Thickness Of Cover Plate Research Articles

Porous acoustic metamaterial for simultaneous control of high and low frequency machinery noise: Case study of a water pump.

An acoustic metamaterial (AMM) consisting of a porous material (melamine foam) layer above a symmetrical labyrinthine metamaterial, incorporating a micro-hole and micro-slit cover plate, is proposed to simultaneously mitigate low and high frequency noise from industrial machineries. Theoretical model of sound absorption by this AMM is developed and validated numerically and experimentally. Sensitivity analysis indicates that increasing the length of the labyrinthine pathway and cover plate thickness and decreasing the slit width, slit length, and hole diameter shifts the peak sound absorption to lower frequencies. This material is successfully applied as a sound absorptive enclosure of a 0.5 hp water pump to reduce its sound pressure levels across widely separated frequencies of 1414-2245 Hz (high frequency) and 176-222 Hz (low frequency). This study offers guidelines to noise control engineers for controlling low and high frequency noise in industrial machineries.

Influence of the cover plate thickness on the ballistic penetration of re-entrant auxetic structures

This study investigated how mild steel cover plates of various thicknesses affected the collapse of re-entrant auxetic structures under penetration at 500 m/s by ø16 mm spherical projectiles. A combination of experimental and numerical methods was used to capture this effect with auxetic structures made from 3D printed titanium alloy (Ti6Al4V) and ABS plastic (acrylonitrile butadiene styrene), and wire cut 304 stainless steel (SS304). Experimentally, structures were tested with a 2.90 mm cover plate and without the cover plate. Numerically, the effect of the cover plate thickness on the auxetic response of the structure was tested with 0.95 mm, 1.50 mm, and 2.90 mm cover plates (as well as no cover plate). The auxetic densification was found to be greatest under the thickest cover. Material characterisation tests were conducted to develop strength and failure models for the mild steel cover and back plates in this study, which produced simulated correlation to the ballistic experiments. Although the simulated auxetic effect generally increased with cover plate thickness, similar to the experiments, the structure material significantly affected the range of this dependence. For the ductile SS304 structures, a thin (0.95 mm) cover plate showed a small improvement in the auxetic response, with a marked improvement with a 1.50 mm cover plate. Whereas the Ti6Al4V structures showed a steady improvement in auxetic densification as the cover plate thickness was increased. Overall densification of the ABS structures was significantly improved by adding cover plates, however collapse was delayed compared to the other materials. These findings therefore indicate that the thickness of cover plates in auxetic sandwiches can be specifically engineered to maximise auxetic effect while considering the ranges of this dependence with different auxetic materials.

Influence of sewage culvert cover plate thickness on dynamic response and damage of the cover plate under gas explosion

In order to address the risk of combustible gas explosions in sewage culverts, a numerical model was established using ANSYS/LS-DYNA software. The model consisted of a culvert and a cover plate, and was used to study the effect of cover plate thickness (ranging from 0.08 m to 0.12 m) on the dynamic response and damage of the structure under explosive loads. The results indicated that, during the loading negative pressure stage, the equivalent stress peak value of the central monitoring unit of the cover plate first increased and then decreased with increasing cover plate thickness. Additionally, the maximum principal stress peak value first decreased and then increased, while the maximum shear stress peak value first increased and then decreased. During the loading positive pressure stage, the maximum principal strain peak value of the monitoring unit decreased overall with increasing cover plate thickness. However, the equivalent plastic strain peak value initially increased and then decreased gradually. The equivalent strain indicated that plastic damage occurred in the cover plate. Beyond a thickness of 0.11 m, increasing the cover thickness did not appear to enhance its resistance to plastic damage. The damage analysis revealed that as cover plate thickness increased, the peak displacement and velocity of the monitoring unit continued to decrease, while the overall stability and explosive resistance of the cover plate increased. Additionally, the number of damaged fragments decreased. However, once the cover plate thickness reached 0.11 m, the bonding performance of the reinforced concrete structure had been fully developed, increasing the thickness of the cover plate no longer had a significant impact on the explosive resistance of the cover plate.

