scholarly journals PARAMETERS AFFECTING THE STRUCTURAL ANALYSIS OF A TUNNEL STRUCTURE EXPOSED TO FIRE

2016 ◽  
Vol 7 ◽  
pp. 48
Author(s):  
Omid Pouran ◽  
Reinhard Harte ◽  
Carsten Peter
Keyword(s):  
Structural Analysis ◽  
Structural Model ◽  
Elevated Temperatures ◽  
Thermal Analyses ◽  
Material Model ◽  
Realistic Model ◽  
Structural Behaviour ◽  
Polypropylene Fibres ◽  
Concrete Mixtures ◽  
Strain Model

Behaviour of cut-and-cover tunnels exposed to fire should be analysed by using a realistic structural model that takes account of mechanical and thermal effects on the structure. This has been performed with the aid of Finite Element (FE) software package called SOFiSTiK in parallel, for two types of elements as a scope of research project financed by the German Bundesanstalt für Straßenwesen BAST. Since the stiffness of the structure at elevated temperatures is highly affected, a realistic model of structural behaviour of the tunnel could be only achieved by considering the nonlinear analysis of the structure. This has been performed for a 2–cell cut and cover tunnel by taking account of simultaneous reduction of stiffness and strength and the time-dependent increasing indirect effects due to axial constraints and temperature gradients induced by elevated temperatures. The thermal analyses have been performed and the effects were implemented into the structural model by the multi-layered strain model. The stress–strain model proposed by EN 1992-1-2 is implemented for the elevated temperature. Since there was sufficient amount of Polypropylene fibres in the concrete mixtures, modelling of spalling was excluded from the analysis. The critical corresponding stresses and material behaviour are compared and interpreted at different time stages. The main parameters affecting the accuracy and convergence of the results of structural analysis for the used model are identified: defining a realistic fire action, using concrete material model fulfilling the requirements of fire situation in tunnels, defining appropriate time intervals for load implementations. These parameters along with other parameters, which influence the results to a lesser degree, are identified and investigated in this paper.

scholarly journals Model Analysis and Optimization of BIM Technology in High-rise Shear Wall Residential Structure

2019 ◽  
Vol 267 ◽  
pp. 02001
Author(s):  
Liangli Xiao ◽  
Yan Liu ◽  
Zhuang Du ◽  
Zhao Yang ◽  
Kai Xu
Keyword(s):  
Structural Analysis ◽  
Collaborative Design ◽  
Structural Model ◽  
Structural Information ◽  
Shear Wall ◽  
Structure Design ◽  
Secondary Development ◽  
Optimized Design ◽  
Analysis Model ◽  
High Rise

This study combines specific high-rise shear wall residential projects with the Revit to demonstrate BIM application processes. The use of R-Star CAD may help to realize the link barrier of the building information model and the structural analysis software PKPM. Sequentially, the information supplement of the structural analysis model is completed by extracting the structural information with the Revit secondary development. By the collaborative design platform based on BIM technology, the paper examines the collision check of structural model, conducts collision analysis on other professional models and modifies the design scheme for conflict points. After the statistics of material usage, an optimized design is proposed. The findings of this paper could contribute to provide some reference for the specific application of BIM in structural design and realize the application of BIM technology in the process of building structure design.

Thermo-structural analysis of cryogenic tanks with common bulkhead configuration

2021 ◽  
pp. 095441002110247
Author(s):  
S Sumith ◽  
R Ramesh Kumar
Keyword(s):  
Structural Analysis ◽  
Temperature Gradient ◽  
Thermal Gradient ◽  
Load Transfer ◽  
Thermal Analyses ◽  
Positive Margin ◽  
Heat Transfer Analysis ◽  
Liquid Oxygen ◽  
Launch Vehicles ◽  
Element Analysis

