Type Of Anchor Research Articles

Structural parameters and critical anchorage length of tunnel system bolts made of basalt fibre

Basalt fibre reinforced polymer (BFRP) has the advantages of high tensile strength and good durability; therefore, the anchor bolt developed with BFRP has potential application in tunnel surrounding rock anchorage. This study used meso-scale numerical simulation and laboratory tests to examine the structural parameters of BFRP anchor plate and rod and the critical anchorage length of BFRP cement mortar anchor. The results showed that: 1) the special-shaped truncated cone type anchor plate can convert the axial force into internal tensile stress, which improves the tensile performance of the basalt fibre material. 2) The larger the thread pitch of the BFRP bolt or the smaller the thread height, the more uniform is the shear stress distribution of the bolt thread, and the smaller is the maximum shear stress of the rod and nut. 3) The thread height of 2 mm and thread pitch of 18 mm is the optimal combination. 4) The critical anchoring length of the BFRP cement mortar bolt is 20–40 times its diameter. The findings of this study can provide new and meaningful reference for the application of System Bolts made of Basalt Fiber in tunnel engineering.

Do Career Demands and Career Choices Always Coincide? A Matching Perspective Based on Career Anchors and Job Characteristics

Career choice is an important behavior for people wanting to develop their social life and is a key link to doing so. The matching of career choice with an individual’s real work demands will have a significant impact on the development of individuals, organizations, and society. However, at this stage, there are few studies on this matching situation. From the perspective of the matching of career anchors and job characteristics, this study explored the distribution and different characteristics of employees’ career demands and their career choices through a survey of 407 employees, and further discussed the matching status of these. The results of the study are as follows: (1) Individual career demands (career anchors) presented three attributes: single, multiple, and unclear. Among the single career anchor types, life anchors had the largest proportion, while among multiple career anchor individuals, individuals with both challenge anchors and service anchors accounted for the majority. (2) Individual career demands (career anchors) were significantly different across most demographic variables and organizational/work variables. (3) Deviations between employees’ career demands and their career choices seemed to be a common phenomenon, with the highest degree of fit (62.79%) with the entrepreneurial creativity anchor and the lowest degree of fit (21.28%) with the lifestyle anchor. In addition, in an analysis of three job fit characteristics, the entrepreneurial creativity anchor had a significant preference for managerial characteristics, whereas the challenge anchor had a significant preference for technological characteristics. The degrees of fit of the other anchors were characterized by the frequency of ‘right suboptimal fit’ being larger than that of ‘left suboptimal fit’. In other words, a specific career anchor had a significant preference for job characteristics matched by the right career anchor, with the midpoint of the career anchor octagon model defining the angle of observation. This study provides a reference for human resource management departments and for employees’ recognition and planning of career anchors.

Analisa Perhitungan Dimensi Turap Kayu (Panjang Kayu Ditanam Dan Tebal) Sebagai Dinding Penahan Tanah Sementara

At this time, the development of retaining structures continues to be optimized according to the available land use, to deal with current and future landslides. The structure of the retaining wall (Turap) is expected to provide a solution for the handling. Based on the type of material used, several types of sheet pile are known, namely; wood sheet pile, concrete sheet pile and steel sheet pile, and based on the type of construction there are two types, namely; cantilever type and anchor type. Sheet pile made of wood, the function of this material is to retain the soil which is not so high. This is because the wood material will not be able to withstand excessive soil or gravel loads. In a handling, knowing the function or planning for handling avalanches is very important, because by knowing the purpose and function of the plan, it can be easier in the design and planning process. Calculations for the quality and efficiency of handling can be achieved as desired. The purpose of this study was to analyze the planning calculation of the dimensions of the temporary wood sheet pile (length of planted wood and thickness) as a soil barrier that was built to prevent landslides caused by the intensity of rain. From the results of the research that has been carried out, the planning of wooden sheet piles with a width of 1 meter and 2 meters as retaining walls and for soil volume ranges from 20 KN/M3-30 KN/M3 while the height of sheet piles is 1 meter - 4 meters. It was found that the length of the sheet pile planted did not affect changes in the volume of the soil while the thickness of the wood did.

