Abstract
A three-dimensional finite element method is used for analysis of repairing cracks in plates with bonded composite patch in elastic and elastic plastic analysis. This study was performed in order to establish an analytical model of the J-integral for repair crack. This formulation of the J-integral to establish models of fatigue crack growth in repairing aircraft structures. The model was developed by interpolation of numerical results. The obtained results were compared with those calculated with the finite element method. It was found that our model gives a good agreement of the J-integral. The arrow shape reduces the J integral at the crack tip, which improves the repair efficiency.
Key Words
composite; Finite Element Method; modelling; fracture mechanic; elastic-plastic
Address
Nassim Serier, Belaïd Mechab, Rachid Mhamdia and Boualem Serier: LMPM, Department of Mechanical Engineering, University of SidiBel Abbes, BP 89 City Ben M\'hidi 22000, SidiBel Abbes, Algeria
Abstract
The results of diagnostics and analysis of an industrial hall located on the premises of a thermal power plant severely damaged by fire are presented in the paper. The comprehensive failure-related diagnostics, non-destructive and destructive tests of steel and concrete materials, geodetic surveying of selected structural members, numerical modelling, static analysis and reliability assessment were focused on two basic goals: The determination of the current technical condition of the load bearing structure and the assessment of its post fire resistance as well as assessing the degree of damage and subsequent design of reconstruction measures and arrangements which would enable the safe and reliable use of the building. The current mechanical properties of the steel material obtained from the tests and measured geometric characteristics of the structural members with imperfections were employed in finite element models to study the post-fire behaviour of the structure. In order to compare the behaviour of the numerically modelled steel roof truss, subjected to the effects of fire, with the real post-fire response of the damaged structure theoretically obtained resistance, critical temperature and the time at which the structure no longer meets the required reliability criteria under its given loading are compared with real values. A very good agreement between the simulated results and real characteristics of the structure after the fire was observed.
Key Words
damaged industrial hall; fire effects; failure diagnostics; non-destructive and destructive tests; geodetic surveying; finite element analysis; reliability assessment; fire resistance check
Address
Stanislav Kmet, Michal Tomko, Ivo Demjan, Sergej Priganc: Institute of Structural Engineering, Faculty of Civil Engineering, Technical University of Kosice, Vysokoskolska 4, Kosice, Slovakia
Ladislav Pesekc: Department of Material Science, Faculty of Metallurgy, Technical University of Kosice, Park Komenskeho 11, Kosice, Slovakia
Abstract
Exact solutions for stresses, strains, and displacements of a perforated rectangular plate by an arbitrarily located circular hole subjected to both linearly varying in-plane normal stresses on the two opposite edges and in-plane shear stresses are investigated using the Airy stress function. The hoop stress occurring at the edge of the non-central circular hole are computed and plotted. Stress concentration factors (the maximum non-dimensional hoop stresses) depending on the location and size of the non-central circular hole and the loading condition are tabularized.
Key Words
perforated plate; arbitrarily located circular hole; hoop stress; stress concentration factor; airy stress function; in-plane linearly varying normal stresses; in-plane shear stresses
Address
Yeong-Bin Yang: MOE Key Laboratory of New Technology for Construction of Cities in Mountain Area and School of Civil Engineering, Chongqing University, Chongqing 400045, China; Department of Civil Engineering, National Taiwan University, Taipei 10617, Taiwan
Jae-Hoon Kang: Department of Architectural Engineering, Chung-Ang University, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756, Republic of Korea
Abstract
A finite element model for the non-linear dynamic analysis of a reinforced concrete (RC) containment shell of a nuclear power plant subjected to extreme loads such as impact and earthquake is presented in this work. The impact is modeled by using an uncoupled approach in which a load function is applied at the impact zone. The earthquake load is modeled by prescribing ground accelerations at the base of the structure. The nuclear containment is discretized spatially by using 20-node brick finite elements. The concrete in compression is modeled by using a modified Drücker-Prager elasto-plastic constitutive law where strain rate effects are considered. Cracking of concrete is modeled by using a smeared cracking approach where the tension-stiffening effect is included via a strain-softening rule. A model based on fracture mechanics, using the concept of constant fracture energy release, is used to relate the strain softening effect to the element size in order to guaranty mesh independency in the numerical prediction. The reinforcing bars are represented by incorporated membrane elements with a von Mises elasto-plastic law. Two benchmarks are used to verify the numerical implementation of the present model. Results are presented graphically in terms of displacement histories and cracking patterns. Finally, the influence of the shear transfer model used for cracked concrete as well as the effect due to a base slab incorporation in the numerical modeling are analyzed.
