This paper presents in-situ seismic performance tests of a bridge before its demolition due to accumulated scouring problem. The tests were conducted on three single columns and one caisson-type foundation. The three ...This paper presents in-situ seismic performance tests of a bridge before its demolition due to accumulated scouring problem. The tests were conducted on three single columns and one caisson-type foundation. The three single columns were 1.8 m in diameter,reinforced by 30-D32 longitudinal reinforcements and laterally hooped by D16 reinforcements with spacing of 20 cm. The column height is 9.54 m,10.59 m and 10.37 m for Column P2,P3,and P4,respectively. Column P2 had no exposed foundation and was subjected to pseudo-dynamic tests with peak ground acceleration of 0.32 g first,followed by one cyclic loading test. Column P3 was the benchmark specimen with exposed length of 1.2 m on its foundation. The exposed length for Column P4 was excavated to 4 m,approximately 1/3 of the foundation length,to study the effect of the scouring problem to the column performance. Both Column P3 and Column P4 were subjected to cyclic loading tests. Based on the test results,due to the large dimension of the caisson foundation and the well graded gravel soil type that provided large lateral resistance,the seismic performance among the three columns had only minor differences. Lateral push tests were also conducted on the caisson foundation at Column P5. The caisson was 12 m long and had circular cross-sections whose diameters were 5 m in the upper portion and 4 m in the lower portion. An analytical model to simulate the test results was developed in the OpenSees platform. The analytical model comprised nonlinear flexural elements as well as nonlinear soil springs. The analytical results closely followed the experimental test results. A parametric study to predict the behavior of the bridge column with different ground motions and different levels of scouring on the foundation are also discussed.展开更多
This paper introduces to fluid state physics （fluid mechanics） a new interpretation of physical phenomena taking place in a fluid in motion. It introduces the base of a new theory claiming that every flow has its ow...This paper introduces to fluid state physics （fluid mechanics） a new interpretation of physical phenomena taking place in a fluid in motion. It introduces the base of a new theory claiming that every flow has its own internal structure of motion, which is definite organization of motion, rather than a ＂molecular chaos＂, known from the fluid statics. The paper introduces the new notion of structures vector fields of power and momentum and shows every Newtonian fluid flows are dual in character. It shows that the flow of Newtonian fluid has a dual character. It demonstrates on models and further in mathematical interpretation of physical phenomena. It introduces, on the one hand, the cycloidal motion model into the fluid mechanics, ad on the other hand an addition to the known, the classical model of Poiseuille laminar motion. The theory of dualism （double nature of physical phenomena） allows the description of selected characteristics of the flow, either by using the theory ofcycloidal motion （semicycloidal）, or by using the supplemented theory of laminar motion. The dualism theory is useful to describe each type of flows both, laminar and turbulent. This paper is only an introduction to the theory. It has been assigned number 1. It has been granted a high priority, since it contains basic concepts that will be used in others, following papers of long cycle.展开更多
To modify two-step experimental etch-and-rinse dentin adhesive with different concentrations of riboflavin and to study its effect on the bond strength,degree of conversion,along with resin infiltration within the dem...To modify two-step experimental etch-and-rinse dentin adhesive with different concentrations of riboflavin and to study its effect on the bond strength,degree of conversion,along with resin infiltration within the demineralized dentin substrate,an experimental adhesive-system was modified with different concentrations of riboflavin（mlm,0,1%,3%,5%and 10%）.Dentin surfaces were etched with 37%phosphoric acid,bonded with respective adhesives,restored with restorative composite-resin,and sectioned into resin-dentin slabs and beams to be