scholarly journals Optimization of the Ultimate Bearing Capacity of Reinforced Soft Soils through the Concept of the Critical Length of Stone Columns

2021 ◽  
Vol 7 (9) ◽  
pp. 1472-1487
Author(s):  
Nour El Islam Boumekik ◽  
Mohamed Labed ◽  
Mekki Mellas ◽  
Abdelhak Mabrouki
Keyword(s):  
Bearing Capacity ◽  
Numerical Models ◽  
Critical Length ◽  
Ultimate Bearing Capacity ◽  
Analytical Equation ◽  
Stone Columns ◽  
Length Ratio ◽  
Soft Soils ◽  
Bearing Capacity Ratio ◽  
Capacity Ratio

The objective of this paper is to develop an analytical equation based on the concept of the critical-length of columns in order to optimize the ultimate bearing-capacity of soft soils, supporting a strip footing and reinforced by a group of floating stone columns. Optimization procedure was performed on three-dimensional numerical models simulated on the Flac3D computer code, for various soft-soils with different undrained-cohesions (Cu=15–35kPa), reinforced by columns of varying lengths (L) and area replacement ratio (As=10-40%), considering different footing widths B. Obtained results indicate that the optimal bearing-capacity ratio (Ultimate bearing-capacity of reinforced soil/unreinforced soil) is reached for the column critical-length ratio (Lc/B) and increase with increase of the later ratio, depending  on As and Cu. Analysis of results also showed that the optimal values of the bearing-capacity ratio in the reinforced soils remain bounded between the lower and higher values (1.28-2.32), respectively for minimal and maximal values of the critical-length ratio (1.1) and (4.4). Based on these results, a useful analytical equation is proposed by the authors, for the expression of the critical-length; thus ensuring an optimal pre-dimensioning of the stone columns. The proposed equation was compared with the data available in the literature and showed good agreement. Doi: 10.28991/cej-2021-03091737 Full Text: PDF

scholarly journals Behaviour of eccentrically inclined loaded rectangular foundation on reinforced sand

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sujata Gupta ◽  
Anupam Mital
Keyword(s):  
Bearing Capacity ◽  
Loading Conditions ◽  
Test Results ◽  
Bearing Capacity Ratio ◽  
Reinforced Sand ◽  
The Core ◽  
Capacity Ratio ◽  
Core Boundary ◽  
Rectangular Foundation ◽  
Increasing Load

Abstract This study presents the behaviour of model footing resting over unreinforced and reinforced sand bed under different loading conditions carried out experimentally. The parameters investigated in this study includes the number of reinforced layers (N = 0, 1, 2, 3, 4), embedment ratio (Df /B = 0, 0.5, 1.0), eccentric and inclined ratio (e/L, e/B = 0, 0.05, 0.10, 0.15) and (a = 0°, 7°, 14°). The test sand was reinforced with bi-axial geogrid (Bx20/20). The test results show that the ultimate bearing capacities decrease with axial eccentricity and inclination of applied loads. The test results also show that the depth of model footing increase zero to B (B = width of model footing), an increase of ultimate bearing capacity (UBC) approximated at 93%. Similarly, the multi-layered geogrid reinforced sand (N = 0 to 4) increases the UBC by about 75%. The bearing capacity ratio (BCR) of the model footing increases with an increasing load eccentricity to the core boundary of footing; if the load eccentricities increase continuity, the BCR decreases. The tilt of the model footing is increased by increasing the eccentricity and decreases with increasing the number of reinforcing layers.

scholarly journals Axial Compression Performance of Square Thin Walled Concrete-Filled Steel Tube Stub Columns with Reinforcement Stiffener under Constant High-Temperature

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1098 ◽  
Author(s):  
Xuetao Lyu ◽  
Yang Xu ◽  
Qian Xu ◽  
Yang Yu
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Bearing Capacity ◽  
Numerical Models ◽  
Steel Tube ◽  
Ultimate Bearing Capacity ◽  
Displacement Curve ◽  
Concrete Filled Steel Tube ◽  
Finite Element Software ◽  
Thin Walled