In launch vehicles, cryogenic propulsion stages store liquid oxygen (LOX) at 76 K and liquid hydrogen (LH2) at 20 K, generally in two separate insulated tanks connected through tubular truss components. Consequently, load transfer from the LH2 tank to the LOX tank is very much localized, resulting in a nonoptimal design. This article presents an alternative single tankage design using a common bulkhead (CBH) to enhance the payload capability, which enables maintaining LH2 temperature within a specified temperature when exposed to a temperature gradient. A sandwich insulator using aramid honeycomb embedded with polyimide foam keeps the LH2 temperature within 20 ± 1 K is proposed, based on transient heat transfer analysis for 1000 s. The foam-filled honeycomb core is treated as equivalent foam in the analysis as the thermal conductivity of the core and the foam is quite close. The efficacy of the insulator is established by an experiment to measure the back wall temperature when liquid nitrogen is loaded on the top skin of the panel, and the insulator maintains a temperature gradient of 123 K for 1000 s. A good agreement is obtained between the transient finite element analysis results with experimental data. An externally insulated LOX tank configuration with an optimum length of the skirt–cylinder where the temperature reaches 80 K is arrived at based on slosh, buckling, and thermal analyses. No thermal gradient is found across the thickness of the skirt, while the thermal gradient is observed along the length of the skirt as anticipated. An integrated thermo-structural analysis of the cryo-system is carried out considering temperature-dependent material properties. A positive margin for the skirt is obtained. A payload gain of 366 kg is estimated based on the present study for the new design option with a CBH and skirt as compared to the traditional tubular truss arrangements.

Polycrystal Simulations Investigating the Effect of Additional Slip System Availability in a 6063 Aluminum Alloy at Elevated Temperature

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Antoinette M. Maniatty ◽  
David J. Littlewood ◽  
Jing Lu
Keyword(s):  
Aluminum Alloy ◽  
Elevated Temperature ◽  
Compression Test ◽  
Elevated Temperatures ◽  
Material Model ◽  
Grain Structure ◽  
Slip Systems ◽  
Modeling Framework ◽  
Element Analysis ◽  
6063 Aluminum Alloy

In order to better understand and predict the intragrain heterogeneous deformation in a 6063 aluminum alloy deformed at an elevated temperature, when additional slip systems beyond the usual octahedral slip systems are active, a modeling framework for analyzing representative polycrystals under these conditions is presented. A model polycrystal that has a similar microstructure to that observed in the material under consideration is modeled with a finite element analysis. A large number of elements per grain (more than 1000) are used to capture well the intragranular heterogeneous response. The polycrystal model is analyzed with three different sets of initial orientations. A compression test is used to calibrate the material model, and a macroscale simulation of the compression test is used to define the deformation history applied to the model polycrystal. In order to reduce boundary condition effects, periodic boundary conditions are applied to the model polycrystal. To investigate the effect of additional slip systems expected to be active at elevated temperatures, the results considering only the 12 {111}⟨110⟩ slip systems are compared to the results with the additional 12 {110}⟨110⟩ and {001}⟨110⟩ slip systems available (i.e., 24 available slip systems). The resulting predicted grain structure and texture are compared to the experimentally observed grain structure and texture in the 6063 aluminum alloy compression sample as well as to the available data in the literature, and the intragranular misorientations are studied.

scholarly journals Determining the material model at elevated temperatures with different strain rates and simulating the warm forming process for Mg alloy AZ31B sheet

2015 ◽  
Vol 18 (2) ◽  
pp. 149-158
Author(s):  
Thien Tich Truong ◽  
Long Thanh Nguyen ◽  
Binh Nguyen Thanh Vu ◽  
Hien Thai Nguyen
Keyword(s):  
Magnesium Alloy ◽  
Constitutive Equations ◽  
Elevated Temperatures ◽  
Material Model ◽  
Alloy Sheet ◽  
Strain Rates ◽  
Functional Requirements ◽  
Temperature Dependent ◽  
Forming Process ◽  
Az31b Alloy

Magnesium alloy is one of lightweight alloys has been studied more extensively today. Because weight reduction while maintaining functional requirements is one of the major goals in industries in order to save materials, energy and costs, etc. Its density is about 2/3 of aluminum and 1/4 of steel.The material used in this study is commercial AZ31B magnesium alloy sheet which includes 3% Al and 1% Zn. However, due to HCP (Hexagonal Close Packed) crystal structure, magnesium alloy has limited ductility and poor formability at room temperature. But its ductility and formability will be improved clearly at elevated temperature. From the data of tensile testing, the constitutive equations of AZ31B was approximated using the Ramgberg-Osgood model with temperature dependent parameters to fit in the experiment results in tensile test. Yield locus are also drawn in plane stress σ1- σ2 with different yield criteria such as Hill48, Drucker Prager, Logan Hosford, Y. W. Yoon 2013 and particular Barlat 2000 criteria with temperature dependent parameters. Applying these constitutive equations were determined at various temperatures and different strain rates, the finite element simulation stamping process for AZ31B alloy sheet by software PAM- STAMP 2G 2012, to verify the model materials and the constitutive equations.

