Rectangular Panels Research Articles

New development of design rules for girder with non‐rectangular slender web

AbstractThe current research work focuses on the analysis of longitudinally stiffened I‐girders with slender non‐rectangular web subjected to bending (M), shear (V) and M‐V interaction. Slender structures of thin panels are usually designed according to the rules in EN 1993‐1‐5 generally assuming rectangular panels. For tapered panels, the verifications in EN 1993‐1‐5, are not clearly stated.To investigate the behaviour of the non‐rectangular panels, six large tests have been realised at the laboratory at the University of Stuttgart, composed of unstiffened and longitudinally stiffened girders. The unstiffened and stiffened panels are numerically recalculated, and the model is validated. Based on a validated numerical model, a parametric study on stiffened girders has been performed. The chosen parameters cover the common application range of bridges. The results of the numerical parametric study also proved that the influence of inclined flange in respect of shear resistance may be considered advantageously. Therefore, a new resistance models has been developed, the results of the existing and the new resistance models were evaluated and compared with the numerical results from the parametric study.This paper presents an improved design approach of non‐rectangular panel considering the influence of inclined flange. The proposed approach ensures safe and more economic results for non‐rectangular panels.

Energy Saving and Charging Discharging Characteristics of Multiple PCMs Subjected to Internal Air Flow

One essential utilization of phase change materials as energy storage materials is energy saving and temperature control in air conditioning and indirect solar air drying systems. This study presents an experimental investigation evaluating the characteristics and energy savings of multiple phase change materials subjected to internal flow in an air heating system during charging and discharging cycles. The experimental tests were conducted using a test rig consisting of two main parts, an air supply duct and a room model equipped with phase change materials (PCMs) placed in rectangular aluminum panels. Analysis of the results was based on three test cases: PCM1 (Paraffin wax) placed in the air duct was used alone in the first case; PCM2 (RT–42) placed in the room model was used alone in the second case; and in the third case, the two PCMs (PCM1 and PCM2) were used at the same time. The results revealed a significant improvement in the energy savings and room model temperature control for the air heating system incorporated with multiple PCMs compared with that of a single PCM. Complete melting during the charging cycle occurred at temperatures in the range of 57–60 °C for PCM1 and 38–43 °C for PCM2, respectively, thereby validating the reported PCMs’ melting–solidification results. Multiple PCMs maintained the room air temperature at the desired range of 35–45.2 °C in the air heating applications by minimizing the air temperature fluctuations. The augmentation in discharging time and improvement in the room model temperature using multiple PCMs were about 28.4% higher than those without the use of PCMs. The total energy saving using two PCMs was higher by about 29.5% and 46.7% compared with the use of PCM1 and PCM2, respectively. It can be concluded that multiple PCMs have revealed higher energy savings and thermal stability for the air heating system considered in the current study.

Affordable Roofing System with Square and Rectangular Dome Panels

Affordable roofing is a word, which refers to residence units or habitation units whose prices are assumed/expected to be affordable or economical to a category of community with an identified remuneration limit or scale. Structural roofs are taken in to computation for considerable or valuable price of building in ordinary condition. Thus some savings accomplished in roofing operation or roofing system, significantly decreases the price of the structural units or building unit. In India, BMTPC (Building material and technology promotion council) and HUDCO ( Housing and urban development corporation limited) are the main tow organization or council who have been advertising or promoting appropriate building material and construction technologies in different territory or division of the country. In this roofing, systemized, standardized, advanced roofing units or parts have been used to avoid the temporary structures like shuttering. Hence, the roofing will be economical and progress of work is fast which ensures better in quality. Even though the studies, experiments or researching on this affordable roofing system as not been completely utilized as in other sector or region, a concentrated examination or exploration is to be done to verify the prefabricated roofing which would change the common roofing procedure. The major requisite of choosing affordable roofing system is to develop or advance the rapidity in construction and to decrease the price. In the current work, staadpro software is used for designing the precast RCC roofs and analysis of joist by analytical study using the finite element method. The outcomes which manifest the satisfactory volume of price or cost depletion for various set of panels. In this design, we have considered two least dimensions of 0.5m and 0.75m panels. The aspect ratios which is varying from 1 to 2 and the price depletion is of 0.4% to 9.4% for the least dimension of 0.5m panels. Likewise aspect ratio varying from 1 to 2 with a price depletion from 19.7% to 34.7% for a least dimensions of 0.75m panel size. As the size of the panels increases it becomes cost effective. The preferred roofing system was found to be more cost beneficial as compared with regular RCC roofing system with the increase in dimension of the slab. The roofing system is designed considering M20 concrete and fe415 steel. The beam system panels are precasted and can be easily placed in the position. 3 to 5 masons are enough to easily handle the loads of panels and primary, secondary beam because of weights of panels are less as compare to Conventional slabs. The affordable roofing systems requires lesser time for construction when compare to conventional RCC slab. The major advantage of this roofing is that false roofing works is not required for the dome shaped portion. This dome shaped portion sealing gives good attractive or decorative appearance. The cost analysis made between conventional roofing system and proposed roofing system indicates a cost reduction or depletion of 40% when compare to RCC slab of same size.

