When a rope quickly transfers from a slack state to a taut state, a snapping action occurs and produces a large tensile force which is known as a snap load. Energy is dissipated during this snap load, and it is proposed to use synthetic fiber ropes as a type of passive earthquake damper in order to take advantage of this phenomenon. This thesis is the second phase of a multi-stage research project whose goal is to investigate and develop what will be known as Snapping-Cable Energy Dissipators (SCEDs). The experimental data that was collected in the Master'­s Thesis of Nicholas Pearson was organized and analyzed as a part of this research in order to evaluate the behavior of the ropes during the snapping action. Additional tests were also conducted for this project under more controlled conditions in order to better understand how the ropes change throughout a sequence of similar snap loadings and also to determine the amount of energy that is dissipated. The data from both projects was then used as input parameters for a mathematical model that was developed to characterize the behavior of the ropes during a snap load. This model will be utilized in subsequent research involving the finite element analysis of the seismic response of structural frames containing SCEDs. / Master of Science

Energy is lost when a rope transfers from a slack state to a taut state. This transfer is called a snap load and can be very violent. It is proposed to use synthetic fiber ropes as a type of passive control device in new or existing structures to mitigate seismic response. Experimental static and snap load (dynamic) tests were conducted on various synthetic fiber ropes. An eleven-foot-tall drop tower was built in the Virginia Tech Structures and Materials Laboratory in order to conduct these tests. Force and acceleration of the drop plate, which slides vertically within the drop tower, were measured with respect to time for all dynamic tests. Acceleration data was integrated using the trapezoidal or midpoint rule to obtain velocity and displacement values. Plots were made for each test in order to give a better representation of the results. These plots include representations of force and acceleration vs. time, force vs. absolute displacement, force vs. velocity, and force, acceleration, velocity, and displacement vs. time (during the initial taut phase only). Test results show that energy was dissipated in all of the dynamic drop tests, which was expected. Also, the displacement of each rope did not return to zero at the same time that the force returned to zero after the initial snap load. This proves that the ropes undergo some permanent elongation under load. The stiffness of each rope increased with continuous testing. As more tests are conducted on each rope, the strands are pulled tighter into the braided configuration, which causes the rope to become stiffer. / Master of Science

Movement of a bridge superstructure during a seismic event can result in damage to the bridge or even collapse of the span. An incapacitated bridge is a life-safety issue due directly to the damaged bridge and the possible loss of a life-line. A lost bridge can be expensive to repair at a time when a region's resources are most strained and a compromised commercial route could result in losses to the regional economy. This thesis investigates the use of Snapping-Cable Energy Dissipators (SCEDs) to restrain a simply supported single span bridge subjected to three-dimensional seismic loads. SCEDs are synthetic fiber ropes that undergo a slack to taut transition when loaded. Finite element models of six simply supported spans were developed in the commercial finite element program ABAQUS. Two seismic records of the 1940 Imperial Valley and 1994 Northridge earthquakes were scaled to 0.7g PGA and applied at the boundaries of the structure. The SCEDs were modeled as nonlinear springs with an initial slackness of 12.7mm. Comparisons of analyses without SCEDs were made to determine how one-dimensional, axial ground motion and three-dimensional ground motion affect bridge response. Analysis were then run to determine the effectiveness of the SCEDs at restraining bridge motion during strong ground motion. The SCEDs were found to be effective at restraining the spans during strong three-dimensional ground motion. / Master of Science

Blast resistance has recently become increasingly relevant for structural engineers. Blast loads are created by explosive devices that, upon detonation, create pressure loads that are much higher than most that a structure would ever experience. While there are many types of blast loads that are impossible to adequately prepare for, methods are presently being developed to mitigate these loads. This research investigates the possibility of using synthetic fiber ropes as a means of blast resistance. This is the third phase of a multi-stage research endeavor whose goal is to analyze Snapping-Cable Energy Dissipators (SCEDs) for reducing the effects of large-scale lateral loads. Finite element models of portal frames were developed using the commercial finite element program ABAQUS and dynamic models were run for varying blasts and frame systems. Blast pressures of 100, 2,000, and 4,000 psi were applied to a steel portal frame and comparisons were made between unbraced frames and frames braced with springs of different stiffnesses. Additional tests were run to examine the effects of strain rate dependent yield on the results of the models. Parallel research is being conducted on the specific material behavior of the synthetic fiber ropes so that the models developed for this research can be revised for a more accurate determination of the effects of the ropes on structural systems subjected to blast loads. / Master of Science

