EFFECT OF PRYING ACTION FORCES ON DESIGN METHOD OF SEMI-RIGID BOLTED CONNECTIONS
Y.
Hosseinzadeh
Faculty of Civil Engineering University of Tabriz
author
M.A.
Lotfollahi Yaghin
Faculty of Civil Engineering University of Tabriz
author
M.R.
Farajpour
Faculty of Civil Engineering University of Tabriz
author
text
article
2012
per
In this study, the behavior of end plate connections with various rigid has been studied. After the creation of the finite element models. model accuracy is evaluated using the experimental results. Maximum error of finite element models generated is estimated at about 8 percent. With parametric analysis semi rigid connections, an important factor influencing the behavior of the connections is detected. The prying action is one of the most significant parameters in connections behavior; lack of attention to this phenomenon in the design phase will cause errors in calculation. To calculating the prying action force in T connections, two experimental methods exist. The computational method of Smith and AISC, the amount of computational error in smith method,is 80 to 160 percent depending rigidity of end plate connections. In second method, AISC, in connection with semi-rigid end plate, the error is estimated at about 40 percent. To understand how to set formulation AISC, models of the T Connection with variable end plate thickness is made and parametric analysis was performed. Failure mechanism of these connections is shown that in connection with flexible end plate, much of the prying action force is created. In connection with the very rigid plate can be neglected under the conditions of the effect of prying action forces. With comparing the stress distribution in flexible, rigid and T connections, the geometric coefficient of 3 row bolted end plate connections is considered 1 25 and in 2 row bolted 0.5 The maximum error of calculating the prying action force is about \%5. Using the improved method, in semi rigid connections, the need to calculate the prying action and no need to calculate it is characterized. Having the exact amount of prying action forces. animproved design method has been authorized based on the philosophy and methods of allowed stress. In this method, 22 percent reduction in design error has been observed.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
3
13
https://sjce.journals.sharif.edu/article_681_9b6493e6319f847890bef2d2aafd87b8.pdf
EVALUATION OF THE EFFECTS OF HYDRAULIC AND MECHANICAL PARAMETERS ON THE \r\nWATER COEFFICIENT OF PERMEABILITY OF A CLAYEY SAND WITH A NOVEL PERMEAMETER FOR \r\nUNSATURATE
G.
Adelian
Geotechnical Engineering\r\nTarbiat Modares University
author
S.S.
Yasrobi
Geotechnical Engineering\r\nTarbiat Modares University
author
A.
Mirzaii
Geotechnical Engineering\r\nTarbiat Modares University
author
text
article
2012
per
In this paper, the influence of hydraulic parameters of soil-water characteristic curve hysteresis and water flow head and the mechanical parameters of net confining stress and specimen height are evaluated on the unsaturated water coefficient of permeability of a clayey sand. For this, a series of unsaturated permeability tests are carried out on the understudying soil with a novel flexible wall permeameter for unsaturated soils designed and built in Tarbiat Modares University. The novel permeameter is capable to quantify air and water coefficients of permeability of unsaturated soils in various flow states at different isotropic confining stress. This apparatus is composed of a flexible wall permeameter cell, pressure panel, and flow and volume change measuring systems. The cell of the apparatus is capable to distinctly control or measure the variation of pore air and pore water pressures in top and bottom of samples in various consolidation stresses. Positive and negative pressures of the apparatus were set with the precision pressure regulators in pressure panel. The proper de-aired water for permeability tests was also generated inside the pressure panel. Also, the apparatus enables automatic measurement of the inlet/outlet water volume of the soil sample with the accuracy of 0.01 cubic centimeters. The effect of hydraulic hysteresis and flow head on water coefficient of permeability is assessed through a set of tests on samples with the height of 1 cm for two flow heads of 40 and 80 kPa and in matrix suctions of 40 and 100 kPa on wetting curve and matrix suction of 100 kPa on drying curve. These tests were also repeated on samples with the height of 3 cm just in for the water flow head of 40 kPa to evaluate the effect of soil thickness on the water coefficient of permeability. The effect of net confining stress on permeability of understudying soil is also assessed through a set of tests on soil samples with the height of 1 cm and matrix suction of 100 kPa on wetting curve in flow head of 40 kPa and net confining stress of 100 and 200 kPa. The experimental results indicate that for constant matrix suction, the water coefficient of permeability attained in drying cycle is more than similar values on wetting cycle. Additionally along each of drying or wetting curves, the water coefficient of permeability increases with reduction of matrix suction. Further, the hydraulic conductivity of understudying soil appeared to be independent of applied heads and Dacry law was valid for the range of water flow heads. The experimental results also corroborated that any change of the soil thickness has only increased the required time to reach a steady state for water flow, and the water permeability of soil samples was independent of the sample thickness.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
15
24
https://sjce.journals.sharif.edu/article_682_94ab6150d41884b7350979cb10166879.pdf
EVALUATION OF DIRECT DISPLACEMENT BASED METHOD FOR SEISMIC DESIGN OF REINFORCED CONCRETE SHEAR WALLS
M.