This study investigated the axial compressive performance of six thin-walled concrete-filled steel tube (CFST) square column specimens with steel bar stiffeners and two non-stiffened specimens at constant temperatures of 20 °C, 100 °C, 200 °C, 400 °C, 600 °C and 800 °C. The mechanical properties of the specimens at different temperatures were analyzed in terms of the ultimate bearing capacity, failure mode, and load–displacement curve. The experiment results show that at high temperature, even though the mechanical properties of the specimens declined, leading to a decrease of the ultimate bearing capacity, the ductility and deformation capacity of the specimens improved inversely. Based on finite element software ABAQUS, numerical models were developed to calculate both temperature and mechanical fields, the results of which were in good agreement with experimental results. Then, the stress mechanism of eight specimens was analyzed using established numerical models. The analysis results show that with the increase of temperature, the longitudinal stress gradient of the concrete in the specimen column increases while the stress value decreases. The lateral restraint of the stiffeners is capable of restraining the steel outer buckling and enhancing the restraint effect on the concrete.

PERBAIKAN TANAH LEMPUNG BERLANAU MENGGUNAKAN KOMBINASI PERKUATAN ANYAMAN BAMBU DAN GRID BAMBU

2019 ◽  
Vol 18 (1) ◽  
pp. 67-79
Author(s):  
Aef Saefudin ◽  
Sri Wulandari
Keyword(s):  
Bearing Capacity ◽  
Bearing Capacity Ratio ◽  
Capacity Ratio

Berbagai metode perbaikan tanah telah banyak dikembangkan, salah satunya dengan perkuatan tanah sebagai alternatif pemecahan masalah terhadap daya dukung tanah yang rendah dan besarnya penurunan. Dalam penelitian ini, anyaman bambu dan grid bambu digunakan sebagai material perkuatan yang diharapkan dapat menjadi alternatif material perkuatan untuk meningkatkan daya dukung tanah lempung dengan variasi kedalaman perkuatan, jarak grid dan spasi lapis perkuatan. Tujuan dari penelitian ini adalah untuk mengetahui peningkatan daya dukung dari setiap variasi dengan nilai daya dukung tanpa perkuatan. Metodologi peneltian yang digunakan adalah pengujian dengan skala laboratorium. Data yang didapatkan dari pengujian tersebut kemudian dianalisa dengan membandingkan nilai daya dukung antara tanah tanpa perkuatan dengan menggunakan perkuatan yang dinyatakan dalam Bearing Capacity Ratio (BCR). Dari studi model di laboratorium diperoleh hasil bahwa dengan adanya pengurangan kedalaman perkuatan, jarak grid dan pengurangan spasi lapis perkuatan akan memberikan angka rasio daya dukung (BCR) yang semakin besar. Hasil diperoleh kombinasi yang memberikan nilai daya dukung tertinggi adalah penggunaan jarak grid 5 cm perkuatan dengan jarak kedalaman 0,15B (B adalah lebar pondasi) dengan spasi perkuatan (z) 0.4B. Nilai daya dukung tersebut sebesar 68 kPa dengan rasio daya dukung (BCR) sebesar 4 atau persen peningkatannya sebesar 300%.

A study of bearing capacity of skirted octagonal footings resting on different sands

2021 ◽  
Vol 1 (107) ◽  
pp. 21-31
Author(s):  
A. Thakur ◽  
R.K. Dutta
Keyword(s):  
Numerical Analysis ◽  
Bearing Capacity ◽  
Stress Level ◽  
Design Methodology ◽  
Numerical Models ◽  
Ultimate Bearing Capacity ◽  
Field Size ◽  
3D Software ◽  
Plaxis 3D ◽  
Made In

Purpose: After a thorough study of literature it is concluded that the studies related to unskirted/skirted octagonal footings on sand have not yet been investigated. Thus, this paper presents a numerical analysis to assess the ultimate bearing capacity of the unskirted, unskirted-embedded, singly and doubly skirted octagonal footings resting on different sands (S1, S2, and S3). The length of skirt and depth of the embedded footing were varied from 0.0B to 1.5B. Design/methodology/approach: The numerical square and octagonal footing with singly and doubly skirted footing models were developed using Plaxis 3D software. Findings: The results of the doubly skirted octagonal footings ultimate bearing capacity were marginally higher in comparison to the singly skirted footing at all normalised skirt depths as well as for all sands up to a Ds/B ratio 0.25 beyond which the increase in the ultimate bearing capacity in case of doubly skirted footing was appreciable. Research limitations/implications: The results presented in this paper were based on numerical analysis. However, for the actual footings the soil placement and compaction, details of skirt construction and the stress level will be different from the numerical analysis. Further investigations using full-scale numerical models simulating field size footings were recommended to generalize the results. Originality/value: No such study on singly and doubly skirted octagonal shaped footings were conducted so far. Hence, an attempt was made in this article to predict the bearing capacity of those footings using Plaxis 3D.

