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Showing papers on "Bending moment published in 2015"


Journal ArticleDOI
TL;DR: In this paper, the results of flexural tests on RC beams strengthened with both NSM and EBR techniques are discussed in order to show that debonding phenomena for NSM strip strengthened beams are less significant than for EBR plate beams.

125 citations


Journal ArticleDOI
TL;DR: In this paper, the free vibration of functionally graded Timoshenko beams is investigated by developing the dynamic stiffness method, where material properties of the beam are assumed to vary continuously in the thickness direction.

118 citations


Journal ArticleDOI
TL;DR: In this paper, a test embankment constructed on a soft clayey deposit in Saga, Japan, was simulated by both three-dimensional and two-dimensional finite element analyses (FEA).

95 citations


Journal ArticleDOI
TL;DR: In this paper, the development of longitudinal joint opening with bending moment under different axial stress levels, and the longitudinal joint joint opening in the Ultimate Limit State (ULS) was investigated.

90 citations


Journal ArticleDOI
TL;DR: In this article, a generalized attempt has been made to evaluate the relative magnitudes of these four loadings by transforming them into bending moment spectra using site-specific and turbine-specific data.
Abstract: Offshore wind turbines are subjected to multiple dynamic loads arising from the wind, waves, rotational frequency (1P) and blade passing frequency (3P) loads. In the literature, these loads are often represented using a frequency plot where the power spectral densities (PSDs) of wave height and wind turbulence are plotted against the corresponding frequency range. The PSD magnitudes are usually normalized to unity, probably because they have different units, and thus, the magnitudes are not directly comparable. In this paper, a generalized attempt has been made to evaluate the relative magnitudes of these four loadings by transforming them into bending moment spectra using site-specific and turbine-specific data. A formulation is proposed to construct bending moment spectra at the mudline, i.e. at the location where the highest fatigue damage is expected. Equally, this formulation can also be tailored to find the bending moment at any other critical cross section, e.g. the transition piece level. Finally, an example case study is considered to demonstrate the application of the proposed methodology. The constructed spectra serve as a basis for frequency-domain fatigue estimation methods available in the literature

89 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present an experimental study on the seismic performance of steel-polypropylene hybrid fiber reinforced concrete (HFRC) columns, which is of vital significance to post-earthquake serviceability of structures.

80 citations


Journal ArticleDOI
TL;DR: In this article, a simple displacement field based on higher-order shear deformation theory is implemented for free vibration analysis of functionally graded metal-ceramic (FG) beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication.
Abstract: This work presents a free vibration analysis of functionally graded metal-ceramic (FG) beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. For this purpose, a simple displacement field based on higher order shear deformation theory is implemented. The proposed theory is based on the assumption that the transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. The most interesting feature of this theory is that it accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the beam without using shear correction factors. In addition, it has strong similarities with Euler-Bernoulli beam theory in some aspects such as equations of motion, boundary conditions, and stress resultant expressions. The rule of mixture is modified to describe and approximate material properties of the FG beams with porosity phases. By employing the Hamilton\'s principle, governing equations of motion for coupled axial-shear-flexural response are determined. The validity of the present theory is investigated by comparing some of the present results with those of the first-order and the other higher-order theories reported in the literature. Illustrative examples are given also to show the effects of varying gradients, porosity volume fraction, aspect ratios, and thickness to length ratios on the free vibration of the FG beams.

69 citations


Journal ArticleDOI
TL;DR: In this article, an extension of the Continuous Strength Method (CSM) is described to enable the prediction of the ultimate cross-section resistance of I-sections and box sections under combined loading.

66 citations


Journal ArticleDOI
TL;DR: In this paper, an axisymmetric numerical model is introduced that allows analyzing the role and significance of moment redistribution between hogging and sagging moments and compressive membrane action on the flexural deformations of continuous flat slabs.

