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.

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.

scholarly journals Effects of Grain Pattern on the Rolling Shear Properties of Wood in Cross-Laminated Timber

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 668
Author(s):  
Guofang Wu ◽  
Yong Zhong ◽  
Haiqing Ren
Keyword(s):  
Shear Modulus ◽  
Mechanical Performance ◽  
Wood Products ◽  
Rolling Shear ◽  
Shear Moduli ◽  
Factors Affecting ◽  
Cross Laminated Timber ◽  
Aspect Ratios ◽  
Shear Property ◽  
Pure Rolling

Rolling shear modulus and strength are the key factors affecting the mechanical performance of some wood products such as cross-laminated timber (CLT). As reported, rolling shear property strongly depends on the sawing pattern such as the aspect ratio and grain direction (grain mode). However, the mechanism behind this phenomenon has not yet been clarified. In this work, the rolling shear modulus and strength of spruce-pine-fir (SPF) with different grain modes and aspect ratios were experimentally investigated. In addition, a theoretical investigation was carried out to reveal the mechanism behind this phenomenon. The results exhibited that the rolling shear moduli of 0° and 90° grain-mode wood were the same. This value can be called the pure rolling shear modulus. Rolling shear modulus of wood with angles other than 0° and 90° can be calculated from the pure rolling shear modulus and grain angle. Therefore, this modulus can be called the apparent rolling shear modulus. Thus, using 0° and 90° grain-mode specimens to determine the pure rolling shear modulus and strength of wood is recommended.

scholarly journals Out-of-plane local mechanism analysis with finite element method

2021 ◽  
Vol 8 (1) ◽  
pp. 130-136
Author(s):  
Roberto Spagnuolo
Keyword(s):  
Finite Element ◽  
Masonry Walls ◽  
Finite Element Models ◽  
Mechanism Analysis ◽  
Fem Method ◽  
Local Mechanism ◽  
Out Of Plane ◽  
Smeared Crack ◽  
The Stability ◽  
No Tension Material

Abstract The stability check of masonry structures is a debated problem in Italy that poses serious problems for its extensive use. Indeed, the danger of out of plane collapse of masonry walls, which is one of the more challenging to evaluate, is traditionally addressed not using finite element models (FEM). The power of FEM is not properly used and some simplified method are preferred. In this paper the use of the thrust surface is suggested. This concept allows to to evaluate the eccentricity of the membrane stresses using the FEM method. For this purpose a sophisticated, layered, finite element with a no-tension material is used. To model a no-tension material we used the smeared crack method as it is not mesh-dependent and it is well known since the early ’80 in an ASCE Report [1]. The described element has been implemented by the author in the program Nòlian by Softing.

scholarly journals Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 532
Author(s):  
Emily E. Pocock ◽  
Richard J. Mandle ◽  
John W. Goodby
Keyword(s):  
Liquid Crystalline ◽  
Computational Study ◽  
Structure Property ◽  
Correlation Lengths ◽  
Aspect Ratios ◽  
Smectic Phases ◽  
Out Of Plane ◽  
Lower Temperature ◽  
Soft Crystal ◽  
Optical Textures

Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (NTB) phases. While the features that give rise to NTB phase formation are now somewhat understood, a comparable structure–property relationship governing the formation of layered (smectic) phases from the NTB phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both NTB and intercalated smectic phases. The higher temperature smectic phase is assigned as SmCA based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ‘’X’’ phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens.

