Hollow Panels Research Articles

Load Capacity and Bending Strength of Double-Acting Friction Stir Welded AA6061 Hollow Panels

Aluminum alloy hollow panels are essential components in both civil and mechanical structures, such as building floors or large vehicle platforms. They enhance rigidity while staying lightweight and conserving material volume. In its application, this panel must be joined using welding methods. One common issue encountered in aluminum welding is the formation of porosity defects. Solid-state welding methods like Friction Stir Welding (FSW) can be a solution to address this problem. The FSW joining process on hollow panels cannot be completed in one welding operation due to their thickness. The FSW process must be performed on both surfaces, which requires a relatively long time. Therefore, FSW needs to be developed into a Double-acting FSW that utilizes two tools simultaneously. These two tools introduce two sources of heat input, pressing force, and friction-stirring, resulting in a novel response that needs further research. This study delves into the impact of welding speed variations in Double-Acting FSW on the load capacity and bending strength of AA 6061 hollow panel joints. Welding speeds of 20, 30, and 40 mm/min were tested alongside rotational speed (1500 rpm), tilt angle (2°), and shoulder diameter (24 mm). It was discovered that reducing welding speed enhances both load capacity and bending strength. Notably, specimens welded at 20 mm/min exhibited a load capacity of 15.61 kN and bending strength of 52 MPa, highlighting the potential of slower speeds for superior weld performance. Doi: 10.28991/CEJ-2024-010-08-018 Full Text: PDF

The Development of New Type GFRP Hollow Panels

Under the background of global energy transformation, pumped storage power stations are becoming more and more important. Most of their water retaining structures adopt face rockfill dams, but their concrete panels will have many problems such as durability. In this study, a new type of GFRP hollow panel was developed for face rockfill dam. The nonlinear behavior and damage process of the material were simulated by finite element analysis and UMAT subroutine. Through analysis and comparison, it is found that the triangular section form is superior to other forms in terms of stress distribution and bearing capacity. After optimization design, the optimal section takes into account the stability, safety and economic benefits of the structure. The research results provide a high-performance panel solution with high construction efficiency and low maintenance cost for the face rockfill dam, and provide an important design reference for the application of GFRP composite materials in water conservancy projects in the future.

Effect of tools rotational speed on the mechanical properties of one-step double-acting friction stir welded aluminum alloy AA 6061 hollow panel

The utilization of Aluminum hollow panels enhances structural strength while simultaneously ensuring a lightweight and efficient use of materials. During their application, these panels necessitate a welding process that is susceptible to porosity due to the disparity in hydrogen gas solubility between liquid and solid aluminum. Solid-state welding techniques, such as Friction Stir Welding (FSW), have proven to be effective and appropriate solutions for overcoming this issue. However, due to the thickness of the hollow panels, FSW process is unfeasible as it requires welding on both sides, resulting in prolonged production times. Consequently, the development of a one-step double-acting FSW technique becomes necessary, involving the simultaneous utilization of two tools. The usage of two tools introduces two sources of friction-stir forces, heat, and axial forces, demanding an assessment of the novel response from the specimens. This research aims to analyze the effect of a specific parameter, namely the tool rotation speed, within the one-step double-acting FSW process on the physical and mechanical properties of the AA6061 hollow panels. The One-Step Double-Acting FSW process involved conducting variations in the tool rotation speed on both sides of the welds. Specifically, for the 4G weld position (underside of the workpiece with an overhead weld position), speeds of 1200, 1500, and 1800 rpm were employed. Meanwhile, a consistent rotation speed of 1500 rpm was maintained for the 1G weld position (overside of the material with a flat weld position). The transverse speed and tilt angle are set at 30 mm/min and 2°, respectively. Elevating the tool rotation speed results in increased hardness, load capacity, and bending strength of the weld joints. The specimen subjected to the highest rotational speed (1800 rpm) exhibits the most exceptional mechanical properties, including a hardness of 73.46 HVN, load capacity of 18.47 kN, and bending strength of 60.56 MPa.