Nonlinear parametric assessment of modular prefabricated steel-reinforced concrete composite column subjected to earthquake loading

This study is intended to propose a novel bolted off-site connection for prefabricated steel-reinforced concrete composite (PSRC) column to overcome significant problems involved in the traditional precast concrete connections, such as its complicity under compacted sleeve grouting and insufficient post-cast concrete vibration. Within the context of the study, the seismic characteristics such as failure model, stiffness, and energy dissipation of five PSRC columns subjected to different axial compression and shear-to-span ratios were investigated by conducting low reversed cyclic tests. Thereafter, the accuracy of multiple finite element models (FEM) of the test specimens was verified against the experimental results. In general, the research outcomes showed that the PSRC column has a simple connection structure, efficient assembly, good bearing capacity, and hysteresis characteristics. Under the influence of different parameters, the failure position was located at the middle connection, which was the key to the overall seismic performance. Moreover, it was found that the axial compression and shear-span ratios significantly affect the seismic performance of the joints. The stiffening plate thickness, the cover plate thickness, the square steel tube width-thickness ratio and the middle connection position height greatly impacted the bearing capacity but had an ignorable influence on the ductility, energy consumption, and performance degradation.

Experimental and numerical investigations of bolted assembled joints to concrete encased CFST columns with different connection details

Concrete encased CFST (CECFST) composite components have prominent advantages over traditional CFST components such as better durability, high stiffness and strength, etc. However, the encased concrete outside caused certain difficulty in connecting to the steel beam. In this paper, two types of bolted assembled joints between CECFST column and steel beam were proposed and tested under cyclic loads, in which the end plate and cover plate joints were included. Typical failure modes of the joints were analyzed and characterized. In comparison, the CECFST column in end plate joints exhibited more severe failure and higher strength than that in cover plate joints. Seismic performance including hysteretic curves and energy dissipation were also discussed. In addition, numerical modelling of the joint was established considering the complicated material models and interactions in the joint core, of which the accuracy was validated against the test results. Further, parametric analyses were performed on the cover plate joints with CECFST columns through the numerical approach. It demonstrated that the axial ratio, thickness and strength of cover plate, diameter of bolt, strength and thickness of steel tube significantly affected the stiffness and strength of the joint. The experimental and numerical results revealed that the proposed two types of joints with CECFST column performed relatively favorable seismic behavior and could be employed in engineering practice.

Steel rocking column bases with replaceable cover plates: Cyclic loading behaviour and practical design

This study proposed a steel rocking column base that dissipates seismic energy through a pair of replaceable steel cover plates. Three specimens of the proposed steel column base were designed and tested under static cyclic loading. Hysteretic response, failure modes, and energy dissipation of the column base were obtained and discussed. Then three-dimensional finite element model of the column base was built and validated against the test results. Later on, a component method was employed to predict the rotational stiffness and capacity of the column base. The Yield Line Theory was employed to predict the ultimate capacity of the cover plates and the demand of axial resistance of anchoring rods. It shows that the proposed column base is capable of dissipating seismic energy through the plastic bending of the cover plates. The moment resisting capacity increased with the increasing yield strength and thickness of cover plates and axial compression ratio, wherein the axial compression ratio has the most significant effect. The proposed design equations can predict the rotational stiffness of the column base and ultimate capacity of the column base with acceptable accuracy. Moreover, stiffening approaches for the column end were also presented to facilitate the practical design of the proposed column base.

Numerical study on the seismic performance of precast UHPC bridge columns considering the buckling behavior of replaceable energy dissipaters

This paper aims to explore the seismic performance of a novel earthquake-resilient bridge column with replaceable elements, including external ultra-high-performance concrete (UHPC) cover plates and internal steel dissipaters, based on a numerical model including local and overall levels. The overall model was established to assess the seismic behavior of the bridge columns considering the buckling behavior of steel dissipaters adopting the modified material constitutive relationship, of which the parameters were determined according to the results of the local model. The numerical model was verified with reported experimental results. A parametric analysis was conducted to investigate the effects of three parameters. The results show that the numerical model can effectively evaluate the seismic performance of the bridge columns. The buckling behavior of steel dissipaters dominates lateral deformation capacity of the bridge columns. The steel dissipater's initial defect direction and gap gradient can accelerate the failure of cover plates. Reasonable upper and lower limits are required for the length-to-diameter ratio of the fuse part as well as the gap between the fuse part and surrounding concrete, while only a suitable lower limit is needed for the thickness of cover plate to ensure the superior seismic performance of the bridge columns.

