The simulation of seafloor-steel catenary interaction and prediction of riser fatigue life required an accurate characterization of seafloor stiffness as well as realistic description of riser load-deflection (P-y) response. This thesis presents two load-deflection (P-y) models (non-degradating and degradating models) to simulate seafloor-riser interaction. These two models considered the seafloor-riser system in terms of an elastic steel pipe supported on non-linear soil springs with vertical motions. These two models were formulated in terms of a backbone curve describing self-embedment of the riser, bounding curves describing P-y behavior under extremely large deflections, and a series of rules for describing P-y behavior within the bounding loop. The non-degradating P-y model was capable of simulating the riser behavior under very complex loading conditions, including unloading (uplift) and re-loading (downwards) cycles under conditions of partial and full separation of soils and riser. In the non-degradating model, there was a series of model parameters which included three riser properties, two trench geometry parameters and one trench roughness parameter, two backbone curve model parameters, and four bounding loop model parameters. To capture the seafloor stiffness degradation effect due to cyclic loading, a degradating P-y model was also developed. The degradating model proposes three degradation control parameters, which consider the effects of the number of cycles and cyclic unloading-reloading paths. Accumulated deflections serve as a measure of energy dissipation. The degradating model was also made up of three components. The first one was the backbone curve, same as the non-degradating model. The bounding loops define the P-y behavior of extreme loading deflections. The elastic rebound curve and partial separation stage were in the same formation as the non-degradating model. However, for the re-contact and re-loading curve, degradation effects were taken into the calculation. These two models were verified through comparisons with laboratory basin tests. Computer codes were also developed to implement these models for seafloor-riser interaction response.

The simulation of seafloor-steel catenary interaction and prediction of riser fatigue life required an accurate characterization of seafloor stiffness as well as realistic description of riser load-deflection (P-y) response. This thesis presents two load-deflection (P-y) models (non-degradating and degradating models) to simulate seafloor-riser interaction. These two models considered the seafloor-riser system in terms of an elastic steel pipe supported on non-linear soil springs with vertical motions. These two models were formulated in terms of a backbone curve describing self-embedment of the riser, bounding curves describing P-y behavior under extremely large deflections, and a series of rules for describing P-y behavior within the bounding loop. The non-degradating P-y model was capable of simulating the riser behavior under very complex loading conditions, including unloading (uplift) and re-loading (downwards) cycles under conditions of partial and full separation of soils and riser. In the non-degradating model, there was a series of model parameters which included three riser properties, two trench geometry parameters and one trench roughness parameter, two backbone curve model parameters, and four bounding loop model parameters. To capture the seafloor stiffness degradation effect due to cyclic loading, a degradating P-y model was also developed. The degradating model proposes three degradation control parameters, which consider the effects of the number of cycles and cyclic unloading-reloading paths. Accumulated deflections serve as a measure of energy dissipation. The degradating model was also made up of three components. The first one was the backbone curve, same as the non-degradating model. The bounding loops define the P-y behavior of extreme loading deflections. The elastic rebound curve and partial separation stage were in the same formation as the non-degradating model. However, for the re-contact and re-loading curve, degradation effects were taken into the calculation. These two models were verified through comparisons with laboratory basin tests. Computer codes were also developed to implement these models for seafloor-riser interaction response.

Three progressively larger statnamic lateral load tests were performed on a 2.59 m diameter drilled shaft foundation after the surrounding soil was liquefied using down-hole explosive charges. An attempt to develop p-y curves from strain data along the pile was made. Due to low quality and lack of strain data, p-y curves along the test shaft could not be reliably determined. Therefore, the statnamic load tests were analyzed using a ten degree-of-freedom model of the pile-soil system to determine the equivalent static load-deflection curve for each test. The equivalent static load-deflection curves had shapes very similar to that obtained from static load tests performed previously at the site. The computed damping ratio was 30%, which is within the range of values derived from the log decrement method. The computer program LPILE was then used to compute the load-deflection curves in comparison with the response from the field load tests. Analyses were performed using a variety of p-y curve shapes proposed for liquefied sand. The best agreement was obtained using the concave upward curve shapes proposed by Rollins et al. (2005) with a p-multiplier of approximately 8 to account for the increased pile diameter. P-y curves based on the undrained strength approach and the p-multiplier approach with values of 0.1 to 0.3 did not match the measured load-deflection curve over the full range of deflections. These approaches typically overestimated resistance at small deflections and underestimated the resistance at large deflections indicating that the p-y curve shapes were inappropriate. When the liquefied sand was assumed to have no resistance, the computed deflection significantly overestimated the deflections from the field tests.

