Load Test Data Research Articles

Shaft-grouted bored pile – a practical engineering approach to the bearing capacity

ABSTRACT The paper investigates various static load test results on both shaft-grouted and non-shaft-grouted (plain) bored piles at eight project sites in Vietnam. A practical engineering model for shaft-grouted bored piles is proposed to determine the side friction of the shaft-grouted bored piles (drilled shafts), with consideration of shaft friction distribution on instrumented bored piles. The improved ratio of bored pile skin resistance after shaft grouting, compared to non-shaft grouting, ranges from 1.058 to 1.323. The application of shaft grouting is beneficial for the soils of gravel, sand, clayey sand, and silty sand, which have the permeability ranging from 1.00 × 10–5 to 8.60 × 10–5 m/s, while it is not sufficient for clayey soils. Moreover, the possibly mobilised side friction for these shaft-grouted bore piles can be up to 250 kPa. The results derived from the proposed model agree well with the static load test data of the shaft-grouted piles in term of side friction, bearing capacity, and load transfer mechanism.

Study on increasing load capacity of wooden arch bridge by CFRP strengthening: experimental and numerical Verification

The wooden arch corridor bridge is a typical representative of Chinese wooden bridges, holding significant historical research value. Currently, these bridges face issues of severe component deformation and insufficient load-bearing capacity. To address these problems, this study employs CFRP reinforcement on the components of wooden arch corridor bridges to reduce deformation and enhance load-bearing capacity. Experimental research on CFRP reinforcement has yielded the elastic modulus of the bonding interface. Given the lack of an accurate numerical model for wooden arch corridor bridges, this study establishes a precise numerical model by setting parameters based on load test data from wooden arch corridor bridges. The elastic modulus obtained from the experiments is input into the numerical model for analysis. The results indicate that CFRP exhibits excellent reinforcement performance, with the load-bearing capacity of the reinforced damaged components still reaching 75%–85% of their original capacity, while the load-bearing capacity of the reinforced undamaged components increases to 130%–140% of their original capacity. The failure modes of the CFRP-reinforced wooden components suggest that allowing for some gaps in the bonding of CFRP can enhance overall ductility. The application of CFRP to wooden arch corridor bridges also demonstrates favorable reinforcement effects, increasing the load-bearing capacity of the arch surface by approximately 20%, thereby providing a theoretical basis for the reinforcement of wooden arch bridge frameworks.

A new approach on constitutive modeling for quasi-brittle materials under multiaxial loading

Abstract This work introduces a new method for expanding unidimensional models to predict material behavior under multiaxial loading. The concept of six-dimensional mechanical space is adopted, and in each basis direction of the space, there is one fiber-bundle model (FBM), so these six FBMs are independent amongst one another but follow the same damage evolution rule. Under triaxial loading, these FBMs have different stress and strain states, so six corresponding damage variables have different values. The anisotropic damage is thus represented by the six damage variables. When it is under uniaxial loading, the six-dimensional space reduces to one-dimensional space, so the proposed model can be calibrated using uniaxial loading test data, and the calibrated model can predict the material behavior under multiaxial loading conditions. Biaxial loading and triaxial loading test data are used to verify the proposed model, and parametric analyses are performed to analyze model predictions under different loading conditions. It shows that model predictions agree well with the test data and are consistent with experimental observations.

Effect of Load Cycling on High Temperature Creep of 316L Stainless Steel

For components in concentrating solar thermal plants, the creep mechanism will cause a significant portion of material damage to receivers, storage tanks, turbines and pipework. These components will undergo conditions where loads, temperature, or both load and temperature are not constatnly applied. This creep damage process will not resemble the constant load creep tests used to characterise creep of materials. Therefore, creep tests incorporating a load cycle were undertaken to obtain a better understanding of how high temperature materials respond to these cyclic conditions. These tests showed that when time under load was considered, creep undertaken under load cycling conditions were accelerated relative to constant load conditions. A modified Larson-Miller approach was used to assess this effect and determine an equivalent stress where constant load test data agrees with the cycled test data. This found that cycling the load was equivalent to if the system were under 3 and 7 MPa higher stress, for tests which were loaded for 12 hrs and 6 hrs per 24 hrs respectively. This could be a potential approach to simply and easily consider these load cycling effects for design and life analysis.

