Evaluation Of Bearing Capacity Research Articles

Evaluation of the pseudo-dynamic bearing capacity of surface footings on cohesionless soils using finite element lower bound limit analysis

ABSTRACT Design of shallow foundations subjected to dynamic loading is an important topic in the geotechnical engineering practice. In this study, an attempt has been made to evaluate the seismic bearing capacity of a strip footing founded on a soil deposit using the lower bound limit analysis method merged with the finite element formulation adopting the second-order conic programming (SOCP) approach. To this end, a well-established pseudo-dynamic loading scheme has been employed to apply the seismic loading on the surface footing. Accounting for the various conditions of the underlying soil layer, the results of the so-called ‘conventional pseudo-dynamic (CPD)’, ‘spectral pseudo-dynamic (SPD)’ and ‘modified pseudo-dynamic (MPD)’ bearing capacity analyses are compared with one another and their pseudo-static counterparts in terms of the value of parameter. The results show the notable influence of the amplification factor, the impedance factor and the site characteristics on the seismic bearing capacity of shallow foundations. In addition, the results obtained from the MPD, CPD and SPD methods are observed to bear a good agreement with each other. Moreover, the MPD approach was observed to render the most conservative seismic bearing capacity values.

Effect of soil moisture content on the bearing capacity of small bored piles in the unsaturated soil of Maringá, Paraná, Brazil

In this study, the influence of soil moisture on the bearing capacity of piles founded in an unsaturated clay soil was investigated. The soil studied, composing the upper soil layer in Maringá, Brazil, is lateritic, has degree of saturation between 37% and 70% and has collapsible behaviour when wet. The bearing capacity was determined by full-scale load tests following the Brazilian Standard for Static Load Test. Two pile lengths, 4 m and 8 m, were considered. To analyse the influence of soil moisture, two tests were performed for each pile length: one in soil in its natural moisture content and another in pre-moistened soil. Results show that for both pile lengths, an increase in water content caused a significant reduction in bearing capacity, which is attributed to the decrease in the matric suction of the soil. This is confirmed by the results of the initial evaluation made on the variation of matric suction and its contribution to the bearing capacity with changes in water content. In summary, this study confirms that the pile bearing capacity in unsaturated soil is dependent on soil water content, highlighting the fact that the approach of assuming full saturation condition in the evaluation of the pile bearing capacity in such soil may give erroneous results. Moreover, this study demonstrate that the empirical methods most commonly used in Brazil for pile bearing capacity determination, the Décourt & Quaresma and Aoki & Velloso methods, are overly conservative when applied to the Maringá soil.

Evaluation of bearing capacity of reinforced concrete box ribbed arch bridge based on dynamic load test

Dynamic load test is to measure the natural vibration characteristics of the bridge structure or the forced vibration characteristics under dynamic load, and to evaluate the driving performance, driving safety and comfort of the bridge through dynamic load test. In order to evaluate the stress state and working performance of a reinforced concrete box-ribbed arch bridge, the load test of the bridge is carried out. Dynamic load test is used to test the inherent fundamental frequency, damping ratio and impact coefficient of the bridge through pulsation test and sports car test. Through the experiment with the key parts of the stress (strain) and displacement load and other important data, through analysis and study, the comprehensive analysis of the phenomenon of calculation and test, a comprehensive performance evaluation structure and function whether meet the design requirements, to provide technical basis for the safety of the bridge operation, and provide the original material for the bridge maintenance and management in the future.

Evaluation of bearing capacity of a beam on an elastic foundation using the methods of the theory of limiting balance

The analytical expressions and graphs for determining a limiting load have been obtained using the methods of the theory of limiting balance. The processes of strain of the beams after formation of a plastic hinge until their complete destruction have been investigated. The dependences of a bearing capacity of the beam on its parameters and characteristics of the foundation soils have been obtained. The regularities of formation of plastic hinges have been revealed depending on a place of application of the load. The limiting values of the load have been calculated analytically, and the forms of deformation of the beam have been established at the time of the appearance of the first plastic strains and in the limiting state. The comparative analysis of the research results of the adopted model with the numerical studies of the elastoplastic beam has been carried out.

