Anchorage Failure Research Articles

New insights into the failure mechanisms of horizontal plate anchors in clay during pull-out

Offshore wind developments are moving towards deep-water regions where energy is abundant, visual impact is minimised and the larger turbine sizes can make the energy production more cost-effective. One of the key challenges facing the industry is the development of reliable substructures. While fixed foundation systems are widely used for shallow-water (<60 m) developments, permanent anchors are seen as one of the most viable mooring solutions for floating structures in deep water. In the current study, the pull-out behaviour of square plate anchors in clay was investigated using large-displacement finite-element analysis. The anchor capacity and failure mechanism were considered for a range of embedment ratios and undrained shear strengths. Three distinct modes of anchor failure identified in previous studies were examined through the analysis of four descriptors including: the pull-out capacity of the anchor, the pull-out displacement required to mobilise this capacity, the energy absorbed by the anchor during pull-out and the variation of the pull-out capacity with respect to a normalised overburden pressure. The findings of the study are presented in the form of a series of charts that can aid design through understanding of the factors controlling the development of anchor failure modes, in addition to identifying the transition point between different failure mechanisms.

Failure and Deformation Mechanisms of Vertical Plate Anchors Subjected to Lateral Loading in Sand

Abstract This paper presents an experimental study on the pullout behavior of a vertical plate anchor buried in sand under lateral loading, using the digital image correlation (DIC) technique. Base...

Experimental study on progressive collapse mechanism in braced and tied-back retaining systems of deep excavations

Collapses of braced or tied-back excavations have occurred frequently. However, the influence of the failure of some retaining structure members on the overall safety performance of a retaining system has not been studied. Model tests of failures of retaining piles, struts or anchors were conducted in this study and the load-transfer mechanisms underlying these conditions were analysed. When failures or large deformations occurred in certain piles, the increasing ratios of the bending moments in adjacent piles were much larger in the braced retaining system than in the cantilever system and more easily triggered progressive failure. When the strut elevation was lower or the excavation depth was greater, the degree of influence and range of pile failures became larger. When certain struts or anchors failed, their loads transferred to a few adjacent struts or anchors, possibly leading to further strut or anchor failure. The influence mechanisms of strut or anchor failure on piles were different from those of pile failure. As the number of failed struts or anchors increases, the bending moments of the piles in the failure zone first decrease and then increase to very high values. Therefore, the progressive failure path extends from struts or anchors to piles and will lead to large-scale collapse.

Cyclic and Load-to-Failure Properties of All-Suture Anchors in Human Cadaveric Shoulder Greater Tuberosities

The purpose of this study was to evaluate the cyclic displacement, stiffness, and ultimate load to failure of 3 all-suture anchors in human cadaveric greater tuberosities. Three all-suture anchors indicated for rotator cuff repair were tested in 14 matched pairs of human cadaver fresh-frozen humeri. Anchors were inserted at 3 locations from anterior to posterior along the greater tuberosity and placed 5 mm from the articular margin. The constructs were cycled from 10 to 60 N at 1 Hz for 200 cycles. The anchors that survived cycling were then subjected to a single pull to failure test. A Kruskal-Wallis 1-way analysis of variance on ranks was performed to compare the displacement, stiffness, and ultimate load to failure of the different anchors tested. One matched pair was excluded because of poor bone quality; therefore, 13 matched pairs were included in the study. After 20, 100, and 200 cycles, there was no difference in median displacement between the anchors tested (P= .23, P= .21, P= .18, respectively). The median ultimate load-to-failure between the Iconix (295.2 N, 95% confidence interval [CI], 125-762.2), JuggerKnot (287.6 N, 95% CI, 152.9-584.4), and Q-fix (333.3 N, 95% CI, 165.0-671.9) showed no statistically significant difference (P= .58). After 20, 100, and 200 cycles, there was no difference in median stiffness between the anchors tested (P= .41, P= .19, P= .26 respectively). Displacement greater than 5 mm occurred in 0 Iconix anchors (0%), 1 JuggerKnot anchor (3.64%), and 2 Q-fix anchors (7.69%). One JuggerKnot anchor failed by anchor pullout during cyclic loading. When tested in human cadaveric humeral greater tuberosities 3 all-suture anchors, the 2.9-mm JuggerKnot, the 2.8-mm Q-fix, and the 2.3-mm Iconix, showed no significant differences in median displacement or stiffness after 20, 100, or 200 cycles or in median ultimate load to failure. Although not statistically significant, the Iconix was the only anchor tested to have no failures, whereas the JuggerKnot had both a clinical and catastrophic failure and the Q-fix had 2 clinical failures. Level V, Controlled Laboratory Study.

