Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
HYDRO MECHANICAL EFFECT OF FOUNDATION ROCK MASS ON STABILITY OF CONCRETE GRAVITY DAMS
HYDRO MECHANICAL EFFECT OF FOUNDATION ROCK MASS ON STABILITY OF CONCRETE GRAVITY DAMS
3
12
625
FA
R.
Mahin Roosta
Faculty of Engineering & Technology \r\nTarbiat Mo&zwnj
M.
Hamidipour
Faculty of Engineering University of Zanjan
Journal Article
2009
10
27
One of the most important factors for the design and site selection of concrete gravity dams is the rock mass foundation. Concrete dam foundations are often rock masses with several discontinuities. The existence of discontinuities in rock mass, and their characteristics, such as aperture, roughness, stiffness, dip angle, spacing, geometric situation relative to dam body, and etc, cause rock mass to have complicated behavior. Furthermore, the hydro-mechanical interaction of jointed rock mass in the foundation of a dam increases its complexity. Also, uplift pressure under the dam body is an important factor in the design of such dams, whose distribution under the dam depends on the water head in the up and downstream of the dam and the joint set characteristics in the foundation. Another problem that hinders the stability of gravity dams is tension crack in the upstream and often in the heel of the dam. Accordingly, ignoring the role of discontinuities in design of dams may cause unrealistic forces on the dam and foundations, or may have adverse effects on the stability and efficiency of the dam. In this research, the stability of a typical 100 m height gravity dam on a jointed rock mass foundation, with two and three regular joint sets, was investigated using the distinct element code, UDEC. In order to provide an initial state in the model for controlling design requirements, dam construction and the first impoundment of the model were considered until the occurrence of steady state seepage flow in the whole dam and foundation system. Owing to the fact that both flow and equilibrium equations were active in all processes of simulations, hydro-mechanical behavior, with the effects of joint set characteristics, was considered. This process was repeated by changing the dip angle of the joint sets and results were compared with each other. All design requirements were controlled in each model and compared with traditional methods of designing gravity dams, in which the dam foundation was considered continuous. This evaluation consists of the overturning of the dam, sliding on the foundation surface, tension crack development at the base of the dam and the global stability of the dam and rock mass foundation. The results show that the number, dip and characteristics of joint sets are very effective parameters in different kinds of stability of gravity dams. On the one hand, the uplift pressure changes dramatically, due to changes in the joint set dip angles, and on the other hand, the pattern of instability in the whole system was controlled through the formation of a specific mechanism in the discontinuous rock foundation. In comparison with traditional methods of gravity dam design, it is noted that in the design of gravity dams on an abutment with continuous media, more caution should be taken into account regarding the discontinuous media.
One of the most important factors for the design and site selection of concrete gravity dams is the rock mass foundation. Concrete dam foundations are often rock masses with several discontinuities. The existence of discontinuities in rock mass, and their characteristics, such as aperture, roughness, stiffness, dip angle, spacing, geometric situation relative to dam body, and etc, cause rock mass to have complicated behavior. Furthermore, the hydro-mechanical interaction of jointed rock mass in the foundation of a dam increases its complexity. Also, uplift pressure under the dam body is an important factor in the design of such dams, whose distribution under the dam depends on the water head in the up and downstream of the dam and the joint set characteristics in the foundation. Another problem that hinders the stability of gravity dams is tension crack in the upstream and often in the heel of the dam. Accordingly, ignoring the role of discontinuities in design of dams may cause unrealistic forces on the dam and foundations, or may have adverse effects on the stability and efficiency of the dam. In this research, the stability of a typical 100 m height gravity dam on a jointed rock mass foundation, with two and three regular joint sets, was investigated using the distinct element code, UDEC. In order to provide an initial state in the model for controlling design requirements, dam construction and the first impoundment of the model were considered until the occurrence of steady state seepage flow in the whole dam and foundation system. Owing to the fact that both flow and equilibrium equations were active in all processes of simulations, hydro-mechanical behavior, with the effects of joint set characteristics, was considered. This process was repeated by changing the dip angle of the joint sets and results were compared with each other. All design requirements were controlled in each model and compared with traditional methods of designing gravity dams, in which the dam foundation was considered continuous. This evaluation consists of the overturning of the dam, sliding on the foundation surface, tension crack development at the base of the dam and the global stability of the dam and rock mass foundation. The results show that the number, dip and characteristics of joint sets are very effective parameters in different kinds of stability of gravity dams. On the one hand, the uplift pressure changes dramatically, due to changes in the joint set dip angles, and on the other hand, the pattern of instability in the whole system was controlled through the formation of a specific mechanism in the discontinuous rock foundation. In comparison with traditional methods of gravity dam design, it is noted that in the design of gravity dams on an abutment with continuous media, more caution should be taken into account regarding the discontinuous media.
https://sjce.journals.sharif.edu/article_625_233509073ed3432027d48b1a83f5fbd2.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
EVALUATION OF DAMAGE FUNCTIONS FOR NON-ENGINEERING BUILDINGS DURING THE 2005 DAHOOIYEH-ZARAND EARTHQUAKE IN IRAN
EVALUATION OF DAMAGE FUNCTIONS FOR NON-ENGINEERING BUILDINGS DURING THE 2005 DAHOOIYEH-ZARAND EARTHQUAKE IN IRAN
13
19
624
FA
M. R.
Ghayamghamian
International Institute of Earthquake Engine&
S.
Ahmadzadeh
Institute of Geophysics niversity of Tehran
N.
Mirzaei
Institute of Geophysics University of Tehran
Journal Article
2009
04
15
Several aspects of an earthquake, including those of a seismological, engineering, and socio-economical nature, must be understood and incorporated effectively before the impact of an earthquake can be predicted. Earthquake damage and loss modeling requires comprehensive assessment of earthquake hazard, the seismic vulnerability of the built environment and associated exposure. One of the steps in hazard mitigation and the realistic modeling of damage, fatalities and causality due to future earthquakes, is to apply appropriate damage and fatality functions. Among different methods for evaluating damage functions, the most robust method is the empirical method, which is based on the damage information of different building types from past earthquakes. The application of appropriate damage functions could provide an essential input for the seismic hazard mitigation plan before an earthquake, as well as preparedness and response plans after an earthquake. Damage functions vary for each region or country, based on the types of structure, materials and construction methods. Therefore, the damage data from a past earthquake should be carefully gathered and analyzed. Then, the ground motion level, in the form of seismic intensity, peak ground acceleration or velocity, needs to be estimated in damaged areas and their relation to the observed damage of structures should be investigated. To this end, the recent earthquakes in Iran provide a unique opportunity to develop damage functions, and to study their relations with different levels of damage experienced by different types of structure. In this paper, the empirical damage functions for non-engineering buildings (adobe and masonry structures) were evaluated in terms of intensity and peak ground acceleration for the Zarand region. The building damage data were collected from the damage survey of the 2005 Dahooiyeh-Zarand earthquake, by the first author, and those gathered from the damage report provided by different organizations. The earthquake intensity was evaluated in the damaged areas considering the vulnerability class and the damage grade of buildings using the European Macroseismic Scale (EMS-98). Furthermore, peak ground acceleration was estimated from the recorded data and by application of an interpolation technique to those estimated by attenuation relationships in damaged areas, where no recorded data were available. Then, the damage functions for a heavy damage level (G4+G5) were evaluated for adobe and masonry structures, which were the major types of structure in the Zarand egion. The introduced damage functions revealed that the heavy damage threshold for non-engineering buildings in the Zarand region is about 100 cm/s$^2$ or VII on the EMS-98 intensity scale.
