Chemical Anchors Research Articles

Effect of inclination angle on the pull-out strength of bonded anchors installed in low-strength concrete

Bonded anchors are commonly used in the strengthening of reinforced concrete structures to ensure effective bonding between the existing and new concrete. In chemical-anchor applications, the anchor direction is typically perpendicular to the concrete surface. Most approaches adopted to design chemical anchors assume that the anchor direction is the same as the direction normal to the concrete surface. However, owing to certain requirements or application errors, the anchor direction may differ from the direction normal to the concrete surface. In this study, the effect of the inclination angle on the anchor strength was experimentally investigated. In addition to the inclination angle, the anchor embedment depth and concrete strength were also considered. As the concrete strength is generally lower than the design strength of reinforced concrete buildings that need to be strengthened, low-strength concrete was considered in our analysis. During our analysis, pull-out tests were conducted on 30 samples for five different angles (0°, 10°, 20°, 30°, and 40°), three embedment depths (64, 96, and 128 mm), and two concrete grades. The results obtained from the experiments were analyzed and statistically evaluated. The analysis revealed that an inclination angle of up to 10° did not have a significant effect on the pull-out strength, and the decrease in strength for angles up to 30° could be compensated by an increase in the embedment depth. Moreover, some experiments showed that increasing the inclination angle can positively contribute to the energy absorption capacity of the joint.

Distinct element modeling of the in‐plane response of a steel‐framed retrofit solution for URM structures

AbstractThis paper presents the results of a numerical study aimed at assessing the effectiveness of an innovative steel modular retrofit system on improving the in‐plane lateral capacity of unreinforced masonry (URM) load‐bearing structures. The investigated retrofit solution consists of modular steel frames fastened to the external surface of masonry piers through chemical anchors. Distinct element models are built and calibrated against experimental data coming from a series of in‐plane quasi‐static tests performed on piers in both bare and retrofitted conditions. Two different masonry typologies are considered herein: one made up with solid clay bricks and lime mortar, assembled in a header bond pattern, and the other with typical Italian hollow clay units and cement‐lime mortar, arranged in a Flemish bond pattern. A simplified microscale approach, combined with a mesh‐refinement strategy, is adopted to decrease computational demand without losing numerical accuracy. All in‐plane failure mechanisms, such as mortar and unit tensile failures, as well as masonry crushing for high compressive stresses, are included in the developed numerical models. Moreover, a methodology to explicitly account for the contribution of the investigated retrofit in the distinct element method (DEM) framework is presented and discussed. The proposed modeling strategy yielded a good prediction in terms of lateral stiffness, lateral strength, hysteretic response, and crack pattern for unreinforced and strengthened specimens. A novel set of metrics is proposed to quantitatively assess the retrofit performance benefits.

Construction of Biomass Tea Polyphenol-Functionalized Halloysite Nanotubes Enabling Green and Sustained-Release Antioxidants for Highly Antiaging Elastomers

The strategy of using sustainable biomass resources instead of traditional petrochemical products has been established as an environmentally friendly way to achieve the “green rubber” industry. Meanwhile, rubber antioxidants possessing high efficiency, long-lasting protection, migration resistance, and green multifunctional properties have attracted intensive investigation for rubber protection. Herein, a naturally extracted substance of tea polyphenol (TP)-functionalized halloysite nanotubes (HNTs), which generates the slow release of free-radical capturing activity and excellent interfacial interaction in the natural rubber matrix, is fabricated by vacuum-pumping and surface-decorating methods (denoted as HNTs-s-TP). Interestingly, the nontoxic and natural antioxidant HNTs-s-TP exhibited remarkable thermo-oxidative aging resistance and stability in a natural rubber (NR) matrix compared to that of TP directly pumped into the tubes due to the further modification of the chemical anchor TP on the outer surface of HNTs. In addition, we have systematically investigated the mechanism for highly efficient and sustainable antioxidation in the rubber matrix via the natural antioxidant HNTs-s-TP derived from the constructed galloyl structure. We envision that this new natural antioxidant fabrication technology will provide significant insights into the innovation for the construction of green and eco-friendly functionalized rubber additives.

