Composite Load Research Articles

Scour effects on the bearing capacity of multi-bucket jacket foundation for offshore wind turbines

The Multi-Bucket Jacket Foundation (MBJF) is presently being installed in Chinese wind farms with increasing numbers. Compared to monopiles, MBJF is a shallow foundation and the effect of scouring on the bearing capacity is more significant. This research proposes a universal three-dimensional model of the MBJF with local scour to efficiently estimate the effect of scouring on the MBJF bearing capacity. Firstly, using the proposed model, the ultimate bearing capacity is calculated under a single load, and the discounting effect of different scour ranges and scour depths on the ultimate bearing capacity is evaluated. Furthermore, the fixed load-displacement approach is used to calculate the failure envelope of the foundation under composite loading mode, and the influence of different scour patterns on the failure envelope is compared. The findings reveal that when the scour extent and depth increase, the foundation's bearing capacity decreases non-linearly, and the foundation bearing envelope line gradually shrinks. Under the condition that the ultimate vertical load is not exceeded, a rise in vertical load can enhance the ultimate load capacity after scouring to a certain extent. Finally, the calculated envelopes are integrated with engineering applications to quantify the safety redundancy of the MBJF bearing capacity for different seabed morphologies. The method and results can provide methodological support for the accurate prediction and efficient assessment of the MBJF's post-scour bearing capacity.

Study on the correlation between the puncture impact performance of arc-shaped bamboo splits and bamboo ages

The unique hierarchical gradient structure of bamboo from the macro to nano scales and its remarkable combination of vascular bundles and parenchyma provide its high strength and toughness. Bamboo is an excellent engineering material that is widely used in construction and transportation, and its impact performance is an important indicator that reflects its structural stability. In this study, the finite element method was used to analyze the mechanical characteristics of bamboo splits under impact in simulations, and arc-shaped bamboo splits were tested to assess impact performance under puncture, thus, clarifying the relationship between bamboo age, density, and chemical composition and fracture load. As the bamboo age increased (from 2 to 4 and 8 years), the maximum impact load of bamboo first increased and then decreased. The maximum impact load of 4-year-old bamboo was 4373 N, which was 1.79- and 1.70-fold that of 2- and 8-year-old bamboo, respectively. Although the maximum impact load of 2-year-old bamboo was lower than that of 4-year-old bamboo, it nevertheless withstood secondary loads after fracture and was highly tough. Specimens exhibited both transverse and intergranular impact fractures, but the latter category comprised most of the fractures. The crack deflection, fiber stripping, and crack bridging caused by the gradient structure of bamboo enhanced its fracture load. There were clear correlations between the maximum load of bamboo impact and the density, moisture content, and chemical composition of bamboo. The establishment of structure–activity relationships between the bamboo impact load and physicochemical properties can guide the engineering applications of bamboo and provide a reference for biomimetic materials.

Study on properties of Ca0.9La0.067TiO3‐0.01Al2O3 ceramics reinforced PSAE/fiber composite substrate with high εr

AbstractA “self‐permeation” method was used to fabricate a Ca0.9La0.067TiO3‐0.01Al2O3 (CLT)‐reinforced polysilylaryl‐enyne/fiber multilayer board with different volume fractions of CLT (0–40 vol%). The microstructure, dielectric, mechanical, and thermal properties were fully studied. The results showed that the composite with optimal dielectric properties (εr∼8.75, tanδ∼0.0043) could be obtained when the volume fraction of CLT reached 30 vol%. Meanwhile, the thermal conductivity reached a high level of 0.644 W/(m·K) and 0.762 W/(m·K) at Z and X/Y directions, respectively. Due to the high decomposition temperature of PSAE, Td5 (the temperature corresponding to 5% weight loss) of composite loading with 30 vol% CLT was higher than 900℃, which indicates an excellent thermal resistance. And the bending strength could reach 115.3 MPa indicating excellent mechanical property. The novel polysilylaryl‐enyne/fiber/Ca0.9La0.067TiO3‐0.01Al2O3 multilayer board with excellent performance is expected to be a candidate material for print circuit boards and widely used in the microwave communication field.