Several aspects of an earthquake, including those of a seismological, engineering, and socio-economical nature, must be understood and incorporated effectively before the impact of an earthquake can be predicted. Earthquake damage and loss modeling requires comprehensive assessment of earthquake hazard, the seismic vulnerability of the built environment and associated exposure. One of the steps in hazard mitigation and the realistic modeling of damage, fatalities and causality due to future earthquakes, is to apply appropriate damage and fatality functions. Among different methods for evaluating damage functions, the most robust method is the empirical method, which is based on the damage information of different building types from past earthquakes. The application of appropriate damage functions could provide an essential input for the seismic hazard mitigation plan before an earthquake, as well as preparedness and response plans after an earthquake. Damage functions vary for each region or country, based on the types of structure, materials and construction methods. Therefore, the damage data from a past earthquake should be carefully gathered and analyzed. Then, the ground motion level, in the form of seismic intensity, peak ground acceleration or velocity, needs to be estimated in damaged areas and their relation to the observed damage of structures should be investigated. To this end, the recent earthquakes in Iran provide a unique opportunity to develop damage functions, and to study their relations with different levels of damage experienced by different types of structure. In this paper, the empirical damage functions for non-engineering buildings (adobe and masonry structures) were evaluated in terms of intensity and peak ground acceleration for the Zarand region. The building damage data were collected from the damage survey of the 2005 Dahooiyeh-Zarand earthquake, by the first author, and those gathered from the damage report provided by different organizations. The earthquake intensity was evaluated in the damaged areas considering the vulnerability class and the damage grade of buildings using the European Macroseismic Scale (EMS-98). Furthermore, peak ground acceleration was estimated from the recorded data and by application of an interpolation technique to those estimated by attenuation relationships in damaged areas, where no recorded data were available. Then, the damage functions for a heavy damage level (G4+G5) were evaluated for adobe and masonry structures, which were the major types of structure in the Zarand egion. The introduced damage functions revealed that the heavy damage threshold for non-engineering buildings in the Zarand region is about 100 cm/s$^2$ or VII on the EMS-98 intensity scale.
https://sjce.journals.sharif.edu/article_624_48ab2f9b45957ab574cf005eb8a76760.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
ROUGHNESS EFFECT ON VELOCITY DOMAIN THROUGH ROCK FRACTURES
ROUGHNESS EFFECT ON VELOCITY DOMAIN THROUGH ROCK FRACTURES
21
28
626
FA
M.
Javadi
Dept. of Mining & Metallurgical Engineering\r\nAmi&zwnj
M.
Sharifzadeh
Dept. of Mining & Metallurgical Engineering Ami
K.
Shahriar
Dept. of Mining & Metallurgical Engineering \r\nAmi&
M.
Mehrjooe
Dept. of Mechanical Engineering Amirkabir Univ&zwnj
Journal Article
2009
02
17
Fluid flow and solute transport in a fractured rock mass are of key interest for many practical applications, such as in the hydrocarbon and water industries and in the safe design of disposal sites for domestic, industrial and nuclear waste. In many geological structures, rock fractures are the main flow paths and are a most important attribute in rock mass hydraulic behavior. Therefore, the development of realistic and robust predictive models of flow and transport requires a thorough understanding of the physical processes that govern flow in individual fractures. The objective of this paper is to examine the impacts of fracture roughness on the flow velocity field throughout an individual fracture. First, a three-dimensional geometrical domain of an arbitrary rough-walled fracture, consisting of 150 volumetric elements (fracture segments) in 6 rows and 25 columns, was generated. The computational domain of this fracture was generated, and turbulent flow through the void specimen was simulated by using the finite volume method for a wide range of inlet velocities; from 0.01 to 1 m/s. In order to evaluate the effect of surface roughness and aperture on the average flow velocity, sixty-four horizontal sections, with 0.01mm consecutive distances in a z-direction and eleven vertical sections, normal to the y-direction and perpendicular to the main flow direction, with 1 mm consecutive distances in the y-direction, were considered through the geometrical domain, respectively. The average velocity on these horizontal and vertical sections has been normalized with the inlet velocity. These normalized velocities were used to illustrate roughness and aperture effects on flow velocity fields in rock fractures. The maximum value of the normalized velocity on horizontal sections is about 1.47, occurred in the inlet velocity of 0.01 m/s, which is close to the ideal magnitude for cubic law. By increasing inlet velocity, the maximum value of the normalized velocity on horizontal sections decreases from 1.47 to 1.34 for the inlet velocity of 0.01 m/s to 1 m/s, respectively. Moreover, by increasing inlet velocity, the corresponding height of the maximum value of the normalized velocity decreases from 0.205 mm to 0.18 mm for the inlet velocity of 0.01 m /s to 1 m/s, respectively. The results show that; (i) by increasing flow rate, the symmetry of the velocity profile decreases and inclines to the smoothest fracture surface, and, also, the intensity of the rotational flow increases, (ii) in high flow rates, the arrangement of flow channels changes and lower flow rates take place through large apertures.
Fluid flow and solute transport in a fractured rock mass are of key interest for many practical applications, such as in the hydrocarbon and water industries and in the safe design of disposal sites for domestic, industrial and nuclear waste. In many geological structures, rock fractures are the main flow paths and are a most important attribute in rock mass hydraulic behavior. Therefore, the development of realistic and robust predictive models of flow and transport requires a thorough understanding of the physical processes that govern flow in individual fractures. The objective of this paper is to examine the impacts of fracture roughness on the flow velocity field throughout an individual fracture. First, a three-dimensional geometrical domain of an arbitrary rough-walled fracture, consisting of 150 volumetric elements (fracture segments) in 6 rows and 25 columns, was generated. The computational domain of this fracture was generated, and turbulent flow through the void specimen was simulated by using the finite volume method for a wide range of inlet velocities; from 0.01 to 1 m/s. In order to evaluate the effect of surface roughness and aperture on the average flow velocity, sixty-four horizontal sections, with 0.01mm consecutive distances in a z-direction and eleven vertical sections, normal to the y-direction and perpendicular to the main flow direction, with 1 mm consecutive distances in the y-direction, were considered through the geometrical domain, respectively. The average velocity on these horizontal and vertical sections has been normalized with the inlet velocity. These normalized velocities were used to illustrate roughness and aperture effects on flow velocity fields in rock fractures. The maximum value of the normalized velocity on horizontal sections is about 1.47, occurred in the inlet velocity of 0.01 m/s, which is close to the ideal magnitude for cubic law. By increasing inlet velocity, the maximum value of the normalized velocity on horizontal sections decreases from 1.47 to 1.34 for the inlet velocity of 0.01 m/s to 1 m/s, respectively. Moreover, by increasing inlet velocity, the corresponding height of the maximum value of the normalized velocity decreases from 0.205 mm to 0.18 mm for the inlet velocity of 0.01 m /s to 1 m/s, respectively. The results show that; (i) by increasing flow rate, the symmetry of the velocity profile decreases and inclines to the smoothest fracture surface, and, also, the intensity of the rotational flow increases, (ii) in high flow rates, the arrangement of flow channels changes and lower flow rates take place through large apertures.
https://sjce.journals.sharif.edu/article_626_45645a27c4f1adc8a7a835976064a86d.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
A FIBER ELEMENT MODEL FOR SEISMIC EVALUATION OF OLD R.C. BUILDINGS
A FIBER ELEMENT MODEL FOR SEISMIC EVALUATION OF OLD R.C. BUILDINGS
29
40
627
FA
A.
Dabiri
Dept. of Civil Engineering K.N.Toosi University of Te&zwn
M.
Zeinoddini
Dept. of Civil Engineering K.N.Toosi University of Te&zwn
J.