stored for 24 h or 9 months in artificial saliva.Micro-tensile bond testing was performed with scanning electron microscopy to analyse the failure of debonded beams.The degree of conversion was evaluated with Fourier transform infrared spectroscopy（FTIR） at different time points along with micro-Raman spectroscopy analysis.Data was analyzed with one-way and two-way analysis of variance followed by Tukey＇s for pair-wise comparison.Modification with 1%and 3%riboflavin increased the micro-tensile bond strength compared to the control at 24 h and 9-month storage with no significant differences in degree of conversion（P〈0.05）.The most predominant failure mode was the mixed fracture among all specimens except 10%riboflavin-modified adhesive specimens where cohesive failure was predominant.Raman analysis revealed that 1%and 3%riboflavin adhesives specimens showed relatively higher resin infiltration.The incorporation of riboflavin in the experimental two-step etch-and-rinse adhesive at 3%（mlm） improved the immediate bond strengths and bond durability after 9-month storage in artificial saliva without adversely affecting the degree of conversion of the adhesive monomers and resin infiltration.展开更多
In the present work it is found that the pyrotechnic composition VS⁃2 can be initiated with flash lamps IFC⁃500 and EVIS.VS⁃2 pyrotechnic composition contains 90%of mercury(Ⅱ)5⁃hydrazinotetrazolate perchlorate and 10...In the present work it is found that the pyrotechnic composition VS⁃2 can be initiated with flash lamps IFC⁃500 and EVIS.VS⁃2 pyrotechnic composition contains 90%of mercury(Ⅱ)5⁃hydrazinotetrazolate perchlorate and 10%of optically trans⁃parent copolymer of 2⁃methyl⁃5⁃vinyltetrazole and methacrylic acid(PVMT).We have found that the flash lamps make it possi⁃ble to initiate combustion of VS⁃2 composition with its transition to detonation both in cylindrical charges placed in brass caps of 5 mm diameter and 2 mm high,and film charges with 10 mm×80 mm in size and surface weights of 60 mg·cm^(-2)and 90 mg·cm^(-2),showing ignition delay times 10μs and 3μs,respectively.We also measured detonation velocities for VS⁃2 composition film charges,which were 4375-4505 m·s^(-1)(of the charge being surface mass 60 mg·cm^(-2))and 4221-4281 m·s^(-1)(of the charge be⁃ing surface mass 90 mg·cm^(-2))and their blasting action on the aluminum plate.The depths of the normal shock wave imprints at the charge⁃barrier interface were 0.6-0.7 mm(for surface mass of the film charges 60 mg·cm^(-2))and 1.2-1.3 mm(for surface mass of the film charges 90 mg·cm^(-2))展开更多
文摘This paper presents in-situ seismic performance tests of a bridge before its demolition due to accumulated scouring problem. The tests were conducted on three single columns and one caisson-type foundation. The three single columns were 1.8 m in diameter,reinforced by 30-D32 longitudinal reinforcements and laterally hooped by D16 reinforcements with spacing of 20 cm. The column height is 9.54 m,10.59 m and 10.37 m for Column P2,P3,and P4,respectively. Column P2 had no exposed foundation and was subjected to pseudo-dynamic tests with peak ground acceleration of 0.32 g first,followed by one cyclic loading test. Column P3 was the benchmark specimen with exposed length of 1.2 m on its foundation. The exposed length for Column P4 was excavated to 4 m,approximately 1/3 of the foundation length,to study the effect of the scouring problem to the column performance. Both Column P3 and Column P4 were subjected to cyclic loading tests. Based on the test results,due to the large dimension of the caisson foundation and the well graded gravel soil type that provided large lateral resistance,the seismic performance among the three columns had only minor differences. Lateral push tests were also conducted on the caisson foundation at Column P5. The caisson was 12 m long and had circular cross-sections whose diameters were 5 m in the upper portion and 4 m in the lower portion. An analytical model to simulate the test results was developed in the OpenSees platform. The analytical model comprised nonlinear flexural elements as well as nonlinear soil springs. The analytical results closely followed the experimental test results. A parametric study to predict the behavior of the bridge column with different ground motions and different levels of scouring on the foundation are also discussed.