Enhancing Quality Management of PHC Piles through Improved Driving Formulas: A Comprehensive Review and Analysis

In construction projects, conducting dynamic load tests on all piles proves impractical. Selective testing estimates bearing capacity, while the remaining piles rely on penetration depth for management. This approach, however, faces reliability issues due to varying conditions among piles. Technological advancements, such as non-contact hammers and sensors, have enhanced the accuracy of penetration depth measurements during final driving. Nonetheless, relying solely on penetration depth for construction and quality management remains problematic. This study, therefore, focuses on enhancing the use of driving formulas to improve pile quality management, particularly for the widely used pre-stressed high-strength concrete (PHC) piles. To improve pile quality management, existing driving formulas underwent review and refinement. Utilizing 258 dynamic load test data from various sites, the Hiley, Gates, and Danish formulas underwent validation through statistical analysis and graphical comparison. Enhancements to the Gates formula, achieved through curve fitting with actual data and the application of segment-based coefficients, demonstrated increased accuracy in bearing capacity estimation. These improvements offer a more reliable approach to pile quality management in construction projects.

Optimizing axial bearing capacity estimation of pre-bored grouted planted nodular (PGPN) pile: Enriched dataset and genetic algorithm approach

This study introduces a practical and efficient methodology to improve the estimation of the ultimate axial bearing capacity of Pre-bored Grouted Planted Nodular (PGPN) piles, addressing a critical need in geotechnical engineering. By enhancing the dataset with 98 additional case histories and pile load test data from various projects across Vietnam, we have developed a more reliable predictive tool for engineers. The use of genetic algorithms has refined existing empirical formulas, significantly improving their accuracy while remaining simple enough for hand calculations. The proposed formula achieves a correlation coefficient of 0.907, a 7.2% improvement over previous methods. This research offers a valuable solution for the challenges faced in predicting the load-bearing capacity of PGPN piles, providing a more dependable method that can streamline design and construction practices.

Distraction Enterogenesis in Rats: A Novel Approach for the Treatment of Short Bowel Syndrome.

Surgeons often encounter patients with intestinal failure due to inadequate intestinal length ("short bowel syndrome"/SBS). Treatment in these patients remains challenging and the process of physiologic adaptation may take years to complete, which frequently requires parenteral nutrition. We propose a proof-of-concept mechanical bowel elongation approach using a self-expanding prototype of an intestinal expansion sleeve (IES) for use in SBS to accelerate the adaptation process. IESs were deployed in the small intestines of Sprague Dawley rats. Mechanical characterization of these prototypes was performed. IES length-tension relationships and post-implant bowel expansion were measured ex vivo. Bowel histology before and after implantation was evaluated. IES mechanical studies demonstrated decreasing expansive force with elongation. The deployment of IES devices produced an immediate 21 ± 8% increase in bowel length (p < 0.001, n = 11). Mechanical load testing data showed that the IESs expressed maximum expansive forces at 50% compression of the initial pre-contracted length. The small-intestine failure load in the rats was 1.88 ± 21 N. Intestinal histology post deployment of the IES showed significant expansive changes compared to unstretched bowel tissue. IES devices were scalable to the rat intestinal model in our study. The failure load of the rat small intestine was many times higher than the force exerted by the contraction of the IES. Histology demonstrated preservation of intestinal structure with some mucosal erosion. Future in vivo rat studies on distraction enterogenesis with this IES should help to define this organogenesis phenomenon.

Assessment of load test program for reliability-based design of piles

Quantifying the uncertainty of the bearing capacity of piles is crucial in the context of reliability-based design (RBD) for pile foundations. The utilization of site-specific load test data plays a pivotal role in reducing the uncertainty associated with bearing capacity, thereby enhancing the overall design of pile foundations. However, prior to initiating a load test program, there exists uncertainty both in the outcomes of the program and the potential benefits it may yield. This research endeavors to develop a method that allows for assessing the effectiveness of a load test program before its execution. The structure of this paper is as follows: firstly, it introduces a framework for evaluating the utility of the pile load test (PLT) program. Subsequently, it constructs a pre-posterior analysis to examine the anticipated benefits derived from the load test program. Finally, the proposed methodology is elaborated upon through a detailed example. This paper is valuable for enhancing decision-making in optimizing pile load test programs.