scholarly journals Influence of Infill Wall Configuration on Failure Modes of RC Frames

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaojie Zhou ◽  
Xiaoyuan Kou ◽  
Quanmin Peng ◽  
Jintao Cui
Keyword(s):  
Bearing Capacity ◽  
Rc Frame ◽  
Infill Wall ◽  
Bearing Capacity Ratio ◽  
Short Column ◽  
Shear Span ◽  
Capacity Ratio ◽  
Rc Frames ◽  
Shear Bearing Capacity ◽  
Lateral Constraint

An improper configuration of masonry infill walls in RC frame may lead to short column effect on the columns, which is harmful to the seismic behavior of the structure. In this study, a bare frame and two single-story, single-bay RC frames, partially infilled with masonry, were tested under cyclic loading. The failure mechanism and seismic performance of these partially infilled RC frames (with an infill height of 600 mm) with different types of connections were analysed. Based on the experiment, nonlinear finite element simulation and analysis were conducted to study the effects of the infill walls and connections. The results show that both mechanical performance and failure mode are affected by the infill height, the type of connection between the frame and the infill, and the ratio of shear bearing capacity of the frame column to that of the infill. For the masonry-infilled frame with rigid connection, the higher the infill wall is, the lower the shear bearing capacity ratio will be. Thus, the effect of the lateral constraint of the infill wall on the column increases, and the shear span ratio of the free segment of the column decreases, resulting in the short column effect. Based on the analysis results, a value of 2.0 is suggested for the critical shear bearing capacity ratio of the frame column to the infill wall. If the shear bearing capacity ratio is less than 2.0 and the shear span ratio of the column free segment is not more than 2.0, the short column effect will occur. For the infilled frame with flexible connection, both the lateral constraint from the wall to the column and the wall-frame interaction decrease; this reduces or prevents the short column effect. The conclusion can present guidance for the design and construction of masonry-infilled RC frame structure.

scholarly journals A NEW DESIGN EQUATION FOR PREDICTION OF ULTIMATE BEARING CAPACITY OF SHALLOW FOUNDATION ON GRANULAR SOILS

2014 ◽  
Vol 19 (Supplement_1) ◽  
pp. S78-S90 ◽  
Author(s):  
Ehsan Sadrossadat ◽  
Fazlollah Soltani ◽  
Seyyed Mohammad Mousavi ◽  
Seyed Morteza Marandi ◽  
Amir H. Alavi
Keyword(s):  
Bearing Capacity ◽  
Numerical Models ◽  
Ultimate Bearing Capacity ◽  
Prediction Performance ◽  
Shallow Foundations ◽  
Shallow Foundation ◽  
Granular Soils ◽  
Good Prediction ◽  
Design Equation ◽  
Statistical Measures

A major concern in design of structures is to provide precise estimations of ultimate bearing capacity of soil beneath their foundations. Direct determination of the bearing capacity of foundations requires performing expensive and time consuming laboratory tests. To cope with this issue, several numerical models have been presented by researchers. This paper presents the development of a new design equation for the prediction of the ultimate bearing capacity of shallow foundations on granular soils using linear genetic programming (LGP) methodology. The ultimate bearing capacity is formulated in terms of width of footing, footing geometry, depth of footing, unit weight of sand, and angle of shearing resistance. The LGP-based design equation is established using the results of several load tests on real sized foundations presented in the literature. Validity of the model is verified using a part of laboratory data that are not involved in the calibration process. The statistical measures of coefficient of determination, root mean squared error and mean absolute error are used to evaluate the performance of the model. Sensitivity and parametric analyses are conducted and discussed. The proposed model accurately characterizes the ultimate bearing capacity resulting in a very good prediction performance. The LGP model reaches a better prediction performance than the well-known prediction equations for the bearing capacity of shallow foundations.

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