All-suture anchor pullout results in decreased bone damage and depends on cortical thickness

PurposeTo evaluate the influence of cortical and cancellous bone structure on the biomechanical properties of all-suture and conventional anchors and compare the morphological bone damage after their failure. The hypothesis of the study is that all-suture anchor pullout is less invasive and that the pullout force is influenced by the cortical thickness.MethodsThirty human humeri were biomechanically tested as follows: starting with a load cycle from 20 to 50 N, a stepwise increase of the upper peak force by 0.05 N for each cycle at a rate of 1 Hz was performed. Analysis included maximum pullout strength for three different anchor implantation angles (45°, 90°, 110°) of the two anchor types. After anchor pullout, every sample underwent micro-CT analysis. Bone mineral density (BMD) and cortical thickness were determined at the anchor implantation site. Furthermore, the diameter of the cortical defect and the volume of the bone cavity were identified.ResultsThe maximum pullout strength of all-suture anchors demonstrates a strong correlation to the adjacent cortical thickness (r = 0.82, p ≤ 0.05) with at least 0.4 mm needed to withstand 200 N. No correlation could be seen in conventional anchors. Moreover, no correlation could be detected for local BMD in both anchors. All-suture anchors show a significantly narrower cortical defect as well as a smaller bone cavity following pullout (4.3 ± 1.3 mm vs. 5.3 ± 0.9 mm, p = 0.037; 141 mm3 vs. 212 mm3; p = 0.009). The cortical defect is largest if the anchors are placed at a 45° angle.ConclusionIn contrast to conventional anchors, the pullout force of all-suture anchors depends on the thickness of the humeral cortex. Furthermore, all-suture anchors show a significantly smaller cortical defect as well as decreased bone damage in the case of pullout. Therefore, the clinical implication of this study is that all-suture anchors are advantageous due to their bone preserving ability. Also, intraoperative decortication should not be performed and cortical thickness should be preoperatively evaluated to decrease the risk of anchor failure.

Assessment of Flexion Elongation Relation and Type of Failure after Capsulodesis.

Background Injury of the scapholunate interosseous ligament is the most frequently diagnosed cause of carpal instability and can be treated with a Mayo capsulodesis procedure. During this procedure, a radially based flap of the dorsal radiocarpal complex is attached to the lunate. The procedure attempts to reduce flexion of the scaphoid and restore the scapholunate relationship by crossing the scapholunate interval. To obtain a better understanding of the biomechanical properties and possibly improve the postoperative rehabilitation process, a better understanding of the reconstructions biomechanics is needed. Methods Ten dorsal intercarpal ligament capsulodesis were performed on embalmed wrists to assess the flexion elongation relation at the dorsal intercarpal reconstruction, the dorsal intercarpal complex, and the type of failure during flexion of the wrist. Results The mean elongation of the dorsal intercarpal reconstruction at 70-degree flexion was 0.8 mm. During flexion, the dorsal intercarpal reconstruction showed no ligament tears or failure of the bone anchor. The mean elongation of the dorsal intercarpal complex was 3.9 mm at 70 degrees. During subsequent repeated flexion, four sutures to connect the dorsal intercarpal complex to the surrounding tissue loosened between 55 and 60 degrees. Conclusions These findings suggest that capsulodesis can safely withstand flexion of the wrist until 50 degrees. Clinical Relevance Clinicians should consider the opportunity to start early with controlled active motion. Level of Evidence Not applicable.