Pile caps are used in foundation design to aid multiple single piles to act as a pile group to resist lateral forces that may cause overturning moments. The pile cap and pile group resist these forces by pile-soil-pile interaction, base and side friction along the pile cap-backfill interface, and passive earth resistance. Passive earth resistance has been neglected in design due to a limited amount of full-scale testing. This research presents the results of a combination of hydraulic actuator and eccentric-mass shaker full-scale testing of a pile cap with loose silty sand backfill to quantify the contribution of the passive earth resistance to the lateral force resistance. The test cap is 1.12 m tall and 5.18 x 3.05 m in plan view, connecting 12 steel pipe piles (324mm O.D) placed in a 4 x 3 pattern with center-to-center spacing of 4.4 and 3.3 pile-diameters in the long and short dimensions, respectively. The hydraulic actuator applied a static load to the system (backfill + pile group) while the eccentric-mass shaker introduced cyclic and dynamic loading to the system. The passive earth resistance accounted for approximately 22% of the total system resistance, with piles contributing approximately 78%. Furthermore, the results produce general correlations between cyclic and dynamic effects on degradation of the backfill provided by the testing and soil characteristics obtained, including target (static) displacement, dynamic displacement amplitude, stiffness, and damping. The dynamic displacement amplitudes during the eccentric mass shaker tests typically ranged between .4 and 2 mm for frequencies between 5 and 9.5 Hz representing behavior under reloading conditions rather than virgin loading conditions. Generally, the presence of the loose silty sand backfill nearly doubled the dynamic stiffness of the pile cap. The stiffness of the backfill and pile cap combined was typically between 100 and 200 kN/mm for frequencies between 4 and 8 Hz, while the stiffness for the backfill alone was typically a decreasing trend between 100 and 40 kN/mm for the same frequency range. The overall isolated loose silty sand damping ratio shows a general increasing trend with values from 32% to 55% for frequencies 3 and 8 Hz.

This thesis presents the results of a research project to investigate the behaviour of the two components of a reverse channel connection to concrete filled tubular sections: the reverse channel and the steel tubular section, at both ambient and elevated temperatures. This research forms part of a European Union funded project on the robustness of joints to composite columns under fire conditions. The specific objectives of this research are to develop methods of quantifying the load-deformation behaviour at various temperatures of the two components. This research has been carried out through a combination of experiments, numerical simulations and analytical developments. Two series of tests have been carried out at different elevated temperatures, one for the reverse channels with lateral loads to the web applied as tensile loads through bolts and one for the concrete filled tubular sections under lateral loads applied through two steel plates (simulating the legs of a reverse channel) in the longitudinal direction of the section. These tests have been used to provide data for the validation of the numerical models based on using the general finite element package ABAQUS. The validated numerical models have been used to conduct a number of parametric studies to provide extensive data for the development of analytical methods to determine the load-deflection characteristics of the two components. For the reverse channel web, the load-deflection relationship consists of two parts and this research has developed analytical equations to predict initial stiffness, yield and ultimate resistance. The initial stiffness is based on extending and simplifying the Timoshenko solution for a plate under a block of lateral loads. The yield resistance is based on the yield line solution that the failure patterns were chosen based on the results attained from test and simulations. The ultimate resistance was calculated based on virtual work principle for the patterns considered in the yield resistance part. For the rectangular concrete filled tubular sections under lateral pulling forces applied through two plates, the load-deflection curve consists of two parts, depicting a linear phase followed by a nonlinear part. This research has developed expressions to calculate initial stiffness, yield resistance, and ultimate resistance. The initial stiffness is formulated according to the Timoshenko solution for a partially loaded plate. The yield resistance is determined by employing yield line solution for the yield patterns obtained from both the test and FE modelling. The ultimate resistance is evaluated by implementing the virtual work principle to the patterns considered in former part. The analytical load-deflection solutions have been compared with the numerical simulation and the experimental results and the agreement is generally satisfactory.

