Reliability-based design of deep foundations based on differential settlement criterion

2009 ◽  
Vol 46 (2) ◽  
pp. 168-176 ◽  
Author(s):  
Lance A. Roberts ◽  
Anil Misra
Keyword(s):  
Soil Structure ◽  
Load Capacity ◽  
Limit State ◽  
Interaction Model ◽  
Differential Settlement ◽  
Model Parameters ◽  
Deep Foundations ◽  
Deep Foundation ◽  
Reliability Based Design ◽  
Service Limit State

Load–displacement analysis of a single deep foundation element can be accomplished by utilizing a soil–structure interaction model, such as the “t–z” model. By combining the soil–structure interaction model with a probabilistic analysis technique, such as Monte Carlo simulation, methods to rationally incorporate variability in the model parameters can be developed. As a result, the service limit state load capacity of a single deep foundation element can be computed for an allowable total head displacement. However, in design, differential settlement between individual foundation elements is often the event of interest. This paper develops a reliability-based design methodology for deep foundations based on a differential settlement design criterion. The design methodology is developed for various levels of uncertainty in the model parameters. The results are presented in the form of cumulative distribution functions that, combined with the calculated service limit state load capacity, form the basis for serviceability design of deep foundations based on a differential settlement criterion.

Geotechnical resistance factors for ultimate limit state design of deep foundations in cohesive soils

2011 ◽  
Vol 48 (11) ◽  
pp. 1729-1741 ◽  
Author(s):  
Mehrangiz Naghibi ◽  
Gordon A. Fenton
Keyword(s):  
Limit State ◽  
Cohesive Soil ◽  
Ultimate Limit State ◽  
Deep Foundations ◽  
Cohesive Soils ◽  
Deep Foundation ◽  
Resistance Factors ◽  
Limit State Design ◽  
Ultimate Limit State Design ◽  
Ultimate Limit

This paper investigates the ultimate limit state load and resistance factor design (LRFD) of deep foundations founded within purely cohesive soils. The geotechnical resistance factors required to produce deep foundation designs having a maximum acceptable failure probability are estimated as a function of site understanding and failure consequence. The probability theory developed in this paper, used to determine the resistance factors, is verified by a two-dimensional random field Monte Carlo simulation of a spatially variable cohesive soil. The agreement between theory and simulation is found to be very good, and the theory is then used to derive the required geotechnical resistance factors. The results presented in this paper can be used to complement current ultimate limit state design code calibration efforts for deep foundations in cohesive soils.

scholarly journals Analysis of soil-structure interaction in buildings with deep foundation

2020 ◽  
Vol 13 (2) ◽  
pp. 248-273
Author(s):  
M. G. RITTER ◽  
M. L. MENEGOTTO ◽  
M. F. COSTELLA ◽  
R. C. PAVAN ◽  
S. E. PILZ
Keyword(s):  
Global Stability ◽  
Soil Structure ◽  
Soil Structure Interaction ◽  
Deep Foundations ◽  
Reinforced Concrete Structures ◽  
Commercial Building ◽  
Computational Simulations ◽  
Global Instability ◽  
Deep Foundation ◽  
Structure Interaction

Abstract In this paper it is presented how the influence of soil-structure interaction (SSI) interferes on reinforced concrete structures in small buildings with deep foundations, with the objective of analyzing the influence of SSI on the loads and repressions, global stability and costs of materials. The analysis were based on numerical-computational simulations of a commercial building using CAD/TQS commercial software. The building was simulated with 4, 6 and 8 floors with 3 different profiles of soils, generating 8 case studies. When considering SSI, the loads and repressions did not present significant variations and the parameters of global instability were within the normative recommendations. Among the variables analyzed, the material cost of the structure was the least affected item with the SSI consideration.

Probabilistic analysis of drilled shaft service limit state using the "t–z" method

2006 ◽  
Vol 43 (12) ◽  
pp. 1324-1332 ◽  
Author(s):  
Anil Misra ◽  
Lance A Roberts
Keyword(s):  
Limit State ◽  
Drilled Shafts ◽  
Cumulative Distribution ◽  
Hyperbolic Model ◽  
Drilled Shaft ◽  
Large Set ◽  
Reliability Based Design ◽  
Service Limit State ◽  
Load Displacement ◽  
Load And Resistance Factor

The utility of the load and resistance factor design (LRFD) approach is being increasingly recognized for the design of drilled shafts. The current LRFD methodologies of drilled shaft design would be more efficient if reliability based design approaches were used for service limit state design. In this paper, the "t–z" methodology is utilized to develop probabilistic approaches for axial service limit state analysis of drilled shafts. Two different models of the soil–shaft interaction are implemented for load displacement calculations: (1) an ideal elastoplastic model, and (2) a hyperbolic model. For both of these soil–shaft interactions, Monte Carlo simulation is used to obtain a large set of load–displacement curves assuming lognormal distributions for the shaft–soil interface properties. The load–displacement curves are analyzed to develop two alternate methods for determining the probability of drilled shaft failure at the service limit state. As a result, cumulative distribution histograms are developed for drilled shaft load capacities at allowable head displacements. These results may be utilized to obtain resistance factors that can be applied to LRFD based service limit state design.Key words: drilled shaft, serviceability, failure probability, load displacement relation, "t–z" method.