Abstract 305: Novel nanoformulation of piperlongumine for pancreatic cancer therapy

Abstract Background: Pancreatic cancer (PanCa) is expected to be the second leading cause of cancer-related death by 2030. The treatment of PanCa is highly challenging due to the extremely poor response to existing therapeutic options. Highly desmoplastic tumor microenvironment in pancreatic tumor causes suboptimal delivery of therapeutic agents in tumors that eventually resulted to chemo-resistance. Piperlongumine (PL) is a natural alkaloid isolated from the long pepper, Piper longum L., and has shown substantial cancer-preventive and therapeutic efficacy against variety of cancers. However, delivering its effective concentration in pancreatic tumors has been challenging. In this study, we have synthesized and characterized a novel nano-formulation of PL composed of a PLGA core (PLGA-PL), stabilized with polyvinyl alcohol (PVA) and coated with poly-L-lysine (PLL), and evaluated its therapeutic effects against PanCa. Methods: The various physicochemical approaches (FT-IR, DSC, TEM, TGA, and HPLC) was used to characterize the PLGA-PL formulation for particle size, chemical composition, and drug loading efficiency. Cellular uptake of PLGA-PL was achieved in incubation with PLGA-PL in PanCa cells. Further, the therapeutic efficacy of PLGA-PL was determined by using various in vitro assays (MTS, wound healing, boyden chamber, cell cycle and apoptosis assays) using PanCa cells. The effects of PLGA-PL on various key oncogenic signaling pathways were evaluated by qRT-PCR, Western blot, confocal microscopy, immunohistochemistry (IHC) analyses. Results: Our novel PLGA-PL formulation has an average size of 110 nm in dynamic light scattering and a zeta potential range of -6.52 to -7.68 mV with excellent PL loading efficiency. Cellular uptake and internalization studies show that PLGA-PL escapes lysosomal degradation, allowing for effective endosomal release into the cytosol. PLGA-PL showed superior anti-cancer activity in various PanCa cells (BxPC-3, HPAF-II, AsPC-1, Panc-1, and MIA PaCa-2) compared to free PL. Moreover, PLGA-PL showed a remarkable inhibition of the migration and invasion potential of PanCa cells. Furthermore, PLGA-PL more effectively inhibited the components of the Shh pathway and Gli targets as determined by qPCR and Western blot analysis. Additionally, PLGA-PL treatment targets cancer stem cells by regulating pluripotency, maintaining stemness factors (Oct-4, Sox2, Nanog and c-Myc), and limiting tumor sphere formation. Conclusions: Taken together, our results demonstrate that PLGA-PL nanoformulation exhibits superior anti-cancer potential than free PL against and could be used as a novel therapeutic modality for the management of PanCa. Citation Format: Vivek Kumar Kashyap, Godwin P. Darkwah, Swati Dhasmana, Neeraj Chauhan, Anupam Dhasmana, Sudhir Kotnala, Partha Laskar, Mohammed Sikander, Bilal B. Hafeez, Murali M. Yallapu, Meena Jaggi, Subhash C. Chauhan. Novel nanoformulation of piperlongumine for pancreatic cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 305.

Natural rubber reinforced with super-hydrophobic multiwalled carbon nanotubes: obvious improved abrasive resistance and enhanced thermal conductivity

Abstract Polyurethane chain was successfully grafted onto carbon nanotubes, affording polyurethane-functionalized multiwalled carbon nanotubes (P-MWCNTs) with super-hydrophobic property, which shows improved abrasive resistance obviously and enhanced thermal conductivity for natural rubber (NR) vulcanizate. Under the optimized conditions, the akron abrasion loss of NR vulcanizate combined with 5 parts per hundred rubber (5 phr) P-MWCNTs is 0.9 cm3/1.61 km compared to 2.96 cm3/1.61 km of pristine NR vulcanizate. The thermal conductivity of NR vulcanizate combined with 5 phr P-MWCNTs has been improved by 40.3% compared to that of pristine NR vulcanizate. The decreased height of the maximum tan δ peak shows that P-MWCNTs can reduce the heat buildup and damping capability of NR/P-MWCNTs composites. The good dispersion of P-MWCNTs with a continuous network, particularly at high loading (5 phr) in the NR composites, was evidenced from transmission electron microscopy (TEM).

Enhanced Interfacial Integrity for Chain Growth Polymer Carbon Fiber Composites via Surface-Initiated Polymerization

The interface between carbon fiber (CF) and a polymer matrix is critical for the transfer of load in CF-reinforced polymer composites. Surface functionalization via covalently grafted molecules has been a successful strategy for enhancing the interfacial integrity of epoxy-based composites. In contrast, there has been limited application to composite resins based on chain-growth polymerization mechanisms, such as vinyl ester resins, due to challenges in their experimental evaluation. Here, we introduce a concept to systematically enhance and tailor the interfacial mechanical properties of these composites based on short, surface-grown polymers. All-atom molecular dynamics simulations reveal how the complexities of the cross-linking network, both among the surface-grown chains and between the surface chains to the bulk resin, are critical to securing a robust interfacial mechanical response under shear. These key traits, obtained from molecular-level insights, provide practical guidance for using surface-initiated polymerization to optimize the interface, expanding the range of applications for these challenging composites based on chain-growth resins.