Evaluation of bearing capacity of reinforced concrete box ribbed arch bridge based on static load test

In order to evaluate the stress and working performance of a reinforced concrete box-ribbed arch bridge after completion, the load test of the bridge is carried out. Static load test is to test the stress and displacement of each section of arch rib under the action of partial load and medium load. Through the experiment with the key parts of the stress (strain) and displacement load and other important data, through analysis and study, the comprehensive analysis of the phenomenon of calculation and test, a comprehensive performance evaluation structure and function whether meet the design requirements, to provide technical basis for the safety of the bridge operation, and provide the original material for the bridge maintenance and management in the future.

Semianalytical Solution for Evaluating Bearing Capacity of a Footing Adjacent to a Slope

Abstract The study of the influence of foundations, placed adjacent to slopes, on the bearing capacity is of great importance in geotechnical engineering. The available analytical and empirical met...

Regional Geotechnical Mapping Employing Kriging on Electronic Geodatabase

A regional geotechnical map was developed by employing kriging using spatial and s geostatistical analysis tools. Many studies have been carried out in the field of topography, digital elevation modeling, agriculture, geological, crop, and precipitation mapping. However, no significant contribution to the development of geotechnical mapping has been made. For the appraisal of a geotechnical map, extensive field explorations were carried out throughout the geotechnically diversified plateau spread over an area of approximately 23,000 km2. In total, 450 soil samples were collected from 75 data stations to determine requisite index properties and soil classification for the subsequent allowable bearing capacity evaluation. The formatted test results, along with associated geospatial information, were uploaded to ArcMap, which created an initial input electronic database. The kriging technique of geostatistical analysis was determined to be more feasible for generating a geotechnical map. The developed map represents the distribution of soil in the region as per the engineering classification system, allowable bearing capacity, and American Association of State Highway and Transportation Officials (AASHTO) subgrade rating for 1.5-, 3.0-, and 4.5-m depths. The accuracy of the maps generated using kriging interpolation technique under spatial analyst tools was verified by comparing the values in the generated surface with the actual values measured at randomly selected validation points. The database was primarily created for the appraisal of geotechnical maps and can also be used for preliminary geotechnical investigations, which saves the cost of soil investigations. In addition, this approach allows establishing useful correlations among the geotechnical properties of soil.

A Full-Scale Experimental Study of the Vertical Dynamic and Static Behavior of the Pier-Cap-Pile System

The bearing capacity evaluation of bridge substructures is difficult as the static loading test (SLT) cannot be employed for the bridges in services. As a type of dynamic nondestructive test technique, the dynamic transient response method (TRM) could be employed to estimate the vertical bearing capacity when the relationship between static stiffness and dynamic stiffness is known. The TRM is usually employed to evaluate single piles. For the pier-cap-pile system, its applicability should be investigated. In the present study, a novel full-scale experimental study, including both TRM test and SLT, was performed on an abandoned bridge pier with grouped pile foundation. The test included three steps: firstly, testing the intact pier-cap-pile system; then, cutting off the pier and testing the cap-pile system; finally, cutting off the cap and testing the single pile. The TRM test was repeatedly performed in the above three steps, whereas the SLT was only performed on the cap-pile system. Based on the experimental results, the ratio of dynamic and static stiffness of the cap-pile system was obtained. The results show that (1) in the low-frequency range (between 10 and 30 Hz in this study), the dynamic stiffness of the whole system is approximately four times of that of a single pile; (2) the ratio of dynamic and static stiffness of the cap-pile system tested in the study is approximately 1.74, which was similar to other tested values of a single pile; (3) to evaluate the capacity of similar cap-pile system and with similar soil layer conditions by TRM, the value of Kd/Ks tested in the study can be used as a reference.

Prediction of Structural Performance of Vinyl Ester Polymer Concrete Using FEM Elasto-Plastic Model.

This paper presents the methodology for predicting the mechanical performance of structural elements made of polymer concrete (PC). A vinyl ester polymer concrete composition and the results of experimental studies to determine the basic mechanical properties of the material are presented. Following the strategy for sustainable development in the building industry, the material cost of polymer concrete was lowered by reducing the consumption of raw materials and the partial replacing of the microfiller fraction with recycled waste products—calcium fly ash. An accurate computational model enabling stress analysis is a convenient way to verify the suitability of PC as a construction material in structural applications. Due to difficulty in deriving an accurate analytical formula, numerical approximation (finite element method) was used as a method for solving the problem. Constitutive modeling of PC is a very important aspect of the strength calculations and here it was done within the framework of elasto-plasticity. Numerical evaluation of the static bearing capacity of PC manhole covers is shown as an example of the proposed FEM methodology. The results of computer simulations were compared with laboratory tests. Finally, the adequacy of the numerical modeling for testing new construction and material improvements is discussed. The study showed that the concrete damaged plasticity material model can be effectively used for the description of PC mechanical behavior.