Estimation of Seismic Energy Dissipation for Steel Slit Shear Walls Considering Out-of-Plane Buckling

2021 ◽  
Author(s):  
Yiming Ma ◽  
Liusheng He ◽  
Ming Li
Keyword(s):  
Energy Dissipation ◽  
Shear Walls ◽  
Seismic Energy ◽  
Thickness Ratio ◽  
Design Parameters ◽  
Test Results ◽  
Loading Test ◽  
Aspect Ratios ◽  
Out Of Plane ◽  
Energy Dissipation Capacity

Steel slit shear walls (SSSWs), made by cutting slits in steel plates, are increasingly adopted in seismic design of buildings for energy dissipation. This paper estimates the seismic energy dissipation capacity of SSSWs considering out-of-plane buckling. In the experimental study, three SSSW specimens were designed with different width-thickness ratios and aspect ratios and tested under quasi-static cyclic loading. Test results showed that the width-thickness ratio of the links dominated the occurrence of out-of-plane buckling, which produced pinching in the hysteresis and thus reduced the energy dissipation capacity. Out-of-plane buckling occurred earlier for the links with a larger width-thickness ratio, and vice versa. Refined finite element model was built for the SSSW specimens, and validated by the test results. The concept of average pinching parameter was proposed to quantify the degree of pinching in the hysteresis. Through the parametric analysis, an equation was derived to estimate the average pinching parameter of the SSSWs with different design parameters. A new method for estimating the energy dissipation of the SSSWs considering out-of-plane buckling was proposed, by which the predicted energy dissipation agreed well with the test results.

Strains and Deflections of GFRP Sandwich Panels Due to Uniform Out-of-Plane Pressure

2002 ◽  
Vol 39 (04) ◽  
pp. 223-231
Author(s):  
J. C. Roberts ◽  
M. P. Boyle ◽  
P. D. Wienhold ◽  
E. E. Ward
Keyword(s):  
Finite Element ◽  
Compressive Strain ◽  
Sandwich Panels ◽  
External Pressure ◽  
Woven Fabric ◽  
Core Material ◽  
Finite Element Models ◽  
Strain Gages ◽  
Glass Fiber Reinforced Plastic ◽  
Out Of Plane

Rectangular orthotropic glass fiber reinforced plastic sandwich panels were tested under uniform out-of-plane pressure and the strains and deflections were compared with those from finite-element models of the panels. The panels, with 0.32 cm (0.125 in.) face sheets and a 1.27 cm (0.5 in.)core of either balsa or linear polyvinylchloride foam, were tested in two sizes: 183 × 92 cm (72 × 36 in.) and121 × 92 cm (48 × 36 in.). The sandwich panels were fabricated using the vacuum-assisted resin transfer molding technique. The two short edges of the sandwich panels were clamped, while the two long edges were simply supported. Uniform external pressure was applied using two large water inflatable bladders in series. The deflection and strains were measured using dial gages and strain gages placed at quarter and half points on the surface of the panels. Measurements were made up to a maximum out-of-plane pressure of 0.1 MPa (15psi). A total of six balsa core and six foam core panels were tested. Finite-element models were constructed for the 183-cm-long panel and the121-cm-long panel. Correlation between numerical and experimental strains to deflect the sandwich panel was much better on the top (tensile) side of the panels than on the bottom (compressive)side of the panels, regardless of panel aspect ratio or core material. All sandwich panels exhibited the same compressive strain reversal behavior on the compressive side of the panel. This phenomenon was thought to be due to nonlinearly induced micro-buckling under the strain gages, buckling of the woven fabric, or micro-cracking within the resin.

Multi-performance blast pressure-duration curves of laminated glass panes

2020 ◽  
pp. 204141962096883
Author(s):  
Mohammadreza Eslami ◽  
Khalid M Mosalam ◽  
Venkatesh Kodur ◽  
Shalva Marjanishvili ◽  
Brian Katz ◽  
...  
Keyword(s):  
Blast Resistance ◽  
Design Procedure ◽  
Performance Criteria ◽  
Laminated Glass ◽  
Limit States ◽  
Performance Levels ◽  
Performance Pressure ◽  
Pull Out ◽  
Aspect Ratios ◽  
Ultimate Failure

