This dissertation examines ancient anchoring practice in the Mediterranean through ca. 1500 CE, as well as the history and technological developments of iron anchors, which are among the most important tools inherited from the ancient world. The methodology employed is holistic in synthesizing archaeological finds, textual, and iconographic evidence, and includes statistical and geographical analysis based on a substantial catalogue of ancient anchor finds. An experimental project is also included where anchor reconstructions were used in the sea and their utility tested. Mooring is one of the least studied aspects of everyday life for the people of the ancient Mediterranean. It has been elucidated that in most circumstances beaching would not have been a practical option, even for warships and the smallest cargo vessels. Rather, vessels were equipped with specialized gear for mooring off or near undeveloped shores. This included ship's boats enabling access to the shore. Lower draft vessels, particularly galleys, could approach unbuilt shores and employ mooring stakes and cables, and the ship's landing-ladder would be deployed into shallow water. Where available, however, ships would benefit from built quays which facilitated goods transport. The iron stock-anchor displays the greatest longevity of any anchoring tool, evinced as early as the 5th c. BCE, and appears to have achieved dominance over wooden types by the 3rd c. CE. From its conception the iron-stock anchor undergoes a broad range of gradual changes to its form and features. The earliest known finds take a 'V' form in the bulk-arms and gradually develop through rounded to 'T' and 'Y' forms in the Byzantine Period. The stocks evolve from removable iron types, to permanent forms entirely of wood. Reintroduction of upward-oriented arm designs from northern Europe around the 13th c. CE, and incorporation of hydraulic mechanized smithing developments, heralded a revolution of anchoring technology. Larger, stronger and more efficient anchors were being produced to standardized dimensions and quality, promoting larger ships, and ultimately resulting in novel characteristics of navigation.

During construction of dams, rock bolts are in general installed in the interface between concrete and rock as an extra safety measure against overturning failure. These bolts are however not allowed to be taken into consideration for the stability calculations of large dams. New standards and new design criterias have increased the requirements of the safety of the old dams, leading to a need for expensive rehabilitation and strengthening. It is possible that consideration of these bolts in stability calculations may lead to money being saved. In order to do so more information about the long term strength of these bolts is needed. One way of getting this information has been the destructive testing of old dugout bolts found during reconstruction works. At the Lima hydropower station in Sweden, this kind of testing was made. The test rig used had a design where a piston pressed down on the rock around the bolt in order to pull it out. The question was raised if this could affect the failure load of the bolt. In this thesis, an attempt was made to answer this question using finite element methods. Models of a rock bolt was made in Abaqus, where one model included the piston and one where it was not. The connection between the bolt and the rock was modelled with nonlinear springs and friction, and the results were then compared between the cases and with experimental data. The results showed that the resulting force-deformation curves may be affected by the piston in cases where the dominant failure mode was adhesive failure, which would influence failure loads and deformations. Since so little was known about the properties of the rock and grout at Lima however, it is difficult to say to which extent the test rig has affected these results.

Suture or bone anchors are used to reattach a tendon or ligament after it has been torn away from the bone. Anchors provide secure attachments to bone during trauma or reconstructive surgery, holding the ligament or tendon in place and potentially allowing greater mobility during recovery. Computer modelling techniques are used to investigate both established bone anchor technology, such as threaded implants, and emerging technologies such as cement augmentation or sonic-fusion. Sonic fusion is an ultrasound-assisted anchoring method which has recently been introduced in low load maxillofacial applications, and is expected to be used in other low load applications such as hallux valgus alignment procedures and suture attachment. Threaded anchors were examined using two Finite Element (FE) models of human cancellous bone, representing both “normal” and “weaker” bone. Simulation and analysis revealed the critical nature of modelling the microstructure of bone. Changing the direction of loading in the model leads to significant changes in the response of the construct, and this cannot be represented in continuum models, or in physical models using artificial cancellous bone. Rapid prototyping (RP) using 3d printing was used for validation of the FE models. While this method has previously been implemented to create physical bone models, testing an assembly model and comparing it to FE results for inclined loading had not been attempted. RP models were created of the threaded anchor in both “normal” and “weaker” bone, and a sonic fusion model in the normal bone was also created. These models were then subjected to mechanical testing. Results produced from the simulation correlated with the physical results. The importance of a cortical layer was re-confirmed. At the apparent densities simulated, engagement with the cortical layer increases pull-out force dramatically. Engaging the anchor even with a thin cortical layer can produce a significant improvement to pull-out strength. Novel sonic fusion FE models were created from a CT scan of animal bone, and the geometry for both the sonic-fusion pin and bone were taken from the CT scan. Computer generated geometry was used to build pin concepts of varying shapes. It was shown that if good engagement is made with bone, as in the case of all of the concepts created, then sonic fusion can produce a good holding power - comparable with that of a threaded anchor. The results showed that sonic-fusion requires less drill penetration into the bone, meaning less of the inherent bone structure is removed – vital for patients with poor bone quality. Bone cement models were investigated. Bone augmentation models were created, and the addition of cement demonstrated an improvement in anchor holding power. The research showed that there are benefits to using FEA as a tool to evaluate the mechanical aspects of cement distribution. The results proved the hypothesis that augmentation will likely increase the holding power of anchor, and its distribution will affect pull-out significantly. This work has created a method for modelling and evaluating both established and novel bone anchor technology in CT bone geometry, a procedure which could be expanded to other bone implants. It has been validated using the innovative approach of rapid prototyping.