Shabdin
Dept. of Civil and Environmental \r\nEngineering Tarbiat Modares
author
M.
Soltani
Dept. of Civil and Environmental \r\nEngineering Tarbiat Modares University
author
text
article
2012
per
The purpose of this study is to evaluate the direct displacement based seismic design (DDBD) method in the design of reinforced concrete shear walls.Direct Displacement- Based Design has been developed by Priestley et al with the aim of mitigating the deficiencies in current force-based design. In this method displacement leads to strength which inverts the process of traditional force-based design where strength leads to an estimate of displacement.For this purpose, four reinforced concrete shear walls with different heights (4, 8, 12 and 16 floors) are considered and designed based on the displacement based seismic design method for a specified drift at roof level.Nonlinear time history analyses method with incremental acceleration (IDA) is used in order to analyze the shear walls. By comparing the results of analyses with the design assumptions it can be seen that the displacements predicted by direct displacement based design method conservatively has a considerable difference with the results of time history analyses.Therefore, it is expected that in order to reach a certain displacement, the base shear of shear walls be less than the base shear resulted from DDBD method. With studies done, the reasons of this difference were investigated. For this purpose, some of the assumptions of DDBD method such as Yield curvature, Yield displacement and Base shear and the basis of substitute structure assumption are considered and corrective recommendations are presented. By performing proposed modifications in Direct Displacement Based Design, the designs of shear walls are repeated. In this case in which the design method is based on the modified method, the conformity of analyze results from time history analyses and the design assumption is quite obvious. In this study the nonlinear beam-column element is used to model reinforced concrete shear walls and confirmed using WCOMD finite element software. Numerical modelling and analyses of shear walls are performed using OpenSees .
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
25
38
https://sjce.journals.sharif.edu/article_683_de779799d4b0b4d1a4791b06d66a4112.pdf
DETERMINATION OF BEARING CAPACITY FOR PILES USING SYSTEMATIC NUMERICAL ANALYSES OF PILE LOAD TESTING BASED ON TAGUCHI METHOD
M.
Yazdani
Faculty of Civil & Environmental \r\nEngineering Tarbiat Modares University
author
P.
