Chemical Anchors Research Articles

Behaviour of post-installed adhesive anchors in natural stone

This work is based on the results of an experimental research related to chemical anchors in natural stone. The specific goal is to achieve the minimum embedment depth for chemical anchoring of post-installed threaded rods in basalt, sandstone and limestone support, by using epoxy resin. The reliability of theoretical formulations in the literature valid for concrete is evaluated. The applicability of some numerical models for the prediction of the bearing capacity of the anchor is then investigated, whereas the theoretical formulations are not feasible.

Prediction of the pull-out strength of chemical anchors in natural stone

The applicability of some numerical models for the prediction of the failure mechanism and of the bearing capacity of post-installed threaded rods chemically anchored in basalt, sandstone and limestone is investigated, as well as the reliability of theoretical formulations conceived for concrete. The numerical predictions, performed by means of engineering structural analysis software and advanced numerical codes, are compared with the results of an experimental research related to chemical anchors in natural stone. The minimum embedment depth for such fastening system is identified.

Experimental Study on Tension Performance of Anchor Group

The torque-controlled expansion anchors, undercut anchors,bonded anchors and special inverted conical chemical anchors subjected to tension load, which including single anchor, two anchors, four anchors and eight anchors are tested. Failure mode and tension performance of anchor group are investigated, and test value and calculative value of ultimate load are compared. Experimental results show that some anchor group occur the concrete cone failure under tension load, and others occur steel failure under tension load. Test value and calculative value of ultimate load are compared, and the result meets well.

Validation of Aspergillus fumigatus glucosamine-6-phosphate N-acetyltransferase as a potential antifungal target

BackgroundAspergillus fumigatus presents a spectrum of clinical, diagnostic, and therapeutic challenges. A new pipeline of novel validated antifungal targets is needed to address limitations in existing agents. The fungal cell wall is essential for survival, with chitin (β(1-4) linked N-acetyl-D-glucosamine [GlcNAc]) forming an integral layer. Enzymes involved in the biosynthesis of its sugar nucleotide precursor, UDP-GlcNAc, are potential antifungal targets. One such enzyme is glucosamine-6-phosphate N-acetyltransferase (GNA1) that N-acetylates glucosamine-6-phosphate to N-acetyl-glucosamine-6-phosphate as an intermediary step. Here we genetically validate A fumigatus GNA1 as an antifungal target and assess whether small-molecule ligands bind to the protein. MethodsWe constructed a gene deletion mutant, based on homologous recombination, by replacing the afugna1 coding sequence with the pyrG selectable marker. Purified GNA1 from A fumigatus (AfGNA1) was chemically biotinylated, and a fragment screen using bio-layer interferometry (Octet Red, Pall Forte Bio, Menlo Park, CA, USA) done to assess the binding of fragments to the target protein. X-ray crystallography was used to verify preliminary hits and determine the binding mode. FindingsThe mutant strain of A fumigatus was unable to grow in vitro without the addition of exogenous GlcNAc. Screening the Dundee Drug Discovery Unit (DDU) fragment library gave a preliminary hit rate of 5·7 % (37/652 with a response rate >0·02 nm). A subset of seven fragments showed stoichiometric binding with equilibrium dissociation constants in the micromolar range. Structural analysis of AfGNA1 in complex with fragment (A) showed that the fragment binds in a groove behind the sugar substrate. InterpretationFragment-based drug discovery provides a complementary and contrasting approach to traditional high-throughput methods by elaborating weakly binding small molecules. Iterative cycles of medicinal chemistry and structural biology are required to optimise this chemical anchor by extending into the active site to generate highly potent drug-like lead molecules. This work suggests that GNA1 is essential for cell viability in A fumigatus and could be a potential novel antifungal target. FundingUK Medical Research Council.

