Dynamic Interaction Analysis Research Articles

Vertical dynamic interactions of poroelastic soils and embedded piles considering the effects of pile-soil radial deformations

The paper presents an analytical solution for the vertical dynamic interaction analysis of a poroelastic soil layer and an embedded pile with the consideration of pile-soil radial deformations. The soil is treated a three-dimensional porous continuum and described by the Boer’s poroelastic model, while the pile is treated as a two-dimensional rod with both radial and vertical deformations of which the equation of motion is derived by the Hamilton’s variational principle. Without the introduction of potential functions, first take the volumetric strain of soil skeleton and pore fluid pressure as intermediate variables to deal with the equations of motion for the soil and then use the separation of variables to solve the equations of motion for the soil and the pile. By imposing the boundary and continuity conditions of the pile-soil system, the dynamic impedance in frequency domain and the velocity response in time domain of the pile top are obtained. The present solution is then verified by comparing with the corresponding finite element model computation results and the existing solutions. The effects of the pile-soil parameters on the dynamic characteristic of the pile-soil system are also analyzed. Some significant conclusions are drawn, which can provide useful reference for related engineering practice.

Stability enhancement of DC power systems by VSM control strategy

DC system is characterized by low inertia and weak damping, which leads to a couple of stability issues. This paper proposes a modeling method for analyzing the DC-side oscillations occurred in DC microgrid with taking multi-paralleled converters into account. A new modeling is developed for analysis of dynamic interaction between multiple power converters. Thus, it is found that dynamic interaction between multiple converters will result in the poorly-damped oscillation of DC voltage. Besides, the poorly-damped modes will aggravate the stability of DC system. To cope with this issue, a virtual synchronous machine (VSM) control approach is proposed to suppress the oscillation of DC voltage, strengthen inertia, and improve damping performance of DC microgrid. Besides, the controller tuning of the VSM has a large flexibility that it does not depend on the system parameters. Finally, the proposed conceives are demonstrated by simulations.

A scheme for switching boundary condition types in the integral static-dynamic analysis of soil-structures in Abaqus

Simulation of semi-infinite foundation is a key issue in the finite element analysis of dynamic soil-structure interactions. When the viscous-spring artificial boundary is used to simulate the radiation damping effect, the boundary condition types of the truncated foundation are different in the static and dynamic steps. It is needed to switch the displacement boundary to the traction boundary in the integral static-dynamic analysis. This paper proposes a scheme for steadily switching boundary condition types in the integral static-dynamic analysis of structures in Abaqus by means of the element birth and death technique. To verify the proposed scheme, a two-dimensional FE analysis of Pine Flat dam due to static and dynamic loads is carried out for wave motion problems of both internal and external sources. Results show that the proposed scheme can switch the boundary conditions steadily and improve the computational accuracy.

Developing multivariate time series models to examine the interrelations between police enforcement, traffic violations, and traffic crashes

Safer roads and police enforcement are closely associated since the latter directly encourages road users to improve their behavior by complying with basic traffic rules and laws. Understanding the relationships between police enforcement, driving behavior, and traffic safety is a prerequisite for optimizing enforcement strategies. However, there is a dearth of research on the contemporaneous relationships between these three parameters. Using multivariate time series techniques, this study provides an in-depth analysis of contemporaneous relationships and dynamic interactions among police enforcement, traffic violations, and traffic crashes. The amount of police patrol time per day was used as a surrogate measure for police enforcement intensity. A vector autoregressive (VAR) model was first used to examine the influences of exogenous factors including weather conditions and holidays. Based on the findings of the VAR model, a structural vector autoregressive (SVAR) model was developed to determine contemporaneous effects; the Granger causality test was employed to detect any dynamic interactions between the three parameters. The results indicated that traffic crashes and violations had weekly variation and were significantly impacted by holiday and weather conditions, while police patrol time was not impacted. A contemporaneous negative impact of police patrol time was found in traffic crashes: each 1% increase in police patrol time was associated with a 0.15% decrease in contemporaneous crash frequency. The findings from the Granger causality test demonstrated that police patrol time did not Granger-cause traffic crashes, but crashes Granger-caused police patrol time. The significant bidirectional interactions in conditional variances of police enforcement, traffic violations, and traffic crashes further confirm the necessity to analyze the three simultaneously. The findings of this study are expected to assist the relevant traffic authorities in devising policies and strategies such as optimal police patrol scheduling.