Experimental study on anchorage mechanism and performance of rock umbrella anchor

The existing reinforcement technology of rock slope and cavern cannot provide large anchoring force and high time efficiency at the same time, which leads to being unable to achieve rapid and effective prevention and rescue in case of landslide, collapse and other dangerous situations. As a new type of mechanical anchoring bolt, rock umbrella anchor is based on the principle of compressing rock mass by tensioning the metal wedge and then producing friction force, finally using the compressive strength of rock mass and interface action to obtain large enough anchoring force. The new anchor can adapt to the deformation of the rock mass, realize rapid anchorage, and obtain larger anchoring force while continuously tensioning. In this paper, the structure composition of rock umbrella anchor is introduced at first. Secondly, based on the geometric characteristics of the structure composition, the anchoring mechanism is analysed and supposed. Thirdly, in-door pull-out model test is conducted to study the structural and anchorage performance of the rock umbrella anchor. In the tests, the deformation characteristics of the anchor are recorded and analysed in the whole pull-out process. Meanwhile, the anchorage failure modes, failure mechanism together with corresponding bearing capacity are obtained, and the influence factors are analysed. Finally, the supposed anchorage mechanism has been verified and the suggestion for application of this new type of anchor is proposed. The results of this paper provide experimental support for the design and engineering application of rock umbrella anchor.

A self-penetration torpedo anchor with vibrational shearing

As the depths at which marine facilities are constructed increase, mooring systems have become more complex, expensive, and difficult to install, making it necessary to develop new types of anchors to replace conventional drag-type anchors. In this paper, a new anchor concept based on the application of sediment fluidization technology is proposed. The proposed self-penetration torpedo anchor has a design similar to that of a torpedo anchor but is equipped with a specially designed mechanical vibrational unit. Laboratory tests were carried out to assess the penetration behavior, holding performance, and pullout behavior of the proposed torpedo under self-induced vibration. To evaluate the effect of installation on the anchorage force, the anchoring forces were measured over different rest times following vertical arrival at designated penetration depths. It was demonstrated that the anchor is able to automatically enter deep beds at moderate penetration speeds and that it has a high holding index, with an anchoring force that can recover more than 83.2% of its holding capacity following 7 d of rest in a silty bed with median particle diameters d50 of 31 μm. Furthermore, unlike conventional torpedo anchors the anchoring force and penetration depth of the self-penetration torpedo anchor are not limited by water depth or drop height. Because the proposed torpedo can be more easily extracted through the application of vibration, problems arising from an inability to pull the anchor out can be more readily avoided.

Experimental and Numerical Studies on the Inflatable Recyclable Anchor in the Tube Piece Type Based on the Soil-Anchor Interaction Mechanism

This paper deeply studies the characteristics and “uplift bearing capacity” of a novel type of inflatable recyclable anchor in the tube piece. The proposed novel inflatable recyclable anchor in the tube piece type comprises a metallic rod, an inflatable anchorage device, and a recovery device. Fifteen field uplift tests are conducted to investigate the effects of inflation pressure, thickness of the steel disc, embedment length, and time lapse between anchor inflation and pullout on “the uplift bearing capacity.” The results show that “the uplift bearing capacity” of the novel inflatable anchor in the tube piece type increases with the increase of inflation pressure, thickness of the steel disc, and embedment length. With the increase of inflation time, “the uplift bearing capacity” of the novel inflatable anchor experiences an increase after first experiencing a decrease. The finite element analysis method is used to establish a numerical analysis model of the inflatable anchor, and the distribution law of the tensile stress of the surrounding soil during the pullout of the anchor is analysed. Compared with the traditional grouted anchor, the proposed anchor has an obvious superiority in recyclability, reusability, and swifter formation of anchorage force and thus is a resource-saving and environmentally friendly anchor technology.