가압식 브레이싱 보강에 의한 지중박스구조물의 내진성능향상 방법

This paper presents a new strengthening method of underground box structures against seismic loads for anti-seismic capacity improvement. A threaded steel member with pressure devices(so called 'I-bracing pressure system') is used to improve seismic capacity of the RC box structure. The I-bracing pressure system is fixed the corner of opening after chemical anchor was installed by drilling hole on the box structure. The structural performance was evaluated analytically. Two bracing types of strengthening methods were used; conventional bracing method and improved I-bracing pressure system. For the performance evaluation, seismic analyses were performed on moment and shear resisting structures with and without I-bracing pressure system. Numerical results confirmed that the proposed I-bracing pressure system can enhance the seismic capacity of the underground RC box structures.

Bearing capacity of steel-caged RC columns under combined bending and axial loads: Estimation based on Artificial Neural Networks

The use of steel caging for strengthening a reinforced concrete (RC) column is an economical and common solution. However, the design of the optimum steel cage is a complex task. Artificial Neural Networks (ANN) has shown to be a useful device for engineers to solve tasks related to the modelling and prediction of the behavior of complex engineering problems. This mathematical tool can be trained from a series of inputs in order to obtain a desired output, without the need to reproduce the phenomenon under study. Based on a total of 950 results obtained with a validated finite element (FE) model, this paper presents the use of ANN to predict the axial–bending moment (N–M) interaction diagram of steel-caged RC columns under combined bending and axial loads. The data is arranged in a format of six input parameters taking into account several aspects such as the geometry of the RC column, the size of the steel cage, the concrete compressive strength, the steel yield stress and the axial load level. The output is the bending moment reached by the steel-caged RC column. Since the way of solving the beam–column joint plays a key role in the behavior of the strengthened column, four ANNs are developed in this paper, related to the beam–column connection type: using capitals, using capitals with chemical anchors, using capitals and steel bars, and without any element. The ANNs developed show excellent results, which are far better to those given by three design analytical proposals. Based on the ANNs performed, a simple mathematical expression is developed, which can be used by practitioners when facing the design of a steel-caged RC column subjected to axial loads and bending moments.

Tensile behavior of post-installed chemical anchors embedded to low strength concrete

In the scope of this paper, tensile capacities of post-installed chemical anchors embedded to 5.9 and 10.9MPa concrete blocks are investigated. Pull-out tests are applied to 80 ductile steel bars (S420a). For the anchor diameters, 12, 16 and 20mm are chosen. On the other hand, 10, 15 and 20times the bar diameter are selected as free-edge distance and embedment depth for monotonic tensile loading tests. The results indicate that installation of anchors into low-strength concrete with sufficient embedment depth and free-edge distance is not unsafe as previously expected. To obtain ductile failure in low strength concrete, free-edge distance and embedment depth of minimum 15times the anchor diameter should be required. Furthermore, a comparison of test results with ACI 318 capacities is done and it is observed that ACI 318 has quite an over-conservative approach for the tensile capacity of post-installed anchors when low-strength concrete is considered.

Synthesis of Clickable Water‐Soluble Poly(amidoamine) Fullerodendrimers and Their Use for Surface Functionalization of Azido‐Coated Polymer Nanoparticles

AbstractIn this study, the synthesis of water‐soluble fullerene derivatives bearing on one side a poly(amidoamine) (PAMAM) dendron with peripheral carboxylic groups and an alkyne moiety on the other side is presented. Fullerodendrimers with tert‐butyl ester groups at the periphery were first prepared by treating C60 with unsymmetrical malonates through the use of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU)/I2 or DBU/CBr4 conditions. The latter led to an unexpected addition of dibromocarbene on C60. The tert‐butyl esters were then cleaved using formic acid and gave the corresponding carboxyfullerene derivatives. The second generation with eight carboxylic groups at the periphery was easily dissolved in water, whereas the first generation with its four carboxylic groups can only be solubilized in a basic medium. These compounds self‐assemble into micelle‐like aggregates probably composed of a cluster of C60 surrounded by a PAMAM shell. The alkyne moiety was then used as a chemical anchor to immobilize in water fullerodendrimers on the surface of azido‐coated polymer nanoparticles by means of the copper(I)‐catalyzed azide and alkyne cycloaddition reaction. At room temperature, this reaction is competing with azido cycloaddition onto the fullerene core. Given the high density of azide anchoring groups on the nanoparticle surface and the size of the fullerodendrimers, unreacted azides are still active and are available for subsequent functional arrangements. This strategy paves the way for the design of functional fullerene‐rich nanomaterials that could be of interest in the field of materials science.