Spatially developing supersonic turbulent boundary layer subjected to static surface deformations

The effects of static surface deformations on a spatially developing supersonic boundary layer flow at Mach number M=4 and Reynolds number Reδin≈49300, based on inflow boundary layer thickness (δin), are analyzed by performing large eddy simulations. Two low-order structural modes of a rectangular clamped surface panel of dimensions ≈33δin×48δin are prescribed with modal amplitudes of δin. The effects of these surface deformations are examined on the boundary layer, including changes in the mean properties, thermal and compressibility effects and turbulence structure. The results are analyzed in the context of deviations from concepts typically derived and employed for equilibrium turbulence. The surface deflections, to some degree, modify the correlations that govern both Morkovin’s hypothesis and strong Reynolds analogy away from the wall, whereas in the near-wall region both the hypotheses breakdown. Modifications to the turbulence structure due to the surface deformations are elucidated by means of the wall pressure two-point correlations and anisotropy invariant maps. In addition to the amplification of turbulence, such surface deformations lead to local flow separation, instigating low-frequency unsteadiness. One consequence of significance to practical design is the presence of low frequency unsteadiness similar to that encountered in impinging or ramp shock boundary layer interactions.

Dating Nathan: The Oldest Stained Glass Window in England?

Relatively little is known about stained glass windows in England predating c. 1170; however, art-historical evaluation by Caviness (1987) argued that four figures from the “Ancestors series” of Canterbury Cathedral, usually dated to the late 12th and early 13th century, in fact date earlier (c. 1130–1160). This would place them amongst the earliest stained glass in England, and the world. Building on our previous work, we address Caviness’s hypothesis using a methodology based upon analysis of a few, well-measured heavy trace elements and a 3D-printed attachment for a pXRF spectrometer that facilitates in situ analysis. The results confirm two major periods of “recycling” or re-using medieval glass. The first is consistent with Caviness’s argument that figures predating the 1174 fire were reused in the early 13th century. The results suggest that in addition to figures, ornamental borders were reused, indicating the presence of more early glass than previously thought. In the second period of recycling (1790s), surviving figures from the Ancestors series were removed and adapted into rectangular panels for insertion into large Perpendicular-style windows elsewhere in the cathedral. The results show that the glasses used to adapt the panels to a rectangular shape were broadly contemporary with the glasses used to glaze the original Ancestors windows, again representing a more extensive presence of medieval glass in the windows.

A study on ballistic performance of origami sandwich panels

Sandwich structures with origami cores have shown great potential for engineering applications. However, few studies have been performed on the ballistic performance of origami sandwich panels, particularly on their plastic deformation and ballistic resistance. In this study, rectangular metallic sandwich panels with aluminium origami cores were manufactured. Quasi-static indentation and ballistic impact tests were conducted to explore their ballistic performance. Three different shapes of indenters were considered: flat-ended, hemispherical-nosed and conical-nosed. Plastic deformation and energy absorption capacities were observed and analysed. Subsequently, finite element (FE) simulations using Ansys/Ls-dyna were executed to compare the ballistic performance of sandwich panels with origami cores and honeycomb cores. Parametric studies were also conducted to examine the effect of wall thickness, cell edge length and cell number of origami cores on the ballistic performance of origami sandwich panels.