Textile Reinforced Concrete (TRC) with a small thickness, high tensile and compressive strength has been combined with lightweight materials to create sandwich elements. Due to the low strength of the core materials in the sandwich elements, the additional shear connector devices were suggested to improve the load capacity. However, it raised an idea of using a higher strength material core, Expanded Polystyrene Concrete (EPC), without any connector devices to create a new type of lightweight sandwich element, which can be an answer for not only developing lightweight structures but also solving environmental problems. In this thesis, this novel idea was gradually realized with a study on TRC-EPC sandwich beams. Firstly, experimental material tests on EPC showed the possibility to recycle EPS waste for EPC with a density of around 950 kg/m3. Thus, an EPC with a density of 920 kg/m3 and a compressive strength of 5.2 N/mm2 was chosen for the core to realize the concept for TRC-EPC sandwich with 18 experimental beams. Bending tests of six series with shear-to-depth-ratio (a/d) from 1.5 to 5.2 were implemented to study load responses of this type of sandwich beam. The failure moments of all the specimens were smaller than the nominal moment strength of the cross section. The load capacities of the specimens depend strongly on the ratio a/d. The calculations for the shear capacity according to standards as well as shear calculation approaches were implemented. Due to their generalized form, ACI 318-05 and EC2 offer conservative results for a/d<5.2. The dependence of the shear capacity on a/d could be better described with CEB-FIB Model Code 1990. For the beams with 1.5<a/d and a/d<2.1, Strut and Tie Model gave the most suitable results. In case a/d>2.1, ZINK’s model offered better results than the others. Besides, a new proposed equation for the shear capacity of TRC-EPC sandwich beams depending on the a/d was also suggested. In order to model the load response of the six experimental series, FEM models with ATENA developed. The models with and without a consideration of the bond between the textile and fine HSC in the TRC layer underestimated the load capacity with tolerance 26% and 28 % respectively. The tolerances for the deflections in the models with a/d>2.5 were around 22 % and 23%. Finally, an engineering model originally based on sandwich theory was developed to model the load-deflection response of this type of sandwich beams. The model could predict the displacement with tolerances from -24 % to 12 %. The load capacity of TRC-EPC sandwich beams was underestimated with a tolerance in the range of 15- 34 %. / In dieser Arbeit wurde eine neue Sandwichkonstruktion untersucht, für die Textilbeton, ein Werkstoff mit geringer Dicke und gleichzeitig hoher Zug- und Druckfestigkeit, mit leichten Kernmaterialien kombiniert wurde. Aufgrund der geringen Festigkeit der Kernmaterialien werden in vielen Sandwichkonstruktionen zusätzliche Schubverbinder benötigt, um eine ausreichende Tragfähigkeit zu erreichen. Dies führte zu der Idee, Expanded Polystyrene Concrete (EPC) als höherfestes Kernmaterial zu verwenden, das keine zusätzlichen Verbindungsmittel benötigt. Damit entsteht eine neuartige Sandwichkonstruktion, die nicht nur eine Lösung für die Entwicklung neuer leichter Strukturen ist, sondern auch für Umweltprobleme. Diese Idee wurde in dieser Arbeit durch theoretische und experimentelle Untersuchungen an Textilbeton-EPC-Sandwichbalken umgesetzt. Zunächst wurden Materialuntersuchungen an EPC durchgeführt, um nachzuweisen, dass es möglich ist, EPC mit einer Dichte von rund 950 kg/m³ mit recyceltem EPS herzustellen. Für die anschließenden Untersuchungen an 18 Sandwichbalken wurde dann ein EPC mit einer Dichte von 920 kg/m³ und einer Druckfestigkeit von 5,2 N/mm² ausgewählt. In 6 Serien von Sandwichbalken wurden 4-Punkt-Biegeversuche mit Schubschlankheiten von 1,5 bis 5,2 durchgeführt. Die Bruchmomente aller Balken waren geringer als die rechnerische Momententragfähigkeit des Querschnitts und die Tragfähigkeit war stark von der Schubschlankheit abhängig. Es wurden Berechnungen zur Schubtragfähigkeit nach den verschiedenen internationalen Normen durchgeführt. Aufgrund ihrer allgemeingültigen Form ergaben ACI 318-05 und EC2 sehr konservative Ergebnisse für Schubschlankheiten kleiner als 5,2. Die Formulierung des CEB-FIB Model Code 1990 war besser geeignet, die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit abzubilden. Für die Balken mit Schubschlankheiten a/d=1,5 bis 2,1 brachten Stabwerkmodelle ausreichend gute Ergebnisse. In Fällen mit a/d>2,1 ergab das Modell von Zink die besten Übereinstimmungen. Um die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit besser erfassen zu können, wurde eine neue Berechnungsgleichung für Textilbeton-EPC-Balken vorgeschlagen. Um das Last-Verformungsverhalten der experimentellen Untersuchungen beschreiben zu können, wurden FEM-Modelle mit der Software ATENA entwickelt. Es wurden verschiedene Modelle untersucht, die den Verbund zwischen dem textilen Gelege und dem Feinbeton unterschiedlich stark berücksichtigten. Die Tragfähigkeit der untersuchten Balken wurde mit den FEM-Modellen um ca. 26% bis 28% unterschätzt. Die Abweichungen in den berechneten Durchbiegungen betrugen für die Balken mit a/d>2,5 ca. 22% bis 23%. Abschließend wurde ein Ingenieurmodell auf Grundlage der Sandwichtheorie entwickelt, mit dem das Last-Verformungsverhalten dieser Sandwichkonstruktion gut beschrieben werden kann. Mit dem Modell ergaben sich Abweichungen von -24% bis +12% zwischen experimentellen und theoretisch ermittelten Verformungen. Die Tragfähigkeit wurde mit einer Abweichung von 15% bis 34% unterschätzt.