A miniaturised mono‐cone antenna with top plate and composite lumped loading

A wideband mono-cone antenna is proposed. Evolution from a top-loaded mono-cone, the top plate is etched by two rings and loaded by an array of resistors and inductors. This design improves impedance matching properties in the low frequency range while maintaining a compact size. An equivalent circuit modal is built for assisting the antenna design. A prototype is fabricated and measured for verification. The antenna operates in the frequency band of 118–1100 MHz with |S11|≤-10 dB and the fluctuation of omni-directional radiation pattern ≤ 2.5 dB. The occupied area of the antenna is 0.24 λL × 0.24 λL × 0.06 λL, which is attractive for use on aircraft.

The Large Deflection Solution of Circular Elastic Membrane under Composite Loads

In this paper, the large deflection problem of axisymmetric isotropic elastic membranes subjected to the composite loads is studied. The Hencky transformation is extended and the general solution of large deflection of the membranes under the composite loads is obtained. The general solution is given in different forms in different values of loads. The obtained results of the numerical values of elastic characters can be applied in practice.

Environmental degradation and mechanical behavior of glass fiber reinforced polymer nanocomposites used in offshore applications

Present study aims at the variation of mechanical properties of glass fiber/epoxy composite under the effect of temperature, alkalinity, and rate of loading. Glass fiber reinforced polymer (GFRP) with plain epoxy and GFRP with 1–2% variation of Nanoclay were utilized for experimentation. Flexural testing of specimen at optimum percentage of Nanoclay in GFRP and epoxy was performed and after that pre-stretching of GFRP with plain epoxy and GFRP with optimum percentage of Nanoclay was conducted. Combined effect of moisture, alkali, and temperature on the degradation behavior of glass fiber reinforced polymers in different environments was studied. The macroscopic and microscopic behavior of the GFRP composite specimen and pure epoxy and Nanoclay reinforced epoxy exposed to varying hygrothermal loads has also been analyzed. Scanning electron microscope (SEM) was used to study the microscopic behavior of GFRP composites. X-Ray diffraction analysis of epoxy with 1%, 2%, and 3% Nanoclay addition was also performed. Tensile and flexural testing of specimen at different orientations such as 0°, 30°, 45°, 60°, and 90° were also studied. At 0° orientation, maximum average flexural strength of 295.04 MPa and 481.69 MPa was observed for plain glass fiber reinforced polymer and 2% Nanoclay/glass fiber reinforced polymer before hygrothermal loading. At 20% and 50% loading conditions the maximum flexural strength of 46.7 MPa for plain glass fiber reinforced polymer and 147.52 MPa for 2% Nanoclay/glass fiber reinforced polymer was observed before hygrothermal conditions. Maximum degradation in tensile strength (384.78 MPa at 50% loading) for 2% Nanoclay/glass fiber reinforced polymer after hygrothermal loading was observed in NaCl environment. Lower tensile strength observed for 1% of Nanoclay addition in pure epoxy as compared to the 0% and 2% mixing. There is decrease in tensile strength for specimen with 2% of Nanoclay in pure epoxy as compared to the 0% and 1% mixing. Tensile strength changed by moisture as well as mechanical loading of the glass composites. There is lesser degradation and significant increase in tensile strength of glass fiber reinforced polymer nanocomposite was observed when it exposed for lesser time period while tensile strength significantly reduced when specimen was exposed for longer time (3000 hr). After degradation in four different environments (four tanks) for 30 days intervals, SEM analysis of glass fiber reinforced polymer nanocomposite at pre-stretching of 20% and 50% loading was observed. At 20% loading there is lesser damage of glass fiber reinforced polymer nanocomposite with the formation of small irregular lumps were observed while at 50% loading there is significant damage of glass fiber reinforced polymer nanocomposite with the formation of voids of epoxy was clearly observed during SEM analysis.

Context-dependent parasite infection affects trophic niche in populations of sympatric stickleback species.

