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Showing 19 results for Bearing Capacity

H. Ghiassian,
Volume 2, Issue 1 (3-2004)
Abstract

A study of bearing capacity and compressibility characteristics of cohesive soil, reinforced by geogrid and supporting square footing loads has been conducted. The lack of adequate frictional resistance between clay and reinforcing elements was compensated by using a thin sand layer (lens) encapsulating the geogrid sheet. In this way, tensile forces induced in the geogrid were transferred to the bulk clay medium through the sand particles and soil reinforcement was improved Experiments were conduced on two sets of specimens, one set of 1 x 1 x 1 m dimension and the footing size of 19 x 19 cm (series A), and the other set of 0.15 x 0.15 x 0.15 m dimension and the footing size of 3.7 x 3.7 cm (series B). The loading systems for the above specimens were stress controlled and strain controlled respectively. All specimens were saturated and presumably loaded under an undrained condition. The results qualitatively confirmed the effectiveness of the sand lens in improving the bearing capacity and settlement characteristics of the model footing. In series A, the maximum increase in the bearing capacity due to the presence of the sand lens was 17% whereas in series B, the amount of increase was 24%. The percentage reductions in the settlement for these results were 30% and 46% respectively.
A.a. Maghsoudi, H. Akbarzadeh Bengar,
Volume 5, Issue 2 (6-2007)
Abstract

Limit to the tension reinforcement ratio ( ρ) in flexural high strength reinforced concrete (HSRC) members is based on the requirement that tension failure as sufficient rotation capacity are ensured at ultimate limit state. However, the provisions for the total amount of longitudinal reinforcement ratio ( ρ and ρ’) are not associated with any rational derivation. In this paper, a quantitative measure to evaluate an upper limit to the compression reinforcement ratio ρBmax of flexural HSRC members is proposed. The quantitative criterion to ρBmax can be derived from i) steel congestion and ii) considerations that are related to the diagonal compression bearing capacity of the members. In this paper it is shown that, when shear loading is dominant, the limit to is set by the diagonal compression criterion. Parameters that affect this limit are deeply investigated and the expressions were derived for different end conditions, to provide an additional tool for a better design and assessment of the flexural capacity of HSRC members.
A.a. Maghsoudi, H. Akbarzadeh Bengar,
Volume 7, Issue 1 (3-2009)
Abstract

Limit to the tension reinforcement ratio in flexural high strength reinforced concrete (HSRC) members is

based on the requirement that tension failure as sufficient rotation capacity are ensured at ultimate limit state.

However, the provisions for the total amount of longitudinal reinforcement ratio ( and ) are not associated with

any rational derivation. In this paper, a quantitative measure to evaluate an upper limit to the compression

reinforcement ratio of flexural HSRC members is proposed. The quantitative criterion to can be derived

from i) steel congestion and ii) considerations that are related to the diagonal compression bearing capacity of the

members. In this paper it is shown that, when shear loading is dominant, the limit to is set by the diagonal

compression criterion. Parameters that affect this limit are deeply investigated and the expressions were derived for

different end conditions, to provide an additional tool for a better design and assessment of the flexural capacity of

HSRC members.


