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Showing 24 results for Interaction

S. Mohammadi, A. Bebamzadeh,
Volume 4, Issue 4 (12-2006)

Explosion has always been regarded as one of the most complicated engineering problems. As a result, many engineers have preferred rather simplified empirical approaches in comparison to extremely complex deterministic analyses. In this paper, however, a numerical simulation based on the combined finite/discrete element methodology is presented for analyzing the dynamic behavior of fracturing rock masses in blasting. A finite element discretization of discrete elements allows for complex shapes of fully deformable discrete elements with geometric and material nonlinearities to be considered. Only a Rankine strain softening plasticity model is employed, which is suitable for rock and other brittle materials. Creation of new lines/edges/bodies from fracturing and fragmentation of original objects is systematically considered in the proposed gas-solid interaction flow model. An equation of state is adopted to inexpensively calculate the pressure of the detonation gas in closed form. The model employed for the flow of detonation gas has resulted in a logical algorithmic procedure for the evaluation of spatial distribution of the pressure of detonation gas, work done by the expanding gas and the total mass of the detonation gas as functions of time indicating the ability of model to respond to changes in both the mass of explosive charge and the size of the solid block undergoing fracture. Rock blasting and demolition problems are amongst the engineering applications that are expected to benefit directly from the present development. The results of this study may also be used to provide some numerical based reliable solutions for the complex analysis of structures subjected to explosive loadings.
S. N. Moghaddas Tafreshi,
Volume 6, Issue 4 (12-2008)

This paper presents the numerical analysis of seismic soil-pile-superstructure interaction in soft clay using free-field soil analysis and beam on Winkler foundation approach. This model is developed to compute the nonlinear response of single piles under seismic loads, based on one-dimensional finite element formulation. The parameters of the proposed model are calibrated by fitting the experimental data of largescale seismic soil-pile-structure tests which were conducted on shaking table in UC Berkeley. A comparative evaluation of single piles shows that the results obtained from the proposed procedure are in good agreement with the experimental results.
M.r. Abdi, S. A. Sadrnejad, M.a. Arjomand,
Volume 7, Issue 4 (12-2009)

Large size direct shear tests (i.e.300 x 300mm) were conducted to investigate the interaction between clay reinforced with geogrids embedded in thin layers of sand. Test results for the clay, sand, clay-sand, clay-geogrid, sandgeogrid and clay-sand-geogrid are discussed. Thin layers of sand including 4, 6, 8, 10, 12 and 14mm were used to increase the interaction between the clay and the geogrids. Effects of sand layer thickness, normal pressure and transverse geogrid members were studied. All tests were conducted on saturated clay under unconsolidated-undrained (UU) conditions. Test results indicate that provision of thin layers of high strength sand on both sides of the geogrid is very effective in improving the strength and deformation behaviour of reinforced clay under UU loading conditions. Using geogrids embedded in thin layers of sand not only can improve performance of clay backfills but also it can provide drainage paths preventing pore water pressure generations. For the soil, geogrid and the normal pressures used, an optimum sand layer thickness of 10mm was determined which proved to be independent of the magnitude of the normal pressure used. Effect of sand layers combined with the geogrid reinforcement increased with increase in normal pressures. The improvement was more pronounced at higher normal pressures. Total shear resistance provided by the geogrids with transverse members removed was approximately 10% lower than shear resistance of geogrids with transverse members.
F. Messaoud, M. S. Nouaouria,
Volume 8, Issue 1 (3-2010)

This paper presents a description of the equipment, testing procedure, and methodology to obtain ground

mechanical parameters. The p-y curves for laterally loaded piles are developed. Methods for the development of p-y

curves from pressure meter and dilatometer (DMT) test are described. P-y curves are used in the analysis to represent

lateral soil-pile interaction. The pressure meter offers an almost ideal in-situ modeling tool for determining directly

the p-y curves for the design of deep foundations. As the pressure meter can be driven into the soil, the results can be

used to model a displacement pile. DMT tests were performed for comparisons with PPMT tests. Correlations were

developed between the PPMT and DMT results, indicating a consistency in soil parameters values. Comparisons

between PPMT and DMT p-y curves were developed based on the ultimate soil resistance, the slope of the initial

portion of the curves, and the shape of the curves. The initial slope shows a good agreement between PPMT and DMT

results. The predicted DMT and PPMT ultimate loads are not similar, while the predicted PPMT and DMT deflections

within the elastic range are identical.