How parasites alter host feeding ecology remains elusive in natural populations. A powerful approach to investigate the link between infection and feeding ecology is quantifying unique and shared responses to parasite infection in related host species within a common environment. Here, 9 pairs of sympatric populations of the three-spined and nine-spined stickleback fishes were sampled across a range of freshwater and brackish habitats to investigate how parasites alter host feeding ecology: (i) biotic and abiotic determinants of parasite community composition, and (ii) to what extent parasite infection correlates with trophic niche specialization of the 2 species, using stable isotope analyses (δ15N and δ13C). It was determined that parasite community composition and host parasite load varied among sites and species and were correlated with dissolved oxygen. It was also observed that the digenean Cyathocotyle sp.'s abundance, a common directly infecting parasite with a complex life cycle, correlated with host δ13C in a fish species-specific manner. In 6 sites, correlations were found between parasite abundance and their hosts' feeding ecology. These effects were location-specific and occasionally host species or host size-specific. Overall, the results suggest a relationship between parasite infection and host trophic niche which may be an important and largely overlooked ecological factor. The population specificity and variation in parasite communities also suggest this effect is multifarious and context-dependent.

Frequency division and optimizing capacity technology for hybrid energy storage system considering load smoothing

There is a problem that how to optimize the allocation of hybrid energy storage system (HESS) economically on user-side. To solve this, a planning and scheduling method of HESS considering load smoothing is proposed. Firstly, an optimization model of energy storage system (ESS) considering energy storage life and peak-shaving rate is established, which is used to determine the rated power, rated capacity of ESS, and the charge and discharge power at each moment of the day. Then, this paper constructs a HESS consisting of lead-carbon battery (Pb-C) and supercapacitor. Variational mode decomposition (VMD) algorithm was used to extract peak load. The peak load is smoothed by super capacitor, and the composite load after peak load optimization is smoothed by Pb-C. Finally, solving the optimization model of HESS by mixed integer linear programming (MILP). And the results of the calculation examples show that the optimization method of HESS proposed in this paper not only reduces peak load effectively, but also improves benefits of HESS under the background of time-of-use electricity price.

Online Parameter Identification of a Simplified Composite Load Model by Voltage Sag Events

Online Parameter Identification of a Simplified Composite Load Model by Voltage Sag Events

Role of Oral Microbiota Biofilms in Recurrent Tonsillitis and Sleep‐Disordered Breathing in Children

Aims & HypothesisThe palatine tonsils are aggregates of lymphoid tissue in the lateral oropharynx. In children, tonsillar enlargement can lead to upper airway obstruction and sleep‐disordered breathing (SDB). The reason for tonsillar enlargement in some children, and not others is unknown. We have investigated the role of the tonsillar microbiota in tonsillar enlargement. The role of bacterial biofilms in RT and SDB was investigated through comparisons of tonsil histopathology, mixed‐species biofilm's microbiota composition and biofilm phenotypes. We hypothesized that the SDB tonsillar phenotype has distinct biofilm forming bacterial communities driving tonsillar hyperplasia compared to recurrent tonsillitis.MethodsTonsils were acquired via tonsillectomy from children with RT or SDB. Tonsils were stained to assess florid reactive lymphoid hyperplasia (FRLH). In situ microbiota characterization was assessed by 16S rRNA gene sequencing and overall bacterial biomass was assessed by 16S qPCR. Tonsillar bacteria were extracted and grown in BHI media for in vitro assays. Oral microbiota biofilms were characterized using the Calgary Biofilm Device and “O’Toole” assay. Biofilm biomass was assessed by spectrophotometry using crystal violet staining. Bacterial adhesion/invasion assays were performed by infecting pharyngeal carcinoma cell lines Det‐562 with tonsil microbiota from RT and SDB groups. Immune profile of Det‐562 cells infected with RT and SDB microbiota (t=3 hours) was assessed by cytokine multiplex analysis.ResultsHistopathological analysis showed higher FRLH of the enlarged lymph node in the SDB group compared to RT group. Microbiota analysis has shown that the tonsil's microbiota composition and bacterial biomass did not significantly differ between tonsils that were taken out due to SDB and those taken out for recurrent tonsillitis. Calgary Biofilm Device biofilm assays indicated that the SDB multi‐species biofilms have higher biomass compared to RT biofilms. Microbiota from SDB group were more adhesive/invasive to Det‐562 cells compared to RT bacteria after 3 hours incubation. Cytokine profiling showed increased expression of granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), pro‐inflammatory cytokines IL‐1β, IL‐2, IL‐12 and interferon gamma (IFNγ) in Det‐562 cells exposed to SDB microbiota compared to RT.ConclusionsOur results indicate that SDB and RT tonsils have distinct histopathological signatures. In situ tonsillar microbiota composition and bacterial load did not differ between SDB and RT groups. In vitro assays showed that SDB tonsils exhibit increases in both multi‐species biofilm mass and bacterial adhesion/invasion to epithelial surfaces. These results also suggest that SDB bacterial biofilms lead to greater inflammation of the tonsils, confirmed by the elevated levels of FRLH and increased expression of pro‐inflammatory mediators. This study sheds light on the role pathobionts released from dysbiotic oral microbiota biofilms in the development of tonsillitis.