Effect of synthetic zeolite on tobermorite synthesis

Chemical anchors are widely used in additional installations of construction irons, repair and reinforcement work. Due to the increasing diversity of materials and the improved awareness of waste products, it has become possible to produce different kinds of concrete, with various properties. In this study, class B420C ribbed bars with 16 mm diameter, were installed in four different concretes by using four different chemical adhesives, and a tensile force was applied. The stiffness, displacement ductility ratio, energy-dissipation capability and tensile force values were determined and the failure modes were interpreted from the load-displacement curves, obtained as a result of the experiments. It was found that the tensile force and energy-dissipation capacity, had increased as a result of installing anchor and applying a tensile force to the concrete, that was obtained by adding admixture materials, to the reference concrete. In the analytical part of the study, the formulation provided in ACI 318 was used, capacity and design strengths were identified, and their safety levels were determined in comparison with the test results.

Expediting Stepwise Sulfur Conversion via Spontaneous Built‐In Electric Field and Binary Sulfiphilic Effect of Conductive NbB2‐MXene Heterostructure in Lithium–Sulfur Batteries

AbstractFabricating metal boride heterostructures and deciphering their interface interaction mechanism on accelerating polysulfide conversion at atomic levels are meaningful yet challenging in lithium–sulfur batteries (LSBs). Herein, novel highly‐conductive and binary sulfiphilic NbB2‐MXene heterostructures are elaborately designed with spontaneous built‐in electric field (BIEF) via a simple one‐step borothermal reduction strategy. Experimental and theoretical results reveal that Nb and B atoms can chemically bond with polysulfides, thereby enriching chemical anchor and catalytic active sites. Meanwhile, the spontaneous BIEF induces interfacial charge redistribution to make more electrons transferred to surface NbB2 sites, thereby weakening its strong adsorption property yet accelerating polysulfide transfer and electron diffusion on hetero‐interface, so providing moderate polysulfide adsorb‐ability yet decreasing sulfur‐species conversion energy barriers, further boosting the intrinsically catalytic activity of NbB2‐MXene for accelerated bidirectional sulfur conversion. Thus, S/NbB2‐MXene cathode presents high initial capacity of 1310.1 mAh g−1 at 0.1 C, stable long‐term lifespan with 500 cycles (0.076% capacity decay per cycle) at 1 C, and large areal capacity of 6.5 mAh cm−2 (sulfur loading: 7.0 mg cm−2 in lean electrolyte of 5 µL mgs−1) at 0.1 C. This work clearly unveils the mechanism of interfacial BIEF and binary sulfiphilic effect on accelerating stepwise sulfur conversion at atomic levels.

Numerical Investigation on the Mechanical Properties of Vault Void Lining and Steel Plate Strengthening.

To study the mechanism of vault lining under different void heights and verify the strengthening effect of the attached steel plate, a CDP (concrete-damaged plasticity) model and the XFEM (extended finite element method) were used to construct the local numerical model of the vault void, and an experiment was carried out for verification. The strengthened structure of the steel plate was assembled with a combination of a two-component epoxy adhesive and chemical anchor bolts. Five lining models with various void thicknesses, together with their strengthened models, were evaluated. The results of the established numerical model were compared with the experimental results in terms of failure mode, vertical displacement, and load-deformation results. The results of the two numerical models were in good agreement with the experimental results, revealing the failure mechanism of the vault lining. The rigidity of the specimen after steel plate strengthening was significantly improved. When the void height was one-fourth of the secondary lining thickness, the lining cracks were reduced from 14 to 4, and the distribution width of the cracks was also reduced from 1.047 to 0.091 m after steel plate strengthening. The level of damage caused by cracking was significantly reduced, which proves the effectiveness of the surface-sticking method for steel plate strengthening.

