Beam Walls Research Articles

Reducing skid marks on steel slabs by developing an improved design scheme of water beam

Due to the existence of cooling water pipes and thermoduric skids in the walking beam type reheating furnace, skid marks always occur on the bottom of the steel slab and the quality of the steel slab is seriously affected. In this paper, the coupled heat transfer model among steel slab, water beam, furnace gas and furnace walls is established to accurately simulate the reheating process of the steel slab. The discrete ordinates method (DOM) is adopted to solve radiative heat transfer problem in reheating furnace. To get closer to the real situation, the relative movement between steel slab and thermoduric skid is taken into account strictly. The formation process of skid mark is clarified based on the calculated results of coupled heat transfer, and an improved design scheme for water beam is proposed to make the new skid marks produced after water beam dislocation not overlap each other, which effectively reduces the skid marks. Our study can provide helpful advising for the improvement of steel slab quality and the design of water beam structure in reheating furnace.

Seismic behaviour of connections between replaceable coupling beam and double skin composite shear wall

In order to optimize the performance of hybrid coupled wall system, a novel of connections between replaceable coupling beam (RCB) and double skin composite shear walls (DSCSWs) are proposed. The seismic design of RCB-to-DSCSW connection is very important for structural safety. This study investigates the seismic behaviour of RCB-to-DSCSW connections. Two specimens with different layout schemes of embedded rebars and one with embedded steel I-beam were subjected to reversed cyclic loading. The failure process of all the specimens was basically the same, mainly by steel faceplate local buckling, weld tensile fracturing and the concrete crushing at both ends of the joint. The strength and ductility of connections were highly affected by the weld tensile fracturing and concrete crushing. At the current loading level or the next loading level of weld tensile fractured, the connection specimens reached its peak loading capacity, and then the concrete rapidly crushed. The ductility coefficients of all the specimens were smaller than those of RC structures. In addition, the mechanical properties of these two kinds of embedded rebar connections were similar. The steel I-beam connection exhibited higher initial stiffness. Under the same rotation of loading, the cumulative energy consumption of the steel beam was higher. Finally, according to the stress pattern of each component, the simplified mechanical model and calculation formulae of the connection bearing capacity were developed.

Seismic performance and numerical analysis of steel plate-fiber reinforced concrete composite coupling beams

To improve the seismic performance of reinforced concrete coupling beams with small span-to-height ratio, a steel plate-fiber reinforced concrete coupling beam is proposed in this paper. Quasi-static tests of a steel plate-fiber reinforced concrete composite coupling beam and a steel plate-reinforced concrete composite coupling beam have been completed. Seismic performance metrics such as failure process and bearing capacity were analyzed. Finite element software was used to analyze the stress development of concrete, steel plates, and steel rods coupled to beams under three operating conditions, as well as the distribution laws of axial forces, shear forces, and bending moments of the embedded plates. The results show that steel plate - fiber reinforced concrete coupling beam has high bearing capacity, energy dissipation capacity and ductility. The addition of fibers effectively controls the expansion of the initial cracks in the concrete and works better with steel plates. The maximum stress of the embedded steel plate is at the junction of the beam walls. The axial force of the coupling beam steel plate is U-shaped, which is subjected to a large axial force at the end and the minimum axial force in the middle, but the shear force at the end of the coupling beam steel plate is the smallest, and the closer to the middle, the greater the shear force.

Effect of particle size and media volume fraction on the vibration attenuation of a thin-walled beam containing granular media

Granular media can be used inside structural elements to make their vibration damped. As an example, using granular dampers at the foundation and between the stores reduces the vibration of upper stores when earthquake waves are transferred to the building foundation. In this paper, effects of sand particles size and volume fraction are studied on the attenuation of free vibration of an aluminum elastic beam of box section encompassing sand particles. A high-speed camera was used to measure damping ratio of the beam vibration. It was observed that damping ratio of the beam filled partially with different sand samples was larger than those of the completely filled, mostly filled and empty beams. It was found that two parameters were responsible for larger damping ratios of partially filled beams: 1-frictional energy loss between sand particles themselves and the beam walls; 2-degree of particles possible movements leading to their slippage and collisions.