Comparison of optimized steel frame structures

Abstract Frame structures are defined as structures built of straight, less often curved bars, which are dimensioned to carry a planar or spatial load. These frames are generally considered statically indeterminate structures so that several methods can be used to determine their loads, but all of them require some simplification. This paper is not concerned with investigating these theories for determining the stresses but with the optimum design of a frame structure for a given geometry. Several different loads have been considered, where the value of the wind load in the horizontal direction has been considered. The optimization problem is mathematically formulated so that both compressive forces and bending moments acting on the horizontal beam and the vertical column, and their composite loads, are below the limit set by the material properties. The column connections were assumed to be fully rigid, and welded I-section were considered for both columns. For local bending conditions, the Eurocode 3 specification was applied. Several steel grades were tested during the investigations, and fire loading was considered an additional load. In this case, a higher safety factor was assumed to make the times to collapse comparable.

Greatly Enhanced Electromagnetic Interference Shielding Effectiveness and Mechanical Properties of Polyaniline-Grafted Ti3C2Tx MXene–PVDF Composites

Nowadays, evolutions in wireless telecommunication industries, such as the emergence of complex 5G technology, occur together with massive development in portable electronics and wireless systems. This positive progress has come at the expense of significant electromagnetic interference (EMI) pollution, which requires the development of highly efficient shielding materials with low EM reflection. The manipulation of MXene surface functional groups and, subsequently, incorporation into engineered polymer matrices provide mechanisms to improve the electromechanical performance of conductive polymer composites (CPCs) and create a safe EM environment. Herein, Ti3C2Tx MXene nanoflakes were first synthesized and then, taking advantage of their abundant surface functional groups, polyaniline (PA) nanofibers were grafted onto the MXene surface via oxidant-free oxidative polymerization at two different MXene to monomer ratios. The electrical conductivity, EMI shielding effectiveness (SE), and mechanical properties of poly (vinylidene fluoride) (PVDF)-based CPCs at different nanomaterial loadings were then thoroughly investigated. A very low percolation threshold of 1.8 vol % and outstanding electrical conductivities of 0.23, 0.195, and 0.17 S/cm were obtained at 6.9 vol % loading for PVDF-MXene, PVDF-MX2AN1, and PVDF-MX1AN1, respectively. Compared to the pristine MXene composite, surface modification significantly enhanced the EMI SE of the PVDF-MX2AN1 and PVDF-MX1AN1 composites by 19.6 and 32.7%, respectively. The remarkable EMI SE enhancement of the modified nanoflakes was attributed to (i) the intercalation of PA nanofibers between MXene layers, resulting in better nanoflake exfoliation, (ii) a large amount of dipole and interfacial polarization dissipation by constructing capacitor-like structures between nanoflakes and polymer chains, and (iii) augmented EMI attenuation via conducting PA nanofibers. The surface modification of the MXene nanoflakes also enhanced the interfacial interactions between PVDF chains and nanoflakes, which resulted in an improved Young's modulus of the PVDF matrix by about 67 and 46% at 6.9 vol % loading for PVDF-MX2AN1 and PVDF-MX1AN1 composites, respectively.

In Situ FBG Monitoring of a Henequen-Epoxy Biocomposite: From Manufacturing to Performance

This work reports the in situ instrumentation from manufacturing to loading of a henequen fiber woven-bioepoxy composite. Continuous monitoring was performed by means of fiber Bragg gratings (FBG) with the aim of tracking the curing behavior of the biolaminate by vacuum-assisted resin infusion (VARI). The instrumented composite was later tested mechanically under bending. Among the results obtained, micro-deformations were detected as a consequence of curing residual stresses, and when tested, the FBG data had similarity with the strain calculated according to the ASTM D7264/D7264M standard.

