As jack-up platforms have recently been used in deeper and harsher waters,there has been an increasing demand to understand their behaviour more accurately to develop more sophisticated analysis techniques.One of the ...As jack-up platforms have recently been used in deeper and harsher waters,there has been an increasing demand to understand their behaviour more accurately to develop more sophisticated analysis techniques.One of the areas of significant development has been the modelling of spudcan performance,where the load-displacement behaviour of the foundation is required to be included in any numerical model of the structure.In this study,beam on nonlinear winkler foundation(BNWF) modeling—which is based on using nonlinear springs and dampers instead of a continuum soil media—is employed for this purpose.A regular monochrome design wave and an irregular wave representing a design sea state are applied to the platform as lateral loading.By using the BNWF model and assuming a granular soil under spudcans,properties such as soil nonlinear behaviour near the structure,contact phenomena at the interface of soil and spudcan(such as uplifting and rocking),and geometrical nonlinear behaviour of the structure are studied.Results of this study show that inelastic behaviour of the soil causes an increase in the lateral displacement at the hull elevation and permanent unequal settlement in soil below the spudcans,which are increased by decreasing the friction angle of the sandy soil.In fact,spudcans and the underlying soil cause a relative fixity at the platform support,which changes the dynamic response of the structure compared with the case where the structure is assumed to have a fixed support or pinned support.For simulating this behaviour without explicit modelling of soil-structure interaction(SSI),momentrotation curves at the end of platform legs,which are dependent on foundation dimensions and soil characteristics,are obtained.These curves can be used in a simplified model of the platform for considering the relative fixity at the soilfoundation interface.展开更多
Earthquake engineering research and development have received much attention since the first half of the twentieth century. This valuable research presented a huge step forward in understanding earthquake hazard mitig...Earthquake engineering research and development have received much attention since the first half of the twentieth century. This valuable research presented a huge step forward in understanding earthquake hazard mitigation,which resulted in appreciable reduction of the effects of past earthquakes. Nevertheless,the 2011 Tohoku earthquake and the subsequent tsunami resulted in major damage. This paper presents the timeline of earthquake mitigation and recovery,as seen by the authors. Possible research directions where the authors think that many open questions still remain are identified. These are primarily based on the important lessons learned from the 2011 Tohoku earthquake.展开更多
Two genes(GhC4H1 and GhC4H2) that encode putative cotton cinnamate 4-hydroxylases that catalyze the second step in the phenylpropanoid pathway were isolated from developing cotton fibers. GhC4H1 and GhC4H2 each contai...Two genes(GhC4H1 and GhC4H2) that encode putative cotton cinnamate 4-hydroxylases that catalyze the second step in the phenylpropanoid pathway were isolated from developing cotton fibers. GhC4H1 and GhC4H2 each contain open reading frames of 1 518 base pairs(bp) in length and both encode proteins consisting of 505 amino acid residues. They are 90.89% identical to each other at the amino acid sequence level and belong to class I of plant C4 Hs. GhC4H1 and GhC4H2 genomic DNA are 2 247 and 2 161 bp long, respectively, and contain two introns located at conserved positions relative to the coding sequence. GhC4H1 and GhC4H2 promoters were isolated and found to contain many cis-elements(boxes P, L and AC-I element) previously identified in the promoters of other phenylpropanoid pathway genes. Histochemical staining showed GUS expression driven by the GhC4H1 and GhC4H2 promoters in ovules and fibers tissues. GhC4H1 and GhC4H2 were also widely expressed in other cotton tissues. GhC4H2 expression reached its highest level during the elongation stage of fiber development, whereas GhC4H1 expression increased during the secondary wall development period in cotton fibers. Our results contribute to a better understanding of the biochemical role of GhC4H1 and GhC4H2 in cotton fiber development.展开更多
Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior,yet only a few experimental works and analytical models have been reported,most o...Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior,yet only a few experimental works and analytical models have been reported,most of which are based on the global rock bolt response evaluated in pull-out tests.This paper presents a laboratory experimental setup aiming to capture the rock formation effect,while using distributed fiber optic sensing to quantify the effect of the confinement and the reinforcement pull-out behavior on a more local level.It is shown that the behavior along the sample itself varies,with certain points exhibiting stress drops with crack formation.Some edge effects related to the kinematic freedom of the grout to dilate are also observed.Regardless,it was found that the mid-level response is quite similar to the average response along the sample.The ability to characterize the variation of the response along the sample is one of the many advantages high-resolution fiber optic sensing allows in such investigations.The paper also offers a plasticity-based hardening load transfer function,representing a"slice"of the anchor.The paper describes in detail the development of the model and the calibration/determination of its parameters.The suggested model captures well the coupled behavior in which the pull-out process leads to an increase in the confining stress due to dilative behavior.展开更多