Assessment of the geometrically nonlinear behavior of thin cleavage type surface defects of anisotropic structure under shear

When designing up-to-date composite structure defects are allowable. In this case an important factor for design is in-service non-propagation of allowable defects. Thin surface defects of rectangular delamination type are examined in this paper. Defect structure is anisotropic and boundary conditions correspond to rigid support. Let us assume that tangential forces act in load-bearing composite panel plane. This investigation subject is thin surface rectangular defect. It is assumed that given shear forces act on the defect and its geometrically non-linear behavior is possible. For expert estimation of defect mode of deformation by Bubnov-Galerkin method analytical solution of non-linear problem is obtained. Expressions for rectangular panel membrane stress which appear in case of post-buckling behavior due to shear are explicitly given for mode of deformation estimation. In order to supplement practical significance of obtained analytical solution thin anisotropic panel design method based on post-buckling state with tangential forces is shown.

Designing of Thin Composite Panels with the Post-Buckling Behavior Considering Rigid Support and Loading with Shear Flows

Geometrically non-linear problem of orthotropic thin rectangular panel post-buckling behavior with shear is solved. Deflection function takes all-boundary rigid support conditions into account. Based on derived solution method of smooth panels design which can be used for aircraft structures rib and spar webs optimal parameters is suggested.

Analysis of stability and bearing capacity of reinforced panels made of composite materials under shear

When performing stress verification analysis of wing spar supported composite walls it is essential to estimate local stability of smooth wall and general stability of orthotropic panel under shear forces. Almost square fragment of spar wall supported with ribs (between two ribs) is examined in this paper. In order to estimate general stability and load-bearing capacity of orthotropic panel geometrically nonlinear problem is examined. When examining linear problem compact expression for critical shear flow definition is explicitly written in order to estimate general stability with ultimate loading. When examining nonlinear problem a system of two equations in deflection amplitude is obtained. Besides nonlinear problem of smooth wall (skin) local stability and postbuckling state estimation with possible geometrically nonlinear behavior is examined. Analytical solution of orthotropic rectangular panel with shear geometrically nonlinear problem is obtained. Based on method of design by postbuckling state with critical shear stress provided with buckling a method of skin thickness definition is suggested. In order to apply obtained solutions to design activities method of orthotropic panels design by stability and postbuckling state with corresponding load level is shown.

On attached masses of panels oscillating in incompressible medium

The paper discusses small oscillations of a panel in an incompressible medium. Air can be considered an incompressible medium during modal tests of solar array panels for spacecraft deployed on the ground in a lab environment. A panel is represented as a two-sided boundary surface. Conditions are determined for applicability of the potential motion of the medium. Calculation of the attached mass is reduced to the solution of the Neumann boundary value problem. To solve the boundary value problem, the method of boundary elements is used in the piecewise constant approximation variant, which provides a solution of the hypersingular boundary integral equation. Numerical solutions are obtained for the three fundamental modes of rectangular panels. The obtained numerical values are refined using non-linear Shanks transformation. Dependence of attached mass on panel elongation and the amount of the gap between its fragments is studied. For any in-plane oscillation mode of a panel fragment, the attached mass is determined using the principle of linear superposition. An estimate is given of the effect of the distance from the panel to the wall on the attached mass value. Key words: oscillations, incompressible medium, air, attached mass, rectangular panels, boundary elements method.

Three dimensional numerical solution for the bending study of magneto-piezo-elastic spherical and cylindrical shells

This paper presents an exact solution for the static analysis of magneto-electro-elastic simply supported shallow shells panels. The mechanical equations are derived via equilibrium elasticity relations. The electrical and magnetic governing equations are obtained by electrostatic and magnetostatic equilibrium relations. The shell displacements, electrical and magnetic potential functions are solved analytically by the Navier closed form solutions. The governing equations formulated in terms of thickness coordinate are solved semi-analytically by using the differential quadrature method. The Lagrange polynomials are employed as basis functions. The equations are discretized per each layer by the Chebyshev-Gauss-Lobatto grid distribution. The continuity conditions in the adjacent layers for mechanical displacement, transverse dielectric displacement, electric and magnetic scalar function and transverse magnetic induction are complied. The correct load traction condition is considered at the top and bottom of the shell. Numerical results for spherical, cylindrical and rectangular panels are reported. The results are in excellent agreement with other 3D elasticity solutions reported in the literature so a new benchmark problem for shell is proposed.