Keyvani
Faculty of Engineering \r\nKharazmi University
Journal Article
2009
06
13
The structural safety of existing constructions is one of the key issues of modern earthquake and structural engineering. Many existing old concrete buildings are designed according to obsolete seismic codes or even without any specific seismic provisions. Before the 1970s, when deformed bars found a wider application, plain rebars were extensively used in RC structures. Currently, there is no generally accepted practice for the seismic evaluation of RC buildings with plain reinforcements. The stiffness, strength, ductility and energy dissipation behavior of RC members with plain reinforcements are significantly influenced by the bond-slip. The current study deals with the seismic behavior of RC buildings reinforced with plain rebars. In this study, a tailored fiber element model has been proposed, which can be used for evaluating the seismic performance of RC structures reinforced with plain rebars. The slipping characteristics of the plain rebar have been calculated using a semi-analytical approximation and incorporated in this model. To this aim, an altered stress-strain property has been assigned to the steel fibers in tension. To evaluate the seismic performance of RC buildings reinforced with plain rebars, the cross section of the structural members needs to then be modeled by fiber elements and the new but softer stress-strain onstitutive model should be introduced to the steel fibers. The bond-slip behavior is included into two end segments in all beam-column RC members. The length of the end segments, or the strain penetration length, has been considered to be proportional to the plastic hinge length at two ends of each RC member. The ratio between the strain penetration and plastic hinge lengths has been obtained from calibrating the proposed model against experimental data. For cyclic loadings, the energy degradation factor (for steel fibers with bond-slip effects) has also been defined through the calibration of the proposed fiber element model against experimental data. The calibrated model has then been validated against other sets of experimental results from other researchers, who carried out monotonic and cyclic tests on RC members with plain rebars. In general, a reasonable level of agreement has been perceived between the numerical and experimental results, under both monotonic and cyclic loading conditions. As a practical case study, the model proposed has been implemented for the seismic evaluation of an important historical existing RC building with plain reinforcements. Two dimensional frames from this old reinforced building with plain rebars have then been studied. Both non-linear static and dynamic types of earthquake excitation have been considered. The model proposed has been found to well present a degraded performance for the reinforcements, in comparison with a corresponding structure with deformed reinforcements. It has also been noticed that the simple approach proposed by FEMA273, for the seismic modeling of RC buildings with plain reinforcements, yields considerably conservative predictions for the seismic performance of the structure studied.
The structural safety of existing constructions is one of the key issues of modern earthquake and structural engineering. Many existing old concrete buildings are designed according to obsolete seismic codes or even without any specific seismic provisions. Before the 1970s, when deformed bars found a wider application, plain rebars were extensively used in RC structures. Currently, there is no generally accepted practice for the seismic evaluation of RC buildings with plain reinforcements. The stiffness, strength, ductility and energy dissipation behavior of RC members with plain reinforcements are significantly influenced by the bond-slip. The current study deals with the seismic behavior of RC buildings reinforced with plain rebars. In this study, a tailored fiber element model has been proposed, which can be used for evaluating the seismic performance of RC structures reinforced with plain rebars. The slipping characteristics of the plain rebar have been calculated using a semi-analytical approximation and incorporated in this model. To this aim, an altered stress-strain property has been assigned to the steel fibers in tension. To evaluate the seismic performance of RC buildings reinforced with plain rebars, the cross section of the structural members needs to then be modeled by fiber elements and the new but softer stress-strain onstitutive model should be introduced to the steel fibers. The bond-slip behavior is included into two end segments in all beam-column RC members. The length of the end segments, or the strain penetration length, has been considered to be proportional to the plastic hinge length at two ends of each RC member. The ratio between the strain penetration and plastic hinge lengths has been obtained from calibrating the proposed model against experimental data. For cyclic loadings, the energy degradation factor (for steel fibers with bond-slip effects) has also been defined through the calibration of the proposed fiber element model against experimental data. The calibrated model has then been validated against other sets of experimental results from other researchers, who carried out monotonic and cyclic tests on RC members with plain rebars. In general, a reasonable level of agreement has been perceived between the numerical and experimental results, under both monotonic and cyclic loading conditions. As a practical case study, the model proposed has been implemented for the seismic evaluation of an important historical existing RC building with plain reinforcements. Two dimensional frames from this old reinforced building with plain rebars have then been studied. Both non-linear static and dynamic types of earthquake excitation have been considered. The model proposed has been found to well present a degraded performance for the reinforcements, in comparison with a corresponding structure with deformed reinforcements. It has also been noticed that the simple approach proposed by FEMA273, for the seismic modeling of RC buildings with plain reinforcements, yields considerably conservative predictions for the seismic performance of the structure studied.
https://sjce.journals.sharif.edu/article_627_185c29dc24325934ee377cfda20e414c.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
MODELLING OF PRESSUREMETER TESTS WITH ARTIFICIAL NEURAL NETWORKS
MODELLING OF PRESSUREMETER TESTS WITH ARTIFICIAL NEURAL NETWORKS
41
54
628
FA
M.
Emami
Faculty of Engineering \r\nTarbiat Modares Univer&
S. S.
Yasrobi
Faculty of Engineering\r\nTarbiat Modares Univer&zwnj
Journal Article
2009
04
08
In this paper, three types of Artificial Neural Network (ANN) are employed to interpret pressuremeter test results. First, a multi layer perceptron neural network, one of the most applicable neural networks, is used. Then, a neuro-fuzzy network, a combination of neural-fuzzy networks, is employed and, finally, a radial basis function, successful in solving nonlinear problems, is applied. Of all neural network models, the multi layer perceptron neural network proved to be the most effective. Finally, different models have been compared and the network with the most outstanding performance in two stages is determined. For the purpose of assessment, the capability of the model generalization, and the performance of the mentioned network against inexperienced data has been compared with empirical results. Contrary to conventional behavioral models, models based on neural networks are unable to demonstrate the effect of input parameters on output parameters. This research is a response to this need, through conducting a sensitivity analysis on the optimal structure of proposed models. Also, derivation of a governing equation for the neural network model gives more assurance to the user to employ such models, and, consequently, facilitates the application of models in engineering practices.
In this paper, three types of Artificial Neural Network (ANN) are employed to interpret pressuremeter test results. First, a multi layer perceptron neural network, one of the most applicable neural networks, is used. Then, a neuro-fuzzy network, a combination of neural-fuzzy networks, is employed and, finally, a radial basis function, successful in solving nonlinear problems, is applied. Of all neural network models, the multi layer perceptron neural network proved to be the most effective. Finally, different models have been compared and the network with the most outstanding performance in two stages is determined. For the purpose of assessment, the capability of the model generalization, and the performance of the mentioned network against inexperienced data has been compared with empirical results. Contrary to conventional behavioral models, models based on neural networks are unable to demonstrate the effect of input parameters on output parameters. This research is a response to this need, through conducting a sensitivity analysis on the optimal structure of proposed models. Also, derivation of a governing equation for the neural network model gives more assurance to the user to employ such models, and, consequently, facilitates the application of models in engineering practices.
https://sjce.journals.sharif.edu/article_628_42e77b63637ab381e8be5f8318cc28a2.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
TENSION STIFFENING OF CONCRETE MEMBERS STRENGTHENED WITH\r\nFIBER-REINFORCED POLYMER (FRP) SHEETS
TENSION STIFFENING OF CONCRETE MEMBERS STRENGTHENED WITH\r\nFIBER-REINFORCED POLYMER (FRP) SHEETS
55
64
629
FA
S.M.
Pirayesh
Dept. of Civil Engineering Ferdowsi University o&z
M.R.
