Resin injected bolted connections : a step towards achieving slip-resistant joints in FRP bridge engineering

This paper reports results from a series of static tests on resin injected bolted joints with pultruded Fibre Reinforced Polymer (FRP) material. The aim is to characterise a method of connection that could be fatigue and slip resistant. For comparison, tests are also carried out on standard bolted connections without resin and with 2 mm clearance holes. Slip in joints is a major issue in bridge engineering, which has to be controlled if the structural scheme is to perform satisfactorily over its service life. The transfer of connection force in FRP joints, by way of frictional force, say by using High Strength Friction Grip (HSFG) bolts, cannot be relied upon [1], because steel bolting is known to lose its pre-tension with time due to the viscoelastic properties of the FRP. The aim of our preliminary study is to offer a potential solution to developing a suitable slip resistant connection. Tests are conducted on double lap-shear joints according to Annex G of BS EN 1090-2:2008 [2]. The hexagon injection bolts and bottom washer are prepared as per Annex K of the same standard. A new top washer has been designed and tested to ensure smooth resin filling in the cavity between bolt (M16) and 2 mm hole clearance. It is expected that resin injected bolting will provide a mechanical fastening system that has locking capabilities. If successful the outcome of our research will address the challenge of durability and will ensure longer service lives for joint limit states under bridge loading. The results will also help in preparation of recognised design guidelines for FRP bridges

Behaviour of pultruded beam-to-column joints using steel web cleats

Response of pultruded Fibre Reinforced Polymer (FRP) beam-to-column joints with steel bolted web cleats is studied through physical testing. Two joint configurations are considered with either three or two bolts per cleat leg, as per drawings in a pultruder’s Design Manual. Moment-rotation curves, failure modes and potential performance gains from semi-rigid action are determined from two batches, each having six nominally identical joints. Results show that initial joint properties for stiffness and moment can possess, at 19 to 62%, an extremely high coefficient of variation. All joints failed by fracturing within the FRP column’s flange outstands. Because this failure mode has not been reported previously there is a need to establish how its existence influences joint design. As joint properties for the three- and two-bolted configurations are not significantly different, the middle (third) bolt is found to be redundant. Damage is shown to initiate within the column flange outstands when the mid-span deflection of a 5.08 m span beam, subjected to a uniformly distributed load, is span/500. This is half the serviceability vertical deflection limit recommended in the EUROCOMP Design Code and Handbook. The mean joint moment resistance for design is established to be 2.9 kNm and this is 1.5 times the moment for damage onset

Design and implementation of a quadruped amphibious robot using duck feet

Roaming complexity in terrains and unexpected environments pose significant difficulties in robotic exploration of an area. In a broader sense, robots have to face two common tasks during exploration, namely, walking on the drylands and swimming through the water. This research aims to design and develop an amphibious robot, which incorporates a webbed duck feet design to walk on different terrains, swim in the water, and tackle obstructions on its way. The designed robot is compact, easy to use, and also has the abilities to work autonomously. Such a mechanism is implemented by designing a novel robotic webbed foot consisting of two hinged plates. Because of the design, the webbed feet are able to open and close with the help of water pressure. Klann linkages have been used to convert rotational motion to walking and swimming for the animal's gait. Because of its amphibian nature, the designed robot can be used for exploring tight caves, closed spaces, and moving on uneven challenging terrains such as sand, mud, or water. It is envisaged that the proposed design will be appreciated in the industry to design amphibious robots in the near future. - 2019 by the authors.Faculty of Robotics and Advanced Computing, Qatar Armed Forces-Academic Bridge Program, Qatar Foundation, 24404 Doha, Qatar Faculty of Engineering, Computing and Science, Swinburne University of Technology, 93350 Sarawak, Malaysia Faculty of Computer Engineering Signal and Image Processing Qatar University, 24404 Doha, Qatar Correspondence: [email protected]

Response of beam-to-column web cleated joints for FRP pultruded members

Physical testing is used to characterize the structural properties of beam-to-column joints, comprising pultruded fiber-reinforced polymer (FRP) H-shapes of depth 203 mm, connected by 128 mm-long web cleats and two M16 bolts per leg. Testing is performed on two batches of nominally identical specimens. One batch had web cleats of pultruded FRP and the other had structural steel. The structural behavior of the joints is based on their moment-rotation responses, failure modes, and serviceability vertical deflection limits. Joints with FRP cleats failed by delamination cracking at the top of the cleats, and when the cleats were of steel, the FRP failure occurred inside the column members. Neither failure mode is reported in the design manuals from pultruders. At the onset of the FRP damage, it was found that the steel joints were twice as stiff as the FRP joints. On the basis of a characteristic (damage) rotation, calculated in accordance with Eurocode 0, the serviceability deflection limits are established to be span/300 and span/650 for the joints with FRP and steel cleats, respectively. This finding suggests that appropriate deflection limits, in relation to cleated connections, should be proposed in manufactures’ design manuals and relative design standards and design codes. Failure to address the serviceability, by the engineer of record, could lead to unreliable designs

