Bearing Capacity Behavior Research Articles

CLSM bridge abutments – Finite element modeling and parametric study

Controlled low strength materials (CLSMs) are increasingly gaining importance in the construction industry. Among many applications, CLSMs can be used for rapid and sustainable construction of bridge abutments. This paper describes the finite element analysis of a full-scale loading test of a bridge abutment backfilled with the CLSM referred to as “CLSM bridge abutment”. The finite element analysis will help with the understanding of the behavior of CLSM bridge abutments, in terms of bearing capacity, displacements and the developed axial force in anchors. The accuracy of the finite element results for the response and failure behavior of a CLSM mass was evaluated by a comparison with the experimental results. The experimental program included both standard compressive strength testing on CLSM cylinders and a laboratory full-scale testing on a CLSM bridge abutment. The analysis shows that the performance of a CLSM abutment while subject to a service load or a limiting failure load from a bridge superstructure can be simulated in a reasonably accurate manner.In addition, a parametric study was conducted to better understand the performance of the CLSM bridge abutments in terms of bearing capacity and overall behavior. This study investigated the performance of the CLSM bridge abutments as they are affected by material curing age, environment temperature and construction details. The results indicated that the CLSM bridge abutment is capable of carrying typical bridge loads with relatively after only one day from the placement. It was observed that the bearing capacity increased with further curing of the CLSM material.

Experimental studies on interference of two angular footings resting on surface of two-layer cohesionless soil deposit

The paper presents an experimental study pertaining to the interference of two closely spaced small scaled model square and rectangular footings, each of two different sizes, and resting on the surface of a two-layered sand deposit. The effect of the parameters such as the depth of the upper weak sand layer D and the clear spacing between the footings S on the bearing capacity and settlement behavior of the interacting footings were studied. The study indicates that the bearing capacity and settlement values of the closely spaced footings on the layered deposit decrease with increase in D/B ratio, where B is the width of footing. The results are presented in terms of efficiency and settlement factors, ξγ and ξδ, and their variations with S/B ratio are presented. The present experimental observations are generally found to be in good agreement with similar studies available in the literature.

Computerised processing of ground investigation data and use in predicting the load-settlement behaviour of piled foundations

A new computer program “PILESET” is developed for use in predicting the bearing capacity and load-settlement behaviour of axially loaded single piles. The program can analyse almost any soil profile and accommodates (a) displacement piles (b) replacement (c) friction piles, (d) end-bearing piles, (e) under-reamed piles and (f) partially sleeved piles. A variety of soil input data can be used, including: (i) standard penetration tests, (ii) cone/piezo-cone tests, (iii) pressure-meter tests and (iv) laboratory tests. The above data types can be combined, if desired, for pile analysis by PILESET. The program calculates the shaft and base capacities of a pile based on 23 methods published in design guides in over 10 European countries. PILESET also predicts the pile load-settlement curve using five published methods, which include two modified load transfer (t-z) approaches formulated by the author. To demonstrate the capabilities of the program, analysis is carried out for case study involving seven full-scale screw piles formed in sand and tested to failure. In each case, the load-settlement curve computed using the author’s modified method in PILESET is found to be in excellent agreement with the actual pile test results.

The Simulation Analysis of the Bearing Capacity of the BFRP Reinforced Concrete Columns

The behavior of the bearing capacity of the reinforced concrete columns confined with basalt fiber reinforced plastic sheet (BFRP) under axial compression is analyzed by the finite element method, and obtain the ultimate compressive strength and stress distribution of the BFRP. The analysis results show that the simulation results agree well with the experimental results, the strength and ductility of the BFRP reinforced concrete columns are improved obviously. The ratio of the strength test values and simulation values is between 0.91~1.14, the error is within an acceptable range. Then based on the strength of FRP confined concrete columns model, the test values are compared with those of the strength model calculation values, the ratio of the simulation values and calculated values is ​​between 0.94 to 1.03,that means the simulation values are credible. The mechanical properties of the BFRP reinforced concrete column are improved significantly.