Analisis Daya Dukung &amp; Penurunan Bored Pile 80cm di Proyek Kompleks Kantor-Apartemen dengan Metode Analitis &amp; Elemen Hingga

This study will look for the ultimate bearing capacity value of bored pile foundation and foundation subsidence, based on SPT data and loading test calculated empirically with SPT data using equations provided by O'Neil and Reese while loading test data using curve interpretation Davidson Method, Mazurkiewich Method, Chin Method and finite element method using 2D Plaxis software with all types of medium mesh. After analysis, the ultimate bored pile carrying capacity value of ø 80 cm based on SPT data using the O'neill and Reese equations was 1242 tons, then analysis using the Davisson method of 875 tons, using the Mazurkiewiech method of 960 tons and the Chin method of 876 tons. While the ultimate carrying capacity based on PLAXIS 2D calculations is 1364 tons. 5. Based on SPT data, the carrying capacity of a single bored pile axial permit (Qi) was obtained at 497 tons with SF = 2.5. And for the value of the decrease that occurs in the bored pile foundation based on analytical results is 22.85 mm, based on the loading test is 7.95 mm and based on the PLAXIS 2D program is 14.12 mm. Based on the results of the analysis, it can be concluded that the O'Neil and Reese equations provide a greater value than the interpretation of load testing so that it will provide a large safety value if used when design and descent analysis that is closest to the results in the field is analysis with 2D PLAXIS with the Mohr-Coulomb modeling type. There are differences in carrying and lowering capacity analysis results with several methods used, but the use of analytical methods and finite element methods with PLAXIS 2D meets the safety requirements of bored pile foundations.

Research on internal explosion loads in folded arch tunnels: A theoretical approach

To elucidate the loading characteristics in the folded arch tunnel subjected to internal explosion, a field blast test was conducted in a large-scale (1:5) model constructed according to the immersed tube tunnel of Hong Kong-Zhuhai-Macao Bridge. The spatial distribution and time histories of the overpressure around the detonation point were recorded in the folded arch tunnel. The test data indicate that the internal blast loads in the folded arch tunnel is mainly attributed to the shock overpressure and gas overpressure. A fine FE model was developed in the LSDYNA platform, which was validated by the loading test data. The propagation process of blast waves and detonation products along the folded arch tunnel were studied by the developed model, which also helped reveal the interaction mechanism with the tunnel structure. Three existing theoretical models in predicting the internal blast loads were compared and assessed. It is found that the existing theoretical models developed for the internal blast loads has limitations in predicting the blast load in the tunnel, which especially would introduce a large error in manifesting the gas overpressure. A new loading model that enables precisely predicting the internal blast loads in the folded arch tunnel was proposed, which offers valuable insights for the blast-resistant design and disaster mitigation measures for the tunnel structure.

Hysteretic behavior and cyclic constitutive model of corroded low-alloy steel in a corrosive environment

To quantitatively analyze the mechanical properties of corroded low-alloy steel under monotonic and cyclic loading, a cyclic constitutive model was established. Accelerated corrosion, monotonic tensile testing, and cyclic loading testing of 28 groups of Q345B steel specimens were conducted to examine how corrosion affected the monotonic tensile and hysteresis characteristics of the specimens, and the combined hardening parameters based on the Chaboche model were calibrated and confirmed based on the test findings. The results showed that corrosion clearly affected the monotonic stress-strain curve of steel and that most mechanical indices deteriorated linearly with respect to the corrosion rate. The combination of corrosion and cyclic cumulative damage exacerbated the degradation of the deformation capacity of the steel and affected its energy consumption capacity and cyclic hardening. The constitutive model of corroded steel calibrated on the basis of cyclic loading test data could effectively simulate the hysteresis performance of corroded Q345B steel under cyclic loading.

Experimental Behavior of a Steel Girder–Stringer–Floorbeam Bridge

The presented case study summarizes a quick-response project for the Tennessee Department of Transportation (TDOT), which focused on the steel-stringer behavior for a girder–stringer–floorbeam bridge. TDOT was confronted with relatively low stringer load ratings for many of their 31 similar structures. As a result, TDOT initiated this field study to ultimately produce refined load ratings. This information was then to be utilized for deciding whether an intervention (e.g., retrofit) was necessary. Diagnostic load testing was the approach selected and a representative bridge was chosen. Then load testing was comprehensively designed and executed. This included the installation of 42 strain gauges, data-acquisition quality-control testing, weighing and measuring test trucks, load testing of the structure, and then removal of the system. The load-test data provided insight into the true behavior of the bridge. The stringers were subjected to a combined interaction of the global and local response. Overall, the local demands were the largest component, but the magnitudes were well below the predicted values. This was partly because of the lateral distribution of the load. Additionally, partial composite action was identified between the steel stringers and concrete slab. Refined load ratings were calculated using the field-measured data and following the AASHTO Manual for Bridge Evaluation. The comparison of predicted to measured responses clearly indicated the conservative nature of the prior analytical calculations. The stringer load ratings were increased by 68% based on the field testing. In the end, the steel-stringer load ratings were sufficient, with no intervention necessary.