文摘This paper introduces to fluid state physics （fluid mechanics） a new interpretation of physical phenomena taking place in a fluid in motion. It introduces the base of a new theory claiming that every flow has its own internal structure of motion, which is definite organization of motion, rather than a ＂molecular chaos＂, known from the fluid statics. The paper introduces the new notion of structures vector fields of power and momentum and shows every Newtonian fluid flows are dual in character. It shows that the flow of Newtonian fluid has a dual character. It demonstrates on models and further in mathematical interpretation of physical phenomena. It introduces, on the one hand, the cycloidal motion model into the fluid mechanics, ad on the other hand an addition to the known, the classical model of Poiseuille laminar motion. The theory of dualism （double nature of physical phenomena） allows the description of selected characteristics of the flow, either by using the theory ofcycloidal motion （semicycloidal）, or by using the supplemented theory of laminar motion. The dualism theory is useful to describe each type of flows both, laminar and turbulent. This paper is only an introduction to the theory. It has been assigned number 1. It has been granted a high priority, since it contains basic concepts that will be used in others, following papers of long cycle.
基金supported,in part,by the Ministry of Education,Singapore,NUS/ARF grants R221000039133 and R221000052112
文摘To modify two-step experimental etch-and-rinse dentin adhesive with different concentrations of riboflavin and to study its effect on the bond strength,degree of conversion,along with resin infiltration within the demineralized dentin substrate,an experimental adhesive-system was modified with different concentrations of riboflavin（mlm,0,1%,3%,5%and 10%）.Dentin surfaces were etched with 37%phosphoric acid,bonded with respective adhesives,restored with restorative composite-resin,and sectioned into resin-dentin slabs and beams to be stored for 24 h or 9 months in artificial saliva.Micro-tensile bond testing was performed with scanning electron microscopy to analyse the failure of debonded beams.The degree of conversion was evaluated with Fourier transform infrared spectroscopy（FTIR） at different time points along with micro-Raman spectroscopy analysis.Data was analyzed with one-way and two-way analysis of variance followed by Tukey＇s for pair-wise comparison.Modification with 1%and 3%riboflavin increased the micro-tensile bond strength compared to the control at 24 h and 9-month storage with no significant differences in degree of conversion（P〈0.05）.The most predominant failure mode was the mixed fracture among all specimens except 10%riboflavin-modified adhesive specimens where cohesive failure was predominant.Raman analysis revealed that 1%and 3%riboflavin adhesives specimens showed relatively higher resin infiltration.The incorporation of riboflavin in the experimental two-step etch-and-rinse adhesive at 3%（mlm） improved the immediate bond strengths and bond durability after 9-month storage in artificial saliva without adversely affecting the degree of conversion of the adhesive monomers and resin infiltration.
文摘In the present work it is found that the pyrotechnic composition VS⁃2 can be initiated with flash lamps IFC⁃500 and EVIS.VS⁃2 pyrotechnic composition contains 90%of mercury(Ⅱ)5⁃hydrazinotetrazolate perchlorate and 10%of optically trans⁃parent copolymer of 2⁃methyl⁃5⁃vinyltetrazole and methacrylic acid(PVMT).We have found that the flash lamps make it possi⁃ble to initiate combustion of VS⁃2 composition with its transition to detonation both in cylindrical charges placed in brass caps of 5 mm diameter and 2 mm high,and film charges with 10 mm×80 mm in size and surface weights of 60 mg·cm^(-2)and 90 mg·cm^(-2),showing ignition delay times 10μs and 3μs,respectively.We also measured detonation velocities for VS⁃2 composition film charges,which were 4375-4505 m·s^(-1)(of the charge being surface mass 60 mg·cm^(-2))and 4221-4281 m·s^(-1)(of the charge be⁃ing surface mass 90 mg·cm^(-2))and their blasting action on the aluminum plate.The depths of the normal shock wave imprints at the charge⁃barrier interface were 0.6-0.7 mm(for surface mass of the film charges 60 mg·cm^(-2))and 1.2-1.3 mm(for surface mass of the film charges 90 mg·cm^(-2))
