| 1. |
- Atashipour, Rasoul, 1983, et al.
(författare)
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A weak shear web model for deflection analysis of deep composite box-type beams
- 2018
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 155, s. 36-49
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Tidskriftsartikel (refereegranskat)abstract
- Deep box-type beams, consisting of framing members and sheathings, are sensitive to shear deformations andhence appropriate refined theories or complicated magnification factors are needed to be used to obtain accurate results. For sheathings or webs between the framing members that are weak in shear, additional shear deformations occur corresponding to the relative axial displacement between the framing members. These sandwich-type or partial interaction-type of in-plane shear behaviour between the framing members, needs to betaken into account, especially when the web shear stiffness is very low. The composite box-type beam treatedhere is composed of three framing members with sheathings on both sides. To incorporate effects of the sheathings shear deformations between the framing members on the deflection, the sheathings, here called web interlayers, are modelled as shear media with equivalent slip moduli corresponding to a partially interacting composite beam model. Governing equilibrium equations of the model are obtained using the minimum total potential energy principle and solved explicitly. The obtained results are compared with those based on different conventional beam theories and 3-D finite element (FE) simulations. It is shown that the model is capable of predicting accurately the deflection for a wide range of geometry and property parameters. It is demonstrated that the deflection of such deep box-type beams can be expressed as the summation of three different effects, namely bending deformations, conventional shear deformations in the framing members and sheathings, and additional in-plane shear deformations or shear slips of the weak web causing relative axial displacements between the framing members.
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| 2. |
- Atashipour, Rasoul, 1983, et al.
(författare)
-
Exact Lévy-type solutions for bending of thick laminated orthotropic plates based on 3-D elasticity and shear deformation theories
- 2017
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Ingår i: Composite Structures. - : Elsevier BV. - 0263-8223 .- 1879-1085. ; 163, s. 129-151
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Tidskriftsartikel (refereegranskat)abstract
- Exact solutions for static bending of symmetric laminated orthotropic plates with different Lévy-type boundary conditions are developed. The shear deformation plate theories of Mindlin-Reissner and Reddy as well as the three-dimensional elasticity theory are employed. Using the minimum total potential energy principle, governing equilibrium equations of laminated orthotropic plates and pertaining boundary conditions are derived. Closed-form Lévy-type solutions are obtained for the governing equations of both theories using separation of variables method and different types of classical boundary conditions, namely simply-supported, clamped and free edge, are exactly satisfied. Thereafter, 3-D elasto-static equations for orthotropic materials are solved for bending analysis of laminated plates using two different approaches. First, the method of separation of variables is utilised and an exact closed-from solution is achieved for simply-supported laminated orthotropic plates. Next, a combined Fourier-Differential Quadrature (DQ) approach is employed to present a semi-numerical solution for bending of laminated orthotropic plates with Lévy-type boundary conditions based on the three-dimensional elasticity theory. High accuracy of the presented solutions are proven and comprehensive comparative numerical results are provided and discussed. Presented comparative numerical results can serve as benchmark for investigating the correctness of new solution methods which may be established in the future.
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| 3. |
- Atashipour, Rasoul, 1983, et al.
(författare)
-
Influence of grain inclination angle on shear buckling of laminated timber sheathing products
- 2018
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Ingår i: Structures. - : Elsevier BV. - 2352-0124. ; 13, s. 36-46
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in timber production industries have enabled production of new innovative laminated timberproducts having layers with grain inclination angle. This paper is aimed to study influence of grain inclinationangle in the laminated veneer lumber (LVL) and plywood sheathings on their shear buckling loads. Two extremeedge conditions of simply supported and clamped edges are considered. First, an accurate differential quadrature(DQ) computational code is developed using MAPLE programming software to obtain eigen buckling values andtheir corresponding eigen mode shapes. Next, for convenience of engineering calculations, approximate algebraic formulae are presented to predict critical shear buckling loads and mode shapes of LVL and plywood panels having layers with grain inclination angle, with adequate accuracy. Furthermore, finite element (FE) modelling is conducted for several cases using ANSYS software to show validity and accuracy of the predicted results for theproblem. It is shown that the highest shear buckling loads of LVL sheathings is achievable when the inclination angle of about 30° with respect to the shorter edges is considered for production of LVL panels, whereas the same angle with respect to the long edges of the LVL sheathings results in a relatively lower buckling load. Considering similar inclination angle with respect to any edges of a plywood sheathings will also results in its highest prebuckling capacity. It is also demonstrated that, under optimal design and certain loading circumstances, LVL shows a higher shear buckling capacity compared to a similar plywood sheathing.