Evaluation of Ultimate Bearing Capacity of Pre-Stressed High-Strength Concrete Pipe Pile Embedded in Saturated Sandy Soil Based on In-Situ Test

Estimation of ultimate bearing capacity (UBC) of pre-stressed high-strength concrete (PHC) pipe pile is critical for optimizing pile design and construction. In this study, a standard penetration test (SPT), static cone penetration test (CPT) and static load test (SLT) were carried out to assess, determine and compare the UBC of the PHC pipe pile embedded in saturated sandy layers at different depths. The UBC was calculated with three methods including the JGJ94-2008 method, Meyerhof method and Schmertmann method based on in-situ blow count (N) of SPT (SPT-N) which was higher than the values recommended in survey report regardless of pile length. The average UBC values calculated with cone-tip resistance and sleeve friction from CPTs was also higher than the value recommended in the survey report. Moreover, the actual UBC values directly obtained by load-displacement curves from SLTs were in line with the calculated values based on in-situ SPTs and CPTs, but approximately twice as high as the values recommended in the survey report regardless of pile length. For the SPT method, the application of bentonite mud in saturated sand layers is critical for the assessment of pile capacity in the survey phase, CPTs can provide reliable results regardless of soil characteristics and groundwater if the soil layer can be penetrated, and SLTs are necessary to accurately determine the UBC in complex stratum.

Pseudo-static Seismic Bearing Capacity of Shallow Foundations in Unsaturated Soils Employing Limit Equilibrium Method

There exist many structures founded on unsaturated soil deposits. Shear strength augmentation due to the evolution of the matric suction within the unsaturated porous media enhances the bearing capacity of the overlying foundation. This paper presents the evaluation of the pseudo-static seismic bearing capacity of the shallow foundations resting on unsaturated soil deposits using limit equilibrium method. Adopting the Coulomb failure mechanism and Bishop effective stress concept, the bearing capacity equations are solved. The distribution of the matric suction beneath the footing is assumed to be linear. The results of the bearing capacity evaluation are validated against some experimental data found in literature for the static condition. For the seismic loading consideration, the pseudo-static method is utilized. The dual effect of the earthquake acceleration vertical component is thoroughly discussed and a suction transition point is introduced in which the minimum bearing capacity is observed to bear the same value for both upward and downward directions. The increase in the matric suction throughout the soil deposit leads to the increase in the soil shear strength, thus posing more resisting forces as well as higher ultimate bearing capacity. The offered solution is deemed a consistent and useful tool for the accurate prediction of the seismic bearing capacity of shallow footings resting on unsaturated soil deposits.

Static Load Test interpretation methods of pile base capacity approximation for design of wind turbine deep foundation

The bearing capacity of a pile is mainly assessed from a static load test, which is widely considered as the most reliable method of pile testing. The test provides important information about pile behaviour in a subsoil, but often for more precise data it should be performed on additionally instrumented piles. With specially prepared pipe piles static load tests can be performed with a load applied only to a pile base. The results of this test allow on an evaluation only of pile base bearing capacity, although it often requires an application of some of the methods dedicated to analyse the static load test results. In paper some of the methods for evaluation bearing capacity of a pile from a static load test are introduced. Evaluation of pile base bearing capacity by different methods was compared using results of static load tests with a load applied only to the pile base. A discussion of results and future recommendations were also presented.

Evaluation of bearing capacity of reinforced stone arch bridge based on dynamic load test

In order to evaluate the stress and working performance of a reinforced stone arch bridge, the load test of the bridge is carried out. Dynamic load test is used to test the inherent fundamental frequency, damping ratio and impact coefficient of the bridge through pulsation test and sports car test. Under the dynamic load, the first vertical natural vibration frequency of the bridge is 5.005, the damping ratio is 0.203, the second vertical natural vibration frequency of the bridge is 6.274, the damping ratio is 0.021, the tested strain impact coefficient is between 1.03 and 1.10, the measured vertical fundamental frequency is greater than the calculated fundamental frequency, and the overall stiffness of the bridge meets the design specification. The test results show that the reinforcement method of thickening the main arch ring has good application value, can effectively improve the service level of the old bridge and prolong the safety service life, and has obvious social and economic benefits.