One of the founders of structural control theory and its application in civil engineering,Professor Emeritus Tsu T.Soong,envisioned the development of the integral design of structures protected by active control devi...One of the founders of structural control theory and its application in civil engineering,Professor Emeritus Tsu T.Soong,envisioned the development of the integral design of structures protected by active control devices.Most of his disciples and colleagues continuously attempted to develop procedures to achieve such integral control.In his recent papers published jointly with some of the authors of this paper,Professor Soong developed design procedures for the entire structure using a design-redesign procedure applied to elastic systems.Such a procedure was developed as an extension of other work by his disciples.This paper summarizes some recent techniques that use traditional active control algorithms to derive the most suitable(optimal,stable) control force,which could then be implemented with a combination of active,passive and semi-active devices through a simple match or more sophisticated optimal procedures.Alternative design can address the behavior of structures using Liapunov stability criteria.This paper shows a unifi ed procedure which can be applied to both elastic and inelastic structures.Although the implementation does not always preserve the optimal criteria,it is shown that the solutions are effective and practical for design of supplemental damping,stiffness enhancement or softening,and strengthening or weakening.展开更多
Objective To check whether health risk impacts of exposure to airborne metals and Benzo(a) Pyrene during episodes of high PM_(10) concentrations lead to an increased number of lung cancer cases in Poland.Methods In th...Objective To check whether health risk impacts of exposure to airborne metals and Benzo(a) Pyrene during episodes of high PM_(10) concentrations lead to an increased number of lung cancer cases in Poland.Methods In this work,we gathered data from 2002 to 2014 concerning the ambient concentrations of PM_(10) and PM_(10)-bound carcinogenic Benzo(a)pyrene [B(a)P] and As,Cd,Pb,and Ni.With the use of the criterion of the exceedance in the daily PM_(10) mass concentration on at least 50% of all the analyzed stations,the PM_(10) maxima's were selected.Lung cancer occurrences in periods with and without the episodes were further compared.Results During a 12-year period,348 large-scale smog episodes occurred in Poland.A total of 307 of these episodes occurred in the winter season,which is characterized by increased emissions from residential heating.The occurrence of episodes significantly(P < 0.05) increased the concentrations of PM_(10)-bound carcinogenic As,Cd,Pb,Ni,and B(a)P.During these events,a significant increase in the overall health risk from those PM_(10)-related compounds was also observed.The highest probability of lung cancer occurrences was found in cities,and the smallest probability was found in the remaining areas outside the cities and agglomerations.Conclusion The link between PM pollution and cancer risk in Poland is a serious public health threat that needs further investigation.展开更多
This study was conducted to assess the performance of modified asphalt binders and engineering properties of mixtures prepared with incorporation 3 vol%and 6 vol%of calcium carbonate(CaCO3),linear low-density polyethy...This study was conducted to assess the performance of modified asphalt binders and engineering properties of mixtures prepared with incorporation 3 vol%and 6 vol%of calcium carbonate(CaCO3),linear low-density polyethylene(LLDPE),and combinations of CaCO3 and LLDPE.The rheological properties of control and modified asphalt binders were evaluated using a series of testing such as rotational viscometer(RV),multiple stress creep recovery(MSCR)and bending beam rheometer(BBR)tests.Meanwhile,four-point beam fatigue test,the dynamic modulus(E*)test and tensile strength ratio(TSR)test were conducted to assess the engineering properties of asphalt mixtures.Based on the findings,the RV and MSCR test result shows that all modified asphalt binders have improved performance in comparison to the neat asphalt binders in terms of higher viscosity and improved permanent deformation resistance.A higher amount of CaCO3 and LLDPE have led modified asphalt binders to better recovery percentage,except the asphalt binders modified using a combination of CaCO3 and LLDPE.However,the inclusion of LLDPE into asphalt binder has lowered the thermal cracking resistance.The incorporation of CaCO3 in asphalt mixtures was found beneficial,especially in improving the ability to resist fatigue cracking of asphalt mixture.In contrast,asphalt mixtures show better moisture sensitivity through the addition of LLDPE.The addition of LLDPE has significantly enhanced the indirect tensile strength values and tensile strength ratio of asphalt mixtures.展开更多
This paper sums up the determining analysis of the measuring location of Treflusing a thermocouple during the thermography tests.Laboratory temperature distribution testing methods,analysis of value and location of Tre...This paper sums up the determining analysis of the measuring location of Treflusing a thermocouple during the thermography tests.Laboratory temperature distribution testing methods,analysis of value and location of Treflmeasurement are explained in this paper.The heat source is two halogen lamps of 500 watts eachfitted at a distance of 30–50 cm.Noises appearing during testing of thermography are corrected with measured T_(refl) value.The results of thermogram correction of corroded concrete surfaces using T_(refl) values are displayed in this paper too.The concrete surface temperature results of quantitative image processing method are compared to the experimental test results.The results showed good accuracy,which was seen from most errors<3%and the maximum error is<5%.The end of paper,explained of application Treflvalue to the corroded reinforced concrete thermogram.展开更多
This study aims to develop several optimization techniques for predicting advance rate of tunnel boring machine(TBM)in different weathered zones of granite.For this purpose,extensive field and laboratory studies have ...This study aims to develop several optimization techniques for predicting advance rate of tunnel boring machine(TBM)in different weathered zones of granite.For this purpose,extensive field and laboratory studies have been conducted along the 12,649 m of the Pahang-Selangor raw water transfer tunnel in Malaysia.Rock properties consisting of uniaxial compressive strength(UCS),Brazilian tensile strength(BTS),rock mass rating(RMR),rock quality designation(RQD),quartz content(q)and weathered zone as well as machine specifications including thrust force and revolution per minute(RPM)were measured to establish comprehensive datasets for optimization.Accordingly,to estimate the advance rate of TBM,two new hybrid optimization techniques,i.e.an artificial neural network(ANN)combined with both imperialist competitive algorithm(ICA)and particle swarm optimization(PSO),were developed for mechanical tunneling in granitic rocks.Further,the new hybrid optimization techniques were compared and the best one was chosen among them to be used for practice.To evaluate the accuracy of the proposed models for both testing and training datasets,various statistical indices including coefficient of determination(R^2),root mean square error(RMSE)and variance account for(VAF)were utilized herein.The values of R^2,RMSE,and VAF ranged in 0.939-0.961,0.022-0.036,and 93.899-96.145,respectively,with the PSO-ANN hybrid technique demonstrating the best performance.It is concluded that both the optimization techniques,i.e.PSO-ANN and ICA-ANN,could be utilized for predicting the advance rate of TBMs;however,the PSO-ANN technique is superior.展开更多