Calcar-guided short-stem total hip arthroplasty: Will it be the future standard? Review and perspectives.

Short stems in total hip arthroplasty (THA) are becoming increasingly popular. In Germany, already 10.4% of all primary THAs are performed using a cementless short stem. The concept of modern, calcar-guided, short stems aims for an individualized reconstruction of the hip anatomy by following the calcar of the femoral neck, a bone- and soft-tissue-sparing implantation technique, and physiological loading. The stem design uses either metaphyseal fixation alone or additional diaphyseal anchoring, depending on the stem alignment and indication. These individualized anchorage types increase the potential indications for the safe use of a short stem. The design features may account for potential advantages of current short stem implants compared with earlier short-stem designs, particularly in cases of reduced bone quality or osteonecrosis of the femoral head and femoral neck fractures. The implantation technique, however, requires distinct knowledge regarding the characteristics of varus and valgus positioning, with the potential for clinical consequences. A learning curve for surgeons new to this technique must be taken into account. Cortical contact with the distal lateral cortex appears to be crucial to provide sufficient primary stability, and the use of intraoperative imaging to identify “undersizing” is highly recommended. Current results of several national registries indicate that calcar-guided short stems are among the most successful implants in terms of mid-term survivorship. However, long-term data remain scarce. This review introduces the characteristics of calcar-guided short-stem THA and summarizes the current evidence.

Investigation and MASH Full-Scale Crash Testing of the Buried-in-Backslope Terminal Compatible with Midwest Guardrail System

Buried-in-backslope (BIB) terminal designs for beam guardrails were developed under the National Cooperative Highway Research Program (NCHRP) Report 350 criteria for 27¾-in. high guardrail systems. The design terminates a W-beam guardrail installation by burying the end terminal in the backslope. When properly designed and located, this type of anchor eliminates the possibility of an end-on impact with the barrier terminal and minimizes the likelihood of vehicular intrusion behind the barrier. Considering the increase in guardrail height to 31 in. in recent years, there is a need to modify the BIB terminal design for a 27¾-in. high guardrail to satisfy current crashworthiness standard criteria for a 31-in. high guardrail. The crash tests reported in this paper were performed in accordance with the Manual for Assessing Safety Hardware (MASH) Tests 3-34 and 3-35 for non-gating terminals, which represent the tests considered necessary to demonstrate MASH compliance of the device. The TL-3 BIB terminal system met MASH requirements and is considered MASH compliant. It is considered suitable for implementation at V-ditch locations with a 4H:1V or flatter foreslope where a MASH TL-3 BIB terminal system is needed and/or desired.

Research on calculation model of penetration depth when anchor touches Seabed

In order to provide a reference for the safe buried depth of underwater pipeline in the navigable waters, this paper on the basis of the famous penetration formula, studied the calculation model of ship’s anchor dropped to seabed. The model considers the main factors that affect the penetration depth, such as the type of anchor, the weight, the speed of bottoming and the substrate condition. The model makes clear the bottom coefficient values, shows the method of hall anchor’s velocity of touching bottom and cross sectional area, and combines with the existing cast anchor experiment results to determine the shape factor of anchor. Using the calculation model, typical scenario was calculated and the calculation result of different methods were compared. The results show that the calculation model is better ease and compliance. It is very important to study the factors affecting the penetration of ship anchor and to determine and evaluate the buried depth of underwater pipeline in navigable waters.

Influence Depth of the Tensile Capacity of Ground Anchors Folding Type in Cohesive Soils

A ground anchor is used to withstand tensile stresses caused by loading both the natural load of the soil and external pressures, then passing the force into the ground. It is generally used to retain tensile form and lateral power structures in constructing walls, foundations, transmission towers, pile, floating docks, mooring dolphin, and offshore buildings. Various ground anchors have been widely used, such as drag, helical, circular-shaped plates, and squares. Especially for massive plate anchors, installation is complicated because it must be excavated first before installation. A challenge in engineering is especially on cohesive soil conditions (soft soil). With these considerations, it is necessary to develop innovative models that are easier to install but still have a large enough tensile capacity. This research analyzes the tensile capacity by using ground anchor folding type to overcome building problems on cohesive soil. The test was tensile capacity with four leaves and a Variation of depth-the performance of this folding type anchor based on the tensile capacity and the anchor. The results obtained in this study; the greater area of the element occurred a significant increase in tensile capacity.