Evaluation of bearing capacity of reinforced stone arch bridge based on static load test

In order to evaluate the stress and working performance of a reinforced stone arch bridge, the load test of the bridge is carried out. Static load test is to test the stress and displacement of each section of the main arch ring under the action of partial load and medium load. The results show that under the action of various loads, the check coefficients of deflection and strain of this bridge do not exceed the specification limit of 1.0 of masonry arch bridge, the actual working performance of the structure is good, the maximum value of relative residual strain and relative residual deformation are 11.11% and 8.21% respectively, and they do not exceed the standard allowable value of 20%, and the whole bridge is in the elastic deformation stage. The test results show that the reinforcement method of thickening the main arch ring has good application value, can effectively improve the service level of the old bridge and prolong the safety service life, and has obvious social and economic benefits.

Study on the destructive test of T-beam strengthened by external prestressing

Three T-beams with severe cracks in the operation were selected for the approach bridge of the Yellow River Bridge of a national highway. Three pieces of external T-beams were used for reinforcement and the destructive tests were carried out on the strengthened T-beams. The test results of the T-beam test of the approach bridge are analyzed to evaluate the bearing capacity. The main conclusions are as follows: The strengthened T-beam has greatly improved the mechanical performance, improved the cracking load of the T-beam, and slowed the crack development. The change of beam deflection is divided into three stages: 0~30t, 30~66t, 66~134t. The deflection value increases gradually, and the turning point of deflection changes basically corresponds to the crack development. The stiffness and ultimate load carrying capacity of the T-beam are greatly improved, which greatly improves the safety of the T-beam. Due to the lack of space at the bottom of the beam, the test beams of the three pieces of reinforcement were loaded to the final failure, and the maximum crack width has reached the loading termination condition. This indicates that the elastic stress stage of the T beam is increased after the reinforcement, and the T beam has a strong T-beam. Deformation recovery capability. It provides some reference for the reinforcement and transformation of similar T-beams and the evaluation of bearing capacity.

On determining the undrained bearing capacity coefficients of variation for foundations embedded on spatially variable soil

Abstract This paper presents an efficient method and its usage for the three-dimensional random bearing capacity evaluation for square and rectangular footings. One of the objectives of the study is to deliver graphs that can be used to easily estimate the approximated values of coefficients of variations of undrained bearing capacity. The numerical calculations were based on the proposed method that connects three-dimensional failure mechanism, simulated annealing optimization scheme and spatial averaging. The random field is used for describing the spatial variability of undrained shear strength. The proposed approach is in accordance with a constant covariance matrix concept, that results in a highly efficient tool for estimating the probabilistic characteristics of bearing capacity. As a result, numerous three-dimensional simulations were performed to create the graphs. The considered covariance matrix is a result of Vanmarcke’s spatial averaging discretization of a random field in the dissipation regions to the single random variables. The matrix describes mutual correlation between each dissipation region (or between those random variables). However, in the presented approach, the matrix was obtained for the expected value of undrained shear strength and keep constant during Monte Carlo simulations. The graphs were established in dimensionless coordinates that vary in the observable in practice ranges of parameters (i.e., values of fluctuation scales, foundation sizes and shapes). Examples of usage were given in the study to illustrate the application possibility of the graphs. Moreover, the comparison with the approach that uses individually determined covariance matrix is shown.

Characteristic analysis on the compression-bending capacity of segmental joint based on the investigated joint parameters

The compression-bending capacity, also known as compressive membrane action, is an important mechanical property of segmental joints. However, owing to a lack of validated calculation methods and quantitative analysis of joint parameters, it has not been applied in the design of segmental joints. Thus, based on a method for calculating the compression-bending capacity of segmental joints proposed previously and joint parameters investigated from a number of practical engineering projects, the characteristic shapes and points of the compression-bending capacity curve are obtained, and the influence of joint parameters on the bearing capacity of segmental joints are quantitatively analyzed. The results show that the compression-bending capacity curve for a segmental joint is a parabolic curve, which can be divided into two parts (parts I and II), where the demarcation point between parts I and II represents that bolt yielding and concrete failure happen at the same time. There are five characteristic points on the curve, based on which four different stress states of the bolt are defined, different characteristic points have different sensitivity to the changes in the joint surface parameters, but the largest changes are all more than double. The influence of segment width and concrete strength on the compression-bending capacity of segmental joints is integral and varies widely, while the influence of the bolt parameters is mainly reflected in small changes at lower axial pressures. The results of this study can provide support and guidance for the design and bearing capacity evaluation of segmental joints.

