A theoretical prediction method based on the change of concrete material is proposed to evaluate the ultimate bending moment of concrete beams which have undergone freeze-thaw cycles （PTCs）. First, the freeze-thaw d...A theoretical prediction method based on the change of concrete material is proposed to evaluate the ultimate bending moment of concrete beams which have undergone freeze-thaw cycles （PTCs）. First, the freeze-thaw damage on concrete material is analyzed and the residual compressive strength is chosen to indicate the freeze-thaw damage. Then, the equivalent block method is employed to simplify the compressive stress-strain curve of the freeze-thaw damaged concrete and the mathematical expression for the ultimate bending moment is obtained. Comparisons of the predicted results with the test data indicate that the ultimate bending moment of concrete beams affected by FTC attack can be predicted by this proposed method. However, the bond-slip behavior and the randomness of freeze-thaw damage will affect the accuracy of the predicted results, especially when the residual compressive strength is less than 50%.展开更多
The basic goal of this paper is to point out the importance of design shaping as well as the key parameter of the great interaction between the structure and natural environment. However, experiences confirm the fact ...The basic goal of this paper is to point out the importance of design shaping as well as the key parameter of the great interaction between the structure and natural environment. However, experiences confirm the fact that the most successful structures, the bridges also, have not got that attribute because of their grandiosity but per their great integration in the nature that is environment. Beside the basic function, that is the usage to man, their integrations in the environment greately enrich the ambience. The old stone bridges are mostly well integrated in the natural environment. In the period of large building, it did not take care of the parameters （the bridges of steel, concrete and prestressed concrete）, but great attention was paid to records referring to spans and complicated forms. The author thinks it is necessary to take care about integration of all building structures in the environment, especially bridges. As a good example of successful creation, simplicity of form, and especially good integration in the natural surroundings are three bridges from Montenegro, one of them is old stone bridge, others are reinforced-concrete and steel bridges.展开更多
In this paper,the Fourier spectrum-based strain energy damage detection method for beam-like structures is proposed based on the discrete Fourier transform.The classical strain energy damage detection method localizes...In this paper,the Fourier spectrum-based strain energy damage detection method for beam-like structures is proposed based on the discrete Fourier transform.The classical strain energy damage detection method localizes damage by the comparison of the strain energy between the intact and inspected structures.The evaluation of the 2nd-order derivative term in the strain energy plays a crucial part in the comparison.The classical methods are mostly based on a numerical derivative estimation for this term.The numerical derivative,however,introduces additional disturbances into damage indications.To address this problem,a discrete Fourier transform-based strain energy is proposed with the emphasis of enhancing the performance in noisy condition.The validations conducted on the simulated and experimental data show that the developed method is effective enough for composite beam damage detection in noisy environments.展开更多
基金The National Natural Science Foundation of China(No.5097822451378104)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘A theoretical prediction method based on the change of concrete material is proposed to evaluate the ultimate bending moment of concrete beams which have undergone freeze-thaw cycles （PTCs）. First, the freeze-thaw damage on concrete material is analyzed and the residual compressive strength is chosen to indicate the freeze-thaw damage. Then, the equivalent block method is employed to simplify the compressive stress-strain curve of the freeze-thaw damaged concrete and the mathematical expression for the ultimate bending moment is obtained. Comparisons of the predicted results with the test data indicate that the ultimate bending moment of concrete beams affected by FTC attack can be predicted by this proposed method. However, the bond-slip behavior and the randomness of freeze-thaw damage will affect the accuracy of the predicted results, especially when the residual compressive strength is less than 50%.
文摘The basic goal of this paper is to point out the importance of design shaping as well as the key parameter of the great interaction between the structure and natural environment. However, experiences confirm the fact that the most successful structures, the bridges also, have not got that attribute because of their grandiosity but per their great integration in the nature that is environment. Beside the basic function, that is the usage to man, their integrations in the environment greately enrich the ambience. The old stone bridges are mostly well integrated in the natural environment. In the period of large building, it did not take care of the parameters （the bridges of steel, concrete and prestressed concrete）, but great attention was paid to records referring to spans and complicated forms. The author thinks it is necessary to take care about integration of all building structures in the environment, especially bridges. As a good example of successful creation, simplicity of form, and especially good integration in the natural surroundings are three bridges from Montenegro, one of them is old stone bridge, others are reinforced-concrete and steel bridges.
基金supported by the National Natural Science Foundation of China(Grant Nos.51405369&51421004)the National Key Basic Research Program of China(Grant No.2015CB057400)+1 种基金the National Natural Science Foundation of Shaanxi Province(Grant No.2016JQ5049)the Postdoctoral Science Foundation of Shaanxi Province
文摘In this paper,the Fourier spectrum-based strain energy damage detection method for beam-like structures is proposed based on the discrete Fourier transform.The classical strain energy damage detection method localizes damage by the comparison of the strain energy between the intact and inspected structures.The evaluation of the 2nd-order derivative term in the strain energy plays a crucial part in the comparison.The classical methods are mostly based on a numerical derivative estimation for this term.The numerical derivative,however,introduces additional disturbances into damage indications.To address this problem,a discrete Fourier transform-based strain energy is proposed with the emphasis of enhancing the performance in noisy condition.The validations conducted on the simulated and experimental data show that the developed method is effective enough for composite beam damage detection in noisy environments.