This thesis includes experimental and theoretical work performed to investigate the behaviour of ground anchors in sand. The anchor footing used was a circular plate connected to a tie rod. The experimental work was carried out by installing the anchor in a l830mm x 1830mm x l220mm deep tank containing dry sand. The sand sample was prepared by using a vibrator fixed to the bottom of the tank. The anchor was pulled out at a constant rate of strain and the load-displacement curve was recorded on a plotter. The vibration of the tank was defined by deter.mining the acceleratton and amplitude of the motion in the horizontal and vertical directions. A density tube and a hydraulic gauge were designed to investigate the distribution of stresses in sand. The variation of the vibration time, the constant rate of strain, the shaf V plate diameter, the plate thickness/plate diameter, and the boundary distance with the load-displacement curve were also investigated. The load-displacement curve of different diameter plates embedded at various depths for different times of vibration were recorded. To investigate the behaviour of ground anchors theoretically, the finite element technique was used and a computer progra~ developed. A linear stress-strain relationship was used to predj.ct and investigate the behaviour of the anchor. A non-linear stress-strain relationship and a failure criterion were also used to predict the load-displacement curve of the vertical anchor. The effect of the parameters which were investigated experimentally were also examined. The distribution of the load on the anchor plate and the extent of the failure zone were plotted. The predicted and experimental results in this thesis were compared with laboratory and field results obtained by previous researchers.

This study presents the applications of plastic limit analysis to offshore foundations and anchors, including the drag embedment anchors (DEAs) for mobile offshore drilling units (MODU’s) and spudcan foundations for jack-up platforms. In deep waters, drag embedment anchors are an attractive option for mooring of semisubmersible platforms due to low installation cost and high holding capacity; on the other hand, jack-up platforms are more stable than semisubmersible platforms but only can be placed in shallow waters. The analyses of anchor capacities are developed for an idealized anchor comprising a rectangular fluke, a cylindrical shank, and a metal chain connected to the shank at the padeye. The anchor trajectory prediction during drag embedment is also developed by considering anchor behavior in conjunction with the mechanics of the anchor line. The results of simulations show that anchors approach at equilibrium condition rapidly during the embedment and both the normalized holding capacity and the anchor line uplift angle remain constants in this stage. Besides the geometry of the fluke, the properties of the shank and soil are also crucial factors in the anchor-soil interaction behavior. Partial failure of mooring systems for floating structures will subject drag anchors to loads having an appreciable component outside of the intended plane of loading. Partial failure of mooring systems during hurricanes in recent years have generated an interest in understanding drag anchor performance under these conditions. The analysis presents the simulations of three dimensional trajectories of an anchor system subjected to an out-of-plane load component. For the conditions simulated in the example analyses, the anchor experienced a modest amount of continued embedment following partial failure of the mooring system; however, the ultimate embedment and capacity of the anchor is much less than what would have developed if the anchor had continued in its original trajectory within the plane of intended loading. The analyses of the spudcan foundation of jack-up units include preloading, bearing capacity, and the displacement assessment. When the contribution of the soil moment resistance is considered, a three-stage assessment procedure is recommended: superposing environmental forces on the plot of yield surface, determining the value of yield function corresponding to the external forces, and computing the factor of safety of the spudcan. The results of the assessment may be ambiguous while the different yield functions are employed to analyze the spudcan in soft clay.

