Thickness Of Cover Plate Research Articles

Behaviour and design of demountable steel column-column connections

This paper presents a finite element (FE) model for predicting the behaviour of steel column-column connections under axial compression and tension. A robustness approach is utilised for the design of steel columncolumn connections. The FE models take into account for the effects of initial geometric imperfections, material nonlinearities and geometric nonlinearities. The accuracy of the FE models is examined by comparing the predicted results with independent experimental results. It is demonstrated that the FE models accurately predict the ultimate axial strengths and load-deflection curves for steel column-column connections. A parametric study is carried out to investigate the effects of slenderness ratio, contact surface imperfection, thickness of cover-plates, end-plate thickness and bolt position. The buckling strengths of steel column-column connections with contact surface imperfections are compared with design strengths obtained from Australian Standards AS4100 (1998) and Eurocode 3 (2005). It is found that the column connections with maximum allowable imperfections satisfy the design requirements. Furthermore, the steel column-column connections analysed in this paper can be dismantled and reused safely under typical service loads which are usually less than 40% of ultimate axial strengths. The results indicate that steel column-column connections can be demounted at 50% of the ultimate axial load which is greater than typical service load.

Dwell and penetration of tungsten heavy alloy long-rod penetrators impacting unconfined finite-thickness silicon carbide ceramic targets

Impact experiments with a tungsten heavy alloy long rod projectile against silicon carbide tiles were performed to study the transition from dwell to penetration and to compare against earlier investigations which focused either on small scale semi-infinite set-ups or on finite thickness set-ups with confinement. A depth-of-penetration configuration consisting of a ceramic tile and an extended steel backing was used to assess the impact response of the unconfined finite-thickness ceramic. The ceramic tile was either bare or had a cover plate attached to the front. The cover plate thickness has been varied and gives best results for a thickness of about half the projectile diameter used in the experiments. For the bare ceramic, a long dwell phase can be maintained up to impact velocities of around 900 m/s. For the buffered ceramic, partial dwell can be achieved up to around 1700 m/s. The results corroborate those of earlier investigations mentioned above. More importantly, the present results show that it is possible to substantially erode a heavy alloy long-rod penetrator at the surface of a finite thickness ceramic element without lateral confinement in direct impact experiments even at high impact velocities.

The Repair Method of Damaged H-shaped Steel Members and Experimental Study on Recovery after Repair

Recently, there have been many discussions about repairability for damaged building structures after severe disasters. In japan, a technical manual for repairing damaged buildings has been established; however, its repair abilities have not been reported sufficiently. In this study, the Box-Shaped Repair Method which has been suggested on Japanese technical guideline is adopted for the damaged steel members, and its applicability and feasibility are investigated experimentally. Herein, the damaged portion on steel member such as plastic hinge or local buckling occurrence is covered with steel plate by welding. So the loading test is performed as parameters with section size of steel members, thickness of cover plate and welding size during repair process, and loading path. The procedure of this study is as follows; the first, the damaged test specimens of H-shaped steel member with local buckling are reproduced by initial loading test. Next, the damaged specimens with plastic residual deformation are returned to the original position. Finally, the loading test is done after repair. From test results, it is confirmed that the fundamental structural performance such as the rigidity, maximum strength, and absorbed energy after repair are improved by comparison of original state. And also, this performance can be controlled by adjusting the thickness of cover plate and welding condition. Furthermore, from the observation of test results, the analytical model of repaired steel member is suggested. From the comparison of test results, it can be said that the proposed model shows good agreements both test results and theoretical figure.

Study of TBM cutterhead fatigue crack propagation life based on multi-degree of freedom coupling system dynamics

Cutterhead is the core component of TBM tunneling equipment, which endures strong, multi-point distributed impact loads when the TBM tunnels, owing to the extreme surrounding rock environment of high hardness, high temperature and high quartz content. For this reason, the cutterhead works in an extremely severe vibration environment, which leads to engineering fault by a large area crack damage before the service life. Hence, the study on life prediction of TBM cutterhead under the impact loads is a core part of cutterhead design. This paper combines with the technology of system dynamics, linear elastic fracture mechanics and cumulative theory of fatigue damage, for the first time, proposes a method of fatigue crack propagation life prediction for the large and complex structures. In this paper, the TBM cutterhead of an actual project is taken as an example, to predict the fatigue crack propagation life of cutterhead piece and analyze the influences of plate thicknesses on fatigue life, then a new improved scheme of cutterhead structure is presented. The results show that the fatigue crack propagation life of actual cutterhead is 26.6km, which is able to meet the requirement of 20km service life. Moreover, the upper cover plate thickness has the greatest influence on cutterhead fatigue crack propagation life, with the thickness increasing 10%, the life increases nearly by 1.24 times. Then, the other influencing factors are as follows: thickness of the main support plate, thickness of the annular support plate and thickness of the support plate, whereas the influence of the lower cover plate thickness on fatigue life is minimal. Furthermore, the plate thickness limit sizes meeting the life requirement are obtained, and a new structure modified scheme of cutterhead is proposed. Compared with the original scheme, the new cutterhead scheme meets the requirements of structural strength and service life with 8.08% weight decrease, which achieves life determination design and lightweight design. The proposed method of fatigue crack propagation life prediction is feasible in the design and application stage of TBM cutterhead, besides, it is flexible enough and can also be applied in damage strength assessment, dynamic parameters optimization and establishment of nondestructive inspection cycle for the other large and complex structure, and takes on stronger project value and generality.