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| 4. |
- Atashipour, Rasoul, 1983, et al.
(författare)
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On buckling of layered composite heavy columns—Effect of interlayer bonding imperfection
- 2023
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 260-261
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Tidskriftsartikel (refereegranskat)abstract
- Buckling loads of partial composite columns under distributed axial loads is investigated in this paper for the first time. The interlayer interaction corresponding to the level of interfacial bonding imperfection in the layered heavy composite columns is formulated in the model by a shear slip/stiffness modulus. Governing differential equations and boundary equations are derived and represented in a general dimensionless form. A semi-analytical solution is applied to the governing buckling equations of the presented model using power-series technique to extract critical loads of partial composite columns. Five different classical end types are considered namely clamped–clamped (C-C), clamped-pinned (C-P), clamped-sliding (C-S), clamped-free (C-F) and pinned–pinned (P-P). Also, for two extreme cases of non-composite/zero-interaction and full-composite/perfectly-bonded layered columns, exact closed-form characteristic buckling equations are introduced. A convergence study is conducted to ensure stability of the applied power-series solution. It is demonstrated that the obtained buckling loads for partial composite columns with different end conditions approach those obtained from the exact closed-from solution for the full-composite extreme case when the interfacial shear modulus approaches infinity. Effect of imperfect bonding between the column layers and slip on critical buckling loads is investigated. It is shown that a more realistic model based on the partial composite interaction hypothesis predicts critical loads that are less than those based on idealized composite columns with perfect interfacial bonding.
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| 5. |
- Atashipour, Rasoul, 1983, et al.
(författare)
-
Stability analysis of three-layer shear deformable partial composite columns
- 2017
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 106-107, s. 213-228
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Tidskriftsartikel (refereegranskat)abstract
- This paper is focused on the effect of imperfect bonding and partial composite interaction between the sub-elements of a box-type column on the critical buckling loads. The box column is modelled as a symmetric three-layer composite structure with interlayer slips at the interfaces, based on the Engesser–Timoshenko theory with uniform shear deformation assumptions. Linear shear springs or slip modulus is considered at the interfaces to model the partial interaction between the sub-elements of the structure. The minimum total potential energy principle is utilized to obtain governing equations and boundary conditions. A direct analytical solution of the original governing equations is presented for obtaining exact buckling characteristic equation of the three-layer partial composite column with different end conditions including clamped-pinned end conditions. Also, the coupled equations are recast into an efficient uncoupled form and shown that there is a strong similarity with those for the two layer element. It is shown that the obtained formulae are converted to the known Euler column formulae when the slip modulus approaches infinity (i.e. perfect bonding) and no shear deformations in the sub-elements are considered. A differential shear Engesser–Timoshenko partial composite model is also employed and critical buckling loads, obtained from an inverse solution method, are compared to examine the validity and accuracy level of the uniform shear model. Comprehensive dimensionless numerical results are presented and discussed.
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| 6. |
- Atashipour, Seyed Rasoul, et al.
(författare)
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On the Shear Buckling of Clamped Narrow Rectangular Orthotropic Plates
- 2015
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Ingår i: Mathematical problems in engineering (Print). - : Hindawi Limited. - 1024-123X .- 1563-5147. ; 2015
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with stability analysis of clamped rectangular orthotropic thin plates subjected to uniformly distributed shear load around the edges. Due to the nature of this problem, it is impossible to present mathematically exact analytical solution for the governing differential equations. Consequently, all existing studies in the literature have been performed by means of different numerical approaches. Here, a closed-form approach is presented for simple and fast prediction of the critical buckling load of clamped narrow rectangular orthotropic thin plates. Next, a practical modification factor is proposed to extend the validity of the obtained results for a wide range of plate aspect ratios. To demonstrate the efficiency and reliability of the proposed closed-form formulas, an accurate computational code is developed based on the classical plate theory (CPT) by means of differential quadrature method (DQM) for comparison purposes. Moreover, several finite element (FE) simulations are performed via ANSYS software. It is shown that simplicity, high accuracy, and rapid prediction of the critical load for different values of the plate aspect ratio and for a wide range of effective geometric and mechanical parameters are the main advantages of the proposed closed-form formulas over other existing studies in the literature for the same problem.
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| 7. |
- Atashipour, Seyed Rasoul, et al.
(författare)
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The Effect of Weak Shear Webs on the Deformations of Timber Box Type Beams
- 2015
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Ingår i: Proceedings of the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing. - Stirlingshire : Civil-Comp Press.
