Large thin walled cylindrical above ground tanks have become more susceptible to failure by buckling during earthquakes. In this study, three different geometries of tanks with H/D （height to diameter） ratios of 2.0...Large thin walled cylindrical above ground tanks have become more susceptible to failure by buckling during earthquakes. In this study, three different geometries of tanks with H/D （height to diameter） ratios of 2.0, 0.56, 1.0, and D/t （depth to thickness） ratios of 960.0, 1,706.67 and 640.0 respectively were analyzed for stability when subjected to the E1 Centro earthquake at the base. The Budiansky and Roth procedure was used to find the buckling loads when the tanks were empty and when they were filled with liquid up to 90% of their depth. Also, nonlinear time history analysis using ANSYS finite element computer program was performed. Analysis results show that the dynamic buckling occurs for empty tanks at very high PGA （peak ground accelerations） which are unrealistic even for major earthquakes. Furthermore, when the tanks filled with water up to 90% of its height, analysis results show that when the H/D ratio reduced by two times （i.e., from 2 to 1）, the PGA for the buckling increased by six times （increase from 0.25g to 1 .Sg）. Hence, H/D ratio plays an important role in the earthquake stability design of over ground steel tanks.展开更多
NLTHA （nonlinear time history analysis） is impractical for widespread used by the professional engineer because it requires long and inefficient computational time involving complexities when six DOF （degree of fre...NLTHA （nonlinear time history analysis） is impractical for widespread used by the professional engineer because it requires long and inefficient computational time involving complexities when six DOF （degree of freedom） per node is applied. The NLTHA nowadays is predicted by MPA （modal pushover analysis）. In this method, effects of higher modes on the dynamic response are considered to estimate seismic demands for structures. In this study, the effect of the reduction of number of DOF is analyzed using 3D NLTHA together with MPA of a rigid connection RC bridge under large earthquake motion. The results are compared with the 6 DOF NLTHA in terms of response of the structure and CPU time to obtain the most efficient computational effort. Result of NLTHA showed that the computational time of the structure both for 4 DOF （without two lateral torsional effects） and 3 DOF （without two lateral torsional and vertical displacements） was reduced significantly compared to the structure using 6 DOF. The reduction of computational time was close to fifty percent both for 4 and 3 DOF＇s. When the maximum responses between NLTHA and MPA are compared, it is found that the differences are insignificant.展开更多
It is often required to know which roadway （adjustment roadway） resistances and how much values of the resis- tances should be changed to make the airflow rates in roadways （target roadways） to certain required va...It is often required to know which roadway （adjustment roadway） resistances and how much values of the resis- tances should be changed to make the airflow rates in roadways （target roadways） to certain required values in the practice of mine ventilation. In this case, the airflow rates of the target roadways and the resistances of the roadways other than the ad- justment roadways are the given conditions and the resistances of the adjustment roadways are the solutions to be found. No straightforward method to solve the problem has been found up to now. Therefore, trial and error method using the ventilation network analysis program is utilized to solve the problem so far. The method takes long calculation time and the best answer is not necessarily obtained. The authors newly defined ＂airflow element＂ as an element of the ventilation network analysis. The resistances that satisfy the airflow requirements can be calculated straight forwardly by putting the function of the airflow element into the ventilation network analysis. The air power required for the ventilation can be minimized while meeting the airflow requirements by the advanced application of the method. The authors made the computer program fulfill the method. The program was applied to actual ventilation network and it was found that the method is very practical and the time required for the analysis is short.展开更多
The communication in the physical layer between an interrogator and a tag of a passive Radio Frequency Identification （RFID） system operating between 860-960 MHz is defined by the Gen 2 protocol. The tag can be cons...The communication in the physical layer between an interrogator and a tag of a passive Radio Frequency Identification （RFID） system operating between 860-960 MHz is defined by the Gen 2 protocol. The tag can be considered a remote executing unit or a computer that executes instructions from the Gen 2 protocol. The selection of the parameter and command configuration within the protocol limitations is critical especially if the time available for the memory operations in a passive RFID system is limited. An effort is made to map the operation of the tag not in its states of operation as elaborately explained in the protocol but rather in its elementary format. The research reported in this article identifies all the parameters that affect the dynamic operation of the tag. The operation is further divided into singulation, read and write; identifying the significant parameters in each case. The choices of the different commands that can be adopted to perform identical operations on the tag are analyzed. The elements to consider in selecting the optimum command configuration are described. The impact of the different parameter and command configuration on the singulation, read and write time is calculated and recorded using a tested Gen 2 simulator program.展开更多