62 citations


Journal ArticleDOI
TL;DR: In this article, a smart rotor configuration where Adaptive Trailing Edge Flaps (ATEF) are employed for active alleviations of the aerodynamic loads on the blades of the NREL 5 MW reference turbine is proposed.
Abstract: The paper proposes a smart rotor configuration where Adaptive Trailing Edge Flaps (ATEF) are employed for active alleviations of the aerodynamic loads on the blades of the NREL 5 MW reference turbine. The flaps extend for 20 % of the blade length, and are controlled by a Linear Quadratic (LQ) algorithm based on measurements of the blade root flapwise bending moment. The control algorithm includes frequency weighting to discourage flap activity at frequencies higher than 0.5 Hz. The linear model required by the LQ algorithm is obtained from subspace system identification; periodic disturbance signals described by simple functions of the blade azimuthal position are included in the identification to avoid biases from the periodic load variations observed on a rotating blade. The LQ controller uses the same periodic disturbance signals to handle anticipation of the loads periodic component. The effects of active flap control are assessed with aeroelastic simulations of the turbine in normal operation conditions, as prescribed by the IEC standard. The turbine lifetime fatigue damage equivalent loads provide a convenient summary of the results achieved with ATEF control: a 10 % reduction of the blade root flapwise bending moment is reported in the simplest control configuration, whereas reductions of approximately 14 % are achieved by including periodic loads anticipation. The simulations also highlight impacts on the fatigue damage loads in other parts of the structure, in particular, an increase of the blade torsion moment, and a reduction of the tower fore-aft loads.

59 citations


Journal ArticleDOI
TL;DR: In this article, the nonlocal elastostatic problem of Bernoulli-Euler nanobeams is formulated in variational terms by recognizing that the nonlocality effect is equivalent to a bending curvature distortion prescribed on a corresponding local nanobeam, subjected to the same kinematic boundary constraints and applied loads.
Abstract: Small-scale effects in nanobeams are effectively described by the Eringen model of nonlocal elasticity. The nonlocal elastostatic problem of Bernoulli–Euler nanobeams is here formulated in variational terms by recognizing that the nonlocality effect is equivalent to a bending curvature distortion prescribed on a corresponding local nanobeam, subjected to the same kinematic boundary constraints and applied loads. The conditions to be imposed for the kinematic integrability of the bending curvature field are also provided to evaluate the bending moment solution in statically indeterminate nonlocal nanobeams. Since the curvature distortion describing the nonlocality effect is kinematically integrable in statically determinate structures, bending moments do not exhibit small-scale effects in non-redundant nanobeams. The equivalence method illustrated in the present paper is resorted to for solving the nonlocal elastostatic problem of nanobeams under constant transversal load distributions.

Journal ArticleDOI
TL;DR: In this article, an analysis of the effects of random imperfections on the load carrying capacity of a hot-rolled steel beam was performed in the analytical form using the Latin Hypercube Sampling method.

Journal ArticleDOI
TL;DR: In this article, the bending moment and deflection response of a single pile under the combined influence of lateral and axial compressive loading during an earthquake, in both saturated and dry homogenous soil, and in a typical layered soil.

Journal ArticleDOI
TL;DR: In this article, the potential of the detection of flexural damage state in the lower part of the mid-span area of a simply supported reinforced concrete beam using piezoelectric sensors is analytically investigated.
Abstract: Structural health monitoring along with damage detection and assessment of its severity level in non-accessible reinforced concrete members using piezoelectric materials becomes essential since engineers often face the problem of detecting hidden damage. In this study, the potential of the detection of flexural damage state in the lower part of the mid-span area of a simply supported reinforced concrete beam using piezoelectric sensors is analytically investigated. Two common severity levels of flexural damage are examined: (i) cracking of concrete that extends from the external lower fiber of concrete up to the steel reinforcement and (ii) yielding of reinforcing bars that occurs for higher levels of bending moment and after the flexural cracking. The purpose of this investigation is to apply finite element modeling using admittance based signature data to analyze its accuracy and to check the potential use of this technique to monitor structural damage in real-time. It has been indicated that damage detection capability greatly depends on the frequency selection rather than on the level of the harmonic excitation loading. This way, the excitation loading sequence can have a level low enough that the technique may be considered as applicable and effective for real structures. Further, it is concluded that the closest applied piezoelectric sensor to the flexural damage demonstrates higher overall sensitivity to structural damage in the entire frequency band for both damage states with respect to the other used sensors. However, the observed sensitivity of the other sensors becomes comparatively high in the peak values of the root mean square deviation index.