Criteria for Evaluating Local Stability of Steel Beam Walls in Case of Uneven Stress Distribution

In the article, numerical studies are performed to assess the stress-strain state of the wall of a steel beam with an I-beam symmetrical cross-section. The determination of internal forces and stresses is performed in the SCAD Office computing complex. A new method is proposed for estimating the average stress values in the wall, taking into account the uneven distribution of stress over the area of the wall section where local stability is evaluated. Based on the results of calculations, stress plots and mosaics are constructed, showing their spatial distribution of stress on the controlled sections of the beam wall compartments. Analysis of the research results showed that the most appropriate application of the proposed approach is in areas with uneven distribution of beam stresses, especially in the support sections of the wall.

Работа подкрановых балок с усталостными трещинами в зоне сжатого пояса

The method of determining the critical parameters of stability of the crane beam walls with fatigue cracks in the compressed belt zone is briefly described. The dependences of the bifurcation critical and limit stresses in the wall on the crack length, the crack position in the section, and on the wall flexibility are shown. The results of numerical studies of the effect of cracks on the increase in normal stresses in the compressed belt are presented. A method for assessing the local stability of the beam wall with a crack is proposed.

Устойчивость стенок подкрановых балок с усталостными трещинами в зоне сжатого пояса

The paper describes a method for assessing the bearing capacity of the crane beam walls with fatigue cracks. There has been developed and implemented an algorithm for evaluating the stress-strain and limit state of the beam with a crack in the wall under a compressed belt. There has been established the dependence of the stress-strain and limit states of the beam wall on the value of the initial relative beam bending and the crack length in the section under the action of the bending moment and transverse force. The author presents the results of numerical studies of the effect of cracks on the bearing capacity of the beam wall. The influence of the amplitude of the initial beam wall deflection on the critical stress parameters is revealed. The dependence of the values of critical stress parameters on the relative crack length is considered.

Nonlinear vibrations of a rotating thin-walled composite piezo-beam with circumferentially uniform stiffness (CUS)

A rotating system comprising a hub and a thin-walled laminate cantilever beam with embedded nonlinear piezoelectric layers is analysed in the paper. The reinforcing fibres set-up in composite material conforms to circumferentially uniform stiffness lamination scheme. This configuration exhibits the mutual bending couplings in two orthogonal planes. Nonlinear analytical model of a piezoelectric material embedded onto the beam walls is postulated by considering the higher-order constitutive relations with respect to electric field variable. Moreover, to properly model electromechanical structural behaviour, the full two-way coupling piezoelectric effect is considered. To this aim, the assumption of a spanwise electric field variation is postulated in the mathematical model of the structure. Based on previous authors’ research, the system of mutually coupled nonlinear equations of motion is formulated. In the numerical analysis the forced response of the system under zero and nonzero mean value harmonic torque excitation is considered. In particular, the influence of hub inertia, excitation amplitude and mean rotating speed on system dynamics is investigated. The results are presented in the form of appropriate frequency response plots and bifurcation diagrams.

Study on Damage of Shallow Foundation Building caused by Surface Curvature Deformation in Coal Mining Area

Coal mining can lead to various forms of surface deformation, the damage caused by curvature deformation is the most extensive, which has become the key to restricting the development and utilization of coal resources under villages. Therefore, it is very important to master the deformation and destruction mechanism of buildings under surface curvature deformation for the rational exploitation of coal resources under villages. In this paper, the deformation and damage of buildings caused by curvature deformation are studied with theoretical analysis and numerical simulation, aiming at the shallow foundation building in rural China, and the following objectives are achieved: 1) Based on the theory of elastic foundation beam, the longitudinal and transverse walls are considered as a whole and analyzed, and a mathematical model of the cooperative deformation in building walls under surface curvature deformation is established. 2) The failure mechanism of masonry buildings is analyzed, including the distribution of internal stress and the form of wall cracks. 3) The influence of various factors on the internal stress changes of buildings is discussed. 4) The results of numerical simulation of wall stress distribution are similar to theoretical analysis, and the influence of doors and windows on the additional stress distribution is analyzed emphatically. This study can provide important guidance for the optimization of coal mining design under villages and the protection of village buildings.