Seismic design of guyed masts, commonly used in the broadcasting and telecommunications industries, has not been fully addressed in the United States. There is no specific design code, and only a limited amount of research has been reported on the subject. This research investigates the behavior of guyed masts incorporating synthetic ropes as guys, with a particular focus on the effect of snap loads on the mast behavior. This is the third phase of a multi-stage project aimed at analyzing the potential for Snapping-Cable Energy Dissipators (SCEDs) to minimize lateral response in structures. A finite element model of a 120-m-tall guyed mast was developed with the commercial program ABAQUS. The three-dimensional behavior of the mast was observed when subjected to two ground motion records: Northridge and El Centro. Three orthogonal earthquake components were input, two horizontal and one vertical. A series of parametric studies was conducted to determine the sensitivity of the response to guy pretension, which is a measure of the potential slackness in the guys during response. Additionally, the studies examined the effects of guy stiffness, mast properties, and directionality of input motion. Deflections, bending moments, guy tensions, and base shears were examined. The results were used to characterize the trends in the structural response of guyed masts. The level of slackness in the guys changed the behavior, and the lessons learned will be used to continue research on the application of SCEDs in structures. / Master of Science

The presented research investigated the viability of a double-braided synthetic fiber rope for providing improved performance of steel moment frames subjected to earthquake-induced ground motions. A series of experimental tests, including a 1:3-scale dynamic test and 1:6-scale shaking table tests, was conducted using Northridge ground-motion input. A series of nonlinear dynamic analytical studies, using DRAIN-2DX, was conducted to develop the experimental tests. Throughout experimental testing, the ropes exhibited a hyper-elastic loading response and a reduced-stiffness unloading response. A conditioning cycle was defined as a loading cycle induced in the rope above the highest load expected to be experienced by the rope, and was determined to be requisite for ropes intended to be used for the stated objectives of the research program. After experiencing a conditioning cycle, the rope response returned to initial conditions without permanent deformation, demonstrating repeatability of response through several loading cycles below the conditioning load. In the 1:6-scale shaking-table experiments, the ropes drastically improved the performance of the steel moment frames. Maximum and residual drift were reduced significantly, with a corresponding minimal increase to the maximum base shear. Base shear was reduced at several peaks subsequent to the initial pulse of the Northridge ground-motion input. The analytical model developed was excellent for predicting elastic response of the 1:6-scale shaking table experiments and adequate for the purpose of planning shaking table studies. Correlation of peak rope forces between the analytical model and experimental results was poor, and was attributed to limitations of the pre-defined elements used to represent the rope devices in the software program. The inability of the elements to capture the complex unloading response of the rope was specifically noted. / Ph. D.

Seile aus synthetischen Fasern gewinnen zunehmend an Bedeutung für fördertechnische Anwendungen. Wegen ihrer geringen Dichte und Biegesteifigkeit sowie den gleichzeitig mit Stahl vergleichbaren Zugfestigkeiten, haben sich Seile aus ultrahochmolekularen Polyethylenfasern (UHMW-PE) in vielen Anwendungen in der Seefahrt und im Offshore-Bereich durchgesetzt. Die grundsätzliche Eignung solcher Seile für technische Anwendungen, wie z.B. Kräne, Aufzüge, Windenanwendungen, wurde in wissenschaftlichen Studien bereits nachgewiesen. In der vorliegenden Arbeit werden hochfeste Polyethylenfasern verschiedener Hersteller daraufhin untersucht, in wie weit diese durch ihre Eigenschaftsprofile ebenfalls grundsätzlich für technische Anwendungen mit auftretenden Biegewechselbelastungen geeignet sind und welche Anwendungspotentiale sie bieten. Beginnend mit einem kurzen geschichtlichen Abriss über die Entwicklung von synthetischen Polymerfasern und den Einsatz der Fasern in Seilen für technische Anwendungen, sollen grundlegend die Herstellungsverfahren und Eigenschaften von Garnen aus ausgewählten UHMW Polyethylen verglichen werden. Im weiteren Verlauf werden Faserseile aus den gewählten Fasern hinsichtlich Zugfestigkeit, Biegewechselverhalten und Eignung zum Thermofixieren untersucht. Auftretende Effekte werden analysiert und auf die Eigenschaften der Fasern bzw. Garne zurückgeführt. Eine vergleichende Betrachtung der Materialkosten als Teil der gesamten Herstellungskosten der Seile bildet den Abschluss der Arbeit. / This thesis covers investigations on the properties of ultrahigh-molecular-weight (UHMW) polyethylene fibers for use of manufacturing braided fiber ropes for conveyor and hoisting applications. The importance of synthetic fibres for conveying applications has increased during the last years. Due to the low density and bending stiffness at a strength that is comparable to steel, ropes made from high-strength UHMW polyethylene fibres have found their ways into several shipping and off-shore applications. The basic aptitude of UHMW polyethylene fibres to be used in applications like cranes, elevators and winch applications has already been proven in scientific works. Within this thesis, selected UHMW polyethylene fibres are investigated to determine how much their differing property profiles do influence their aptitude to be used in technical applications with cyclic bending loads and for which potentials for fields of application they might be appropriate. Starting with a short overview on the history of synthetic fibres and the use of such fibres in technical applications, manufacturing processes and properties of these fibres are to be compared. Further, fibre ropes, made from the selected fibres, are going to be investigated concerning their tensile strength, behaviour in cyclic bend-over-sheave tests and their aptitude to increase the strength by thermosetting. Occurring effects are going to be analysed and related to the properties of the yarns. A competitive view on the prices of the yarns regarding their portion of the total costs of rope manufacturing is finalising this work.