Journal ArticleDOI
TL;DR: In this article, a set of blade-root bending moment responses for a scale-model tidal turbine subjected to an unsteady planar forcing in a towing tank is presented, where the boundary layer was believed to be attached to the outer sections of the blade.

Journal ArticleDOI
TL;DR: In this paper, the influence of different aspects of chip breaker geometry on cutting force, chip shape, and bending moment was evaluated by using finite element and experimental approaches, and the results indicated that the predicted cutting force and chip shape are in close agreement with the experimental ones.
Abstract: Control of continuous chips in turning operation is a very vital issue to enhance productivity and operator safety. A famous method to control the chip size is utilization of chip breaker. In this study, the influence of different aspects of chip breaker geometry on cutting force, chip shape, and bending moment was evaluated by using finite element and experimental approaches. Therefore, cutting tests were carried out on AISI 1045 steel using tungsten carbide inserts with various chip breaker geometries. The results indicated that the predicted cutting force and chip shape are in close agreement with the experimental ones. It is also observed that the bending moment generated by the upper level of breadth surface has the highest contribution in the development of combined and nonuniform state of stress at the root and body of deformed chip. Meanwhile, the chip breaker geometry had a significant effect on the cutting force value.

Journal ArticleDOI
TL;DR: In this paper, the structural strength and stability of cold-formed steel lipped channel beam-columns under bi-axial moments and axial force are experimentally investigated, and the results show that the failure modes are highly dependent on the stress distribution applied on the cross-section by the combined actions.
Abstract: In this paper, the structural strength and stability of cold-formed steel lipped channel beam-columns under bi-axial moments and axial force are experimentally investigated. The results are employed to evaluate the reliability of the current North American cold-formed steel design standard, AISI-S100-12, for predicting the strength of beam-columns, by both the effective width method (EWM) and the direct strength method (DSM). Fifty-five 600S137-54 (AISI-S200-12 nomenclature) lipped channel beam-column sections with three different lengths: 305 mm (short), 610 mm (intermediate), and 1219 mm (long) are tested under combined bi-axial bending moments and axial force to characterize the failure modes and the member capacity. A loading rig specifically designed to apply eccentric axial load, in order to provide bi-axial bending and compression to the specimens, was developed and detailed herein. The experimental observations reveal that the failure modes are highly dependent on the stress distribution applied on the cross-section by the combined actions. The results show a considerable potential for improvement in current specification approaches which utilize a simple interaction equation, as this typically results in conservative strength predictions. The potential for further improvement of the current specification for predicting the strength of cold-formed steel beam-columns is discussed.

Journal ArticleDOI
TL;DR: In this article, the effects of soil-structure interaction (SSI) problems on the seismic response of multi-story buildings are analyzed for typical multi-dimensional building resting on a raft foundation.
Abstract: Soil conditions have a great deal to do with damage to structures during earthquakes. Hence the investigation on the energy transfer mechanism from soils to buildings during earthquakes is critical for the seismic design of multi-story buildings and for upgrading existing structures. Thus, the need for research into soil–structure interaction (SSI) problems is greater than ever. Moreover, recent studies show that the effects of SSI may be detrimental to the seismic response of structure and neglecting SSI in analysis may lead to un-conservative design. Despite this, the conventional design procedure usually involves assumption of fixity at the base of foundation neglecting the flexibility of the foundation, the compressibility of the underneath soil and, consequently, the effect of foundation settlement on further redistribution of bending moment and shear force demands. Hence the SSI analysis of multi-story buildings is the main focus of this research; the effects of SSI are analyzed for typical multi-story building resting on raft foundation. Three methods of analysis are used for seismic demands evaluation of the target moment-resistant frame buildings: equivalent static load; response spectrum methods and nonlinear time history analysis with suit of nine time history records. Three-dimensional FE model is constructed to investigate the effects of different soil conditions and number of stories on the vibration characteristics and seismic response demands of building structures. Numerical results obtained using SSI model with different soil conditions are compared to those corresponding to fixed-base support modeling assumption. The peak responses of story shear, story moment, story displacement, story drift, moments at beam ends, as well as force of inner columns are analyzed. The results of different analysis approaches are used to evaluate the advantages, limitations, and ease of application of each approach for seismic analysis.

