Panel Specimens Research Articles

Experimental and numerical analysis of novel multi-layer sandwich panels under three point bending load

In this study, mechanical behavior of multilayer corrugated core laminated composite sandwich panel subjected to quasi-static three-point bending is investigated experimentally as well as numerically. Parameters such as contact force, energy absorption and specific absorbed energy (unit mass energy) for different geometries of corrugated core (rectangular, trapezoidal and triangular) are studied during loading process and failure. Composite plates and corrugated cores have been manually made using ML506 epoxy resin with 15% hardener and 45% volumetric woven glass fibers. Experimental results show that multilayer sandwich composite panels not only strengthen the structure in the quasi-static three-point bending process, but also make the absorbed energy to grow significantly by increasing the contact force and displacement up to the complete failure. The main mechanisms of damage and failure of sandwich panel specimens during load bearing process are matrix cracking, fiber breakage, delamination, local indentation, global bending, crushing and buckling of cell walls and face sheet and core de-bonding. Rectangular geometry of corrugated core, in terms of energy absorption and specific energy exhibits better results in comparison to other shapes. Numerical simulation using ABAQUS FEA package led to results, which are in good agreement with experimental ones and make it possible to use simulation instead of costly tests for analysis and design.

Flexural performance of precast concrete insulated wall panels with various configurations of ductile shear ties

This paper presents an experimental evaluation of the flexural response of non-load bearing precast concrete insulated partially-composite wall panels fabricated with varying layouts of ductile shear ties. The out-of-plane, one-way, single span load-displacement relationship is obtained for each panel via experimental pseudo-static flexural testing using a water bladder apparatus. Panel specimens constructed with several tie layouts are examined for potential improvements in flexural performance relative to current construction methods. The influence of the shear tie pattern, insulation type, and concrete-insulation interface are examined. Results indicate that placement of additional ties in regions with higher shear demands can enhance the overall flexural capacity and ductility of the panel. Test results show good agreement with partially-composite numerical predictions of both flexural capacity and deflection ductility. Panel deformation histories including full deflected shapes are used to develop deformation-dependent load-mass transformation factors for blast-resistant design via dynamic analysis. Lastly, the strain energy of each panel at several flexural load-deflection milestones are calculated as a preliminary approximation of the blast resistance of each panel.

Life Prediction for Anticorrosive Coatings on Steel Bridges

This paper presents the results of the effects of tensile stress and corrosion environment on the performances of epoxy (EP) coating systems and fluorocarbon (FC) coating systems on steel bridge by accelerated exposure test. Gloss, color characteristic parameter, and blistering area were selected to be aging indexes of anticorrosive coatings. Four different stress levels were applied on coated steel panel specimens by using a three-point bend loading, and the stress coefficient is proposed in this paper. The results showed that coating corroded more severely in seawater than in freshwater. The tensile stress may accelerate the degradation of the coating. The degree of corrosion damage of the coatings increased with the increase of stress levels. Natural exposure tests of EP and FC coating systems were performed at Sanya test site and Qingdao test site in China, respectively. The correlation between natural exposure test and accelerated exposure test is presented by the acceleration coefficient. A life prediction model of anticorrosive coatings on steel bridge is proposed. The stress coefficient was presented in the life prediction model. The stress coefficient increases with the increase of stress applied on coatings. The proposed life prediction model can provide an important basis for quantitatively describing the failure of anticorrosive coatings and predicting the life of anticorrosive coatings on steel bridges.

Hygrothermal characterization and modeling of cross-laminated timber in the building envelope

