Load Test Data Research Articles

Comparison of a Contact Mechanics Model With Experimental Results to Optimize the Prediction of Transverse Load Effects of Large Superconducting Cable-In-Conduit-Conductor

A model based on contact mechanics concepts has been developed to analyze and quantitatively evaluate mechanical transverse load effects on superconducting strands in a cable-in-conduit-conductor (CICC). The model estimates the number of contact points and the effective contact pressures between the strands in a cable. Experimental measurements confirmed the model, which was then used to evaluate mechanical transverse load effects on the critical current degradation of sub-sized cable samples of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires. It is proposed to use a set of experimental transverse load test data of the smallest stage cable (triplet) in order to predict transverse load degradations of the critical current of a large full size CICC cable. This paper will review the model to estimate the degradation caused by the transverse load effect and discuss the results of several cable configurations. The analysis provides suggestions for future design evaluation of mechanical behaviors of large Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CICC magnets during operations.

Experimental Study on Bearing Behavior of Large-Diameter Overlength Cast-in-Place Bored Pile Post-Grouting

The bearing capacity property of large-diameter bored cast-in-situ deep and post-grouting pile is analyzed on the basis of measuring data of static load test and axial stress measure data. The study indicates that the large-diameter bored cast-in-situ deep and post-grouting pile show the characteristics of the friction when the bearing course at pile end is sand, when the pile top load is greater than 18000kN, the pile end begin to resistance and the share proportion is small, only 1% to 10%; the load settlement cure is gradual decline, no inflection point, the settlement of pile compression only accounted for about 15%, The developing degree of side resistance is well corresponding to the relative displacement between pile and soil. The side resistances significantly enhance effect, the measured value of the soil side resistance is 1.3 to 1.5 times of survey report recommended.

EVALUATION OF SIDE RESISTANCE CAPACITY FOR DRILLED SHAFTS

This paper presents an extensive evaluation of axial side resistance of drilled shaft foundations. A wide variety of load test data are used and these data are divided into drained and undrained databases. Representative analytical models, including alpha (α), beta (β), and lambda (λ) methods, are examined in detail using both measured and predicted results to assess their relative merits for the drilled shaft design. Based on these analyses, the undrained shear strength (α-s(subscript μ)) correlations have exhibited better statistics for undrained side resistance prediction, and the undrained strength ratio (α-USR) correlations can be adopted as an alternative analytical method, especially in the case of smaller s(subscript μ). For β method, the stress factors (K/K(subscript o)) are developed from the back-analysis of field load tests. However, the β method has presented more varying results for short shafts in both drained and undrained loading. Among all analytical methods, the λ method is relatively the less reliable prediction model. Specific design recommendations for side resistance analysis of drilled shaft are suggested.

Evaluation of lateral interpretation criteria for rigid drilled shafts

Representative criteria are examined to evaluate the “interpreted failure load” or “capacity” of rigid drilled shaft foundations under lateral loading. Field lateral load test data are used for this analysis, consisting of both drained and undrained databases. It was found that a hyperbola describes the load–displacement data well and that the normalized undrained curve is stiffer, higher, and more sharply curving than the drained curve. The initial elastic region ends at approximately 1%B (where B is the shaft diameter),which represents serviceability limit state (SLS) conditions. The final region begins at about 4%–5%B, which represents ultimate limit state (ULS) conditions. Also, the QLmethod is most appropriate for interpreting the “failure load” because it is the only method that incorporates actual soil-shaft failure mechanisms as part of the interpretation, is the least variable, and has the lowest coefficient of variation (COV). Further detailed recommendations are given for assessing the load test data.

LRFD Resistance Factors for Design of Driven H-Piles in Layered Soils

The load and resistance factor design (LRFD) of piles embedded in layered soils that are commonly classified as sand, clay, and mixed soil sites is investigated using static analysis methods at the strength limit state. Unlike the current practice, the main emphasis of this study is to use a more clearly defined, less ambiguous classification for the sites based on the percentage of soil types present along the pile embedment length. Two different site classifications and the corresponding LRFD resistance factors are recommended for different static methods, used during the pile design stage, in accordance with the AASHTO-LRFD calibration framework. For this purpose, a total of 90 high-quality static load tests data obtained from steel H-piles were used, including 10 load tests conducted recently on heavily instrumented steel H-piles. The new group of data facilitated verification of the proposed methods, which were first developed based on the 80 load test data and then updated based on the entire 90 pile tests. In addition to a locally developed static method known as the Bluebook approach, several commonly adopted static analysis approaches, as well as combinations of methods, have been examined with due consideration to soil variation along the pile length. The investigation found that (1) the Bluebook method consistently provided higher resistance and efficiency factors, (2) using a 70% rule is an appropriate means to define the soil type at the site while maintaining simplicity in the design approach, and (3) utilizing a more refined site classification based on the percentage of cohesive versus cohesionless soils existing along the pile embedded length further enhanced the LRFD approach for pile foundations.