Heparan sulphate inhibition of cell proliferation induced by TGFβ and PDGF

The effect of glycosaminoglycans (GAGs) on the proliferation of smooth muscle cells (SMC) and fibroblasts was assessed by culturing cells with or without GAGs. Porcine heparan sulphate (HS) inhibited proliferation in a dose dependent manner. At 167 μg/ml of HS this reached 88% and 72% inhibition of SMC and fibroblast growth, respectively. Pig and beef mucosal heparins also blocked proliferation, but to a lesser extent. In contrast, beef lung heparin, chondroitin sulphate, and dermatan sulphate failed to block growth factor induced proliferation. Continuous presence of HS was not required, suggesting that the inhibitory effects resulted from a direct effect on the cell rather than an interaction of the GAG with growth factors. The mechanism by which GAGs inhibit proliferation will be addressed in future studies

Survey of sediment quality in Sabine Lake, Texas and vicinity

The toxicity of sediments in Sabine Lake, Texas, and adjoining Intracoastal Waterway canals was determined as part of bioeffects assessment studies managed by NOAA’s National Status and Trends Program. The objectives of the survey were to determine: (1) the incidence and degree of toxicity of sediments throughout the study area; (2) the spatial patterns (or gradients) in chemical contamination and toxicity, if any, throughout the study area; (3) the spatial extent of chemical contamination and toxicity; and (4) the statistical relationships between measures of toxicity and concentrations of chemicals in the sediments. Surficial sediment samples were collected during August, 1995 from 66 randomly-chosen locations. Laboratory toxicity tests were performed as indicators of potential ecotoxicological effects in sediments. A battery of tests was performed to generate information from different phases (components) of the sediments. Tests were selected to represent a range in toxicological endpoints from acute to chronic sublethal responses. Toxicological tests were conducted to measure: reduced survival of adult amphipods exposed to solid-phase sediments; impaired fertilization success and abnormal morphological development in gametes and embryos, respectively, of sea urchins exposed to pore waters; reduced metabolic activity of a marine bioluminescent bacteria exposed to organic solvent extracts; and induction of a cytochrome P-450 reporter gene system in exposures to solvent extracts of the sediments. Chemical analyses were performed on portions of each sample to quantify the concentrations of trace metals, polynuclear aromatic hydrocarbons, and chlorinated organic compounds. Correlation analyses were conducted to determine the relationships between measures of toxicity and concentrations of potentially toxic substances in the samples. Based upon the compilation of results from chemical analyses and toxicity tests, the quality of sediments in Sabine Lake and vicinity did not appear to be severely degraded. Chemical concentrations rarely exceeded effects-based numerical guidelines, suggesting that toxicant-induced effects would not be expected in most areas. None of the samples was highly toxic in acute amphipod survival tests and a minority (23%) of samples were highly toxic in sublethal urchin fertilization tests. Although toxic responses occurred frequently (94% of samples) in urchin embryo development tests performed with 100% pore waters, toxicity diminished markedly in tests done with diluted pore waters. Microbial bioluminescent activity was not reduced to a great degree (no EC50 <0.06 mg/ml) and cytochrome P-450 activity was not highly induced (6 samples exceeded 37.1 ug/g benzo[a]pyrene equivalents) in tests done with organic solvent extracts. Urchin embryological development was highly correlated with concentrations of ammonia and many trace metals. Cytochrome P450 induction was highly correlated with concentrations of a number of classes of organic compounds (including the polynuclear aromatic hydrocarbons and chlorinated compounds). (PDF contains 51 pages

Evaluation of FOXM1 inhibitor (FDI-6) as a potential therapeutic molecule for small cell lung cancer