S.a. Naeini, R. Ziaie_moayed,
Volume 7, Issue 2 (6-2009)
Abstract

In recent years, soil reinforcement is considered of great importance in many different civil projects. One of the most significant applications of soil reinforcement is in road construction. Sub grade soil and its properties are very important in the design of road pavement structure. Its main function is to give adequate support to the pavement from beneath. Therefore, it should have a sufficient load carrying capacity. The use of geosynthetics in road and airfield construction has shown the potential to increase the soil bearing capacity. One category of geosynthetics to particular, geogrid, has gained increasing acceptance in road construction. A geogrid is a geosynthetic material consisting of connected parallel sets of tensile ribs with apertures of sufficient size to allow strike-through of surrounding soil, stone, or other geotechnical material. Geogrid reinforcement of sub grade soil is achieved through the increase of frictional interaction between the soil and the reinforcement. Geogrid have been successfully used to provide a construction platform over subgrades. In this application, the geogrid improves the ability to obtain compaction in overlying aggregates, while reducing the amount of material required be removing and replacing. Relative agreement exists that substantial benefits can be achieved from the inclusion of geogrids within the pavement systems however, the quantity of the improvement is in relative disagreement. This paper presents the effects of plasticity index and also reinforcing of soft clay on CBR values. Three samples of clay with different plasticity index (PI) values are selected and tested without reinforcement. Then by placing one and two layer of geogrid at certain depth within sample height, the effects of reinforcement and PI on CBR values are investigated in both soaked and unsoaked conditions. The results shows that as the PI increase the CBR value decreases and reinforcing clay with geogrid will increase the CBR value.
A. R. Majidi, A.a. Mirghasemi, M. Arabshahi,
Volume 9, Issue 4 (12-2011)
Abstract

In the current study, an effort is made to determine three dimensional bearing capacity of rectangular foundations using Discrete

Element Method. The soil mass is modeled as discrete blocks connected with Winkler springs. Different factors affect the geometry

of failure surface. Six independent angles are used to define the failure surface. By trial and error, the optimum shape of failure

surface beneath the foundation can be found. The paper includes the derivation of the governing equations for this DEM based

formulation in three dimensional state as well as parametric sensitivity analyses and comparison with other methods. Moreover,

using the current method, bearing capacity coefficients are presented for various friction angles and foundation aspect ratios.


M. Jahanandish, M. Veiskarami, A. Ghahramani,
Volume 9, Issue 4 (12-2011)
Abstract

Foundations behavior is affected by soil behavior which can vary from dilative to contractive depending on the stress level,

particularly in dense frictional soils. The Zero Extension Lines (ZEL) method has been generally developed to predict the

foundations behavior. Knowledge of soil behavior enables the ZEL method to predict the general and local shear failure modes.

In this paper, a relatively simple work hardening/softening soil constitutive model is developed to represent dense frictional soils

behavior under different stress levels. This model is based on the accumulation of the plastic work during a simple direct shear

test and its relationship to stress ratio to establish the hardening law. Verifications have been made for the developed soil model.

The model is then implemented into the ZEL method to theoretically investigate the bearing capacity and load-displacement

behavior of foundations over dense frictional soils. Utilization of this model enables the ZEL method to capture different modes

of failure depending on the foundation size. A numerical study on foundations behavior was performed showing the ability of the

presented approach in capturing both failure modes.


J. Nazari Afshar, M. Ghazavi,
Volume 12, Issue 1 (1-2014)
Abstract

The Stone-column is a useful method for increasing the bearing capacity and reducing settlement of foundation soil. The prediction of accurate ultimate bearing capacity of stone columns is very important in soil improvement techniques. Bulging failure mechanism usually controls the failure mechanism. In this paper, an imaginary retaining wall is used such that it stretches vertically from the stone column edge. A simple analytical method is introduced for estimation of the ultimate bearing capacity of the stone column using Coulomb lateral earth pressure theory. Presented method needs conventional Mohr-coloumb shear strength parameters of the stone column material and the native soil for estimation the ultimate bearing capacity of stone column. The validity of the developed method has been verified using finite element method and test data. Parametric studies have been carried out and effects of contributing parameters such as stone column diameter, column spacing, and the internal friction angle of the stone column material on the ultimate bearing capacity have been investigated.
A. Eslami, I. Tajvidi, M. Karimpour-Fard,
Volume 12, Issue 1 (1-2014)
Abstract