Esfahani
Dept. of Civil Engineering Ferdowsi University o&zw
0000-0002-2655-2466
Journal Article
2009
06
29
Concrete behavior in structural members is considerably affected by cracking due to tensile loads. The initiation of cracks is influenced by the properties of concrete under tensile stresses. The development of cracks plays a significant role in the nonlinear analysis of concrete structures. The cracking process in tension starts at a relatively low tensile strain, causing plain concrete to exhibit a gradual softening behavior. This softening behavior is magnified by the tension stiffening phenomenon in reinforced or strengthened concrete members. Very few studies can be found concerning the behavior of FRP (Fiber Reinforced Polymers)-strengthened reinforced concrete (RC) elements. Tension stiffening is an effective parameter in the behavior of externally bonded FRP sheets in tension. This parameter influences the crack width, spacing between cracks and the stiffness of the tensile members. In order to study the effect of tension stiffening of the FRP sheets, 16 concrete specimens were manufactured and tested. Each concrete specimen included 2 concrete prisms bonded together with adhesive, and 2 or 4 layers of either CFRP (Carbon Fiber Reinforced Polymers) or GFRP (Glass Fiber Reinforced Polymers) sheets. The dimensions of each concrete prism were 500$times$ 80 $times$ 40 mm. Two concrete mixtures with the compressive strengths of 25 MPa and 40 MPa were used for different specimens. The specimens were tested under tension through the application of tensile force on the FRP sheet ends. The stress-strain relationships of different specimens were compared with each other in order to evaluate the effect of tension stiffening of the strengthened members. The ratios of the effective modulus of elasticity of the strengthened concrete members, E$_{eff}$, over the modulus of elasticity of FRP sheets, $E_{frp}$ , were measured. Based on the test results, reduction of the FRP ratio in sections increased the effect of the tension stiffening of the members. The ratio of E$_{eff./}$E$_{frp}$ in the case of the GFRP sheet was larger than that of the CFRP sheet compared to the CFRP sheets. Also, the increase of concrete strength from 25 to 40 MPa increased the tension stiffening effect.
Concrete behavior in structural members is considerably affected by cracking due to tensile loads. The initiation of cracks is influenced by the properties of concrete under tensile stresses. The development of cracks plays a significant role in the nonlinear analysis of concrete structures. The cracking process in tension starts at a relatively low tensile strain, causing plain concrete to exhibit a gradual softening behavior. This softening behavior is magnified by the tension stiffening phenomenon in reinforced or strengthened concrete members. Very few studies can be found concerning the behavior of FRP (Fiber Reinforced Polymers)-strengthened reinforced concrete (RC) elements. Tension stiffening is an effective parameter in the behavior of externally bonded FRP sheets in tension. This parameter influences the crack width, spacing between cracks and the stiffness of the tensile members. In order to study the effect of tension stiffening of the FRP sheets, 16 concrete specimens were manufactured and tested. Each concrete specimen included 2 concrete prisms bonded together with adhesive, and 2 or 4 layers of either CFRP (Carbon Fiber Reinforced Polymers) or GFRP (Glass Fiber Reinforced Polymers) sheets. The dimensions of each concrete prism were 500$times$ 80 $times$ 40 mm. Two concrete mixtures with the compressive strengths of 25 MPa and 40 MPa were used for different specimens. The specimens were tested under tension through the application of tensile force on the FRP sheet ends. The stress-strain relationships of different specimens were compared with each other in order to evaluate the effect of tension stiffening of the strengthened members. The ratios of the effective modulus of elasticity of the strengthened concrete members, E$_{eff}$, over the modulus of elasticity of FRP sheets, $E_{frp}$ , were measured. Based on the test results, reduction of the FRP ratio in sections increased the effect of the tension stiffening of the members. The ratio of E$_{eff./}$E$_{frp}$ in the case of the GFRP sheet was larger than that of the CFRP sheet compared to the CFRP sheets. Also, the increase of concrete strength from 25 to 40 MPa increased the tension stiffening effect.
https://sjce.journals.sharif.edu/article_629_051e4e127b92f5d98d3c79b195f2b291.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
NEW METHOD FOR GENERATION OF ARTIFICIAL EARTHQUAKE ACCELEROGRAMS USING WAVELET PACKET TRANSFORM AND GENERALIZED REGRESSION NEURAL
NEW METHOD FOR GENERATION OF ARTIFICIAL EARTHQUAKE ACCELEROGRAMS USING WAVELET PACKET TRANSFORM AND GENERALIZED REGRESSION NEURAL
65
74
630
FA
G.
G.Amiri
Dept. of Civil Engineering\r\nIran University of Scie
0000-0003-3244-0943
A.
Asadi
Dept. of Civil Engineering,\r\nYazd University
A.
Bagheri
Dept. of Civil and Environmental Engineering\r\nUni&z
Journal Article
2009
07
18
For earthquake resistant design of critical structures, a dynamic analysis, either response spectrum or time history, is frequently required. Owing to the lack of recorded data and the randomness of earthquake ground motion that may be experienced by structures in the future, it is usually difficult to obtain recorded data that fit the requirements well. Therefore, artificial seismic waves are widely used in seismic design, in verification of seismic capacity and in the seismic assessment of structures. The purpose of this paper is to develop a numerical method using generalized regression neural networks and the wavelet packet in the best basis method, which is presented for the computation of artificial earthquake records consistent with any arbitrarily specified target response spectra requirement. Earthquake ground motion has been modeled as a non-stationary process using a wavelet packet. In this study, a new neural-network-based methodology, with a wavelet packet best-basis transform, for the generation of artificial accelerograms from the pseudo-velocity response spectra, has been proposed. The wavelet packets can be used for numerous xpansions of a given signal. The most suitable decomposition of a given signal, with respect to an entropy-based criterion, was selected. A single wavelet packet decomposition gives many bases, from which one can look for the best representation, with respect to a design objective. It can be done by using an entropy-based criterion to select the most suitable decomposition of a given signal. The best basis algorithm, described by Wickerhauser, uses a minimum entropy criterion and gives the most concise description for a signal for the dictionary in hand. This can be done by finding the best tree based on an entropy criterion. The best basis search algorithm uses wavelet packets in this approach; the signal is expressed as a linear combination of time-frequency atoms. The atoms are obtained by dilations of the analyzing functions, and are organized into dictionaries as wavelet packets. This method shows, by computation of the best-tree for given entropy, that the optimal wavelet packet tree is computed to balance the amount of compression and retained energy. By using this method, the results can be optimized. The presented method also uses the learning capabilities of neural networks to develop the nowledge of inverse mapping from response spectra to earthquake accelerogram. In the proposed method, the neural networks learn the inverse mapping directly from the actual recorded earthquake accelerograms and their response spectra. The proposed method is validated using Iranian earthquake accelerograms to train the neural networks. The trained neural network was tested with the earthquake accelerograms from both the training set and the novel cases from the test set. The generated accelerogram is plausible, with similar characteristics to those in the training set, and its response spectrum is very close to the input design spectrum. This is a useful property of the neural network based methodology; it will enable the generation of accelerograms compatible with any specified design spectra. The generated accelerogram is plausible, with similar characteristics to those in the training set, and its response spectrum is very close to the input design spectrum. This is a useful property of the neural network based methodology; it will enable the generation of accelerograms compatible with any specified design spectra. The generated accelerograms can then be used in time history analysis of linear and nonlinear structures. Finally, with the proposed method, an artificial earthquake accelerogram, compatible with a single design spectrum, is generated. This study shows that the procedure, using the neural network-based model and wavelet packets in a best-basis method, is applicable for generating artificial earthquakes compatible with any response spectra.