Influence of Kinematic Analysis Parameters of Drag Anchor Trajectory Prediction Using Yield Envelope Method

Drag anchor is widely applied in offshore engineering for offshore mooring systems. The prediction of the invisible trajectory during its drag-in installation is challenging for anchor design in determining the anchor final position for ensuring sufficient holding capacity. The yield envelope method based on deep anchor failure for kinematic analysis was proposed as a promising trajectory prediction method for drag anchor. However, there is a lack of analysis on the effects of the parameters applied in the kinematic analysis. The current work studies the effects of the yield envelope parameters, anchor line bearing capacity factor and the anchor/soil interface friction. It is found that the accuracy of the yield envelope parameters has large impact on the prediction results based on deep yield envelopes. Analyses of cases with smooth fluke predict deeper embedment depth than that from analyses of cases with rough fluke. The decrease of the capacity factor results in the increase of the anchor embedment depth, the anchor line load, the anchor chain angle and the stable value of the normalized horizontal load component for the same drag length, while the stable value of the normalized vertical load component decreases when the capacity factor decreases. This illustrates the importance in applying reasonable parameters and improving the method for more reliable prediction of the anchor trajectory.

Novel and reproducible technique coping with intraoperative anchor pullout during arthroscopic rotator cuff repair.

To evaluate the incidence of intraoperative anchor pullout during arthroscopic rotator cuff repair, to compare the outcomes of different methods of managing anchor pullout, and to introduce a new technique for anchor pullout. 1076 patients who underwent arthroscopic rotator cuff repair using a single-row repair technique were included. In 483 patients, rotator cuff repair was performed using a screw-in type anchor, and in 593 patients, soft anchors were used. When intraoperative anchor pullout occurred, it was managed by buddy screwing, anchor insertion in a different location, cement augmentation, or by bar anchoring using a threaded Steinmann pin. Plain radiography and sonography were used to check anchor locations and healing. Fifty-two patients experienced anchor pullout intra- or postoperatively (48 and four patients, respectively). Anchor pullouts were more frequently observed for larger tears, women, older patients, and in patients with preoperative stiffness (limitations of both active and passive movements of the affected shoulder joint). For screw-in type anchors, pullout during surgery occurred in 16 patients (3.3%, 16/483), and all were managed using the buddy screwing technique. For soft anchor cases, pullout occurred in 32 patients (5.4%, 32/593) and was managed by anchor insertion in a different location (17 patients), cement augmentation (two patients), or bar anchoring using a threaded Steinmann pin (13 patients). Three patients managed by buddy screwing and two patients managed by anchor insertion in a different location had anchor failure after repair. Tendon healing at 6months was observed in 12/16 patients treated by buddy screwing, 11/17 treated by anchor insertion in a different location, 2/2 treated by cement augmentation, and 12/13 treated by bar anchoring with a threaded Steinmann pin. Intraoperative anchor pullout during arthroscopic rotator cuff repair is an uncommon but cumbersome complication. There are some techniques already introduced to deal with this complication. In comparison, not one technique is overwhelmingly superior to others; however, our new technique which is bar anchoring with a threaded Steinmann pin could be another solution, since it could utilize primary anchor sites and results appear to be acceptable. Level of evidence III.