Evaluation of Anchor Penetration Depth based on Numerical Analysis for Burial Protection Method of Submarine Cables

Submarine cables are installed and operated for the stable power supply of island regions, and feature protective measures to counter marine hazard factors. With regard to the protection techniques to prevent damage to submarine cables, the method of digging and embedding the submarine ground is applied the most. However, since there are no design criteria and techniques for such protection facilities, the burial depth of the submarine ground has been calculated only qualitatively and empirically after an ocean survey is conducted. Such an imperfect method has led to assorted damages to submarine cables. Therefore, in this study, to ensure the safety of submarine cables from marine hazard factors, the three-dimensional dynamic interaction analysis model was established for the ship anchor and ground, and the penetration depth of this anchor was calculated through numerical analysis for the burial protection method. These results were compared and evaluated with the results of the full scale test for anchoring and dragging anchor. As a result, the error rate(average) of the anchor penetration depth through the numerical analysis and test was 12.2% in the ground conditions of sand, clay and multi(clay/sand) layers. This error rate was analyzed to be caused by various uncertainties in the test, such as the dynamic impact of the anchor and ground conditions, and the numerical analysis was evaluated to ensure sufficient reliability. The results of this study are expected to be useful in the burial depth calculation of the burial protection method to ensure the safety of submarine cables.

A systematic modeling approach for layered soil considering horizontal and rotational foundation vibrations

Several simplified models have been developed to simulate unbound soil for dynamic soil-structure interaction analysis in time domain. However, the existing models may have critical limitations for general applications. This study presents an approach to systematically generate lumped-parameter models with frequency-independent coefficients to represent the dynamic stiffness of rigid foundations in layered soil undergoing horizontal and rotational vibration. The components of the proposed model are determined from modularized units using a computational procedure, which simulates the coupling between the horizontal and rotational motion. This study applies the proposed model to simulate a non-uniform layered half-space and a uniform stratum on rigid rock. For surface and embedded foundations, the dynamic responses calculated by the proposed model agree well with theoretical solutions and computer program results. For embedded cylindrical foundations, the proposed model performs better and uses fewer parameters than an existing lumped-parameter model to simulate a soil layer on rock. Thus, the proposed systematic modeling approach shows a higher degree of adaptivity than traditional methods to generate simplified models for the simulation of layered soil considering coupled horizontal and rotational motion.

Analysis of the Pile-Soil Dynamic Interaction of Wharf in Marine Environment under the Impact of Earthquake

Zhou, L., 2020. Analysis of the pile-soil dynamic interaction of wharf in marine environment under the impact of earthquake. In: Gong, D.; Zhang, M., and Liu, R. (eds.), Advances in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 106, pp. 531–535. Coconut Creek (Florida), ISSN 0749-0208.The dynamic interaction of pile-soil structure is an interdisciplinary subject combining structural dynamics and soil dynamics. Under the action of an earthquake load, the soil will cause the movement of ground surface different from that of underlying bedrock. At the same time, the pile-soil structure will also affect the movement of the foundation bottom. Pile foundation is a foundation form with a long history that has many unique functions and is widely used in many fields, such as high-rise buildings, heavy-duty workshops, bridges, and offshore engineering. Pile foundation has become an important type of foundation in engineering construction and is widely used in marine terminals. The dynamic interaction of pile-soil structure in marine environment under earthquake needs to be stimulated, which will have important academic significance and practical value. In this paper, the loads and their effects on the quay structures in the marine environment are analyzed, which reflects the results of the pile-soil dynamic interaction.

Coupled dynamic analysis of low and medium speed maglev vehicle-bridge interaction using SIMPACK

The low- and medium-speed maglev vehicle generally operates on elevated bridges with a levitation gap of only 8--10 mm, which makes it very sensitive to the vehicle--bridge coupled vibration. To conduct the corresponding modeling and simulation with common dynamics tools, an equivalent processing of the levitation system is required. Using the dynamics software SIMPACK, this paper first introduces the methods of building the multi-body vehicle system, levitation control system and the elastic bridge, respectively, in the SIMPACK railway module, levitation control module and SIMBEAM elastomer module, thus providing a modeling idea for the simulation of the active levitation and operation of low- and medium-speed maglev vehicles through multi-span bridges. It then goes on to simulate and analyze the coupled vibration of a 160 km/h low- and medium-speed maglev vehicle passing through 25 m + 25 m double-span continuous bridges. The research results show that the modeling method introduced in this paper can simulate the low- and medium-speed maglev vehicle--bridge coupled vibration phenomenon, which can be affected significantly by the low-order frequency of the elastic bridge, and can also be intensified under the bridge end impact when the vehicle enters and leaves the bridge. As the running speed of the vehicle increases and the dynamic force increases, the vertical vibration amplitudes of the elastic bridge mid-span, the car body as well as the levitation frame approximate a linear fitting with the vehicle speed. The variation amplitudes of the levitation gap and of the electromagnet current approximate a quadratic fitting with the vehicle speed.