For earthquake resistant design of critical structures, a dynamic analysis, either response spectrum or time history, is frequently required. Owing to the lack of recorded data and the randomness of earthquake ground motion that may be experienced by structures in the future, it is usually difficult to obtain recorded data that fit the requirements well. Therefore, artificial seismic waves are widely used in seismic design, in verification of seismic capacity and in the seismic assessment of structures. The purpose of this paper is to develop a numerical method using generalized regression neural networks and the wavelet packet in the best basis method, which is presented for the computation of artificial earthquake records consistent with any arbitrarily specified target response spectra requirement. Earthquake ground motion has been modeled as a non-stationary process using a wavelet packet. In this study, a new neural-network-based methodology, with a wavelet packet best-basis transform, for the generation of artificial accelerograms from the pseudo-velocity response spectra, has been proposed. The wavelet packets can be used for numerous xpansions of a given signal. The most suitable decomposition of a given signal, with respect to an entropy-based criterion, was selected. A single wavelet packet decomposition gives many bases, from which one can look for the best representation, with respect to a design objective. It can be done by using an entropy-based criterion to select the most suitable decomposition of a given signal. The best basis algorithm, described by Wickerhauser, uses a minimum entropy criterion and gives the most concise description for a signal for the dictionary in hand. This can be done by finding the best tree based on an entropy criterion. The best basis search algorithm uses wavelet packets in this approach; the signal is expressed as a linear combination of time-frequency atoms. The atoms are obtained by dilations of the analyzing functions, and are organized into dictionaries as wavelet packets. This method shows, by computation of the best-tree for given entropy, that the optimal wavelet packet tree is computed to balance the amount of compression and retained energy. By using this method, the results can be optimized. The presented method also uses the learning capabilities of neural networks to develop the nowledge of inverse mapping from response spectra to earthquake accelerogram. In the proposed method, the neural networks learn the inverse mapping directly from the actual recorded earthquake accelerograms and their response spectra. The proposed method is validated using Iranian earthquake accelerograms to train the neural networks. The trained neural network was tested with the earthquake accelerograms from both the training set and the novel cases from the test set. The generated accelerogram is plausible, with similar characteristics to those in the training set, and its response spectrum is very close to the input design spectrum. This is a useful property of the neural network based methodology; it will enable the generation of accelerograms compatible with any specified design spectra. The generated accelerogram is plausible, with similar characteristics to those in the training set, and its response spectrum is very close to the input design spectrum. This is a useful property of the neural network based methodology; it will enable the generation of accelerograms compatible with any specified design spectra. The generated accelerograms can then be used in time history analysis of linear and nonlinear structures. Finally, with the proposed method, an artificial earthquake accelerogram, compatible with a single design spectrum, is generated. This study shows that the procedure, using the neural network-based model and wavelet packets in a best-basis method, is applicable for generating artificial earthquakes compatible with any response spectra.
https://sjce.journals.sharif.edu/article_630_9cc138f8dc04cbf16240daa92d8d50e2.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
INVESTIGATION OF HETEROGENEITY IN NATURAL DEPOSITS USING THE RANDOM FIELD THEORY
INVESTIGATION OF HETEROGENEITY IN NATURAL DEPOSITS USING THE RANDOM FIELD THEORY
75
83
631
FA
R.
J. Chenari
Dept. of Civil Engineering \r\nUniversity of Guilan
R.
O. Dodaran
Dept. of Civil Engineering University of Guilan
Journal Article
2009
07
27
One of the main distinctions between geomaterials and other engineering materials is the spatial variation of their properties in different directions inside them. This characteristic of geomaterials, called heterogeneity, is studied herewith. Almost all natural soils are highly variable in their properties and rarely homogeneous. Soil heterogeneity can be classified into two main categories. The first is lithological heterogeneity, which can be manifested in the form of thin soft/stiff layers embedded in a stiffer/softer media, or the inclusion of pockets of different lithology within a more uniform soil mass. The second source of heterogeneity can be attributed to inherent spatial soil variability, which is the variation of soil properties from one point to another in space. Inherent spatial variability of geomaterials is itself divided into a random component, which is attributed to different depositional conditions, and the deterministic trends, which are attributed to the variations in soil properties, such as the increase in soil strength and stiffness with depth, due to the increase in confining pressure. Different elements of soil inherent spatial variability, such as mean, variance, and spatial correlation characteristics, are introduced. The settlement calculation for shallow foundations is based mainly on input stiffness parameters, which are used in an average sense in classic and traditional methods. Spatial variability, which is inherent to geomaterials, is not considered in conventional settlement prediction schemes for shallow foundations. This study focuses on the heterogeneity of a soil deformation modulus. Inherent variability, as the major source of heterogeneity, was modeled as a Gaussian stochastic field in a horizontal direction. In a vertical direction, a deterministic trend was invoked by assuming that the coefficient of variation (COV) remains constant, while the average follows a trend. It is found that for the deformation modulus, a transformation depth exists where its depth-varying trend changes direction. An empirical formula for the transformation depth of the deformation modulus is introduced. Realizations are produced, with the aid of the Local Average Subdivisions (LAS) theory, relying on in-situ test results and the proposed trend for the elastic modulus, leading to the conclusion that the random field theory is a powerful tool for modeling the heterogeneity embedded in soil materials. The random field theory can finally be adopted, in combination with the finite element theory, in order to model different problems.
One of the main distinctions between geomaterials and other engineering materials is the spatial variation of their properties in different directions inside them. This characteristic of geomaterials, called heterogeneity, is studied herewith. Almost all natural soils are highly variable in their properties and rarely homogeneous. Soil heterogeneity can be classified into two main categories. The first is lithological heterogeneity, which can be manifested in the form of thin soft/stiff layers embedded in a stiffer/softer media, or the inclusion of pockets of different lithology within a more uniform soil mass. The second source of heterogeneity can be attributed to inherent spatial soil variability, which is the variation of soil properties from one point to another in space. Inherent spatial variability of geomaterials is itself divided into a random component, which is attributed to different depositional conditions, and the deterministic trends, which are attributed to the variations in soil properties, such as the increase in soil strength and stiffness with depth, due to the increase in confining pressure. Different elements of soil inherent spatial variability, such as mean, variance, and spatial correlation characteristics, are introduced. The settlement calculation for shallow foundations is based mainly on input stiffness parameters, which are used in an average sense in classic and traditional methods. Spatial variability, which is inherent to geomaterials, is not considered in conventional settlement prediction schemes for shallow foundations. This study focuses on the heterogeneity of a soil deformation modulus. Inherent variability, as the major source of heterogeneity, was modeled as a Gaussian stochastic field in a horizontal direction. In a vertical direction, a deterministic trend was invoked by assuming that the coefficient of variation (COV) remains constant, while the average follows a trend. It is found that for the deformation modulus, a transformation depth exists where its depth-varying trend changes direction. An empirical formula for the transformation depth of the deformation modulus is introduced. Realizations are produced, with the aid of the Local Average Subdivisions (LAS) theory, relying on in-situ test results and the proposed trend for the elastic modulus, leading to the conclusion that the random field theory is a powerful tool for modeling the heterogeneity embedded in soil materials. The random field theory can finally be adopted, in combination with the finite element theory, in order to model different problems.
https://sjce.journals.sharif.edu/article_631_b7bb35b9c6ca2aee2df08cf09d7016c2.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
DISCHARGE COEFFICIENT OF LABYRINTH SIDE WEIRS USING ARTIFICIAL NEURAL NETWORK METHOD BASED ON EXPERIMENTAL DATA
DISCHARGE COEFFICIENT OF LABYRINTH SIDE WEIRS USING ARTIFICIAL NEURAL NETWORK METHOD BASED ON EXPERIMENTAL DATA
85
92
632
FA
A.R.
Kabiri-Samani
Dept. of Civil Engineering Isfahan University of Te
S.R.
Hejazi
Dept. of Industrial and Systems Engineering\r\nIsfah
M.
Aghajan
Dept. of Civil Engineering Isfahan University of T
H.
Esmaili
Dept. of Civil Engineering Isfahan University of T&
Journal Article
2009
08
29
Side weirs are flow-regulating devices commonly encountered in hydraulic engineering. A side weir is an over flow weir framed at the side of a channel, over which lateral outflow takes place when the water surface in the channel rises above the weir crest. They are widely used for flow diversions in irrigation, land drainage, urban sewage systems and also in intake structures. It is essential for hydraulic engineers to correctly predict the weir discharge coefficient, regarding the technical and economical design of side weirs. Although the discharge coefficient for flow over a side weir has been investigated experimentally by many investigators, an overall acceptable formula or a complete analytical solution of the equation governing the flow does not exist. Although sharp crested rectangular side weirs have been extensively studied, there is a lack of information on the other shapes of side weirs, such as labyrinth weirs. In this study the hydraulic characteristics of flow over labyrinth sharp crested side weirs are adapted to formulate the discharge coefficient, based on experimental data and the artificial neural network method. The discharge coefficient (C$_M$) is then related to the main channel upstream; Froude Number (Fr$_1$), weir height to upsteam flow depth ratio (w/y$_1$), weir crest length to channel width ratio (L/B) and the labyrinth weir angle ($delta$). The main objective of this study is to determine C$_M$, based on experimental data, by employing linear and nonlinear regressions and artificial neural network (ANN) approaches. The results have been compared with source data. Comparison of results shows that the ANN method is a good tool for determination of the labyrinth sharp crested side weir discharge cofficient.