Ghahremani
Faculty of Civil & Environmental \r\nEngineering Tarbiat Modares University
author
text
article
2012
per
Determination of bearing capacity of piles is one of the important subjects which always challenge geotechnical engineers. The factors which affect the bearing capacity of a pile in compressive, tensile or lateral loading are consisting of geometrical characteristics of pile such as length and shape of cross section, execution methods (cast in place, driving) and also geotechnical specifications. Due to these numerous factors, a direct estimation of pile baring capacity based on in-situ testing is the most precise and reliable method. However, this method is expensive, time consuming and troublesome . In this regard, geotechnical engineers usually utilize the classic formulations proposed by some soil mechanics pioneers such as Meyerhof, Hansen, and Vesic to estimate the ultimate bearing capacity of piles. However, these relationships may lead to conservative or unsafe designs. Numerical methods, on the other hand, has been a powerful but relatively cheap approach which help engineers to obtain a reasonable estimate of ultimate bearing capacity based on existent soil mechanics parameters. Nevertheless, a wrong determination of geomechanical parameters can lead to a wrong estimation of pile bearing capacity. To overcome those difficulties, a combination of pile loading tests and numerical modeling is able to submit a precise and reasonable cost solution to the problem. In this method, the geometechnical parameters are varied in numerical modeling in such a way that the results of load-settlement curve obtained by a number of numerical analyses find a good agreement with the same curve recorded during in-situ pile test . In this study, a suitable arrangement of all parameters affecting the numerical analysis is introduced based on Taguchi systematic method to allow a good agreement between the results of numerical analysis and pile load testing. Hereby, the accurate soil parameters and the relative importance of each factor which govern the bearing capacity are determined. In this research, the laboratory soil mechanics parameters and the results of pile load testing in a specific site are incorporated into a group of Taguchi analyses to improve the mechanical parameters of soil. The results indicated that the soil-pile interface factor, frictional angle and cohesion of soil are major factors in the bearing capacity, while Poissons ratio and dilation angle play minor roles.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
39
51
https://sjce.journals.sharif.edu/article_684_336ee74aafdd04f98fd7b5dc08739b04.pdf
MODELING THE EFFECT OF EMBANKMENT DAM CONSTRUCTION ON THE LIQUEFACTION POTENTIAL OF ALLUVIUAL FOUNDATION
R.
Mahin Roosta
Dept. of EngineeringTarbiat \r\nModarres University}
author
R.
Naghiloo
Dept. of Engineering \r\n Zanjan University
author
text
article
2012
per
Loose saturated sand and alluvial strata are susceptible to liquefaction during earthquake. Simple and empirical method for evaluating their resistance against liquefaction is based on the results of standard penetration tests (SPT). One of the most important parameter which affects liquefaction resistance is initial stress; Standard procedures for considering this effect require correcting penetration resistances to an equivalent overburden stress of one atmosphere and adjusting the cyclic resistance ratio for the effects of overburden. Liquefaction potential in alluvium will change after construction of heavy structures on them, which is due to changes in earthquake loads, overburden pressures and soil densification. In this paper, a new methodology is explained to calculate changes in compaction of alluvial foundation after dam construction, which influence both shear strength and dynamic shear stresses. With this new formula, one can determine shear strength of alluvium against liquefaction and compare its values with induced dynamic shear stresses to evaluate factor of safety . Effect of dam construction on liquefaction potential of alluvium is investigated through dynamic analysis based on equivalent linear approach. Liquefaction potential of alluvial foundation without dam construction is compared to that potential after construction in two ways; in the first method, effect of induced stresses on liquefaction potential is considered in the numerical analysis based on new stress states and related functions, and in the second method, in addition to these changes, relative density of the alluvium is corrected due to construction; for instance a method is described to update alluvium relative densities and update material parameters. To clarify effectiveness of the dam body on the liquefaction potential of foundation, three different compressibility conditions, i.e. weak, medium and stiff states, are considered in the alluvium to discover changes in factor of safety after dam construction. Results of analyses show that liquefaction potential of alluvial foundation decreases significantly after construction in various alluvial strata. Considering results derived from this study, if selected site for dam construction is prone to liquefaction, engineers might have economic project with keeping alluvium beneath the dam instead of totally excavation.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
53
64
https://sjce.journals.sharif.edu/article_685_4116a91d9aa01227ea81162c94ba54e5.pdf
ASSESSMENT OF PROGRESSIVE COLLAPSE POTENTIAL OF STEEL STRUCTURES THAT ARE DESIGNED ON IRANIAN CODE
F.
Mehrabi
Dept. of Civil Engineering\r\nSemnan University
author
A.
Kheiroddin
Dept. of Civil Engineering\r\nSemnan University
author
M.
