Showing 14 results for Shear
S. M. Haeri, N. Sadati and R. Mahin-Rousta,
Volume 20, Issue 2 (4-2001)
Abstract
In this research, behaviour of clayey soils under triaxial loading is studied using Neural Network. The models have been prepared to predict the stress-strain behaviour of remolded clays under undrained condition. The advantage of the model developed is that simple parameters such as physical characteristics of soils like water content, fine content, Atterberg limits and so on, are used to model the stress-strain behaviour of clays under triaxial loading, without performing exact and time-consuming tests on samples.
Results from the network show that neural network is a good tool for prediction of stress-strain behaviour of clayey soils using simple physical characteristics of such soils
D. Mostofinejad and M.davoodnabi,
Volume 21, Issue 1 (7-2002)
Abstract
In most cases, structural engineers assume a concrete floor to be a rigid diaphragm. Although this simplification is in most cases acceptable, it should be noted that such an assumption may be distrusted due to certain problems. Concrete structures with staggered shear walls are among those whose analysis should be conducted with special concern for the behavior of their floor diaphragms. However, in the structures with staggered shear walls, the horizontal shear due to lateral loads is transmitted to the lower stories through the floor diaphragm since the walls are not usually located over each other in consecutive stories. Therefore, the rigidity of the floor diaphragm is of great importance. In the present study, a parametric analysis was performed to investigate the effect of the rigidity of the floor diaphragm on the load-carrying procedure of the structures with staggered shear walls. The investigated parameters were the number of stories, the ratio of length to width of the plan, and the thickness of walls and diaphragms. Furthermore, the study was carried out for both rectangular and I-shaped plans. All analyses were dynamically performed by ANSYS 5.4 using acceleration spectrum recommended by Iranian Building Code Standard No. 2800. Finally, the behavior of these structures and comparison of the frequencies, the maximum lateral displacements and the shear in the walls and columns as the responses of rigid and flexible diaphragms were highlighted and outlined.
Keywords: Reinforced concrete, staggered shear wall, load carrying, floor diaphragm, rigidity.
M. R. Banan and A. Fouladi,
Volume 22, Issue 1 (7-2003)
Abstract
This paper presents a new super-element with twelve degrees of freedom for latticed columns. This elements is developed such that it behaves, with an acceptable approximation, in the same manner as a reference model does. The reference model is constructed by using many Solid elements. The cross section area, moments of inertia, shear coefficient and torsoinal rigidity of the developed new element are derived. Since the reference model has a large number of degrees of freedom (especially for nonlinear cases), computation of the equivalent essential parameters of the proposed element is very time consuming, so, a model using only beam elements is also presented. For the super element, a general purpose program is developed that is capable of performing linear and nonlinear analysis of 3D-frames with latticed columns. In order to derive the essential parameters of the proposed super-element, many latticed columns are analyzed while shear deformations are taken into consideration. Using these essential equivalent parameters approximate relations are proposed for the compution of parameters of any latticed column based on geometric characteristics. Finally, to show the accuracy of the proposed element, several examples are presented.
Keywords: Finite elements, Super-element, Latticed column, Shear deformations, 3D-frames
A. Shirvani and M. Farzin,
Volume 22, Issue 1 (7-2003)
Abstract
In this paper, shear localization due to strain softening in sidepressed cylinders, is inverstigated. Shear localization causes formation of macroscopic shear bands which can be obsserved in the metallographic cross-section. In this paper, for the first time a method is presented in which a simple two-slice model is used to study the formation of shear bands. The results obtained form this model are in perfect agreement with the results obtatained form experimental works for and micrcrostructures in Ti-6242Si alloy.
Keywords: shear Localiation, shear Bands, Two –Slice Model, Titanium Alloy Ti-6242Si
M. Kahrom, K. Alavie and M. M. Jafariean,
Volume 24, Issue 1 (7-2005)
Abstract
Neutral stability limits for wake flow behind a flat plate is studied using spectral method. First, Orr-Sommerfeld equation was changed to matrix form, covering the whole domain of solution. Next, each term of matrix was expanded using Chebyshev expansion series, a series very much equivalent to the Fourier cosine series. A group of functions and conditions are applied to start and end points in the mathematical domain of the solution so as to avoid error accomulation at these points. The scheme ends with two matrices which result from the Orr-Sommerfeld equation. These matrices are solved, in conjunction,
with boundary conditions ending up with a curve of neutral points of stability for an assumed velocity profile. Results are compared with other existing numerical methods and experiments, and the accuracy of the method is confirmed.