On the Characteristics of Ground Motion and the Improvement of the Input Mode of Complex Layered Sites

It is a hot research topic to perform the dynamic interaction analysis between the engineering structure and the soil by using the time-domain method. This paper studies the seismic behaviour of the layered sites and the seismic response of the structures using the viscous-spring artificial boundary theory. The artificial boundary model of viscous-spring is initially based on homogeneous foundation. For the layered site (Foundation), the traditional homogeneous model or equivalent load input mode is not suitable, which may bring great error. By introducing the changes of coefficients and phases of reflection and transmission of seismic waves at the interface between layers, an improved method of equivalent load input mode of traditional viscous-spring artificial boundary model is proposed. This new wave model can simulate the propagation law of seismic wave in layered site more accurately, which is available for the seismic performance of engineering structure under the condition of large and complex layered site. At last, the simplified homogeneous model, the equivalent load input method and the improved layered model input method are used to study the seismic response of the engineering example. It is shown that the results calculated by the three methods are different, which shows that the homogeneous foundation model and the conventional equivalent load input method of seismic wave cannot simulate the seismic force accurately, whereas the improved wave input model can better reflect the characteristic of traveling wave in layered sites.

Dynamic soil-structure interaction analyses of two important structures affected by liquefaction during the Canterbury earthquake sequence

The 2010–2011 Canterbury earthquake sequence produced significant damage in Christchurch. Much of the observed damage was related to soil liquefaction. The availability of building information, performance observations, survey data, geotechnical data, and ground motions recordings in Christchurch produced several well-documented case histories that provide insights to liquefaction-induced building settlement. Two case histories of important structures built atop fluvial soil deposits with sand and gravel layers are analyzed. One building was the third tallest building in Christchurch before the earthquakes, and the other building is an architectural landmark. Both structures were sited near the Avon River in zones of minor-to-moderate lateral spreading. Nonlinear dynamic soil-structure-interaction effective stress analyses are performed using the program FLAC with the PM4Sand constitutive model calibrated with laboratory tests or established simplified liquefaction procedures. The results show good agreement between observed and calculated responses of the ground and structure for the Canterbury earthquake sequence. Dynamic analysis identified several potential mechanisms contributing to the observed performance. Its use is encouraged to estimate shear-induced liquefaction building settlement.

Vehicle-track dynamic interaction analysis of a metro vehicle

In this paper, comparison of results between the self-programming model (considering the track flexibility) and SIMPACK model (considering only fastener support) is carried out. The wheelset vibration is more obviously for the self-programming model as the track flexibility is considered. For the traditional dynamic calculation, the SIMPACK multi-rigid-body model is acceptable. Two kinds of harmonic vibrations in the car body for a metro car, which were found in the service operations, are reproduced by using self-programming model. High tread conicity leds to the harmonic vibrations in the car body about 4.8Hz. Reducing wheel conicity can improve the bogie hunting stability, and solve this problem. Another harmonic vibration with the frequency of about 2.2Hz in the car body is caused by the constant excitation wavelength in the track, which causes vibration transmited through the primary and secondary suspensions to the carbody. To reduce this harmonic vibration, more advanced suspensions are needed.

Dynamic interaction analysis of bridges induced by a low-to-medium–speed maglev train

The structure of low-to-medium–speed maglev trains significantly differs from that of traditional wheel/rail trains, leading to significant differences between the coupling vibration mechanism of the train and bridge systems. To determine the vertical dynamic interaction of the low-to-medium–speed maglev train–bridge system, a dynamic interaction model was established and studied, based on a proportional–integral–derivative active suspension control system and modal superposition method. The simulation model was validated through bridge dynamic field tests on the Changsha low-to-medium–speed maglev commercial line. The vertical dynamic characteristics of the system were analyzed for bridges with different girder heights. Subsequently, the mechanism of the vertical resonance of the bridge induced by the maglev train was analyzed carefully. The results show that reducing the bridge rigidity increases the electromagnetic levitation force, thereby increasing the dynamic response. The low-speed resonance in the bridge is caused by the circulation loading frequency of the adjacent electromagnetic force, whereas the normal-speed resonance is induced by the self-frequency of the electromagnetic levitation force.

