Abstract in English:Abstract Developing fragility functions is the essential step in incorporating important uncertainties in next-generation performance-based earthquake engineering (PBEE) methodology. The present paper is aimed to involve record-to-record variability as well as modelling uncertainty sources in developing the fragility curves at the collapse limit state. In this article, in order to reduce the dispersion of uncertainties, Group Method of Data Handling (GMDH) in combination with Monte Carlo Simulation (MCS) is used to develop structural collapse fragility curve, considering effects of epistemic and aleatory uncertainties. A Steel Moment Resisting Frame (SMRF) is chosen as the tested structure. The fragility curves obtained by the proposed method which belongs to GMDH approaches are compared with those resulted from simple and well-known available methods such as First-Order Second-Moment (FOSM), Approximate Second-Order Second-Moment (ASOSM) and Monte Carlo (MC)/Response Surface Method (RSM), somehow, as an accurate method. The results of the application of the proposed approach indicate increasing accuracy and precision of the outputs as well as power with the same computational time compared to aforementioned methods. The GMDH method introduced here can be applied to the other performance levels.
Abstract in English:Abstract The numerical modelling for dynamic impact testing of end-anchored rockbolt is established in this paper. The dynamic response of rockbolt under impact loading condition is investigated considering the effects of different impact energy levels, anchoring length, bolt diameter, and material type. The results show that the stress characteristics of the anchoring section in end-anchored rockbolt could be divided into three stages with the impact time: impact initial stage, impact middle stage and impact final stage. The elongation of the rockbolt increases by about 30 mm for every 5kJ increase in impact energy. When the impact energy level increases, the energy absorption rate and maximum plastic strain both increase significantly. The impact energy is mainly dissipated by the plastic deformation of the free section and debonding section of end-anchored rockbolt. The free section plays a buffer role through its elastic deformation when the rockbolt is subjected to impact loading. It is remarkable that the energy absorption rate and anti-impact performance of the end-anchored rockbolt can be improved by increasing the bolt diameter and the bolt material strength.
Abstract in English:Abstract In this work, carbon fibre reinforced polymer (CFRP) plates have been tested under free impact vibration tests in pristine and damaged configurations. The plates were suspended as cantilevers and vibrated using an impact hammer. Two accelerometers and one microphone were used to obtain the vibration response data signals from the pristine and damaged plates, and the frequency response function (FRF) was plotted. The current technique focused on the detected signal from more than one vibration sensor to ensure the measurement's accuracy. Comparisons between the experimental vibration test and the simulated analysis using finite element analysis (FEA) showed that the results agreed. The damage orientation significantly affected the composites’ dynamic properties. The FRF measures of the damaged CFRP composites showed the lowest eigenvalues in the resonant frequencies. The 0/90 layup laminate composite exhibited greater fluctuations in resonant frequencies across the various mode shapes, which reached a 2.85% difference compared to the quasi-isotropic laminate composites.
Abstract in English:Abstract Trapezoidal laminated plates with cutouts are commonly found in many engineering field, especially in aerospace structures. In many cases these plates are subjected to various harsh environmental conditions during its service life. Thermally induced load is the one which seriously affect the buckling characteristics of the structural components. The study presents the effect of rise in temperature on the thermal buckling characteristics of trapezoidal laminated composite plates with and without cutouts by using finite element technique. In order to model the plate, a 9-noded heterosis plate element has been used by incorporating the effect of shear deformation. By correlating present findings with the available literature, the effectiveness of the present formulation is verified. The computer program FORTRAN language has been developed to investigate the effect of different parameters such as trapezoidal shapes, cutout offsets, plate aspect ratio, ply-orientations, different thickness and plate edge conditions. The influence of each parameter on the thermal buckling behavior is well investigated through this work.
Abstract in English:Abstract High-strength concrete incorporating macro-fiber combines high compressive strength of the matrix, strain-hardening, and multiple crack characteristics. Also, calcite sediment remediation bacterial techniques can enhance the mechanical properties, reduce concrete deterioration, and prevent corrosion of steel reinforcement in both the short-term and long-term. In this paper, The Bacillus subtilis bacteria at an optimum dosage of 105 cells/ml of mixing water was incorporated into M60 and M80 concrete strengthened with 0.5% macro synthetic-fiber content. The performance of 32 simply supported reinforced concrete beams with rectangular-section were evaluated numerically using ANSYS. In this study, the properties of matrix components are considered for different geometric sizes as slender and short beams with different longitudinal reinforcement ratios. The results showed that the bacterial participation in fibrous concrete beams had more significant enhancement in the initial cracking load, ultimate load, moment capacity ratio, ductility ratio, and flexural toughness compared to associated conventional concrete.