Theory and Empirical Analysis of Bridge Load Limitation Under the Action of Typical Heavy-Duty Vehicles

Abstract With the continuous growth of transportation demands, in-service highway bridges face greater challenges in their long-term operational lifespans, and bridge collapse accidents caused by vehicle overloading occur from time to time. Additionally, under the influence of loads and environmental factors, various wear patterns inevitably lead to degraded reinforced concrete bridges. In view of this problem, it is reasonable and feasible to limit the vehicle loads passing over highway bridges, and the key basis for limitation is determining the load limit value of a bridge. To determine a reasonable load limit value of a bridge, this paper has carried out the following research: Based on a classification of vehicle types, this paper explores the load parameters of several heavy-duty vehicles with large traffic volumes through traffic flow information and summarizes the load spectra of typical heavy-duty vehicles. On the basis of the theory of structural reliability, a method for determining the limit load of bridges is proposed. Given a structural target reliability index, the theoretical load limit value of a bridge can be calculated. To ensure the rationality of the theory of bridge load limit value, by relying on the engineering example, the theoretical load limit value is calculated. By comparing actual bridge load test data with the finite element model results, the rationality of the bridge load limiting theory is verified. Finally, the paper notes that it is safer and more reliable to define the load limit value according to the bending stress state for bridges.

Prediction Ability Analysis of Phenomenological Strength Criteria for Composites

The article examines and assesses the phenomenological strength theory of composite materials. A comparative analysis of the theoretical envelopes was conducted for each criterion. A unified form of the phenomenological strength criterion was established. The study specifically examined the effects of altering the interaction parameter on the Tsai-Wu criterion’s theoretical envelope. Based on the available experimental data, the study plotted the failure envelopes of each strength criterion under planar composite stress states. The variation of these envelopes across various stress quadrants was highlighted. As a result of the examinations, four typical phenomenological strength criteria were chosen. The composites’ off-axis tensile and biaxial loading test data were used to evaluate the predictive power objectively. The results showed that not all stress states’ test results agreed with the predictions of the phenomenological strength theory. The criterion proposed by Norris and Tsai-Hill performed better at accounting for the material’s different compressive and tensile characteristics. The other criteria tended to be conservative under particular circumstances. Simultaneously, the Hoffman criterion matched the test data more closely over a broader range of stress states. Overall, this study clarified the limitations and applicability of various strength criteria in composite material strength prediction.

Predicting Load-Settlement Behaviour of Large Diameter Piles using Runge-Kutta numerical Method.

A numerical solution for predicting the axial load and corresponding settlement of large diameter piles is proposed based on the hyperbolic curve load transfer function in this paper. It is important to note that the most reliable approach to determine the axial load capacity of a pile is to use the P-S curve, which is usually obtained through an on-site load test. Performing a pile load test on a large diameter pile (pile diameters over 3m), requires a thousand tons of test load, which sometimes is unachievable. The load-settlement relationship or P-S curve of this type of pile can be determined by the Runge-Kutta numerical method for practical application especially for offshore piles. Comparison is made between the results obtained by this proposed numerical, the test data, analytical solution and pile load test data, and close agreement has been found thus verifying the accuracy of the proposed method. However, the rigid body displacement of the piles did not show any significant effect on the proposed numerical when compared to the analytical and onsite pile load test results. It is expected that the proposed numerical method can be used to predict the load and corresponding settlement of large diameter piles.

Digital Twin and Blockchain Extension in Smart Buildings Platform as Cyber-Physical Systems

Cyber-physical systems is integrated computation with the physical world. CPS increasing in a wide range of applications, from smart homes to smart buildings. Digital twins are promising way to solve challenges with combination of CPS, 3D technology, and IoT. The system provides users with immersive interfaces to control and interact with devices within the smart building environment. Blockchain was chosen to secure user data using cryptographic algorithms and ensure data protection against manipulation, spying, and theft. Average load testing data for digital twin platform implemented in smart buildings range from 1 to 11 floors. The results reveal a gradual increase in average test times as the buildings' size and complexity grow, with the following values: 5.663s for 1 floor until 11 floors 7.294s. The data obtained from of the blockchain test using Hyperledger Besu provide essential insights into the system's performance with several bandwidth that used in the system. Average time for each test trial ranged from 1.066 seconds to 2.006 seconds, showing slight variations based on the bandwidth used. However, transactions per second (TPS) values were relatively fast, ranging from 1.066 tps to 0.499 tps with positive aspect of the retention rate for all trials was 100% success.