Three common approaches to determine the axial pile capacity based on static analysis and in-situ tests are presented, compared and evaluated. The Unified Pile Design (UPD), American Petroleum Institute (API) and a SPT based methods were chosen to be validated. The API is a common method to estimate the axial bearing capacity of piles in marine environments, where as the others are currently used by geotechnical engineers. Seventy pile load test records performed in the northern bank of Persian Gulf with SPT profile have been compiled for methods evaluation. In all cases, pile capacities were measured using full scale static compression and/or pull out loading tests. As the loading tests in some cases were in the format of proof test without reaching the plunging or ultimate bearing capacity, for interpretation the results, offset limit load criteria was employed. Three statistical and probability based approaches in the form of a systematic ranking, called Rank Index, RI, were utilized to evaluate the performance of predictive methods. Wasted Capacity Index (WCI) concept was also applied to validate the efficiency of current methods. The evaluations revealed that among these three predictive methods, the UPD is more accurate and cost effective than the others.
H. Shahnazari, M. A. Shahin, M. A. Tutunchian,
Volume 12, Issue 1 (1-2014)
Abstract

Due to the heterogeneous nature of granular soils and the involvement of many effective parameters in the geotechnical behavior of soil-foundation systems, the accurate prediction of shallow foundation settlements on cohesionless soils is a complex engineering problem. In this study, three new evolutionary-based techniques, including evolutionary polynomial regression (EPR), classical genetic programming (GP), and gene expression programming (GEP), are utilized to obtain more accurate predictive settlement models. The models are developed using a large databank of standard penetration test (SPT)-based case histories. The values obtained from the new models are compared with those of the most precise models that have been previously proposed by researchers. The results show that the new EPR and GP-based models are able to predict the foundation settlement on cohesionless soils under the described conditions with R2 values higher than 87%. The artificial neural networks (ANNs) and genetic programming (GP)-based models obtained from the literature, have R2 values of about 85% and 83%, respectively which are higher than 80% for the GEP-based model. A subsequent comprehensive parametric study is further carried out to evaluate the sensitivity of the foundation settlement to the effective input parameters. The comparison results prove that the new EPR and GP-based models are the most accurate models. In this study, the feasibility of the EPR, GP and GEP approaches in finding solutions for highly nonlinear problems such as settlement of shallow foundations on granular soils is also clearly illustrated. The developed models are quite simple and straightforward and can be used reliably for routine design practice.
M. Haghbin,
Volume 12, Issue 4 (12-2014)
Abstract

This research examines the behavior of soil-reinforced piles and applied loads based on the analytical method and by using the numerical results of FLAC3D software for comparison with the analytical results. The analysis was based on a method called virtual retaining wall, the following into consideration: an imaginary retaining wall that passes the footing edge the bearing capacity of footing on reinforced soil with piles, which was determined by applying equilibrium between active and passive forces on virtual wall and a pile row that exists beneath the shallow foundation. To calculate the lateral pile resistance here, an analytical equation was then required. The main objective of this paper is to determine the percentage of applied load on pile. Similarly, the effect of adding pile in various positions relative to the present footing (underpinning) was studied in this research. The various parameters of this study included pile length, vertical distance of pile head to shallow footing, pile distance to center of footing and location of the pile. Finally, the findings were compared with the numerical results of FLAC3D and the formerly presented experimental results. Results show that the analytical method, while being close to other methods is more conservative.


A. Saeedi Azizkandi, M.h. Baziar, H. Rasouli, M. Modarresi, H. Shahnazari,
Volume 13, Issue 2 (6-2015)
Abstract

In present research, 17 centrifuge tests have been conducted to study the effect of various parameters such as the number of piles, the distance between piles, gradation and thickness of the granular layer on the load-settlement behavior of a pile raft system. The results showed the importance of granular layer to reduce the settlement of non-connected pile raft system when the roles of piles are to reduce the settlement. In other words when the piles have major contribution on the bearing capacity of pile raft system, presence of a granular layer may increase the settlement.
A.r. Sattarifar, M.k. Sharbatdar, A. Dalvand,
Volume 13, Issue 4 (12-2015)
Abstract