scholarly journals RECALQUES EM FUNDAÇÕES PROFUNDAS – ANÁLISE EM ESTACAS HÉLICE CONTÍNUA

2017 ◽  
Vol 14 (1) ◽  
Author(s):  
Pedro Lucas Prununciati ◽  
Jean Rodrigo Garcia ◽  
Tiago Garcia Rodriguez
Keyword(s):  
Sampling Error ◽  
Load Capacity ◽  
Limit State ◽  
Load Test ◽  
Limiting Factor ◽  
Deep Foundations ◽  
Slow Type ◽  
Load Tests ◽  
Penetration Tests ◽  
The City

RESUMO:  O recalque em fundações profundas e sua influência numa edificação tem se mostrado um parâmetro crítico, já que em diversos projetos a capacidade de carga não é o fator limitante, mas sim o recalque que a estrutura pode suportar em seu estado limite de serviço (ELS). Neste trabalho, são analisados resultados de deslocamento para uma estaca, estimados a partir dos métodos de Poulos e Davis (1980), Vésic (1969, 1975a) e Cintra e Aoki (2010), comparando-os com o valor recalque obtido por ensaios de prova de carga. Para tal, se apresentam três ensaios com carregamento do tipo lento, seguindo instruções da NBR12131 (ABNT, 2006), executados em estacas hélice contínua instrumentadas, com comprimentos de 14,75 m, 12,85 m e 21,80 m e diâmetros de 70 cm, 60 cm e 70 cm, respectivamente. Essas estacas foram ensaiadas no munícipio de Itatiba, em uma região onde sondagens à percussão demonstram a predominância de areia e silte. Para as estacas analisadas, o método proposto por Cintra e Aoki (2010) mostrou melhor resultado para a estimativa do recalque, quando comparado aos resultados de recalque obtidos em prova de carga. O método Poulos e Davis (1980) obteve desempenho menos satisfatório, resultando uma margem de erro de 16%, para mais ou para menos. O método de Vésic (1969, 1975a) se mostrou conservador e, nos casos analisados, resultou uma superestimativa de 138%, quando comparados aos valores de prova de carga.ABSTRACT: The settlement in deep foundations and its influence appears to be a critical parameter, as in many projects, the load capacity of a pile is not the limiting factor, but the settlement which the structure can suffer on its serviceability limit state (SLS) is. In this research, the settlement results of a pile, estimated by the methods of Poulos e Davis (1980), Vésic (1969, 1975a) and Cintra e Aoki (2010) will be analyzed, to be compared with the value of settlement obtained from load tests. Three slow type load tests, following the instructions of NBR12131 (ABNT, 2006) are presented, carried out in instrumented continuous flight augers, with lengths of 14,75 m, 12,85 m and 21,80 m and diameters of 70 cm, 60 cm and 70 cm, respectively. Those piles were tested in the city of Itatiba, in a region where standard penetration tests evidenced the predominance of sand and silt. In the analyzed piles, the Cintra e Aoki (2010) method has shown the best result for a settlement estimate, when compared with the value obtained by a load test. The Poulos e Davis method (1980) obtained a less satisfactory performance, resulting a margin of sampling error of plus or minus 16%. The Vésic method (1969, 1975a) has shown to be conservative, resulting, in the analyzed cases, an overestimate of 138%, when compared with the load tests values.

Evaluation of model uncertainties in reliability-based design of steel H-piles in axial compression

2018 ◽  
Vol 55 (11) ◽  
pp. 1513-1532 ◽  
Author(s):  
Chong Tang ◽  
Kok-Kwang Phoon
Keyword(s):  
Axial Compression ◽  
Limit State ◽  
Load Test ◽  
Hyperbolic Model ◽  
Ultimate Limit State ◽  
Model Uncertainties ◽  
Deep Foundation ◽  
Mean Values ◽  
Reliability Based Design ◽  
Load Tests

To account for uncertainties of load and resistance in a more rational way, reliability-based design (RBD) concepts have been increasingly applied to design bridge foundations. One of critical elements in the geotechnical RBD process is the characterization of model uncertainties. This paper compiles 126 and 23 reliable static load tests for steel H-piles in axial compression from two databases: Pile-Load Tests (PILOT) and Deep Foundation Load Test Database (DFLTD), respectively. The Davisson offset limit is adopted to define the measured resistance in clay, sand, and layered soil, which is verified with the L1–L2 method developed for drilled shafts. A hyperbolic model with two parameters is chosen to fit the measured load–settlement curves. The uncertainties in resistance calculations and the load–settlement curves are captured by a ratio (or model factor) of measured to calculated resistance and the hyperbolic parameters. The mean values, coefficients of variation, and the probability distributions of the model factors are established from 149 load tests. The statistics of the resistance model factor are applied to calibrate the resistance factors (for the ultimate limit state) in load and resistance factor design of steel H-piles in axial compression. In future, the statistics of the hyperbolic parameters can be incorporated into the development of RBD of steel H-piles at the serviceability limit state.