Analysis of Human-Land Coupled Bearing Capacity of Qiangtang Meadow in Northern Tibet Based on Fuzzy Clustering Algorithm

Aiming to address the problems of high energy consumption, low efficiency, low correlation between the analyzed and actual results, and poor rationality of research indexes in current methods of analysis of human-land coupled bearing capacity of meadows, a novel method of human-land coupled bearing capacity analysis of Qiangtang meadow in northern Tibet, based on fuzzy clustering algorithm, is proposed. Basic geographic information data in Tibet were acquired, the collected data images were registered by ENVI4.2 software, and the collected data were vectorized by ArcGIS 9.3 software to construct a basic geographic information database in Tibet. Based on the frequency domain processing algorithm, the geographic information image was suppressed by noise and filtered by using a high-pass filter to realize the geographic information data processing in the study area. The human-land coupled bearing capacity analysis of Qiangtang meadow in northern Tibet was evaluated through fuzzy clustering, bearing capacity evaluation, and bearing capacity calculation under the sharing of closure. The experimental results showed that the average running energy consumption of the method was 81 J, and 97% of the analyzed results were consistent with the actual situation. These results indicate that the operation efficiency of the method is high, and the rationality coefficient of the research index is large. The proposed method has superior performance and feasibility.

Evaluation of Geological and Ecological Bearing Capacity and Spatial Pattern along Du-Wen Road Based on the Analytic Hierarchy Process (AHP) and the Technique for Order of Preference by Similarity to an Ideal Solution (TOPSIS) Method

As China is a mountainous country, a large quantity of the population has to live in mountainous areas due to limited living space. Most of them cluster along roads in areas with relatively poor traffic conditions. In view of the spatial-temporal change of complex geological and ecological environment along the roads in the mountains, this paper takes the Dujiangyan- Wenchuan (Du-Wen) Road as the research object, and puts forward a method to evaluate the bearing capacity of regional geological and ecological environment based on the evaluation of quality and spatial coupling of bearing capacity. For the needs of the current research, a total number of 20 indicators from three aspects of geological, ecological, and social attributes were selected to carry out the assessment. Based on the GIS platform and evaluation index system, the weight of each evaluation index factor is determined by Analytic Hierarchy Process (AHP). The comprehensive quality of bearing capacity is calculated by the Technique for Order of Preference by Similarity to an Ideal Solution (TOPSIS) algorithm through weighted superposition, which comes to result in the evaluation of geological, ecological, and social environment. Afterward, the bearing capacity of the study area is classified, combining the results of hot spot analysis. The study shows that the spatial distribution of geological, ecological, and socio-economic bearing capacity in this area is highly aggregated, with 31.12% of the area to be classified as suitable construction area, 31.98% as backup reserve area, and 36.79% as unsuitable construction area. The studied triangle area, composed of Yingxiu Town, Xuankou Town, and Dujiangyan City, presents a large area of a high-valued aggregation area, with comprehensive high quality bearing capacity and spatial aggregation, which is better for planning and construction.

Inspection and Monitoring of Concrete Structures via Radiography and Weighted Nuclear Norm Minimization Method

The location of reinforcement bar in concrete, the bar corrosion, diameter and the depth below the surface are important factors in the evaluation of the load bearing capacity and the usage property within the scope of building condition and damage analysis. Radiographic techniques are used to examine the structure of different buildings. The basic goal of the inspection is the visualization of reinforcement bars, fittings or tension cables. In this research, the Weighted Nuclear Norm Minimization method was used to improve visualization of the hidden structures and defects from the concrete radiographs. The method relies on minimization of the image energy and singular value decomposition for enhancing contrast. The proposed algorithm was successfully applied to radiographic images of concrete segments. Improvement of the structure detail visualization and defect region detection were achieved while preserving structure edge and fine detail imaging information. Evaluation of the image quality enhancement showed that the contrast level to noise increases by a factor of about two in reconstructed images using the proposed method. Also, the background is suppressed towards the zero baselines, and better visual quality is achieved.