In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue ...In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue life are deduced. And then, the fatigue damage probability densities of the Miner and Chaboche-Zhao models are deduced. By virtue of laboratory fatigue test results, the fatigue damage probability density functions of the two models can be obtained, considering different stress ratios. Finally, substituting load cycles into them, the change law of cement concrete fatigue reliability about load cycles can be acquired. The results show that under the same stress ratio, with the increase in the load cycle, the fatigue reliability declines from almost 100% to 0% gradually. No matter under what stress ratio, during the initial stage of the load action, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the stable phase gradually shortens and the load cycle corresponding to the reliability of 0% also decreases. In the descent phase of reliability, the higher the stress ratio is, the lower the concrete reliability is for the same load cycle. Besides, compared with the Chaboche-Zhao fatigue damage model, the Miner fatigue damage model is safer.展开更多
A model is proposed to correlate the crack growth rate and stress ratio containing very high cycle fatigue regime.The model is verified by the experimental data in literature.Then a formula is derived for the effect o...A model is proposed to correlate the crack growth rate and stress ratio containing very high cycle fatigue regime.The model is verified by the experimental data in literature.Then a formula is derived for the effect of mean stress on fatigue strength,and it is used to estimate the fatigue strength of a bearing steel in very high cycle fatigue regime at different stress ratios.The estimated results are also compared with those by Goodman formula.展开更多
Multiaxial compression tests were performed on 100 mm×100 mm×100 mm high-strength high-performance concrete （HSI-IPC） cubes and normal strength concrete （NSC） cubes. The failure modes of specimens were p...Multiaxial compression tests were performed on 100 mm×100 mm×100 mm high-strength high-performance concrete （HSI-IPC） cubes and normal strength concrete （NSC） cubes. The failure modes of specimens were presented, the static compressive strengths in principal directions were measured, the influence of the stress ratios was analyzed. The experimental results show that the ultimate strengths for HSHPC and NSC under multiaxial compression are greater than the uniaxial compressive strengths at all stress ratios, and the multiaxial strength is dependent on the brittleness and stiffness of concrete, the stress state and the stress ratios. In addition, the Kupfer-Gersfle and Ottosen＇s failure criteria for plain HSHPC and NSC under multiaxial compressive loading were modified.展开更多
基金The National Natural Science Foundation of China(No. 51008071 )the Natural Science Foundation of Jiangsu Province(No. BK2010413)
文摘In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue life are deduced. And then, the fatigue damage probability densities of the Miner and Chaboche-Zhao models are deduced. By virtue of laboratory fatigue test results, the fatigue damage probability density functions of the two models can be obtained, considering different stress ratios. Finally, substituting load cycles into them, the change law of cement concrete fatigue reliability about load cycles can be acquired. The results show that under the same stress ratio, with the increase in the load cycle, the fatigue reliability declines from almost 100% to 0% gradually. No matter under what stress ratio, during the initial stage of the load action, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the stable phase gradually shortens and the load cycle corresponding to the reliability of 0% also decreases. In the descent phase of reliability, the higher the stress ratio is, the lower the concrete reliability is for the same load cycle. Besides, compared with the Chaboche-Zhao fatigue damage model, the Miner fatigue damage model is safer.
基金supported by the National Natural Science Foundation of China(11172304 and 11021262)the National Basic Research Program of China (2012CB937500)
文摘A model is proposed to correlate the crack growth rate and stress ratio containing very high cycle fatigue regime.The model is verified by the experimental data in literature.Then a formula is derived for the effect of mean stress on fatigue strength,and it is used to estimate the fatigue strength of a bearing steel in very high cycle fatigue regime at different stress ratios.The estimated results are also compared with those by Goodman formula.
文摘Multiaxial compression tests were performed on 100 mm×100 mm×100 mm high-strength high-performance concrete （HSI-IPC） cubes and normal strength concrete （NSC） cubes. The failure modes of specimens were presented, the static compressive strengths in principal directions were measured, the influence of the stress ratios was analyzed. The experimental results show that the ultimate strengths for HSHPC and NSC under multiaxial compression are greater than the uniaxial compressive strengths at all stress ratios, and the multiaxial strength is dependent on the brittleness and stiffness of concrete, the stress state and the stress ratios. In addition, the Kupfer-Gersfle and Ottosen＇s failure criteria for plain HSHPC and NSC under multiaxial compressive loading were modified.