The accurate analysis of the seismic response of isolated structures requires incorporation of the flexibility of supporting soil.However,it is often customary to idealize the soil as rigid during the analysis of such...The accurate analysis of the seismic response of isolated structures requires incorporation of the flexibility of supporting soil.However,it is often customary to idealize the soil as rigid during the analysis of such structures.In this paper,seismic response time history analyses of base-isolated buildings modelled as linear single degree-of-freedom(SDOF) and multi degree-of-freedom(MDOF) systems with linear and nonlinear base models considering and ignoring the flexibility of supporting soil are conducted.The flexibility of supporting soil is modelled through a lumped parameter model consisting of swaying and rocking spring-dashpots.In the analysis,a large number of parametric studies for different earthquake excitations with three different peak ground acceleration(PGA) levels,different natural periods of the building models,and different shear wave velocities in the soil are considered.For the isolation system,laminated rubber bearings(LRBs) as well as high damping rubber bearings(HDRBs) are used.Responses of the isolated buildings with and without SSI are compared under different ground motions leading to the following conclusions:(1) soil flexibility may considerably influence the stiff superstructure response and may only slightly influence the response of the flexible structures;(2) the use of HDRBs for the isolation system induces higher structural peak responses with SSI compared to the system with LRBs;(3) although the peak response is affected by the incorporation of soil flexibility,it appears insensitive to the variation of shear wave velocity in the soil;(4) the response amplifications of the SDOF system become closer to unit with the increase in the natural period of the building,indicating an inverse relationship between SSI effects and natural periods for all the considered ground motions,base isolations and shear wave velocities;(5) the incorporation of SSI increases the number of significant cycles of large amplitude accelerations for all the stories,especially for earthquakes with low and moderate PGA levels;and(6) buildings with a linear LRB base-isolation system exhibit larger differences in displacement and acceleration amplifications,especially at the level of the lower stories.展开更多
In this study,a novel rotational damper called a Rotational Friction Viscoelastic Damper(RFVD) is introduced.Some viscoelastic pads are added to the Rotational Friction Damper(RFD) in addition to the friction discs us...In this study,a novel rotational damper called a Rotational Friction Viscoelastic Damper(RFVD) is introduced.Some viscoelastic pads are added to the Rotational Friction Damper(RFD) in addition to the friction discs used in this conventional device.Consequently,the amount of energy dissipated by the damper increases in low excitation frequencies.In fact,the input energy to the structure is simultaneously dissipated in the form of friction and heat by frictional discs and viscoelastic pads.In order to compare the performance of this novel damper with the earlier types,a set of experiments were carried out.According to the test results,the RFVD showed a better performance in dissipating input energy to the structure when compared to the RFD.The seismic behavior of steel frames equipped with these dampers was also numerically evaluated based on a nonlinear time history analysis.The numerical results verifi ed the performance of the dampers in increasing the energy dissipation and decreasing the energy input to the structural elements.In order to achieve the maximum dissipated energy,the dampers need to be installed in certain places called critical points in the structure.An appropriate approach is presented to properly fi nd these points.Finally,the performance of the RFVDs installed at these critical points was investigated in comparison to some other confi gurations and the validity of the suggested method in increasing the energy dissipation was confi rmed.展开更多
Flooding is a common natural disaster that causes enormous economic, social, and human losses. Of various flood routing methods, the dynamic wave model is one of the best approaches for the prediction of the character...Flooding is a common natural disaster that causes enormous economic, social, and human losses. Of various flood routing methods, the dynamic wave model is one of the best approaches for the prediction of the characteristics of floods during their propagations in natural rivers because all of the terms of the momentum equation are considered in the model. However, no significant research has been conducted on how the model sensitivity affects the accuracy of the downstream hydrograph. In this study, a comprehensive analysis of the input parameters of the dynamic wave model was performed through field applications in natural rivers and routing experiments in artificial channels using the graphical multi-parametric sensitivity analysis (GMPSA). The results indicate that the effects of input parameter errors on the output results are more significant in special situations, such as lower values of Manning's roughness coefficient and/or a steeper bed slope on the characteristics of a design hydrograph, larger values of the skewness factor and/or time to peak on the channel characteristics, larger values of Manning's roughness coefficient and/or the bed slope on the space step, and lower values of Manning's roughness coefficient and/or a steeper bed slope on the time step and weighting factor.展开更多