Cross-laminated timber (CLT) is a type of mass timber panel used in floor, wall, and roof assemblies. An important consideration in design and construction of timber buildings is moisture durability. This study characterized the hygrothermal performance of CLT panels with laboratory measurements at multiple scales, field measurements, and modeling. The CLT panels consisted of five layers, four with spruce-pine-fir lumber and one with Douglas-fir lumber. Laboratory characterization involved measurements on small specimens that included material from only one or two layers and large specimens that included all five layers of the CLT panel. Water absorption was measured with panel specimens partially immersed in water, and a new method was developed where panels were exposed to ponded water on the top surface. This configuration gave a higher rate of water uptake than the partial immersion test. The rate of drying was much slower when the wetted surface was covered with an impermeable membrane. Measured hygrothermal properties were implemented in a one-dimensional transient hygrothermal model. Simulation of water uptake indicated that vapor diffusion had a significant contribution in parallel with liquid transport. A simple approximation for liquid transport coefficients, with identical coefficients for suction and redistribution, was adequate for simulating panel-scale wetting and drying. Finally, hygrothermal simulation of a CLT roof assembly that had been monitored in a companion field study showed agreement in most cases within the sensor uncertainty. Although the hygrothermal properties are particular to the wood species and CLT panels investigated here, the modeling approach is broadly applicable.

Implications of impact experiments on honeycomb shielded exterior beam-column joint

The response of building structures under impact loads is a challenging subject for both numerical and analytical studies, as the available experimental data is limited. In the current research, an attempt was made to study the experimental investigation on the exterior beam-column joint against accidental and intentional impact loading. The velocity regime of the projectile was considered in the range 30–34 m/s. The response of the structural member shielded with the Aluminum honeycomb sandwich panel was compared with the unshielded beam-column joint. The target damage, failure modes, energy absorption, and evolution of cracks were examined in terms of both analytically and experimentally. Results obtained from high-speed imaging were used to obtain the projectiles incident, residual, and re-bound velocities. The application of honeycomb shielding on the seismic group specimens shows that the ballistic limit was increased by its energy absorption characteristics. It was found that they have a 22% higher ballistic limit than that of the seismic group specimens without honeycomb shielding. The shielded honeycomb sandwich panel specimens show promising results as they absorbed 49% higher impact energy than that of seismic specimens without honeycomb shielding. The current study provides a valuable reference for designing of honeycomb panels as a sacrificial material to safeguard the engineering structures against impact loads in the intermediate velocity regime.

Experimental Study on the Cyclic Behavior of Integrated Panels for Cold-Formed Steel Shear Wall System

Studies on the constructability of cold-formed steel (CFS) members are lacking. In this context, this paper proposes an integrated panel to replace the studs and steel sheet in the steel-sheathed wall system used in light gauge steel frames. The integrated panel was developed, to not only exhibit better structural performance and constructability than the steel-sheathed wall system, but to also reflect the appropriate details for applications to on-site panel construction. Cyclic loading tests were performed to investigate the seismic performances of three integrated panel specimens and a steel-sheathed panel specimen. The integrated panel specimens exhibited greater deformation capacity, ductility and equivalent damping ratio than the steel-sheathed panel. Although the web slenderness of the integrated member was nearly 400, the nominal strength of the integrated panel was predictable on an AISI standard. However, for stud-reinforced integrated panels, the nominal strength was overestimated by 45%–60%, and a draft equation was proposed to predict the yield strength of these panels. The proposed equation accurately predicted the yield strength of the stud-reinforced integrated panel specimens. The study results can aid in the construction of light gauge steel frames that require reinforcing parts with a high web slenderness ratio.

Fluorescent concrete with strontium phosphorus powder and plastic waste

Concrete as a structural material can also function in the aesthetic field. The use of fluorescent concrete can beautify buildings, roads and other construction buildings with concrete material. The use of plastic waste has added value to this concrete because it can reduce environmental damage. So that beautiful, environmentally friendly concrete is expected to be created. This research was carried out in the hope of utilising strontium phosphorus powder and plastic waste to increase the value of concrete benefits. The research that will be carried out consists of several stages. First, the problem identification phase and the materials were making up the concrete, so that the characteristics of the material can be known. The second stage is the concrete mix design using SNI 03-2834-2000 guidelines. The third stage is making the compressive strength and concrete panel specimens carried out in the laboratory. The fourth step is testing the compressive strength and concrete panel specimens and analyzing the test results. Concrete test results show that the more the percentage of strontium phosphorus powder instead of cement, the lower the compressive strength of the concrete. For the percentage of concrete plus 4% plastic waste and 5%, strontium phosphorus powder has a compressive strength of 11.69 MPa compared to normal concrete 26.03 MPa. Then the longest time the fluorescent concrete produced by panel concrete plus cement paste 10% strontium phosphorus powder is for 3 hours.