Unraveling the adsorption mechanism of aromatic and aliphatic diols on the TiO2 surface: a density functional theory analysis

Understanding the adsorption mechanism of organic molecules on inorganic semiconductors is of great importance for generating and control functions in organic-inorganic materials. Here we have comprehensively investigated, by means of the density functional theory, the adsorption structure and energetic stability of aliphatic and aromatic diols on TiO2 using ethylene glycol, 1,2-n-decanediol, and catechol. Our calculations clearly show that the non-dissociative bidentate adsorption is more stable than the dissociative one for the aliphatic diol, both at low and high coverage conditions, result far differently from many other chemical anchor cases for which the dissociative mechanism usually prevails. On the other hand, for catechol the dissociative bidentate is the most stable at low coverage conditions, whereas, surprisingly, increasing the coverage with catechol makes the non-dissociative mechanism the most stable one, revealing possible coexistence of a dissociative and non-dissociative anchoring at high coverage. This work unraveled a variety of adsorption fashions of the diol compounds in conjunction with the impact of the coverage effect, highly dependent on the nature of the lateral chain of the anchor group.

Shear strength of epoxy anchors embedded into low strength concrete

Chemical anchors are getting more frequently used to connect structural elements. The studies regarding the chemical anchors embedded in low strength concrete are very limited in the literature. However, the compressive strength of the concrete may be 10MPa or lower in many strengthening applications. Steel bars having 12, 16 and 20mm diameters have been selected as the anchor rod in this study. They have been embedded in to concrete blocks with 5.9 and 10.9MPa compressive strength. Solvent-free epoxy based three component chemical adhesive has been used for the connection between concrete and anchor bar. The depth of holes is 10, 15 and 20 times that of the anchor diameter. The anchors have been embedded such that they are sufficiently away from the free edge so as not to cause any concrete failure. The load–displacement cycles of all anchors have been obtained by reversed cyclic tests with incremental displacement. The obtained results indicate that increasing the anchor diameter have decreased the shear strength. Even though the anchor damage has been caused by steel failure, a decrease in shear capacity was observed with the lower strength concrete.

Natural Tissue Microenvironmental Conditions Modulate Adhesive Material Performance

We designed and optimized tissue-responsive adhesive materials by matching material and tissue properties. A two-component material based on dextran aldehyde and dendrimer amine provides a cohesive gel through aldehyde-amine cross-linking and an adhesive interface created by a dextran aldehyde-selective reaction with tissue amines. By altering aldehyde-amine chemistry, we examined how variations in tissue surfaces (serosal amine density in the duodenum, jejunum, and ileum) affect interactions with adhesive materials of varied compositions (aldehyde content). Interestingly, the same adhesive formulation reacts differentially with the three regions of the small intestine as a result of variation in the tissue amine density along the intestinal tract, affecting the tissue-material interfacial morphology, adhesion strength, and adhesive mechanical properties. Whereas tissues provide chemical anchors for interaction with materials, we were able to tune the adhesion strength for each section of the small intestine tissue by altering the adhesive formulation using a two-component material with flexible variables aimed at controlling the aldehyde/amine ratio. This tissue-specific approach should be applied to the broad spectrum of biomaterials, taking into account specific microenvironmental conditions in material design.

Influence of Column Construction Type on the Bearing Capacity of Bonded Anchors

The anchorage formed by the post-installed steel chemical anchors can be used for new buildings. Thanks to easy and fast installation can be used particularly for reconstructions. Chemical anchors are the most frequently used with concrete and reinforced concrete. On the trade of anchoring, the chemical anchor systems are represented by a number of variants of this anchorage type but, in fact, they always consist of a steel bolt (anchor) installed in a pre-drilled hole. The connection between a steel bolt and concrete or masonry (most frequently) is done by glue, i.e. usually by different types of epoxy.The research presented in this article is focused on a possible application of these anchor types, namely in the connection of a steel beam with a face plate to different types of columns.The analysis of a connection steel beam cantilever stressed by bending moment to the construction of the column with bonded anchors. The loading capacity of anchors connected (bonded) to steel HEB concreted column will be compared to loading capacity of anchors bonded to reinforced concrete column.Comparisons will be done on the basis of experimental tests and subsequently validated by numerical models. Compared resistance of the anchors is different for columns and the rigidity of joints.

