| 1. |
- Heng, Piseth, et al.
(författare)
-
Residual stiffness and strength of shear connectors in steel-concrete composite beams after being subjected to a pull-out pre-damaging : An experimental investigation
- 2017
-
Ingår i: Structures. - : Elsevier. - 2352-0124. ; 11, s. 189-205
-
Tidskriftsartikel (refereegranskat)abstract
- Horizontal stability of the medium rise steel frame structures is usually ensured by vertical bracings and diaphragm action of composite floors. Load transfer within the composite floor system is made through shear connectors, e.g. headed studs. In an event of explosion, such connectors must reserve sufficient residual stiffness and strength in order to avoid a sudden or delayed collapse of the building. These remaining capacities have not been experimentally studied yet in the literature. This paper presents large scale horizontal push out tests to determine the residual stiffness of the shear connectors after being initially damaged by explosion. The initial damaging is reproduced by a pull-out test using a quasi-static loading. Two types of numerical simulation have also been developed using ABAQUS/CAE software to provide a better understanding of the experimental results.
|
|
| 2. |
- Alsafadie, R., et al.
(författare)
-
Corotational mixed finite element formulation for thin-walled beams with generic cross-section
- 2010
-
Ingår i: Computer Methods in Applied Mechanics and Engineering. - : Elsevier BV. - 0045-7825 .- 1879-2138. ; 199:49-52, s. 3197-3212
-
Tidskriftsartikel (refereegranskat)abstract
- The corotational technique is adopted here for the analysis of three-dimensional beams. The technique exploits the technology that applies to a two-noded element, a coordinate system which continuously translates and rotates with the element. In this way, the rigid body motion is separated out from the deformational motion. In this paper, a mixed formulation are adopted for the derivation of the local element tangent stiffness matrix and nodal forces. The mixed finite element formulation is based on an incremental form of the two-field Hellinger-Reissner variational principle to permit elasto-plastic material behavior. The local beam kinematics is based on a low-order nonlinear strain expression using Bernoulli assumption. The present formulation captures both the Saint-Venant and warping torsional effects of thin-walled open cross-sections. Shape functions that satisfy the nonlinear local equilibrium equations are selected for the interpolation of the stress resultants. In particular, for the torsional forces and the twist rotation degree of freedom, a family of hyperbolic interpolation functions is adopted in lieu of conventional polynomials. Governing equations are expressed in a weak form, and the constitutive equations are enforced at each integration cross-section along the element length. A consistent state determination algorithm is proposed. This local element, together with the corotational framework, can be used to analyze the nonlinear buckling and postbuckling of thin-walled beams with generic cross-section. The present corotational mixed element solution is compared against the results obtained from a corotational displacement-based model having the same beam kinematics and corotational framework. The superiority of the mixed formulation is clearly demonstrated.
|
|
| 3. |
- Alsafadie, R., et al.
(författare)
-
Local formulation for elasto-plastic corotational thin-walled beams based on higher-order curvature terms
- 2011
-
Ingår i: Finite elements in analysis and design (Print). - : Elsevier. - 0168-874X .- 1872-6925. ; 47:2, s. 119-128
-
Tidskriftsartikel (refereegranskat)abstract
- The paper deals with the derivation of a local elasto-plastic finite element formulation of three dimensional corotational beams with arbitrary cross- section. Based on Bernoulli beam kinematics, an improved displacement field is constructed by inclusion of second-order terms of cross-section local rotations. The formulation captures both the Saint-Venant and warping torsional effects of open cross sections. Numerical tests show that the inclusion of the second-order terms of the local bending curvatures gives more accurate and more efficient element that allows a significant reduction of the computational time.
|
|
| 4. |
- Alsafadie, R., et al.
(författare)
-
Three-dimensional formulation of a mixed corotational thin-walled beam element incorporating shear and warping deformation
- 2011
-
Ingår i: Thin-walled structures. - : Elsevier. - 0263-8231 .- 1879-3223. ; 49:4, s. 523-533
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a corotational formulation of a three-dimensional elasto-plastic mixed beam element that can undergo large displacements and rotations. The corotational approach applies to a two-noded element a coordinate system which continuously translates and rotates with the element. In this way, the rigid body motion is separated out from the deformational motion. In this paper, a mixed formulation is adopted for the derivation of the local element tangent stiffness matrix and nodal forces based on a two-field Hellinger-Reissner variational principle. The local beam kinematics is based on a low-order nonlinear strain expression using Timoshenko assumption. The warping effects are characterized by adopting Benscoter theory that describes the warping degree of freedom by an independent function. Shape functions that satisfy the nonlinear local equilibrium equations are selected for the interpolation of the stress resultants. This local element, together with the corotational framework, can be used to analyze the nonlinear buckling and postbuckling of thin-walled beams with generic cross-section. The mixed formulation solution is compared against the results obtained from a corotational displacement-based formulation having the same beam kinematics. The superiority of the mixed formulation is clearly demonstrated.
|
|
| 5. |
- Battini, Jean-Marc, et al.
(författare)
-
Non-linear finite element analysis of composite beams with interlayer slips
- 2009
-
Ingår i: Computers & structures. - : Elsevier BV. - 0045-7949 .- 1879-2243. ; 87:13-14, s. 904-912
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a new non-linear finite element formulation for the analysis of two-layer composite plane beams with interlayer slips. The element is based on the corotational method. The main interest of this approach is that different linear elements can be automatically transformed to non-linear ones. To avoid curvature locking that may occur for low order element(s). a local linear formulation based on the exact stiffness matrix is used, Five numerical applications are presented in order to assess the performance of the formulation.
|
|
| 6. |
- Chhang, Sophy, et al.