The purpose of this study is to survey the impact of climate change on the runoff of Gharehsoo River in northwest of Iran. In this research the outputs of monthly precipitation and temperature data of PRECIS model, wh...The purpose of this study is to survey the impact of climate change on the runoff of Gharehsoo River in northwest of Iran. In this research the outputs of monthly precipitation and temperature data of PRECIS model, which is a regional climate model with 50 × 50 km resolution on the basis of B2 scenario, have been utilized for base (1961-1990) and future (2071-2100) periods. The output results of PRECIS model show that the average temperature of watershed increased up to 2°C - 5°C. In addition, future precipitation is more than the base precipitation on January, February, March, September and December. The observed data of 1996-2002 used for calibration of HSPF model and the data of 2003-2004 were used for HSPF validation. The present monthly patterns for precipitation and temperature were estimated using the geostatistical techniques and the future monthly patterns were retrieved by the combination of future monthly PRECIS data and monthly patterns of precipitation and temperature. Then, the base and future precipitation and temperature patterns were introduced to validate HSPF model for the simulation of monthly runoff in the base and future periods. The results show that in the future, the discharge of Gharehsoo River watershed decreases in all of the months. In addition, the peak discharge in the future period happens one month earlier, in April, because of increase of temperature and earlier beginning of snow melting season. Finally the sensitivity analysis was performed on the monthly runoff. The results showed that monthly discharge increases 0.3% - 35.6% and decreases 0.3% - 32.6% due to 20% increase and decrease of precipitation, respectively. In addition, 1°C and 2°C increase of temperature lead to 0% - 8% and 0.1% - 15% decrease of average monthly discharge, respectively.展开更多
Replacing the entire soil-structure system with a fixed base oscillator to consider the effect of soil-structure interaction (SSI) is a common analysis method in seismic design.This technique has been included in desi...Replacing the entire soil-structure system with a fixed base oscillator to consider the effect of soil-structure interaction (SSI) is a common analysis method in seismic design.This technique has been included in design procedures such as NEHRP, ASCE, etc.by defining an equivalent fundamental period and damping ratio that can modify the response of the structure.However, recent studies indicate that the effects of SSI should be reconsidered when a structure undergoes a nonlinear displacement demand.In recent documents on Nonlinear Static Procedures (NSPs), FEMA-440 (2005), a modified damping ratio of the replacement oscillator was proposed by introducing the ductility of the soil-structure system obtained from pushover analysis.In this paper, the damping defined in FEMA-440 to include the soil-structure interaction effect is evaluated, and the accuracy of the Coefficient Method given in FEMA-440 and the Equivalent Linearization Method is studied.Although the improvements for Nonlinear Static Procedures (NSPs) in FEMA-440 are achieved for a fixed base SDOF structure, the soil effects are not perfectly obtained.Furthermore, the damping definition of a soil-structure system is extended to structures to consider bilinear behavior.展开更多
In the design process of berm breakwaters, their front slope recession has an inevitable rule in large number of model tests, and this parameter being studied. This research draws its data from Moghim's and Shekar...In the design process of berm breakwaters, their front slope recession has an inevitable rule in large number of model tests, and this parameter being studied. This research draws its data from Moghim's and Shekari's experiment results. These experiments consist of two different 2D model tests in two wave flumes, in which the berm recession to different sea state and structural parameters have been studied. Irregular waves with a JONSWAP spectrum were used in both test series. A total of 412 test results were used to cover the impact of sea state conditions such as wave height, wave period, storm duration and water depth at the toe of the structure, and structural parameters such as berm elevation from still water level, berm width and stone diameter on berm recession parameters. In this paper, a new set of equations for berm recession is derived using the M5' model tree as a machine learning approach. A comparison is made between the estimations by the new formula and the formulae recently given by other researchers to show the preference of new M5' approach.展开更多
The breakwaters have experienced many changes during their construction history.These changes have been considered to improve their performance,depending on their environmental conditions and applications.Numerical mo...The breakwaters have experienced many changes during their construction history.These changes have been considered to improve their performance,depending on their environmental conditions and applications.Numerical modelling was conducted using FLOW-3 D software.In this study,the wave overtopping from composite berm breakwater as new conceptual structure and the pressure imposed on the composite berm breakwater are considered and investigated.The results show a decrease of 84.01,70.88 and 61.42 percent of the wave overtopping in the composite berm breakwater,in comparison to the rubble mound breakwater,horizontally caisson breakwater and caisson breakwater,respectively.Also,the pressure applied to the composite berm breakwater with the pressure applied to the horizontally caisson breakwater was compared and evaluated.Composite berm breakwater compared with horizontally caisson breakwater in P1,the amount of the obtained pressure decreased by 52.09%,in P2 the amount of the obtained pressure decreased by 63.07%,in P3 decreased by 76.09%and in Pu,this pressure reduced by53.92%.For the composite berm breakwater,the impact of three types of berms,homogenous berm(Type 1),a berm consisting of armor-filter(Type 2)and multi-layer berm(Type 3)with the aim of optimizing the hydraulic responses and wave interaction on the caisson of the breakwater was examined and evaluated.In total,Type 3 will be recommended with a significant reduction in the overtopping values and maximum pressure.展开更多