Experimental investigation of simply-supported post-tensioned beam after anchorage system failure

In recent years, with the rapid development of China's transportation industry, some existing bridges have needed to be demolished and rebuilt. Bridge demolition is a complex process of structural system conversions. During demolition, the prestressed beam performance is not clear after anchorage system failure. Therefore, it is important to carry out research to better understand the behaviour of post-tensioned prestressed concrete members after anchorage failure. In this paper, the demolition project of the Qingkou interchange ramp bridge of the Fuzhou circumferential highway is taken as research background to carry out an experimental investigation on post-tensioned prestressed concrete beam specimens to study their mechanical performance before and after the failure of the anchorage system. The results show that the anchorage has a longitudinal extrusion effect on the concrete, and the contribution of the concrete and the rebar to the structure decreases from the end to the mid-span of the beams. The failure of the anchorage system affects the cracking load, the crack width and the ultimate bearing capacity, while it has no effect on the final crack distribution and the concrete failure mode. Beyond the limit of elasticity, the prestressing tendons and the concrete grout start to debond, and the bearing capacity of the beam decreases gradually. The crack resistance and the ductility of the prestressed concrete beams are also reduced. After concrete cracking and under the same load condition, the prestressing tendons bear a larger load in the case of anchorage system failure. It is suggested that after the failure of the anchorage system, the contribution of the residual stress in the prestressing tendons to the bearing capacity of the structure be taken into account until the limit of elasticity of the structure is reached.

Unplanned return to OR (UPROR) for children with early onset scoliosis (EOS): a comprehensive evaluation of all diagnoses and instrumentation strategies.

Retrospective analysis of a prospectively collected multicenter database. Our goal was to study unplanned return to the OR (UPROR, a postoperative complication that could not be treated without an additional anesthetic) as a function of C-EOS diagnosis and implant type. Growing concerns over the impact of multiple anesthetic events on the young brain have focused attention on limiting UPROR in early onset scoliosis (EOS). We studied all patients with a diagnosis of EOS who had surgical implantation of growing instrumentation from October 4, 2010, to September 27, 2015, with a minimum 2-year follow-up. Among the complications requiring surgical treatment (revision for implant or anchor failure, infection, or implant removal), we analyzed all UPROR events-those that required a separate anesthetic (could not be treated as part of a planned surgical lengthening) within the first 2years after initial implantation. UPROR was analyzed by diagnosis, deformity type, and implant strategy using the C-EOS classification. A total of 369 patients met inclusion criteria. Eighty-five of the 369 (23%) required unplanned trips to the operating room for various reasons. The C-EOS group at highest risk of an unplanned trip to the operating room is the hyperkyphotic neuromuscular (M3+, 14/85) cohort, followed closely by the congenital (C3N, 9/85) and neuromuscular (M3N, 8/85) groups with normal sagittal profiles and Cobb angles between 50° and 90°. Implant strategy was significantly related to risk of UPROR (p = .009; Table1), with traditional implants (vertically expandable prosthetic titanium rib/traditional growing rod) being less likely to have an UPROR event. Growing instrumentation to treat EOS, when considered comprehensively, results in a true unplanned reoperation rate within 2years of implantation of 23% (85/369). UPROR events are more common with certain C-EOS groups (hyperkyphotic neuromuscular deformities) and implant strategies. Families should be counseled that unplanned anesthetics are common with any implant strategy available today. Level III, therapeutic.

Improving integrity of RC beam‐column joints with deficient beam rebar anchorage

SummaryIn recent earthquakes in developing countries, severe damage was observed on reinforced concrete buildings. This study focuses on exterior beam‐column joints with substandard beam rebar anchorage and seismic strengthening by installing wing walls. First, a series of experiments was conducted to investigate the seismic behavior of exterior joints with substandard beam rebar anchorage representing typical Bangladeshi buildings. Two 0.7‐scaled exterior joint specimens were tested, and these specimens showed beam rebar anchorage failure and/or joint shear failure. Prior to strengthening of the joint, a series of pullout tests was conducted on postinstalled bonded anchors in low‐strength concrete for strengthening design. Then, an experiment was performed to apply the strengthening method by wing walls to one of the exterior joint specimens to improve the integrity, and this method was intended to prevent the failure of beam rebar anchorage. The strengthening method is proposed to extend the development length of beam longitudinal bars by considering the embedment length along the wing walls. The test results verified the effectiveness and applicability of the proposed strengthening method to upgrade exterior RC beam‐column joints with deficient beam rebar anchorage.