Journal ArticleDOI
TL;DR: In this article, a hot-rolled steel IPE-beam designed according to Eurocodes is considered and its reliability is assessed using probabilistic analysis based on the Monte Carlo method.
Abstract: .The paper deals with the analysis of reliability of a hot-rolled steel IPE-beam designed according to Eurocodes. A beam at its ultimate limit state is considered. The load acting on the beam consists of permanent and long-term single variation actions. The beam is loaded with end bending moments about the major principal axis. The beam is susceptible to lateral torsional buckling between the end supports. Reliability of the beam is assessed using probabilistic analysis based on the Monte Carlo method. Failure probability is a function of the random variability of the loadcarrying capacity and the random variability of load effects. The variability of the load-carrying capacity is influenced by the variability of initial imperfections. Imperfections are considered according to experimental research. Numerical studies showed that the failure probability is significantly misaligned. High values of failure probability were obtained for slender beams, for beams loaded only by permanent load action, an...

Journal ArticleDOI
TL;DR: In this paper, the authors presented a simplified approach to calculate the strength domains for reinforced concrete columns subjected to axial force and uniaxial bending moment, taking into account the effects of confinement with proper stress block parameters, the latter adapted for confined concrete, and of the composite action of jacket and core; buckling of longitudinal bars is considered and discussed with an appropriate stress-strain law for steel in compression.

Journal ArticleDOI
TL;DR: In this paper, a strip theory based partially nonlinear time domain code is extended to include body nonlinearity in the calculation of radiation and diffraction forces, which expresses the dependence of hydrodynamic forces on the time changing underwater hull shape.

Journal ArticleDOI
TL;DR: In this article, a physical modeling system was established to explore the fracture mechanism of the hard roof, and the characteristics of acoustic emission (AE) signals during the process of hard roof failure were also studied.
Abstract: Roof fracture has been a persistent threat to coal mine safety. In this paper, a physical modeling system was established to explore the fracture mechanism of the hard roof. The characteristics of acoustic emission (AE) signals during the process of hard roof failure were also studied. Results indicate that shear failure first occurs in the two ends of the hard roof beam due to the comprehensive effect of ground stress and mining-induced stress. After this failure occurs, the bending moment moves quickly toward the middle of the beam. This movement will cause tensile failure in the middle part of the beam. Broadband frequency signals are produced when a hard roof is fractured. When compared with AE energy, the AE count shows an increasing trend during a short period before each hard roof fracture. AE signals, especially for AE energy, increase steeply, reaching a peak value at the moment rock fracture occurs. These signals then drop rapidly, ending with a weak level until the next turn. Both the periodic characteristics and evolution process of AE signals can reflect not only the stress state but also the damage degree of the roof strata. These results could offer some thoughts and reference for forecasting and monitoring rock bursts caused by hard roof failure.

Journal ArticleDOI
Fuat Kara1
TL;DR: In this article, the numerical predictions of the hydroelasticity of floating bodies with and without forward speed are presented using a direct time domain approximation using Boundary-Integral Equation Method (BIEM) with three-dimensional transient free surface Green function and Neumman-Kelvin approximation for the solution of the hydrodynamic part and solved as impulsive velocity potential whilst Euler-Bernoulli beam approach is used for structural analysis with analytically defined modeshapes.

Journal ArticleDOI
TL;DR: In this paper, a coupled dynamic analysis of a marine riser under combined forcing excitation and parametric excitation is presented, where the forces are induced by lateral sea wave and current, and time-varying heave motion of a floating vessel respectively.