S.m. Moosavi, M.k. Jafari , M. Kamalian, A. Shafiee ,
Volume 8, Issue 2 (6-2010)

Ground differential movements due to faulting have been observed to cause damage to engineered structures

and facilities. Although surface fault rupture is not a new problem, there are only a few building codes in the world

containing some type of provisions for reducing the risks. Fault setbacks or avoidance of construction in the proximity

to seismically active faults, are usually supposed as the first priority. In this paper, based on some 1-g physical

modelling tests, clear perspectives of surface fault rupture propagation and its interaction with shallow rigid

foundations are presented. It is observed that the surface fault rupture could be diverted by massive structures seated

on thick soil deposits. Where possible the fault has been deviated by the presence of the rigid foundation, which

remained undisturbed on the footwall. It is shown that the setback provision does not give generally enough assurance

that future faulting would not threaten the existing structures.

R. Attarnejad, F. Kalateh,
Volume 10, Issue 1 (3-2012)

This paper describes a numerical model and its finite element implementation that used to compute the cavitation effects on

seismic behavior of concrete dam and reservoir systems. The system is composed of two sub-systems, namely, the reservoir and

the dam. The water is considered as bilinear compressible and inviscid and the equation of motion of fluid domain is expressed

in terms of the pressure variable alone. A bilinear state equation is used to model the pressure–density relationship of a cavitated

fluid. A standard displacement finite element formulation is used for the structure. The Structural damping of the dam material

and the radiation damping of the water and damping from foundation soil and banks have been incorporated in the analysis. The

solution of the coupled system is accomplished by solving the two sub-systems separately with the interaction effects at the damreservoir

interface enforced by a developed iterative scheme. The developed method is validated by testing it against problem for

which, there is existing solution and the effects of cavitation on dynamic response of Konya gravity dam and Morrow Point arch

dam subjected to the first 6 s of the May 1940 El-Centro, California earthquake, is considered. Obtained results show that impact

forces caused by cavitation have a small effect on the dynamic response of dam-reservoir system.

A. A. Maghsoudi, H. Akbarzadeh Bengar,
Volume 10, Issue 4 (12-2012)

In order to lighten the prestressed concrete solid members, nowadays, it is possible to make use of the advantage of HPC (fcchr('39')>60

MPa) as well as replacing the solid section with a PSC thin-walled section for certain members such as circular and box columns.

Using the strength theory of ACI, a numerical procedure along with a computer program was developed for the analysis of such

sections subjected to axial compression or tension load and bending moments. The program solves for all possible variables such

as, concrete compressive strength (fcchr('39')= 60-100 MPa), type of prestressed steel, concrete cover, ratio of wall thickness to the section

dimensions and the PS steel arrangements to satisfy the given loading cases, thus leading to an optimal cost solution. However,

since the cross section is thin-walled circular or box and the PS steel is located at discrete points along the periphery of a circle

or rectangle, the equations of equilibrium are complex for hand computations (especially for circular section) but suitable for

computer program. So, by use of MATLAB software the interaction diagrams were also drawn for the analysis of such sections

for all mentioned variables. The use of prestressed thin-walled column diagrams is a safe and easy tool for the analysis of such

columns. Finally, the accuracy of the proposed method is demonstrated by comparing its results to those of the available

experimental values and is indicate that the proposed method predict very well the capacity of prestressed thin-walled column.

Y. L. Luo,
Volume 11, Issue 1 (5-2013)

The occurrence of piping failures in earth structures demonstrates the urgency and importance of studying piping. With this

intention, a new piping model was developed in the framework of continuum mixture theory. Assuming that porous media are

comprised of solid skeleton phase, fluid phase and fluidized fine particles phase, the fluidized fine particles phase is considered

to be a special solute migrating with the fluid phase. The three phases interact while being constrained by the mass conservation

equations of the three phases, and a sink term was introduced into the mass conservation equation of the solid skeleton phase to

describe the erosion of fluidized fine particles, then a new continuum fluid-particle coupled piping model was established and

validated. The validation indicates that the proposed model can predict the piping development of complicated structures under

complex boundary and flow conditions, and reflect the dynamic changes of porosity, permeability and pore pressure in the

evolution of piping.