УЧЁТ СДВИГА ПРИ РАСЧЁТЕ БАЛОК СУДОВЫХ БОРТОВЫХ ПЕРЕКРЫТИЙ, ВОСПРИНИМАЮЩИХ ИНТЕНСИВНЫЕ ЛОКАЛЬНО РАСПРЕДЕЛЁННЫЕ НАГРУЗКИ

In the process of operation, shipboard beams are subjected to the impact of various types of loads, the greatest danger being intense local distributed loads which are the main cause of damage to ship hulls. Therefore, designing ship hulls with minimum weight characteristics, as well as choosing the optimum sizes of connections when reinforcing the beams, require to use methods for calculating hull structures under the action of local loads beyond the elastic limit. The paper presents design models that allow taking into account shear effects in the beam walls, as well as the effect of the support forces on elastic-plastic base on their deformation. These problems can be avoided, if the sector of the frame on which shearing force has reached the limit value can be replaced by an ideal cable lying on the elastic-plastic base with variable stiffness characteristics. The results of the calculation of the shipboard beams have been compared using the described approach and the method of "instantaneous variation of bending parameters". It is shown that for large deflections the discrepancy is insignificant, which is explained by the dominant influence of the support forces on the side skin and longitudinal forces on the behavior of locally loaded frames. The proposed technique allows taking into account the impact of shear effects on deformation of locally loaded frames, which can be used in design and modernization of ship hulls to select the optimum sizes of connections.

Adiabatic surface temperature as thermal/structural parameter in fire modeling: Thermal analysis for different wall conductivities

The new useful concept of “Adiabatic Surface Temperature” or more commonly known as AST, introduced by Wickström et al. in 2007, is investigated in this study. Adiabatic surface temperature can be used for bridging the gap between fire models and temperature models; for example, it offers the opportunity to transfer both thermal information of the gas and the net heat flux to the solid phase model, obtained by CFD analysis.In this study two numerical analyses are carried out in order to evaluate the effect of wall thermal conductivity and of convective heat transfer coefficient on the adiabatic surface temperature as thermal/structural parameter in fire modeling. First one CFD analysis simulating a fire scenario, “conjugate heat transfer”, with a square beam exposed to hot surface, is carried out to calculate AST, convective heat transfer coefficient and temperature field in the beam. In the second one, a conductive analysis is carried out on “standalone beam” imposing a third type boundary condition on its boundaries assuming the AST, evaluated in the conjugate analysis, as external temperature. Different convective heat transfer coefficients are imposed on the beam walls; the beam is of concrete or steel. Results are presented in terms of net heat flux on beam surfaces, convective heat transfer coefficients and temperature profiles on the beam walls, temperature fields for the two, CFD and conductive, analyses and the relative temperature and net heat flux percent errors. Results underline that convective heat transfer coefficient profiles and adiabatic surface temperatures on the bottom and lateral beam walls are independent of the wall thermal conductivity value, whereas the net heat flux values increase as wall thermal conductivity increases, fixed the emissivity.

An Improved Puncture Access Tip-Retraction Mechanism

An Improved Puncture Access Tip-Retraction Mechanism

Finite element analysis of beam-column T-joints of rectangular hollow steel sections strengthened using through-wall bolts

A nonlinear finite element model is developed to analyze beam-column T-joints of Rectangular Hollow Sections (RHS) strengthened using through-wall bolts. The model was verified using experimental results for different beam depth-to-wall thickness (h/t) ratios and different bolts configurations and captured the full response and web buckling at the vicinity of the column quite well. The model was then used in a parametric study to investigate the effects of beam depth-to-width (h/b) ratio, span-to-depth (L/h) ratio, column breadth-to-beam depth (B/h) ratio, and welding the bolts to the webs, on the ultimate-to-plastic moment (M/Mp) ratio. As (L/h) increased from 4.9 to 7.9, (M/Mp) increased from 0.57 to 0.77 for the control joints and from 0.71 to 1.0 for the strengthened joints. Similarly, the limits of (h/b) and (B/h) at which strengthening allows the RHS beam to reach its full plastic moment are established. Welding the bolts to the beam walls enhanced ductility considerably with little increase in strength.

