Tube Anchor Research Articles

Modelling of CFRP-Strengthened RC Shear Walls with a Focus on End-Anchor Effects

This study first provides an overview of the development of a novel tube anchor system for the seismic strengthening or repair of reinforced concrete (RC) shear walls with carbon fibre-reinforced polymer (CFRP) sheets. The new anchor system can significantly improve the load transfer mechanism between the CFRP and supporting RC structural elements, resulting in ductile behaviour of the strengthened shear walls with increases of lateral load capacity and ductility by up to 2.6 and 8.3 times, respectively. The study then presents a new finite element modelling technique capable of capturing the complete cyclic response, i.e., from the elastic behaviour to the ultimate collapse of CFRP-strengthened RC shear walls with the newly developed tube anchor system. Two different modelling approaches are proposed to consider the effects of the tube anchor system. Additionally, other important CFRP- and RC-related mechanisms, including CFRP debonding effects, confinement enhancement, tension stiffening, compression softening, and strength and stiffness degradation under cyclic loads, are also considered in the model. By comparing the analytical and experimental results, it is demonstrated that the proposed modelling approach can accurately replicate the complex behaviour of CFRP-strengthened shear walls with a wide range of aspect ratios, from the ductile flexural behaviour of slender walls to the brittle shear failure of squat walls, without requiring detailed modelling of the anchor system.

Tensile Testing of Carbon FRP (CFRP) and Glass FRP (GFRP) Bars: An Experimental Study

Abstract The available ASTM recommends grout-filled steel tube anchors (STAs) for the tensile testing of 6.4- to 32-mm-diameter glass fiber-reinforced polymer (GFRP) bars and a 9.5-mm-diameter carbon FRP (CFRP) bar. The available ASTM provides minimum STA dimensions for tensile testing of the FRP bars. However, because of the large variations in the FRP bars, the exact STA dimensions for successfully testing the FRP bars in tension vary significantly and depend on the type and diameter of the FRP bar. In this experimental study, tensile testing of 9- and 15-mm-diameter CFRP bars and a 15.9-mm-diameter GFRP bar was successfully conducted using cement grout–filled STAs. For the 9-mm-diameter CFRP bar, a STA of 31.8-mm outer diameter (OD), 17.6-mm inner diameter (ID), and 460-mm anchorage length (La) was used. For the 15-mm-diameter CFRP bar, a STA of 46.3-mm OD, 27.1-mm ID, and 600 mm La was used. For the 15.9-mm-diameter GFRP bar, a STA of 46.3-mm OD, 27.1-mm ID, and 460-mm La was used. This study investigated the effect of anchorage length of STAs, number of sand coat layers, and grout age on the tensile stress–strain response of the FRP bars. The experimental results showed that increasing the anchorage length of STAs and the number of layers of sand coating improved the frictional resistance between the FRP bars and the surrounding cement grout, which resulted in rupturing of the FRP bars. The experimental results showed that FRP bars with grout-filled STAs tested at 3 days of casting failed by the rupturing of FRP bars, whereas FRP bars with grout filled STA tested at 28 days of casting slipped out from STAs during the tensile test.

Movement Tube Detection Network Integrating 3D CNN and Object Detection Framework to Detect Fall

Unlike most of the existing neural network-based fall detection methods, which only detect fall at the time range, the algorithm proposed in this paper detect fall in both spatial and temporal dimension. A movement tube detection network integrating 3D CNN and object detection framework such as SSD is proposed to detect human fall with constrained movement tubes. The constrained movement tube, which encapsulates the person with a sequence of bounding boxes, has the merits of encapsulating the person closely and avoiding peripheral interference. A 3D convolutional neural network is used to encode the motion and appearance features of a video clip, which are fed into the tube anchors generation layer, softmax classification, and movement tube regression layer. The movement tube regression layer fine tunes the tube anchors to the constrained movement tubes. A large-scale spatio-temporal (LSST) fall dataset is constructed using self-collected data to evaluate the fall detection in both spatial and temporal dimensions. LSST has three characteristics of large scale, annotation, and posture and viewpoint diversities. Furthermore, the comparative experiments on a public dataset demonstrate that the proposed algorithm achieved sensitivity, specificity an accuracy of 100%, 97.04%, and 97.23%, respectively, outperforms the existing methods.