Assessing provisions in Eurocode2 for anchoring reinforcing bars with bends

In Eurocode2, the design provisions allow for the anchorage length of reinforcing bars with bends to be calculated as the center line of the bar from the critical section of the member to the end of the straight portion of the bar beyond the bend, with no limit on the maximum value of the length beyond the bend (extension length). This paper thus presents statistical analysis for test results of reinforcing bars anchored with bends, collected from the literature, as a means to assess the performance of the provisions of Eurocode2. Strength of bent bars at an anchorage length depends on many parameters, including concrete compressive strength, embodied as a constant bond stress along the anchorage length; diameter of the bar; concrete side cover; spacing between bars, and confining reinforcement. Test results incorporated in this analysis include 113 simulated beam-column joint specimens with 16, 19, 22, 25, and 36 mm beam bars with stresses at anchorage failure ranging from 213 to 943 MPa, and concrete compressive strengths ranging from 18 to 114 MPa. Each specimen contained 2, 3, or 4 bent beam bars with clear spacing between them ranging from 2db to 11.4db. All specimens contained no confining reinforcement within the joint region and a constant concrete side cover of either 65 mm or 90 mm. The analysis showed that, for a given bar diameter, the predicted bar stress at anchorage failure with limitations as originally integrated on bond stress, concrete cover, and spacing between bars is reasonably safe. However, the ratio of test-to-calculated bar stress decreases as the ratio of extension to embedment length increases, resulting in an unconservative design when the extension length exceeds half of the embedment length. For rational designs, an upper limit on the extension length of half the embedment length is thus suggested.

Revisability of polyetheretherketone suture anchors utilised in primary and revision Bankart repair

BackgroundPolyetheretherketone (PEEK) suture anchors are frequently used in Bankart shoulder stabilisation. This study analyzed the primary stability and revisability of PEEK anchors in-vitro in case of primary Bankart repair and revision Bankart repair after failed primary repair. MethodsTo simulate primary Bankart repair, 12 anchors (Arthrex PEEK PushLock® 3.5 mm) were implanted in 1, 3, 5, 7, 9 and 11 o'clock positions in cadaveric human glenoids and then cyclically tested. To simulate revision Bankart repair, 12 anchors were implanted in the same manner, over-drilled and 12 new anchors of the same diameter were implanted into the same bone socket as the primary anchors and then cyclically tested. The maximum failure loads (Fmax), system displacements, force at clinical failure and modes of failure were recorded. ResultsOne primary anchor failed prematurely due to a technical problem. Three out of 12 revision anchors (25%) dislocated while setting the 25 N preload. The Fmax, the displacement and clinical failure of the remaining 9 revision anchors were non-significant when compared to the 11 primary repair anchors. The main mode of failure in the primary and revision Bankart surgery group was suture slippage. Anchor dislocations were observed four times in the primary and once in the revision repair groups. ConclusionsRevision Bankart repair using PEEK anchors of the same diameter in a pre-existing bone socket is possible but bears high risk of premature anchor failure and can jeopardize the reconstruction. PEEK suture anchor in revision Bankart surgery should be implanted in a new bone socket if possible.