Side weirs are flow-regulating devices commonly encountered in hydraulic engineering. A side weir is an over flow weir framed at the side of a channel, over which lateral outflow takes place when the water surface in the channel rises above the weir crest. They are widely used for flow diversions in irrigation, land drainage, urban sewage systems and also in intake structures. It is essential for hydraulic engineers to correctly predict the weir discharge coefficient, regarding the technical and economical design of side weirs. Although the discharge coefficient for flow over a side weir has been investigated experimentally by many investigators, an overall acceptable formula or a complete analytical solution of the equation governing the flow does not exist. Although sharp crested rectangular side weirs have been extensively studied, there is a lack of information on the other shapes of side weirs, such as labyrinth weirs. In this study the hydraulic characteristics of flow over labyrinth sharp crested side weirs are adapted to formulate the discharge coefficient, based on experimental data and the artificial neural network method. The discharge coefficient (C$_M$) is then related to the main channel upstream; Froude Number (Fr$_1$), weir height to upsteam flow depth ratio (w/y$_1$), weir crest length to channel width ratio (L/B) and the labyrinth weir angle ($delta$). The main objective of this study is to determine C$_M$, based on experimental data, by employing linear and nonlinear regressions and artificial neural network (ANN) approaches. The results have been compared with source data. Comparison of results shows that the ANN method is a good tool for determination of the labyrinth sharp crested side weir discharge cofficient.
https://sjce.journals.sharif.edu/article_632_abd815286ba1007abfbb8415b83ae2cf.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
STUDY OF THE BEHAVIOUR OF SOIL AROUND PILE GROUPS UNDER LATERAL LOAD IN\r\nSAND
STUDY OF THE BEHAVIOUR OF SOIL AROUND PILE GROUPS UNDER LATERAL LOAD IN\r\nSAND
93
101
633
FA
M.
Hajialilue-Bonab
Dept. of Civil Engineering\r\nUniversity of Tabriz
H.
Azarnya-Shahgoli
Dept. of Civil Engineering\r\nUniversity of Tabriz
M. H.
Mohassel
Dept. of Civil Engineering\r\n University of Tabriz
Journal Article
2009
09
22
Many buildings and structures require the use of deep foundations to utilize the bearing capacity of stronger soil layers. Pile groups are one particular type of deep foundation commonly used for large structures. In addition to vertical loads that must be sustained by the piles, significant lateral loads may be present and must be accounted for in the design. These lateral loads can come from a variety of sources, such as wind forces, collisions, wave or ice impact, earthquake shaking, liquefaction and slope failure. A pile group subjected to lateral loading is nfluenced by the existence of neighboring piles. This pile-soil-pile interaction is strongly dependent on the pile-to-pile spacing, which dominates the pattern of stress and deformation around a pile group. Full-scale tests are generally believed to provide the most accurate results, but are rare due to high costs. Therefore, many studies are available concerning centrifuge and model testing. In this paper, the behaviour of soil around laterally loaded pile groups in sand for different cases were studied and interpreted in the laboratory on small scale physical models, using the Particle Image Velocimetry (PIV) method. The group effect and interaction between piles in a pile group were also studied. A wooden box was used as the test box. A transparent sheet was used in place of a fourth wooden wall. Plexiglass was used to allow observation of the deformations in the soil sample. The soil was fine, dry sand. The soil was placed in the box using a sand raining system, in order to obtain a uniform and homogeneous medium. Rectangular piles were selected, in order to apply the similitude law. The smallest dimensions of piles were in contact with the Plexiglass. The 2$times$ 1 pile group model, with different pile spacing, was used in the direction of the load. An aluminous cap was used to connect two pile heads. Each pile was joined by a hinge (free rotation) to the cap. An electromotor with uniform velocity was used to apply lateral load statically to the pile group cap. A LVDT displacement sensor and a sensitive load cell were installed in order to record the pile head displacement and applied force. A digital camera was used for visualization of the soil movements and for image processing. The tests were performed by varying the pile centre-to-centre spacing from 1 to 6 times the pile widths (B). One test was performed on a laterally loaded single pile. Soil displacement vectors, soil shear strain and the soil displacement field around a laterally loaded single pile and pile groups, were obtained by image processing using the PIV method. Also, the load --- deflection curve for pile heads was obtained. It is found that, although a pile-group strengthens overall lateral load resistance it can weaken the individual pile response of the piles in the group. The overall lateral load is divided among each of the piles in the group. Each pile pushes against the soil behind it, creating a shear zone in the soil. These shear zones begin to enlarge and overlap as the lateral load increases. More overlapping occurs if the piles are spaced very closely together. In the case of 1B space between piles, the soil between the two piles has very low resistance against the horizontal displacement of the trail pile. In the case of 6B space between piles, the displacements of soil around each pile have no overlaps. It can be concluded that the interaction between piles decreases with increasing pile space. Also, in the case of 1B space between piles, strain wedges are overlapped, which shows the interaction of two piles. In this case, the created strain wedge is very similar to a single pile with larger width. This means that when two piles are very close to each other, the behaviour of the pile group would be similar to a single pile. With increasing pile spacing in a group, the displacement field between piles decreases and, also, shear strain created in the soil around the lead pile increases. In front of laterally loaded piles, the horizontal displacements are generally larger than vertical ones, and these two values decrease with an increase in the distance from the soil surface.
Many buildings and structures require the use of deep foundations to utilize the bearing capacity of stronger soil layers. Pile groups are one particular type of deep foundation commonly used for large structures. In addition to vertical loads that must be sustained by the piles, significant lateral loads may be present and must be accounted for in the design. These lateral loads can come from a variety of sources, such as wind forces, collisions, wave or ice impact, earthquake shaking, liquefaction and slope failure. A pile group subjected to lateral loading is nfluenced by the existence of neighboring piles. This pile-soil-pile interaction is strongly dependent on the pile-to-pile spacing, which dominates the pattern of stress and deformation around a pile group. Full-scale tests are generally believed to provide the most accurate results, but are rare due to high costs. Therefore, many studies are available concerning centrifuge and model testing. In this paper, the behaviour of soil around laterally loaded pile groups in sand for different cases were studied and interpreted in the laboratory on small scale physical models, using the Particle Image Velocimetry (PIV) method. The group effect and interaction between piles in a pile group were also studied. A wooden box was used as the test box. A transparent sheet was used in place of a fourth wooden wall. Plexiglass was used to allow observation of the deformations in the soil sample. The soil was fine, dry sand. The soil was placed in the box using a sand raining system, in order to obtain a uniform and homogeneous medium. Rectangular piles were selected, in order to apply the similitude law. The smallest dimensions of piles were in contact with the Plexiglass. The 2$times$ 1 pile group model, with different pile spacing, was used in the direction of the load. An aluminous cap was used to connect two pile heads. Each pile was joined by a hinge (free rotation) to the cap. An electromotor with uniform velocity was used to apply lateral load statically to the pile group cap. A LVDT displacement sensor and a sensitive load cell were installed in order to record the pile head displacement and applied force. A digital camera was used for visualization of the soil movements and for image processing. The tests were performed by varying the pile centre-to-centre spacing from 1 to 6 times the pile widths (B). One test was performed on a laterally loaded single pile. Soil displacement vectors, soil shear strain and the soil displacement field around a laterally loaded single pile and pile groups, were obtained by image processing using the PIV method. Also, the load --- deflection curve for pile heads was obtained. It is found that, although a pile-group strengthens overall lateral load resistance it can weaken the individual pile response of the piles in the group. The overall lateral load is divided among each of the piles in the group. Each pile pushes against the soil behind it, creating a shear zone in the soil. These shear zones begin to enlarge and overlap as the lateral load increases. More overlapping occurs if the piles are spaced very closely together. In the case of 1B space between piles, the soil between the two piles has very low resistance against the horizontal displacement of the trail pile. In the case of 6B space between piles, the displacements of soil around each pile have no overlaps. It can be concluded that the interaction between piles decreases with increasing pile space. Also, in the case of 1B space between piles, strain wedges are overlapped, which shows the interaction of two piles. In this case, the created strain wedge is very similar to a single pile with larger width. This means that when two piles are very close to each other, the behaviour of the pile group would be similar to a single pile. With increasing pile spacing in a group, the displacement field between piles decreases and, also, shear strain created in the soil around the lead pile increases. In front of laterally loaded piles, the horizontal displacements are generally larger than vertical ones, and these two values decrease with an increase in the distance from the soil surface.