ON ATTACHED MASSES OF PANELS OSCILLATING IN INCOMPRESSIBLE MEDIUM

The paper discusses small oscillations of a panel in an incompressible medium. Air can be considered an incompressible medium during modal tests of solar array panels for spacecraft deployed on the ground in a lab environment. A panel is represented as a two-sided boundary surface. Conditions are determined for applicability of the potential motion of the medium. Calculation of the attached mass is reduced to the solution of the Neumann boundary value problem. To solve the boundary value problem, the method of boundary elements is used in the piecewise constant approximation variant, which provides a solution of the hypersingular boundary integral equation. Numerical solutions are obtained for the three fundamental modes of rectangular panels. The obtained numerical values are refined using non-linear Shanks transformation. Dependence of attached mass on panel elongation and the amount of the gap between its fragments is studied. For any in-plane oscillation mode of a panel fragment, the attached mass is determined using the principle of linear superposition. An estimate is given of the effect of the distance from the panel to the wall on the attached mass value. Key words: oscillations, incompressible medium, air, attached mass, rectangular panels, boundary elements method.

Cyclic behavior of an innovative braced ductile thin shear panel

This study aimed to investigate the cyclic behavior of an innovative braced ductile thin shear panel (BDSP) component consisting of a concentric rectangular thin shear panel, a surrounding flange plate, and X-shaped brace segments. A total of eight BDSP specimens at a one-third scale were designed, considering the influence of shear panel thickness, shear panel dimension, and stiffening rib space. The tests were performed by applying a reversed cyclic lateral load. All specimens exhibited a high initial lateral stiffness and stable cyclic behavior and failed in the shear panel region. The adoption of stiffening ribs reduced the ductility of test specimens but enhanced the lateral strength and energy dissipation. Pinching of the lateral force versus drift ratio was observed for the BDSP specimens without stiffening ribs, which exhibited considerably high deformability and limited energy dissipation. Additionally, the specimens without stiffening ribs experienced elastic shear buckling behavior and developed a tension field mechanism in the shear panel region along the main diagonal direction. The overstrength factor (RΩ) value of 1.4 was conservatively recommended for the BDSP specimens without stiffening ribs.

Thermo-Acoustic Effects on the Natural Frequencies of Vibration of an Elastic Rectangular Panel

In this paper, the thermo-acoustic behavior of a rectangular panel fully immersed in a compressible fluid at rest is investigated. A boundary element method (BEM) has been employed taking into account the Kirchhoff–Helmholtz (K-H) integral equation for the acoustic pressure and with the fluid-plate interface boundary condition the acoustic pressure jump over the panel is calculated. The thermal effects are considered regarding in the form of a uniform increment of temperature of the panel and are analyzed in order to prevent the buckling phenomena. The deformation modes of the panel correspond to the vacuum case. Applying a collocation method for the panel equation, the natural frequencies are obtained. The effects of several geometric parameters regarding different thermal loads on these frequencies are evaluated. Furthermore, the influence of the wave number for different temperatures of the panel on the acoustic damping ratio is evaluated, as well as the acoustic radiation efficiency for the different modes. The verification of the method is proven with other works.

Experimental of Inverted-T Shape Reinforced Concrete Wall Subjected to Blast Load

Reinforced concrete (RC) widely used as the construction material for the main structural element for many significant structures such as bridge and building because of its relatively high strength and economical. However, there still lacks research published regarding the appropriate reinforcement steel arrangement in a complete RC structure subjected to blast load. Most of the published experimental works focused on the small rectangular or square RC panel. From the record search, the approved design by professional engineers, when RC wall subjected to the possibility of blast load, both RC wall details either retaining wall or shear wall implemented. Therefore, the full-scale blast experiment is vital to appraise the appropriate steel reinforcement arrangement in the RC wall. The blast experiment indicated, with different steel reinforcement arrangement in the RC wall, the better blast resistance with the number of cracks on the RC wall is significantly less from one another for the wall with the arrangement of horizontal flexural reinforcement tied-outside the vertical flexural reinforcement and the hooked-in direction of vertical flexural steel reinforcement into the wall base.

Numerical Study on the Behavior and Bearing Mechanism of Flat Slabs in Column Loss Events

This study investigates the behavior and the load-bearing mechanism of a typical flat slab with rectangular panels in several scenarios including the removal of a corner, penultimate, and internal columns. The scenarios are rather similar to those used in the conventional evaluation of the progressive collapse potential; however, application of the uniformly distributed loading over panels adjacent to the removed columns was not limited to twice the value of the initial load. Thus, load-deflection curves were drawn up to the point in which a great number of longitudinal slab bars ruptured. Introducing 5 stages on each curve, finite element outputs on concrete cracking pattern and rebar stress state were presented. A significant increase in the stresses along the diagonals of the slab panels accompanied by bar ruptures around columns adjacent to the removed column proved contribution of an important load-bearing mechanism in addition to the behavior called “quasiframe action.” Consecutive rupture of bars showed formation of a zipper-type collapse mode as well as a great tendency to transfer load share of missing column mainly along shorter direction of slab panels. Moreover, the findings indicated that the slab damaged zone could exceed the panels under uniform overloading.

