جستجوی مقالات مرتبط با کلیدواژه « abaqus » در نشریات گروه « مواد و متالورژی »

This paper aims to numerically investigate the structural behavior of reinforced high-strength concrete (HSC) beams retrofitted by Carbon Fiber Reinforced Polymer (CFRP) sheets after cracking. Six pre-cracked HSC beams retrofitted with CFRP sheets having identical reinforcement are numerically tested by four-point loading until failure using Abaqus software, besides two others without CFRP as control beams. CFRP sheets are attached on three beam sides in the shear span after cracking under 60 % of loading. Two shear span distances, two inclinations of CFRP sheets, and the number of sheets are adopted as parameters to compare with the experimental results obtained previously. Test results are matched with the practical findings to calibrate the Abaqus parameters. The results show that retrofitting the cracked beam by CFRP raised its tolerance to the applied load by a range of (13-36) % depending on the shear span to depth ratio and the arrangement of CFRP sheets. When the beam tends to fail in shear, the effect of CFRP is more pronounced than when it tends to fracture in flexure. The inclined sheets are more effective than the vertical ones. Furthermore, two additional parameters are regarded to clarify their effects on the behavior of retrofitted beams: sheet width and concrete compressive strength. Altering the CFRP width does not affect the tolerance, whereas increasing concrete compressive strength raises the beam loading.

This study aimed to determine the effect of various influencing parameters such as tunnel diameter (D), depth (H), width (B), length (L), number of floors, and the horizontal distance of the building from the tunnel axis (X), as well as soil properties such as internal friction angle (ϕ), Poisson ratio (υ), modulus of elasticity (E), and cohesion (C) on surface settlement using ABAQUS. According to the results, the settelment increases with increasing tunnel diameter at a constant depth, while it decreases with increasing tunnel depth. Changes in the width and length of the building also affect the settlement directly; consequently, as the width and length of the building increase due to increasing the cross-sectional area of the building and its rigidity and stiffness, the settlement of the foundation becomes more uniform and resistant to displacement, leading to a decrease in the surface settlement. Also, as the distance of the building from the tunnel axis increases, the settlement decreases and follows a constant trend after a distance equal to the tunnel diameter. Based on the results of the sensitivity analysis, the depth of the tunnel has the greatest effect on the surface settlement, which can be prevented by controlling the depth of the tunnel from the ground surface. Also, among the soil geomechanical parameters, the modulus of elasticity had the greatest effect on settlement in the present study. Finally, according to the results, the effect of tunnel, building, and soil properties on surface settlement is very important, particularly in urban environments.

In Iran, using the hand excavated pits (wells) have been more common compared to other countries. As a matter of fact, recent years, utilizing the dynamic probing test (DPT) in these types of pits has been significantly developed in Iran. This is while the standard state of doing this test is from the ground level. In this work, the dynamic probing test is carried out in two similar wells with diameter of 1 m and the depth of 10 m in two areas in city of Qom in Iran; one has silty sand soil and the other is clay. Then, both tests are simulated using numerical modeling in Abaqus software and the results are compared and calibrated with the values obtained at the mentioned sites. The results show a good agreement between the simulation data and tests done in the sites. After calibrating the simulated values with the values obtained from the site, we perform another simulation, this time, for the standard state (It means that the test is done from the ground level or with the assumption without well), as deep as 10 m and for both areas and with the mentioned soils specifications. The results show 35 and 22 percent difference in the dynamic resistance of cone’s tip between the testing in standard state and hand excavated pit, for silty sand and clay soils, respectively. Finally, using the simulation, we present the relations between the depth of the test point and dynamic resistance of cone’s tip for both states and both types of the soils studied in this paper.

In the current paper, the results of a numerical simulation that were verified by a well instrumented experimental procedure for studying the arching effect over a trapdoor in sand is presented. To simulate this phenomenon with continuum mechanics, the experimental procedure is modeled in ABAQUS code using stress dependent hardening in elastic state and plastic strain dependent frictional hardening-softening with Mohr Coulomb failure criterion applying user sub-routine. The apparatus comprises of concentric circular trapdoors with different diameters that can yield downward while stresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole soil mass deforms elastically. However, after an immediate specified displacement, depending on the diameter of the trapdoor, the soil mass behaves plastically. This behavior of sand occurs due to the flow phenomenon and continues until the stress on trapdoor is minimized. Then the failure process develops in sand and the measured stress on the trapdoor shows an ascending trend. This indicates gradual separation of the yielding mass from the whole soil body. Finally, the flow process leads to establish a stable vault of sand called arching mechanism or progressive collapse of the soil body.