Functionalization of carbon nanotubes with arenedyazonium salts in urea

ABSTRACTThe functionalization of single wall carbon nanotubes (SWCNT) with arenediazonium salts, formed in situ from anilines as dimethyl-5-aminoisophthalate, sulfanilamide and p-anisidine, using the environmentally solvent urea. The functionalized SWNTs were then characterized using spectroscopic and microscopic methods along with thermogravimetric analysis (TGA). According to enhance solubility in solvents after that introduce them into the industrial processes. The molecules added appear on the nanotubes like chemical anchors.

Bond Strength of Chemical Anchor in High-Strength Concrete

This paper summarizes the results of experimental and numerical research focused on determination of the behavior and bond strength limits of what are currently the most widespread industrial glues used for anchor bonding. The goal of this research is to find the limits of the effective use of such glue types in high performance concrete, and also to verify the most commonly used design methods for bonded anchors. The progress and configuration of the experiments are described. The goal of this research is to find the limits of effective use of these glue types in high performance concrete and also verification of mostly used design methods. The article is closely focused on bond strength experiments using high strength concrete up to class C50/60 or higher.

Chemical approaches to synthetic polymer surface biofunctionalization for targeted cell adhesion using small binding motifs

In the present review the principal strategies to chemically modify the surface of synthetic polymeric materials with small molecules for targeted cell adhesion are collated and critically discussed. The focus is purposely oriented on the chemistry involved in these modifications and neither the physical characterizations nor the activity evaluations resulting from these modifications are addressed in depth, although most reviewed examples demonstrate cell adhesion. Particularly, the introduction of a chemical anchor onto the polymeric substrate, the spacing via a linker between the polymer surface and the cell-binding motif, as well as the linkage generated on this cell-binding motif are discussed. Particular cases where variable substrate geometries or spatial patterning are achieved are additionally highlighted. © 2012 The Royal Society of Chemistry.

Rehabilitation of a high‐rise coupled shear wall system in a 56‐storey residential reinforced concrete building (Tehran Tower), based on nonlinear dynamic time‐history analyses

SUMMARYTehran Tower is a 56‐storey reinforced concrete tall building consisting of three wings with identical plan dimensions each approximately 48 m by 22 m. The three wings are at 120° from each other and have no expansions/seismic joints. This paper contains the consideration of the rehabilitation of the Tehran Tower based on the findings of an exhaustive investigation of the nonlinear performance evaluation efforts. It has tried to show the procedure followed, methodologies utilized and the results obtained for life‐safety (LS) and collapse‐prevention (CP) evaluations of the building. Moreover, the weak zones of the structure due to analysis results are introduced and appropriate retrofit technique for satisfaction related to LS and CP criteria is presented. In this project, to improve the local behaviour of coupling panels that are regularly located in spine walls, and definitely have been recognized as the most vulnerable structural elements, making use of steel plates that are connected to concrete members by chemical anchors has been used as the best rehabilitation method for this case. Therefore, in the final section, the professional practical method utilized to perform the aforementioned project is explained. Copyright © 2010 John Wiley & Sons, Ltd.

