Analytical Models of Concrete Fatigue:A State-of-the-Art Review

Fatigue failure phenomena of the concrete structures under long-term low amplitude loading have attractedmore attention.Some structures,such as wind power towers,offshore platforms,and high-speed railways,may resist millions of cycles loading during their intended lives.Over the past century,analytical methods for concrete fatigue are emerging.It is concluded that models for the concrete fatigue calculation can fall into four categories:the empirical model relying on fatigue tests,fatigue crack growth model in fracture mechanics,fatigue damage evolution model based on damage mechanics and advanced machine learning model.In this paper,a detailed review of fatigue computing methodology for concrete is presented,and the characteristics of different types of fatigue models have been stated and discussed.

Damage Assessment of Reinforced Concrete Structures through Damage Indices:A State-of-the-Art Review

Due to the developments of computer science and technology in recent years,computer models and numerical simulations for large and complicated structures can be done.Among the vast information and results obtained from the analysis and simulations,the damage performance is of great importance since this damage might cause enormous losses for society and humanity,notably in cases of severe damage occurring.One of the most effective tools to handle the results about the damage performance of the structure is the damage index(DI)together with the damage states,which are used to correlate the damage indices with the damage that occurred in the actual structures.Numbers of damage indices proposed and developed rely on the fact that the damage causes noticeable changes in the structural and dynamic properties of the structural components or the whole structure.Therefore,this study presents a comprehensive review of the damage assessment of Reinforced Concrete(RC)structures.It presents step by step the development of the damage indices that are most widely used to estimate the performance of structural components in the structure and subsequently assess the damage degree of such these structures either based on the structural properties or dynamic properties of the structure.Also,several damage states have been introduced to estimate the performance level of the structure.Finally,case studies,methodologies,and applications on the damage assessment of RC structures are reviewed and presented.

Centrifuge Model Tests and Numerical Simulations of the Impact of Underwater Explosion on an Air-Backed Steel Plate

Damage and threats to hydraulic and submarine structures by underwater explosions(UNDEXs)have raised much attention.The centrifuge model test,compared to prototype test,is a more promising way to examine the problem while reducing cost and satisfying the similitude requirements of both Mach and Froude numbers simultaneously.This study used a systematic approach employing centrifuge model tests and numerical simulations to investigate the effects of UNDEXs on an air-backed steel plate.Nineteen methodical centrifuge tests of UNDEXs were conducted.The shock wave pressure,bubble oscillation pressure,acceleration and the strain of the air-backed steel plate were recorded and compared with numerical studies using the finite element analysis(FEA)commercial software ABAQUS.By implementing empirically derived and physically measured pressures into the numerical models,the effects of the shock wave and bubble oscillation on the steel plate were investigated.Generally,the numerical results were in agreement with the experimental results.These results showed that the peak pressure of an UNDEX has a significant effect on the peak acceleration of the steel plate and that the impulse of the UNDEX pressure governs the peak strain of the steel plate.

Introduction to the Special Issue Numerical Modeling and Simulation for Structural Safety and Disaster Mitigation

Natural disasters including earthquake,hurricane,tsunami,flood and wildfire,cause enormous loss of lives and properties for human society every year.The structures and infra-structures are built to protect the mankind from natural disasters,but their damage and failure sometimes become part of the disasters.Therefore,the structural safety and disaster mitigation have become timely research topics for safeguarding our society.

Centrifuge experiment and numerical analysis of an air-backed plate subjected to underwater shock loading

In this study,systematic centrifuge experiments and numerical studies are conducted to investigate the effect of shock loads due to an underwater explosion on the dynamic responses of an air-backed steel plate.Numerical simulations with three different models of pressure time history generated by underwater explosion were carried out.The first model of pressure time history was measured in test.The second model to predict the time history of shock wave pressure from an underwater explosion was created by Cole in 1948.Coefficients of Cole's formulas are determined experimentally.The third model was developed by Zamyshlyaev and Yakovlev in 1973.All of them are implemented into the numerical model to calculate the shock responses of the plate.Simulated peak strains obtained from the three models are compared with the experimental results,yielding average relative differences of 21.39%,45.73%,and 13.92%,respectively.The Russell error technique is used to quantitatively analyze the correlation between the numerical and experimental results.Quantitative analysis shows that the simulated strains for most measurement points on the steel plate are acceptable.By changing the scaled distances,different shock impulses were obtained and exerted on the steel plate.Systematic numerical studies are performed to investigate the effect of the accumulated shock impulse on the peak strains.The numerical and experimental results suggest that the peak strains are strongly dependent on the accumulated shock impulse.