Gerami
Dept. of Civil Engineering\r\nSemnan University
author
text
article
2012
per
Progressive collapse is used to refer to the spread of an initial local failure within a structure this local failure is triggered by the loss of one or more load carrying members and leads to partial or total collapse of the structure in a manner analogous to a chain chemical reaction. The partial collapse of Ronan Point apartment in 1968 initiated this subject in Britain, and events of 11 September 2001 have instigated a comprehensive debate among the structural engineering communities regarding the performance of tall buildings under extreme loading conditions such as blast, impact or fire. A wide range of explanations were given in different countries like England, Canada, USA and EU Meanwhile two specific codes were offered for progressive collapse in the USA. These require that all new and existing buildings of three stories or more be designed to avoid progressive collapse. Abnormal loading, large deformation due to fire and etc are reasons of first local failure. The two general approaches currently employed for mitigating the risk of progressive collapse include: 1) the indirect design method, and 2) the direct design method. The former is a prescriptive approach of providing a minimum level of connectivity between various structural components, and therefore it can be readily implemented in structural design without the need for any additional analysis. Instead of calculations investigating the effects of extreme loads on the building, the designer employs an implicit design approach that incorporates measures typically related to strength, continuity and ductility to enhance the overall robustness of the structure. On the other hand, the direct methods rely heavily on structural analysis and, in fact, can significantly benefit from sophisticated analysis techniques, such as nonlinear and/or dynamic analysis, which are not commonly used in routine design practice. Despite all of them there are many problems around progressive collapse event which are unknown. Furthermore, Iranian codes have not yet considered about this subject. Because of these, this study was done on 46 models of structures with differences in heights and the structural systems, which were designed according to Iranian codes, and then they were assessed for potential of progressive collapse due to removed column in different positions in the first floor based on the direct method. Finally it was found that these structures have potential of progressive collapse. This study also shows that many features are effective in progressive events like the number of stories, position of the removed element, the structural system, indetermination due to extra elements, and finally it is concluded that the progressive collapse should be taken consideration in Iranian code.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
65
72
https://sjce.journals.sharif.edu/article_686_59011adde3b2f4bf13cd4eb47b90ec5a.pdf
THREE DIMENSIONAL NON-AXISYMMETRIC VIBRATION ANALYSIS OF A BURIED PIPELINE WITH CONCERNING \r\nSLIP
Y.
Nassira
Dept. of Civil Engineerin Amirkabir University of echnology
author
H.
Rajaie
Dept. of Civil Engineerin\r\nAmirkabir University of Technology
author
text
article
2012
per
The response of the underground pipelines to wave propagation is influenced by many factors, because of large geometrical dimensions of pipelines, wave characteristic lay open to the change of ground motion phase and geotechnical conditions for different points alongside the pipeline axis, provides technical hitches for an efficient solution. Basis on three-dimensional theory of elasticity, in this paper an analytical formulation is presented for vibration analysis of a buried pipeline to study stresses and deformations of an underground pipeline. The succeeded governing equation is applicable for an infinite pipeline which surrounded by an enormous soil medium that lay open to an incident wave plane. The pipe-soil interaction is modeled with concerning to the occurrence slip between pipe and soil medium and in addition the Coulomb frictional-force is supposed equal to the viscous damping on the interface. To investigate the unknown parameters such as, slippage, variation of wave angle as well as damping coefficient of bond, the succeeded algebraic equation is solved analytically. With regarding the elastic limitation, some numerical examples are provided to show the application of the presented model and demonstrate the prediction of the critical value which may cause yielding in the pipe for incident-wave amplitude. The radial and shear stresses for the inside and outside diameter of the pipe are also evaluated in order to show the validity of the results. However, comparisons with some available FEM models display a respectable correlation for stress distribution on a cross sectional of buried pipeline. The effect of some parameters, such as porosity of the soil, thickness of the pipe and also perfect and imperfect bond between soil and buried pipe are discussed and demonstrated with relative graphs.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
73
82
https://sjce.journals.sharif.edu/article_687_b1dfef98c2c8238776b52705947138f6.pdf
EFFECT OF EARTHQUAKE ON DISCRETE CRACK PROPAGATION IN SEFIDRUD DAM USING MULTI REGION DUAL BOUNDARY ELEMENT METHOD IN THE TIME DOMAIN
B.
