Current Issue : July - September Volume : 2019 Issue Number : 3 Articles : 5 Articles
The current experimental study presents the results of bond strength loss (steel bar concrete) due to the corrosion damage of steel\nbar specimens, semiembedded in concrete, at various times of exposure to corrosive environment. In this case, a correlation was\nmade between the width of the surface cracks of concrete caused by reinforcing steel corrosion and bond strength for different\ndistances between stirrups and different cover thickness of concrete. The study indicates close relationship between the width of\nsurface cracking, the percentage mass loss of embedded reinforcing bar, the distance between stirrups, and the cover thickness. In\naddition, mathematical predictive models of bond strength loss of corroded specimens were proposed. The model outcomes\nshowed that the cracking development on concrete surface up to a width of 1.6mmis accompanied by an exponential reduction of\nbond strength loss between steel reinforcement and concrete. Furthermore, the investigation has shown that the increase of\ntransverse reinforcement (stirrups) percentage and the cover thickness play a significant role in durability of reinforced concrete\nelements and in bond strength maintenance between rebar and concrete....
Recent advances in concrete recycling technology focus on novel fragmentation techniques\nto obtain aggregate fractions with low cement matrix content. This study assesses the aggregate\nliberation effectiveness of four different treatment processes including standard and innovative\nconcrete fragmentation techniques. Lab-made concrete samples were subjected to either standard\nmechanical crushing technique (SMT) or electrodynamic fragmentation (EDF). For both fragmentation\nprocesses, the influence of a microwave weakening pre-treatment technique (MWT) was investigated.\nA detailed analysis of the particle size distribution was carried out on samples after fragmentation............................
Three-dimensional finite element method analysis on the tunnel-soil-underground pipeline was carried out based on the\nABAQUS program. PSI element was applied to simulate the interaction between the pipelines and soil. Parameters such as an\nelastic modulus of soil, stress release rate, at-rest lateral pressure coefficients, an elastic modulus of pipelines, and buried\ndepths of tunnels were analyzed. The effects of tunnel excavation on the displacement of existing pipelines were investigated,\nand the settlement relationships were obtained. The relationship between each parameter and surface settlement was determined\nby the grey relational analysis method to analyze each parameterâ??s sensitivity to the settlement of the pipeline, which\ncan provide a reference for emphasis and methods of shield tunneling support. Finally, a formula of the settlement relationship\nbetween the maximum surface settlement and pipelines deformation was proposed for different pipe-soil relative stiffness. The\nformula was applied in the practical case. Compared with the field monitoring results and FEM computer results, it has been\nfound that the proposed normalized formula is consistent with the measured results and numerical simulation of the\npipeline settlement....
Based on the low cyclic loading test results of vertical stiffener joints between concrete-filled double steel tubular (CFDST)\ncolumns and steel beams, the shear transfer mechanism and shear resistance were analyzed in this paper. A conceptual model\nformulated was presented in terms of equilibrium and stress-strain relationships. The results calculated by the theoretical model\nand the available experimental data were compared, and then one new concept of shear storage coefficient was proposed for the\ndetermination of the shear storage capacity of the joint, which quantitatively explained the ductility failure progression of the joint\nspecimens in the seismic performance test. It was concluded that the vertical stiffener joint had sufficient shear resistance, which\nmet the seismic design principle of strong shear and weak bending. Results show that the ribbed joints have greater shear\nresistance than unribbed ones; lengthening the overhang of the vertical stiffener can both increase shear resistance and shear\nstorage capacity of the joint; axial compression ratio can reduce the shear storage capacity. The paper also suggests that the joint\ndesign should ensure enough safety storage of shear resistance to improve the seismic performance....
This paper proposes a tension-compression damage model for concrete materials, formulated within the framework of thermodynamics\nof irreversible processes. The aim of this work is to solve the following problems: the premature divergence of\nnumerical solutions under general loading conditions due to the conflict of tensile and compressive damage bounding surfaces,\nwhich is a result of the application of the spectral decomposition method to distinguish tension and compression, and the\nunsatisfactory reproduction of distinct tension-compression behaviors of concrete by strain-driven damage models. The former is\nsolved by the sign of the volumetric deformation, while the latter is solved via two separated dissipation mechanisms. Moreover, of\nspecific interest is an improved solution to the problem of mesh-size dependency using consistent crack bandwidths, which takes\ninto account situations with irregular meshes and arbitrary crack directions in the context of the crack band approach. The\nperformance of the model is validated by the well-documented experimental data.The simplicity and the explicit integration of the\nconstitutive equations render the model well suitable for large-scale computations....
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