Effect of axial-load ratio and shear-span ratio on seismic behavior of the prefabricated structures for cast-in-place RC boundary elements confined uniform hollow panels

To meet the requirements of seismic safety, energy efficiency, and convenient transport, while achieving efficient construction of low or multi-story building structures. A prefabricated structure was developed with uniform hollow panels as the main force elements and cast-in-place RC provides restraint. The safety of the connection between the elements was verified by a low cyclic loading experiment and numerical analysis. In addition, the influence of the axial-load ratio and the shear-span ratio on the seismic performance of the structure was investigated, and the damage characteristics of progressive failure were revealed. The study found that as the axial-load ratio increased from 0.15 to 0.30, the cracking of the uniform hollow panels progressed, but the cracking of the columns was delayed, and the tendency of the edge member to separate from the uniform hollow panel increased. The ultimate lateral load capacity increased by 9.96 %, but the deformation capacity decreased, and the ductility coefficient decreased from 3.19 to 2.45. As the shear-span ratio decreased from 1.35 to 0.95, the uniform hollow panel and the structural columns cracked earlier and later, respectively, and the ultimate lateral load-bearing capacity increased by 25.03 %. However, the cracks at the base of the column increased, the deformation capacity decreased, and the ductility coefficient decreased from 3.19 to 2.15. Meanwhile, it is observed that the structure exhibits a three-stage progressive failure characteristic, i.e., the joint working stage, transformation transition stage, and weak frame stage. This greatly improved the deformation and energy dissipation capacity of the structure, which maintained good stability even when the inter-story displacement angle reached 1/50. This paper also established the calculation method for the lateral load resistance of this prefabricated structure, which showed accurate and reliable results. In general, the results of this research can provide an important reference for building design code and the application of this structure.

Experimental and numerical study on seismic performance of precast concrete hollow shear walls

Precast hollow shear wall structure is a new type of prefabricated shear wall structure. The wall of the structure is composed of precast hollow panels, cast-in-place boundary elements and cast-in-place vertical splice joints. The precast hollow panel is provided with vertical and horizontal holes, and concrete is poured at the construction site to form solid wall. Horizontally inserted reinforcement bars are arranged in the horizontal holes of the hollow panels, which are indirectly overlapped with the horizontally distributed reinforcement bars in the hollow panels to realize the connection of horizontal reinforced bars of adjacent hollow panels in the same story. In order to study the seismic performance of precast hollow shear wall, quasi-static tests were conducted on five hollow shear wall specimens with aspect ratio of 1.61 to 2.07. The experimental results showed that the specimens failed due to flexure-compression, which achieved the expected design target of “strong shear and weak bending”, and horizontal reinforcement indirectly connected by horizontal inserts could effectively resist horizontal shear force. The ultimate drift ratios of specimens ranged from 1.4% to 2.6%. The load-carrying capacity of the hollow shear wall could be calculated according to the formula for cast-in-place shear wall provided by the GB 50010–2010. Two kinds of connection between the hollow panels (direct splicing connection and cast-in-place vertical splicing connection) could make the hollow panels become a whole. The seismic performance of the hollow shear wall with precast boundary elements also met the requirements of the GB 50011–2010. Finally, the finite element model of shear wall specimen was established and verified using MSC.MARC software. On this basis, the impact of key parameters on the seismic performance of the precast hollow shear wall was studied. The results show that the axial load ratio and boundary longitudinal reinforcement ratio had great influence on the seismic performance, while the diameter of the steel bar inserted horizontally had little effect on the seismic performance of the precast hollow shear wall with higher aspect ratio.