Doctor of Philosophy / Department of Civil Engineering / Hayder A. Rasheed / The use of carbon fiber reinforced polymer (CFRP) anchors can improve the performance of reinforced concrete (RC) beams strengthened in flexure with CFRP sheets. This improvement results from delaying or controlling the debonding of FRP sheets at failure. In this research, six full-scale T beams and six full-scale rectangular beams are prepared and tested as two separate series. All the specimens are strengthened identically using three layers of unidirectional CFRP sheets and one layer of bidirectional CFRP sheet. The first strengthened beam in each series is anchored with side GFRP bars inserted longitudinally to both sides of the beam. The second strengthened beam in each series is anchored with GFRP patches applied to both sides of the beam. CFRP spike anchors are utilized for the other beams in the two series. The third beam in each series is secured with CFRP spike anchors of 16 mm diameter at 140 mm spacing along the shear span. The fourth strengthened beam in each series is anchored with CFRP spike anchors of 19 mm diameter at 203 mm spacing along the shear span. Four CFRP anchors are applied to each shear span of the fifth beam in each series with 16 mm- diameter (spaced at 406 mm) to secure the flexural CFRP sheets. An end CFRP anchorage technique is considered for the last beam in each series, which includes installing one CFRP spike anchor placed at 76 mm from the free edge of CFRP sheets. The beams were tested under four-point bending until failure and the results for each series are evaluated. In addition, the outcome is compared with other anchorage techniques that have been examined by some researchers utilizing the same beam geometry and properties. The experimental testing and nonlinear analysis showed improvement in the flexural performance of anchored beams compared with those strengthened beams without anchorage. By attaining debonding or rupture failure modes for the T beams and concrete crushing failure mode for the rectangular specimens, the ultimate sectional force capacity is achieved. Accordingly, the results prove that the anchors offer an effective solution against premature debonding failure.

No description available.

<div>Research has shown that many adjacent box beam bridges in Indiana experience premature deterioration. Primarily caused by leaking joints between beams, this deterioration leads to corrosion and/or fracturing of prestressing strands, ultimately resulting in flexural deficiency of the bridge. A testing program was designed to simulate this observed deterioration by constructing test specimens and implementing various strengthening techniques using fiber reinforced polymer (FRP) systems. The objective of this testing program is to investigate the effectiveness of FRP strengthening systems to increase or even regain the full capacity of beams that have effectively lost tension reinforcing steel due to corrosion. The FRP-strengthened beam specimens incorporate the use of near-surface-mounted and externally bonded systems. Reinforcing bars in the beams are excluded or cut to simulate deterioration. Furthermore, two different methods of end anchorage for the externally bonded sheets, FRP fan anchorage and U-wrap anchorage, are investigated. Results and conclusions from the testing program are described in order to help advise best practices in implementing the aforementioned strengthening systems. </div>

No description available.

<p>  </p> <p>The use of headed reinforcement in concrete has found an increasing interest in construction applications. From shear reinforcement in walls to longitudinal reinforcement in beams and columns, there is a growing need to understand the behavior of headed rebars. A headed rebar is a deformed bar with a head attached to its end and while similar anchorage devices such as headed studs and hooked rebars are well established in theory with design equations developed, headed reinforcement lack this level of knowledge and hence, their application in industry is limited.</p> <p>Current code provisions such as fib Model Code 2010 allow the design of headed rebars as (1) a hooked bar, (2) a headed stud, and (3) using experimental results. Moreover, ACI 318-19 only contains a design equation for the development length of headed rebars but not its capacity. While the literature has justified the approximation of the capacity of headed rebars with hooked bars through a multitude of studies comparing both anchorage devices. Such a justification is not well-founded for headed studs due to a scarcity of studies comparing headed rebars to headed studs. Moreover, there is a lack of design equations accurately predicting the behavior of headed rebars in several parameters. All these issues emanate from the complexity of headed rebars due to their joint mechanism of anchorage coming from both resistance along the rebar deformations and bearing on the head.</p> <p>This study aims to better understand the behavior of headed bars by numerically analyzing the influence of different parameters on their performance. Furthermore, direct comparisons are made between headed reinforcement, headed studs, and straight bars to segregate the effect of the bond along the shaft and the bearing at the head on the behavior of headed bars. </p> <p>The parameters included in this study are embedment depth, edge distance, and concrete compressive strength. The numerical models are verified using a 3D non-linear finite element software MASA (Macroscopic Space Analysis) which employs the microplane model with relaxed kinematic constraint as the constitutive laws of concrete. Two numerical approaches, which differ only in the interface properties between the head and concrete, are validated against experimental results before carrying out the parametric study. Several properties including head, concrete, and bond stresses, along with ultimate capacities and crack patterns are extracted from the models and analyzed. Moreover, the load-displacement graphs of headed rebars, studs, and straight rebars are compared and contrasted. Assessments and theories about the discrepancies between the behavior of headed studs and rebars are stipulated. Finally, potential methods for formulating design equations are proposed for future studies.</p>