Seile aus synthetischen Fasern gewinnen zunehmend an Bedeutung für fördertechnische Anwendungen. Wegen ihrer geringen Dichte und Biegesteifigkeit sowie den gleichzeitig mit Stahl vergleichbaren Zugfestigkeiten, haben sich Seile aus ultrahochmolekularen Polyethylenfasern (UHMW-PE) in vielen Anwendungen in der Seefahrt und im Offshore-Bereich durchgesetzt. Die grundsätzliche Eignung solcher Seile für technische Anwendungen, wie z.B. Kräne, Aufzüge, Windenanwendungen, wurde in wissenschaftlichen Studien bereits nachgewiesen. In der vorliegenden Arbeit werden hochfeste Polyethylenfasern verschiedener Hersteller daraufhin untersucht, in wie weit diese durch ihre Eigenschaftsprofile ebenfalls grundsätzlich für technische Anwendungen mit auftretenden Biegewechselbelastungen geeignet sind und welche Anwendungspotentiale sie bieten. Beginnend mit einem kurzen geschichtlichen Abriss über die Entwicklung von synthetischen Polymerfasern und den Einsatz der Fasern in Seilen für technische Anwendungen, sollen grundlegend die Herstellungsverfahren und Eigenschaften von Garnen aus ausgewählten UHMW Polyethylen verglichen werden. Im weiteren Verlauf werden Faserseile aus den gewählten Fasern hinsichtlich Zugfestigkeit, Biegewechselverhalten und Eignung zum Thermofixieren untersucht. Auftretende Effekte werden analysiert und auf die Eigenschaften der Fasern bzw. Garne zurückgeführt. Eine vergleichende Betrachtung der Materialkosten als Teil der gesamten Herstellungskosten der Seile bildet den Abschluss der Arbeit. / This thesis covers investigations on the properties of ultrahigh-molecular-weight (UHMW) polyethylene fibers for use of manufacturing braided fiber ropes for conveyor and hoisting applications. The importance of synthetic fibres for conveying applications has increased during the last years. Due to the low density and bending stiffness at a strength that is comparable to steel, ropes made from high-strength UHMW polyethylene fibres have found their ways into several shipping and off-shore applications. The basic aptitude of UHMW polyethylene fibres to be used in applications like cranes, elevators and winch applications has already been proven in scientific works. Within this thesis, selected UHMW polyethylene fibres are investigated to determine how much their differing property profiles do influence their aptitude to be used in technical applications with cyclic bending loads and for which potentials for fields of application they might be appropriate. Starting with a short overview on the history of synthetic fibres and the use of such fibres in technical applications, manufacturing processes and properties of these fibres are to be compared. Further, fibre ropes, made from the selected fibres, are going to be investigated concerning their tensile strength, behaviour in cyclic bend-over-sheave tests and their aptitude to increase the strength by thermosetting. Occurring effects are going to be analysed and related to the properties of the yarns. A competitive view on the prices of the yarns regarding their portion of the total costs of rope manufacturing is finalising this work.