scholarly journals Tests on Pretrained Superelastic NiTi Shape Memory Alloy Rods: Towards Application in Self-Centering Link Beams

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Xian Xu ◽  
Guangming Cheng ◽  
Junhua Zheng
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Strain Amplitude ◽  
Loading Rate ◽  
Mechanical Performance ◽  
Material Model ◽  
Niti Shape Memory Alloy ◽  
Test Results ◽  
Potential Applications ◽  
Strain Model

Austenitic shape memory alloy has potential applications in self-centering seismic resistant structural systems due to its superelastic response under cyclic tension. Raw austenitic SMA needs proper pretreatments and pretraining to gain a stable superelastic property. In this paper, tests are carried out to investigate the effects of pretraining, pretreatments, loading rate, and strain amplitude on the mechanical performance on austenitic SMA rods with a given size. The tested rods are to be used in a new concept self-centering steel link beam. Customized pretraining scheme and heat treatment are determined through the tests. The effects of loading rate and strain amplitude are investigated. A simplified stress-strain model for the SMA rods oriented to numerical simulations is obtained based on the test results. An example of using the simplified material model in numerical analysis of a self-centering steel link beam is conducted to validate the applicability of the model.

Structural behaviour of water sloshing damper with embossments subject to random excitation

2004 ◽  
Vol 31 (1) ◽  
pp. 120-132 ◽  
Author(s):  
Young-Kyu Ju
Keyword(s):  
Standard Deviation ◽  
Vibration Control ◽  
Structural Model ◽  
Structural Characteristics ◽  
Damping Ratio ◽  
Tall Buildings ◽  
Random Excitation ◽  
Water Tank ◽  
Structural Behaviour ◽  
Peak Displacement

To improve the serviceability of tall buildings, several types of vibration control systems have been developed. The tuned liquid damper (TLD) has advantages, such as simple adjustment of natural frequency, easy installation, and low maintenance. Since water tanks at the top of tall buildings can be directly modeled as a TLD system, it is more practical than any other vibration control system in Korea. Since most of the tanks in Korea have embossments on the wall, the structural characteristics are different from those of tanks used in other countries. As the damping ratio of the TLD depends on several factors, such as the magnitude and frequency of applied load, the shape of the tank, wall roughness, and so forth, it is difficult to evaluate the control performance of the tank exactly. In this study, the characteristics of the water sloshing damper with embossments (WSDE) are evaluated and the equation for equivalent damping ratio is proposed. To clarify the damping effect of a high-rise building with a damping device subject to random excitation, an experiment of a coupled structural model with a water tank was conducted. The parameters were mass ratio of water to model structure, number of wire screens, and shape factor of the water tank. The peak displacement, acceleration response, and standard deviation of the experimental results are analyzed. The coupled structural model with a water tank shows lower maximum and standard deviation responses than those of the structural model alone.Key words: water sloshing damper with embossment, vibration control, structural test, tall buildings.

An Alternate Approach to SHPB Tests to Compute Johnson-Cook Material Model Constants for 97 WHA at High Strain Rates and Elevated Temperatures Using Machining Tests

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Chithajalu Kiran Sagar ◽  
Amrita Priyadarshini ◽  
Amit Kumar Gupta ◽  
Tarun Kumar ◽  
Shreya Saxena
Keyword(s):  
Finite Element ◽  
High Strain Rate ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
High Strain ◽  
Optimization Technique ◽  
Material Model ◽  
Computational Techniques ◽  
Fe Model