Numerical modeling of submerged mussel longlines with protective sleeves

Farmers growing mussels in offshore environments have turned to submerged longline farming as a relatively safe, reliable and profitable way to produce mussels in the exposed ocean environment. However, variations in the environmental conditions (strong currents and storms) and potential presence of predator species (e.g. eider ducks) require robust engineering approaches to design longline mussel farms and their components.This paper describes application of a mechanistic fluid-structure interaction modeling software Hydro-FE to predict the dynamic response of several mooring/longline/dropper configurations subjected to typical and extreme environmental conditions of a North Atlantic mussel farming site. Hydro-FE is a software tool that expands and modernizes the approach previously implemented in the finite element program Aqua-FE developed at the University of New Hampshire to analyze flexible structures in marine environment. The numerical model takes into account smooth variation of the hydrodynamic forces around the free surface (continuous partial submergence), Reynolds number dependence of drag coefficients of mooring lines and includes contributions of predator-protection sleeves to the overall mechanical response of mussel droppers. The simulations provide estimates of anchor forces, mooring line tensions, and time-series data on the motion of the droppers. This information can be used in the design of mussel longlines to prevent anchor failure, rope breakage, line entanglement and mussel fall-off.

Stability Recovery in London Plane Trees Eight Years After Primary Anchorage Failure

As the intensity and frequency of strong storms increase, the potential for damage to urban trees also increases. So far, the risk of ultimate failure for partially uprooted trees and how they may recover their stability is not well understood. This study sets out to explore if and to what extent trees can regain anchoring strength after their root systems have been overloaded. In 2010, ten London Plane (Platanus × acerifolia) trees were subjected to destructive winching tests. Two trees were pulled to the ground while eight were loaded until primary anchorage failure occurred and were left standing with inclined stems. In 2013, two trees had failed and six were re-tested nondestructively. By 2018, another tree had failed, and we tested the remaining five again. Rotational stiffness was derived for all trials and served as a nondestructive proxy for anchoring strength (R² = 0.91). After eight years, one tree had regained its original strength, while four had reached between 71 and 82% of their initial rotational stiffness. However, three trees failed during the observation period. The results indicate that partially uprooted trees may re-establish stability over time, but some will not and may fail. In our small data set, it was not possible to identify visual criteria that could provide a reliable indication of tree stability recovery, but our data support the assumption that nondestructive pulling tests can be successfully employed to determine good vigorous candidates for retention after partial uprooting.

Finite element modelling of bond–slip at anchorages of reinforced concrete members subjected to bending

The bond mechanism plays a decisive role when anchorage failure in a reinforced concrete (RC) member occurs. A refined model of bond–slip is therefore needed to analyse RC members by analytical or finite element (FE) modelling where the anchorage of reinforcement is critical, such as at a lapped-splice or in any situation where the strength of a bar is required to be developed to achieve its ultimate strength. This paper presents results of FE modelling of some experimental RC specimens with anchorage of deformed steel reinforcing bars in tension, including the cases of end development and lapped splices of bars in specimens subjected to bending. The FE modelling of the anchorage length specimens with bond–slip laws calibrated from experimental results was better able to predict the load–deflection behavior observed during experimental tests. A comparison of the results obtained using the calibrated bond–slip laws with those using conventional Federation Internationale du Beton bond–slip laws is made and discussion is provided on the effects of the anchorage lengths and bar diameters on the bond–slip relationships.

Study on Anchorage Failure and Bolting Measures of Roadway in Weak Rock

A mechanical model for anchorage and surrounding rock was established against the failure of bolting system, the differential equation of load-transfer was solved and the shape and depth of excavation damaged zone (EDZ) of the surrounding rock was analysed. The results show that to achieve full performance of rockbolts materials and to lengthen its service life, two requirements must be met. One is that the load of rockbolt is no more than its load-bearing capacity. The other one is that the anchorage should be located in stable elastic zone. The shape of EDZ is determined by the magnitude and direction of in-situ stress. Reasonable bolting design should abandon the traditional design of uniform support strength. Rather, should adopt coordinated support and nonuniform support design according to the shape of EDZ in field. Based on the above principles, a new type of combination rockbolt with the effect of high resistance and yield pattern was adopted for the new bolting scheme in the main roadway of Puhe Coal Mine. By analyzing the data collected in field, it is concluded that the combination rockbolt can solve the problem that appearing pull-out failure of rockbolts and tensile failure of cablebolts.