Progressive Failure of Precast Shear Wall Structure for RC Composite Column Confined Uniform Hollow Panels under Cyclic Loading

To increase the assembly construction efficiency of low-rise and multi-story buildings in rural areas, the precast shear wall for RC composite column confined uniform hollow panels was designed in this paper. The seismic performance and failure mechanism of the structure are studied by combining low cyclic load test with finite element and theoretical analysis. The study found that the connection between the components is safe. The structure has three progressive failure processes that are the interaction stage, composite column constrained dense column work stage and weak framework stage. The structure has good bearing and capacity of energy dissipation, and the ductility coefficient of the specimen is 2.89. In addition, the finite element model is established based on ABAQUS, and the damage evolution process of the structure is visually represented by the damage nephogram. In combination with test and simulation, calculation methods of shear capacity of the shear wall are established. The ratio of test value to calculated value in the interaction stage and weak framework stage is 1.14 and 1.06 respectively. The calculation method is reliable and has clear physical significance. The study can provide a reference for the application in low-rise and multi-story buildings.

Exergy analysis of two indirect evaporative cooling experimental prototypes

This paper deals with the exergy analysis of two experimental prototypes consisting of indirect evaporative cooling systems with different constructive characteristics. Both prototypes have been designed and manufactured in the Thermal Engineering Laboratory of the University of Valladolid. They are made of polycarbonate hollow panels of different cross section and connected into a heat recovery cycle. Each prototype has been tested at 4 levels of outdoor air volume flow (from 125 to 400 m3·h−1) and 4 levels of dry bulb temperature (from 25 to 40 °C). For each of the 16 different operating conditions the exergy destructed by each prototype has been calculated. Results show that the higher the dry bulb temperature at the primary air inlet, the higher the exergy destruction and the exergy losses. The exergy destruction increases when the wet bulb depression temperature of the secondary air inlet decreases, leading to more inefficient configurations. The value of the exergetic efficiency is in the order of 2–12 %. The optimum combination of operating conditions at any inlet temperature of the primary air can be proposed as: 300 m3h−1 and 200 m3h−1. for the wide and narrow plates prototype, respectively.

Axial behaviour of precast concrete panels with hollow composite reinforcing systems

This study investigated the axial behaviour of precast concrete panels with hollow composite reinforcing systems (CRSs). These systems were provided to create voids, reduce the concrete and the self-weight of the panels. Thirteen specimens representing the unit width of a precast concrete panel were prepared and tested under concentric axial compression to investigate the effects of CRS spacing and slenderness ratio. From the experimental results, introducing the hollow core did not affect the stiffness of the panels due to the relatively small area of the hollow core at the middle of the section, while the axial capacity was reduced by 11%. On the other hand, the CRS increased the axial strength capacity and stiffness of the hollow panels by 70% and 71%, respectively as it provided additional reinforcement and stabilised the concrete core. Furthermore, narrower CRS spacing provided better structural performance than wider spacing due to the higher efficiency of the CRS and its flanges in holding together the cracked concrete. Moreover, the axial stiffness provided by the CRS prevented the global buckling failure of slender panels. Finally, a theoretical model was developed to predict axial load capacity by considering the contribution of the CRS and slenderness of the panels.

Flexural Strength Analysis of Styrofoam Concrete Hollow Panel Walls Incorporated with High Volume Fly Ash

Purpose: One of the innovations needed to create lightweight wall is possible by using Styrofoam as a partially fine aggregate substitution. This study was conducted to study the flexural strength of Styrofoam lightweight concrete panel walls with a high-volume fly ash content in a square column connection. Methodology: The size of the wall panel used is 120 x 30 x 10 cm with 10 x 10 cm square column holes as support on both sides. In the centre of the wall panel, four square holes with a dimension of 18 x 4 cm were created. The variations of fine aggregate replacement with Styrofoam were 50% and 60% by the volume of fine aggregate, while the use of Fly ash is 50% as partially cement substitution. SCC (Self Compacting Concrete) method was used to manufacture this kind of concrete. Results: The results of Slump Flow T50 test for 50% and 60% Styrofoam variations are 64 cm and 59 cm, while the concrete weight-volumes are1387.7 kg/m3 and 1259.4 kg/m3. Compressive strength test for both variations are 42.62 Kg/cm2 and 31.71 kg/cm2. Stiffness values for both variations are 1434.7 N/mm and 1125 N/mm. This study also analysed the maximum length of the panel wall in which for 50% Styrofoam variation is 4 m and 60% Styrofoam variation is 3.2 m. Applications/ Originality/ Value: Research on Styrofoam concrete hollow panel walls incorporated with high volume fly ash is significant since it opens the possibility to reduce the Styrofoam waste.