Abstract With advances in computational techniques, numerical methods such as finite element method (FEM) are gaining much of the popularity for analysis as these substitute the expensive trial and error experimental techniques to a great extent. Consequently, selection of suitable material models and determination of precise material model constants are one of the prime concerns in FEM. This paper presents a methodology to determine the Johnson-Cook constitutive equation constants (JC constants) of 97 W Tungsten heavy alloys (WHAs) under high strain rate conditions using machining tests in conjunction with Oxley’s predictive model and particle swarm optimization (PSO) algorithm. Currently, availability of the high strain rate data for 97 WHA are limited and consequently, JC constants for the same are not readily available. The overall methodology includes determination of three sets of JC constants, namely, M1 and M2 from the Split-Hopkinson pressure bar (SHPB) test data available in literature by using conventional optimization technique and artificial bee colony (ABC) algorithm, respectively. However, M3 is determined from machining tests using inverse identification method. To validate the identified JC constants, machining outputs (cutting forces, temperature, and shear strain) are predicted using finite element (FE) model by considering M1, M2, and M3 as input under different cutting conditions and then validated with corresponding experimental values. The predicted outputs obtained using JC constants M3 closely matched with that of the experimental ones with error percentage well within 10%.

Historical Analysis and Structural Monitoring Cases – Studies for an Integrated Approach

2010 ◽  
Vol 133-134 ◽  
pp. 247-252
Author(s):  
Laura Balboni ◽  
Paolo Corradini ◽  
Davide Del Curto ◽  
Luca Valisi
Keyword(s):  
Structural Analysis ◽  
Historical Analysis ◽  
Integrated Approach ◽  
Historical Evolution ◽  
Structural Behaviour ◽  
The North ◽  
Single Structure ◽  
Long Time ◽  
History Of ◽  
The Relationship

The paper focuses on the structural analysis of monumental buildings, particularly upon the relationship between both instrumental measurements and the preliminary studies and the general comprehension of the construction history of each single building, including e.g. the historical evolution, materials, decay. A couple of case – study in the north of Italy are presented: the Trostburg Castle in South Tyrol and the S. Agata Church in Brescia. In these cases, cracks have been controlled by a long - time monitoring to investigate if structural damages could be influenced by the construction of underground galleries just near their foundations. The study focuses on the structural analysis of monumental buildings, particularly upon the relationship between both instrumental measurements and the preliminary studies and the general comprehension of the construction history of each single building, including e.g. the historical evolution, materials, decay. Collected data are discussed in comparison with the different approaches related to the knowledge of buildings, in order to evaluate limits and possibilities of proposed methods. Results underline how a deep investigation of an ancient and complex building, usually made up by a long time process of transformations and stratifications, allows to better understand the general structural behaviour. The strong comprehension of the constructive history of each single structure and a carefully discussed cracks board can provide a wider support to plan and make the diagnostic and structural investigation, e.g. this method helps in the choice of the type of tests and instrumentation to be employed and helps to localise where measurements should be taken, empowering the effectiveness of the results. Moreover, it allows to control and to understand results.

Modelling of grey cast iron for application to brake discs for heavy vehicles

2016 ◽  
Vol 231 (1) ◽  
pp. 35-49 ◽  
Author(s):  
Gaël Le Gigan ◽  
Magnus Ekh ◽  
Tore Vernersson ◽  
Roger Lundén
Keyword(s):  
Cast Iron ◽  
Elevated Temperatures ◽  
Kinematic Hardening ◽  
Frictional Heating ◽  
Material Model ◽  
Tensile Tests ◽  
Brake Disc ◽  
Brake Discs ◽  
Different Temperatures ◽  
Tension And Compression

Cast iron brake discs are commonly used in the automotive industry, and efforts are being made to gain a better understanding of the thermal and mechanical phenomena occurring at braking. The high thermomechanical loading at braking arises from interaction between the brake disc and the brake pads. Frictional heating generates elevated temperatures with a non-uniform spatial distribution often in the form of banding or hot spotting. These phenomena contribute to material fatigue and wear and possibly also to cracking. The use of advanced calibrated material models is one important step towards a reliable analysis of the mechanical behaviour and the life of brake discs. In the present study, a material model of the Gurson–Tvergaard–Needleman type is adopted, which accounts for asymmetric yielding in tension and compression, kinematic hardening effects, viscoplastic response and temperature dependence. The material model is calibrated using specimens tested in uniaxial cyclic loading for six different temperatures ranging from room temperature to 650 °C. A special testing protocol is followed which is intended to activate the different features of the material model. Validation of the model is performed by using tensile tests and thermomechanical experiments. An application example is given where a 10° sector of a brake disc is analysed using the commercial finitie element code Abaqus under a uniformly applied heat flux on the two friction surfaces. The results indicate that the friction surface of the hat side and the neck can be critical areas with respect to fatigue for the uniform heating studied.

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