Optimisation of the padeye location for dynamically embedded plate anchors

Dynamically embedded plate anchors (DEPLAs) are a relatively new anchor type that combine the advantages of dynamically installed anchors and conventional plate anchors. Through three dimensional finite element modelling, this paper first derives the combined loading yield surface of the anchor holding capacity in clay and then uses this yield surface in plasticity analyses to study the anchor trajectory under chain loading. These analyses reveal that the anchor padeye in the current DEPLA design is not optimally located as the anchor will eventually pull out of the seabed when loaded beyond its design capacity. It also shows that there are alternative padeye locations that lead to an equilibrium condition, where the DEPLA attains an ultimate holding capacity. The plasticity analyses are supplemented by simplified closed-form equations that are used in a parametric study to calculate the ultimate DEPLA holding capacity for various padeye positions. The optimal padeye location from the analyses is at a location that has a padeye offset ratio (ratio of the normal to the parallel distance between the padeye and the centre of rotation of the plate) in the range 0.55–0.65, varying slightly with chain loading angle.

Post-installed anchors in concrete strengthened by post-installed reinforcement under tensile load

This research discusses post-installed anchors strengthened by post-installed reinforcement (PRs) under tensile loading. Both types of adhesive and expansion anchors were tested under tensile loading. The PRs are reinforcing bars that were installed in a vertical and an inclined direction around a single anchor, as different samples separately. In general, the results showed that the PRs in the vertical direction were more effective than those in the inclined direction. It was found that the tensile capacity of the adhesive anchors significantly improved using the PRs. Although, no major enhancement was recorded in the tensile capacity of the expansion anchors. For both types of anchors, the PRs prevented severe concrete breakout failure. Moreover, with the PRs, a higher ductile behavior was observed at both types of anchors. Employing PRs could be a feasible and practical method to strengthen anchorage systems in concrete and prevent severe damages in concrete substrates.

A review of studies on concrete structures prestressed with external fiber reinforced polymer composites tendons

The studies on concrete structures prestressed with external fiber reinforced polymer (FRP) tendons are reviewed in the aspects of FRP tendon, key technology and structural component, in this review. The tensile properties and long-term behaviors of FRP tendon are firstly introduced. The design-oriented values of creep-rupture stress, relaxation rate and the limits of maximum fatigue stress and fatigue stress range are provided. The advantages and deficiencies of three main types of anchor for FRP tendon, and the methods of reducing the stress concentration on FRP tendon at anchor are elaborated. The newly-developed composite-wedge anchor is emphasized, which possesses an anchor efficiency coefficient exceeding 90%. Meanwhile, the curvature radius of deviator is recommended to be larger than 200 times of the radius the cross-section of FRP tendons, and the bending angle of FRP tendons should not exceed 5°, based on the experimental results on the mechanical properties of deviated FRP tendons. The experimental results of concrete beams prestressed with external FRP tendons are reviewed, including monotonic loading, sustained loading and cyclic loading. The design methodologies in the codes at home and overseas are introduced. The accuracies of the calculating methods in the codes are evaluated using the experimental data of forty-two beams, and the methods in the Chinese code GB 50608—2020 are validated to be accurate in the design calculation for concrete structures prestressed with external FRP tendons. This paper is expected to actively promote the popularization and application of concrete structures prestressed with external FRP tendons.