Formulation of an alternate concrete mix for concrete filled GFRG panels

Glass fiber reinforced gypsum panels (GFRG) are hollow panels made from modified gypsum plaster and reinforced with chopped glass fibers. The hollow cores of panels can be filled with in-situ concrete/reinforced concrete or insulation material to increase the structural strength or the thermal insulation, respectively. GFRG panels are unfilled when used as partition walls. As load bearing walls, the panels are filled with M 20 grade concrete (reinforced concrete filling) in order to resist the gravity and lateral loads. The study was conducted in two stages: First stage involves formulation of the alternate light weight mix by conducting experimental investigations to obtain the optimum combination of phosphogypsum and shredded thermocol. In the second stage the alternate mixes are filled in GFRG panels and experimental investigations are conducted to compare the performance against panels filled with conventional M 20 mix.

Experimental Investigation on Use of Shredded Thermocol to Formulate a Light Weight Concrete Mix for Concrete Filled GFRG Panels

Glass fiber reinforced gypsum panels (GFRG) are hollow panels made from modified gypsum plaster and reinforced with chopped glass fibers. The hollow cores inside the walls can be filled with in-situ concrete/reinforced concrete or insulation material to increase the structural strength or the thermal insulation, respectively. GFRG panels can be unfilled when used as partition walls, but when used as load bearing walls, it is filled with M20 grade concrete (reinforced concrete filling) in order to resist the gravity and lateral loads. The study was conducted in two stages: First stage involves formulation of an alternate light weight mix to be used in the GFRG panels in lieu of M20 grade concrete by partial replacement of cement with phosphogypsum and fine aggregate with shredded thermocol and thereby conducting experimental investigations to obtain the optimum combination. In the second stage the above formulated mix is filled in GFRG panels and experimental investigations are conducted to evaluate the strength parameters and the results are compared with the panels filled with conventional M20 concrete mix. The results of the first stage of experimental investigations are presented in this paper.

Wind Load Reduction in Hollow Panel Arrayed Set

Reducing the wind loading of photovoltaic structures is crucial for their structural stability. In this study, two solar panel arrayed sets were numerically tested for load reduction purposes. All panel surface areas of the arrayed set are exposed to the wind similarly. The first set was comprised of conventional panels. The second one was fitted with square holes located right at the gravity center of each panel. Wind flow analysis on standalone arrayed set of panels at fixed inclination was carried out to calculate the wind loads at various flow velocities and directions. The panels which included holes reduced the velocity in the downwind flow region and extended the low velocity flow region when compared to the nonhole panels. The loading reduction, in the arrayed set of panels with holes ranged from 0.8% to 12.53%. The maximum load reduction occurred at 6.0 m/s upwind velocity and 120.0° approach angle. At 30.00 approach angle, wind load increased but marginally. Current research work findings suggest that the panel holes greatly affect the flow pattern and subsequently the wind load reduction. The computational analysis indicates that it is possible to considerably reduce the wind loading using panels with holes.