Suspended Load Prediction on Sucker Rod Suspension Load Based on Artificial Neural Network

Using the test data of suspendsion load on socker rod from oilfield database, a prediction model is presented, which adapted the improved L-M neural network algorithm and explored the 6 effect factors’ relationship: the rod stroke, frequency of strokes, rod diameter, pump diameter, submergence depth and pump setting depth. With training the model,and higher training accuracy is acquired, which shows using this method to predict the suspendsion load is effective.

Rectangular footing on sand subjected to double eccentric load

This paper describes the results of a series of loading tests of a rectangular footing, with an aspect ratio of two, resting on dry sand and subjected to double eccentricity in a centrifuge. The results indicate that current design practice of calculating failure load of rectangular surface footing excessively underestimates the centrifuge loading test data. This trend is more marked when the eccentricity becomes larger. The decreasing trend in failure load with an increase of double eccentricity is rather uniquely expressed by a single curve, using a newly defined resultant eccentricity and the diagonal length of the footing base. Detailed measurements of progressive change in the contact area between the footing base and the ground were made, and three-dimensional failure mechanisms were also captured and presented for future verification of three-dimensional analysis.

In Vitro Biomechanical Comparison of the Effect of Pattern, Inclination, and Size of Positional Screws on Load Resistance for Bilateral Sagittal Split Osteotomy

The purpose of this in vitro investigation was to determine whether the pattern, angle of placement, or size of positional screws affected their ability to resist vertical loads resembling mastication in the bilateral sagittal split osteotomy system. Standardized bone substitutes were secured with three 12- to 16 mm-long, 1.85-, 2.0-, 2.1-, and 2.4-mm outer diameter, self-tapping titanium screws (Synthes, Solothurn, Switzerland) in various patterns using a positional screw technique. These patterns included transbuccal triangular, intraoral triangular, and transbuccal linear patterns. The models were secured in a jig and subjected to vertical loads by a mechanical testing unit (1475 UPM; Zwick, Ulm, Germany) until failure. Loading test data analysis was based on peak load values resulting in mechanical deformation of the system (1-, 3-, and 5-mm displacement), maximal force, and stiffness (load/displacement slope curve) for each group. Means and standard deviations were derived and compared for statistical significance using univariate analysis of variance with a confidence level of 95% (P values < .05). The designed study demonstrated that 1.85- and 2.0-mm-diameter positional screws provided similar stability in all 3 setups. Three screws placed in an inverted L pattern at 90° (simulating a transbuccal approach) showed significantly higher resistance to vertical forces for advancement movements at 1-, 3-, and 5-mm displacement when compared with the inverted L group of screws placed at an angle (intraoral approach) or 3 screws in a linear pattern placed at 90° (transbuccal approach) (P < .01). Under the conditions tested in this in vitro study, differences in the load resistance of positional screws placed in a transbuccal or intraoral approach could be demonstrated depending on the fixation technique. The transbuccal group of 3 screws in an inverted L pattern showed significantly greater stability than the intraoral group of 3 screws placed in an inverted L pattern and the transbuccal group of 3 screws in a linear pattern. Resistance to vertical loads with 1.85-mm screws was similar to that with the standard 2.0-mm screws in all 3 setups. The results of this study suggest that the angle of screw placement (surgical approach) and pattern have a greater influence on the stability of the bilateral sagittal split osteotomy system than the screw size.

Bacterial Foraging Algorithm based Parameter Estimation of Three WINDING Transformer

Transformers are one of the main components of any power system. An accurate estimation of system be-haviour, including load flow studies, protection, and safe control of the system calls for an accurate equiva-lent circuit parameters of all system components such as generators, transformers, etc. This paper presents a methodology to estimate the equivalent circuit parameters of the Three Winding Transformer (TWT) using Bacterial Foraging Algorithm (BFA). The estimation procedure based on load test data at one particular op-erating point namely supply voltage, load currents, input power. The performance characteristics, such as efficiency and voltage regulation are considered along with the name plate data in order to minimize the er-ror between the estimated and measured data. The estimation procedure is demonstrated with a sample three winding transformer and the results are compared against the directly measured performance of TWT and genetic algorithm optimization results. The simulation results show the ability of the proposed technique to capture the true values of the machine parameters and the superiority of the results obtained using the bacte-rial foraging algorithm.