Experimental investigations the effects of dusty, humidity and temperature conditions on chemical anchors

Chemical anchor applications are frequently used to add new structural elements to existing structures. Chemical anchors can be applied quickly and easily, if anchors apply according to a detailed installation and cleaning procedure depending on environmental conditions and workmanship. In this work, the relationship between the axial tensile capacity of chemical anchors and the effect of dust, humidity, and temperature were examined as adverse conditions. The effect of using different conditions, anchorage diameters and embedment depth on the tensile strength of the anchors was evaluated. In the experimental study, anchors diameter 12, 16 and 20 mm were selected to be used as anchors. The depth of embedding was determined to be 5, 10, 15 and 20 times the diameter of used anchors. The initial stiffness, displacement ductility ratio, energy absorption capacity, failure modes, and safety levels according to ACI 318 were obtained by using the load-displacement curves. According to the parameters considered in the experimental program, the most unfavorable situation was obtained in anchors embedded in a wet environment. In addition, it was observed that the diameter of the drilled holes causes a decrease in the axial tensile capacity by increasing the exposure time of the anchors to water and temperature.

Resonant transport in a highly conducting single molecular junction via metal-metal covalent bond.

Achieving highly transmitting molecular junctions through resonant transport at low bias is key to the next-generation low-power molecular devices. Although resonant transport in molecular junctions was observed by connecting a molecule between the metal electrodes via chemical anchors by applying a high source-drain bias (>1 V), the conductance was limited to <0.1G0, G0 being the quantum of conductance. Herein, we report electronic transport measurements by directly connecting a ferrocene molecule between Au electrodes under ambient conditions in a mechanically controllable break junction setup (MCBJ), revealing a conductance peak at ∼0.2G0 in the conductance histogram. A similar experiment was repeated for ferrocene terminated with amine (-NH2) and cyano (-CN) anchors, where conductance histograms exhibit an extended low conductance feature, including the sharp high conductance peak, similar to pristine ferrocene. The statistical analysis of the data and density functional theory-based transport calculation suggest a possible molecular conformation with a strong hybridization between the Au electrodes, and that the Fe atom of ferrocene is responsible for a near-perfect transmission in the vicinity of the Fermi energy, leading to the resonant transport at a small applied bias (<0.5 V). Moreover, calculations including van der Waals/dispersion corrections reveal a covalent-like organometallic bonding between Au and the central Fe atom of ferrocene, having bond energies of ∼660 meV. Overall, our study not only demonstrates the realization of an air-stable highly transmitting molecular junction, but also provides important insights about the nature of chemical bonding at the metal/organo-metallic interface.

Determination of the effects of the rebar-cement bond parameters variation in UHPFRC using Fa and ANN

The experimental study included the design and production of ultra-high-performance steel fiber-reinforced concrete (UHPFRC). The physical and mechanical properties of UHPFRC were investigated in a laboratory setting. To investigate the properties of UHPFR concrete, three types of concrete and over 70 samples were used. Following that, samples were created to test the anchors' load-bearing performance. Six concrete slabs with a total of 108 pre-installed anchor samples and six concrete slabs with 108 post-installed chemical anchor samples were created. The analysis of the test findings comprised all individual results as well as the definition of the relationship between the anchor's tensile load capacity and other parameters. To accurately determine the individual influence of the investigated factors as well as their combined impact, a factorial experiment, and artificial neural networks were used in addition to normal statistical numerical studies. It was determined that both approaches offer advantages. The results obtained show matches in certain parts. Due to the way data is processed in different ways, there are also significant differences between them.

Chemical Anchor Pullout Force Modeling with Variation of Anchor Embedment Length in Concrete and Concrete Strength