Strain integration-based soil shear displacement measurement using high-resolution strain sensing technology

The distributed fiber optic sensing technology has emerged as a promising tool for monitoring soil shear deformation. However, the question remains whether the strain measurements obtained by the soil-embedded optical fiber cables are reliable due to cable-soil slippage. In this paper, a direct shear model test was conducted in laboratory to characterize the cable-soil deformation compatibility considering different anchorage conditions. The optical frequency domain reflectometer was employed to measure cable strains. The measurements were compared with those from the particle image velocity technique. When the strain sensing cable couples well with soil, the cable elongation exhibits a linear relationship with the soil shear displacement. A strain integration method is then proposed to convert strain measurements into shear displacements. Furthermore, the effect of block and tube anchors on the cable-soil coupling behavior is investigated. The conclusions drawn in this study provide a reference for establishing new geotechnical deformation monitoring systems.

3121 Spontaneous Breakage and Antegrade Enteral Migration of Jejunal Extension Tubing

INTRODUCTION: Gastroenteric tube feeding can provide essential nutrition for patients with neurologic or mechanical dysphagia. Many patients undergo pre-pyloric feeding; however, some patients require post-pyloric feeding through jejunal access. These present additional challenges in placement with potential for complications. Here we discuss a rare complication of a jejunal extension portion of a gastrojejunostomy (G-J) tube separating and becoming a foreign body. CASE DESCRIPTION/METHODS: A 77-year old woman with a past medical history of rheumatic heart disease with mitral stenosis and pulmonary hypertension (pHTN) was admitted for acute decompensated pHTN. Three months prior the patient had underwent radiologic percutaneous placement of a pull-type gastric-tube (G-tube) for dysphagia due to severe deconditioning. One week later she developed gastroparesis and the tube was exchanged under fluoroscopy with a 9-french G-J tube extension. Upon admission patient was tolerating tube feeds without complication and underwent intravenous diuresis for her pHTN exacerbation. On hospital day seven she reported onset of abdominal pain and bloating. Physical exam noted new right-upper quadrant tenderness and mild distention, G-J tube insertion site appeared normal without leakage or skin breakdown. Abdominal x-ray showed the jejunal extension tubing had separated from the G-tube balloon insertion and was visualized projecting coiled over right lower quadrant (Figure 1). Tube feeds were held and the gastroenterology service was consulted. At time of re-examination abdominal symptoms had resolved. Given the positioning of the tubing, serial abdominal imaging and supportive measures of daily suppositories to facilitate spontaneous passage by rectum were recommended. The patient was restarted on tube feeds through the remaining G-tube without complication. Ultimately the jejunal extender proceeded through the colon (Figure 2) and passed by rectum 5 days later without complication (Figure 3). DISCUSSION: The placement of jejunal extensions through existing gastrostomy tubes is typically a well-tolerated procedure and antegrade migration of jejunal tubing is rare. In this case the jejunal tubing somehow separated from its gastrostomy tube anchor. In the event of this rare complication it is reasonable to monitor for spontaneous passage with serial imaging as demonstrated in this case, with consideration for surgical exploration or endoscopic retrieval if there is non-progression of the tube or an associated complication.