A. Ghanbari, E. Hoomaan, M. Mojallal,
Volume 11, Issue 1 (5-2013)

For calculating the natural frequency of structures such as buildings, chimneys, bridges and silos appropriate analytical

formulas exist. However, in the case of retaining walls undergoing the soil pressure at one side, calculating the natural frequency

is not a straightforward task and requires the effects of soil-structure interactions to be considered. By modeling the soil as series

of linear springs, a new formulation is presented in this article, to calculate the natural frequency of retaining walls. This formula

considers the vertical cross sectional width change, and hence, enables us to calculating the natural frequency of retaining walls

with different types of backfill. The geometrical properties of the retaining walls and its bending rigidity together with the soil’s

modulus of elasticity and its Poisson’s ratio are the most important parameters to calculate. A comparison of the results for

retaining walls with constant cross section obtained from the suggested method with those of the software analyses was carried

out and good agreement was detected. A second comparison of the results with those of other researchers revealed that the natural

frequency of flexible retaining wall is an upper bound for natural frequency of rigid walls. The Selected shape function is also

very close to the real shape mode.

N. Abedimahzoon, A. Lashteh Neshaei,
Volume 11, Issue 4 (12-2013)

In this paper, a new approach is presented for estimating the vertical and horizontal distribution of undertow in the surf zone for reflective beaches. The present model is a modification of the original model presented by Okayasu et al., (1990) for natural, non-reflective beaches to include the effect of partially reflected waves. The nonlinearity of waves, wave-current interaction and nonlinear mass drift of the incident wave are also included in the present model. The results of experimental investigation and model development show that existence of reflective conditions on beaches results in a reduction in the magnitude of undertow and modifies its distribution across the beach profile. Comparison of the results by those obtained from the experiments clearly indicates that by taking the nonlinearity and wave-current interaction, the predictions of undertow in the surf zone are much improved. In particular, due to the effect of turbulence induced by wave breaking for nonlinear waves, the predicted results show more consistence with the measurements.
H. Shakib, Gh. R. Atefatdoost,
Volume 12, Issue 1 (3-2014)

An approach was formulated for the nonlinear analysis of three-dimensional dynamic soil-structure interaction (SSI) of asymmetric buildings in time domain in order to evaluate the seismic response behavior of torsionally coupled wall-type buildings. The asymmetric building was idealized as a single-storey three-dimensional system resting on different soil conditions. The soil beneath the superstructure was modeled as nonlinear solid element. As the stiffness of the reinforced concrete flexural wall is a strength dependent parameter, a method for strength distribution among the lateral force resisting elements was considered. The response of soil-structure interaction of the system under the lateral component of El Centro 1940 earthquake record was evaluated and the effect of base flexibility on the response behavior of the system was verified. The results indicated that the base flexibility decreased the torsional response of asymmetric building so that this effect for soft soil was maximum. On the other hand, the torsional effects can be minimized by using a strength distribution, when the centre of both strength CV and rigidity CR is located on the opposite side of the centre of mass CM, and SSI has no effect on this criterion.
P. Vahabkashi, A. R. Rahai, A. Amirshahkarami,
Volume 12, Issue 1 (3-2014)

Piles or drilled shafts used in bridge foundation, waterfronts, and high rise buildings are generally subjected to lateral loads. In order to study the effect of concrete pile geometry on the structural behavior in layered soils, several models with different shapes and dimensions for piles and different properties for two soil layers with variable thickness were selected and analyzed using the finite difference method. The performance of piles situated in layered granular soil with different compaction and thicknesses were studied in two cycles of lateral loading and unloading. The applied finite difference procedure is also validated based on experimental and published results. The pile head displacement of different models due to their overall deformation and rotation were calculated under maximum loading. For a comparison of pile head displacement due to their overall deformation and rotation in different models, the "performance index” is defined as the ratio of “displacement due to deformation” to the “total displacement”.
Mohammad Amin Hariri Ardebili, Hasan Mirzabozorg, Reza Kianoush,
Volume 12, Issue 2 (6-2014)