The embedment length influences the adhesion between the cast iron material and the concrete. The concrete's compression strength also contributes to an increase in bond strength. Therefore, this research aims to determine the maximum pullout force on each variation of the anchor and the optimal embedment length. A gauge is modeled as a rod-type with a diameter of 16 mm, and the embedment lengths used are 5D, 10D, and 15D, while the compressive strengths include fc’ 20, 30, 40, 50, and 60 MPa. Furthermore, a finite element-based application was utilized with the ANSYS Workbench student version. The result showed that the concrete with strengths of 20, 30, 40, 50, and 60 MPa has maximum pullout forces of 27.011, 53.536, 68.657, 68.970, and 84.407 kN, respectively at an embedment length of 15D. It was observed that the failure pattern obtained starts from the defect in the concrete cone and ends with the breakage of reinforcement or steel failure at each variation of concrete strength. A combination of two non-parametric techniques was used in this research, which includes Kruskal Wallis and U-Mann Whitney test. The first technique revealed that the chi-square value for strengths 20, 40, 50, and 60 MPa is 9.486, while that of 30 MPa is 9.881. The second test employed showed a significance value below 0.05. In conclusion, the embedment length affected the value of pullout force, and 15D was the optimum embedment length for each variation of concrete strength. The enhancement in tensile strength increases with the strength of the concrete.

Experimental Investigation on the Mechanical Properties of Vault Void Lining in Highway Tunnels and Steel Plate Strengthening

In the present study, large-scale specimens based on the tunnel prototype were prepared and static load tests were carried out to investigate the damage caused by lining voids. Based on the strengthening scheme of the tunnel, the strengthened specimens were prepared to explore the strengthening effect on the strengthening structure. The strengthening structure is made of a steel plate fixed with chemical anchor bolts and two-component epoxy adhesive. By analyzing the failure mode, structural deformation, and the relationship between load and strain, the damage caused by vault void with various void heights was analyzed and the obtained results were verified through the experiment. Moreover, the enhancement of the bearing capacity and stiffness of the structure strengthened by surface bonding steel was studied. The obtained results show that the damage caused by the lining void mainly occurs at the void boundary. The damage appears as multiple longitudinal cracks. The crack starts from the lower surface and develops radially. Using chemical anchor bolts and two-component epoxy adhesive to bond the steel plate on the lining surface, the damage can be reduced, and the bearing capacity of the structure can be improved effectively when the void height is a quarter of the second lining thickness, the number of cracks is reduced from 14 to 5 after steel plate strengthening, and the length of the longest crack is reduced from 13.2 cm to 8.3 cm, reduced by 37.12%. The steel plate strengthening also reduces the strain of the lower steel bar at the void boundary from 1130.58 με to 555.12 με, and the strain decreases by 50.89%. The experimental results show that the position where the void has the greatest impact on the lining is at the void boundary. Therefore, when steel plates are used to strengthen the void lining, the void boundary should be emphasized, which makes the strengthening more accurate and saves the cost of treatment.

Low-Temperature Calcination of Metal-Organic Frameworks(MOFs) to Derive the High Entropy Stabilized Oxide for High Performance Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) battery owing to high energy density and theoretical capacity is anticipated as a high-performance rechargeable power source for flexible electronic devices and electric vehicles. However, the rapid capacity fade, low Coulombic efficiency, and significant self-discharge capacity loss due to the polysulfides shuttling are the major constraints of its real-world applications. To conquer these challenges, despite the physical encapsulation of polysulfides, chemical interactions between shuttle effect-suppressive sulfur host materials and soluble lithium polysulfides have recently been emphasized. Herein, a novel approach to synthesize the high entropic stabilized oxide (HEO) at low temperature is developed from the self-sacrificing template of metal-organic frameworks (MOFs) to chemically anchor the lithium polysulfides. As-synthesized HEO850 at 850 ºC (transition temperature) exhibited a single-phase rocksalt crystalline structure with homogenous dispersion of Ni, Mg, Cu, Co, and Zn and reversible entropic phase stabilization in the certain temperature range (750-850 ºC). When employed as a chemical anchor to lithium polysulfides (LIPSs) and compared the electrochemical performance of Li-S cells with medium configurational entropic oxide (MEOs) (HEOs-one metal cation), low entropy oxide (LEOs) (HEOs-three metal cations), and routine sulfur ketjen black (S/KB) cells, it revealed a competitive reversible capacity, excellent cycling stability and a low capacity decay rate by immobilizing the LIPSs and facilitating the redox reaction in the cathode. The cells with HEO850/KB/S cathode delivered a higher initial specific discharge capacity of 1244.1 mAh g-1 than those of MEO850/S/KB (979.625 mAh g-1), LEO850/S/KB (908 mAh g-1), and S/KB (966 mAh g-1). After 800 cycles of continuous charging and discharging at 0.5 C, the capacity of 784.1 mAh g-1 with outstanding Coulombic efficiency of 99.66 % is still retained demonstrating excellent cycling stability with a negligible capacity fade rate of 0.04% per cycle. This outstanding performance could be attributed to the synergistic contribution and exposure of numerous active sites of randomly dispersed elements in the HEO850. This study not only highlights the extraordinary electrochemical performance of Li-S battery with efficient immobilization of LIPSs but also provide a novel strategy for the synthesis of HEOs at lower calcination temperature for various energy conversion and storage applications. After getting confidence with these prilimary results, Ti-based HEOs owing to both high ionic and electric conductivities will be investigated at coin and pouch cell level as future research direction.