The mixing of two or more components belongs to the category of the most common unit operations, both in technology and in nature. One particular version is homogenization(blending), the effectivity of which is strong...The mixing of two or more components belongs to the category of the most common unit operations, both in technology and in nature. One particular version is homogenization(blending), the effectivity of which is strongly related to the blending time. Among many differentiated individual solutions of mixing systems used in blenders, one should distinguish the class of agitators with diffusers. An analysis of the character of the velocity field during a blending chamber operation leads to the conclusion that it would be of avail to outfit a straight diffuser with different setups of elbows. In consequence, the vertical direction of the inflowing fluid stream would be changed into the horizontal direction of the outflowing stream, which should intensify the blending process. The concept has been verified experimentally, making use of the tracer methodology. The obtained results confirmed the theoretical conclusion that the blending time for the swirling-diffuser was shorter than for the classical straight one.展开更多
文摘As jack-up platforms have recently been used in deeper and harsher waters,there has been an increasing demand to understand their behaviour more accurately to develop more sophisticated analysis techniques.One of the areas of significant development has been the modelling of spudcan performance,where the load-displacement behaviour of the foundation is required to be included in any numerical model of the structure.In this study,beam on nonlinear winkler foundation(BNWF) modeling—which is based on using nonlinear springs and dampers instead of a continuum soil media—is employed for this purpose.A regular monochrome design wave and an irregular wave representing a design sea state are applied to the platform as lateral loading.By using the BNWF model and assuming a granular soil under spudcans,properties such as soil nonlinear behaviour near the structure,contact phenomena at the interface of soil and spudcan(such as uplifting and rocking),and geometrical nonlinear behaviour of the structure are studied.Results of this study show that inelastic behaviour of the soil causes an increase in the lateral displacement at the hull elevation and permanent unequal settlement in soil below the spudcans,which are increased by decreasing the friction angle of the sandy soil.In fact,spudcans and the underlying soil cause a relative fixity at the platform support,which changes the dynamic response of the structure compared with the case where the structure is assumed to have a fixed support or pinned support.For simulating this behaviour without explicit modelling of soil-structure interaction(SSI),momentrotation curves at the end of platform legs,which are dependent on foundation dimensions and soil characteristics,are obtained.These curves can be used in a simplified model of the platform for considering the relative fixity at the soilfoundation interface.
文摘Earthquake engineering research and development have received much attention since the first half of the twentieth century. This valuable research presented a huge step forward in understanding earthquake hazard mitigation,which resulted in appreciable reduction of the effects of past earthquakes. Nevertheless,the 2011 Tohoku earthquake and the subsequent tsunami resulted in major damage. This paper presents the timeline of earthquake mitigation and recovery,as seen by the authors. Possible research directions where the authors think that many open questions still remain are identified. These are primarily based on the important lessons learned from the 2011 Tohoku earthquake.
基金funded by the National Natural Science Foundation of China(31060173)the Joint Funds of the National Natural Science Foundation of China(U1178305)the High-Tech R&D Program of Xinjiang,China(201111116)
文摘Two genes(GhC4H1 and GhC4H2) that encode putative cotton cinnamate 4-hydroxylases that catalyze the second step in the phenylpropanoid pathway were isolated from developing cotton fibers. GhC4H1 and GhC4H2 each contain open reading frames of 1 518 base pairs(bp) in length and both encode proteins consisting of 505 amino acid residues. They are 90.89% identical to each other at the amino acid sequence level and belong to class I of plant C4 Hs. GhC4H1 and GhC4H2 genomic DNA are 2 247 and 2 161 bp long, respectively, and contain two introns located at conserved positions relative to the coding sequence. GhC4H1 and GhC4H2 promoters were isolated and found to contain many cis-elements(boxes P, L and AC-I element) previously identified in the promoters of other phenylpropanoid pathway genes. Histochemical staining showed GUS expression driven by the GhC4H1 and GhC4H2 promoters in ovules and fibers tissues. GhC4H1 and GhC4H2 were also widely expressed in other cotton tissues. GhC4H2 expression reached its highest level during the elongation stage of fiber development, whereas GhC4H1 expression increased during the secondary wall development period in cotton fibers. Our results contribute to a better understanding of the biochemical role of GhC4H1 and GhC4H2 in cotton fiber development.
基金funding support from the Israeli Ministry of Housing and Construction(Grant No.2028286).
文摘Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior,yet only a few experimental works and analytical models have been reported,most of which are based on the global rock bolt response evaluated in pull-out tests.This paper presents a laboratory experimental setup aiming to capture the rock formation effect,while using distributed fiber optic sensing to quantify the effect of the confinement and the reinforcement pull-out behavior on a more local level.It is shown that the behavior along the sample itself varies,with certain points exhibiting stress drops with crack formation.Some edge effects related to the kinematic freedom of the grout to dilate are also observed.Regardless,it was found that the mid-level response is quite similar to the average response along the sample.The ability to characterize the variation of the response along the sample is one of the many advantages high-resolution fiber optic sensing allows in such investigations.The paper also offers a plasticity-based hardening load transfer function,representing a"slice"of the anchor.The paper describes in detail the development of the model and the calibration/determination of its parameters.The suggested model captures well the coupled behavior in which the pull-out process leads to an increase in the confining stress due to dilative behavior.
