ASSESSMENT OF SHEAR ANALOGY AND TIMOSHENKO METHOD FOR ANALYZING HYBRID CLT UNDER OUT-OF-PLANE LOADING

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
MD Tanvir Rahman ◽  
Mahud Ashraf ◽  
Kazem Ghabraie ◽  
Mahbube Subhani
Keyword(s):  
Shear Modulus ◽  
Numerical Models ◽  
Natural Material ◽  
Fiber Direction ◽  
Viable Option ◽  
Rolling Shear ◽  
Significant Interest ◽  
Out Of Plane ◽  
Superior Mechanical Properties ◽  
Cross Layers

Timber is a natural material which offers superior mechanical properties in parallel to fiber direction when compared against those in perpendicular to the fibers. Cross-laminated timber (CLT) is made up of layers of structurally graded timber, orthogonally oriented in layers whereby it can sustain loading in both directions. CLT is often used as floor panels, and hence, its performance under out-of-plane loading is of significant interest. Low rolling shear modulus resulting in higher shear flexibility of the cross-layers tend to decrease the effective bending stiffness of CLT sections. Developing hybrid CLT using timbers with higher rolling shear modulus as cross-layers in CLT is considered a viable option to improve its performance under out-of-plane loading. The present study investigates the performance of shear analogy and Timoshenko methods in predicting the deflection of hybrid CLT panels while considering different span-to-depth ratios and various combinations of rolling shear modulus. Numerical models were developed to conduct a parametric study and obtained deflection results were compared against those calculated from the shear analogy method and Timoshenko method. It was observed that for CLT with a small span-to-depth ratio and cross-layers made from material with higher rolling shear modulus, the deflection calculated from the analytical methods deviates from the values obtained from the numerical model.

scholarly journals Evaluating Timoshenko Method for Analyzing CLT under Out-of-Plane Loading

Buildings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 184
Author(s):  
MD Tanvir Rahman ◽  
Mahmud Ashraf ◽  
Kazem Ghabraie ◽  
Mahbube Subhani
Keyword(s):  
Shear Modulus ◽  
Shear Deformation ◽  
Numerical Study ◽  
Wood Products ◽  
Tangential Plane ◽  
Rolling Shear ◽  
Laminated Veneer Lumber ◽  
Engineered Wood ◽  
Out Of Plane ◽  
Cross Layers

Cross-laminated timber (CLT) is an engineered wood product made up of layers of structurally graded timber, where subsequent layers are oriented orthogonally to each other. In CLT, the layers oriented in transverse direction, generally termed as cross-layer, are subjected to shear in radial–tangential plane, which is commonly known as rolling shear. As the shear modulus of cross-layers is significantly lower than that in other planes, CLT exhibits higher shear deformation under out-of-plane loading in contrast to other engineered wood products such as laminated veneer lumber (LVL) and glue laminated timber (GLT). Several analytical methods such as Timoshenko, modified gamma and shear analogy methods were proposed to account for this excessive shear deformation in CLT. This paper focuses on the effectiveness of Timoshenko method in hybrid CLT, in which hardwood cross-layers are used due to their higher rolling shear modulus. A comprehensive numerical study was conducted and obtained results were carefully analyzed for a range of hybrid combinations. It was observed that Timoshenko method could not accurately predict the shear response of CLTs with hardwood cross layers. Comprehensive parametric analysis was conducted to generate reliable numerical results, which were subsequently used to propose modified design equations for hybrid CLTs.

Rolling shear modulus and strength of beech wood laminations

Holzforschung ◽  
2016 ◽  
Vol 70 (8) ◽  
pp. 773-781 ◽  
Author(s):  
Simon Aicher ◽  
Zachary Christian ◽  
Maren Hirsch
Keyword(s):  
Shear Strength ◽  
Shear Modulus ◽  
Beech Wood ◽  
European Beech ◽  
Rolling Shear ◽  
Shear Properties ◽  
Shear Moduli ◽  
Major Interest ◽  
Characteristic Values ◽  
Cross Layers

Abstract Previous research indicated that the rolling shear properties of European beech wood (Fagus sylvatica) are considerably higher than those of softwood. The aim of the presented investigation was to substantiate previous data on rolling shear modulus and strength of European beech wood and to further evaluate its substitution of softwoods in applications where shear properties are influential, namely as cross layers in cross-laminated timber (CLT). Further, the effect of the annual ring orientation within the boards on shear modulus and strength was of major interest. The beech specimens comprised four different sawing patterns, classified unambiguously with reference to the pith location. The shear properties were determined by 50, two-plate shear tests with specimen cross-section dimensions of 33 mm × 135 mm. A mean rolling shear modulus of 370 N mm-2 was obtained, whereby no significant detrimental effect for pith boards with cracks was observed. In agreement with continuum mechanics, the semi-quarter-sawn boards revealed the highest shear moduli whereas the quarter-sawn boards showed roughly 30% lower values. The mean rolling shear strength was 5.6 N mm-2 for all specimens, whereby pith specimens resulted in generally lower values. The 5% quantile, disregarding pith specimens, was 4.5 N mm-2. In conclusion, the rolling shear strength and modulus exceed the respective characteristic values for softwoods by roughly factors of 5 and 7, indicating great potential for beech wood cross-layers in CLT.