Analysis of Composite Beam with Shear Connectors Using FEA Software (ANSYS)

Abstract: The Composite structures made of concrete slabs and rolled steel profiles are widely used components in bridges and High buildings. Composite effects are created by connecting concrete slabs and steel profiles with chemical anchors. In this paper, I analyze three types of shear connectors ( Headstud, T shape, Channel section ) with different grade of concrete M-20, M-30, M-40 based on design strength given by the code book IS: 11384-1985. Based on their performance under static load, find the best connector for a particular composite beam while maintaining the stress and amount of steel in the connector as a common aspect. Keywords: Composite beams, Ansys Software, Shear Connectors

A Multifunctional Fluorinated Polymer Enabling Efficient MAPbI3-Based Inverted Perovskite Solar Cells.

Exploring polymeric hole-transporting materials (HTMs) with passivation functions represents a simplified and effective approach to minimize the perovskite defect density. To date, most of reported polymeric HTMs were applied to fabricate n-i-p regular perovskite solar cells (PSCs). The polymers compatible for p-i-n inverted PSCs were very limited. Moreover, the passivation polymers were devoted to passivate the uncoordinated Pb2+. However, the MA+ cation defect has profound unwanted effect on device efficiency and long-term stability. In order to synchronously passivate the Pb2+ and MA+ defects in p-i-n inverted PSCs, a new nonfused polymer was intentionally explored via mild polymerization. The aromatic bridge instead of long alkyl chains enabled polymer BN-12 to achieve excellent thermal stability and good wettability of perovskite precursor. Furthermore, the incorporation of chemical anchor sites ("C═O" and "F") strongly controlled the crystallization of perovskite and restrained the MA+ ion migration. As a result, a significant fill factor (FF) of 82.9% and an enhanced power conversion efficiency (PCE) of 20.28% were achieved for MAPbI3-based devices with the dopant-free BN-12, exceeding those with the commercial HTM PTAA (FF = 81.7%, PCE = 19.51%). More importantly, the unencapsulated devices based on BN-12 realized outstanding long-term stability, maintaining approximately 95% of its initial efficiency after stored for 85 days. By contrast, the PTAA-based device showed rapid decrease which retained only 50% of its initial value after 45 days.

Grain Boundary Chemical Anchoring via Bidirectional Active Site Additive Enables Efficient and Stable Perovskite Solar Cells

AbstractThe nonradiative recombination induced by trap states at the surface and grain boundaries impedes the further increase of power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Consequently, it is highly desirable to minimize the trap‐assisted nonradiative recombination in perovskite films. Here, an effective additive engineering strategy is reported where N‐succinimidyl 6‐maleimidohexanoate (denoted as NSMH) with multiple active sites and hydrophobic alkyl chains were incorporated for fully eliminating undercoordinated Pb2+ traps in perovskite films. It is revealed that improved crystallinity and reduced defect density are achieved, which is ascribed to the strong coordination interaction between the carbonyl groups at both sides of NSMH molecules and Pb2+. As a result, the NSMH‐modified device exhibits a champion PCE of 22.40% with negligible hysteresis, which is significantly higher than 20.67% of the control device. The unencapsulated modified device exhibits no degradation while the control device degrades to 82% of its initial PCE after storing for 1536 h in a relative humidity of 10–20% at room temperature in the dark.