Finite Element Analysis Framework for Dynamic Vehicle-Bridge Interaction System Based on ABAQUS

This paper presents a unified framework for dynamic analysis of vehicle-bridge interaction (VBI) systems using a commercial finite element software suite (ABAQUS[Formula: see text]). This framework can provide bridge designers and engineering practitioners with a general platform to analyze the coupled system with high modeling efficiency and accuracy in modeling and outputting. Moreover, it has readily available nonlinear material/element models and nonlinear dynamic analysis functions for complex structures. This analysis framework was first validated with a classical VBI problem involving a sprung mass moving on a simply supported beam, whose closed-form solution is readily available. Validation for the application on complex structure was then presented with a typical 16-car Japanese high-speed train (Shinkansen) and a three-block bridge. The cars comprised car bodies, bogies and wheelsets, which were all modeled as rigid bodies and which were connected with springs and dashpots. The bridge was modeled with typical three-dimensional solid elements. Interaction between wheelsets and tracks was realized using the penalty method. Rail irregularity was also considered in the analysis. The consistency between calculated dynamic responses and field experiment data of certain pre-specified observation points validated the proposed method. Furthermore, ease in analyzing VBI problems involving nonlinear material properties and with high spatial resolutions was demonstrated with a classical cracked beam problem: a point mass moving on a simply supported cracked beam. Both linear and nonlinear crack models were employed. The former model assigned crack surfaces with a mechanical contact property and showed its accuracy in comparison to the reference model. The latter assigned a nonlinear material model in crack-prone zones and illustrated the potential applicability to dynamic crack propagation simulation in VBI problems. The present framework was further applied to seismic response analysis of a train-bridge interaction system involving material nonlinearity and separation between track and wheel under a strong earthquake.

Effect of raft thickness and soil modulus on frequency and amplitude of building frame

The paper presents the limited study on the evaluation of the response of the dynamic soil structure interaction analysis of a two storeyed building frame resting on raft foundation using finite element method. The components of the building frame such as beams, columns and slabs along with the raft are modeled using 20 noded isoparametric continuum elements. The soil surrounding the foundation is modeled in the simplified manner using discrete independent springs. The interface of soil and raft has been accounted for by incorporating 16 node interface elements in the modeling. Further, the components of the superstructure and substructure are treated to behave in the linear elastic manner whereas the soil media is idealized to behave in the non-linear manner. The effect of raft thickness and soil modulus is evaluated on the dynamic response of the frame. The response is considered in terms of the frequency and amplitude. The result indicates that the dynamic loading and SSI has a considerable effect on the response of the structure.

Nonlinear dynamic soil structure interaction in adjacent basement

This research was conducted to analyze the lateral dynamic pressure distribution on the basement walls and amplification of earthquake motion on the surface using the finite element method Midas GTS-NX. Dynamic soil-structure interaction analysis was carried out by using a sensitivity program to influence soil conditions, earthquake acceleration in bedrock, basement depth, bedrock depth and stiffness of the basement structure with a distance between basements of 15,0 m. From this study, the lateral pressure distribution of the dynamic soil reaches the maximum at the base of the basement with an increase in pressure that is almost linear in soft and nonlinear soil conditions in medium and hard soil conditions. The greatest increase in gradient occurs at a depth of four per five basement walls measured from the surface to the bottom of the basement. The analysis shows that the dynamic lateral pressure distribution has a maximum value at the top end of the basement and tends to shrink to the bottom of the basement.