Performance comparison of next generation sequencing analysis pipelines for HIV-1 drug resistance testing

Next generation sequencing (NGS) is a trending new standard for genotypic HIV-1 drug resistance (HIVDR) testing. Many NGS HIVDR data analysis pipelines have been independently developed, each with variable outputs and data management protocols. Standardization of such analytical methods and comparison of available pipelines are lacking, yet may impact subsequent HIVDR interpretation and other downstream applications. Here we compared the performance of five NGS HIVDR pipelines using proficiency panel samples from NIAID Virology Quality Assurance (VQA) program. Ten VQA panel specimens were genotyped by each of six international laboratories using their own in-house NGS assays. Raw NGS data were then processed using each of the five different pipelines including HyDRA, MiCall, PASeq, Hivmmer and DEEPGEN. All pipelines detected amino acid variants (AAVs) at full range of frequencies (1~100%) and demonstrated good linearity as compared to the reference frequency values. While the sensitivity in detecting low abundance AAVs, with frequencies between 1~20%, is less a concern for all pipelines, their specificity dramatically decreased at AAV frequencies <2%, suggesting that 2% threshold may be a more reliable reporting threshold for ensured specificity in AAV calling and reporting. More variations were observed among the pipelines when low abundance AAVs are concerned, likely due to differences in their NGS read quality control strategies. Findings from this study highlight the need for standardized strategies for NGS HIVDR data analysis, especially for the detection of minority HIVDR variants.

An energy dissipating hold down device for cold-formed steel structures

A two-phase experimental investigation has been conducted for the development and evaluation of a hold down device that has energy dissipating feature. Focus of the first phase was the development of the device itself, while the second phase concentrated on the investigation of the performance of this device when used in a CFS framed sheathed wall panel that is subjected to reversed cyclic lateral loading. Hold down subassembly test results indicate that the load capacity of the hold downs is mostly limited by the shearing capacity of connection screws. Hold down devices themselves were observed to remain virtually undamaged under tensile loading, indicating a superior mechanical behavior in terms of strength and stiffness. As part of the second phase of the study, cyclic lateral load tests were conducted on seven CFS framed sheathed wall panels in order to study the energy dissipation ability of the proposed hold down device when used in CFS wall systems. Aligned with this focus, the anchor rods used to connect the hold downs to the foundation system in wall panel specimens were altered mainly by reducing the rod diameter within the middle portion over a certain length to provide controlled rod yielding under tensile forces. Controlled yielding of anchor rods was observed to reduce the drift demands imposed on wall panels due to seismic effects, resulting in a minimal damage on wall panels themselves.

Dynamic Responses of Sandwich Cemboard-Foamed Concrete Panels Subjected to Low-Velocity Impact

Sandwich cemboard-foamed concrete panel (SCFCP) has sparked the attention due to green and sustainability requirements in construction of building. SCFCP is essentially made of fiber cement board as core component and foamed concrete as outer layers. Shear connectors act as joint mechanism and create compositeness behaviour. However, investigations on SCFCP remains passive, creating a number of uncertainties particularly in dynamic responses. Therefore, this study intends to investigate the dynamic responses of SCFCP under low-velocity impact. Nine cube specimens were prepared using size of 100 mm x 100 mm x 100 mm, while nine panel specimens were casting using size of 1220 mm x 300 mm x 76 mm. The compression and impact tests were conducted on cube and panel specimens. The compression test revealed that foamed concrete has compressive strength approximately 18 MPa with density of 1600 kg/m3. Under low-impact of 1.39 m/s, it is noticeable that the impact force decreases from 8.41 kN to 6.73 kN in correspond to the spacing of shear connector. Contradictory, the displacement shows sprang off pattern with value between 87.90 mm to 96.50 mm.