The current design procedure for steel frame structures is a two-step process including an elastic analysis to determine design actions and a separate member capacity check. This design procedure is unable to trace the full range of load-deflection response and hence the failure modes of the frame structures can not be accurately predicted. In recent years, the development of advanced analysis methods has aimed at solving this problem by combining the analysis and design tasks into one step. Application of the new advanced analysis methods permits a comprehensive assessment of the actual failure modes and ultimate strengths of structural steel systems in practical design situations. One of the advanced analysis methods, the refined plastic hinge method, has shown great potential to become a practical design tool. However, at present, it is only suitable for a special class of steel frame structures that is not subject to lateral torsional buckling effects. The refined plastic hinge analysis can directly account for three types of frame failures, gradual formation of plastic hinges, column buckling and local buckling. However, this precludes most of the steel frame structures whose behaviour is governed by lateral torsional buckling. Therefore, the aim of this research is to develop a practical advanced analysis method suitable for general steel frame structures including the effects of lateral-torsional buckling. Lateral torsional buckling is a complex three dimensional instability phenomenon. Unlike the in-plane buckling of beam-columns, a closed form analytical solution is not available for lateral torsional buckling. The member capacity equations used in design specifications are derived mainly from testing of simply supported beams. Further, there has been very limited research into the behaviour and design of steel frame structures subject to lateral torsional buckling failures. Therefore in order to incorporate lateral torsional buckling effects into an advanced analysis method, a detailed study must be carried out including inelastic beam buckling failures. This thesis contains a detailed description of research on extending the scope of advanced analysis by developing methods that include the effects of lateral torsional buckling in a nonlinear analysis formulation. It has two components. Firstly, distributed plasticity models were developed using the state-of-the-art finite element analysis programs for a range of simply supported beams and rigid frame structures to investigate and fully understand their lateral torsional buckling behavioural characteristics. Nonlinear analyses were conducted to study the load-deflection response of these structures under lateral torsional buckling influences. It was found that the behaviour of simply supported beams and members in rigid frame structures is significantly different. In real frame structures, the connection details are a decisive factor in terms of ultimate frame capacities. Accounting for the connection rigidities in a simplified advanced analysis method is very difficult, but is most critical. Generally, the finite element analysis results of simply supported beams agree very well with the predictions of the current Australian steel structures design code AS4100, but the capacities of rigid frame structures can be significantly higher compared with Australian code predictions. The second part of the thesis concerns the development of a two dimensional refined plastic hinge analysis which is capable of considering lateral torsional buckling effects. The formulation of the new method is based on the observations from the distributed plasticity analyses of both simply supported beams and rigid frame structures. The lateral torsional buckling effects are taken into account implicitly using a flexural stiffness reduction factor in the stiffness matrix formulation based on the member capacities specified by AS4100. Due to the lack of suitable alternatives, concepts of moment modification and effective length factors are still used for determining the member capacities. The effects of connection rigidities and restraints from adjacent members are handled by using appropriate effective length factors in the analysis. Compared with the benchmark solutions for simply supported beams, the new refined plastic hinge analysis is very accurate. For rigid frame structures, the new method is generally more conservative than the finite element models. The accuracy of the new method relies on the user's judgement of beam segment restraints. Overall, the design capacities in the new method are superior to those in the current design procedure, especially for frame structures with less slender members. The new refined plastic hinge analysis is now able to capture four types of failure modes, plastic hinge formation, column buckling, local buckling and lateral torsional buckling. With the inclusion of lateral torsional buckling mode as proposed in this thesis, advanced analysis is one step closer to being used for general design practice.