Glass Furnace Controlling from Saving Energy Aspect

The article is the possibility of energy saving of glass furnaces Bonacci when operating. A proposal to energy saving is aimed at changing of the control process of furnaces and installation of closing doors inlet and outlet ports of furnaces. By inlet and outlet ports of these continuous furnaces considerably leaks thermal energy when are not used (i.e. breaks at work). The doors are designed as a hollow panel, which is filled by isolation. This leads to a considerable saving of energy and to reduce of operating costs. The current control process of furnaces is now obsolete and can not flexibly changed it according a change of manufacturing products. The newly designed controlling systems is controls not only the kinematics, i.e. moving actuator of glass, but also temperatures in furnaces and newly inlet and outlet doors for closing of holes.

Effect of stay-in-place PVC formwork panel geometry on flexural behavior of reinforced concrete walls

The use of stay-in-place (SIP) formwork has become an increasingly popular tool for concrete structures, providing advantages in construction scheduling and labor reduction. Previous research suggests that PVC provides an enhancement to reinforced concrete strength and ductility. The research herein outlines tests on reinforced concrete walls with a compressive strength of 25MPa, utilizing two types of PVC panels: flat or hollow, in order to further understand the polymer's contribution to flexural resistance. Variables studied included concrete core thickness (152mm, 178mm, and 203mm), reinforcing ratio (3–10M bars or 3–15M bars), and panel type (hollow or flat). The walls were tested in four point bending. Walls failed due to steel yielding followed by concrete crushing, PVC buckling, and/or PVC rupture depending on the reinforcement ratio and panel type. The hollow panel encased specimens also experienced slip of the panels on the tensile face. The PVC encasement enhanced the yield load, ultimate load, ductility, and toughness of the concrete walls. Concrete cores were taken from the tested PVC encased specimens and compressive strength was found to be the same as the control walls.

In situ measurement of thermal transmittance and thermal resistance of hollow reinforced precast concrete walls

A study was conducted to determine the in situ thermal transmittance and thermal resistance of two exterior reinforced precast concrete walls of a building constructed with hollow panels. The results indicate that the North and East facing walls have a mean thermal transmittance (air to air) of 1.459 and 1.803W/m2K, respectively. The mean thermal resistance value (surface to surface) of the North and East walls is 0.355 and 0.352m2K/W, respectively. While the thermal transmittance depends on the wall orientation and the outside weather conditions, the thermal resistance is independent of the wall orientation. The results also indicate that a monitoring period of six days is sufficient to ascertain the in situ thermal transmittance and thermal resistance of reinforced precast concrete walls.

Structural performance of prestressed façade limestone panels

Experimental studies on the behaviour and performance of prestressed natural stone hollow panels were performed using prestressing wires as internal tendons to apply a compression force to pre-assembled dimension stone slabs forming the panels. Six prototypes were subjected to three-point bending and vibration tests, and the effect of filling the panel void with polyurethane and of the prestressing intensity was also studied. Dynamic tests were performed to obtain the panel’s self natural period of vibration and the natural stone’s Young’s modulus. Static load tests were performed to ascertain the panels’ suitability for application as stand-alone facade panels. The experimental results revealed two distinct failure modes after cracking, depending on whether polyurethane infill was injected into the void. The post-rupture behaviour was analysed taking into account the favourable effect of filling the panel void with polyurethane foam. Finite element computer analyses of the stress states induced in the panels were also carried out for three different geometries. Data obtained from specimens subjected to the same load regime were compared.

Influence of constructive parameters on the performance of two indirect evaporative cooler prototypes