Thorn-Like Carbon Nanofibers Combined with Molybdenum Nitride Nanosheets as a Modified Separator Coating: An Efficient Chemical Anchor and Catalyst for Li–S Batteries

Thorn-Like Carbon Nanofibers Combined with Molybdenum Nitride Nanosheets as a Modified Separator Coating: An Efficient Chemical Anchor and Catalyst for Li–S Batteries

Strength Performance of the Connection between Brick and SPF Lumber

There are many ways to strengthen an unreinforced brick masonry wall. One of the strengthening methods applies timber, which is a lightweight and easy installation. The connection between the timber and the brick masonry wall plays an important role. In this study, the experimental and theoretical methods were investigated, and the pullout and shear strengths of the chemical anchor were employed as the connection between clay brick and SPF (spruce, pine, fir) lumber. Three bolt diameters (ø8, ø10, ø12 mm) were utilized in nine pullout tests and two types of eighteen shear tests. Four types of prediction models estimated the pullout strength of the chemical anchor. The European Yield Theory (EYT) expected the shear strength of the chemical anchor, involving six failure modes. The results of all experiments were discussed as failure mode, strength, and stiffness under monotonic load. Finally, the effective result of this study highlights A12 specimens using ø12 mm bolt and employing the epoxy resin in brick and lumber. The maximum pullout load of A12 specimens is 12.1 kN, and the yield shear load is 11.2 kN.

Development of novel urea-based ATM kinase inhibitors with subnanomolar cellular potency and high kinome selectivity

The ATM kinase is a key molecule regulating DNA damage response and can be targeted resulting in efficient radio- or chemosensitization. Due to the enormous size of this protein and the associated difficulties in obtaining high-quality crystal structures, we sought to develop an accurate in silico model to identify new targeting possibilities. We identified a urea group as the most beneficial chemical anchor point, which could undergo multiple interactions in the aspartate-rich hydrophobic region I of the atypical ATM kinase domain.Based on in silico data, we designed and synthesized a comprehensive set of novel urea-based inhibitors and characterized them in diverse biochemical assays. Using this strategy, we identified inhibitors with subnanomolar potency, which were further evaluated in cellular models, selectivity and early DMPK properties. Finally, the two lead compounds 34 and 39 exhibited subnanomolar cellular activity along with an excellent selectivity profile and favorable metabolic stability.

Shake table tests of concrete anchors for non-structural components including innovative and alternative anchorage detailing

In recent years, the growing need for reducing non-structural damage after earthquakes has stimulated a dedicated effort to develop innovative types of fasteners for anchoring non-structural components (NSCs) to reinforced concrete (RC) host-structures. To contribute to such need, and building on previous research, this paper presents the results of a series of uni-directional shake-table tests of simulated NSCs anchored to concrete via: (1) expansion, and (2) chemical anchors; post-installed into: (a) uncracked, and (b) cracked concrete. Considering different construction details, the experimental investigation focused on traditional anchorage systems, alternative solutions comprising mortar filling into the gap clearance, and a low-damage system relying on supplemental damping devices, capable of reducing the acceleration of the NSCs as well as the force of the anchorage during seismic shakings. The experimental tests provided significant evidence on the beneficial effects of a dissipative anchorage protecting both the non-structural component and the anchorage itself, even during strong earthquakes. Moreover, when construction details allow to close the fixture clearance with a mortar filling, this stiffer solution provide an additional reduction of NSCs seismic accelerations and forces. Therefore, suggestions for further improvements of the adopted low-damage solution are also proposed.

An Experimental Study on the Pull-out Strength of Post-installed Capsule and Insertable Chemical Anchors

An Experimental Study on the Pull-out Strength of Post-installed Capsule and Insertable Chemical Anchors