In the present study, the application of Endurance Time Analysis (ETA) method is investigated on seismic analysis of a high arch dam. In this method the coupled system is excited using the predesigned intensifying acceleration functions instead of the real ground motions. Finite element model of an arch dam considering the dam-rock-water interaction effects was developed in which the concrete and rock were assumed to have linear elastic behavior. The effect of the large displacement in dam body was considered in numerical model using co-rotational approach. The coupled system was analyzed by conventional Time History Analysis (THA) method in various seismic performance levels and the results were compared with those obtained from ETA at the equivalent target time. It was found that ETA method provides the close results to THA with acceptable accuracy while it reduces the total time of the analyses considerably.
Amir Hossein Jafarieh, Mohammad Ali Ghannad,
Volume 12, Issue 2 (6-2014)

It is well-known that the behavior of soil-structure systems can be well described using a limited number of non-dimensional parameters. This is the outcome of researches based on the premise that the foundation is bonded to the ground. Here, it is shown the concept can be extended to systems with foundation uplift. A set of non-dimensional parameters are introduced which controls the main features of uplifting systems. The effect of foundation uplift on response of soil-structure systems are investigated parametrically through time history analysis for a wide range of systems subjected to ground motions recorded on different soil types. In particular, the effects of uplift on displacement ratio, defined as the ratio of maximum displacement of the uplifting system to that of the elastic system without uplifting and drift ratio, defined as the ratio of maximum drift of the structure as a part of uplifting soil-structure system to that of the elastic system without uplifting, are investigated. It is observed that in general foundation uplift reduces the drift response of structures, which in turn, results in lower base shear. The reduction reaches about 35 percent for slender structures located on relatively soft soils subjected to strong ground motions. Simplified expressions are suggested to estimate this reduction in the base shear.
L. Kalani Sarokolayi, B. Navayi Neya, Javad Vaseghi Amiri,
Volume 13, Issue 1 (3-2015)

This study focuses on non-linear seismic response of a concrete gravity dam subjected to translational and rotational correlated components of ground motions including dam-reservoir interaction. For this purpose rotational components of ground motion is generated using Hong Non Lee improved method based on corresponding available translational components. The 2D seismic behavior of the dam concrete is taken into account using nonlinear fracture mechanics based on the smeared- crack concepts and the dam-reservoir system are modeled using Lagrangian-Lagrangian approach in finite element method. Based on presented formulation, Pine Flat concrete gravity dam is analyzed for different cases and results show that the rotational component of ground motion can increase or decrease the maximum horizontal and vertical displacements of dam crest. These results are dependent on the frequency of dam-reservoir system and predominant frequencies of translational and rotational components of ground motion.
R. Tarinejad, S. Pirboudaghi,
Volume 13, Issue 2 (6-2015)

It is well-known that dam-reservoir interaction has significant effects on the response of dams to the earthquakes. This phenomenon should be considered more exactly in the seismic design of dams with a rational and reliable dynamic analysis method. In this research, seismic analysis of the dam-reservoir is studied as a wave propagation problem by using Legendre Spectral element method (SEM). The special FEM and SEM codes are developed to carry out the seismic analysis of the dam-reservoir interaction system. The results of both SEM and FEM models are compared considering the accuracy and the time consumption of the analysis. Attractive spectral convergence of SEM is obtained either by increasing the degree of the polynomials in the reservoir or by the number of elements of dam. It is shown that all boundary conditions of the reservoir domain in the SEM are evaluated by the exact diagonal matrices. The SEM leads to the diagonal mass matrix for both dam and reservoir domains. The stiffness matrices obtained from the SEM are more sparse than the corresponding stiffness matrices in the FEM consequently the SEM needs a significant less time consumption of the analysis.

