Trapezoidal Wall Research Articles

К ВОПРОСУ ОЦЕНКИ ДЕФОРМАТИВНОСТИ СТЕНКИ ТОНКОСТЕННЫХ ХОЛОДНОГНУТЫХ ПРОФИЛЕЙ С ТРАПЕЦИЕВИДНОЙ ЧАСТЬЮ В БОЛТОВЫХ УЗЛОВЫХ СОЕДИНЕНИЯХ

The article discusses a new nodal connection of thin-walled and cold-formed profiles with a trapezoidal part of the wall using a through stop bushing. The use of this constructive solution allows to place additional bolts in the area of the concave part of the wall of a thin-walled profile, thereby including this area in work. It is noted that the invention in comparison with analogs allows to simplify the assembly process of the node by fixing the position of the sleeve when using a broadened part on one side of the gusset. At the same time, in order to effectively resist the loss of local stability of the wall of a thin-walled and cold-formed profile, it is proposed to arrange adjacent bushings with sides in the opposite direction. Issues of deformability of the wall of a thin-walled and cold-formed profile are studied when additional rows of bolts are installed in the trapezoidal part of the wall due to the developed design solutions: using a through bushing, a through bushing with a stop and in the absence of bolts in the area of the trapezoidal part. The paper presents the results of displacements of the wall under the influence of a compressive load with different variations of bolted nodal joints. A comparative assessment of the efficiency of nodal connections from the point of view of resistance to loss of local stability has been carried out. In result, it is revealed that a bolted nodal connection with the installation of additional bolts in a part of a trapezoidal wall, due to the use of a through bushing, can reduce deformability by 15% and by 33% when using a through bushing with an emphasis in relation to a connection with a two-row bolting

DESIGNING A TRAPEZOIDAL MODULAR BLOCK WALL WITH NONLINEAR OPTIMIZATION

A rectangular wall is better in terms of stability and ease of calculation than a trapezoidal wall. However, a trapezoidal wall is sometimes inevitable such as a retaining wall construction near rockface. FHWA provides simplified rules to design a trapezoidal wall. However, FHWA does not give an example to follow, and the rules need trial and error to implement. BS8006 gives an exact dimension of the block heights, but designing still needs to adjust the block widths. A 16-meters high modular block wall project near rock face in Thailand as an example to illustrate a calculation detail in external stability checking follow FHWA simplified rules and BS8006. The illustrations are trapezoidal walls with two zones, three zones, and four zones. Nonlinear optimization models are also used to minimize the wall base length to facilitate the construction instead of jacking the near rock face to build a rectangular wall. Optimization models also help to relax FHWA simplified rules and BS8006 guidelines. Using an optimization model can decrease the base length from 0.7H to 0.6H for a rectangular wall or even 0.5H for a rectangular wall with competent foundation soil. Optimization models can also achieve a base length down to 0.48H with a decrease in the cross-sectional area down to 0.92 for a three zones trapezoidal wall. A simple three zones wall with exact dimensions is also proposed in the competent foundation soil conditions.

Inverse estimation of the time-dependent wall temperature in stagnation region of an annular jet on a cylinder rod using Levenberg–Marquardt method

For the first time, a numerical solution code, based on Levenberg–Marquardt method is presented for solving non-linear problem of inverse heat transfer in axisymmetric stagnation flow impinging on a cylinder rod to determine time-dependent wall temperature by temperature distribution at a specific point in the fluid region. Also, the effect of noisy data on the final result has been studied. For this purpose, the numerical solution of the dimensionless temperature and the convective heat transfer in a radial incompressible flow on a cylinder axis is carried out as a direct problem. In the direct problem, the free stream is steady with an initial flow strain rate of $$\overline{k}$$ . Using similarity variable and appropriate transformations, momentum and energy equations are converted into semi-similar equations. The new equation systems are then discretized using an implicit finite difference method and solved by applying the tridiagonal matrix algorithm (TDMA). The wall temperature is then estimated by applying the Levenberg–Marquardt parameter estimation approach. This technique is an iterative approach based on minimizing the least-square summation of the error values, the error being the difference between the estimated and measured temperatures. Results of the inverse analysis indicate that the Levenberg–Marquardt algorithm is an efficient and acceptably stable technique for estimating wall temperature in axisymmetric stagnation flow. The maximum value of the sensitivity coefficient is related to the estimation of polynomial wall temperature and its value is 0.1952 also the minimum value of the sensitivity coefficient is 8.62 × 10–6 which is related to the triangular wall temperature. The results show that the parameter estimation error in calculating the triangular and trapezoidal wall temperature is greater than the others because the maximum value of RMS error is obtained for these two cases, which are 0.451 and 0.479, respectively, the reason for the increase in error in estimating these functions is the existence of points where the first derivative of the function does not exist. This method also exhibits considerable stability for noisy input data.