Abstract in English:Abstract A numerical study is performed on the structure-soil-structure interaction (SSSI) between high-rise buildings. ANSYS has been further developed for calculation in the frequency domain, in which hysteretic damping can be considered for both soil and structures. This study is presented in two subsequent papers. The first part focuses on the influence of the SSSI on each kind of dynamic response, while the second part, i.e., this paper, is a parameter study that focuses on the influence of each key parameter, including the separation distance between structures; the damping ratio, thickness and shear wave velocity of the soil; the length of the pile; the damping ratio, style, material stiffness, mass and story number of the superstructure; and the position and number of the structure, on the SSSI. The interaction decreases with the increase in the separation distance between structures, the increase in the damping ratio and shear wave velocity of the soil, the increase in the damping ratio and mass of the superstructure, or the decrease in the material stiffness of the superstructure in a fluctuating manner.
Abstract in English:Abstract The structure-soil-structure interaction (SSSI) between high-rise buildings is numerically investigated. ANSYS has been further developed for calculation in the frequency domain, in which hysteretic damping can be considered for both the soil and structure. This study is presented in two subsequent papers. In the first part, i.e., this paper, the variations in the story shear force, interstory drift angle, displacement, velocity and acceleration of the superstructure, the sway of the foundation, and the axial and shearing forces of the pile are presented. The major influencing factors are the excitation frequency of a harmonic wave or the frequency components of a seismic wave, shaking direction of an exciting wave and direction of the structure arrangement. Under harmonic waves, the interaction mainly occurs when the excitation frequency is 1-5 Hz. Under seismic waves, when the shaking direction of an exciting wave is perpendicular to the direction of the structure arrangement and the direction of the structure arrangement is parallel to the lateral axis of the structure, the influence on the superstructure is greatest.
Abstract in English:Abstract To improve the crashworthiness and energy absorption of thin-walled tube structures, a bionic thin-walled tube was designed based on the structural characteristics of antler osteon and the principle of structural bionics and had the same inner and outer diameters and the same gradient thickness as antler osteon. A nonlinear finite element method is used to simulate the crashworthiness of a thin-walled tube with equal gradient thickness variation (EGTTS) under axial and oblique loads. The crashworthiness of EGTTS-7 (Egtts with 7 layers) was evaluated using the complex proportional assessment(COPRAS). A multi-objective particle swarm optimization (MOPSO) algorithm was used to optimize the EGTTS-7 and the Pareto boundary was used to obtain the optimal structure parameters of the EGTTS-7 by using the loading angles of 0°, 10°, 20°, and 30°. It is found that the crashworthiness of the EGTTS is best when the axial load weight factor of the case is large. Compared with EGTTS and circular tubes(CT), F max can be reduced by up to 50.1% and EA can be increased by up to 22.7%.
Abstract in English:Abstract In the present work, the nano-Aluminum oxide (Al2O3), nano-Silicon Carbide (SiC), or a hybrid of them were infused into epoxy resin with an ultrasonic system with various weight percentage ratios of the nanoparticles. Small punch testing (SPT) and indirect tension testing were adopted to measure the tensile properties of the present nanocomposites. Pin-on-ring wear testing was also performed to examine wear performance of epoxy Al2O3 and SiC nanocomposites. The Finite Element Analysis method is introduced to simulate the indirect tension test and SPT to give a complete vision of the stress distribution in the nanocomposite specimen during the loading, and to examine its mode of failure. Good agreement between the numerical and experimental results was observed. The addition of nanoparticles from Al2O3 or SiC improves the wear resistance of epoxy. Furthermore, epoxy with nano-Al2O3 has a higher wear resistance than that with nano-SiC. The tensile strength and modulus of elasticity of epoxy are reduced by adding the Al2O3 nanoparticle. The synergistic effect is not observed in the present study.
Abstract in English:Abstract The rupture in metals can occur by cleavage, where all process is controlled by stresses, or by ductile fracture, which takes into account the damage caused by nucleation and growth of voids.The process is then dependent on stresses and strains. The Linear Elastic Fracture Mechanics, widely used in engineering practice, is based on the assumption that the first process prevails, which occurs only under certain conditions. Consideration of the second fracture process is not so well disseminated. In this work, two methodologies are considered to take into account the cleavage-ductile transition. One is based on the Tvergaard-Hutchinson's cohesive model and the other is based on the Gurson- Tvergaard-Needleman's ductile damage model. The two methodologies are considerably different and, in this work, initially the relationships between the two models are established. Then, the conditions for a transition from cleavage to ductile fracture are determined and discussed. Most of the results are presented based on crack growth resistence curves obtained for different material parameters. A strip in mode I rupture is considered firstly. It is shown that, depending on the yield stress and other factors, the two fracture modes can coexist. Also, even when only cleavage is occurring, it is affected by interactions with voids. Lastly, the present simulations are compared withCompact Tension experimental results.Results considering the coupling between the two fracture models presented a better fitting with experiments than other simulations where the coupling is not considered.