Experimental and numerical study on steel reinforced high-strength concrete short-leg shear walls

Reinforced concrete (RC) short-leg shear wall structure is a new type of mid-rise residential structure system. It has been widely used in China. In order to expand its scope of application to higher high-rises, studies have been focused on novel approaches improving the seismic behavior of this structure system. The present experimental and numerical study was performed to investigate the bearing capacity and seismic behavior of steel reinforced high-strength concrete (SRHC) short-leg shear walls. Results indicate that the tested SRHC short-leg shear walls have shown a bending failure mode, with the crushing of the compressed concrete and the yielding of the tensioned steel. The loading capacity of SRHC short-leg shear walls was greatly improved. The ductility coefficient of the specimens was between 3.62 and 4.35, which was equivalent to that of common RC short-leg shear walls. The specimens with steel-plate skeleton are more ductile in terms of displacement ductility and energy dissipation than the specimens with steel-truss skeleton. The results also indicate that decreasing the compressive ratio improves ductility. The bearing capacity of SRHC short-leg shear wall can be considerably improved by using high strength concrete, while the ductility decreases with the increase of the concrete strength due to the inherent brittleness of high-strength concrete.

Bucket group effect of the composite multi-bucket structure

As a novel type of foundation in beach and shallow sea, the bucket structure is especially suitable for complex conditions such as soft clay ground and the worse types of sea environments. In this paper, the bearing capacity of a multi-bucket structure is studied by experiments with a single bucket and four-bucket foundation in a saturated sand layer. Based on the experimental data and numerical analysis results, the bearing capacity behavior and the bucket group effect are compared and analyzed. Furthermore, some influential factors, such as the soil type, the ratio of length to diameter L/D, the ratio of the bucket spacing to the bucket diameter S/D, and the bucket number are introduced and their effects on the multi-bucket structural capacity are investigated. The vertical static capacity adjustment factor is introduced to evaluate the bucket group effects of the multi-bucket foundation.

Performance evaluation of a shallow foundation built on structured clays under seismic loading

Due to the increased need of storage, larger and higher structures are being built all over the world, thus requiring a more careful evaluation of the mechanical performance of their foundation deposits both in terms of bearing capacity and compressibility behaviour. The design of such structures and their serviceability and stability is largely governed by the effects of the dynamic loading conditions principally because of their significantly elevated risk in seismic prone zones. In this paper, numerical analyses using an advanced constitutive model, able to account for the initial soil structure and its progressive degradation, have been performed to investigate the seismic response of a silo foundation built on structured clays. The proposed analyses involve the use of a fully-coupled finite element approach. For the dynamic simulations, three different input motions have been selected form earthquake databases according to the seismic hazard study of the specific site. The results of the silo dynamic response are illustrated in terms of signal amplification, permanent excess pore water pressures, accumulated displacements and structure induced degradation during and after the seismic loading. The dynamic behaviour of the footing indicates that extreme earthquake events can induce large destructuration in natural clays, leading to ground settlements up to twice the observed ones under static loads, which need to be properly accounted for in the design. This suggests that there are significant advantages in using advanced models which recognise the existence of initial soil structure and its subsequent damage due to the applied dynamic loads.

Model testing and numerical investigation of interference effect of closely spaced ring and circular footings on reinforced sand

Due to heavy loads and the non-availability of suitable construction sites, engineers are often required to place footings at close spacing. These footings influence each other, including effects on load-settlement and bearing capacity behavior. In this research the bearing capacity of closely located ring and circular footings on reinforced sand has been investigated numerically and experimentally. The goal of this study is to evaluate the interference effect on the bearing capacity of adjacent circular and ring footings. Footings on reinforced and unreinforced sand have been investigated. In this research, interference effect of footings, shape effects, effect of spacing between footings and also the effect of reinforcement layer on the bearing capacity are studied. To achieve these objectives laboratory circular and ring footing models and also numerical models were used. Finite element computer code PLAXIS 3D Foundation was used for numerical modeling. Experimental and numerical analysis results show that the ultimate bearing capacity of two closely spaced circular and ring footings is greatest when they stand exactly beside each other and decreases with increase in the spacing to footing diameter ratio (Δ/D). It is found that for Δ/D > 4, the bearing capacity of each adjacent footing is almost the same as that for single footing. This means that for a center-to-center spacing greater than 4D, no significant interference effect was observed and each footing acted more or less independently, similar to a single footing.