A concentric tube anchor system for fiber-reinforced polymer retrofit of reinforced concrete structural walls under extreme loads

In reinforced concrete elements strengthened with fiber-reinforced polymer sheets, premature debonding of the fiber-reinforced polymer from the concrete substrate occurs due to lack of anchorage, which reduces the efficiency of the retrofitting system. This article reviews several common anchor systems and describes the development, optimization, and testing of a steel tube anchor in retrofit of reinforced concrete structural elements using externally bonded fiber-reinforced polymer sheets suitable for application to improve resistance against extreme load conditions (e.g. blast, impact, or an earthquake). A detailed review of common anchor designs including the proposed tube anchor based on previous studies on flexure-dominated fiber-reinforced polymer-strengthened reinforced concrete shear walls is presented. In this study, finite element analysis is conducted to verify the observed behavior and better understand the deformation mechanisms of the tube anchor. Finite element modeling is then used to evaluate the influence of different design parameters on its performance and propose a design methodology that can be used to optimize the tube anchor design. To verify the performance of the optimized tube anchor, it is tested in an experimental program on the in-plane seismic strengthening of two shear-dominated squat walls strengthened using fiber-reinforced polymer sheets. Experimental results reveal that the optimized tube anchor performs well in preventing premature debonding and allows the fiber-reinforced polymer composite to achieve a higher level of strain when compared to an alternative anchor system. Finally, a set of design steps for the implementation of the tube anchor in fiber-reinforced polymer retrofit applications for reinforced concrete shear walls are presented.

In-Plane Seismic Strengthening of Nonductile Reinforced Concrete Shear Walls Using Externally Bonded CFRP Sheets

AbstractThis study evaluated the effectiveness of using externally bonded carbon fiber–reinforced polymer (CFRP) sheets to enhance the seismic performance of nonductile reinforced concrete shear wall specimens representative of low aspect ratio walls. The specimens were designed to replicate structural deficiencies typically found in older concrete structures constructed during the 1960s and 1970s. The nonductile reinforcement details included insufficient shear reinforcement, lack of boundary elements, and low concrete compressive strength. The specimens were repaired or strengthened using vertical and horizontal CFRP sheets and then cyclically tested to simulate seismic loading. A tube anchor system was used to transfer the tensile force carried by the CFRP sheet to the foundation of the specimens. Experimental results showed that the CFRP retrofitting system was able to restore the original strength and initial stiffness of severely damaged specimens and significantly increase the flexural strength, du...

Tube Anchor: development of a small medical device from concept to market

Experts probably have to immerse themselves in their discipline for at least a decade before they have the knowledge and insights needed to produce world-class work. Medical practitioners with long...

Ground anchorages: shear tube anchors. Technical note

Ground anchorages: shear tube anchors. Technical note

A Disadvantage of Velcro as an Endotracheal Tube Anchor

A Disadvantage of Velcro as an Endotracheal Tube Anchor

Synthetic resin grouted tube anchors. Technical note : Hagedorn, H Rock Mech Rock Engng, V16, N2, June 1983, P143–149

Synthetic resin grouted tube anchors. Technical note : Hagedorn, H Rock Mech Rock Engng, V16, N2, June 1983, P143–149

Synthetic resin grouted tube anchors

Synthetic resin grouted tube anchors

Developments in the concept of compression tube anchors : Ivering, J W Ground Engng, V14, N2, March 1981, P31–34

Developments in the concept of compression tube anchors : Ivering, J W Ground Engng, V14, N2, March 1981, P31–34

OPTIMUM DESIGN OF FLANGED AND FLUED EXPANSION JOINTS

Optimum design of flanged and flued expansion joints used in heat exchangers is presented. Minimization of the reaction transferred by the expansion joint to the tube sheet or anchor is considered as the objective function. The structure is analysed by the finite element method. Design criteria based on stress limitations are used as constraints. The problem turns out to be a nonlinear optimization problem under multiple loading conditions. Optimization is carried out by the improved move limit method of sequential linear programming. The progress of optimization is discussed and results are presented for two values of nondimensional expansion. For each value four cases of internal pressure have been considered. The optimum configuration of structure is discussed in detail.