Edge-clamped two-way slabs containing low-ductility steel

This paper describes a series of full range load tests on two-way, edge-clamped reinforced concrete slab panels containing either Class L WWF or Class N deformed bars. Five rectangular slab panels were tested each with two adjacent fully restrained edges and two free edges. A point support was included under the corner of each panel at the intersection of the two free edges. Each slab specimen was loaded by four transverse loads applied symmetrically in the mid-panel region by a deformation-controlled actuator in a stiff testing frame. The continuous edge supports were provided by clamping two adjacent edges in a carefully designed and constructed testing frame. The slabs were instrumented with load cells to measure applied forces and reactions, strain gauges to measure strain in the steel reinforcement and on the concrete surfaces, linear variable displacement transducers and lasers to measure deflections at all stages of loading. The results of the tests are presented and evaluated, with particular emphasis on the strength, ductility and failure mode of the slabs.

Analysis of post buckling state of composite rectangular panel with asymmetric structure on elastic base caused biaxial compression

Received analytical solution of geometrically nonlinear problem for investigation of post buckling of composite rectangular panel with asymmetric structure on elastic base. Panel deflection corresponds to conditions of rigidity support. Considered longitudinal compression of panel subject to constraint along the longitudinal edges which corresponds panel loading caused biaxial compression. Results can be used in the analysis of post buckling thin defects such as delaminations in laminated skins.

External excitation effects on the flutter characteristics of a 2-DOF rigid rectangular panel

The flutter of a rigid panel is considered as a super/subcritical Hopf bifurcation. However, the initial conditions of such characteristics have not been extensively explored. In this study, a 2-DOF rigid rectangular panel was tested in a wind tunnel at zero angle of attack to investigate the flutter stability, with and without external excitations, in the Reynolds number range of 6.15–8.21×104. Coupled flutter occurs abruptly and evolves into four stages as the inflow wind velocity reaches a critical flutter velocity, Ucr. A hysteresis loop is observed when the wind velocity is decreased from Ucr to 0.75Ucr. External excitations are applied to the test model stepwise in the hysteresis region to examine the stability conditions. The critical excitation amplitude, Acr, is determined, which corresponded to the unstable limit cycle of the subcritical Hopf bifurcation. A fitted equation of the bifurcation is provided to correlate the flutter amplitude and the critical excitation amplitude with wind speed. PIV measurements show the flow field evolution around the panel during the entire flutter occurrence process. The size of the leading-edge vortex expands as the oscillation amplitude increases, then convects to the trailing edge and eventually sheds into the wake region. Wake patterns of each flutter stage were illustrated and analyzed using the Dynamic Mode Decomposition (DMD) method.

Study on analytical global modes for a multi-panel structure connected with flexible hinges

A dynamic modeling method for a multi-panel structure connected with flexible hinges is proposed in this paper. For the solar array composed of several flexible rectangular panels, the global explicit modal functions of spatial coordinates are obtained by employing the Rayleigh-Ritz method, which are in favor of deriving the lower-dimension discrete dynamic equations and the design of controllers for the system in the further research. The Gram-Schmidt characteristic orthogonal polynomials are adopted to construct the flexible deformation expressions of the solar panel. The Lagrange multipliers are introduced to describe the constraint at flexible hinges. The eigen equation of the multi-panel structure is derived to obtain the natural frequencies and corresponding global modes of the system through the Rayleigh-Ritz procedure. Considering the natural frequency calculated from the finite element method as a reference value, the correctness of the modeling process is validated by comparing results with those obtained from the finite element method. Moreover, a high accuracy of the proposed method are confirmed by a very good agreement between results from ANSYS and the theoretical method proposed here. The proposed method derives analytical global modes of the whole system which can be conveniently used to design the controller and work out the nonlinear dynamic model and with a few degree-of-freedoms directly. Finally, the interesting mode interchanged phenomenon is observed with the variation of the stiffness of the rotation spring at flexible hinges.