Seismic behavior of assembled beam-column joints with C-shaped cantilever section

A kind of assembled steel beam-column joint with C-shaped cantilever section was proposed. The influences of the lengths of cantilever sections and cover plates on seismic performance of the joints were discussed through low-cycle reciprocating loading tests and numerical simulations. Then the sensitivity analysis of key parameters such as thickness and width of flange plate,bolt number and cover plate's length were carried out. The results show that the joint consumed energy through warping deformations of end plate and the friction slippages between flange of beam, C-shaped cantilever section and cover plate. By reasonably increasing the lengths of C-shaped cantilevers section and cover plates, it can ensure that the joints have high bearing capacities, while significantly improving energy dissipation capacities of the joints. Parameter analysis showed that increasing thickness of the flange plate can effectively improve the stress concentration at root of the cantilever section. Reducing width of flange plate has a great impact on bearing capacity and initial stiffness of the joint with the maximum drop amplitude of 13.1% and 18.9%, respectively.

Influence of cover thickness on the ballistic performance of silicon carbide subjected to large-scale tungsten projectiles

Al alloy was the optimal metal cover material for confined silicon carbide (SiC) against blunt tungsten-heavy-alloy projectiles based on a previous research. In this study, the influence of the aluminium (Al) alloy plate thickness on the ballistic performance of SiC was investigated to determine the optimal plate thickness. In addition, the ballistic responses of covered ceramic composite structures under various impact velocities were examined. The failure features of the cover plates and ceramic were elaborated based on tests and simulation analyses. The penetration weight calculated using the measured residual penetration was applied to characterise the ballistic performance of ceramic armour modules. The results showed that thin and thick cover plates could increase the loading rate of the ceramic pressure, thus attenuating their buffering effects on the ceramic. Therefore, the determination of the optimal cover plate thickness must simultaneously meet the requirements of stiffness and the reduced ceramic pressure loading rate. The optimal thickness for the Al alloy cover plate was 4 mm for lateral and back confined ceramic against blunt projectiles in this paper, which was obtained via a numerical simulation. Finally, the buffering effect of the cover plate on enhancing the structural ballistic performance varied with the impact velocities of the projectiles. This study provides insights for covered ceramic armour applications.

Simulation study on influence of component thickness on dwell-penetration transition time of long rod projectile impacting ceramic armour module

The influence of component thickness of ceramic armour performance against long rod projectile is a critical information for the process of armour design optimization. In this study, the correlation between dwell time and cover plate thickness and mechanism shift with different ceramic to backing plate thickness ratio were studied using hydrocode simulation software LS-Dyna. The projectile is a long rod projectile with a length to diameter ratio of 14 at a nominal velocity of 1.25 km/s. In this study the cover plate performance is studied based on a surrogate module configuration, where the backing thickness is 10 mm instead of the usual semi-infinite thickness backing which has minimal bending deformation. The parameters used in the simulation were calibrated against experimental data in previous studies. From the study, the cover plate needs a minimal thickness to establish dwell. For thicker cover plate, the dwell time starts to decrease due to the confinement provided by thickness of the cover, which limited the lateral flow of the cover plate. This restriction of lateral flow, resulted in pressure build-up at the ceramic surface, thus, reducing the dwell time.

Effect of Cover Plate on the Ballistic Performance of Ceramic Armor.