The Effects of Perfluoroalkyl and Alkyl Backbone Chains, Spacers, and Anchor Groups on the Performance of Organic Compounds as Corrosion Inhibitors for Aluminum Investigated Using an Integrative Experimental-Modeling Approach

The ability of surfactant-like compounds to inhibit the corrosion of aluminum in NaCl solution was systematically investigated. The basic idea of this study was to scrutinize the effect of type of backbone chain (alkyl and perfluoroalkyl), length of backbone chain (number of carbon atoms 7, 10, and 17), various anchor groups (carboxylic, thiol, and imidazole) and presence of alkylene and benzene spacers between perfluoroalkyl chain and anchor group. To tackle these effects, three model studies were designed for alkaline etched, superhydrophilic aluminum surface and then approached experimentally and by density functional theory modeling. This enabled us to decouple the adsorption affinity of selected anchor groups on the hydroxylated aluminum surface from the lateral intermolecular cohesive interactions between hydrophobic backbone chains. Fourteen compounds were used to study the changes in the surface composition, wettability and the electrochemical barrier properties. For the carboxylic anchor group, the length and type of chain are important for barrier properties and also for tuning the wettability of the surface. The addition of alkylene spacer to perfluoroalkyl chain significantly affects the properties of the modified surface. Thiol and imidazole anchor groups, however, are not efficient inhibitors regardless the type and length of backbone chains.

Regenesorb and polylactic acid hydroxyapatite anchors are associated with similar osseous integration and rotator cuff healing at 2 years.

Commercially available suture anchors for rotator cuff repairs can differ significantly in architecture and material. Clinical data on their osseous integration and its effect on patient-reported outcomes is scarce. Preclinical investigations indicated a higher rate of osseous integration for the open-architecture design of the Healicoil Regenesorb anchor than the closed-threaded design of the Twinfix (Smith & Nephew). The purpose of this study was to investigate these 2 anchors with different architecture and material to determine their effect on osseous integration and clinical outcomes after rotator cuff repair. A prospective randomized controlled trial was performed from 2014 to 2019. Sixty-four patients (39 females, 25 males) with an average age of 58.7 years who underwent arthroscopic rotator cuff repair by one of 4 board-certified, fellowship-trained surgeons were randomized to receive Healicoil Regenesorb (PLGA/ß-TCP/Calcium Sulfate) or Twinfix Ultra HA (PLLA/HA) anchors. Thirty-two patients had Healicoil anchors implanted, and 32 patients had Twinfix anchors implanted. Of the 64 patients, 51 returned at 24 months for computed tomographic (CT) examination (25 Twinfix and 26 Healicoil) to determine osteointegration of the anchors. Patient-reported outcomes, including Penn Shoulder Score (PENN), Western Ontario Rotator Cuff Index, visual analog scale, EQ-5D, Single Assessment Numeric Evaluation, Global Rating of Change, were collected at baseline, 6 weeks, 3 months, 6 months, 12 months, and 24 months. Ultrasonography was used to assess rotator cuff integrity after 6 months. Two board-certified, fellowship-trained orthopedic surgeons, blinded to the type of anchors, analyzed the CT scans to assess the anchor osteointegration at 24 months using a previously published grading scale. There were no differences in demographics, preoperative outcomes, or baseline characteristics such as tear size, number of anchors, Goutallier classification, or smoking status between groups. There was no difference in osseous integration between the 2 anchors at 24 months (P = .117). Eight patients had rotator cuff retears, of which 2 patients had Twinfix anchors and 6 patients had Healicoil anchors (P = .18). There were no statistically significant differences in patient-reported outcomes or complications between groups. The 2-year PENN scores were 89 with the Twinfix and 88 with Healicoil anchors (P = .55). Despite differences in material and anchor architecture, the rate of healing and patient-reported outcomes were similar between the Twinfix and Healicoil anchor groups. The rate of osteointegration was the same at 2 years.