Plasticization of Trunk Lid and Molding Parameter Optimization

A trunk lid plate was taken as an example and Fiberglass-reinforced PET material was used to replace steel for weight-saving in this paper. According to the thin plate stiffness theory, thickness of suitcase cover plate is 3 mm approximately, using finite element simulation analysis to verify its stiffness and mode meet requirements exactly. Injection molding was chosen as plates forming method. Plastic parts warpage had closely relationship with various process parameters, orthogonal experiment was used to find the optimal parameter in the given range.

Modeling and validation of mechanical stress in indium tin oxide layer integrated in highly flexible stacked thin films

Organic electronic devices with multi-stacked thin films based on polymeric substrates are proposed for use in mainstream flexible organic light-emitting diode displays. To achieve the above-mentioned requirements, indium tin oxide (ITO) thin film, a brittle, inorganic material, is necessary to be utilized as a transparent electrode in flexible electronics. The failure rate of ITO films is of concern when introducing harsh flexural load in terms of reliability. This study utilizes a simulation-based factorial-design approach to determine a suitable combination of mechanical characteristics of ITO film stacked with other films to reduce the neutral plane (NP) impact of stacked films. The results indicate that both Young's modulus and cover plate thickness are major factors that alter the stress magnitude of ITO films. Moreover, the simulated results for stacked structures reveal that the distance between the ITO film and NP is significantly reduced when polyimide materials, rather than steel metal, are used for the cover plate. In the meanwhile, ITO film stress drops in virtue of lower mechanical stiffness and lesser thickness direction between the NP and ITO films in a multi-stacked film structure.

Static Response of Steel-Concrete-Steel Sandwich Beam with Bi-Directionally Inclined Connectors

Steel-concrete-steel (SCS) sandwich construction combines the advantages of both steel and concrete and finds application in numerous areas such as bridges, protection against impact and blast loads, flooring system etc. Shear connector is a critical component of SCS system. In the present study, two new configurations of bi-directionally inclined shear connector are proposed. Response behaviour of SCS beams with bi-directionally inclined connector is obtained through numerical investigations. Finite element models of SCS beams are generated by using a simplified approach that employs solid, plate and beam elements to represent concrete, cover plates and shear connector respectively. Behaviour of concrete is represented using concrete damaged plasticity model, while steel behaviour is modelled by using bilinear stress-strain curve. Beam is simply supported and is subjected to a central concentrated load. Nonlinear static analysis is carried out to obtain load-deflection response. Numerical model is validated by solving a SCS beam with through-through connectors, which was experimentally investigated in literature. Responses from bi-directionally inclined connectors are compared with that of through-through connectors. Bi-directionally inclined connector is found to be more ductile compared to that of through-through connector, while the load carrying capacity remains same. Parametric study is carried out by varying the cover plate thickness, angle of inclination and diameter of the connector to study their influence on the behaviour of the steel-concrete composite beam.

Influence of the cover plate thickness on the Lamb wave propagation in honeycomb sandwich panels

Within this paper, the guided Lamb wave propagation in thin honeycomb sandwich panels is studied. The Lamb waves are excited by thin piezoelectric (PZT) patch actuators glued to the surface of the plate, and the signals are received by similar PZT sensor patches. Such actuator and sensor systems can be used for a cost-effective online health monitoring of structures. In homogeneous plates, Lamb waves propagate with symmetrical and anti-symmetrical modes. However, the propagation in heterogeneous media is not as clear and depends on the exciting frequency, the material properties, and the geometry of the structure. In this paper, the influence of the geometrical properties of honeycomb plates on the Lamb wave propagation is studied. For this purpose detailed 3-D finite element calculations are performed, which result in very time consuming computations. Consequently, also simplified models are developed to reduce the computing time without losing the quality of the results. To this end, the honeycomb core material is replaced by a homogeneous layer with orthotropic mechanical properties. The homogenized properties are calculated numerically using a homogenization technique based on the representative volume element method. The comparison of the results received with the two different approaches has shown that the simplified models are in a good agreement with the extended models for a certain range of exciting frequencies and geometrical properties only. The wave propagation on the top and bottom surfaces is also compared in order to show how deep the waves can travel inside the structure.