Two equally-sized cross-flow heat-exchanger prototypes have been designed with a total heat exchange area of 6 m2 and 3 m2 respectively, constructed with polycarbonate hollow panels of different cross section. They are connected into a heat-recovery cycle within the whole experimental setup constructed for the tests, which mainly consists of: an Air Handling Unit to simulate the outdoor airstream conditions, a conditioned climate chamber, and a water circuit to provide the water supply required. They have been experimentally characterised in two operating modes in order to determine how evaporative cooling improves heat recovery in each case, focussing on the influence of modifying the constructive characteristics. To perform the evaporative cooling process, water is supplied to the exhaust airstream. Results are studied considering how constructive issues, outdoor air volume flow rate and temperature, as well as operating mode influence on the performance obtained. An Analysis of Variance shows how outdoor airflow has a key role in the performance of the systems; whereas entering outdoor air temperature determines cooling capacities. Improvements introduced by larger heat exchange areas compensate with their corresponding smaller cross sections, which hinder water–air distribution on the exhaust air side of the heat exchanger. Finally, these small devices achieve cooling capacities of up to 800 W, being able to partly support ventilation load and achieving around 50% of energy saving in ventilation cooling.

Different Types of Pre-Stressed Hollow Core Panels and Their Fire Resistance According to Eurocodes

The authors' work deals with the calculation of the fire resistance of pre-stressed hollow panels. The thermal characteristics of air in the hollows were determined on the basis of testing the fire resistance of two Spiroll panels, thickness 250 mm, with hollows with circle section. The thermal characteristics of the air in the hollows were used to compare the fire resistance of similar pre-stressed panels with different hollows, thickness 200 mm; Echo with hollows with oval section and Elematic with hollows with circle section. Furthermore the fire resistance is analysed in term of the concrete cover; a smaller concrete cover responds to a higher load-bearing capacity for a permanent design situation but decreases the final fire resistance. The calculated fire resistance is compared with the fire resistance determined by testing, if the results are available.

Theoretical analysis and experimental study of hollow acoustic panel

Noise control is important and essential in the electromechanical system; where the industrial health, system maintenance, and operation safety are significantly considered. Therefore, the design expense and the endurance limit of the acoustic hood are mostly focused in the industry. In this study, three types of hollow RCpanels are introduced as the acoustic hoods, and the sound absorbing as well as the insulation characteristics are experimentally addressed and compared to the traditional acoustic hood with absorbing wool. The mathematical model and the sound absorption coefficient under various frequencies for the hollow panels are theoretically constructed as the primary criterion. Additionally, a noise source from the real-world electromechanical system is selected and motivated in a designed hollow hood for the experimental research. With the laminar flow of the air in the hollow panel, the sound absorbing and insulation are then manipulated. Moreover; different fillings (air and wool) in the hollow panel are studied and compared for the effectiveness in noise insulation, and the experimental sound power level is introduced into the theoretical modeling of sound absorption. Thus, the sound absorption coefficient of the hollow acoustic panel is furthermore inversely obtained. This paper surely contributes a simple and concrete modeling technique of sound insulation for hollow acoustic panels, as well as provides the comparison for three types of acoustic panels in sound transmission loss and sound insertion loss. The adaptability and applicability of the hollow acoustic panel are found precious to be expanded through this study.

The effect of longitudinal reinforcement on the cyclic shear behavior of glass fiber reinforced gypsum wall panels: tests

Glass fiber reinforced gypsum (GFRG) walls are new building materials that have been used in Australia and a few Asian countries for the past decade. GFRG walls are hollow panels that are prefabricated in factories and tailored to the design of each specific wall. The hollow cores inside the walls can be filled in situ with reinforced concrete or materials such as insulation to increase the structural strength and the thermal or sound insulation, depending on the design needs. GFRG walls can be used for various structural elements, such as walls and slabs. In Australia, GFRG walls are often used as wall panels for low-rise residential constructions, in which starter bars are inserted into the concrete-filled cores to connect the walls to the floor. The longitudinal reinforcement is therefore discontinuous along the height of the wall. The continuity of the longitudinal reinforcement is important for multi-story GFRG buildings from the point of view of both structural integrity (robustness) and flexural resistance. However, this continuity is considered to be unnecessary in low-rise residential constructions, and starter bar connections are generally accepted in practice. Cyclic shear tests were conducted in this work to study the effect of reinforcement continuity on the performance of shear-dominated GFRG walls.