https://sjce.journals.sharif.edu/article_633_26dd0dbc6e3f4c8043749885523d6a25.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
SEISMIC VULNERABILITY ASSESSMENT OF MASONRY BUILDINGS BY THE CAPACITY SPECTRUM KINEMATIC LIMIT ANALYSIS M
SEISMIC VULNERABILITY ASSESSMENT OF MASONRY BUILDINGS BY THE CAPACITY SPECTRUM KINEMATIC LIMIT ANALYSIS M
103
109
634
FA
S.R
Pashanejati
Building & Housing Faculty
P.
Homami
Faculty of Engineering & Technology\r\nKharazmi U
0000-0002-4993-8628
Journal Article
2009
11
10
Earthquakes are an important hazard for masonry buildings and historical constructions. Recent earthquakes have shown a deficient performance of masonry buildings under seismic loading. In relevance to the importance of this topic, different methods have been presented for the seismic vulnerability assessment of masonry constructions, like linear and nonlinear finite element methods, including limit analysis etc. Limit analysis is a good technique for estimating the ultimate limit state of the structure, because of the simplification of assumption, reducing the number of necessary mechanical properties and giving the ultimate condition of the structure in a critical section. On the other hand, in existing masonry buildings, partial collapses (local failure mechanisms) generally occur; very often due to the loss of equilibrium in masonry portions in earthquakes. Verifications of collapse (in-plane and out of- plane), with reference to those local failure mechanisms, can be done by means of the limit equilibrium analysis, based on the kinematics approach, which depends on selection of the failure mechanism and evaluation of the horizontal forces that generate that kinematic mechanism. Therefore, for application of kinematic limit analysis, it is necessary to identify the different collapse mechanisms. The determination of an abacus of failure mechanism is an important issue, as a good interpretation of the vulnerability of the building, which directly relates to the identification of failure mechanisms. The basis of this method is to find the safety factor of each failure mechanism, due to the kinematical stability imposed on the lateral load. For these reasons, evaluating the ultimate load bearing capacity of an entire masonry building subjected to horizontal loads is a fundamental task for the design of masonry buildings in some codes, for instance, the recent Italian Ordinance PCM 3274 & modifications OPCM 3431 of 3/05/05, which pays due attention to the kinematic limit analysis. This verification can be developed through a simplified verification, with behavior factor q (linear kinematic analysis) and the capacity spectrum (non-linear kinematic analysis). In the capacity spectrum (non-linear kinematic analysis) method, based on appendix 11.c of the Italian rdinance, the safety verifications for local failure mechanisms in the ultimate limit state, consist of a comparison of the ultimate displacement capacity of each local failure mechanism with the displacement demand evaluated by means of a response spectrum, defined similarly to that adopted for the assessment of non-structural elements, estimated in respect to the secant period (Ts). This paper presents an application of the Capacity Spectrum Kinematic Limit Analysis (nonlinear) to assess typical masonry buildings. The safety of the building against 21 failure mechanisms, due to in-plane and out-of-plane behavior, and also, the overturning of parapets in an earthquake with 10% probability of occurrence over 50 years, has been studied. The vulnerability of the structure was assessed, in compliance with the Limit Analysis Method presented in the O.P.C.M 3431 Italian code. At the end, the results of the assessment based on the Italian code has been compared with the results of the same calculation based on the Iranian code.
Earthquakes are an important hazard for masonry buildings and historical constructions. Recent earthquakes have shown a deficient performance of masonry buildings under seismic loading. In relevance to the importance of this topic, different methods have been presented for the seismic vulnerability assessment of masonry constructions, like linear and nonlinear finite element methods, including limit analysis etc. Limit analysis is a good technique for estimating the ultimate limit state of the structure, because of the simplification of assumption, reducing the number of necessary mechanical properties and giving the ultimate condition of the structure in a critical section. On the other hand, in existing masonry buildings, partial collapses (local failure mechanisms) generally occur; very often due to the loss of equilibrium in masonry portions in earthquakes. Verifications of collapse (in-plane and out of- plane), with reference to those local failure mechanisms, can be done by means of the limit equilibrium analysis, based on the kinematics approach, which depends on selection of the failure mechanism and evaluation of the horizontal forces that generate that kinematic mechanism. Therefore, for application of kinematic limit analysis, it is necessary to identify the different collapse mechanisms. The determination of an abacus of failure mechanism is an important issue, as a good interpretation of the vulnerability of the building, which directly relates to the identification of failure mechanisms. The basis of this method is to find the safety factor of each failure mechanism, due to the kinematical stability imposed on the lateral load. For these reasons, evaluating the ultimate load bearing capacity of an entire masonry building subjected to horizontal loads is a fundamental task for the design of masonry buildings in some codes, for instance, the recent Italian Ordinance PCM 3274 & modifications OPCM 3431 of 3/05/05, which pays due attention to the kinematic limit analysis. This verification can be developed through a simplified verification, with behavior factor q (linear kinematic analysis) and the capacity spectrum (non-linear kinematic analysis). In the capacity spectrum (non-linear kinematic analysis) method, based on appendix 11.c of the Italian rdinance, the safety verifications for local failure mechanisms in the ultimate limit state, consist of a comparison of the ultimate displacement capacity of each local failure mechanism with the displacement demand evaluated by means of a response spectrum, defined similarly to that adopted for the assessment of non-structural elements, estimated in respect to the secant period (Ts). This paper presents an application of the Capacity Spectrum Kinematic Limit Analysis (nonlinear) to assess typical masonry buildings. The safety of the building against 21 failure mechanisms, due to in-plane and out-of-plane behavior, and also, the overturning of parapets in an earthquake with 10% probability of occurrence over 50 years, has been studied. The vulnerability of the structure was assessed, in compliance with the Limit Analysis Method presented in the O.P.C.M 3431 Italian code. At the end, the results of the assessment based on the Italian code has been compared with the results of the same calculation based on the Iranian code.
https://sjce.journals.sharif.edu/article_634_6766aa2750c19aad2fa1b32f36ed4aee.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
ESTIMATION OF BREAKING SOLITARY WAVE PRESSURE ON MOORED PONTOON FLOATING BREAKWATERS USING VOF METHOD
ESTIMATION OF BREAKING SOLITARY WAVE PRESSURE ON MOORED PONTOON FLOATING BREAKWATERS USING VOF METHOD
111
122
635
FA
H.
