entrainment of the bed sediments is a contracted (pressurized) flow below the PC toward the piles. A deflected flow around the PC and a strong down-flow along its... 

    Experimental study of a replaceable steel coupling beam with an end-plate connection

    , Article Journal of Constructional Steel Research ; Volume 122 , 2016 , Pages 138-150 ; 0143974X (ISSN) Farsi, A ; Keshavarzi, F ; Pouladi, P ; Mirghaderi, R ; Sharif University of Technology
    Elsevier Ltd  2016
    In order to enhance the post-damage repair capability of the hybrid coupled shear wall systems, a different type of replaceable steel coupling beam with end-plate connection was investigated. Different from conventional configurations, the coupling beams were not embedded into the walls to minimize the post-event repair/replacement difficulties and expenses. To assess the seismic behavior and post-damage replaceability of the coupling beam, a two-stage experimental program was performed to test the full-scale specimens, each utilizing coupling beams with different strength and stiffness. The results of the first specimen indicated a ductile failure with a concentration of inelastic... 

    Restoration of historical Al-Askari shrine. II: Vulnerability assessment by numerical simulation

    , Article Journal of Performance of Constructed Facilities ; Volume 30, Issue 3 , 2016 ; 08873828 (ISSN) Yekrangnia, M ; Aghababai Mobarake, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    This paper presents the results of a vulnerability assessment of the damaged Al-Askari shrine located in Samarra, Iraq by finite element analysis. Reliable material characteristics are derived using limited experimental data on this historical building in order to be utilized in the numerical models. It is concluded that the cracked piers are not vulnerable under the weight of the newly added dome. However, the cracks in the piers widen under design seismic loads, which results in unbalanced settlements in the piers and torsional cracks in the dome. The vulnerability of the minarets is more severe, necessitating heavy reinforcement at their bases and adequate anchorage to the masonry... 

    Flow field around side-by-side piers with and without a scour hole

    , Article European Journal of Mechanics, B/Fluids ; Volume 36 , 2012 , Pages 152-166 ; 09977546 (ISSN) Ataie Ashtiani, B ; Aslani Kordkandi, A ; Sharif University of Technology
    The present study provides the experimental results of the flow pattern around two-circular piers positioned in side-by-side arrangement. The experiments were performed for two bed configurations (with and without a scour hole). Velocities were measured by an Acoustic Doppler Velocimeter (ADV). Flat bed and scour hole were frozen by synthetic glue to facilitate the performance of the experiments. The contours and distributions of the time-averaged velocity components, turbulence intensities, turbulence kinetic energy, and Reynolds stresses at different horizontal and vertical planes are presented. Streamlines and velocity vectors obtained from time-averaged velocity fields are used to show...