In this paper, an experimental study has been conducted on strengthening of reinforced concrete (RC) connections by FRP sheets. The innovation of this research is using narrow grooves on critical regions of connection to increase the adherence of FRP sheets and prevent their early debonding. Therefore, four RC connections were made and tested under a constant axial load on the column and an increasing cyclic load on the beam. The first specimen, as the standard reference specimen, had close tie spacing in ductile regions of beam, column and panel zone based on seismic design provisions, and the second specimen, as the weak reference specimen did not have these conditions in all regions. Two other weak specimens were strengthened using two different strengthening patterns with FRP sheets one by ordinary surface preparation and the other with surface grooving method for installing FRP sheets on the connection. The results showed that ultimate load and ductility of the weak specimen compared to standard specimen decreased 25% and 17%, respectively. The shear failure and concrete crushing were prevented in the ductile regions of the beam and panel zone in both strengthened specimens. Also, it was observed that early debonding of FRP sheets was prevented in the strengthened connection with grooving pattern and so had desirable ductility and bearing capacity similar to the standard specimen.


L. Zeng, Q. Zhou, Ch. Xu, Y. Wu, X. Tu,
Volume 13, Issue 4 (12-2015)
Abstract

To study seismic performance of concrete-encased composite columns with T-shaped steel cross-section, twelve half-scale columns were tested under quasi-stastic cyclic loading. The result indicates that concrete-encased composite columns with T-shaped steel section possess good seismic performance. The failure modes include bending failure, shear-bond failure, shear compression failure and shear-composition failure. Unsymmetrical phenomenon of positive and negative hysteresis loop was shown evidently. Span ratio has a great influence on failure mode. The ductility performance decreases with increasing of axial compression level. As stirrup ratio increases, ductility and bearing capacity of columns are improved greatly, and energy dissipation capacity after yielding is enhanced. Cross tie can enhance ultimate bearing capacity, and lower strength attenuation and stiffness degradation on the later loading stage


E. Kozem Šilih, M. Premrov, M. Kuhta, S. Šilih,
Volume 13, Issue 4 (12-2015)
Abstract

The paper presents a parametric numerical study on the horizontal load-bearing capacitiy of timber framed wall elements coated with single fibre plaster boards (FPB) that can be used in the construction of single- or multi-storey prefabricated buildings. The research deals with both the full elements (without any opening) and with elements containing an opening. The key behaviour indicators like the racking stiffness and strength were determined and presented as ratios dependent on the opening area. A comparative study has proved that none of the methods from the literature that were previously developed for different types of wall elements can be accurately applied to the FPB-sheated panels. It has also been shown that the methods currently available in the European design codes underestimate the capacity of wall elements with openings. Based on the results some diagrams are proposed that enable quick and efficient determination of the essential properties of wall elements with arbitrary areas of openings and may thus represent a useful tool for the structural design process.


Mohammad Reza Lotfizadeh, Mohsen Kamalian,
Volume 14, Issue 2 (3-2016)
Abstract

A study has been conducted on the bearing capacity of strip footings over sandy layered soils using the stress characteristic lines method. Traditional bearing capacity theories for specifying the ultimate bearing capacity of shallow foundations are based on the idea that the bearing layer is homogenous and infinite. However layered soils are mainly happening in practice. The stress characteristic lines method is a powerful numerical tool in order to solve stability problems in geotechnical engineering. In the present paper, an appropriate algorithm is derived for estimating the static bearing capacity of strip footing located on two layered soils using the stress characteristic lines method. Some numerical and experimental examples are presented in order to validate the proposed algorithm. Some graphs and equation are presented for initial estimating the effective depth of strip footings located on two layered soils.