Rezaei
Faculty of Marine Technology Amirkabir Univer
M. J.
Ketabdari
Faculty of Marine Technology Amirkabir Univer
Journal Article
2010
12
07
Incompressible viscous flow with moving free surface is an important phenomenon in nature which has broad application in engineering. For these flows, determination of the temporal and spatial position of this moving free surface under unsteady or non-uniform conditions is very difficult. One of the most complicated phenomena in the coastal zone is wave breaking. The study of these waves is of importance in many applications, such as destructive impact forces on marine structures, and cross-shore and long-shore sediment transport. Being highly nonlinear, transient and complex, a theoretical analysis of wave impact would be impossible without numerical simulations. In this study, fluid is considered as viscous and incompressible. Therefore, Navier-Stokes and continuity are considered as governing equations. To solve these equations, a finite volume method, based on the PISO algorithm, is used. The effect of turbulence was considered using the standard k-$varepsilon$ model. A two dimensional VOF model, using Donor-Acceptor algorithm as a simple line interface construction method, was developed for free surface modeling. A piston-type wave maker and Goring formula are used in the left lateral boundary condition to generate a shallow water solitary wave. A sloped beach is considered in right lateral boundary condition to simulate breaking wave. A pontoon floating breakwater is exposed to an incident wave. Euler equation is used to estimate pressure exerted on pontoon floating breakwater. To validate the present model, a dam break test is adopted as a benchmark. The results are compared with available data and show the accuracy of the developed model. Then, the velocity and pressure field, due to the interaction of a solitary wave and moored floating breakwater, was obtained, using a coupled VOF and N-S solver. To compare the effect of wave breaking force on the structure, the pontoon floating breakwater is located in and out of the breaking wave zone. The results showed that the breaking solitary wave implies much greater force than the non-breaking wave on the floating breakwater.
Incompressible viscous flow with moving free surface is an important phenomenon in nature which has broad application in engineering. For these flows, determination of the temporal and spatial position of this moving free surface under unsteady or non-uniform conditions is very difficult. One of the most complicated phenomena in the coastal zone is wave breaking. The study of these waves is of importance in many applications, such as destructive impact forces on marine structures, and cross-shore and long-shore sediment transport. Being highly nonlinear, transient and complex, a theoretical analysis of wave impact would be impossible without numerical simulations. In this study, fluid is considered as viscous and incompressible. Therefore, Navier-Stokes and continuity are considered as governing equations. To solve these equations, a finite volume method, based on the PISO algorithm, is used. The effect of turbulence was considered using the standard k-$varepsilon$ model. A two dimensional VOF model, using Donor-Acceptor algorithm as a simple line interface construction method, was developed for free surface modeling. A piston-type wave maker and Goring formula are used in the left lateral boundary condition to generate a shallow water solitary wave. A sloped beach is considered in right lateral boundary condition to simulate breaking wave. A pontoon floating breakwater is exposed to an incident wave. Euler equation is used to estimate pressure exerted on pontoon floating breakwater. To validate the present model, a dam break test is adopted as a benchmark. The results are compared with available data and show the accuracy of the developed model. Then, the velocity and pressure field, due to the interaction of a solitary wave and moored floating breakwater, was obtained, using a coupled VOF and N-S solver. To compare the effect of wave breaking force on the structure, the pontoon floating breakwater is located in and out of the breaking wave zone. The results showed that the breaking solitary wave implies much greater force than the non-breaking wave on the floating breakwater.
https://sjce.journals.sharif.edu/article_635_6a10bbd480e4c5573d8f3af73ae0454b.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
HETEROGENEOUS FUZZY GROUP DECISION MAKING IN INTEGRATED WATER RESOURCES MANAGEMENT
HETEROGENEOUS FUZZY GROUP DECISION MAKING IN INTEGRATED WATER RESOURCES MANAGEMENT
123
131
636
FA
H.
Mianabadi
Dept. of Civil Engineering Iran University of Scie&
A.
Afshar
Dept. of Civil EngineeringIran University of Scie&z
Journal Article
2009
07
15
The complexity of water resource management issues and their direct relation to other sciences has caused the single decision maker (DM) to be unable to consider all aspects and criteria of water resources planning and management problems. Therefore, it is necessary to use group decision-making methods to consider DMs opinions, as well as qualitative and quantitative criteria, simultaneously, in this field. The aim of this paper is to develop a new process for the consensus-based heterogeneous group decision-making models. In addition, introducing the group decision-making process and studying its efficiency in integrated water resources planning and management are presented. A case study of water resources management is used to illustrate application of the proposed process in integrated water resources management problems. Two states of homogeneous and heterogeneous group decision making are also used to examine the efficiency of the presented method in water resources problems. Results reveal the importance of considering and calculating the DMs weight in group decision-making processes and its efficiency and application in water resources planning and management problems.
The complexity of water resource management issues and their direct relation to other sciences has caused the single decision maker (DM) to be unable to consider all aspects and criteria of water resources planning and management problems. Therefore, it is necessary to use group decision-making methods to consider DMs opinions, as well as qualitative and quantitative criteria, simultaneously, in this field. The aim of this paper is to develop a new process for the consensus-based heterogeneous group decision-making models. In addition, introducing the group decision-making process and studying its efficiency in integrated water resources planning and management are presented. A case study of water resources management is used to illustrate application of the proposed process in integrated water resources management problems. Two states of homogeneous and heterogeneous group decision making are also used to examine the efficiency of the presented method in water resources problems. Results reveal the importance of considering and calculating the DMs weight in group decision-making processes and its efficiency and application in water resources planning and management problems.
https://sjce.journals.sharif.edu/article_636_c5ab0bc60ac7929182aadd08703f1ec6.pdf
Sharif University of Technology
Sharif Journal of Civil Engineering
2676-4768
Volume 2-27
4
2012
01
21
AN INVESTIGATION OF DESIGN PROVISIONS OF SELF SUPPORTING TELECOMMUNICATION \r\nTOWERS AND IDENTIFYING THE OPTIMUM GEOMETRY
AN INVESTIGATION OF DESIGN PROVISIONS OF SELF SUPPORTING TELECOMMUNICATION \r\nTOWERS AND IDENTIFYING THE OPTIMUM GEOMETRY
133
143
637
FA
M.G.
Sahab
Dept. of Civil ngineering\r\nTafresh University
A.
Falahnezhad
Dept. of Civil Engineering\r\nTafresh University
Journal Article
2009
09
01
Steel latticed towers are special and important structures in structural engineering. Free-standing latticed communication towers are designed and constructed with different geometries, in view of cross and longitudinal section shapes, and topology. In this paper, many well-known codes of practice, which are used for the design of telecommunication towers in Iran, are investigated and compared with each other. 84 free standing telecommunication towers with cross bracing and square and triangle cross sections, with three different heights of 30, 81 and 121 meters, are analyzed and designed, using the SAP2000$_{V11}$ computer software, based on TIA/EIA-222-F(1996) Code of practice. The weights and structural behavior of these telecommunication towers, is evaluated and compared with each other. Among the 84 mentioned towers, the least weight belongs to towers with triangular cross sections, having a tapered longitudinal section in the lower part and a rectangular longitudinal section in the upper part. In respect of the transverse deflection and rotation about the vertical axis, towers with a square cross section have lesser values of deflection and rotation than those of towers with triangular cross sections. Although towers with rectangular cross sections may be preferred to those with triangular sections as far as the restriction of lateral deflections, it has been demonstrated that the total weight of towers with triangular cross sections may be less than those of towers with rectangular cross sections up to 40%, designed for the same loads.
Steel latticed towers are special and important structures in structural engineering. Free-standing latticed communication towers are designed and constructed with different geometries, in view of cross and longitudinal section shapes, and topology. In this paper, many well-known codes of practice, which are used for the design of telecommunication towers in Iran, are investigated and compared with each other. 84 free standing telecommunication towers with cross bracing and square and triangle cross sections, with three different heights of 30, 81 and 121 meters, are analyzed and designed, using the SAP2000$_{V11}$ computer software, based on TIA/EIA-222-F(1996) Code of practice. The weights and structural behavior of these telecommunication towers, is evaluated and compared with each other. Among the 84 mentioned towers, the least weight belongs to towers with triangular cross sections, having a tapered longitudinal section in the lower part and a rectangular longitudinal section in the upper part. In respect of the transverse deflection and rotation about the vertical axis, towers with a square cross section have lesser values of deflection and rotation than those of towers with triangular cross sections. Although towers with rectangular cross sections may be preferred to those with triangular sections as far as the restriction of lateral deflections, it has been demonstrated that the total weight of towers with triangular cross sections may be less than those of towers with rectangular cross sections up to 40%, designed for the same loads.
https://sjce.journals.sharif.edu/article_637_a532400ed62e772b9dc0b86f46e583ff.pdf