scholarly journals The Rolling Shear Influence on the Out-of-Plane Behavior of CLT Panels: A Comparative Analysis

Buildings ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 42 ◽  
Author(s):  
Antonio Sandoli ◽  
Bruno Calderoni
Keyword(s):  
Shear Modulus ◽  
Flexural Behavior ◽  
Finite Element Models ◽  
Limit States ◽  
Shear Deformations ◽  
Rolling Shear ◽  
Tangential Stresses ◽  
Aspect Ratios ◽  
Out Of Plane ◽  
Fully Connected

This paper deals with the influence of the rolling shear deformation on the flexural behavior of CLT (Cross-Laminated Timber) panels. The morphological configuration of the panels, which consist of orthogonal overlapped layers of boards, led to a particular shear behavior when subjected to out-of-plane loadings: the low value of the shear modulus in orthogonal to grain direction (i.e., rolling shear modulus) gives rise to significant shear deformations in the transverse layers of boards, whose grains direction is perpendicular with respect to the tangential stresses direction. This produces increases of deflections and vibrations under service loads, creating discomfort for the users. Different analytical methods accounting for this phenomenon have been already developed and presented in literature. Comparative analyses among the results provided by some of these methods have been carried out in the present paper and the influence of the rolling shear deformations, with reference to different span-to-depth (L/H) ratios investigated. Moreover, the analytical results have also been compared with those obtained by more accurate 2D finite element models. The results show that, at the service limit states, the influence of the rolling shear can be significant when the aspect ratios became less than L/H = 30, and the phenomenon must be accurately considered in both deflection and stress analysis of CLT floors. Contrariwise, in the case of higher aspect ratios (slender panels), the deflections and stresses can be evaluated neglecting the rolling shear influence, assuming the layers of boards as fully-connected.

Turbulent energy transfer in bidimensional numerical models of plasma

2021 ◽  
Author(s):  
Rocio Manobanda ◽  
Christian Vasconez ◽  
Denise Perrone ◽  
Raffaele Marino ◽  
Dimitri Laveder ◽  
...  
Keyword(s):  
Solar Wind ◽  
Energy Transfer ◽  
Numerical Models ◽  
Collisionless Plasma ◽  
Space Plasma ◽  
Turbulent Energy ◽  
Turbulent Medium ◽  
Scaling Properties ◽  
Magnetic Diffusivity ◽  
Out Of Plane

<p>Structured, highly variable and virtually collision-free. Space plasma is an unique laboratory for studying the transfer of energy in a highly turbulent environment. This turbulent medium plays an important role in various aspects of the Solar--Wind generation, particles acceleration and heating, and even in the propagation of cosmic rays. Moreover, the Solar Wind continuous expansion develops a strong turbulent character, which evolves towards a state that resembles the well-known hydrodynamic turbulence (Bruno and Carbone). This turbulence is then dissipated from magnetohydrodynamic (MHD) through kinetic scales by different -not yet well understood- mechanisms. In the MHD approach, Kolmogorov-like behaviour is supported by power-law spectra and intermittency measured in observations of magnetic and velocity fluctuations. In this regime, the intermittent cross-scale energy transfer has been extensively described by the Politano--Pouquet (global) law, which is based on conservation laws of the MHD invariants, and was recently expanded to take into account the physics at the bottom of the inertial (or Hall) range, e.g. (Ferrand et al., 2019). Following the 'Turbulence Dissipation Challenge', we study the properties of the turbulent energy transfer using three different bi-dimensional numerical models of space plasma. The models, Hall-MHD (HMHD), Landau Fluid (LF) and Hybrid Vlasov-Maxwell (HVM), were ran in collisionless-plasma conditions, with an out-of-plane ambient magnetic field, and with magnetic diffusivity carefully calibrated in the fluid models. As each model has its own range of validity, it allows us to explore a long-enough range of scales at a period of maximal turbulence activity. Here, we estimate the local and global scaling properties of different energy channels using a, recently introduced, proxy of the local turbulent energy transfer (LET) rate (Sorriso-Valvo et al., 2018). This study provides information on the structure of the energy fluxes that transfers (and dissipates) most of the energy at small scales throughout the turbulent cascade. </p>

Effect of Swelling Behavior on Elastomeric Materials: Experimental and Numerical Investigation