Method of Testing and Data Processing of Random Load Spectrum of Wheel Loader Transmission

A continuous non-stationary load spectrum of wheel loader transmission was obtained from field testing by a special test system, including time-history of torque, speed, oil pressure and gears. During the data processing, each work cycle was divided into six steps: no-load forward, shoveling, heavy-load back, heavy-load forward, unloading and no-load back with considering the characteristic of gears, torque and oil pressure signals. Discretization, Butterworth filter and the singularity rejecting were adopted to analyze the load data of each step, from which the non-stationary random signals were translated into the pure stationary load signals. The time-history load testing method and data processing of random load spectrum of transmission was presented.

Prediction of pile bearing capacity using support vector machine

This paper examines the potential of support vector machine (SVM) in prediction of bearing capacity of pile from pile load test data. In this study, SVM uses regression technique by introducing ε-insensitive loss function. The data from a pile load test has been used to build the SVM model. SVM uses penetration depth ratio (<i>l/d</i>), mean normal stress (σ_<i>m</i>), and no of blows (<i>n</i>) as input parameters. The output of SVM model is bearing capacity (<i>Q</i>) of pile. Sensitivity analysis of the develop SVM model shows that <i>l/d</i> has the most significant effect on <i>Q</i>. An equation has been also developed for the prediction of bearing capacity of pile. This study shows that SVM approach give an alternative tools to geotechnical engineers for the determination of bearing capacity of pile.

Calibrating Resistance Factors of Single Bored Piles Based on Incomplete Load Test Results

This paper addresses a problem often encountered in calibrating resistance factors for the ultimate capacities of piles based on load test databases. In practice, many pile load tests are not conducted to failure but only to a multiple (e.g., 2) of the design load. This leads to a difficult situation of incomplete information: for these test results, the ultimate bearing capacities of the test piles are unknown. How can these test results still be used to calibrate resistance factors of piles? A full probabilistic framework is proposed in this research to resolve this problem. A local pile test database of Taipei (Taiwan) is presented for demonstration. The analysis results show that the inclusion of the incomplete pile load test data enhances the stability of the calibrated resistance factors. For a target reliability index of 3, the calibrated resistance factor is in the range of 0.4–0.66 for two design models adopted in the current Taiwan design code. Moreover, it is found that the safety factor adopte...

Capacity Evaluation of a Severely Distressed and Deteriorated 50-Year-Old Box Beam with Limited Data

In 2005, 15 adjacent box-beam bridges were randomly selected and inspected to document their performance with consideration of the evolving design procedures. Longitudinal cracking along the soffit of several fascia beams was documented. After evaluating inspection data, the bridge engineer recommended the replacement of a severely distressed fascia beam from the Hawkins Road Bridge in Jackson County, Michigan. The beam was salvaged and the capacity was evaluated through load testing. The remaining prestress was 75% of the initial prestress, which is 5% less than the final prestress used for the design. Concrete modulus of elasticity was evaluated as 35.4 GPa and the nominal compressive strength as 54.4 MPa. Analysis of load test data indicated that a bridge with the beam in this distressed state is safe to operate. This is assuming that the transverse connectivity between the beams is sufficient for load distribution as envisioned in the design. The importance of identifying concealed corrosion, and quantifying material properties and load distribution is highlighted in this paper.

Role of Linear Elasticity in Pile Group Analysis and Load Test Interpretation

This paper compares linear-elastic and nonlinear pile group analysis methods through settlement analyses of hypothetical scenarios and real case studies, and elaborates on the implications for interpretation of pile load test data. Comparisons between linear-elastic and nonlinear methods justify the proposition that pile-to-pile interaction is dominated by linear elasticity, characterized by the small-strain soil stiffness. As the size of a pile group increases, nonlinearity in individual pile behavior becomes overwhelmed by the interaction effects. In such cases, similar estimates will be achieved by both linear and nonlinear methods if the soil modulus is derived from the initial tangent, rather than some secant stiffness, assessed from the load test data. The study clarifies the capabilities and limitations of linear elasticity in pile group analysis and provides guidance on pile test interpretation for analysis of pile group response.

A CPSO-SVM Model for Ultimate Bearing Capacity Determination

In this study, the CPSO-SVM models, which combine chaotic system, particle swarm optimization (PSO) and support vector machine (SVM), are presented and applied to predict the ultimate bearing capacity of shallow foundations. Chaotic mapping enjoys certainty, ergodicity and the stochastic property. Chaotic PSO (CPSO) increases the convergence rate of PSO and precision of the results through introducing chaos mapping into the particle swarm optimization algorithm. Since the selection of parameters for SVM is crucial to its performance of prediction, the CPSO is adopted to search for the optimal parameters. The proposed methods are used to predict the ultimate bearing capacity of shallow foundations based on data of load tests. Results indicate that the proposed methods can appropriately describe the relationship between ultimate bearing capacity and its affective factors, and make good predictions.