Key Words
reinforced concrete structures (RC); finite element method (FEM); impact and seismic loads
Address
Jorge Luis Palomino Tamayo: Center of Applied Mechanics and Computational (CEMACOM), Engineering School of Federal University of Rio Grande do Sul, Av. Osvaldo Aranha 99-3o Floor, 90035-190, Porto Alegre, RS, Brazil
Armando Miguel Awruch: Department of Civil Engineering, Engineering School Federal University of Rio Grande do Sul, Av. Osvaldo Aranha 99-3o Floor, 90035-190, Porto Alegre, RS, Brazil
Abstract
The Turkish Earthquake Code was revised in 1998 and 2007. Before these Codes, especially 1998, reinforced concrete (RC) beams with low flexural and shear strength were widely used in the building. In this study, the RC specimens have been produced by taking into consideration the RC beams with insufficient shear and tensile reinforcement having been manufactured with the use of concrete with low strength. The performance of the RC specimens strengthened with different wrapping methods by using of Carbon Fibre Reinforced Polymer (CFRP) and Glass Fibre Reinforced Polymer (GFRP) composites have been examined in terms of flexural strength, ductility and energy absorption capacity. In the strengthening of the RC elements, the use of GFRP composites instead of CFRP composites has also been examined. For this purpose, the experimental results of the RC specimens strengthened by wrapping with CFRP and GFRP are presented and discussed. It has been concluded that although the flexural and shear strengths of the RC beams strengthened with GFRP composites are lower than those of beams reinforced with CFRP, their ductility and energy absorption capacities are very high. Moreover, the RC beams strengthened with CFRP fracture are more brittle when compared to GFRP.
Address
Ali Saribiyik: Department of Construction Technology, Sakarya University, Sakarya, Turkey
Naci Caglar: Department of Civil Engineering, Engineering Faculty, Sakarya University, Sakarya, Turkey
Abstract
In this study, the free vibration analysis of axially moving beams is investigated according to Reddy-Bickford beam theory (RBT) by using dynamic stiffness method (DSM) and differential transform method (DTM). First of all, the governing differential equations of motion in free vibration are derived by using Hamilton\'s principle. The nondimensionalised multiplication factors for axial speed and axial tensile force are used to investigate their effects on natural frequencies. The natural frequencies are calculated by solving differential equations using analytical method (ANM). After the ANM solution, the governing equations of motion of axially moving Reddy-Bickford beams are solved by using DTM which is based on Finite Taylor Series. Besides DTM, DSM is used to obtain natural frequencies of moving Reddy-Bickford beams. DSM solution is performed via Wittrick-Williams algorithm. For different boundary conditions, the first three natural frequencies that calculated by using DTM and DSM are tabulated in tables and are compared with the results of ANM where a very good proximity is observed. The first three mode shapes and normalised bending moment diagrams are presented in figures.
Key Words
axially moving beam; Reddy-Bickford beam theory; dynamic stiffness method; differential transform method; free vibration analysis; natural frequency
Address
Baran Bozyigit and Yusuf Yesilce: Department of Civil Engineering, Dokuz Eylul University, 35160, Buca, Izmir, Turkey
Abstract
Non-Deformable Support System (NDSS) is one of the support system analysis methods. It is likely seen as numerical analysis. Obviously, numerical modeling is the key tool for this system but not unique. Although the name of the system makes you feel that there is no deformation on the support system, it is not true. The system contains some deformation but in certain tolerance determined by the numerical analyses. The important question is what is the deformation tolerance? Zero deformation in the excavation
environment is not the case, actually. However, deformation occurred after supporting is important. This deformation amount will determine the performance of the applied support. NDSS is a stronghold analysis method applied in full to make this work. While doing this, NDSS uses the properties of rock mass and material, various rock mass failure criteria, various material models, different excavation geometries, like other methods. The thing that differ NDSS method from the others is that NDSS makes analysis using the time dependent deformation properties of rock mass and engineering judgement. During the evaluation process, NDSS gives the permission of questioning the field observations, measurements and timedependent support performance. These transactions are carried out with 3-dimensional numeric modeling analysis. The goal of NDSS is to design a support system which does not allow greater deformation of the support system than that calculated by numerical modeling. In this paper, NDSS applied to the problems of Tunnel 34 of the same Project (excavated with NATM method, has a length of 2218 meters), which is driven in graphite schist, was illustrated. Results of the system analysis and insitu measurements successfully coincide with each other.