Soft soil strengthening by stone columns: case of the embankment under the bridge “Moulay Youssef” (Rabat/Salé)

The soil is generally a heterogeneous material presenting very variable characteristics. In a general way, the main problems related to soils are: low bearing capacity, deformations under static or dynamic loads, large displacements and large settlements of soft soil where the soil moves according to a fixed ground water table. The development of soil mechanics and geotechnical engineering has led to the amelioration of a wide range of soil improvement techniques. These techniques consist in modifying the characteristics of the ground by physical action or by incorporating columnar inclusions made of highly compacted gravel or granular material into the original soil. Stone column is one of the soft ground improvement methods, applicable to a wide range of soil strata and an economical method of support in compressible and cohesive soils. However, there are many difficulties in quantitative analysis of soil column interaction due to the fact that bearing capacity and consolidation behavior of stone column-mat foundation system is affected by various parameters. In the present study, mechanism and various parameters of stone column behavior are investigated by loading tests. Also, tests results are compared to the finite element numerical modeling “Plaxis 2D” (case study: the embankment under the bridge “Moulay Youssef, Rabat/Sale”).

Experiment Study on Bearing Capacity of Muddy Siltstone Foundation and its Application

Rock-socket cast-in-situ piles is a commonly used style of foundation, but theoretical analysis, experiments and test research of bearing capacity behavior about rock-socket piles in soft rock have not adapted to the requirement of engineering. The static loading test of single pile on a project in argillaceous and silt laminate, through which the skin friction and point bearing capacity were measured, the bearing capacity behavior of rock-socket cast-in-situ piles in soft rock was analyzed.

Axial Compression Ratio Limit of Regional Confined Concrete Columns

Through earthquake simulation experiment of nine regional confined concrete columns with different axial compression ratio, the bearing capacity and seismic behavior of regional confined concrete columns were studied in this paper. Considering the ductility, stiffness, energy-dissipation performance and related factors of regional confined concrete columns under different axial compression ratio, by comparative analysis of the hysteretic behavior of the specimens, the limit of axial compression ratio of regional confined concrete columns is proposed for seismic design.

Cyclic Lateral Load Test on T-Shaped Reinforced Concrete Columns

Based on the experiment of eight reinforced concrete T-shaped columns under low cyclic load, the factors which affect bearing capacity and seismic behavior, such as limb length, axial load ratio, stirrup ratio and the arrangement of longitudinal bars, etc., are analyzed. Tests results show that the bearing capacity of the columns increases, but the ductility is decreased with an increase of axial load ratio. The bearing capacity of T-shaped column increases when the web gets longer, while its deformability and ductility decrease. Besides, increase of stirrup ratio and longitudinal bars in the end of the web also have effect on the ductility of the columns.

해상풍력 모노포드 버켓기초의 지지력 거동 - 원심모형실험 및 수치해석

해상풍력 기초로 사용되는 모노포드 석션 버켓기초의 지지력 거동에 대하여 원심모형실험과 수치해석을 통하여 연구하였다. 대상 구조물은 서해안 지역을 대상으로 검토된 해상풍력타워 기초로, 실트질 모래층에 설치하는 것으로 설계되었다. 원심모형실험에 사용된 모형지반은 대상 지반과 유사한 물성을 갖도록 조성하였다. 실험 가속 상태에서 소형 콘 관입시험과 벤더 엘리먼트를 사용한 전단파속도 측정을 통하여 물성을 평가하고 모사 대상 지반과의 유사성을 검증하였다. 원심모형실험으로 해상풍력 기초에 작용하는 하중을 재하하고 거동을 계측할 수 있도록 실험 시스템을 구축하였고, 모노포드 석션 버켓기초의 하중-회전각 관계를 통해서 지지력 거동을 평가하였다. 최적의 실험 조건을 선정 및 검증하기 위하여 수치해석을 수행하였으며, 모델의 자중, 모델과 경계면의 거리 및 지반 탄성계수의 변화에 따른 지지력 거동의 차이를 검토하였다. In order to evaluate the bearing capacity behaviour of a monopod suction bucket foundation for an offshore wind tower at the western sea of Korea, a centrifuge load test and numerical analyses were performed. The monopod bucket foundation was designed to be installed in a silty sand layer. The model soil was prepared to simulate a target site by using soil samples having similar properties and controlling relative density. In-flight miniature cone penetration test and bender element array were used to confirm that the model soil had represented the target site conditions. The load - rotation curve of the centrifuge load test was analysed. A series of numerical analyses were performed to validate the experimental conditions. Self-weight of the model, distance to the boundary and elastic modulus of the soil layer were varied to study their effects on the load - rotation curves.