文摘One of the founders of structural control theory and its application in civil engineering,Professor Emeritus Tsu T.Soong,envisioned the development of the integral design of structures protected by active control devices.Most of his disciples and colleagues continuously attempted to develop procedures to achieve such integral control.In his recent papers published jointly with some of the authors of this paper,Professor Soong developed design procedures for the entire structure using a design-redesign procedure applied to elastic systems.Such a procedure was developed as an extension of other work by his disciples.This paper summarizes some recent techniques that use traditional active control algorithms to derive the most suitable(optimal,stable) control force,which could then be implemented with a combination of active,passive and semi-active devices through a simple match or more sophisticated optimal procedures.Alternative design can address the behavior of structures using Liapunov stability criteria.This paper shows a unifi ed procedure which can be applied to both elastic and inelastic structures.Although the implementation does not always preserve the optimal criteria,it is shown that the solutions are effective and practical for design of supplemental damping,stiffness enhancement or softening,and strengthening or weakening.
文摘Objective To check whether health risk impacts of exposure to airborne metals and Benzo(a) Pyrene during episodes of high PM_(10) concentrations lead to an increased number of lung cancer cases in Poland.Methods In this work,we gathered data from 2002 to 2014 concerning the ambient concentrations of PM_(10) and PM_(10)-bound carcinogenic Benzo(a)pyrene [B(a)P] and As,Cd,Pb,and Ni.With the use of the criterion of the exceedance in the daily PM_(10) mass concentration on at least 50% of all the analyzed stations,the PM_(10) maxima's were selected.Lung cancer occurrences in periods with and without the episodes were further compared.Results During a 12-year period,348 large-scale smog episodes occurred in Poland.A total of 307 of these episodes occurred in the winter season,which is characterized by increased emissions from residential heating.The occurrence of episodes significantly(P < 0.05) increased the concentrations of PM_(10)-bound carcinogenic As,Cd,Pb,Ni,and B(a)P.During these events,a significant increase in the overall health risk from those PM_(10)-related compounds was also observed.The highest probability of lung cancer occurrences was found in cities,and the smallest probability was found in the remaining areas outside the cities and agglomerations.Conclusion The link between PM pollution and cancer risk in Poland is a serious public health threat that needs further investigation.
基金The authors grateful to express their appreciation to Specialty Minerals Inc.(Bethlehem,PA,USA),Payne&Dolan Inc.(Waukesha,WI,USA),and Dow Chemical Company(Midland,MI,USA)for donating test materials.The authors would like to acknowledge the research assistantships to Mohd Rosli Mohd Hasan,Mohd Khairul Idham Mohd Satar,Muhammad Naqiuddin Mohd Warid,and Nurul Hidayah Mohd Kamaruddin.The authors also want to acknowledge Julia A.King from the Department of Chemical Engineering of Michigan Technological University for her significant contributions in materials preparation,test design,and paper revision.It is impossible for the authors to complete the work without her effort.Any opinions,findings and conclusions expressed in this paper are those of the authors’and do not necessarily reflect the views of the official views and policies of any institution or company.
文摘This study was conducted to assess the performance of modified asphalt binders and engineering properties of mixtures prepared with incorporation 3 vol%and 6 vol%of calcium carbonate(CaCO3),linear low-density polyethylene(LLDPE),and combinations of CaCO3 and LLDPE.The rheological properties of control and modified asphalt binders were evaluated using a series of testing such as rotational viscometer(RV),multiple stress creep recovery(MSCR)and bending beam rheometer(BBR)tests.Meanwhile,four-point beam fatigue test,the dynamic modulus(E*)test and tensile strength ratio(TSR)test were conducted to assess the engineering properties of asphalt mixtures.Based on the findings,the RV and MSCR test result shows that all modified asphalt binders have improved performance in comparison to the neat asphalt binders in terms of higher viscosity and improved permanent deformation resistance.A higher amount of CaCO3 and LLDPE have led modified asphalt binders to better recovery percentage,except the asphalt binders modified using a combination of CaCO3 and LLDPE.However,the inclusion of LLDPE into asphalt binder has lowered the thermal cracking resistance.The incorporation of CaCO3 in asphalt mixtures was found beneficial,especially in improving the ability to resist fatigue cracking of asphalt mixture.In contrast,asphalt mixtures show better moisture sensitivity through the addition of LLDPE.The addition of LLDPE has significantly enhanced the indirect tensile strength values and tensile strength ratio of asphalt mixtures.
基金This research was supported by the P3MI Research Grants.Thanks to Prof.Herlien D Setio as authors who received the grant.
文摘This paper sums up the determining analysis of the measuring location of Treflusing a thermocouple during the thermography tests.Laboratory temperature distribution testing methods,analysis of value and location of Treflmeasurement are explained in this paper.The heat source is two halogen lamps of 500 watts eachfitted at a distance of 30–50 cm.Noises appearing during testing of thermography are corrected with measured T_(refl) value.The results of thermogram correction of corroded concrete surfaces using T_(refl) values are displayed in this paper too.The concrete surface temperature results of quantitative image processing method are compared to the experimental test results.The results showed good accuracy,which was seen from most errors<3%and the maximum error is<5%.The end of paper,explained of application Treflvalue to the corroded reinforced concrete thermogram.