Lung cancer is the leading cause of cancer deaths accounting for about 22% of all cancer related cases in both males and females. Lung cancers are broadly grouped into two types mainly small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) with SCLC accounting for about 15% of all lung cancer cases. SCLC is different from NSCLC because in most cases it originates centrally in the bronchi and is frequently seen in smokers. SCLC is aggressive and one of the most malignant forms of tumor characterized by uncontrolled rapid growth of certain cells in the lungs. SCLC displays poor prognosis because of early-stage metastasis, acquisition of chemoresistance, and has a high rate of recurrence. One of major drivers of chemoresistance is the transcription factor Forkhead box protein M1 (FOXM1) that is responsible for modulating cell cycle proliferation, maintenance of genomic stability, DNA damage response, and cell differentiation in numerous tumor entities. In order to explore properties of SCLC cancer cell lines, human non-bone metastatic SBC3, bone metastatic SBC5, H1688, and murine (RPM) cells were treated with a FOXM1 inhibitor known as FDI-6. As a transcription factor FOXMI binds sequence-specific motifs on DNA through its DNA-binding domain activating proliferation and differentiation-associated genes. Anomalous overexpression of FOXMI is a crucial characteristic in oncogenesis and the development of SCLC. FDI-6 is a novel small molecule inhibitor of FOXM1, and it works by binding directly to FOXM1 protein, to displace FOXM1 from genomic targets in SCLC cells prompting concomitant translational downregulation. Functional assays performed confirm that FDI-6 is a viable FOXMI inhibitor showing therapeutic efficacies in SCLC.https://digitalcommons.unmc.edu/surp2021/1044/thumbnail.jp

Deformation and strength characteristics of Laves phases in titanium alloys

The superior reinforcement nature of Laves phases make them suitable for high-strength applications. Therefore, investigations on the deformation and strength characteristics of Laves phases are useful in development of an improved Laves phase-reinforced alloy. In this work, the Vickers micro-indentation method is used to evaluate and compare the deformation and strength characteristics of a hexagonal close-packed Laves phase (C14-type) in Ti-35Zr-5Fe-6Mn (wt%) and a face-centered cubic Laves phase (C15-type) in Ti-33Zr-7Fe-4Cr (wt%), considering the same volume fraction of Laves phase (~7.0%) in these alloys. Moreover, the effects of higher volume fraction of Laves phase (19.4%) on indentation-based deformation features are evaluated in Ti-35Zr-5Fe-8Mn (wt%). Remarkably, dislocation activity and plastic deformation features are evident in the C15-type Laves phase, whereas the C14-type Laves phase strongly blocks dislocation motion. Therefore, the C15-type Laves phase improves plastic deformability, whereas the C14-type Laves phase improves strength characteristics of Laves phase-reinforced alloys

Beta-type Ti-Nb-Zr-Cr alloys with large plasticity and significant strain hardening

A series of Ti-25Nb-8Zr-xCr (x = 0, 2, 4, 6, 8 wt%) alloys were designed based on DV-Xα cluster method and e=a-Δr diagram with an anticipation to obtain high plasticity and significant strain hardening. The designed alloys were produced through cold crucible levitation melting technique in order to effectively investigate their micro-structures and mechanical properties. The addition of Cr significantly enhances the β stability in the microstructures of the Ti-25Nb-8Zr-xCr alloys. Both yield strength and hardness of the studied alloys increase due to the effect of solid-solution strengthening. By contrast, the plasticity, maximum strength and strain hardening rate are influenced by theβstability as well as the distinct deformation mechanisms. None of the alloys comprising Cr fail up to 100 kN (the load capacity used) and all show impressive plasticity (~75%) and superior maximum compressive strength (~4.5 GPa) at 100 kN. Moreover, the deformation bands, which are found around the hardness indentations, are analyzed for all the investigated alloys. The fracture behaviors of the Ti-25Nb-8Zr-xCr alloys are also studied to observe the characteristics related to crack propagation, plastic deformation and the formation of shear bands

Improved deformation behavior in Ti-Zr-Fe-Mn alloys comprising the C14 type Laves and β phases

Laves phase alloys are promising materials for several structural applications, but the extreme brittleness is the predominant shortcoming of a Laves matrix. One potential solution to overcome this shortcoming is to alloy Laves matrix with some soft matrix. A group of Ti-35Zr-5Fe-xMn (x = 0, 2, 4, 6, 8 wt%) alloys was cast with an aim to improve deformation in Laves alloy compositions. The phase and microstructure analyses reveal dual phase matrices, including a β phase and a C14 type Laves phase in the investigated alloys. The mechanical properties such as yield strength, hardness and plastic strain for the investigated alloys are found to be significantly sensitive to volume fraction of the Laves phase. Ti-35Zr-5Fe shows impressive ultimate compressive strength (~1.7 GPa), yield strength (1138 MPa) and large plastic strain (23.2 %). The fracture mechanisms are dependent on the microstructure of the alloys. Additionally, the work-hardening ability of the investigated alloys have also been evaluated based on the analyses of slip band patterns formed around the micro-hardness indentations. Notably, the extreme brittleness is not encountered in all the Ti-35Zr-5Fe-xMn alloys and all exhibit very good compressive elongation including the maximum (32.5 %) in Ti-35Zr-5Fe