Journal ArticleDOI
TL;DR: In this article, the authors presented a FEM blind prediction of centrifuge tests on a reduced scale tunnel, where the tunnel behaviour was assumed to be visco-linear-elastic, while the soil behaviour was considered to be perfectly plastic.
Abstract: The number of tunnels in seismic regions has grown significantly in recent decades. It has usually been assumed that tunnels perform better than surface structures during seismic events. However, recent cases have shown that tunnels can be significantly damaged by seismic events. Thus, an evaluation of their response to earthquakes has become increasingly necessary. This paper presents a FEM blind prediction of centrifuge tests on a reduced scale tunnel. The main objective of the paper is to evaluate the numerical model that reproduces the response recorded in the centrifuge. The centrifuge tests involved a tunnel in dry sand. The numerical simulation was performed on the physical-scale model of the transverse direction of the tunnel, which is of prime importance, as it can show large stress–strain levels in the tunnel lining. The tunnel behaviour was assumed to be visco-linear-elastic, while the soil behaviour was assumed to be visco-elastic-perfectly plastic. The soil model parameters were calibrated on the basis of laboratory tests performed on the sand used for the test. The comparison between the experimental and numerical results is presented in terms of acceleration in the time and frequency domains. The experimental and numerical settlements of the sand surface and displacements of the sand-tunnel system, as well as the bending moments and hoop forces acting in the tunnel are also compared. Increments of the bending moments and hoop forces are also evaluated using the closed-form solution proposed by Wang (Seismic design of tunnels: a simple state-of-the-art design approach. Parson Brinckerhoff, New York, 1993) and Penzien (Earthq Eng Struct Dyn 29:683–691, 2000). A very good agreement between the experimental and numerical results is achieved in terms of horizontal acceleration time-histories and their Fourier spectra, as well as in terms of vertical displacements of the sand surface. Moderate differences exist between the experimental and numerical bending moments and hoop forces; experimental, numerical and analytical increments of the bending moments and hoop forces are in a quite good agreement with each other.

Journal ArticleDOI
TL;DR: In this paper, the authors present a proposal for the design of steel structures sensitive to lateral torsional buckling due to bending moment in order to fill the gaps in the current Standard EN 1993-1-1, guidelines for obtaining the magnitude of the imperfection.


Journal ArticleDOI
TL;DR: In this paper, a series of 1-g plane model tests and FEM analyses were carried out to investigate the influence of the layered soils in terms of their relative stiffness and thickness on the lining behavior (i.e., inner force and convergence).

Journal ArticleDOI
TL;DR: In this article, the authors derived an interface model characterized by macroscopic fracture energies which are different in modes I and II, the fracture energy being the total energy dissipated per unit of fracture area.
Abstract: The present paper deals with the derivation of an interface model characterized by macroscopic fracture energies which are different in modes I and II, the macroscopic fracture energy being the total energy dissipated per unit of fracture area. It is first shown that thermo-dynamical consistency for a model governed by a single damage variable, combined with the choice of employing an equivalent relative displacement and of a linear softening in the stress-relative displacement law, leads to the coincidence of fracture energies in modes I and II. To retrieve the experimental evidence of a greater fracture energy in mode II, a micro-structured geometry is considered at the typical point of the interface where a Representative Interface Element (RIE) characterized by a periodic arrangement of distinct inclined planes is introduced. The interaction within each of these surfaces is governed by a coupled damage-friction law. A sensitivity analysis of the correlation between micromechanical parameters and the numerically computed single-point microstructural response in mode II is reported. An assessment of the capability of the model in predicting different mixed mode fracture energies is carried out both at the single microstructural interface point level and with a structural example. For the latter a double cantilever beam with uneven bending moments has been analyzed and numerical results are compared with experimental data reported in the literature for different values of mode mixity.

Journal ArticleDOI
TL;DR: In this paper, an extensive experimental investigation is carried out on a stack of two dry-jointed tuff blocks subjected to different loading conditions implying interactions among shear, torsion and bending moments.