Boundary element analysis of dynamic interaction of anisotropic elastic half-space and structure under impact load

In this paper, a direct boundary element formulation for numerical modelling of threedimensional dynamic soil-structure interaction is briefly described. Formulation is applicable to problems involving isotropic and anisotropic elastic materials. It is based on the Laplace domain regularized boundary integral equations for the displacements under assumption of vanishing initial conditions and zero body forces. Mixed boundary elements are employed for the spatial discretization of the boundary integral equations. Subdomain technique is used to tackle problems involving piecewise homogeneous material properties. The described formulation is employed for the boundary element analysis of dynamic soil-structure interaction problem involving a structure which contains a cavity with a complex geometrical form. Soil is represented by a transversely isotropic elastic half-space. Effect of material anisotropy of half-space on the transient response of the embedded structure is assessed. It is observed that the shear modulus anisotropy have substantial impact on the displacements response. Influence of the Young’s modulus in the plane of isotropy is lesser but still pronounced.

Dynamic soil-structure interaction analyses considering directionality effects

The paper investigates directionality effects of ground motions in the context of dynamic soil-structure interaction (DSSI) analyses. The problem addressed corresponds to a nonlinear soil deposit, overlaying firm ground, where the input motion was derived from an acceleration time history recorded at a rock outcrop. A simplified procedure is proposed to incorporate directionality effects. The main objective is to identify in advance the incidence angle producing the maximum response of a structure for a given earthquake. Results from the simplified procedure were evaluated by comparison with what is called here the complete rotational approach, where the behaviour of the structure, as a function of the incidence angle of the input motion, is derived through a large number of nonlinear dynamic soil-structure interaction analyses. The obtained results show the importance of considering directionality effects in DSSI analyses. The maximum response of the system was reasonably captured with the simplified approach.

Evaluation of Winkler Model and Pasternak Model for Dynamic Soil-Structure Interaction Analysis of Structures Partially Embedded in Soils

AbstractThis paper reports a comprehensive study including detailed experimental, theoretical, and numerical analyses to evaluate the performance of two predominant soil-structure interaction model...

Liquefaction-induced settlements of residential buildings subjected to induced earthquakes

The paper evaluates the dynamic performance of existing residential houses affected by gas-extraction-induced earthquakes in an area of low tectonic seismicity where structures have not been designed against earthquake loading. The foundation consists of narrow spread footings (width, B < 0.7 m), while the seismic demand is characterized by low intensity. Nonlinear, effective stress, fully coupled, dynamic soil-structure interaction analyses were performed to develop estimates of liquefaction-induced settlements for buildings on narrow spread footings, founded in a range of soil conditions, with ground motions and structural characteristics that are typically encountered in the study area. The results verify patterns observed in recent studies for slab foundations and shed light on new mechanisms. For the low magnitude earthquakes considered in this study, the total foundation settlements were found to be relatively limited, although simplified liquefaction triggering calculations would sometimes predict low factors of safety against liquefaction. A simplified equation was developed from regression of the numerical analyses results to derive estimates of liquefaction-induced settlements for residential buildings that was adopted in the latest update of the relevant seismic building code.

Ground Improvement Design and Construction for Seattle's Elliott Bay Seawall Replacement and Retrofit

The Elliott Bay Seawall in Seattle, Washington, was constructed in the early 1900s over soft/loose non-engineered and liquefaction susceptible fill, estuary, and beach deposits. The fill includes wood from historic waterfront sawmills and debris from the 1889 Great Seattle Fire. After the 2001 Nisqually earthquake, an evaluation of the seawall condition and seismic vulnerability determined that it had undergone significant deterioration and was susceptible to collapse for a 100-year earthquake. This evaluation led to design and replacement/retrofit of 1,130 meters (3,700 feet) of seawall. The new seawall includes an improved soil mass constructed of a cellular arrangement of jet-grout columns that supports a seawall superstructure and provides all seismic lateral restraint. The improved soil mass seismic performance criteria are based on allowable seawall displacement for three earthquake ground motion levels. Final improved soil mass design utilized non-linear dynamic soil-structure interaction analyses. To meet performance criteria, improved soil mass widths range between 7.9 and 18.3 meters (26 and 60 feet), ground improvement area replacement ranges between 50 and 64 percent, and jet-grout soil-cement unconfined compressive strength ranges between 0.86 and 2.76 MPa (125 and 400 psi), depending on the soil type. Improved soil mass construction issues included equipment selection, limited space, spoils handling, wood debris, and obstructions (e.g., buried utilities, piles, and temporary shoring). Lessons learned included: (1) jet grouting was the best construction method given the utilities and thousands of piles beneath the site, (2) early obstructions identification and contingency plans are critical to maintain production, and (3) an understanding of space requirements for all construction activities is required for safe and productive working conditions.