A Competitive Study of the Static and Fatigue Performance of Flax, Glass, and Flax/Glass Hybrid Composites on the Structural Example of a Light Railway Axle Tie

The most common studies in the literature are those analyzing fatigue life under cyclic loading for flax fiber-reinforced composites. A novel type of staple fiber yarn made from flax tow with almost unidirectional fiber orientation and a quasi-unidirectional fabric was developed for composite applications. Additionally, a hybrid material made of flax and glass was produced for a demonstrator component (an axle tie of a narrow-gauge railway). For such an application, the investigation of fatigue strength is of particular importance. Therefore, the fatigue behavior of flax, glass, and hybrid flax/glass composites was investigated in the high cycle fatigue range. A total of 106 load cycles were carried out. From about 7³ to 8³ loading cycles, the flax laminate was found to have higher fatigue strength than the glass fiber-reinforced composite. The hybrid materials tend to show a higher fatigue strength than the glass type from approximately 2 × 105 load cycles. Results based on a finite element method also demonstrate better fatigue properties at an increased number of load cycles for flax-based composites than the glass fiber-reinforced component. The flax/glass component’s fatigue strength ranged between the flax values and the glass fiber-reinforced composites. Overall, the hybrid material shows significantly better static bending and impact characteristics than flax and considerably better fatigue properties than the glass fiber-reinforced composite making the hybrid material attractive for an application in an axle tie.

A general strategy for heterogenizing olefin polymerization catalysts and the synthesis of polyolefins and composites

The heterogenization of homogeneous metal complexes on solid supports presents an efficient strategy for bridging homogeneous catalysts with industrially-preferred heterogeneous catalysts; however, a series of drawbacks restrict their implementation in olefin polymerization, particularly for copolymerization with polar comonomers. In this contribution, we report an ionic anchoring strategy that is highly versatile, generally applicable to different systems, and enables strong catalyst-support interactions while tolerating various polar functional groups. In addition to greatly enhanced polymerization properties, the supported catalysts achieved higher comonomer incorporation than their unsupported counterparts. This strategy enabled efficient polymerization at high temperatures at large scale and great control over product morphology, and the facile synthesis of polyolefin composites. More importantly, the dispersion of different fillers in the polyolefin matrix produced great material properties even at low composite loadings. It is expected that this strategy will find applications in different catalytic systems and the synthesis of advanced engineering materials.

Control of Distributed Photovoltaic Inverters for Frequency Support and System Recovery

Replacing conventional synchronous generator-based power plants with inverter-based renewable energy resources results in a reduction of the inertia in power systems. To sustain the security and reliability of these low-inertia power systems, frequency support is increasingly required in new standards for grid-connected renewable energy resources, especially distributed photovoltaic (DPV) systems. This article proposes a frequency droop-based control in DPV inverters to improve frequency response in power grids with high penetration of renewable energy resources. A predefined power reserve is kept in the DPV inverter, using flexible power point tracking. The proposed algorithm uses this available power reserve to support the grid frequency. Furthermore, a recovery process is proposed to continue injecting the maximum power after the disturbance, until frequency steady-state conditions are met. The positive inertia using the proposed recovery mode, leads to recovery of the frequency in a shorter period. A composite load model of a distribution feeder, including DPV, is developed to assess the effectiveness of the proposed frequency support algorithm in power systems with high penetration of DPV inverters. The dynamic performance of the proposed frequency support algorithm with over frequency and under frequency events is also evaluated experimentally.

Shear strengthening of RC deep beams using glass chopped strand mat (GCSM) composite

This paper presents an easy and effective technique for shear strengthening of reinforced concrete (RC) deep beams using the glass chopped strand mat (GCSM) composite. Based on the previous research, the RC deep beams may fail because of the de-bonding of the GCSM composite from the concrete surface. To prevent this de-bonding failure and to use the GCSM composite to its full potential, two different anchoring systems were investigated and proposed. A total of twenty RC deep beams were tested to failure subjected to one-point and two-point loading systems. The effects of several important parameters, such as GCSM composite layer, strengthening configuration, anchoring system, loading system, and concrete strength, on the ultimate loading capacity and failure modes of the RC deep beams were investigated. The experimental results revealed that the GCSM composite enhanced the ductility and the ultimate loading capacity of the RC deep beams. To confirm the experimental findings, finite element analysis (FEA) of the RC deep beams strengthened with the GCSM composite was also carried out employing the FEA software VecTor2. The FEA results were found to be in good agreement with experimental results for the RC deep beams with and without strengthening.