Load Testing to Collapse Limit State of Barr Creek Bridge

2000 ◽  
Vol 1696 (1) ◽  
pp. 92-102 ◽  
Author(s):  
Nicholas Haritos ◽  
Anil Hira ◽  
Priyan Mendis ◽  
Rob Heywood ◽  
Armando Giufre
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Flexural Rigidity ◽  
Load Capacity ◽  
Limit State ◽  
Dynamic Test ◽  
Service Condition ◽  
Flat Slab ◽  
Testing Program ◽  
Static Testing

VicRoads, the road authority for the state of Victoria, Australia, has been undertaking extensive research into the load capacity and performance of cast-in-place reinforced concrete flat slab bridges. One of the key objectives of this research is the development of analytical tools that can be used to better determine the performance of these bridges under loadings to the elastic limit and subsequently to failure. The 59-year-old Barr Creek Bridge, a flat slab bridge of four short continuous spans over column piers, was made available to VicRoads in aid of this research. The static testing program executed on this bridge was therefore aimed at providing a comprehensive set of measurements of its response to serviceability level loadings and beyond. This test program was preceded by the performance of a dynamic test (a simplified experimental modal analysis using vehicular excitation) to establish basic structural properties of the bridge (effective flexural rigidity, EI) and the influence of the abutment supports from identification of its dynamic modal characteristics. The dynamic test results enabled a reliably tuned finite element model of the bridge in its in-service condition to be produced for use in conjunction with the static testing program. The results of the static testing program compared well with finite element modeling predictions in both the elastic range (serviceability loadings) and the nonlinear range (load levels taken to incipient collapse). Observed collapse failure modes and corresponding collapse load levels were also found to be predicted well using yield line theory.

Dependency of Machine Efficiency on the Thermal Behavior of Induction Machines

Machines ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 9
Author(s):  
Svenja Kalt ◽  
Karl Ludwig Stolle ◽  
Philipp Neuhaus ◽  
Thomas Herrmann ◽  
Alexander Koch ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Electric Vehicles ◽  
Thermal Load ◽  
Load Capacity ◽  
Maximum Load ◽  
Induction Machines ◽  
Electric Machines ◽  
Model Parameters ◽  
Dynamic Operating ◽  
The Impact

The consideration of the thermal behavior of electric machines is becoming increasingly important in the machine design for electric vehicles due to the adaptation to more dynamic operating points compared to stationary applications. Whereas, the dependency of machine efficiency on thermal behavior is caused due to the impact of temperature on the resulting loss types. This leads to a shift of efficiency areas in the efficiency diagram of electric machines and has a significant impact on the maximum load capability and an impact on the cycle efficiency during operation, resulting in a reduction in the overall range of the electric vehicle. Therefore, this article aims at analyzing the thermal load limits of induction machines in regard to actual operation using measured driving data of battery electric vehicles. For this, a thermal model is implemented using MATLAB® and investigations to the sensitivity of model parameters as well as analysis of the continuous load capacity, thermal load and efficiency in driving cycles under changing boundary conditions are conducted.

Experimental Validation of a Volumetric Planetary Rover Wheel/Soil Interaction Model

2013 ◽  
Author(s):  
Willem Petersen ◽  
John McPhee
Keyword(s):  
Contact Force ◽  
Interaction Model ◽  
Contact Model ◽  
Soil Parameters ◽  
Model Parameters ◽  
Force Model ◽  
Normal Contact ◽  
Planetary Rover ◽  
Normal Contact Force ◽  
Contact Force Model

For the multibody simulation of planetary rover operations, a wheel-soil contact model is necessary to represent the forces and moments between the tire and the soft soil. A novel nonlinear contact modelling approach based on the properties of the hypervolume of interpenetration is validated in this paper. This normal contact force model is based on the Winkler foundation model with nonlinear spring properties. To fully define the proposed normal contact force model for this application, seven parameters are required. Besides the geometry parameters that can be easily measured, three soil parameters representing the hyperelastic and plastic properties of the soil have to be identified. Since it is very difficult to directly measure the latter set of soil parameters, they are identified by comparing computer simulations with experimental results of drawbar pull tests performed under different slip conditions on the Juno rover of the Canadian Space Agency (CSA). A multibody dynamics model of the Juno rover including the new wheel/soil interaction model was developed and simulated in MapleSim. To identify the wheel/soil contact model parameters, the cost function of the model residuals of the kinematic data is minimized. The volumetric contact model is then tested by using the identified contact model parameters in a forward dynamics simulation of the rover on an irregular 3-dimensional terrain and compared against experiments.

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