Influence of wall emissivity and convective heat transfer coefficient on the adiabatic surface temperature as thermal/structural parameter in fire modeling

In fire engineering analysis, one of the open problem is the transfer of thermal parameters obtained by fire CFD model to FEM models for structural analysis. In this study the new useful concept of “Adiabatic Surface Temperature” or more commonly known as AST, introduced by Wickström, is investigated. The adiabatic surface temperature offers the opportunity to transfer both thermal information of the gas and the net heat flux to the solid phase model, obtained by CFD analysis.In this study two CFD analyses are carried out in order to evaluate the effect of emissivity and of convective heat transfer coefficient to determine the AST. First one CFD analysis simulating a fire scenario, “conjugate heat transfer”, with a square steel beam exposed to hot surface is carried out to calculate AST, heat convective coefficient and temperature field in the beam. Second one, a conductive analysis is carried out on “standalone beam” imposing a third type boundary condition on its boundaries assuming the AST, evaluated in the conjugate analysis, as external temperature. Different heat convective coefficients are imposed on the beam walls. The comparison between results obtained by means of the two proposed analyses shows the use of AST as transfer thermal parameter between CFD (Computational Fluid Dynamic) and FEM (Finite Element Method) models is appropriate when the convective heat transfer coefficient is properly evaluated.

Incorporation of wall finite relative rotations in a geometrically exact thin-walled beam element

In this paper, a large displacement and finite rotation thin-walled beam element previously developed by the authors, which accounts for cross-section deformation, is extended by including finite relative rotations of the beam walls in the in-plane kinematic description of the cross-sections. The inclusion of these relative rotations is motivated by the fact that it enables a simple and meaningful representation of the cross-section in-plane distortion and allows for a co-rotational description of the wall "local-plate" behavior, which leads to a computationally efficient numerical implementation. The present extension preserves all features of the original formulation, namely the geometrically exact description of the beam mid-surface and the allowance for arbitrary cross-section deformation modes complying with Kirchhoff's assumption. The efficiency of the resulting beam finite element is demonstrated by means of numerical examples, which include comparisons with solutions obtained by means of the previous beam finite element and standard shell finite elements.

Ballistic thermal conductance limited by phonon roughness scattering: A comparison of power-law and Gaussian roughness

In this work, we have investigated the influence of power-law roughness on the ballistic thermal conductance ${K}_{\mathrm{TH}}$ for a nanosized beam adiabatically connected between two heat reservoirs. The sideways wall beam roughness is assumed to be power-law type, which is described by the roughness amplitude $w$, the in-plane roughness correlation length $\ensuremath{\xi}$ and the roughness exponent $0\ensuremath{\leqslant}H\ensuremath{\leqslant}1$. Distinct differences occur in between power-law and Gaussian wall roughness. For power-law roughness with low roughness exponents $H$ $(<0.5)$, the influence of phonon scattering can be rather destructive leading to significant deviations from the universal conductance value for flat beam walls. On the other hand for large roughness exponents $(H>0.5)$ the conductance drop is significantly smaller than that of Gaussian roughness assuming similar roughness ratios $w∕\ensuremath{\xi}$.