Key Words
non-deformable support system; weak rock mass; tunneling; tunnel support; support analysis
Address
C.O. Aksoy: Department of Mining Engineering, Dokuz Eylul University, Izmir, Turkey
G.G. Uyar: Department of Mining Engineering, Hacettepe University, Ankara, Turkey
E. Posluk, K. Ogul: Turkish Republic National Railway, Eskişehir, Turkey
I. Topal: Department of Mining Engineering, Dumlupinar University, Kutahya, Turkey
Abstract
This study analyses the seismic response of a three-dimensional (3-D) rigid massless square foundation resting or embedded in a viscoelastic soil limited by rigid bedrock. The foundation is subjected to harmonic oblique seismic waves P, SV, SH and R. The key step is the characterization of the soil-foundation interaction by computing the impedance matrix and the input motion matrix. A 3-D frequency boundary element method (BEM) in conjunction with the thin layer method (TLM) is adapted for the seismic analysis of the foundation. The dynamic response of the rigid foundation is solved from the wave equations by taking into account the soil-foundation interaction. The solution is formulated using the frequency BEM with the Green
Key Words
harmonic seismic waves; foundation; soil; BEM-TLM; soil-structure interaction
Address
Salah Messioud: LGCE, University of Jijel, BP 98 Jijel 18000, Republic of Algeria
Badreddine Sbartai: Department of Civil Engineering, University of Annaba, BP 25, Annaba 23000, Republic of Algeria; LMGHU Laboratory, University of Skikda, Road El-hadeik BP 26, Skikda 21000, Republic of Algeria
Daniel Dias: 3SR Laboratory, University of Joseph Fourier, Grenoble 38000, Republic of France
Abstract
This paper assesses efficiency of the continuum method as the idealized system of building structures. A modified Coupled Two-Beam (CTB) model equipped with classical and non-classical damping has been proposed and solved analytically. In this system, complementary (non-classical) damping models composed of bending and shear mechanisms have been defined. A spatial shear damping model which is non-homogeneously distributed has been adopted in the CTB formulation and used to equivalently model passive dampers, viscous and viscoelastic devices, embedded in building systems. The application of continuum-based models for the dynamic analysis of shear wall systems has been further discussed. A reference example has been numerically analyzed to evaluate the efficiency of the presented CTB, and the optimization problems of the shear damping have been finally ascertained using local and global performance indices. The results reveal the superior performance of non-classical damping models against the classical damping. They show that the critical position of the first modal rotation in the CTB is reliable as the optimum placement of the shear damping. The results also prove the good efficiency of such a continuum model, in addition to its simplicity, for the fast estimation of dynamic responses and damping optimization issues in building systems.
Key Words
building structural systems; continuum model; replacement beam (RB); coupled two-beam (CTB); classical damping; non-classical damping; passive damping
Address
Hadi Moghadasi Faridani: Department of Civil and Environmental Engineering, Politecnico di Milano, 32 Leonadro da Vinci, Milan, 20133, Italy
Antonio Capsoni: Department of Architecture, Built Environment and Construction Engineering, Politecnico di Milano, 32 Leonadro da Vinci, Milan, 20133, Italy
Abstract
The effects of nanotechnology and smartness on the buckling reduction of pipes are the main contributions of present work. For this ends, the pipe is simulated with classical piezoelectric polymeric cylindrical shell reinforced by armchair double walled boron nitride nanotubes (DWBNNTs), The structure is subjected to combined electro-thermo-mechanical loads. The surrounding elastic foundation is modeled with a novel model namely as orthotropic nonhomogeneous Pasternak medium. Using representative volume element (RVE) based on micromechanical modeling, mechanical, electrical and thermal characteristics of the equivalent composite are determined. Employing nonlinear strains-displacements and stress-strain relations as well as the charge equation for coupling of electrical and mechanical fields, the governing equations are derived based on Hamilton\'s principal. Based on differential quadrature method (DQM), the buckling load of pipe is calculated. The influences of electrical and thermal loads, geometrical parameters of shell, elastic foundation, orientation angle and volume percent of DWBNNTs in polymer are investigated on the buckling of pipe. Results showed that the generated O improved sensor and actuator applications in several process industries, because it increases the stability of structure. Furthermore, using nanotechnology in reinforcing the pipe, the buckling load of structure increases.
Key Words
nanotechnology; smartness; pipe; piezoelectric; orthotropic nonhomogeneous Pasternak medium
Address
Farhad Mosharrafian and Reza Kolahchi: Department of Civil Engineering, Khomein Branch, Islamic Azad University, Khomein, Iran