Analysis of a Distributed Grid-Connected Fuel Cell During Fault Conditions

The effect of a short circuit fault and a voltage sag fault on a distributed grid-connected solid oxide fuel cell (SOFC) is investigated in this paper. The fuel cell is modeled in Simulink and the performance is verified against experimental load testing data. Grid faults are simulated, and conclusions are drawn on the fuel cell response and the effects of the fault condition on internal fuel cell parameters.

Evaluation of Lateral Interpretation Criteria for Drilled Shaft Capacity

Representative interpretation criteria are examined to evaluate the capacity of nonrigid drilled shaft foundations under lateral loading. A wide variety of lateral load test data are used for analysis, and these data are divided into drained and undrained databases. The interpretation criteria are applied to these load test data to establish consistent lateral interpretation criteria. Among these criteria, the results are generally comparable for both drained and undrained loading. The statistical results show that the smaller the displacement or rotation is, the higher the coefficient of variation. Moreover, the undrained load test results present somehow less variability than the drained results. Based on these analyses, the relative merits and interrelationships of these criteria are established, and specific design recommendations for the interpretation of lateral drilled shaft load test are given in terms of capacity, displacement, and rotation.

Reliability-Based Code Calibration for Axial Ultimate Bearing Capacities of Single Bored Piles in Taipei Basin

ABSTRACTIn Taipei, many pile proof load tests were not conducted to failures but only to a multiple (e.g., 2) of the design load. This leads a difficulty of incomplete information: For these test results, the ultimate bearing capacities of the test piles are unknown. This paper addresses the issue of calibrating resistance factors of piles for the axial ultimate bearing capacities based on the incomplete information from these tests. A simplified probabilistic method is proposed to resolve this issue. A local pile test database of Taipei is presented, and the analysis results show that the inclusion of the incomplete pile load test data helps in calibrating the resistance factors. Moreover, it is found that the calibrated resistance factors for the axial ultimate bearing capacities are consistent to the safety factors that are adopted in the current Taiwan design code. This paper also addresses another important issue for the pile design in Taipei: the end bearing capacity in the sandstone layer is very uncertain. A maximum likelihood method is taken to identify the best estimate for this end bearing capacity. The conclusion of this paper may be useful for reliability-based designs for the axial ultimate bearing capacities of single bored piles in the Taipei region.

Investigation of the Accuracy of the Dynamic Methods of Capacity Estimation of Piles

Capacity estimation of piles using dynamic methods is considered in this paper. Commonly used dynamic methods in Sri Lanka, high strain dynamic load testing and pile driving equations are considered in detail. The accuracy of the CAPWAP method of capacity prediction was discussed considering the results of the available comparison studies. Considering the CAPWAP predicted capacities and the capacities estimated from the Case method, the applicability, of the commonly used Case damping factor of 0.5 was investigated. Furthermore, Case damping factors to be used in the field high strain dynamic load testing are also suggested. The capacities estimated from the CAPWAP analysis of the dynamic load test data and the measured set of the pile during high strain dynamic load testing are used to evaluate the accuracy of the capacity predicted by pile driving equations. Based on the data collected, the accuracy of each pile driving method is discussed. Furthermore, the factors affecting the accuracy of the pile driving equations are also investigated. Moreover, the factors of safety to be used with different methods are also presented.

Study of full-scale elements of a ferrocement roof system for Caribbean application

The Caribbean region is exposed to hurricanes annually and the frequency of occurrence is expected to increase due to global warming. However, as revealed due to hurricane Ivan in 2004, the current roofing systems of the houses are particularly vulnerable. In other parts of the world ferrocement roofing is a technically and economically viable solution but for acceptance in the Caribbean, the aesthetic factor controls the roof design in terms of topology prompting a new innovative solution. Load test data is also required by the approving agencies of the various jurisdictions in the Caribbean. The results of structural testing of the full-scale main components of a proposed ferrocement roof system are presented. This comprises of a 9.0 m wide and 2.5 m high pitched-portal frame of channel-section with bolted steel connections; a 6.10 m hollow-section roof slab in bending, and slab-to-frame bolted connections in pullout. It was found that the performance of the elements is consistent with the acknowledged beneficial behavior of ferrocement, and the proposed ferrocement roof system should adequately address the loading conditions expected in the Caribbean. The data can also be used to determine safe spans of the proposed roof system for application in other regions as well.