文摘Large thin walled cylindrical above ground tanks have become more susceptible to failure by buckling during earthquakes. In this study, three different geometries of tanks with H/D （height to diameter） ratios of 2.0, 0.56, 1.0, and D/t （depth to thickness） ratios of 960.0, 1,706.67 and 640.0 respectively were analyzed for stability when subjected to the E1 Centro earthquake at the base. The Budiansky and Roth procedure was used to find the buckling loads when the tanks were empty and when they were filled with liquid up to 90% of their depth. Also, nonlinear time history analysis using ANSYS finite element computer program was performed. Analysis results show that the dynamic buckling occurs for empty tanks at very high PGA （peak ground accelerations） which are unrealistic even for major earthquakes. Furthermore, when the tanks filled with water up to 90% of its height, analysis results show that when the H/D ratio reduced by two times （i.e., from 2 to 1）, the PGA for the buckling increased by six times （increase from 0.25g to 1 .Sg）. Hence, H/D ratio plays an important role in the earthquake stability design of over ground steel tanks.
文摘NLTHA （nonlinear time history analysis） is impractical for widespread used by the professional engineer because it requires long and inefficient computational time involving complexities when six DOF （degree of freedom） per node is applied. The NLTHA nowadays is predicted by MPA （modal pushover analysis）. In this method, effects of higher modes on the dynamic response are considered to estimate seismic demands for structures. In this study, the effect of the reduction of number of DOF is analyzed using 3D NLTHA together with MPA of a rigid connection RC bridge under large earthquake motion. The results are compared with the 6 DOF NLTHA in terms of response of the structure and CPU time to obtain the most efficient computational effort. Result of NLTHA showed that the computational time of the structure both for 4 DOF （without two lateral torsional effects） and 3 DOF （without two lateral torsional and vertical displacements） was reduced significantly compared to the structure using 6 DOF. The reduction of computational time was close to fifty percent both for 4 and 3 DOF＇s. When the maximum responses between NLTHA and MPA are compared, it is found that the differences are insignificant.
文摘It is often required to know which roadway （adjustment roadway） resistances and how much values of the resis- tances should be changed to make the airflow rates in roadways （target roadways） to certain required values in the practice of mine ventilation. In this case, the airflow rates of the target roadways and the resistances of the roadways other than the ad- justment roadways are the given conditions and the resistances of the adjustment roadways are the solutions to be found. No straightforward method to solve the problem has been found up to now. Therefore, trial and error method using the ventilation network analysis program is utilized to solve the problem so far. The method takes long calculation time and the best answer is not necessarily obtained. The authors newly defined ＂airflow element＂ as an element of the ventilation network analysis. The resistances that satisfy the airflow requirements can be calculated straight forwardly by putting the function of the airflow element into the ventilation network analysis. The air power required for the ventilation can be minimized while meeting the airflow requirements by the advanced application of the method. The authors made the computer program fulfill the method. The program was applied to actual ventilation network and it was found that the method is very practical and the time required for the analysis is short.
文摘The communication in the physical layer between an interrogator and a tag of a passive Radio Frequency Identification （RFID） system operating between 860-960 MHz is defined by the Gen 2 protocol. The tag can be considered a remote executing unit or a computer that executes instructions from the Gen 2 protocol. The selection of the parameter and command configuration within the protocol limitations is critical especially if the time available for the memory operations in a passive RFID system is limited. An effort is made to map the operation of the tag not in its states of operation as elaborately explained in the protocol but rather in its elementary format. The research reported in this article identifies all the parameters that affect the dynamic operation of the tag. The operation is further divided into singulation, read and write; identifying the significant parameters in each case. The choices of the different commands that can be adopted to perform identical operations on the tag are analyzed. The elements to consider in selecting the optimum command configuration are described. The impact of the different parameter and command configuration on the singulation, read and write time is calculated and recorded using a tested Gen 2 simulator program.