文摘This study aims to develop several optimization techniques for predicting advance rate of tunnel boring machine(TBM)in different weathered zones of granite.For this purpose,extensive field and laboratory studies have been conducted along the 12,649 m of the Pahang-Selangor raw water transfer tunnel in Malaysia.Rock properties consisting of uniaxial compressive strength(UCS),Brazilian tensile strength(BTS),rock mass rating(RMR),rock quality designation(RQD),quartz content(q)and weathered zone as well as machine specifications including thrust force and revolution per minute(RPM)were measured to establish comprehensive datasets for optimization.Accordingly,to estimate the advance rate of TBM,two new hybrid optimization techniques,i.e.an artificial neural network(ANN)combined with both imperialist competitive algorithm(ICA)and particle swarm optimization(PSO),were developed for mechanical tunneling in granitic rocks.Further,the new hybrid optimization techniques were compared and the best one was chosen among them to be used for practice.To evaluate the accuracy of the proposed models for both testing and training datasets,various statistical indices including coefficient of determination(R^2),root mean square error(RMSE)and variance account for(VAF)were utilized herein.The values of R^2,RMSE,and VAF ranged in 0.939-0.961,0.022-0.036,and 93.899-96.145,respectively,with the PSO-ANN hybrid technique demonstrating the best performance.It is concluded that both the optimization techniques,i.e.PSO-ANN and ICA-ANN,could be utilized for predicting the advance rate of TBMs;however,the PSO-ANN technique is superior.
文摘The accurate analysis of the seismic response of isolated structures requires incorporation of the flexibility of supporting soil.However,it is often customary to idealize the soil as rigid during the analysis of such structures.In this paper,seismic response time history analyses of base-isolated buildings modelled as linear single degree-of-freedom(SDOF) and multi degree-of-freedom(MDOF) systems with linear and nonlinear base models considering and ignoring the flexibility of supporting soil are conducted.The flexibility of supporting soil is modelled through a lumped parameter model consisting of swaying and rocking spring-dashpots.In the analysis,a large number of parametric studies for different earthquake excitations with three different peak ground acceleration(PGA) levels,different natural periods of the building models,and different shear wave velocities in the soil are considered.For the isolation system,laminated rubber bearings(LRBs) as well as high damping rubber bearings(HDRBs) are used.Responses of the isolated buildings with and without SSI are compared under different ground motions leading to the following conclusions:(1) soil flexibility may considerably influence the stiff superstructure response and may only slightly influence the response of the flexible structures;(2) the use of HDRBs for the isolation system induces higher structural peak responses with SSI compared to the system with LRBs;(3) although the peak response is affected by the incorporation of soil flexibility,it appears insensitive to the variation of shear wave velocity in the soil;(4) the response amplifications of the SDOF system become closer to unit with the increase in the natural period of the building,indicating an inverse relationship between SSI effects and natural periods for all the considered ground motions,base isolations and shear wave velocities;(5) the incorporation of SSI increases the number of significant cycles of large amplitude accelerations for all the stories,especially for earthquakes with low and moderate PGA levels;and(6) buildings with a linear LRB base-isolation system exhibit larger differences in displacement and acceleration amplifications,especially at the level of the lower stories.
文摘In this study,a novel rotational damper called a Rotational Friction Viscoelastic Damper(RFVD) is introduced.Some viscoelastic pads are added to the Rotational Friction Damper(RFD) in addition to the friction discs used in this conventional device.Consequently,the amount of energy dissipated by the damper increases in low excitation frequencies.In fact,the input energy to the structure is simultaneously dissipated in the form of friction and heat by frictional discs and viscoelastic pads.In order to compare the performance of this novel damper with the earlier types,a set of experiments were carried out.According to the test results,the RFVD showed a better performance in dissipating input energy to the structure when compared to the RFD.The seismic behavior of steel frames equipped with these dampers was also numerically evaluated based on a nonlinear time history analysis.The numerical results verifi ed the performance of the dampers in increasing the energy dissipation and decreasing the energy input to the structural elements.In order to achieve the maximum dissipated energy,the dampers need to be installed in certain places called critical points in the structure.An appropriate approach is presented to properly fi nd these points.Finally,the performance of the RFVDs installed at these critical points was investigated in comparison to some other confi gurations and the validity of the suggested method in increasing the energy dissipation was confi rmed.
文摘Flooding is a common natural disaster that causes enormous economic, social, and human losses. Of various flood routing methods, the dynamic wave model is one of the best approaches for the prediction of the characteristics of floods during their propagations in natural rivers because all of the terms of the momentum equation are considered in the model. However, no significant research has been conducted on how the model sensitivity affects the accuracy of the downstream hydrograph. In this study, a comprehensive analysis of the input parameters of the dynamic wave model was performed through field applications in natural rivers and routing experiments in artificial channels using the graphical multi-parametric sensitivity analysis (GMPSA). The results indicate that the effects of input parameter errors on the output results are more significant in special situations, such as lower values of Manning's roughness coefficient and/or a steeper bed slope on the characteristics of a design hydrograph, larger values of the skewness factor and/or time to peak on the channel characteristics, larger values of Manning's roughness coefficient and/or the bed slope on the space step, and lower values of Manning's roughness coefficient and/or a steeper bed slope on the time step and weighting factor.