Textile Reinforced Concrete (TRC) with a small thickness, high tensile and compressive strength has been combined with lightweight materials to create sandwich elements. Due to the low strength of the core materials in the sandwich elements, the additional shear connector devices were suggested to improve the load capacity. However, it raised an idea of using a higher strength material core, Expanded Polystyrene Concrete (EPC), without any connector devices to create a new type of lightweight sandwich element, which can be an answer for not only developing lightweight structures but also solving environmental problems. In this thesis, this novel idea was gradually realized with a study on TRC-EPC sandwich beams. Firstly, experimental material tests on EPC showed the possibility to recycle EPS waste for EPC with a density of around 950 kg/m3. Thus, an EPC with a density of 920 kg/m3 and a compressive strength of 5.2 N/mm2 was chosen for the core to realize the concept for TRC-EPC sandwich with 18 experimental beams. Bending tests of six series with shear-to-depth-ratio (a/d) from 1.5 to 5.2 were implemented to study load responses of this type of sandwich beam. The failure moments of all the specimens were smaller than the nominal moment strength of the cross section. The load capacities of the specimens depend strongly on the ratio a/d. The calculations for the shear capacity according to standards as well as shear calculation approaches were implemented. Due to their generalized form, ACI 318-05 and EC2 offer conservative results for a/d<5.2. The dependence of the shear capacity on a/d could be better described with CEB-FIB Model Code 1990. For the beams with 1.5<a/d and a/d<2.1, Strut and Tie Model gave the most suitable results. In case a/d>2.1, ZINK’s model offered better results than the others. Besides, a new proposed equation for the shear capacity of TRC-EPC sandwich beams depending on the a/d was also suggested. In order to model the load response of the six experimental series, FEM models with ATENA developed. The models with and without a consideration of the bond between the textile and fine HSC in the TRC layer underestimated the load capacity with tolerance 26% and 28 % respectively. The tolerances for the deflections in the models with a/d>2.5 were around 22 % and 23%. Finally, an engineering model originally based on sandwich theory was developed to model the load-deflection response of this type of sandwich beams. The model could predict the displacement with tolerances from -24 % to 12 %. The load capacity of TRC-EPC sandwich beams was underestimated with a tolerance in the range of 15- 34 %. / In dieser Arbeit wurde eine neue Sandwichkonstruktion untersucht, für die Textilbeton, ein Werkstoff mit geringer Dicke und gleichzeitig hoher Zug- und Druckfestigkeit, mit leichten Kernmaterialien kombiniert wurde. Aufgrund der geringen Festigkeit der Kernmaterialien werden in vielen Sandwichkonstruktionen zusätzliche Schubverbinder benötigt, um eine ausreichende Tragfähigkeit zu erreichen. Dies führte zu der Idee, Expanded Polystyrene Concrete (EPC) als höherfestes Kernmaterial zu verwenden, das keine zusätzlichen Verbindungsmittel benötigt. Damit entsteht eine neuartige Sandwichkonstruktion, die nicht nur eine Lösung für die Entwicklung neuer leichter Strukturen ist, sondern auch für Umweltprobleme. Diese Idee wurde in dieser Arbeit durch theoretische und experimentelle Untersuchungen an Textilbeton-EPC-Sandwichbalken umgesetzt. Zunächst wurden Materialuntersuchungen an EPC durchgeführt, um nachzuweisen, dass es möglich ist, EPC mit einer Dichte von rund 950 kg/m³ mit recyceltem EPS herzustellen. Für die anschließenden Untersuchungen an 18 Sandwichbalken wurde dann ein EPC mit einer Dichte von 920 kg/m³ und einer Druckfestigkeit von 5,2 N/mm² ausgewählt. In 6 Serien von Sandwichbalken wurden 4-Punkt-Biegeversuche mit Schubschlankheiten von 1,5 bis 5,2 durchgeführt. Die Bruchmomente aller Balken waren geringer als die rechnerische Momententragfähigkeit des Querschnitts und die Tragfähigkeit war stark von der Schubschlankheit abhängig. Es