New nodal connection of thin-walled cold formed profiles with a trapezoidal wall using separate welded bushings

The article suggests a new constructive solution of the node made of thin-walled cold-formed profiles with a part of concave flat wall with the use of separate welded bushings for bolt arrangement. To assess the load-carrying capacity of the proposed node numerical and experimental study of a prototype model, consisting of thin-walled cold-formed profiles connected by a gusset plate with a bolt, using separate welded bushings was fulfilled. By results of researches character of pressure distribution in places of bolts installation is revealed and actual carrying capacity of new node is defined. The significance of the obtained research results for the construction industry lies in the fact that the new design solution of the node with the use of separate welded bushings makes it possible to eliminate the gap between the gusset plate and trapezoidal wall of the profile, thus performing the bolt fastening in this place and improving the actual work of the node. It should be noted that the proposed solution of connection with the use of separate welded bushings allows increasing the carrying capacity of the node, taking into account the installation of bolts in the concave part of the profile wall.

Numerical simulations of flow around two tandem wall-mounted structures at high Reynolds numbers

In the present study, the flow around two-dimensional (2D) square and trapezoidal wall- mounted structures in tandem on a horizontal flat wall has been simulated using two-dimensional Reynolds-averaged Navier-Stokes (RANS) equations combined with the standard k−ω SST turbulence model. The Reynolds number (Re) based on the free stream velocity and the height of the structures is set to be 1.19 × 105. The effects of the gap ratio between the two structures as well as the slope angles of the two sides of the trapezoidal structures on the hydrodynamic quantities and the flow around the two structures have been investigated and discussed.

Free convection in a trapezoidal enclosure divided by a flexible partition

The Fluid-Structure Interaction (FSI) approach was utilized to model the displacement of a flexible partition in a trapezoidal enclosure due to interaction with an internal natural convection flow. A moving mesh technique, Arbitrary Lagrangian–Eulerian (ALE) method, is adopted to model the partition displacement and the flow and heat transfer in the enclosure. The finite element method is employed to solve the governing equations after transforming into a non-dimensional form. The effect of various non-dimensional parameters such as Rayleigh number, Prandtl number, trapezoidal walls inclination angles, and non-dimensional Young's modulus. The results show that the increase of Rayleigh number increases the heat transfer in the enclosure and the tension in the partition. Notably, raising Ra from 104 to 107 can increase the heat transfer rate in the cavity by 8 times. The inclination angle of cavity walls induces a minimal effect on the induced tensions in the partition while it influences the heat transfer. In particular, heat transfer rate in a square cavity is 15% higher than in a trapezoidal cavity having side walls with 30° angle of inclination.

Numerical study on fluid-flow characteristics of peristaltic pump

Flow characteristics in a peristaltic pump, which can be applied to Micro Total Analysis Systems (μ-TAS), were numerically investigated. For the present computational analysis, we assumed a simple sinusoidal wave pattern to simulate the peristaltic motion of flexible channel wall and applied the Immersed Boundary method to the treatment of the wall boundary. The effects of the parameters such as the amplitude and velocity of the peristaltic motion upon the flow characteristics and pump performance were evaluated in the present paper. Saw-toothed or trapezoidal wall patterns were also calculated to examine the potentiality of the pumping flow rate increase.

Geometrical perturbation of an inclined wall on decay times of acoustic modes in a trapezoidal cavity with an impedance surface

Decay times of acoustic modes of a trapezoidal cavity (TC modes) with an inclined wall are studied. Each cavity wall is successively assigned an impedance surface and the other five walls are rigid. The decay times are obtained from the coupling between rigid-walled modes of the rectangular cavity (RC modes) that bounds the trapezoidal cavity. Two coupling mechanisms are identified, namely, the damping coupling and the geometrical coupling. The former is related to the coupling of RC modes at the impedance surface, while the latter is related to the coupling of RC modes at the inclined wall. Both mechanisms include the same volume coupling where RC modes couple throughout the trapezoidal cavity. When the impedance surface is at either of the two trapezoidal walls, the grouping of TC modes with same decay times and the decay time variation with the wall inclination are determined only by the damping coupling. When the surface is at any of the other rectangular walls, both the damping and geometrical couplings are at work. This paper provides an understanding of how the inclined wall and the impedance surface location affect the TC-mode grouping, and what determines the decay time variation with the inclination.