Omidvar
Faculty of Environment university of Tehran
author
A.A
Noorzad
Faculty of Civil Engineering,\r\n University of Technology
author
M.
Rahimian
Faculty of Civil Engineering,\r\nUniversity of Tehran
author
A.
Sanaeiha
Faculty of Civil Engineering,\r\n University of Tehran
author
text
article
2012
per
In the present study, the effect of earthquake on the crack propagation of Sefidrud dam is presented using the concept of dynamic fracture mechanics. After the introduction of displacement and traction boundary integral equations, the dual boundary element method and multi region boundary element method are mixed to simplify the modeling of complicated configuration of buttress dams. Seismic crack propagation of buttress No.15 of Sefidrud dam is analyzed using the proposed mixed method. Different parts of the dam body and dynamic crack propagation can be modeled easily with regard to simultaneous application of boundary element method and multi-domain dual boundary element method. Also, new elements are added to the previous elements in the crack growth modeling, which causes the reduction of calculation time. Seven cases based on the level and length of initial cracks in the body of the downstream wall is considered. The time domain analysis for stable crack condition is considered in the case A. In other cases (B, C, D, E, F and G), analysis are performed for different unstable crack considering the crack growth and crack faces contact. The effect of initial crack length on the crack propagation in the Sefidrud dam can be observed by comparison of cases B, C and D. When larger initial crack length is considered, the crack reaches to the body of upstream wall before the main shock of acceleration records. Four cases D, E, F and G are analysed for camparison of intial crack level. The results of the present study are in good agreement with the observed crack profiles of the dam after the earthquake. But it is worth to mention that a 3D analyses is preferred for a better simulation.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
83
93
https://sjce.journals.sharif.edu/article_688_eec68b0e5bd91f2ba0d287c1c87db3c2.pdf
A FIELD STUDY ON THE BEHAVIOR OF SINGLE RAMMED AGGREGATE PIERS TOWARDS CHANGES IN DIAMETER
H.R.
Razeghi
Dept. of Civil Engineering\r\nIran University of Science and Technology
author
B.
Niroumand
Dept. of Civil Engineering\r\nIran University of Science and Technology
author
H.
Ghiassian
Dept. of Civil Engineering\r\nIran University of Science and Technology
author
M.
Mansoorzadeh
Transportation Research Institute\r\nIsfahan University of Technology
author
text
article
2012
per
Advantages of technological and economic of rammed aggregate piers system (RAPs) in stabilization of the soft soils are due to develop their applications in civil engineering. Over the last two decades, being of these benefits is the main motivation to develop research in this field. In this study, the effect of RAP diameter has been studied on the bearing capacity, settlement, the stiffness modulus, and the load ratio of RAP. In total, eight in situ loading tests has been done on two groups of single RAPs. The nominal length of RAPs was 1 m and their nominal diameters varied from 105 to 185 mm. The testing area consisted of relatively uniform saturated soft alluvial clay overlain by a 1-m-thick wet soft-to-stiff silt layer. In order to load the rammed aggregate piers, mobile reaction beams, in the form of a loading cart and a modular rail system, were used, both to speed up the tests and to make them more economical. The results show, the rate of increase of the load ratio (tip to top) in RAPs with bigger diameters is considerably higher than the rate of increase of the load ratio (tip to top) in the RAPs with smaller diameter. In addition, by increasing the applied stress at the top of the RAP, the difference is also raised. In fact, the RAPs with smaller diameter are more likely to experience bulging deformation, and the RAPs with bigger diameter are more likely to experience tip deformation. So, in a two-layer soil system which the strong layer is on the weak layer, the use of RAPs with smaller diameter will desirable. Interpretations of the test results are particularly focused on the load-settlement behaviors of the single RAPs, stiffness modulus and the load ratio in terms of stress at the top of the RAPs.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
95
103
https://sjce.journals.sharif.edu/article_689_79f9e3a2f3b2d923dc36650e69675e12.pdf
FREE VIBRATION OF RECTANGULAR CONCRETE LIQUID STORAGE TANKS: EXPERIMENTS AND FINITE ELEMENT ANALYSIS
A.S.
