A data processing method was proposed for eliminating the end restraint in triaxial tests of soil. A digital image processing method was used to calculate the local deformations and local stresses for any region on th...A data processing method was proposed for eliminating the end restraint in triaxial tests of soil. A digital image processing method was used to calculate the local deformations and local stresses for any region on the surface of triaxial soil specimens. The principle and implementation of this digital image processing method were introduced as well as the calculation method for local mechanical properties of soil specimens. Comparisons were made between the test results calculated by the data from both the entire specimen and local regions, and it was found that the deformations were more uniform in the middle region compared with the entire specimen. In order to quantify the nonuniform characteristic of deformation, the non-uniformity coefficients of strain were defined and calculated. Traditional and end-lubricated triaxial tests were conducted under the same condition to investigate the effects of using local region data for deformation calculation on eliminating the end restraint of specimens. After the statistical analysis of all test results, it was concluded that for the tested soil specimen with the size of 39.1 mm × 80 ram, the utilization of the middle 35 mm region of traditional specimens in data processing had a better effect on eliminating end restraint compared with end lubrication. Furthermore, the local data analysis in this paper was validated through the comparisons with the test results from other researchers.展开更多
This study modeled the moving-vehicle-induced forcing excitation on a single-span prismatic bridge as a multiple frequency-multiplication harmonic load on the modal coordinates of a linear elastic simple Euler–Bernou...This study modeled the moving-vehicle-induced forcing excitation on a single-span prismatic bridge as a multiple frequency-multiplication harmonic load on the modal coordinates of a linear elastic simple Euler–Bernoulli beam,and investigated the forced modal oscillation and resonance behavior of this type of dynamic system.The forced modal responses consist of multiple frequency-multiplication steady-state harmonics and one damped mono-frequency complementary harmonic.The analysis revealed that a moving load induces high-harmonic forced resonance amplification when the moving speed is low.To verify the occurrence of high-harmonic forced resonance,numerical tests were conducted on single-span simple beams based on structural modeling using the finite element method(FEM)and a moving sprung-mass oscillator vehicle model.The forced resonance amplification characteristics of the fundamental mode for beam response estimation are presented with consideration to different end restraint conditions.The results reveal that the high-harmonic forced resonance may be significant for the investigated beams subjected to vehicle loads moving at specific low speeds.For the investigated single-span simple beams,the moving vehicle carriage heaving oscillation modulates the beam modal frequency,but does not induce notable variation of the modal oscillation harmonic structure for the cases that vehicle of small mass moves in low speed.展开更多
基金Supported by Major State Basic Research Development Program of China("973" Program,No.2010CB731502)
文摘A data processing method was proposed for eliminating the end restraint in triaxial tests of soil. A digital image processing method was used to calculate the local deformations and local stresses for any region on the surface of triaxial soil specimens. The principle and implementation of this digital image processing method were introduced as well as the calculation method for local mechanical properties of soil specimens. Comparisons were made between the test results calculated by the data from both the entire specimen and local regions, and it was found that the deformations were more uniform in the middle region compared with the entire specimen. In order to quantify the nonuniform characteristic of deformation, the non-uniformity coefficients of strain were defined and calculated. Traditional and end-lubricated triaxial tests were conducted under the same condition to investigate the effects of using local region data for deformation calculation on eliminating the end restraint of specimens. After the statistical analysis of all test results, it was concluded that for the tested soil specimen with the size of 39.1 mm × 80 ram, the utilization of the middle 35 mm region of traditional specimens in data processing had a better effect on eliminating end restraint compared with end lubrication. Furthermore, the local data analysis in this paper was validated through the comparisons with the test results from other researchers.
基金supported by the SLDRCE Independent Research Fund of the Ministry of Science and Technology of China(Nos.SLDRCE14-B-24 and SLDRCE19-B-33).
文摘This study modeled the moving-vehicle-induced forcing excitation on a single-span prismatic bridge as a multiple frequency-multiplication harmonic load on the modal coordinates of a linear elastic simple Euler–Bernoulli beam,and investigated the forced modal oscillation and resonance behavior of this type of dynamic system.The forced modal responses consist of multiple frequency-multiplication steady-state harmonics and one damped mono-frequency complementary harmonic.The analysis revealed that a moving load induces high-harmonic forced resonance amplification when the moving speed is low.To verify the occurrence of high-harmonic forced resonance,numerical tests were conducted on single-span simple beams based on structural modeling using the finite element method(FEM)and a moving sprung-mass oscillator vehicle model.The forced resonance amplification characteristics of the fundamental mode for beam response estimation are presented with consideration to different end restraint conditions.The results reveal that the high-harmonic forced resonance may be significant for the investigated beams subjected to vehicle loads moving at specific low speeds.For the investigated single-span simple beams,the moving vehicle carriage heaving oscillation modulates the beam modal frequency,but does not induce notable variation of the modal oscillation harmonic structure for the cases that vehicle of small mass moves in low speed.