A table top suited for CT and radiotherapy

Es sollte eine Tischplatte für die Anwendung in der Strahlentherapie konstruiert und gefertigt werden, die gleichermaßen für ein im Bestrahlungsraum integriertes CT geeignet ist. Kleinräumig war die maximale Verfälschung der Dosisverteilung durch den Tisch auf 4 % zu limitieren, die mittlere Reduktion über das gesamte Zielvolumen auf 2 %. Das CT sollte nur geringe Artefakte aufweisen, um eine Relokalisation des Zielvolumens im Bestrahlungsraum zu ermöglichen.Die Konstruktion der Platte aus kohlefaserverstärktem Kunststoff (CFK) erfolgte mit Hilfe von Finit-Element-Berechnungen. Eine Trapezform der Deckplatte wurde mit Längsträgern kombiniert. Auf der Schmalseite ist ein Durchtritt durch ein CT mit 60 cm Gantryöffnung möglich. Die drehbare Platte lässt auf der Breitseite die Applikation großformatiger ap-pa- Gegenfelder ohne Holmdurchstrahlung zu. Transmissionsmessungen mit Ionisationskammer wurden unter verschiedenen Einstrahlwinkeln durchgeführt, um den Einfluss der CFK-Tischholme und der Plattenfläche zu ermitteln. Zusätzlich wurde ein Flächendetektor (PID) zu vergleichenden Messungen herangezogen.Es zeigten sich geringere Durchbiegungen und Torsionen der Platte als beim Original. Die Transmission der Tischplattenfläche liegt bei 97,5 % bzw. 96,5 % (18 MV bzw. 6 MV). Sofern die Durchstrahlung der Längsträger nicht ganz vermieden werden kann, bewegt sich ihre Transmission in einem unkritischen Bereich. Die CT-Schnitte zeigen nur schwache Artefakte in Richtung der Wandungen der CFK-Längsträger. Die Lokalisation des Tumors bzw. des Zielvolumens wird dadurch nicht beeinträchtigt.

On the load distribution of thin-walled beams subjected to bending with respect to the cross-section distortion

The paper deals with the estimation of the load distribution under which distortion of the cross-sections of thin-walled beams subjected to bending cannot occur. It is assumed that beam walls are hinged along their longitudinal edges. Beams with closed and open rectangular cross-sections, with three or two cells, with two or one axis of symmetry are considered. It is shown that the problem can be treated by two equivalent beams, defined by the shear flow zero points of the beam with rigid cross-section. The beam load must be distributed in the plane of beam walls, proportionally to the cross-section moments of inertia of the equivalent beams. Some illustrative examples are given.

Optimization of composite I-sections using fiber angles as design variables

A problem formulation and solution methodology for design optimization of laminated composite I-sections is presented. Objective functions and constraints are given in the form of beam stiffnesses. Two different objective functions are considered, maximum beam bending stiffness and maximum beam axial stiffness. Fiber directions in the beam walls are treated as design variables. It is assumed that the beam is constructed using unidirectional tape, and manufacturing issues associated with the use of unidirectional tape are discussed and included as constraints in the problem formulation and solution. The paper demonstrates that the design optimization of composite thin-walled beams is a complex global optimization problem that cannot be solved by means of traditional convex programming. Therefore, the solutions described are found using a global search algorithm, Improving Hit-and-Run, which allows the design variables to be either continuous or discrete with a user-specified discretization interval. Numerical results for two material systems and nine different design families for manufacturing composite I-sections are presented.

AN ANALYTICAL MODEL FOR COMPOSITE BOX-BEAMS

A direct analytical beam formulation is developed for predicting the effective elastic stiffnesses and corresponding load deformation behavior of tailored box beams. Deformation of the beam is described by extension, bending, torsion, transverse shearing, and torsion related out-of-plane warping. The present analysis is developed without much dependence on thin-walled beam theory. Formulation of the analysis is in terms of a two-dimensional cross-section, instead of an infinitely thin contour enable stresses, strains, elastic properties to vary through the thickness of the beam walls in a manner consistent to the true laminated structure nature of the composite structure. This analytical model is very useful in studying non-classical phenomenon such as warping and in-plane elasticity. Governing differential equations for the extension, bending, torsion and shearing of the beam are derived using Newtonian approach. Validation studies are carried out for composite designs with no coupling, designs With varying degrees of extension-torsion and bending shear coupling, as well as • tdesigns with varying degrees of torsion-bending and extension shear coupling. The analysis is evaluated by correlation with existing experimental results.