Análisis de los resultados y los factores adversos de la reparación artroscópica de las lesiones del subescapular de origen degenerativo

ObjectiveTo carry out a review of degenerative subscapularis ruptures (SSC) after their arthroscopic repair and to evaluate whether the results are comparable in terms of pain and function to those of younger patients with traumatic ruptures. MethodsThe data of 80 SSC tears of the 660 rotator cuff tears operated on by the same team of surgeons from June 2008 to June 2018 were retrospectively reviewed. The clinical data of the surgical indications were collected: age, gender, laterality, intervention delay, associated pathologies, location of pain, value of the Visual Analogue Scale (VAS) and the Constant-Murley test (CMT); surgical data were also collected: type and size of lesion, associated biceps injury and associated surgical procedure, coracoid stenosis and associated surgical procedure, number and type of anchors used. A statistical study was performed with multiple linear regression test, parametric tests (Student's t or ANOVA) and non-parametric tests. ResultsOf 80 patients, 36 were women (45%) and 44, men (55%); mean age 61years (range 47 to 81); mean delay of surgery 3.5months (range 1 to 6); right shoulder affected in 46 cases (57.5%), left in 34 (42.5%); 22 (27.5%) were isolated lesions, 58 (72.5%) were associated with supraspinatus rupture (SE). The mean improvement was 5.0 points in terms of the VAS and 39.9 points on average in the CMT. New breakage rate, 1.25%. Adverse factors: size of the tear, delay in intervention, women. Patients with type I-B rupture have a better overall result in the CMT than types I-A and III. The longer the delay, the worse results are observed, both for the VAS and the CMT. Women present worse and statistically significant results both in the VAS (P=.00) and in the CMT (P=.01). ConclusionsExcellent and good results have been obtained in this group of patients, but there are adverse factors such as the size of the tear, the duration of the symptoms and the association of other pathologies, especially in women.

Prognostic Factors in Open Triangular Fibrocartilage Complex (TFCC) Repair

PurposePatients with triangular fibrocartilage complex (TFCC) injury report ulnar-sided wrist pain and impaired function. Open TFCC repair aims to improve the condition of these patients. Patients have shown reduction in pain and improvement in function at 12 months after surgery; however, results are highly variable. The purpose of this study was to relate patient (eg, age and sex), disease (eg, trauma history and arthroscopic findings), and surgery factors (type of bone anchor) associated with pain and functional outcomes at 12 months after surgery.MethodsThis study included patients who underwent an open TFCC repair between December 2011 and December 2018 in various Xpert Clinics in the Netherlands. All patients were asked to complete Patient-Rated Wrist Evaluation (PRWE) questionnaires at baseline as well as at 12 months after surgery. Patient, disease, and surgery factors were extracted from digital patient records. All factors were analyzed by performing a multivariable hierarchical linear regression.ResultsWe included 274 patients who had received open TFCC repair and completed PRWE questionnaires. Every extra month of symptoms before surgery was correlated with an increase of 0.14 points on the PRWE total score at 12 months after surgery. In addition, an increase of 0.28 points in the PRWE total score at 12 months was seen per extra point of PRWE total score at baseline.ConclusionsIncreased preoperative pain, less preoperative function, and a longer duration of complaints are factors that were associated with more pain and less function at 12 months after open surgery for TFCC. This study arms surgeons with data to predict outcomes for patients undergoing open TFCC repair.Type of study/level of evidencePrognostic II.

Knotless Suture Anchors: A Comparative Biomechanical Study of Acetabular Rim Anchor Fixation with Implications for Hip Labral Repair