캡슐형 케미컬 롯트앵커의 부착강도에 관한 연구

최근 건축물의 보수 보강 및 리모델링시 구조부재를 부착시키거나 고정하는데 있어서 시공의 유연성 및 용이성으로 후설치 케미컬앵커의 사용량이 증가하고 있는 실정이다. 그동안 후설치 앵커중 기계적 확장앵커에 대한 내력평가는 지난 10년간 실험을 통한 연구가 지속되어 설계기준식 제정등 어느정도 정립단계에 있으나 부착식 케미컬앵커에 대한 해석 및 실험적 연구는 아직 미비한 실정이다. 따라서 현재 우리나라에서는 설계자와 시공자가 신뢰할 수 있는 명확한 설계기준이 없는 상태로서 외국의 설계기준에 의존하고 있는 실정이다. 본 연구에서는 앵커직경, 앵커간격, 묻힘깊이 및 연단거리를 변수로 한 부착식 케미컬 앵커의 인발실험을 통하여 무근콘크리트에 매입된 캡슐형 케미컬 롯트앵커의 부착강도에 미치는 영향을 규명하고 국내 설계기준식 제정을 위한 기초자료를 제공하는 것을 그 목적으로 한다. Recently the use of post-installed anchors has been increasing because this constructing method is flexible and easy to attach or fix structural members when we repair, reinforce, or remodel structures. And the design standard formula of expansion anchors, one method of post-installed anchors, has been settled to a certain level through continual experimental studies for the last about ten years. But analyses or experimental studies of chemical anchors, which are adhesive anchors, are yet insufficient. Accordingly, designers and builders of Korea depend on foreign design codes since there are no exact domestic chemical anchor design codes that they could credit. There are two objectives in this study. The first objective is to investigate the effects of the variations like anchor diameter, anchor interval, embedment depth and edge distance on adhesive strength of capsule chemical lot anchors embeded in plain concrete through drawing experiments of chemical anchors. The second objective is to supply basic data for enactment of domestic chemical anchor design codes.

Polymersome surface decoration by an EGFP fusion protein employing Cecropin A as peptide “anchor”

Polymer based nanocompartments have potential applications in synthetic biology, medicine (drug release) and industrial biotechnology (chiral nanoreactors, multistep syntheses, selective product recovery). A step towards the aforementioned goals is the polymer membrane functionalization through covalent bonding of chemical anchors or insertion of proteins/peptides, to obtain specific properties like recognition, catalytic activity and facilitated diffusion, mimicking the complexity of a biological membrane. The use of genetic engineering techniques widens the possible applications of peptides and proteins specifically designed for polymer membrane interactions. A fusion protein (CecEGFP) based on the antibacterial peptide Cecropin A and the EGFP (Enhanced Green Fluorescent Protein) was designed, expressed and biophysically characterized. CecEGFP interaction with the tri-block copolymer PIB-PEG-PIB (PIB=polyisobutylene, PEG=polyethylene glycol) based polymersome membrane was analyzed by circular dichroism as well as EGFP and Trp fluorescence measurements. Results proved that Cecropin A is usable as a "membrane surface anchor" for water soluble proteins, as it inserts into the polymer membrane. The aim and novelty of this study is within the design of fusion proteins specifically developed for polymer membrane interactions. The use of amphiphilic Cecropin A "anchoring" water soluble proteins to the polymersome surface, avoids chemical coupling between polymers and proteins.

Pullout Performance of Fully and Partially Bonded Retrofit Anchors in Low-Strength Concrete

Although steel reinforcing bars can be used as post-installed anchors to integrate new structural members to the existing structural system in the seismic retrofit of reinforced concrete structures, premature cone-type concrete failure can reduce the bars’ efficiency when they are anchored into low-strength concrete. This study investigates pullout behaviors of fully and partially bonded chemical anchors post-installed in low-strength concrete. The test parameters are the embedment length, the bonded length of the anchors, and the humidity and dust surface conditions of the anchor holes. The pullout behavior is examined through the load-displacement curves, modes of failure, and anchorage strengths of specimens. The results show that the pullout performance of partially bonded, post-installed chemical anchors embedded in low-strength concrete is significantly better than conventional fully bonded post-installed chemical anchors, which suggests that partially bonded anchoring of deformed bars could be useful for anchorages in seismic retrofit applications. A model is proposed for predicting the pullout strength of anchors that fail due to a combination of concrete cone and bond failures. A good correlation is found between the model predictions and test results from this study compared with previously-published experimental findings.

Chemical Anchoring of Ag Nanoparticles to Si Surfaces and Its Application in Lithium Ion Batteries

Chemical Anchoring of Ag Nanoparticles to Si Surfaces and Its Application in Lithium Ion Batteries