Maryam Haghbin,
Volume 14, Issue 7 (10-2016)
Abstract

In the present research, an analytical method is applied to determine the bearing capacity of strip footing on two layers of the soil. Bearing capacity of the footing is calculated according to soil resistance beneath the foundation and virtual retaining wall method. In the said method, the active and passive force on the retaining wall are considered equal on the edge in order to determine the bearing capacity of the footing. Regarding two layers of soil, the active and passive forces of each layer is found and their resultant is applied to calculate footing bearing capacity. This method has many advantages including the possibility to determine the depth of rupture surface of the soil beneath the footing, and to study the effect of the soil second layer on footing bearing capacity. Moreover, the effect of soil improvement beneath the footing as well as the depth and width of compacted area on bearing capacity of footing are also studied here in this research. In general, the studied parameters in this project consist of soil layers thickness, soil cohesion and friction angle, footing depth and width, the width of compacted soil beneath the footing, and the depth of underground water. By programming in MATLAB, the calculation and deduction was fulfilled. The results were compared with the bearing capacity of the footing on one layer of the soil in various situations in order to study the effect of various parameters in two layers of the soil. Finally, this bearing capacity of the footing was compared with the previous experimental methods and reliable results were obtained.



Volume 15, Issue 6 (9-2017)
Abstract

In this study, the shear strength parameters of the Kaolinite clay, as the control material, and the Kaolinite clay reinforced by different percentages of two different types of crumb rubber content have been evaluated. The consolidated drained and unconsolidated undrained triaxial and California bearing ratio tests have been conducted on the control and crumb rubber reinforced soils. Addition of crumb rubber would improve shear strength parameters such as cohesion, friction and dilation angles, stiffness and the ductility of the reinforced soil. 5, 10 and 15 % (by the weight of dry soil) of crumb rubber content were used in this study which were undergone confining stress levels of 100, 200 and 300 kPa and an optimum crumb rubber content is found, which results in the maximum bearing capacity of the soil. Also, due to the non-linearity of the failure mode of reinforced soil and inadequacy of Mohr–Columb envelope for describing the behaviour, a failure mode is proposed for the clay soils reinforced by crumb rubber. This failure criterion is useful for failure envelope of clay-rubber matrix.



Volume 15, Issue 6 (9-2017)
Abstract

Pile load tests and numerical analysis of a small-scale model pile in unsaturated clayey soil are presented in this paper. A small-scale model pile was simulated to bear a static axial loading in unsaturated soil using finite element method. All parameters used in the finite element method were obtained in laboratory tests, including the direct shear test, interface direct shear test, and filter paper method. The numerical analysis results were compared with the pile load test results. The results show that the general trend of pile load and pile head settlement relationship obtained by the numerical analysis shows a good consistence with the pile load test results. With increasing water content of the soil, the matric suction, dilatancy angle and shear strength decrease, and consequently the ultimate bearing capacity of pile decreases.



Volume 15, Issue 6 (9-2017)
Abstract

It is vital to control the settlement of ultra-high voltage and long span tower foundation because of the difficult construction and strict deformation control. Based on the thinking of deformation compatibility, the mechanical model of deformation compatibility between pile and soil is established. Relying on the long span tower project Lingzhou–Shaoxing ±800 kV DC transmission lines across the Yangtze River, through checking ultimate bearing capacity of existing pile foundation, it can be obtained that the present design foundation can effectively meet the upper 200–220 t load, but it cannot meet the load requirements about 300 t in the construction. The failures of tower foundation mainly display that piles cut into the soil with penetration type in the early condition. With the load increasing, the shallow soil and infrastructure gradually damage with the whole cap sinking, cushion layer destruction and the surrounding soil uplifting. As a result, tower foundation is unable to withstand the effect of upper overload and the whole tower becomes shear failure. The treatment scheme was proposed that it can improve the cushion thickness and strength combined with grouting consolidation to soil around the piles. Thus, the stability of tower foundation improves significantly and settlement was controlled within the permitted range of below 10 mm, which can meet the structure requirements. The results of numerical simulation based on deformation compatibility between pile and soil coincide well with field measured results.



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