Abstract in English:Abstract The performance of two different steel beam to column connections known as SidePlateTM and a new proposed connection by seismic loading and progressive collapse were investigated in this research. Seismic performance evaluated included consideration of interstory drift angles and flexural strengths based on 2010 AISC Seismic Provisions while investigation of progressive collapse was conducted through satisfaction of acceptance criteria by rotational capacities of the connections provided in UFC 4-023-03 guideline. The results indicated that both SidePlate and the new proposed moment connection were capable of achieving adequate rotational capacity and developing full inelastic capacity of the connecting beam. Also, an excellent performance was exhibited by the connections in terms of keeping the plastic hinges away from the connection and exceeding interstory drift angle of 0.06 rad without fracture developments in beam flange groove-welded joints. Based on results, it was concluded that the SidePlate and the new proposed connection possess sufficient stiffness, strength and ductility to be classified as rigid, full-strength and ductile connections.
Abstract in English:Abstract The paper investigates the effects of application of nonlocal elasticity theory on electromechanical behaviors of single-walled carbon nanotubes under electrostatic actuation. The influences of different dimensions and boundary conditions on the vibration and dynamic instability of the carbon nanotubes are studied, in detail, using this theory. The results reveal that application of the nonlocal elasticity theory leads to the higher pull-in voltages for the nonlocal model applied for carbon nanotubes. Thus, in order to have more accurate results, one should apply nonclassical theorems such as the nonlocal elasticity theory to scrutinize the mechanical and electromechanical behaviors of the nano structures.
Abstract in English:Abstract The differential quadrature method (DQM) is one of the most elegant and efficient methods for the numerical solution of partial differential equations arising in engineering and applied sciences. It is simple to use and also straightforward to implement. However, the DQM is well-known to have some difficulty when applied to partial differential equations involving singular functions like the Dirac-delta function. This is caused by the fact that the Dirac-delta function cannot be directly discretized by the DQM. To overcome this difficulty, this paper presents a simple differential quadrature procedure in which the Dirac-delta function is replaced by regularized smooth functions. By regularizing the Dirac-delta function, such singular function is treated as non-singular functions and can be easily and directly discretized using the DQM. To demonstrate the applicability and reliability of the proposed method, it is applied here to solve some moving load problems of beams and rectangular plates, where the location of the moving load is described by a time-dependent Dirac-delta function. The results generated by the proposed method are compared with analytical and numerical results available in the literature. Numerical results reveal that the proposed method can be used as an efficient tool for dynamic analysis of beam- and plate-type structures traversed by moving dynamic loads.
Abstract in English:Abstract This paper presents the finite element analysis conducted on SFRP strengthened reinforced concrete (RC) deep beams. The analysis variables included SFRP material (glass and carbon), SFRP thickness (3 mm and 5 mm), SFRP configuration and strength of concrete. The externally applied SFRP technique is significantly effective to enhance the ultimate load carrying capacity of RC deep beams. In the finite element analysis, realistic material constitutive laws were utilized which were capable of accounting for the non-linear behavior of materials. The finite element analysis was performed using computer software WCOMD. In the analysis, two dimensional eight-node reinforced concrete planar elements for concrete and planar elements with elastic-brittle behavior for SFRP were used to simulate the physical models. The concept of smeared cracking in concrete and steel was adopted over the element. The calculated finite element results are found to be in good agreement with the experimental results and to capture the structural response of both un-strengthened and SFRP strengthened RC deep beams. A comparison between the finite element results and experimental data proved the validity of the finite element models. Further, the finite element models were utilized to investigate the behavior of RC deep beams strengthened with different directions of SFRP Strips (vertical and horizontal). The vertical SFRP strips are found to be more effective than horizontal ones.
Abstract in English:Abstract This study concerns the dynamic characteristics of a prestressed isotropic, rectangular plate continuously supported by an elastic foundation and carrying accelerating mass M. Closed form solutions of the governing fourth order partial differential equations with variable and singular coefficients are presented. For the two-dimensional plate problem, the solution techniques is based on the double Fourier Finite Sine integral transformation, the expansion of the Dirac Delta function in series form, a modification of Struble's asymptotic method and the use of Fresnel sine and Fresnel cosine integrals. Numerical analyses in plotted curves are presented. The analyses reveal interesting results on the effect of structural parameters such as foundation moduli, rotatory inertia co-rrection factor and prestressing forces on the dynamic behaviour of isotropic rectangular plate under the actions of concentrated masses moving at variable velocity. In particular it is found that the critical velocity of the travelling load which brings about the occurrence of a resonance state increases as the values of these structural parameters increase.