Ghods
Dept. of Civil Engineering\r\nFerdowsi University of Mashhad
author
M. Reza
Esfahani
Dept. of Civil Engineering \r\nFerdowsi University of Mashhad
author
A.H.
Keivani
Dept. of Civil Engineering\r\nFerdowsi University of Mashhad
author
text
article
2012
per
In recent years, researchers have been intensively studied the dynamic response of liquid containers under ground excitation. However, most of the studies were conducted on cylindrical tanks while those concerning rectangular tanks are not adequate. In the early investigations, approximate methods were proposed to include the effect of hydrodynamic pressure for a symmetric fluid container subjected to horizontal acceleration. The fluid response was represented by impulsive and convective components. The fluid was assumed to be incompressible and the container was assumed to have rigid walls. Recently, very strong earthquakes caused heavy damage to many liquid storage tanks. It was concluded that the assumption of a rigid wall may not be appropriate for the structural modeling. Including the wall deformability in a dynamic analysis requires a systematic knowledge and understanding of the fluid-structure free-vibrational characteristics . Modal test is one form of non-destructive testing that may be used to obtain information on the dynamic behavior of actual structures. This type of experimental study is conducted to determine different modal parameters of a structure such as natural frequencies, damping and mode shapes or to verify the theoretical models and predictions. This technique has the advantage of determining the real structural properties without using any assumption and taking into account the actual boundary condition. In this paper, a numerical-experimental study of the overall dynamic response of rectangular concrete tanks is presented. In order to identify the natural frequencies that mainly contribute to the response, modal tests on a rectangular concrete tank model for different liquid levels were carried out. Also, a numerical model that accounts for the interaction between fluid and structure was developed. A very good agreement between experimental and numerical results was obtained. In the numerical study, the influence of the sloshing on the natural frequencies and their modal pressure distribution are investigated. The results indicate that sloshing has a significant effect on the dynamic characteristics of the system; thus, in case where an accurate dynamical analysis is required, the sloshing should be considered.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
105
113
https://sjce.journals.sharif.edu/article_690_cb33f5acc15e88265bbc0d94a94c2ff3.pdf
STUDY OF ENDURANCE TIME METHOD IN SEISMIC ASSESSMENT OF STEEL FRAMES IN DIFFERENT EXCITATIONS LEVELS
A.
Farhadi
Dept. of Civil Engineering\r\n Sharif University of Technology
author
H.
Estekanchi
Dept. of Civil Engineering\r\n Sharif University of Technology
author
A.
Vafai
Dept. of Civil Engineering\r\n Sharif University of Technology
author
T.
Goli
Dept. of Civil Engineering\r\nSharif University of Technology
author
text
article
2012
per
In recent years, most of the major seismic design codes have placed emphasis on Performance Based Design of structures. However, these methods are computationally complex and time-consuming, and encouraged researchers to seek new and efficient methods to investigate performance of structures under different intensities of seismic loading. This paper provides better insight into the dynamic behavior of structures in continuous performance levels by Endurance Time (ET) analysis and uses this method to evaluate seismic performance of Steel Frames. Due to significant reduction in number of time history analyses for assessment of structural response at different intensities, ET method is considered to be a useful tool for conducting practical Performance Based Design of structures. In this procedure, with each analysis of structure under ET acceleration function, the structural response can be estimated in different performance levels. For more precise results, one can use 3 ET acceleration functions and consider the average of responses as the response of structure. Endurance Time analysis is based on time history analysis, however in this method structure is subjected to gradually intensifying acceleration function and different damage indices of the structure are evaluated through analysis time. The different duration of ET acceleration functions, represents diverse intensities of earthquakes in different hazard levels. Various inelastic moment resisting steel frames were investiged in different hazard levels. The performance of the structures under seismic excitation in different performance levels is evaluated based on interstory drift ratios and story shear forces. To ensure accuracy of ET method, the results were compared to the results of nonlinear time history analysis of two sets of ground motions. It was observed that Endurance Time accelerogram led to a very reasonable prediction of structure behavior at various earthquake records. It was also shown that ET predictions are not sensitive to selected ground motions as long as the average spectral intensity remains consistent. Therefore, Endurance Time Method significantly decreases amount of computation in each seismic evaluation analysis. In this research, ASCE-41 is used as the performance base design criterion.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
115
125
https://sjce.journals.sharif.edu/article_691_4e13db037445c433290ec26551e9cb92.pdf
EVALUATION OF LIQUEFACTION POTENTIAL IN MAZANDARAN PROVINCE USING IN-SITU TEST DATA WITH REVIEW OF ISHIHARA CRITERION
H.