(författare)
-
An energy-momentum co-rotational formulation for nonlinear dynamics of planar beams
- 2017
-
Ingår i: Computers & structures. - : Elsevier Ltd. - 0045-7949 .- 1879-2243. ; 187, s. 50-63
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents an energy-momentum integration scheme for the nonlinear dynamic analysis of planar Euler-Bernoulli beams. The co-rotational approach is adopted to describe the kinematics of the beam and Hermitian functions are used to interpolate the local transverse displacements. In this paper, the same kinematic description is used to derive both the elastic and the inertia terms. The classical midpoint rule is used to integrate the dynamic equations. The central idea, to ensure energy and momenta conservation, is to apply the classical midpoint rule to both the kinematic and the strain quantities. This idea, developed by one of the authors in previous work, is applied here in the context of the co-rotational formulation to the first time. By doing so, we circumvent the nonlinear geometric equations relating the displacement to the strain which is the origin of many numerical difficulties. It is rigorously shown that the proposed method conserves the total energy of the system and, in absence of external loads, the linear and angular momenta remain constant. The accuracy and stability of the proposed algorithm, especially in long term dynamics with a very large number of time steps, is assessed through four numerical examples.
|
|
| 7. |
- Chhang, Sophy, et al.
(författare)
-
An energy-momentum formulation for nonlinear dynamics of planar co-rotating beams
- 2017
-
Ingår i: COMPDYN 2017 - Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. - Athens : National Technical University of Athens. - 9786188284425 ; , s. 3682-3696
-
Konferensbidrag (refereegranskat)abstract
- This article presents an energy-momentum integration scheme for the nonlinear dynamic analysis of planar Bernoulli/Timoshenko beams. The co-rotational approach is adopted to describe the kinematics of the beam and Hermitian functions are used to interpolate the local transverse displacements. In this paper, the same kinematic description is used to derive both the elastic and the inertia terms. The classical midpoint rule is used to integrate the dynamic equations. The central idea, to ensure energy and momenta conservation, is to apply the classical midpoint rule to both the kinematic and the strain quantities. This idea, developed by one of the authors in previous work, is applied here in the context of the co-rotational formulation to the first time. By doing so, we circumvent the nonlinear geometric equations relating the displacement to the strain which is the origin of many numerical difficulties. It can be rigorously shown that the proposed method conserves the total energy of the system and, in absence of external loads, the linear and angular momenta remain constant. The accuracy and stability of the proposed algorithm, especially in long term dynamics with a very large number of time steps, is assessed through two numerical examples.
|
|
| 8. |
- Chhang, Sophy, et al.
(författare)
-
Energy-momentum method for co-rotational plane beams : A comparative study of shear flexible formulations
- 2017
-
Ingår i: Finite elements in analysis and design (Print). - : Elsevier. - 0168-874X .- 1872-6925. ; 134, s. 41-54
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an energy-momentum method for three dynamic co-rotational formulations of shear flexible 2D beams. The classical midpoint rule is applied for both kinematic and strain quantities. Although the idea as such was developed in previous work, its realization and testing in the context of co-rotational Timoshenko 2D beam elements is done here for the first time. The main interest of the method is that the total energy and momenta are conserved. The three proposed formulations are based on the same co-rotational framework but they differ in the assumptions done to derive the local formulations. Four numerical applications are used to assess the accuracy and efficiency of each formulation. In particularly, the conservation of energy with a very large number of steps and the possibility to simplify the tangent dynamic matrix are investigated.
|
|
| 9. |
- Heng, Piseth, et al.
(författare)
-
A simplified model for nonlinear dynamic analysis of steel column subjected to impact
- 2016
-
Ingår i: International Journal of Non-Linear Mechanics. - : Elsevier. - 0020-7462 .- 1878-5638. ; 86, s. 37-54
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new simplified model of the nonlinear dynamic behavior of a steel column subjected to impact loading. In this model, the impacted column, which undergoes large displacement, consists of two rigid bars connected by generalized elastic–plastic hinges where the deformation of the entire steel column as well as the connections is concentrated. The effect of the rest of the structure on the column is modeled by an elastic spring and a point masse both attached to the top end of the column which is also loaded by a compressive force. The plastification of the hinges follows the normality rule with a yield surface that accounts for the interaction between M and N. The latter is described by a super-elliptic yield surface that allows ones to consider a wide range of convex yield criterion by simply varying the roundness factor that affects the shape of the limit surface. By including these features, the model captures both geometry and material nonlinearities. Both the flow rule and the equations of motion are integrated using the midpoint scheme that conserves energy. The non-smooth nature of impact is considered by writing the equations of motion of colliding masses using differential measures. Contact conditions are written in terms of velocity and combined with Newton's law to provide the constitutive law describing interactions between masses during impact. Numerical applications show that the model is able to capture the behavior of a column subjected to impact.
|
|
| 10. |
- Le, T.-N., et al.
(författare)
-
A new 3D co-rotational beam element for nonlinear dynamic analysis
- 2015
-
Ingår i: COMPDYN 2015. - Athens : Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece. ; , s. 1087-1110
-
Konferensbidrag (refereegranskat)abstract
- The paper investigates the contribution of the warping deformations and the shear center location on the dynamic response of 3D thin-walled beams obtained with an original consistent co-rotational formulation developed by the authors. Consistency of the formulation is ensured by employing the same kinematic assumptions to derive both the static and dynamic terms. Hence, the element has seven degrees of freedom at each node and cubic shape functions are used to interpolate local transversal displacements and axial rotations. Accounting for warping deformations and the position of the shear center produces additional terms in the expressions of the inertia force vector and the tangent dynamic matrix. The performance of the present formulation is assessed by comparing its predictions against 3D-solid FE solutions.
|
|