M.a.rowshanzamir and A. Jafari,
Volume 24, Issue 2 (1-2006)
Abstract
Cohesive-frictional soils are widely used in the construction of embankment structures and due to the method of construction, i.e. applying compactive efforts in the vertical direction in these cases, the occurrence of anisotropy in the soil strength and permeability seems to be inevitable. In this study, attempts have been made to evaluate the shear strength of c-f soils through modifying a large shear box apparatus. Conducting more than 108 direct shear tests, the effects of compaction method and moisture on the shear strength anisotropy of a selected c-f soil (a clayey sand) have then been
investigated. According to the test results, firstly strength anisotropy was observed in all the soil specimens and the shear strength in the vertical direction was about 14% to 21% higher than that in the horizontal direction. Secondly, it was found that an increase in the compaction moisture led to an increase in the degree of anisotropy. Furthermore, the anisotropy in the cohesive strength was more pronounced in the specimens with a moisture content higher than the optimum one. The highest degree of anisotropy was observed in the specimens compacted by impacting effort and the lowest one belonged to those with the vibratory compaction.
H. R. Sheibani and H. Bayyat,
Volume 26, Issue 1 (7-2007)
Abstract
A physical model of gabion overflow dams was studied to determine the velocity profile and Reynolds shear stress. Physical tests were done under two different conditions of dam crest, overflow dams with impermeable and with permeable crests. Instantaneous velocity components over dam crest were measured by an ADV (Acoustic Doppler Velocimeter) instrument. This instrument is capable of measuring instantaneous velocity components with frequencies up to 25 Hz. Average velocity components and bed shear stress were extracted from ADV measurements. The results of this research show the effect of crest permeability on velocity and Reynolds shear stress. The magnitude of Reynolds shear stresses, horizontal velocity components, and absolute value of vertical velocity components under the permeable scenario are bigger than those of the impermeable scenario. Velocity distribution over the dam crest is different from the universal logarithmic profile.
D. Mostofinejad and M. Noormohamadi,
Volume 27, Issue 2 (1-2009)
Abstract
Although studies on RC beams under shear have a history record of more than 100 years, many important
issues in this context still remain that have evaded attention. The aim of the current study is to study a number of these less investigated aspects of the behavior of RC beams under shear. For this purpose, and based on the modified compression field theory, a computer program has been written to study the effects of transverse and longitudinal steel reinforcement and shear span, a/d, on the behavior of RC beams under shear. The results show that the shear capacity of the beam cannot be increased beyond an optimum amount of transverse steel ratio. This paper will try to provide a precise definition of this optimum transverse steel ratio. Another finding of the present study is that increasing tensile longitudinal steel ratio increases the amount of the optimum transverse steel ratio, while increasing a/d decreases the optimum transverse steel ratio.
G. Ghodrati Amir, A. Zare Hosseinzadeh,
Volume 34, Issue 1 (7-2015)
Abstract
In this paper, a new vibration-based damage detection method for damage localization in shear frames is presented. For this purpose, a new damage index is proposed by means of static displacements estimated using only the first several mode data and Grey Relation Theory. The efficiency of the presented method has been demonstrated through studying several damage scenarios on three examples of shear frames with a different number of stories. The effects of various situations such as the existence random noises in the recorded data, number of available modes, different damage scenarios and irregularity in the structural characteristics have been studied on the applicability of the presented method. The obtained results show the robustness and good performance of the presented method in the damage diagnosis of shear frames. Some of the most important advantages of the suggested method can be summarized as its ability in damage localization by means of only the first mode data, low sensitivity to the random noises, and high speed and accuracy in estimating damage locations.