Numerical simulation of Lamb wave propagation in metallic foam sandwich structures: a parametric study

The propagation of guided Lamb waves in metallic foam sandwich panels is described in this paper and analyzed numerically with a three-dimensional finite element simulation. The influence of geometrical properties of the foam sandwich plates (such as the irregularity of the foam structure, the relative density or the cover plate thickness) on the wave propagation is investigated in a parametric study. Open-cell and closed-cell structures are found to exhibit similar wave propagation behavior. In addition to the finite element model with fully resolved microstructure, a simplified, computationally cheaper model is also considered – there the porous core of the sandwich panel is approximated by a homogenized effective medium. The limitations of this homogenization approach are briefly pointed out.

Numerical Study on Energy Dissipation and Hysteretic Behavior of Plate-Reinforced Connections

14 models of plate-reinforced connections are analyzed by finite element software ANSYS. Failure mode, hysteretic behavior, ductility and energy dissipation capacity are comparatively studied. Results show that plastic hinge formed at the end of the reinforced plate, hysteretic cruves are full and the connections have good ductility. With the increase in length and thickness of the reinforced plate, bearing capacity increases while hysteretic behavior and ductility factor decrease. If the reinforced plate is longer than the length that design requires, brittle failure occurs in the panel zone. The recommended length of the reinforced plate is defined as 0.5-0.8 times of beam depth, the thickness of flange-plate is 1.2-1.4 times of flange thickness and the thickness of cover-plate is 0.7-1.2 times of flange thickness.

Experimental Study on Hysteretic Behavior for Plate-Reinforced Connections

8 plate-reinforced connections are manufactured at 1/2 scale and then tested under low-cyclic loadings to study their hysteretic behavior, and numerical simultation with ANSYS are applied based on the experimental results. Failure patterns, energy dissipation, hysteretic behavior and skeleton curves are comparatively studied by changing the dimensions of the reinforced plates. Results show:(1)the plastic hinge be formed 1/3-1/4 beam depth from the end of reinforced plate and is obvious, there are serious local buckling in the flange and web, and there is no fracture in the beam-to-column welding;(2)The geometric parameters of reinforced plate have important effect to the bearing capacity and ductility of connections. With the increase of length and thickness of reinforced plate, the bearing capacity increases and hysteretic behavior and ductility factor decreases;(3)When the length of reinforced plate is bigger than the design requirements, there is brittle failure in the panel zone, which lead to decrease of capacity of energy dissipation and equivalent viscous damp coefficient;(4)Recommended parameter scope: the recommended length of reinforced plate(flange-plate and cover-plate) is defined as 0.5-0.8 times beam depth, the recommended thickness of flange-plate is 1.2-1.4 times flange and the recommended thickness of cover-plate is 0.7-1.2 times flange.

Fracture of aluminium foam core sacrificial cladding subjected to air-blast loading

The effect of core density and cover plate thickness on the blast response of sacrificial cladding panels has been investigated through blast loading experiments and finite element modelling on structures with steel cover plates and aluminium foam cores. A range of foam core densities were examined, with 10%, 15% and 20% nominal relative densities. The cover plate thickness greatly influenced the response of the sacrificial cladding. Cover plates that were 2 mm thick exhibited significant permanent deformations and variable percentage crush across the section, whereas the 4 mm thick cover plates were more rigid causing the core to compress uniformly. Considerable fracture of the foam was observed after blast testing, particularly for the lower density foams. The effect of bonding the cover plate to the core was also examined. Numerical simulations of the experiments were performed using ABAQUS/Explicit to provide insight into the response mechanism. It was shown through the finite element simulations that tensile fracture of the foam occurred during the unloading phase of response and that adhesion of the cover plate to the foam caused higher levels of cracking. This was consistent with the experimental observations.

柱貫通型・柱鉄筋コンクリート-梁鉄骨造柱・梁接合部の強度と変形能に関する実験的研究

This study is intended for obtaining knowledge about the influence exerted by the existence of each component upon the strength and deformation capacity of RCS (reinforced concrete plus steel) joint. The test results demonstrated the following: (1) the shear force borne by the cover plate and FBP is small, (2) the orthogonal component limits the concrete deflection at joint, (3) greater thickness of cover plate improves the hysteretic characteristics, and (4) good hysteretic characteristics can be achieved by limiting the average shear input to the joint.