M.a. Rahgozar,
Volume 13, Issue 3 (12-2015)

The interactive effects of adjacent buildings on their seismic performance are not frequently considered in seismic design. The adjacent buildings, however, are interrelated through the soil during seismic ground motions. The seismic energy is redistributed in the neighboring buildings through multiple structure-soil-structure interactions (SSSI). For example, in an area congested with many nearby tall and/or heavy buildings, accounting for the proximity effects of the adjacent buildings is very important. To solve the problem of SSSI successfully, researchers indicate two main research areas where need the most attention: 1) accounting for soil nonlinearity in an efficient way, and 2) spatial analysis of full 3D soil-structure models. In the present study, three-dimensional finite element models of tall buildings on different flexible foundation soils are used to evaluate the extent of cross interaction of adjacent buildings. Soil nonlinearity under cyclic loading is accounted for by Equivalent Linear Method (ELM) as to conduct large parametric studies in the field of seismic soil-structure interaction, the application of ELM is preferred over other alternatives (such as application of complicated constitutive soil models) due to the efficiency and reliability of its results. 15 and 30 story steel structures with pile foundations on two sandy and clayey sites are designed according to modern codes and then subjected to several actual earthquake records scaled to represent the seismicity of the building sites. Results show the cross interaction of adjacent buildings on flexible soils, depending on their proximity, increases dynamic displacements of buildings and reduces their base shears. 

M. Davoodi, M. Sadjadi,
Volume 13, Issue 3 (12-2015)

The distinctive characteristics of near-field earthquake records can lead to different structural responses from those experienced in far-field ones. Furthermore, soil-structure interaction (SSI) can have a crucial influence on the seismic response of structures founded on soft soils however, in most of the time has been neglected nonchalantly. This paper addresses the effects of near-field versus far-field earthquakes on the seismic response of single degree of freedom (SDOF) system with considering SSI. A total 71 records were selected in which near-field ground motions have been classified into two categories: first, records with a strong velocity pulse, (i.e. forward-directivity) second, records with a residual ground displacement (i.e. fling-step). Findings from the study reveal that pulse-type near-field records generally produce greater seismic responses than far-field motions especially at high structure-to-soil stiffness ratios. Moreover, the importance of considering SSI effects in design of structures is investigated through an example. Finally, parametric study between Peak Ground Velocity to Peak Ground Acceleration ratio (PGV/PGA) of pulse-like ground motions and maximum relative displacement indicate that with increase in structure-to-soil stiffness ratios, earthquakes with higher PGV/PGA ratio produce greater responses.

Mahmood Reza Abdi, Hamed Mirzaeifar,
Volume 14, Issue 4 (6-2016)

Abstract To meet construction demands, reinforcement and stabilization methods have been widely used to improve properties and mechanical behavior of clays. Although cement stabilization increases soil strength, at the same time reduces ductility which is of paramount importance in roads, landfill covers, etc. In current study, kaolinite was stabilized with 1, 3 and 5% cement and mixed with 0.05, 0.15, 0.25 and 0.35% polypropylene fibers to increase ductility. Samples were cured at 35°C for 1, 7 and 28 days and subjected to unconfined compression tests. Results showed that inclusion of discrete fibers to uncemented and cemented kaolinite reduced stiffness and the loss of post-peak strength and changed brittle behavior of cemented samples to a more ductile behavior. Cement and fiber contents as well as curing period were found to be the most influential factors and fiber – soil interaction was influenced by binding materials.

Dongdong Zhang,
Volume 14, Issue 8 (12-2016)

This paper compares the seismic load of a 5MW wind turbine supported by a 100-m-high prestressed concrete tower calculated via time history analysis and response spectrum analysis using elastic acceleration spectrum provided by the China Aseismic Code for Buildings. With 5% damping ratio, the fixed-based Multi-degree of freedom model and Finite element model considering soil structure interaction are used for response spectrum analysis and time history analysis, respectively. The results indicated that the seismic load calculated by response spectrum analysis is significantly larger than the results associated with the time history analysis method. It implies that the seismic load determined from common building code procedures along with other loads for wind turbine foundation design is too conservative. Within this paper, the effects of damping ratio, horizontal acceleration amplitude, spring stiffness and damping coefficient of foundation on the seismic load of the prestressed concrete wind turbine tower are discussed. It is shown that the seismic load with mode damping ratio for the prestressed concrete wind turbine tower is not significant when compared with traditional tubular steel designs. The maximum moment demand at the base of the tower may be controlled by earthquake loading as the seismic fortification intensity lever is more than seven. The foundation spring stiffness has a immensely impact on the base bending moment and the natural frequency. Finally, seismic load should be considered in more detail when designing wind turbines that are supported by concrete towers, particularly for turbine’s over 100-m tall and located in seismically active zones.

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