The interface defeat and dwell can effectively improve the ballistic performance of ceramic armors under high velocity impact of long rod projectiles. Confinement conditions along both axial and radial directions of ceramic armors can affect these behaviors. With the aim of giving an insight into the effect of cover plate thickness and connection mode of cover plates with confining tubes on these behaviors, numerical simulations were performed in which the confined silicon carbide (SiC) targets with cover plates were impacted by tungsten rods. The pressure on the surfaces of SiC targets with fixed cover plates are compared to that with free cover plates, showing that the plates fixed with the confining tubes can produce higher pressure by way of wedging. With the increase in cover plate thickness, the dwell duration of the tungsten rods on the ceramic interface gradually grows. In addition, the upper and lower limits of transition impact velocities for the SiC targets with cover plates in different connection modes (i.e., free or fixed) were obtained and analyzed. The results show that the increase rate of the transition velocity region for the cover plate with the fixed-mode is relatively stable and lower than with the free-mode. On this basis, the fixed cover plate contributes higher ballistic performances to the SiC target than the free cover plate. It is also noteworthy that the size of transition velocity region does not enlarge linearly with the increase in cover plate thickness due to the slow growth of the upper limit. Accordingly, thickness thresholds exist, which are 5 mm and 6 mm for the fixed and free cover plates, respectively. Considering the ballistic performance and economy, the cover plate with the thickness ranging from 3 mm to 5 mm, i.e., 1.5~2.5 times of the tungsten rod diameter, is ideal for the structural dimensions in this paper.

Mechanical properties of modular prefabricated steel-concrete composite internal joints under cyclic loading

To investigate the influence of the key parameters on the mechanical properties of modular prefabricated steel-concrete composite internal joint (MPCIJ), finite element model (FEM) of MPCIJ under cyclic load was established by using the finite element analysis (FEA) software ABAQUS, based on test results. FEA results were then compared with the test hysteresis curves, skeleton curves, and failure mode. Based on the verification of reliability of the numerical model, the influence of different parameters on the structural performance was analyzed. According to test and FEA results, the MPCIJ shear mechanism and bearing capacity calculation formula were proposed. Results showed that MPCIJ bearing capacity and deformation performance increased with increasing axial compression ratio (n < 0.45), however, the increase was within 5%. With the increase of concrete strength, the joint bearing capacity and fire resistance and corrosion resistance of joint modules were effectively improved. The recommended width/thickness ratio of the square steel tube should not be less than 17. Reducing the distance between the bolt edges could improve the plastic deformation of the joint module with the recommended value of 25–35 mm. The bolt hole diameter increase should be between 1.5 and 2 mm. MPCIJ bearing capacity increased with increasing thickness of joint cover plate and the peak load increased by about 17%; however, the shear deformation inside the joint module also increased. The shear mechanism of MPCIJ is the ‘steel plate shear wall’ and ‘T-shaped steel frame’. The correctness and reliability of the MPCIJ shear capacity formula were verified.

Behavior of Steel–Concrete–Sandwiched Beam with Steel Fiber Reinforced Concrete Core and X-Form Shear Connectors

Steel–concrete–sandwich (S–C–S) construction has its applications in protection against fatigue, impact and blast loads. In blast-resistant construction, concrete is the most predominantly used building material. Due to the impact of blast loads, the structural and material integrity of concrete gets deteriorated due to spalling, cracking, etc. Recent studies have showed that steel–concrete–sandwich structures exhibited better ductility, structural integrity and blast-resistant capacity. The paper presents a numerical study on steel–concrete–sandwiched beam with through–through shear connectors (S–C–S-TT) after validation from previous experimental tests. Also, the shear connector of the S–C–S-TT beam was modified to X-form shear connectors (S–C–S-X) and its behavior due to the configuration change was studied. The performance of the S–C–S-X beam was found to be superior in terms load carrying capacity and deflection capacity than the S–C–S-TT beam. In order to understand the role of fiber reinforced concrete in S–C–S construction, a new S–C–S-X beam with steel fiber reinforced concrete core (S–C–S-X-SFRC) was modeled and its performance was comparatively studied with S–C–S-TT beam and S–C–S-X beam. The results showed that the S–C–S-X-SFRC beam exhibited enhanced deflection capacity as well as high load carrying capacity than S–C–S-TT beam and S–C–S-X beam. A parametric study was carried out by varying the diameter of connectors, thickness of cover plates and spacing of connectors of S–C–S-X-SFRC beam. From the study, the deflection capacity, which is considered as an important factor for absorbing energy and for designing structures against explosion induced forces, of S–C–S-X-SFRC was found to be high, and thus, it can be used as an alternative to conventional concrete in areas subjected to extreme loading.