AbstractThe purpose of this study was to analyze relevant initial-implantation biomechanical properties of five knotless suture anchors available for use in acetabular labral repair. Five knotless suture anchor constructs were tested: Arthrex PushLock 2.9, Arthrex PushLock 2.4, Arthrex SutureTak 3.0, Stryker CinchLock SS 2.4, and Stryker CinchLock Flex 2.4. Anchors were placed in synthetic bone blocks and in acetabular bone of cadaveric specimens. Constructs were subjected to cyclic and load-to-failure (LTF) testing. Displacement at 1, 100, 250, and 500 cycles, yield load, ultimate load, and failure mode were compared with statistically significant (p < 0.005) differences. PushLock 2.9 mm and CinchLock SS 2.4 anchor constructs had significantly less displacement than PushLock 2.4 mm after 1 cycle (p = 0.017) and 500 cycles (p = 0.043). Excluding “tare” displacement after the first cycle, all anchor constructs were associated with less than 2.0 mm of displacement after 500 cycles. Arthrex PushLock 2.4 and SutureTak 3.0 had the highest number of failures prior to completing cyclic loading. Arthrex PushLock 2.9 was associated with the highest LTF in cadaver (p = 0.00013) and synthetic (p = 0.009) bone models. Most common failure mode in cadaver bone was eyelet failure for all anchor types. Knotless suture anchors used for arthroscopic hip surgery (2.9 mm PushLock, 2.4 mm PushLock, 3.0 mm SutureTak, 2.4 mm CinchLock SS, and 2.4 mm CinchLock Flex) were associated with material properties that met or exceeded the reported thresholds for successful periarticular soft tissue repair surgeries. Based on cyclic and LTF testing in synthetic bone blocks and cadaveric acetabulums, 2.9 mm PushLocks and 2.4 mm CinchLock SS anchors may have potential biomechanical advantages over the other constructs tested. Further functional ex vivo and preclinical animal model studies are recommended to further characterize suture anchor constructs designed for acetabular labrum repair. These results provide novel and relevant biomechanical testing data that contribute to assessing knotless suture anchor constructs for use in acetabular labral repair.

The Helical Anchor Type with Application as a Horizontal Drainage Equipment for Slope Protection

Helical anchors, sometimes referred to as screw anchors, screw piles, and helical piles, are a steel screw-in piling and ground anchoring system used for building deep foundations. Screw piles are manufactured using varying sizes of tubular hollow sections for the pile or anchor shaft. This paper presents an innovation of the helical anchor for horizontal drains, a form of subsurface drainage systems for slope protection. To address the adverse effect of groundwater, an expansion of the application of the helical anchor structure in civil engineering is needed, and new drainage solutions are being considered. The features of the helical anchor type for horizontal drainage equipment, analyses of some of its advantages, and conditions of application are presented. Generally, a helical anchor for horizontal drainage is convenient for installation, maintenance, or removal, and is effective for both horizontal drainage and for anchoring the revetment. It is also a typical construction in drainage works, generally performed by a cranking handle or a rotary-percussion-type drilling machine. The helical anchor pipe for horizontal drainage has many segments with joints using a cranking hand for installation and is quite effective where the installation space is narrow or there is no machine. In particular, the installation of this equipment differs significantly from other drilling methods because it can be driven into a sand layer without a hole wall.

Bond stress distribution analysis between non-prestressed steel strand and concrete in novel beam-to-column connection

The Precast Prestressed Assembled Structural (PPAS) system frame is a novel prefabricated concrete structure, which mainly use 15.2-mm high-strength steel strands as the bottom longitudinal reinforcement. In addition, a certain length of non-prestressed steel strands with 90-degree hooked anchorage type are reserved at the beam end and anchored into concrete column to form a novel beam-to-column connection. The good bond and anchorage performance of steel strand in concrete column is the prerequisite for this connection. However, the bond behaviors such as the bond stress distribution, the bond stress transfer mechanism of the steel strand-to-concrete interface etc. has not been fully understood. For this reason, pull-out tests on six specimens, including thirty-six steel strands with various anchorage type, embedment length and anchorage position, were performed in this research. The results indicated that, compared with straight-line anchorage type, the steel strand with 90-degree hooked anchorage type could increase the ultimate average bond stress and bond stiffness. In addition, the embedment length and anchorage position of the steel strands also had different degrees of influence on the average bond stress. The evolution of strain-pullout load behavior of steel strand was strongly related to the bond position. The anchorage type of steel strand greatly affected the distribution pattern of bond stress between steel strand and concrete. However, the bond stress distribution was always non-uniform along the embedment length, regardless of the anchorage type or embedment length.