2013 ◽  
Author(s):  
Sayyad Zahid Qamar ◽  
Maaz Akhtar ◽  
Moosa S. M. Al-Kharusi
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Poisson’S Ratio ◽  
Saline Water ◽  
Numerical Models ◽  
Oil And Gas Industry ◽  
Material Behavior ◽  
Poisson's Ratio ◽  
Energy Potential ◽  
Finite Element Software

In the last ten years, a new type of advanced polymer known as swelling elastomer has been extensively used as sealing element in the oil and gas industry. These elastomers have been instrumental in various new applications such as water shutoff, zonal isolation, sidetracking, etc. Though swell packers can significantly reduce costs and increase productivity, their failure can lead to serious losses. Integrity and reliability of swelling-elastomer seals under different field conditions is therefore a major concern. Investigation of changes in material behavior over a specified swelling period is a necessary first step for performance evaluation of elastomer seals. Current study is based on experimental and numerical analysis of changes in compressive and bulk behavior of an elastomeric material due to swelling. Tests and simulations were carried out before and after various stages of swelling. Specimens were placed in saline water (0.6% and 12% concentration) at a temperature of 50°C, total swelling period being one month. Both compression and bulk tests were conducted using disc samples. A small test rig had to be designed and constructed for determination of bulk modulus. Young’s modulus (under compression) and bulk modulus were determined for specimens subjected to different swelling periods. Shear modulus and Poisson’s ratio were calculated using isotropic relations. Experiments were also simulated using the commercial finite element software ABAQUS. Different hyperelastic material models were examined. As Ogden model with second strain energy potential gave the closest results, it has been used for all simulations. The elastomer was a fast-swell type. There were drastic changes in material properties within one day of swelling, under both low and high salinity water. Values of elastic and shear modulus dropped by more than 90% in the first few days, and then remained almost constant during the rest of the one-month period. Poisson’s ratio, as expected, showed a mirror behavior of a sharp increase in the first few days. Bulk modulus exhibited a fluctuating pattern; rapid initial decrease, then a slightly slower increase, followed by a much slower decrease. Salinity shows some notable effect in the first 5 or 6 days, but has almost no influence in the later days. Very interestingly, Poisson’s ratio approaches the limiting value of 0.5 within the first 10 days of swelling, justifying the assumption of incompressibility used in most analytical and numerical models. In general, simulations results are in good agreement with experimental ones.

scholarly journals Towards more realistic values of elastic moduli for volcano modelling

2020 ◽  
Author(s):  
Michael Heap ◽  
Marlène Villeneuve ◽  
Fabien Albino ◽  
Jamie Farquharson ◽  
Elodie Brothelande ◽  
...  
Keyword(s):  
Rock Mass ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Volcanic Rock ◽  
Elastic Moduli ◽  
Numerical Models ◽  
Laboratory Data ◽  
Volcanic Rocks ◽  
Published Data ◽  
Selection Of

<p>The accuracy of elastic analytical solutions and numerical models, widely used in volcanology to interpret surface ground deformation, depends heavily on the Young’s modulus chosen to represent the medium. The paucity of laboratory studies that provide Young’s moduli for volcanic rocks, and studies that tackle the topic of upscaling these values to the relevant lengthscale, has left volcano modellers ill-equipped to select appropriate Young’s moduli for their models. Here we present a wealth of laboratory data and suggest tools, widely used in geotechnics but adapted here to better suit volcanic rocks, to upscale these values to the scale of a volcanic rock mass. We provide the means to estimate upscaled values of Young’s modulus, Poisson’s ratio, shear modulus, and bulk modulus for a volcanic rock mass that can be improved with laboratory measurements and/or structural assessments of the studied area, but do not rely on them. In the absence of information, we estimate upscaled values of Young’s modulus, Poisson’s ratio, shear modulus, and bulk modulus for volcanic rock with an average porosity and an average fracture density/quality to be 5.4 GPa, 0.3, 2.1 GPa, and 4.5 GPa, respectively. The proposed Young’s modulus for a typical volcanic rock mass of 5.4 GPa is much lower than the values typically used in volcano modelling. We also offer two methods to estimate depth-dependent rock mass Young’s moduli, and provide two examples, using published data from boreholes within Kīlauea volcano (USA) and Mt. Unzen (Japan), to demonstrate how to apply our approach to real datasets. It is our hope that our data and analysis will assist in the selection of elastic moduli for volcano modelling. To this end, our new publication (Heap et al., 2019), which outlines our approach in detail, also provides a Microsoft Excel© spreadsheet containing the data and necessary equations to calculate rock mass elastic moduli that can be updated when new data become available. The selection of the most appropriate elastic moduli will provide the most accurate model predictions and therefore the most reliable information regarding the unrest of a particular volcano or volcanic terrain.</p><p>Heap, M.J., Villeneuve, M., Albino, F., Farquharson, J.I., Brothelande, E., Amelung, F., Got, J.L. and Baud, P., 2019. Towards more realistic values of elastic moduli for volcano modelling. Journal of Volcanology and Geothermal Research, https://doi.org/10.1016/j.jvolgeores.2019.106684.</p>

scholarly journals Column Stiffness Requirements for Diagonally Stiffened Steel Plate Shear Walls