Mola Abasi
Civil Engineering Group\r\nFaculty of Engineering Guilan University
author
R.
Jamshidi Chenari
Civil Faculty of Engineering Guilan University
author
text
article
2012
per
Liquefaction-induced damages are more highlighted in saturated fine-sand deposits where huge pore pressure buildup will cause premature strength loss within stratum underneath. The potential for occurrence of liquefaction is directly dependent on factors like soil type, seismicity of the region, location of water table and the overlying non-liquefiable stratum thickness. The current paper will focus on the effect of the overlaying non-liquefiable stratum on the liquefaction potential of the underlying layer which is inherently liquefiable. Ishihara method was invoked for this aim and a corrected safety factor was proposed which considers the effect of liquefiable underlying and non-liquefiable overlying layers depth. In order to implement the suggested liquefaction potential correction scheme to a case in real world, Mazandaran province in North Iran was selected to investigate the liquefaction potential in its different regions. Liquefaction potential was sought by adoption of different criteria. In all the employed criteria, standard penetration test, SPT data was used to calculate the cyclic resistance ratio and the cyclic stress ratio was also estimated according to the seismicity of the region. Then the liquefaction potential is calculated from different methods. Correction is finally applied to the calculated safety factors which reflect the liquefaction potential in different regions. A tentative liquefaction zoning map was then provided for Mazandaran province which enables the engineers to avert uncalled-for situations by emphasizing the necessity of detailed study in zones with high liquefaction potential. The proposed zonnation map is more or less qualitative due to the lack of sufficient test boreholes and also the need for more sophisticated in-situ test schemes. However it can pave the way toward an initial understanding of the liquefaction potential in different urban areas. To be more specific, it is crucially important to pay more attention to the liquefaction issue in some coastal cities like, Babolsar and Mahmoudabad which are heavily populated and potentially liquefiable at the same time. Measurements like deep and mat foundations, gravel or stone columns and wick drains are alternative in case remedial or improvement provisions are necessary. Microzonnation will however need more densely-allocated in-situ test scheme and detailed investigation on the liquefaction potential which is followed according to the importance of the structure and the construction location.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
127
135
https://sjce.journals.sharif.edu/article_692_e37a26df0b2710ed4e019612756ebec7.pdf
LOAD CARRYING CAPACITY DETERMINATION OF PILE DRIVEN IN NONCOHESIVE SOIL \r\nWITH WAVELET NEURAL NETWORK APPROACH
M.A.
Lotfollahi-Yaghin
Faculty of Civil Engineering\r\nUniversity of Tabriz
author
B.
Naderinia
Faculty of Civil Engineering \r\nUniversity of Tabriz
author
A.