文摘The purpose of this study is to survey the impact of climate change on the runoff of Gharehsoo River in northwest of Iran. In this research the outputs of monthly precipitation and temperature data of PRECIS model, which is a regional climate model with 50 × 50 km resolution on the basis of B2 scenario, have been utilized for base (1961-1990) and future (2071-2100) periods. The output results of PRECIS model show that the average temperature of watershed increased up to 2°C - 5°C. In addition, future precipitation is more than the base precipitation on January, February, March, September and December. The observed data of 1996-2002 used for calibration of HSPF model and the data of 2003-2004 were used for HSPF validation. The present monthly patterns for precipitation and temperature were estimated using the geostatistical techniques and the future monthly patterns were retrieved by the combination of future monthly PRECIS data and monthly patterns of precipitation and temperature. Then, the base and future precipitation and temperature patterns were introduced to validate HSPF model for the simulation of monthly runoff in the base and future periods. The results show that in the future, the discharge of Gharehsoo River watershed decreases in all of the months. In addition, the peak discharge in the future period happens one month earlier, in April, because of increase of temperature and earlier beginning of snow melting season. Finally the sensitivity analysis was performed on the monthly runoff. The results showed that monthly discharge increases 0.3% - 35.6% and decreases 0.3% - 32.6% due to 20% increase and decrease of precipitation, respectively. In addition, 1°C and 2°C increase of temperature lead to 0% - 8% and 0.1% - 15% decrease of average monthly discharge, respectively.
文摘Replacing the entire soil-structure system with a fixed base oscillator to consider the effect of soil-structure interaction (SSI) is a common analysis method in seismic design.This technique has been included in design procedures such as NEHRP, ASCE, etc.by defining an equivalent fundamental period and damping ratio that can modify the response of the structure.However, recent studies indicate that the effects of SSI should be reconsidered when a structure undergoes a nonlinear displacement demand.In recent documents on Nonlinear Static Procedures (NSPs), FEMA-440 (2005), a modified damping ratio of the replacement oscillator was proposed by introducing the ductility of the soil-structure system obtained from pushover analysis.In this paper, the damping defined in FEMA-440 to include the soil-structure interaction effect is evaluated, and the accuracy of the Coefficient Method given in FEMA-440 and the Equivalent Linearization Method is studied.Although the improvements for Nonlinear Static Procedures (NSPs) in FEMA-440 are achieved for a fixed base SDOF structure, the soil effects are not perfectly obtained.Furthermore, the damping definition of a soil-structure system is extended to structures to consider bilinear behavior.
文摘In the design process of berm breakwaters, their front slope recession has an inevitable rule in large number of model tests, and this parameter being studied. This research draws its data from Moghim's and Shekari's experiment results. These experiments consist of two different 2D model tests in two wave flumes, in which the berm recession to different sea state and structural parameters have been studied. Irregular waves with a JONSWAP spectrum were used in both test series. A total of 412 test results were used to cover the impact of sea state conditions such as wave height, wave period, storm duration and water depth at the toe of the structure, and structural parameters such as berm elevation from still water level, berm width and stone diameter on berm recession parameters. In this paper, a new set of equations for berm recession is derived using the M5' model tree as a machine learning approach. A comparison is made between the estimations by the new formula and the formulae recently given by other researchers to show the preference of new M5' approach.
文摘The breakwaters have experienced many changes during their construction history.These changes have been considered to improve their performance,depending on their environmental conditions and applications.Numerical modelling was conducted using FLOW-3 D software.In this study,the wave overtopping from composite berm breakwater as new conceptual structure and the pressure imposed on the composite berm breakwater are considered and investigated.The results show a decrease of 84.01,70.88 and 61.42 percent of the wave overtopping in the composite berm breakwater,in comparison to the rubble mound breakwater,horizontally caisson breakwater and caisson breakwater,respectively.Also,the pressure applied to the composite berm breakwater with the pressure applied to the horizontally caisson breakwater was compared and evaluated.Composite berm breakwater compared with horizontally caisson breakwater in P1,the amount of the obtained pressure decreased by 52.09%,in P2 the amount of the obtained pressure decreased by 63.07%,in P3 decreased by 76.09%and in Pu,this pressure reduced by53.92%.For the composite berm breakwater,the impact of three types of berms,homogenous berm(Type 1),a berm consisting of armor-filter(Type 2)and multi-layer berm(Type 3)with the aim of optimizing the hydraulic responses and wave interaction on the caisson of the breakwater was examined and evaluated.In total,Type 3 will be recommended with a significant reduction in the overtopping values and maximum pressure.
文摘The mixing of two or more components belongs to the category of the most common unit operations, both in technology and in nature. One particular version is homogenization(blending), the effectivity of which is strongly related to the blending time. Among many differentiated individual solutions of mixing systems used in blenders, one should distinguish the class of agitators with diffusers. An analysis of the character of the velocity field during a blending chamber operation leads to the conclusion that it would be of avail to outfit a straight diffuser with different setups of elbows. In consequence, the vertical direction of the inflowing fluid stream would be changed into the horizontal direction of the outflowing stream, which should intensify the blending process. The concept has been verified experimentally, making use of the tracer methodology. The obtained results confirmed the theoretical conclusion that the blending time for the swirling-diffuser was shorter than for the classical straight one.