2020 ◽  
Vol 9 (5) ◽  
pp. 101-109
Keyword(s):  
Aspect Ratio ◽  
Steel Plate ◽  
Numerical Models ◽  
Shear Walls ◽  
Shear Capacity ◽  
Thickness Ratio ◽  
Steel Plate Shear Wall ◽  
Out Of Plane ◽  
The Impact ◽  
Stiffened Steel

Various numerical models of diagonally stiffened steel plate shear wall were tested under push-over loads to study the required stiffness of columns of diagonally stiffened SPSWs. This research presents a parametric study to explore the influence of varying the infill panel’s thickness, width, and height and the number of floors on the stiffness of the edge columns, and to propose expressions to predict the column’s in-plane stiffness and area required for preliminary design. Different SPSWs were modeled with a range of several stories, an aspect ratio, and height to thickness ratio, respectively, of (n=3-7), (Lp /hp=1-2), and (λ=200-400). The results indicated that the number of floors (n) has a great effect on the wall’s shear capacity. A greater number of floors lead to buckling in columns and early failure of the system, and subsequently, an increase in the column’s rigidity is required. Moreover, an equation is proposed to calculate the value of ωh required for sufficient inertia of the column. Higher the drift is, lower the shear capacity of the wall is, particularly for walls with a larger aspect ratio (Lp /hp > 1.5), and smaller height to thickness ratio (λ < 400). It is proposed that the columns’ out-of-plane stiffness divided by its in-plane stiffness to be equal or greater than 0.4. An equation is also proposed to predict the required columns’ rx substantial to assure that the columns can resist the impact of the tension field and the plate achieves full yield strength.

scholarly journals Numerical Modelling of Glass Fiber Reinforced Polymer (GFRP) Cross Arm

2019 ◽  
Vol 8 (4) ◽  
pp. 6484-6489
Keyword(s):  
Failure Modes ◽  
Limit State ◽  
Geometrical Model ◽  
Fiber Direction ◽  
Ultimate Limit State ◽  
Element Analysis ◽  
Plane Shear ◽  
Glass Fiber Reinforced ◽  
Out Of Plane ◽  
The Matrix

Composites are not isotropic like their metal counterparts, e.g. steel and aluminum, as they are made of two distinctive phases known as the matrix and the reinforcing phases. In addition, weight, fiber direction, fiber composition and even the manufacturing process are all critical factors in determining the strength, stiffness and the behaviour of a composite member. All of that create more challenging designing and manufacturing approaches. This paper shows how to model a GFRP cross arm using SOLIDWORKS to create the 3D geometrical model because it has an intuitive and easy to use user interface, and ANSYS to create the numerical model and the analysis for its great and comprehensive capabilities in the finite element analysis. The cross arm was found to be safe against the failure modes of fiber, matrix, in-plane shear, out-of-plane shear and delamination under all load cases which satisfies the ultimate limit state requirements but the concern was on the serviceability limit state which had a deflection of 34 mm.

Analytical and Experimental Analysis of a Precision Positioning Actuator System

2004 ◽  
Author(s):  
Jason G. Gullicks ◽  
William H. Semke
Keyword(s):  
Composite Materials ◽  
Mechanical Response ◽  
Numerical Models ◽  
Design Concept ◽  
Concept Design ◽  
Out Of Plane ◽  
Manufacturing Procedure ◽  
Actuator System ◽  
Smart Actuator ◽  
Bending Modes

An innovative flexure design concept is developed that involves the use of composite materials with bonded piezoelectric actuators to create a “smart actuator” for nanometer scale positioning both in and out of plane. The utilization of smart actuators/sensors will have many benefits over current positioning stages including the utilization of advantageous composite properties, the increase of the resonant frequency of the stage system, the simplification of the manufacturing procedure, and possible increased range of motion. Enhanced mechanical response is made possible by using composite materials and proper layer orientation. This work is a “proof of concept” design for the ultra-precision smart actuator. Analytical and numerical models were developed to determine the response of the composite material and piezoelectric actuator system. Experimentation was performed on the system to verify the results of the mathematical and numerical models. Good correlation between mathematical, numerical, and experimental data was seen in axial and bending modes of operation. Results from the parametric and experimental verification studies are presented to illustrate the efficacy of the design concept.

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