The current design procedure for blast resistant glass panes is based on dynamic analysis of idealized SDOF models under simplified triangular impulse loads or code-specified pressure-duration (pressure-impulse) curves. In both cases, the main objective is to prevent failure of the pane with no explicit consideration of other limit states to reach higher performance levels. In this study, multi-performance pressure-duration curves of Laminated Glass (LG) panes are estimated by accurate pre-validated Finite Element (FE) models. Multiple performance criteria including initial cracking, PVB-50% (maximum polyvinyl butyral, i.e. PVB, interlayer strain of 50%), PVB-100% (maximum PVB interlayer strain of 100%), and ultimate failure of the pane are considered and pressure-duration curves are estimated for each of these performance levels. Ultimate failure of the pane can be either due to rupture of the PVB interlayer or pull-out of the pane from its frame. Multi-performance pressure-duration curves are obtained for 18 different LG panes with three different layups, two widths, and three aspect ratios. According to the obtained results, the thickness of the glass layers has more pronounced contribution to the blast resistance of the panes in all limit states compared with the PVB thickness. Moreover, the ultimate failure mode of the LG panes with thicker PVB interlayer is observed to be typically pull-out of the pane rather than PVB rupture. Therefore, these panes require frames with deeper bites to develop their full blast resistance. Finally, the blast performance of the LG panes are compared with that of Thermally Tempered Glass (TTG) panes to shed more light on the superior blast resistance of LG panes.

scholarly journals Influence of an MgTiTaON Inserted Layer on Magnetic Properties and Microstructure of FePtAgC Films

Coatings ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 238 ◽  
Author(s):  
Jai-Lin Tsai ◽  
Cheng Dai ◽  
Jyun-you Chen ◽  
Ting-Wei Hsu ◽  
Shi-Min Weng ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Cross Section ◽  
Lattice Relaxation ◽  
Fept Film ◽  
Perpendicular Magnetization ◽  
Aspect Ratios ◽  
Out Of Plane ◽  
Temperature Deposition ◽  
Critical Lattice ◽  
C 30

The FePt film above 10 nm critical lattice relaxation thickness was prepared and the ultrathin MgTiTaON layer was interleaved in between FePt film and the multilayer stack is FePt(6 nm)/[MgTiTaON(1 nm)/FePt(4 nm)]2. Next, the FePt films were co-sputtered with (Ag, C) segregants during deposition and the layer stacks is FePt(6 nm)(Ag, C)(x vol %)/[MgTiTaON (1 nm)/FePt(4 nm)(Ag, C) (x vol %)]2 (x = 0, 10, 20, 30, 40). After high temperature deposition at 470 °C, the granular FePt(Ag, C, MgTiTaON) film illustrated perpendicular magnetization and the out-of-plane coercivity (Hc) was increased with (Ag, C) segregants and the highest Hc is 18.3 kOe when x = 40. From cross-section images, the FePt layer are more continuous with 0 and 10 vol% (Ag, C) segregants and changed to an island structure when the (Ag, C) segregants increase to 20–40 vol %. The FePt grains were grown in separated islands in 20, 30 vol % (Ag, C) and changed to dense columnar-like morphology in 40 vol%. The second nucleated grains which contribute the in-plane magnetization are found in FePt (Ag, C) (40 vol %) film. The FePt islands are reached by inserting the ultrathin MgTiTaON layer and the island heights of FePt(Ag, C) (30, 40 vol %) are around 31–38 nm and the aspect ratios are 0.6–0.8.

scholarly journals Calculation of orthotropic plates for creep taking into account shear deformations

2018 ◽  
Vol 196 ◽  
pp. 01002 ◽  
Author(s):  
Anton Chepurnenko ◽  
Batyr Yazyev ◽  
Angelica Saibel
Keyword(s):  
Differential Equations ◽  
Transverse Shear ◽  
System Of Differential Equations ◽  
Orthotropic Plates ◽  
Shear Deformations ◽  
Tangential Stresses ◽  
Distributed Load ◽  
Uniformly Distributed Load ◽  
Basic Hypothesis

A system of differential equations is obtained for calculating the creep of orthotropic plates taking into account the deformations of the transverse shear. The basic hypothesis is a parabolic change in tangential stresses over the thickness of the plate. An example of the calculation is given for a GRP plate hinged on the contour under the action of a uniformly distributed load.

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