wurden Berechnungen zur Schubtragfähigkeit nach den verschiedenen internationalen Normen durchgeführt. Aufgrund ihrer allgemeingültigen Form ergaben ACI 318-05 und EC2 sehr konservative Ergebnisse für Schubschlankheiten kleiner als 5,2. Die Formulierung des CEB-FIB Model Code 1990 war besser geeignet, die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit abzubilden. Für die Balken mit Schubschlankheiten a/d=1,5 bis 2,1 brachten Stabwerkmodelle ausreichend gute Ergebnisse. In Fällen mit a/d>2,1 ergab das Modell von Zink die besten Übereinstimmungen. Um die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit besser erfassen zu können, wurde eine neue Berechnungsgleichung für Textilbeton-EPC-Balken vorgeschlagen. Um das Last-Verformungsverhalten der experimentellen Untersuchungen beschreiben zu können, wurden FEM-Modelle mit der Software ATENA entwickelt. Es wurden verschiedene Modelle untersucht, die den Verbund zwischen dem textilen Gelege und dem Feinbeton unterschiedlich stark berücksichtigten. Die Tragfähigkeit der untersuchten Balken wurde mit den FEM-Modellen um ca. 26% bis 28% unterschätzt. Die Abweichungen in den berechneten Durchbiegungen betrugen für die Balken mit a/d>2,5 ca. 22% bis 23%. Abschließend wurde ein Ingenieurmodell auf Grundlage der Sandwichtheorie entwickelt, mit dem das Last-Verformungsverhalten dieser Sandwichkonstruktion gut beschrieben werden kann. Mit dem Modell ergaben sich Abweichungen von -24% bis +12% zwischen experimentellen und theoretisch ermittelten Verformungen. Die Tragfähigkeit wurde mit einer Abweichung von 15% bis 34% unterschätzt.

A series of lateral load tests were performed on a full-scale pile cap with three different backfill conditions, namely: with no backfill present, with densely compacted clean sand in place, and with loosely compacted clean sand in place. In addition to being displaced under a static loading, the pile cap was subjected to low frequency, small displacement loading cycles from load actuators and higher frequency, small displacement, dynamic loading cycles from an eccentric mass shaker. The passive earth pressure from the backfill was found to significantly increase the load capacity of the pile cap. At a displacement of about 46 mm, the loosely and densely compacted backfills increased the total resistance of the pile cap otherwise without backfill by 50% and 245%, respectively. The maximum passive earth pressure for the densely compacted backfill occurred at a displacement of approximately 50 mm, which corresponds to a displacement to pile cap height ratio of 0.03. Contrastingly passive earth pressure for the loosely compacted backfill occurred at a displacement of approximately 40 mm. Under low and high frequency cyclic loadings, the stiffness of the pile cap system increased with the presence of the backfill material. The loosely compacted backfill generally provided double the stiffness of the no backfill case. The densely compacted backfill generally provided double the stiffness of the loosely compacted sand, thus quadrupling the stiffness of the pile cap relative to the case with no backfill present. Under low frequency cyclic loadings, the damping ratio of the pile cap system decreased with cap displacement and with increasing stiffness of backfill material. After about 20 mm of pile cap displacement, the average damping ratio was about 18% with the looser backfill and about 24% for the denser backfill. Under higher frequency cyclic loadings, the damping ratio of the pile cap system was quite variable and appeared to vary with frequency. Damping ratios appear to peak in the vicinity of the natural frequency of the pile cap system for each backfill condition. On the whole, damping ratios tend to range between 10 and 30%, with an average of about 20% for the range of frequencies and displacement amplitudes occurring during the tests. The similar amount of damping for different ranges of frequency suggests that dynamic loadings do not appreciably increase the apparent resistance of the pile cap relative to slowly applied cyclic loadings.

No description available.