Experimental study to measure the transmission loss of double panel natural fibers

In this paper, the transmission loss (TL) of the natural fiber materials will be measured experimentally at one third octave band harmonic and broadband frequencies. The different natural fibers used in this study are jute fibers, kenaf fibers, banana fibers, coconut coir fibers, and hemp fibers. An acoustic soundproof cabin has been fabricated to measure the transmission loss of natural fiber material. A one-dimensional duct is placed inside the soundproof cabin. Inside the duct there is a specimen of natural fiber materials. A loudspeaker is used to generate acoustic harmonic and white noise disturbances at various frequencies. The generated acoustic sounds then passed through the double panel natural fiber specimens. A sound pressure level (SPL) meter is used to measure the noise levels inside the duct. In this paper, a double panel natural fiber material specimen is proposed for testing. The double panel specimens are a combination of two natural fiber materials. In the double panel, the two panels are made from same or different natural fibers and also air is enclosed between them. The main objective of this paper is to measure the transmission loss and equivalent continuous A-weighted sound pressure level of fiber-air-fiber type specimens so that in future these types of combinations can be used for various engineering and other applications. It is observed that the combination of jute-air-kenaf is absorbing more sound as compared to jute-air-banana fibers and hemp-air-coconut coir fibers.

Experimental Research on the Shear Performance of the Two-Storey Composite Cold-Formed Thin-Walled Steel Wall

The composite wall made of the cold-formed thin-walled steel has good shear performance. When it is used in buildings, its weak part is located at the joint of floors and becomes the first broken part under the action of the earthquake. The shear test of five Two-storey Composite Cold-formed Thin-walled Steel Walls (TCS) under cyclic loading has been carried out. The influences of axial pressures, types of anti-pulling bolts and panel materials on shear performances are examined. The results show that under the same working condition, the energy dissipation capacity of calcium silicate panel specimens is significantly lager than that of the gypsum panel specimens, and the ultimate bearing capacity is also greater. The axial pressure has a great influence on the ultimate bearing capacity and energy dissipation capacity of the specimens. Compared with the specimens designed according to the Ref. (JGJ227-2011, 2011), the energy dissipation capacity of all specimens is increased by 3.25 times. The extrusion between the self-tapping screw and the wall panel causes the screw to fall off, resulting in a sharp decrease in the rigidity of the specimens at the initial loading stage. After the failure of the wall panel, the bottom and top beam are restricted by double nuts of the anti-pulling bolt at the joint of floors, so the bearing capacity of specimens decreases slowly at the later loading stage. The tilt angle of anti-pulling bolt increases when the TCS wall is loaded to the later stage. The force state of the self-tapping screw on the hold-down is changed from bearing shear force to bearing tension and shear force, resulting in fast failure of the anti-pulling bolt suit. The load borne by the anti-pulling bolt suit is transferred to floor beams and their supporting stiffeners, causing them to collapse rapidly.

Computer vision–based damage and stress state estimation for reinforced concrete and steel fiber–reinforced concrete panels

This article presents a computer vision damage assessment approach that relates surface crack patterns to damage levels and stress state characteristics in conventionally reinforced concrete and steel fiber–reinforced concrete panels. Previous studies have focused on crack patterns for specific structural element types such as beams and columns, but this study considers stress states in a more general framework. In particular, image data from previously published panel test specimens subjected to nominally constant stress have been collected to develop image-based estimation models capable of quantifying damage levels and stress components for full-panel crack patterns, and to investigate subimage sampling strategies to approximate full-panel results using partial-panel images. The objective here is to show that the analog of representative volume elements can be extended to image-based analysis contexts. The image datasets used in this article have been obtained from five different published studies, which provided 189 crack pattern images captured from concrete and steel fiber–reinforced concrete shear panel specimens. Given the limited size of the dataset, a feature-based computer vision approach has been used, with various geometric attributes of surface crack patterns used to train the estimation models. Within the limits of the data available, the preliminary results presented here indicate that quantifiable correlations exist such that stress state and damage level estimation models are valid across a range of loadings (i.e. reverse cyclic and monotonic) and materials (reinforced concrete and steel fiber–reinforced concrete), and that with appropriate sampling techniques, it is possible for subsampled images to yield estimations similar to full-panel results. These localized correlations between crack patterns and stress states potentially could be used in broader contexts for damage assessment of more general reinforced concrete and steel fiber–reinforced concrete members.

