scholarly journals STRUCTURAL FIRE BEHAVIOUR OF Z PURLINS

2016 ◽  
Author(s):  
Ivo Schwarz ◽  
Martin Slatinka ◽  
Michal Jandera
Keyword(s):  
Shell Element ◽  
Fe Model ◽  
Structural Members ◽  
Engineering Model ◽  
Fire Behaviour ◽  
Design Standard ◽  
Secondary Load ◽  
Practical Engineering ◽  
Bending Capacity ◽  
Thin Walled

Cold-formed sections are very common and efficient as secondary load-caring structural members. But the current European design standard EN 1993-1-2 sets the limiting temperature for the Class 4 sections to 350°C which is generallyvery conservative approach.This paper is focused on the thin-walled profilebehaviourin case offire. In particular, the paper describes transition from the beam to fibre behaviour of a Z purlin. A sophisticated shell element FE model is shown and compared to the test. Later, a more practical (Engineering) model neglecting the bending stiffness entirely is made and compared to the previous results. The conclusions show, that such simplified description of real behaviour is possible to be used after the bending capacity of the member is exceeded and predicts the forces to connection well.

Design for Crashworthiness of Vehicle Structures via Equivalent Mechanism Approximations and Crush Mode Matching

2004 ◽  
Author(s):  
Karim Hamza ◽  
Kazuhiro Saitou
Keyword(s):  
Cross Sections ◽  
Surrogate Model ◽  
Time History ◽  
Fe Model ◽  
Structural Members ◽  
Direct Optimization ◽  
Nonlinear Springs ◽  
Crashworthiness Design ◽  
Thin Walled ◽  
Equivalent Mechanism

This paper presents a 3D extension to our previous work on vehicle crashworthiness design that utilizes “equivalent” mechanism models of vehicle structures as a tool for the early design exploration. An equivalent mechanism (EM) is a network of rigid links with lumped masses connected by prismatic and revolute joints with nonlinear springs, which approximate aggregated behaviors of structural members during crush. A number of finite element (FE) models of thin-walled beams with typical cross sections and wall thicknesses are analyzed to build a surrogate model that maps the beam dimensions to nonlinear spring properties. Using the surrogate model, an EM model is optimized for given design objectives by selecting the nonlinear springs among the ones realizable by thin-walled beams. The optimum EM model serves to identify a good crash mode (CM), the time history of collapse of the structural members, and to suggest the dimensions of the structural members to attain it. After the optimization, the FE model of an entire structure is “assembled” from the suggested dimensions, which is further modified to attain the good CM identified by the optimum EM model. A case study of a 3D vehicle front half body demonstrates that the proposed approach can help obtain good designs with far less computational resources than the direct optimization of a FE model.

Numerical Simulation of Automotive Crash-Box Subjected to Low Velocity Frontal Impact

2009 ◽  
Vol 417-418 ◽  
pp. 17-20 ◽  
Author(s):  
Qing Fen Li ◽  
Yan Jie Liu ◽  
Hai Dou Wang ◽  
Sheng Yuan Yan
Keyword(s):  
Energy Absorption ◽  
Cross Section ◽  
Large Strain ◽  
Circular Cross Section ◽  
Shell Element ◽  
Fe Model ◽  
Frontal Impact ◽  
Low Velocity ◽  
Fe Method ◽  
Thin Walled

Thin walled tubes, particularly those of square or circular cross-section, are the common types of automobile crash-box, which equipped at the front end of a car, is one of the most important automotive parts for crash energy absorption. In the present work, energy absorption characters of square and circular cross-section thin walled tubes at low-velocity frontal impact are investigated respectively by using finite element (FE) method. The numerical simulations were carried out using the software LS-DYNA. The tubes were modeled using shell element of designation Belytschko-Tsay, which is suitable for large strain analyses. The FE model of the tube was validated by comparing the theoretical calculation results, experimental results and FE model results. Results show that on average the difference of these results was within 10%. The good correlation of results obtained show that the numerical analyses are reliable.

scholarly journals Vision-Based Structural FE Model Updating Using Genetic Algorithm

2021 ◽  
Vol 11 (4) ◽  
pp. 1622
Author(s):  
Gun Park ◽  
Ki-Nam Hong ◽  
Hyungchul Yoon
Keyword(s):  
Genetic Algorithm ◽  
Model Updating ◽  
Structural Parameters ◽  
Fe Model ◽  
Structural Members ◽  
Stiffness Reduction ◽  
Before And After ◽  
Scale Test ◽  
Fe Model Updating ◽  
Story Building

