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This paper investigates the influence of heterogeneity on mechanical and acoustic emission (AE) behaviours of stratified rock specimens under uniaxial compression using a digital image processing (DIP)-based finite difference method (FDM). In the DIP, a developed image segmentation algorithm based on seeded region growing (SRG) is proposed to fully acquire the mesostructure of stratified rock specimens, instead of the traditional threshold value method. To sufficiently capture the heterogeneity of stratified rock, Weibull statistical manner is adopted to describe mechanical properties of each material component. Three schemes are adopted to study the effect of heterogeneity with different homogeneity index and different mesostructure under two compression loading conditions. The results show that heterogeneity has a great influence on the mechanical and AE behaviours of stratified rock. As the homogeneity of material components increases, the peak strength and brittleness of rocks increase, and the macro elastic modulus improves as well. Simultaneously, the AE modes change from swarm shock to main shock. Under the same component content, the macro-property is better while the component distribution is concentrative relatively, especially to the property of strength. For the coupling effect of mesostructure and heterogeneity arising from material components, mesostructure is considered to cause the visible increase of AE counts. And the numerical results agree well with the previously numerical results and experimental data. [ABSTRACT FROM AUTHOR]

Interval analysis is a new uncertainty analysis method for engineering structures. In this paper, a new sensitivity analysis method is presented by introducing interval analysis which can expand applications of the interval analysis method. The interval analysis process of sensitivity factor matrix of soil parameters is given. A method of parameter intervals and decision-making target intervals is given according to the interval analysis method. With FEM, secondary developments are done for Marc and the Duncan-Chang nonlinear elastic model. Mutual transfer between FORTRAN and Marc is implemented. With practial examples, rationality and feasibility are validated. Comparison is made with some published results. [ABSTRACT FROM AUTHOR]

Many high-piled wharves were built in the last century, and some wharf members have been damaged over decades of operation. It is important to use effective means to evaluate the safety status and durability of these high-piled wharf structures and guide reinforcement efforts. At present, the most common safety status evaluation methods for high-piled wharves are site inspections, crack detection, and concrete strength tests. However, it is difficult to provide quantitative safety indicators using these methods. In this paper, a disturbing-energy method is proposed for the safety assessment of high-piled wharves based on the variational principle and minimum potential energy principle. The geometric nonlinear effect is introduced, and formulations are derived for calculating the disturbing energy. A concentric compression bar example is presented to validate the proposed method through a comparison analysis between the Euler method and disturbing-energy method. Through several cases involving different loads applied to the same high-piled wharf structure, the same load applied to different structures, overall stiffness degradation, and member damage, the disturbing-energy method is shown to reflect very well the safety condition or damage condition of the high-piled wharf structure. The disturbing-energy method can also be used to identify the failure path of the structure and optimize the form of the wharf structure. [ABSTRACT FROM AUTHOR]

Some reinforced concrete structures are subjected to repeated loads during their service lives, and the effect of repeated loads is stronger and more complex than static loads. This paper reports the results of the tests performed on cylindrical reinforced concrete specimens under uniaxial repeated loads. The effect of structural parameters (e.g., stirrup configuration, bond length, confinement method, and concrete cover) and loading parameters (e.g., amplitude, peak load, loading rate, and initial load cycles) on the bond properties of the reinforced concrete under repeated loads was studied in detail. In addition, the degradation mechanisms and failure modes of the specimens' bond stress were analyzed. It is found that the use of stirrups, increase of bond length, and concrete cover, as well as confinement can effectively curb the widening and expansion of cracks in concrete and significantly improve ductility and repeated load bearing capability. As the rigidity of confinement material increased, the enhancement effect of confinement on bond stress increases. Compared to the role of confinement (e.g., carbon fiber reinforced polymer), increasing the concrete cover can more effectively improve the bond stress. The rebar's subsequent residual bond stress declines as the number of early-stage load cycle increases. [ABSTRACT FROM AUTHOR]