K. Tourani, . R. Mahboubi, E. Seyedi Hosseininia,
Volume 35, Issue 1 (9-2016)
Abstract
Although a significant portion of conditions encountered in geotechnical engineering, for investigating engineering behavior of soil, involves unsaturated soils; the traditional analysis and design approach has been to assume the limiting conditions of soils being either completely dry or completely saturated. In unsaturated soils the capillary force produce attractive forces between particles. Discrete Element Method (DEM) is an appropriate tool to consider the capillary effects. The calculations performed in DEM is based on iterative application of Newton’s second law to the particles and force-displacement law at the contacts. In the present study, the behavior of unsaturated soils in pendular regime is simulated utilizing DEM. Triaxial compression tests were modeled as two-dimensional, considering capillary force effects. Finally, capillary effects on Macro parameters of a simulated granular soil (stress, axial strain, volumetric strain and void ratio) and Mohr Coulomb failure criteria parameters were studied.
H. Tanzadeh, H. Amoushahi,
Volume 37, Issue 1 (9-2018)
Abstract
A semi-analytical finite strip method was developed for the buckling analysis of laminated composite plates based on zigzag and third order shear deformation theories. The displacement functions of the plates were evaluated using a continuous harmonic function series in the longitudinal direction that satisfied the simply supported boundary conditions and a piecewise interpolation polynomial in the transverse direction. By considering the displacement-strain relations and strain-stress relations, the standard and geometric matrices were evaluated using the virtual work principle. The numerical results related to the buckling of single-layer and multi-layer plates were presented based on two different plate theories. The effects of different boundary conditions, length to thickness ratio, fiber orientation and modulus of elasticity were also investigated through numerical examples.
S. M. Seyed Sharafy, S. Hatami,
Volume 37, Issue 2 (3-2019)
Abstract
Diagonal Strap bracing is one of the most applicable lateral bracing systems in light steel framing (LSF). In practice, one or more panels of Gypsum Wall Boards (GWBs) is used for the cladding of strap braced frames. Usually, the effect of these GWBs in modelling and design is neglected by designers, but this effect can affect the seismic performance of the system In this paper, firstly, a simple numerical method is developed to model the monotonic and cyclic behavior of cold-formed strap braced shear walls together with GWBs. Then, the effects of GWB on the lateral characteristics and seismic performance levels of shear walls are evaluated. It is found that neglecting GWB in the lateral design or modeling of LSF is not rational and GWB can increase the dissipation of earthquake energy, lateral strength and stiffness of the walls. Also, the shear wall composed of strap bracing and SWBs reaches a certain performance level in a less drift ratio in comparison to to only strap braced system
R. Keshavarzi, Sh. Hatami, Sh. Hashemi,
Volume 39, Issue 2 (2-2021)
Abstract
Plates made of laminated composite materials with variable stiffness can have wide applications in various branches of engineering due to such advantages as high strength /stiffness to weight ratio. In these composites, curved fibers are used to reinforce each lamina instead of the straight fibers. In this paper, the application of finite strip method for the buckling analysis of moderately thick composite plates with variable stiffness is investigated. For buckling analysis, a semi-analytical finite strip method based on the first-order shear deformation theory is employed. In this method, all displacements are presumed by the appropriate harmonic shape functions in the longitudinal direction and polynomial interpolation functions in the transverse direction. The minimum potential energy method has been used to develop the stability formulations. This analysis examines the effect of using curved fibers instead of straight fibers on the laminate composites. The critical loads obtained from this analysis are compared with those of other researchers and the efficiency and accuracy of the developed finite strip method are confirmed. Comparison of the analysis results of these plates shows that changing the slope of the fibers can lead to a significant change in the buckling response. Also, increasing the number of the terms of shape functions in the longitudinal direction has a significant effect on the convergence to the desired results.
M. Hashemian, M. Jabbarzadeh,
Volume 40, Issue 1 (9-2021)
Abstract
In this paper, nonlinear bending analysis of functionally graded rectangular and sectorial micro/nano plates is investigated using the modified couple stress theory. For this purpose, a higher-order shear deformation theory and von Kármán geometrically nonlinear theory are employed. The equilibrium equations and the boundary conditions for rectangular and annular sector plates are derived from the principle of minimum total potential energy and solved using the Semi-Analytical Polynomial Method (SAPM). One of the advantages of the implemented shear deformation theory is removing the defects of higher order shear deformation theory, and obtaining the response of the first and the third-order shear deformation theories at the same time. Afterwards, beside investigating the benefits of this theory compared with other ones, the results are verified with those by other researches. At the end, the effects of length scale parameter, boundary conditions, power law index, and geometrical dimensions are investigated