BEARING CAPACITY AND SETTLEMENT OF FOOTINGS IN UNSATURATED SAND

The focus of the study in this paper is directed towards understanding the influence of three parameters; namely, (i) matric suction, (ii) overburden stress, and (iii) dilation, on the bearing capacity and settlement behavior of surface and embedded model footings in unsaturated sands. The results show that the bearing capacity and settlement behavior of unsaturated sands are significantly influenced by all the three parameters. In addition, comparisons are provided between the predicted and measured bearing capacity and estimated and measured settlement values using the proposed modified Terzaghi's equation and modified Schmertmann's CPT-based method, respectively. There is a good comparison between the predicted/estimated and measured bearing capacity and settlement values for the laboratory and field tests using the proposed modified methods.

A Study on the Failure Mechanism of Suction Caisson under Vertical Load

As a new type of deep water offshore foundation, suction caisson is widely used to offshore structures. However, the current methods of evaluation and design cannot meet the increasing requirement of engineering practice. In this dissertation, the studies are emphasized on finite element method for analyzing the suction caisson bearing capacity behavior and the failure mechanism under the vertical load. Based on studying the vertical bearing behavior of caissons with different ratio of length to diameter L / D, it shown that as L / D increases, the vertical bearing capacity growth slowed.

Experimental Study of the Rotary Filling Piles with Large-Diameter under the Axial Load

Based on the experimental study of rotary filling piles with large diameter subjected to axial load in deep soft soil, the bearing capacity behavior and load transfer mechanism were discussed. Results show that in deep soft soil foundation, the super–long piles behave as end-bearing frictional piles. The exertion of the shaft resistance is not synchronized. The upper layer of soil is exerted prior to the lower part of soil. Meanwhile, the exertion of shaft resistance is prior to the tip resistance. For the different soil and the different depth of the same layer of soil, shaft resistance is different.

Research Review on Bearing Capacity Behavior of Pile Foundation under Lateral Load

Based on review of current study on pile foundation under lateral load, an introduciton is given to some theoretical methods commonly used at home and aboard, with emphasis placed on the elastic subgrade reaction method and the p-y method as well as their characteristics and applicability, and some problems needed for further study are put forward. The present study provides a train of thought for further research on the behavior of large-diameter pile under lateral load.

두께가 다른 이종배관 용접부 면삭 각도 변화에 따른 하중지지능력 평가

두께가 다른 이종강도 배관 용접부에서 인장, 내압 및 굽힘응력에 대한 하중지지능력을 평가하였다. 1.22, 1.54, 및 1.89의 두께비를 갖는 API X65-API X80, API X42-API X65 및 API X42-API X80 배관 용접부를 유한요소해석을 통하여 하중지지능력을 평가하였다. 이종강도 배관의 두께비가 1.5 이하에서 인장강도와 최대모멘트는 면삭각도 변화에 큰 영향을 받지 않으나 두께비가 1.5 이상에서는 큰 영향을 받는다. 저강도 배관의 길이방향 면삭각도와 두께비 변화에 따라서는 내압에 의한 파열압력은 영향을 받지 않는다.

Load transfer behaviour of a tapered rigid pile

Based on Mohr–Coulomb theory and the load transfer method, a new method of analysing the load–settlement relation and the axial force distribution model in a tapered pile is suggested. The method proposed in the paper considers the influence of the pile–soil radial interaction on the bearing capacity and settlement behaviour. The calculation results show that the pile–soil radial interaction is strengthened and the bearing capacity of a single pile is increased when the taper angle of a rigid pile is increased. The reliability was verified by two model tests. Calculated results obtained by the proposed method were compared with the test data. The close agreement between the calculated and measured values confirmed that the method is reasonably accurate for analysing the behaviour of tapered rigid piles.

3D FEM Analysis on Bearing Capacity Behaviors of the Multi-Piles Foundation for Offshore Wind Turbines

With the fast development of technology, offshore wind power generation is playing a major role for developing renewable sources in the whole world nowadays. According to the proposed Hangzhou Bay wind farm in China, using general-purpose finite element software, bearing capacity behaviors of the multi-piles foundation for offshore wind turbine are simulated in this paper by the 3D finite element method. The Mohr - Coulomb model is adopted as the elastic - plastic constitutive model of the soil and also the Coulomb Friction model as the pile - soil contact model. The bearing capacity behavior of multi-piles foundation for offshore wind turbines under monotonic and combined loading are discussed, also the bearing capacity behaviors by changing diameters, spaces of piles and loading directions as well.