Pourtaghi
Faculty of Civil Engineering\\ \r\nUniversity of Tabriz
author
text
article
2012
per
In spite numerous investigations about bearing capacity of a driven pile in noncohesive soil, calculation of that is a complicated trend. Any prediction from numerical analysis was highly dependent on the model adopted for modeling the soil behavior. However, setting up a realistic model that would be able to calculate the Load carrying capacity of pile is rather difficult. Most of the researches show that the capability (i.e. pattern recognition and memorization) of an ANN is suitable for inherent uncertainties and imperfections found in geotechnical engineering problems considering its successful application without any restriction. The combination of the wavelet transforms theory with the basic concept of neural networks leads to a new mapping network called neural network adaptive wavelets or wavenets which is proposed as an alternative to feed-forward neural networks for approximating arbitrary nonlinear functions. A wavelet network is a feed-forward neural network using wavelets as activation functions of its hidden layers neurons. In this network, both the position and dilation of the wavelets are optimized beside the weights. In one special approach of this network construction so called wavenet, the position and dilation of the wavelets are fixed and the weights are optimized. In this research, considering late mentioned procedure for available experimental data, the potential for applying neural network and its adaptive wavelets (wavenets) has been shown for predicting the load carrying capacity of a pile driven in noncohesive soil. The validation tests showed the artificial intelligence solutions clearly outperformed in predictive accuracy under varying training and testing conditions and these methods can be employed for predicting the load carrying capacity of a pile driven in noncohesive soil in comparison with other computational and time consuming methods considering complexity of the soil characteristic. Numerical results indicate that substituting wavelet function as feed-forward neural network transfer functions can enhance the network performance and efficiency. Therefore proposed wavenet with feedforward neural network structure (wavenet) that uses SLOG1 wavelet function as its hidden layer activation functions is much better in comparison to the standard feed-forward in terms of performance generality .
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
137
145
https://sjce.journals.sharif.edu/article_694_0a448fb370ef93543c9ef7746aebe724.pdf
EXPERIMENTAL AND ANALYTICAL STUDY ON CONCENTRICALLY BRACED FRAME SYSTEM COMBINED WITH STEEL SHEAR PANEL
M.
Khazaei-Poul
Structural Engineering Research Center International Institute of Earthquake Engineering and Seismology
author
E.
Alavi
Structural Engineering Research Center International Institute of Earthquake Engineering and Seismology
author
F.
Nateghi-Alahi
Structural Engineering Research Center International Institute of Earthquake Engineering and Seismology
author
text
article
2012
per
The recent researches have demonstrated that thin steel plates have good performance under shear loadings, and upon that property, they have been used in some of the lateral resistant systems such as steel plate shear walls. In the present study, it is intended to employ the shear panels for seismic performance improvement of concentrically braced frames. Hence, a combined system is developed and its non-linear behavior has been analytically and experimentally investigated. For experimental study, a scaled one-story steel shear panel model, with hinge type connections of boundary elements at four corners, is selected. Two rows of bolts with a diameter of 10 mm are used for connections of infill steel plate to surrounding frame. The boundary elements of the specimen are similar, while the infill steel plate thickness is 0.9 mm. specimen consisted of the standard profile double section UNP100, as boundary elements. The specimens depth and width are equal to 400 mm. The specimen is subjected to quasi-static cyclic loading along the diagonal axes of specimen. Ultimate shear strength of system based on test results, 8.2 tons is obtained. Experimental result shows that using steel shear panel in the concentrically braced systems can improved hysteretic curve of system and it can dissipated a large amount of input energy in the nonlinear range. Finite element analysis of the laboratory specimen has been carried out. In the analysis, multi-linear kinematic hardening model is assigned to boundary element and infill plate. It is obtained that the used analytical method has been successful to estimate the actual shear capacity of the system and initial stiffness of system in comparison with the experimental results. It is found that the simulation outcomes have showed good agreement with the experimental results. Fundamental point in the designing of this kind of system is that buckling capacity of the system should be more than capacity of the steel shear panels to ensure that the panel is entered into the non-linear range without any buckling in the braced members. To achieve this goal, to design of the steel shear panel and braced members some equations have been proposed.
Sharif Journal of Civil Engineering
Sharif University of Technology
2676-4768
دوره 2-28
v.
4
no.
2012
147
154
https://sjce.journals.sharif.edu/article_693_23a3056df7975cc19d5336df09506f23.pdf