Experimental study of earthquake-resilient prefabricated opening-web steel channel beam-column joint with double FCPs

In order to facilitate floor assembly and pipeline paving, this paper puts forward a new kind of prefabricated opening-web steel channel beam-column joint with double flange cover plates (POWSCBCJ) which is based on the design concept of plastic damage concentration and replaceable damage components. Six quasi-static reciprocating loading tests were carried out on four joints, and the hysteretic curves, skeleton curves, slip curves and strain curves of each specimen were obtained. The effects of thickness of flange cover plate (FCP), the quantity of connecting bolts and the bolts spacing of FCP and other parameters on the seismic performance and post-earthquake repairable performance of the joint are mainly investigated, and the post-earthquake repairable function, and fatigue performance of the joint under low-cycle reciprocating load are evaluated. Experimental study shows that this kind of joint has good bearing capacity, seismic performance and low-cycle fatigue performance. The joint can transfer the plastic hinge to the replaced FCP by strengthening the flange of the cantilever beam and weakening the FCP, so as to protect the major components such as beams and columns, and the joint function can be quickly repaired by replacing the energy dissipation components after earthquake; the repaired joint also has good bearing capacity and seismic capacity. Each design parameter has great influence on the bearing capacity and energy dissipation capacity of the joint.

The Collapse Analysis of the Lateral-Torsional Buckling of I-Shaped Stepped Steel Beams

The use of a non-prismatic member such as a stepped beam as a design method has the ability to function as a tool for steel beams optimization. A cover plate is partially welded on the upper and lower flange of the member at the maximum bending moment location to increase its flexural strength and, under critical load, flexural members bend about its strong axis, displace to the lateral direction, and twist coincidentally through a phenomenon known as the Lateral-Torsional Buckling (LTB). There is, however, no equations in the AISC 360-16 specification to calculate the critical moment of a stepped beam (Mst). Therefore, this research focuses on developing Mst for a simply supported stepped beam which deforms on its shear center under static-transverse loading through the use of a collapse analysis and the behavior of the beam. The results showed the welded cover plates consequently increased the LTB resistance of the prismatic I-shaped steel beam from 9.8% to 202% while the critical moment increased more significantly with an increment in the ratio of the cover plate length to the unbraced length (α). The cover plate thickness was observed to have dominantly affected only a large α ratio while the post-buckling characteristic of large α showed a sudden collapse phenomenon. Furthermore, the LTB modification factor was generated in this study due to the initial geometrical imperfection from the first mode of Eigen shape with maximum amplitude Lb/2000 (Cb1) and stepped beam shape (Cst) which were required to estimate the critical moment of a stepped beam based on the AISC equation for a prismatic beam.

Damage assessment of reinforced concrete columns retrofitted by steel jacket under blast loading

SummaryIn this study, the damage to a reinforced concrete column retrofitted by steel jacket subjected to blast loading was investigated. Actually, this research is an extensive study of the previous works of the authors. Therefore, some of finite element modeling and validation procedure were adopted. Extensively, the effect of the steel jacket used for retrofitting the reinforced concrete column was evaluated. The effects of scaled distance, axial compressive force, and steel cover plate thickness on the structural performance of the column were investigated and discussed. Moreover, the residual strengths of the column with respect to the different scaled distances were also evaluated. Some useful discussions and recommendations, which may interest structural engineers and researchers, were presented as an important outcome of this research.

Interface defeat studies of long-rod projectile impacting on ceramic targets

Abstract The interface defeat phenomenon always occurs when a long-rod projectile impacting on the ceramic target with certain velocity, i.e., the projectile is forced to flow radially on the surface of ceramic plates for a period of time without significant penetration. Interface defeat has a direct effect upon the ballistic performance of the armor piercing projectile, which is studied numerically and theoretically at present. Firstly, by modeling the projectiles and ceramic targets with the SPH (Smoothed Particle Hydrodynamics) particles and Lagrange finite elements, the systematic numerical simulations on interface defeat are performed with the commercial finite element program AUTODYN. Three different responses, i.e., complete interface defeat, dwell and direct penetration, are reproduced in different types of ceramic targets (bare, buffered, radially confined and oblique). Furthermore, by adopting the validated numerical algorithms, constitutive models and the corresponding material parameters, the influences of projectile (material, diameter, nose shape), constitutive models of ceramic (JH-1 and JH-2 models), buffer and cover plate (thickness, constraints, material), as well as the prestress acted on the target (radial and hydrostatic) on the interface defeat (transition velocity and dwell time) are systematically investigated. Finally, based on the energy conservation approach and taking the strain rate effect of ceramic material into account, a modified model for predicting the upper limit of transition velocity is proposed and validated. The present work and derived conclusions can provide helpful reference for the design and optimization of both the long-rod projectile and ceramic armor.