KUAT LENTUR PANEL DINDING BETON BUSA DENGAN LAPIS GRC DAN WIREMESH

Lightweight concrete is high in demand as it offers lighter specific gravity which makes the load on the structure smaller. In this research, lightweight concrete was produced by mixing water, cement, sand and foam. Besides aiming to obtain lighter specific gravity, the target of this research was also to design lightweight foam concrete with compressive strength equal to the one of commonly used materials for walls of around 3-5 MPa. However, foam concrete has relatively weaker tensile strength, that it would be inadequate when it has to hold the vertical force of the wall when it is applied as wall panels. This research was conducted to examine the flexural strength of the use of GRC coating and wiremesh for wall panels. Cylinder test was performed using tools with a size of 150 mm in diameter x 300 mm in length to analyze the modulus of elasticity at 28 days old, and three cubical test tools for each variance with a size of 50 mm x 50 mm x 50 were employed to test the tensile strength at 28 days old. A number of wall panel specimens with a thickness of 50 mm, width of 400 mm and length of 800 mm were used to measure the flexural strength. The tests performed in this research resulted in modulus of elasticity of 6856,6 MPa, tensile strength of 0,7 MPa. The flexural strength of wall panels without GRC outer layer and without wiremesh reinforcement was found at 1,5 MPa. Meanwhile, the flexural strength of the wall panel with GRC outer layer without wiremesh reinforcement was found at 4,6 MPa. Finally, the wall panel applied with GRC outer layer and wiremesh reinforcement showed a flexural strength 5,3 MPa.

Investigation of Mechanical properties of Glass Fibre Reinforced Honeycomb Panels

In this paper, detailed study and work have been done on the investigation of mechanical properties of glass fibre reinforced honeycomb panels. In this paper comparison between shredded E-glass fibre reinforced with polypropylene honeycomb panel and Woven E-glass fibre reinforced with polypropylene, honeycomb panel has been done. Fabrication of both types of specimens has been done using hand lay-up method. Specimens are machined into ASTM standards for testing. Tensile, flexural, Compressive, wear tests have been done. The density of the two specimens is calculated and compared. Wear test has been for different loadings (20N, 40N, 60N) and different rpms (200rpm, 400rpm, 600rpm) done on Pinion disk tribometer, flexural bending test has been done on three-point bending test machine. Tension and compression tests are done on a universal testing machine. In tension test, bending test and wear resistance the Woven E-glass fibre reinforced with polypropylene honeycomb panel specimen is having better results when compared with shredded E-glass fibre reinforced with polypropylene honeycomb panel. In compression applications, shredded E-glass fibre reinforced with polypropylene honeycomb panel is better than Woven E-glass fibre reinforced with polypropylene honeycomb panel.

Research on Buckling and Post-buckling Characteristics of Composite Curved Stiffened Fuselage Panel under Hoop Bending load

In order to study the buckling, post-buckling and failure modes of composite fuselage structures under circumferential bending loads, innovative four-point bending tests technology was developed and performed on composite curved stiffened fuselage panel (CSFP) specimens with two frame configurations of C-section and Z-section. Meanwhile, the stability engineering analysis and estimation based on plate buckling theory and simplified boundary were carried out, and the finite element (FE) models based on Hashin failure criterion were established to simulate the buckling, post-buckling and failure modes of CSFP specimens. The tests and analysis results show that the buckling modes and failure modes of C-section and Z-section specimens are different under positive bending loads. Specifically, the buckling of C-section specimens firstly occurs in the middle of the frame, then local buckling occurs at both ends of the frame, leading to fracture. For Z-section specimens, only local buckling occurs in the middle of the frame, which directly leads to fracture. By comparing the three methods, the results of FE analysis and engineering calculation are in good agreement with the test results. Among them, the prediction of instability mode and failure mode by FE method is very accurate, and the buckling strain calculated by engineering method can provide a good reference for structural design.