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Konferensbidrag (refereegranskat)abstract
- This paper deals with deflection analysis of a deep composite box beam due to inplane shear deformations, especially the modelling of the shear deformations in the webs is considered. The beam is composed of three framing members with sheathings on both sides. The sheathings or webs between the framing members are modelled as shear media with equivalent slip moduli corresponding to the partially composite beam model with three separated layers and two interlayer slip areas. The minimum total potential energy principle is employed to obtain the governing equilibrium equations and corresponding boundary conditions. The coupled set of governing equations is recast into an uncoupled form and solved explicitly together with the corresponding boundary conditions. The closed-form solutions obtained are compared to those based on the conventional beam theories. It is shown that the model is capable of predicting accurately the deflections for a wide range of geometry and property parameters, especially for small shear stiffness (slip modulus) values for the webs. The formula for the deflection is reduced to the Timoshenko formula for full composite interaction when the shear slip modulus of the web approaches infinity. Comparative numerical results are presented to show the influence of bending deformations, shear deformations in the framing layers and the in-plane shear deformations in the sheathings.
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| 8. |
- Caprolu, Giuseppe, et al.
(författare)
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Analytical and experimental evaluation of the capacity of the bottom rail in partially anchored timber shear walls
- 2012
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Ingår i: World Conference on Timber Engineering 2012 (WCTE 2012). - : WCTE 2012 Committee. - 9781622763054 ; , s. 157-166, s. 157-166
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Konferensbidrag (refereegranskat)abstract
- Kallsner and Girhammar have developed plastic design methods for light-frame timber shear walls that can be used for determining the load-carrying capacity when the shear walls are partially anchored. For such walls, the leading stud is not fully anchored against uplift and tying down forces are developed in the sheathing-to-framing joints. Since the forces in the anchor bolts and the sheathing-to-framing joints do not act in the same vertical plane, the bottom rail will be subjected to cross-wise bending, leading to possible splitting along the bottom side of the rail. Another possible brittle failure mode is splitting along the edge of the bottom rail in line with the sheathing-to-framing fasteners. An experimental program has been conducted using different anchor bolt locations, washer sizes and pith orientations. A fracture mechanics approach for the two failure modes is used to evaluate the experimental results. The comparison shows a good agreement between the experimental and analytical results. The failure mode is largely dependent on the distance between the edge of the washer and the edge of the bottom rail. The size of the washer seems also to have some influence on the failure load. The fracture mechanics models seem to capture the essential behaviour of the splitting modes and to include the decisive parameters. These parameters can easily be adjusted to experimental results and be used in design equations for bottom rails in partially anchored shear walls.
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| 9. |
- Caprolu, Giuseppe, et al.
(författare)
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Analytical models for splitting capacity of bottom rails in partially anchored timber frame shear walls based on fracture mechanics
- 2017
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 12:3, s. 165-188
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Tidskriftsartikel (refereegranskat)abstract
- Plastic design methods can be used for determining the load-carrying capacity of partially anchored shear walls. For such walls, the leading stud is not fully anchored against uplift and tying down forces are developed in the sheathing-to-framing joints and the bottom rail will be subjected to crosswise bending, leading to possible splitting failure of the rail. In order to use these plastic design methods, a ductile behaviour of the sheathing-to-framing joints must be ensured. In two earlier experimental programmes, the splitting failure capacity of the bottom rail has been studied. Two brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the side surface of the bottom rail. In this article, a fracture mechanics approach for the two failure modes is used to evaluate the experimental results. The comparison shows a good agreement between the experimental and analytical results. The failure mode is largely dependent on the distance between the edge of the washer and the loaded edge of the bottom rail. The fracture mechanics models seem to capture the essential behaviour of the splitting modes and to include the decisive parameters.
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| 10. |
- Caprolu, Giuseppe, et al.
(författare)
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Comparison of models and tests on bottom rails in timber frame shear walls experiencing uplift
- 2015
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 94, s. 148-163
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Tidskriftsartikel (refereegranskat)abstract
- The authors present two different studies: one experimental study and one where analytical models developed to calculate the splitting failure capacity of bottom rails in partially anchored timber frame shear walls are evaluated and validated. The experimental study was divided into three parts with specimens matched to each other: (1) first the splitting capacity and failure mode of bottom rails subjected to uplift were studied; (2) then material properties such as tensile strength perpendicular to the grain; and (3) fracture energy were determined by testing specimens cut from the specimens belonging to study (1). The experimental results were compared with models based on a linear fracture mechanics approach presented earlier, using as input values results from (2) and (3). Almost all tested models show good agreement with the test results. The models showing the best agreement have been selected and proposed to be used as basis for calculation of the splitting failure capacity of bottom rails in partially anchored timber frame shear walls. (C) 2015 Elsevier Ltd. All rights reserved.
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