Atmospheric Stress Corrosion Cracking of Stainless Steel Rock Climbing Anchors, Part 1

Austenitic stainless steels Cr-Ni (Types 304, 304L, 321, and similar) and Cr-Ni-Mo (Types 316, 316L, 316 Ti, and similar) are susceptible to atmospherically-induced stress corrosion cracking (AISCC) at ambient temperatures if hygroscopic salts such as MgCl2or CaCl2are present on the surface and the air relative humidity (RH) is in a critical range. This phenomenon has been responsible for incidents of rock climbing anchors breaking under minimal load in seaside areas, putting climbers lives at stake. A systematic failure analysis of anchors collected from various seaside locations throughout the world, namely from Portugal, Azores, Hong Kong, Taiwan, South Africa, and Australia, has been performed. Transgranular AISCC was proven the reason for failures in the majority of investigated anchors made of Type 304L stainless steel. Intergranular cracking due to sensitization by improper welding or heat treatment was also identified as a critical safety issue for both Types 304 and 316 stainless steel types. Comparison of literature data and climatic data from the failure locations suggests that limited washing of deposits in confined zones together with elevated temperature and low RH generated locally by direct sunshine are the key factors of AISCC initiation and ultimately of anchor failure.

Biomechanical analysis of conventional anchor revision after all-suture anchor pullout: a human cadaveric shoulder model

The possibility of implanting a conventional anchor at the pullout site following all-suture anchor failure was evaluated in a biomechanical cadaveric model. The hypothesis of the study was that anchor revision would yieldequal biomechanical properties. Ten human humeri were obtained, and bone density was determined via computed tomography. After all-suture anchor (n = 5) and conventional 4.5-mm anchor (n = 5) insertion, biomechanical testing was conducted. Following all-suture anchor pullout, a conventional 5.5-mm anchor was inserted at the exact site of pullout (n = 5) and biomechanical testing was reinitiated. Testing was conducted using an initial preload of 20 N, followed by an unlimited cyclic protocol, with a stepwise increasing force of 0.05 N for each cycle at a rate of 1 Hz until system failure. The number of cycles, maximum load to failure, stiffness, displacement, and failure mode, as well as macroscopic observation at the failure site including diameter, shape, and cortical destruction, were registered. The defect following all-suture pullout showed a mean diameter of 4 mm, and conventional revision was possible in each sample. There was no significant difference between the initial all-suture anchor implantation and the conventional anchor implantation or the conventional revision following all-suture failure regarding mean pullout strength, stiffness, displacement, or total number of cycles until failure. Conventional anchor revision at the exact same site where all-suture anchor pullout occurred is possible and exhibits similar biomechanical properties.

Seismic response investigation on CFDST column to steel beam blind-bolted connections

The blind bolting technique, recognized as a novel solution to connect a beam to a closed section column for unavailable installation from one side, has been gradually employed in concrete filled steel tube (CFST) column to steel beam connections recently. However, unexpected failure modes including bulge of the thin-walled steel tube and anchorage failure of the blind bolt in the core concrete still existed for this type of connection, which resulted in a limited ductility and inferior strength of the connection. Therefore, a novel blind bolted joint was proposed by replacing the CFST column with the concrete-filled double skin steel tubular (CFDST) column to overcome the above problems. A series of interior joint specimens to square CFDST columns were carried out to investigate their seismic behavior. Compared with the CFST column joints, typical failure modes of the CFDST column joints were characterized. Seismic response was also analyzed in terms of the hysteretic performance, strength and stiffness degradation and energy dissipation capacity to explore the effects of the column hollow ratio and end plate type. The experimental results denoted the CFDST column to steel beam joint with blind bolts performed excellent seismic performance. Based on the equivalent method, two simplified analytical models were discussed to evaluate the initial stiffness of this type of joint. The experimental and analytical results were beneficial for the application of semi-rigid connections to CFDST columns in engineering practice.