Enhanced ignition behavior of reactive material projectiles impacting fuel-filled tank

Abstract Reactive material projectiles can be an extremely efficient lethality enhancement technology that incorporates the defeat mechanisms of chemical energy and kinetic energy. This paper presents such a research on the enhanced ignition behavior of reactive material projectiles impacting a fuel-filled tank. Firstly, the ignition process description of the fuel-filled tank impacted by inert metal and reactive material projectiles is presented. Secondly, ballistic impact experiments are performed to investigate the ignition effects of the fuel-filled tank impacted by reactive material versus tungsten alloy projectiles with mass matched. The fuel tank used for the experiments is a cylindrical steel casing structure filled with aviation kerosene and sealed with aluminum cover plates on both ends using screw bolts. The experimental results indicate that, compared with impacts from tungsten alloy projectiles, there is dramatically enhanced structural damage to the fuel-filled tank and an enhanced ignition effect caused by reactive material projectile impacts. Finally, an analytical model is developed, by which the effects of the aluminum cover plate thickness on critical structural failure energy of the fuel-filled tank and the total energy of the reactive material projectile deposited into the fuel-filled tank are discussed. The analysis shows a good agreement with the experiments.

Seismic performance of bolted connection of H-beam to HSS-column with web end-plate

This paper presents an experimental study on a bolted joint for connecting H-section steel beams to square hollow structural steel (HSS) columns and connecting upper and lower HSS columns in a multi-storey prefabricated steel structure. The components within a module are welded together in the factory, and the modules are assembled on site using high-strength bolts. A rigid connection or a semi-rigid connection can be achieved by adjusting the number and size of bolts. The stiffness of semi-rigid bolted connection changes with the load. The connection is rigid during minor and moderate earthquakes, whereas during major earthquakes, the cover plate slips relative to the beam flange to dissipate energy. In this paper, model tests and finite element analysis (FEA) of the seismic performance under cyclic loads are conducted on six full-scale connections, and the results are compared with the results of a welded connection. The failure mode, slip behaviour, variation and distribution of the bolt tensions, and seismic performance of the connections, including the hysteretic behaviour, skeleton curve, ductility, rotational capacity and stiffness degradation, are obtained. The influences of the number of bolts and the thickness of cover plate on the mechanical and seismic properties are studied. The results show that a reasonable larger bolt hole can facilitate the installation and improve the ductility and energy dissipation capability without significantly affecting the load-carrying capacity of the connection. The results show that the proposed bolted connection has good hysteresis behaviour, energy dissipation and ductility. It is suitable for earthquake-resistant structures.

Seismic performance of prefabricated corrugated web beam-column joint with replaceable cover plates

Based on the idea of damage control, this article studied a new type of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joints. First, the constitution and advantages of prefabricated sinusoidal corrugated web beam-column joints were introduced. Then, finite element models are developed based on the design theory, and the hysteretic behaviour of prefabricated sinusoidal corrugated web beam-column joints was investigated using the finite element method considering the effects of parameters such as the weakened form, thickness and unbolted length of the flange cover plate, the bolt hole form and the gap between the beams. Finally, cyclic loading test and repairing test were conducted on a basic specimen, and the rationality of the numerical analyses and the design theory were verified. It indicates that a properly designed prefabricated sinusoidal corrugated web beam-column joint has good bearing capacity and hysteretic behaviour with earthquake resilience. The thickness and unbolted length of the flange cover plate, the bolt hole form and the gap between the beams have significant effects on the seismic behaviour of the joint.