Abstract in English:Abstract Free vibration analysis of rotating functionally graded (FG) thick Timoshenko beams is presented. The material properties of FG beam vary along the thickness direction of the constituents according to power law model. Governing equations are derived through Hamilton's principle and they are solved applying differential transform method. The good agreement between the results of this article and those available in literature validated the presented approach. The emphasis is placed on investigating the effect of several beam parameters such as constituent volume fractions, slenderness ratios, rotational speed and hub radius on natural frequencies and mode shapes of the rotating thick FG beam.
Abstract in English:Abstract A novel Normal and Shear Deformation Theory (NSDT) for analysis of laminated composite and sandwich beams, taking into account shear deformation as well as normal deformation, is developed. The paper investigates flexural behaviors of thick laminated and sandwich beams under plane stress conditions using NSDT. A generalized displacement-based refined formulation is elucidated with inclusion of various warping functions in terms of thickness coordinates to represent shear and normal deformation effects. These effects become pronounced in thick laminated beams and particularly in sandwich beams with transversely flexible core. Present formulation satisfies the shear stress free surface conditions at the top and bottom surfaces of the beam with realistic through-the-thickness variation of transverse shear stresses. The results obtained are compared with higher order theories available in literature. It is observed that NSDT predicts displacement and stresses accurately compared to other higher order theories.
Abstract in English:Abstract The available shear correction factors have mainly been proposed for single-layer rectangular plates with zero shear tractions and isotropic homogenous materials. The present analytical shear factors are especially suitable for the first-order zigzag or layerwise theories of circular sandwich plates with functionally graded cores/face sheets and simultaneous normal and shear tractions. Although the present layerwise correction factors are general, they are evaluated for the modal analyses where effects of the shear correction are more remarkable than those of the stress analyses. It is the first time that the concept of the local shear correction factor is introduced. To present more accurate results, the Mori-Tanaka micromechanical-based material properties model is used instead of the traditional rule of mixtures. The governing equations are solved using the analytical Taylor transform method. Comparisons made among results associated with the known shear correction factors, present results, and results of the three-dimensional theory of elasticity reveal that significant enhancements may occur through using the proposed analytical shear correction factors.
Abstract in English:Abstract According to the research fruits of the diverse damages of bridge in the past, bearings' invalidation is the main reason of the damage of isolated bridges and causes oversized relative displacements between pier and girder. Eventually, it may lead to severe collision of superstructure. It is extremely dangerous when near-fault motion occurs, because it has obvious velocity pulse effect and increases the risk of colliding between girders. Aiming at this problem, this paper puts forward a device named cable-sliding modular expansion joints (CMEJs) that can control the relative displacement and avoid collision. The working principle and mechanical model are described, and then based on a triple continuous seismic isolation bridge which has different heights of piers, a 3D model with or without CMEJs is established. The responses of continuous beam bridges using the CMEJs are comprehensively inspected under the consideration of the velocity pulse effect, and then a real simulation of limit performance of CMEJs is made, focused on CMEJs' restraining effect. The calculation shows that velocity pulse effect would magnify the seismic response of isolation bridges. In addition, the device can well control the displacement and prevent collisions. And the isolation technology combined with CMEJs can be more effective to play their respective roles. The advantage in controlling displacement is obvious.
Abstract in English:Abstract In the work, a two-dimensional problem of a porous material is considered within the context of the fractional order generalized thermoelasticity theory with one relaxation time. The medium is assumed initially quiescent for a thermoelastic half space whose surface is traction free and has a constant heat flux. The normal mode analysis and eigenvalue approach techniques are used to solve the resulting non-dimensional coupled equations. The effect of the fractional order of the temperature, displacement components, the stress components, changes in volume fraction field and temperature distribution have been depicted graphically.