Current Issue : January - March Volume : 2020 Issue Number : 1 Articles : 5 Articles
Molecular dynamics simulations of the phase transformation from bodycentered-\ncubic (bcc) to face-centered-cubic (fcc) structures were performed.\nA Morse-type function was applied, and the parameters were determined so\nthat both fcc and bcc structures were stable for the perfectcrystal model.\nWhen the fcc structure was superior to the bcc structure, the bcc model\ntransformed to fcc. Two mechanisms, based on the Bain and Nishiyama-\nWasserman (NW) relationships, were considered. Then, point or linear lattice\ndefects, i.e. , randomly scattered or regularly aligned vacancies, were introduced.\nConsequently, bcc models tended to transform to an fcc structure,\nwhereas fcc models remained stable. The transformation process was also\ninvestigated in detail. BCC-to-FCC transformation is often considered as a\nhomogeneous process based on changes in the axis lengths, and such a\nprocess was observed for the perfectcrystal model. Conversely, for the defect\nmodels, local heterogeneous deformation patterns, including cylindrical\ndomain and planar interface formation, were observed. These behaviors are\nconsidered to be related to plastic deformation during phase transformation,\nand the validity of the presented model for further investigation was confirmed....
This study aimed to investigate the static performance of notched hexagonal concrete-filled steel tube (CFST) stub columns\nthrough axial loading. Notch length, notch location, and notch direction in 14 CFST stub columns were experimentally studied.\nStress process, failure mechanism, and ultimate strength in the notched CFST columns were analyzed. Results show that notches\nin steel tubes can weaken the restraining effect of steel pipes on core concrete and induce a decrease in the ultimate strength of\nspecimens. The failure mode of components is greatly affected by notch orientation. The notch is closed under axial compression\nin the horizontally notched specimen, and the slotting indicates outward buckling in the vertically notched specimen. Based on the\ntest results, a method for calculating the ultimate strength of notched hexagonal CFST columns was established. This research\nencourages the extensive application of these structures in civil engineering....
It is important to control and predict the macroscopic properties through pore structure parameters of cement-based materials.\nMicroscopic pore structure of concrete has many characteristics, such as sizes and disordered distribution. It is necessary to use\nfractal theory to describe the pore structure of concrete. In order to establish the relationship between the pore structure\ncharacteristics of aerated concrete and porosity, shape factor, pore superficial area, average pore diameter, and average diameter,\nthe fractal dimension of the pore structure was used to evaluate the pore structure characteristics of aerated concrete. The X-ray\ncomputed tomography (CT) images of the aerated concrete block pore structure were obtained by using the XTH320 series X-ray\nthree-dimensional microscope. Thepore characteristics of aerated concrete block were studied according to Image-Pro Plus (IPP).\nBased on the research of the fractal dimension measurement methods, the proposed MATLAB program automatically determined\nthe fractal dimension of the aerated concrete block pore structure images. The research results indicated that the small pores\n(20 micromApprovimately60 microm) of aerated concrete block account for a large percentage compared with the large pores (60 micromApprovimately400 microm or more)\nfrom pore diameter distribution and the pore structure of aerated concrete block has obvious fractal features and the fractal\ndimension of aerated concrete block pore structure images were calculated to be in the range of 1.775-1.805. The pore fractal\ndimension has a strong correlation with the pore fractal characteristics of aerated concrete blocks. The fractal dimension of the\npore structure linearly increases with porosity, shape factor, and pore surface area. The fractal dimension of the pore structure\ndecreases with the average pore size and average diameter. Thus, the fractal dimension of the pore structure that is calculated by\nthe MATLAB program based on fractal theory can be assumed as the integrative evaluation index for evaluating the pore structure\ncharacteristic of aerated concrete block....
Most tunnel structures tend to have different degrees of structural damage such as leakage, concrete cracking, lining salinization,\nand falling blocks after the operation for a period. Compared with the diversity of tunnel disease detection methods, there are few\nstudies on the methods of quantifying and evaluating the main structural diseases of the lining. Based on the regular inspection\ndata of expressway tunnels in Liaoning Province, this paper summarizes the distribution characteristics and laws of existing\nstructural defects of tunnel lining. In addition, based on the in-depth study of the main structural diseases of the tunnel, the\nextenics theory is used to extract, quantify and classify several indicators that can accurately reflect the health status of the\nstructure, and then establish the corresponding matter-element model to determine the weight of each indicator and the tunnel\nstructure. The comprehensive correlation degree of disease grades is combined with the qualitative evaluation and quantitative\nresearch of lining structure diseases to construct a health evaluation system for tunnel lining structures, which is convenient for\nmanagers to make reasonable decisions. At the same time, combined with the actual test data of tunnel engineering, the calculation\nand analysis of the extension model are carried out to verify the engineering applicability of the model....
The voided biaxial concrete slab has been widely used in the engineering field. The slab has become a popular choice for designers\nand architects looking to reduce slab thickness and overall structure weight recently. Utilizing the empty space in the voided slab\nand introducing the structural control technology of mass damper into it, a new pounding tuned rotary mass damper (PTRMD) is\nproposed in this paper. This damper is designed to locate in the prefabricated hollow module to mitigate response of structure\nsubject to disastrous excitations. The damper combines the characteristics of pounding mechanisms (PMDs) and tuned rotary\nmass dampers (TRMDs). This is achieved by a ball rolling on a curved orbit and a fixed stroke-limiting plate. Thestructural control\nperformance of the PTRMD is studied numerically and verified experimentally. Specifically, first, the motion equations for a\nsingle-degree-of-freedom (SDOF) and multiple-degree-of-freedom (MDOF) system with PTRMDs are derived. Furthermore,\nnumerical results show that the PTRMD provides significant energy dissipation, and thus, is quite effective in reducing the\nstructure response. Besides, the PTRMD generally exhibits better control performance and robustness in terms of vibration\nsuppression compared with the TRMD proposed by the authors before. Finally, a shake-table test is conducted to verify the\ndamping effect of a PTRMD-controlled SDOF system. Pertinent results confirm the effectiveness and robustness of PTRMDs for\nstructural control....
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