An analytical method for interpreting distortion effects on fatigue test results of thin plate panel specimens

This paper presents an analytical treatment of stress concentration caused by two dominant types of welding-induced distortions prevalent in thin plate structures, i.e., angular and buckling distortions. The use of these newly developed solutions is then demonstrated by their applications in analyzing some recent fatigue test data on thin plate specimens in which significant angular distortions were present in the form of local and angular distortions, as defined by Lillemae et al. (Int J Fatigue 44:98–106, 2012). In doing so, the stress concentration factor solution corresponding to global angular distortion given in BS 7910 (2013) incorporating nonlinear geometry effects is shown to be a special case of the present solution. Through a superposition scheme among local and global angular distortions, as well as axial misalignments, it is shown that the test data can be satisfactorily correlated with the 2007 ASME master S-N curve scatter band.

Experimental Investigation of High Strength Precast Reinforced Concrete Walls used (Vierendeel Truss Form)

This paper presents an experimental investigation to study the behavior of Vierendeel Truss used instead of bearing wall in precast construction. The experimental program contains casting and testing (8) R.C wall panels specimens with opening with right angle corner, the dimension of the opening (300*350*75) mm which it is length, width, and thickness. The dimension of the R.C wall panel specimens was (1000*750*75) mm which they are length, width and thickness, respectively and all the specimens contain cantilever portion (100*60*75) mm length width and thickness respectively. In this study the main variable is the type of concrete and the compressive strength. The wall panel specimens were tested with uniformly distributed load with an eccentricity of (67.5) mm. The specimens were simply supported to represent the supports of the truss. The wall panels were divided into (2) groups, the first group is reactive powder concrete with (4) specimens and the second group is high strength self-compacted concrete with (4) specimens. The failure load, load – deflection curves crack pattern was studied. All the panels were deflected in single curvature in the vertical direction of loading. Opening causes concentrated stress at the corners of opening and initiated the cracks and failure.

Far-sided defect recognition of FRP sandwich structures based on local defect resonance

This work provides a novel methodology to non-destructively detect far-sided defect of sandwich structures by local defect resonance-based acoustic activation. Sandwich panel specimens with 10 mm thick balsa wood core and 25 mm thick Nomex honeycomb core are investigated, and artificial facesheet-core disbond with a size of 30 mm × 30 mm is introduced to the specimens. Finite element modeling is constructed to investigate resonance frequency of defect region. Experimental apparatus is constructed to detect far-sided facesheet-core disbond defect, where vibration activation and measurement is performed at near-sided facesheet. It is shown that if the far-sided defect is activated at local defect resonance frequency, distinguishable nonlinear vibration characteristic could be observed from the near-sided facesheet, and the 3rd order superharmonic is especially significant. A stepped frequency sweep excitation approach is further developed for recognition of far-sided defect, which better fits automated defect detection process as local defect resonance frequency is not required to be preliminarily determined.

Clinical evaluation of multiplex RT-PCR assays for the detection of influenza A/B and respiratory syncytial virus using a high throughput system

BackgroundLower respiratory tract infections are a major threat to public health systems worldwide, with RSV and influenza being the main agents causing hospitalization. In outbreak situations, high-volume respiratory testing is needed. In this study, we evaluated the analytical and clinical performance of a pre-designed primer/probe set for the simultaneous multiplex detection of both viruses on a high-throughput platform, the cobas® 6800, using the “open channel” of the system for integration of lab-developed assays for the detection of influenza and RSV. ResultsUsing the influenza/RSV qPCR Assay with swabs, LoD (95%) in TCID50/mL for influenza-A was 0.009, influenza-B 0.003, RSV-A 0.202, and RSV-B 0.009. Inter-run variability (3xLoD) was low (<1 Ct for all targets). Of 371 clinical respiratory specimens analyzed, results were concordant for 358 samples. The calculated sensitivity and specificity of the assay were 98.3% and 98.4% for Flu-A, 100% and 98.5% for Flu-B, and 98.6% and 99.7% for RSV. All quality assessment panel specimens (N = 63, including avian influenza strains) were correctly identified. None of the tested microorganisms showed cross-reactivity. ConclusionCompared with CE-IVD assays, the assay evaluated here showed good analytical and clinical sensitivity and specificity with broad coverage of different virus strains. It offers high-throughput capacity with low hands-on time, facilitating the laboratory management of large respiratory outbreaks.