Structural members can be damaged from earthquakes or deterioration. The finite element (FE) model of a structure should be updated to reflect the damage conditions. If the stiffness reduction is ignored, the analysis results will be unreliable. Conventional FE model updating techniques measure the structure response with accelerometers to update the FE model. However, accelerometers can measure the response only where the sensor is installed. This paper introduces a new computer-vision based method for structural FE model updating using genetic algorithm. The system measures the displacement of the structure using seven different object tracking algorithms, and optimizes the structural parameters using genetic algorithm. To validate the performance, a lab-scale test with a three-story building was conducted. The displacement of each story of the building was measured before and after reducing the stiffness of one column. Genetic algorithm automatically optimized the non-damaged state of the FE model to the damaged state. The proposed method successfully updated the FE model to the damaged state. The proposed method is expected to reduce the time and cost of FE model updating.

scholarly journals Large deflection and post-buckling of thin-walled structures by finite elements with node-dependent kinematics

2020 ◽  
Author(s):  
E. Carrera ◽  
◽  
A. Pagani ◽  
R. Augello
Keyword(s):  
Finite Elements ◽  
Large Deflection ◽  
Nonlinear Problems ◽  
Structural Domain ◽  
Fe Model ◽  
Efficient Manner ◽  
Cross Sectional ◽  
Thin Walled Structures ◽  
Post Buckling ◽  
Thin Walled

AbstractIn the framework of finite elements (FEs) applications, this paper proposes the use of the node-dependent kinematics (NDK) concept to the large deflection and post-buckling analysis of thin-walled metallic one-dimensional (1D) structures. Thin-walled structures could easily exhibit local phenomena which would require refinement of the kinematics in parts of them. This fact is particularly true whenever these thin structures undergo large deflection and post-buckling. FEs with kinematics uniform in each node could prove inappropriate or computationally expensive to solve these locally dependent deformations. The concept of NDK allows kinematics to be independent in each element node; therefore, the theory of structures changes continuously over the structural domain. NDK has been successfully applied to solve linear problems by the authors in previous works. It is herein extended to analyze in a computationally efficient manner nonlinear problems of beam-like structures. The unified 1D FE model in the framework of the Carrera Unified Formulation (CUF) is referred to. CUF allows introducing, at the node level, any theory/kinematics for the evaluation of the cross-sectional deformations of the thin-walled beam. A total Lagrangian formulation along with full Green–Lagrange strains and 2nd Piola Kirchhoff stresses are used. The resulting geometrical nonlinear equations are solved with the Newton–Raphson linearization and the arc-length type constraint. Thin-walled metallic structures are analyzed, with symmetric and asymmetric C-sections, subjected to transverse and compression loadings. Results show how FE models with NDK behave as well as their convenience with respect to the classical FE analysis with the same kinematics for the whole nodes. In particular, zones which undergo remarkable deformations demand high-order theories of structures, whereas a lower-order theory can be employed if no local phenomena occur: this is easily accomplished by NDK analysis. Remarkable advantages are shown in the analysis of thin-walled structures with transverse stiffeners.

scholarly journals Rocking Behaviour of Multi-Block Columns Subjected to Pulse-Type Ground Motion Accelerations

2016 ◽  
Vol 10 (1) ◽  
pp. 150-157 ◽  
Author(s):  
Giovanni Minafò ◽  
Giuseppina Amato ◽  
Lorenzo Stella
Keyword(s):  
Ground Motion ◽  
Numerical Approach ◽  
Structural Members ◽  
Cross Sectional ◽  
Practical Engineering ◽  
Pulse Type ◽  
Single Block ◽  
The Individual ◽  
Acceleration Record ◽  
Rocking Response

Ancient columns, made with a variety of materials such as marble, granite, stone or masonry are an important part of the European cultural heritage. In particular columns of ancient temples in Greece and Sicily which support only the architrave are characterized by small axial load values. This feature together with the slenderness typical of these structural members clearly highlights as the evaluation of the rocking behaviour is a key aspect of their safety assessment and maintenance. It has to be noted that the rocking response of rectangular cross-sectional columns modelled as monolithic rigid elements, has been widely investigated since the first theoretical study carried out by Housner (1963). However, the assumption of monolithic member, although being widely used and accepted for practical engineering applications, is not valid for more complex systems such as multi-block columns made of stacked stone blocks, with or without mortar beds. In these cases, in fact, a correct analysis of the system should consider rocking and sliding phenomena between the individual blocks of the structure. Due to the high non-linearity of the problem, the evaluation of the dynamic behaviour of multi-block columns has been mostly studied in the literature using a numerical approach such as the Discrete Element Method (DEM). This paper presents an introductory study about a proposed analytical-numerical approach for analysing the rocking behaviour of multi-block columns subjected to a sine-pulse type ground motion. Based on the approach proposed by Spanoset al.(2001) for a system made of two rigid blocks, the Eulero-Lagrange method to obtain the motion equations of the system is discussed and numerical applications are performed with case studies reported in the literature and with a real acceleration record. The rocking response of single block and multi-block columns is compared and considerations are made about the overturning conditions and on the effect of forcing function’s frequency.

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