Determination of pile bearing capacity by piles static load test data

In determining pile bearing capacity, static load testing is still considered a highly reliable method and can be used to verify pile load calculations by other methods (BS EN 1997-1:2004, 7.4.(1)P). In practice, often difficult to define an ultimate limit state from a load settlement plot showing a continuous curvature (BS EN 1997-1:2004, 7.6.1.1(3)). Therefore, the determination of pile load capacity from static compression test results is currently not consistent among standard systems. Besides, each standard stipulates different pile static compression test procedures leading to different methods of determining pile load capacity. The article practices calculation of pile load capacity from static compression test results by different methods, thereby comparing the results and making comments.

Determining the Stabilised Subfoudation Soil Deformation Modulus According to the Plate Load Tests and Geotechnical Monitoring Data

Introduction. The subsiding soils, which are widely spread in the south of Russia, create a number of problems and hazards due to the high probability of subfoundations subsidence in case of exceeding the values of initial soil moisture and initial pressure for subsidence. This is an important phenomenon to be considered at all life cycle stages of a building or structure, especially at the stage of design, when the scientifically justified design and technological solutions must be developed to ensure the reliable operation of facilities in the complicated engineering and geological conditions being studied hereby. The present article analyses the acting federal and regional regulatory and technical documentation in the field of buildings and structures design on the subsiding soils. Based on the numerical experiment, the incorrectness of the results sometimes received upon following the normative methodology is shown. A new calculating methodology based on determining the stabilised subfoudation soil deformation modulus according to the plate load tests and geotechnical monitoring data is proposed.Materials and Methods. The research comprised:– analysis of the existing approaches and methodologies for the subfoundations and foundations design on the subsiding soils;– numerical experiments, including calculations according to the normative methodology, which implied variation of the original data of both the initial properties of soils and technological parameters of stabilisation, as well as statistical processing of the results;– analysis of the carried out earlier by the authors geotechnical monitoring results of the buildings built on the stabilized soils and experimental study of the deformation properties using a patented device;– determining the main factors having influence on the design solutions for the subfoudation soils and building foundations strengthening under a complicated set of operational loads and establishing a new dependence of the stabilised soil deformation modulus on the initial soil deformation modulus and percentage of soil reinforcement.Research results. It has been established that the existing methodologies for calculating the stabilised subfoudation soils are not enough precise for determining the forecastable subsidence of buildings and structures, and the obtained design values do not always correspond to the factual deformations of subfoundations and foundations. The dependence of the stabilised subfoudation soil deformation modulus on the initial soil deformation modulus and percentage of soil reinforcement with the cement-sand mortar has been traced. A new calculating methodology has been developed based on determining the stabilised subgrade soil deformation modulus according to the data of the plate load tests using a patented device and geotechnical monitoring.Discussion and conclusion. It has been established that the deformation modulus of the soil mass stabilised by the cementation method depends non-linearly on percentage of soil reinforcement with the cement-sand mortar and the initial soil deformation modulus, and this dependence is described by a second-order surface equation of a general form. It is recommended to apply the discovered dependencies for designing the technological parameters of the subsiding soils stabilisation in the Rostov region conditions.

Fast evaluation method of post-impact performance of bridges based on dynamic load test data using Gaussian process regression

Bridges occasionally suffer from the vehicle or ship collision accidents, leading to structural damage and bridge collapse, resulting in severe consequences such as casualties, ship sinking, and vehicle damage. After such accidents, the performance evaluation of bridge structures is significant for bridge maintenance. The bridge's structural performance should be assessed after a collision with a vehicle or ship before regular traffic is resumed. A gray correlation analysis technique was introduced for the swift and efficient assessment of bridge structural performance following impacts. This method aimed to identify the influential parameters associated with bridge structural performance. Utilizing outcomes from dynamic load tests along with the Gaussian process regression model, adjustments were made to the original finite element analysis model. This refinement facilitated precise scrutiny of structural damage and expedited accurate performance evaluations of the bridge. Subsequently, a practical examination was carried out following a ship collision with the Wanjiang Bridge to validate the viability and precision of the proposed approach. A comparison between performance evaluation outcomes derived from the bridge's structural response to ship collision and actual field test results demonstrated the substantial accuracy and computational efficacy of the suggested technique. The proposed method uses a dynamic load test combined with an intelligent algorithm to replace the static load test, effectively solving the expensive, time-consuming, traffic-impeding static load test problem.

Estimation Criteria for Static Rock Mass Deformability Modulus for Rock-Socket Design in Metamorphic Rock Masses

This study investigates the most appropriate empirical criteria to estimate the static rock mass deformability modulus (𝐸𝑚) in the design of rock-sockets in cast-in-situ bored pile construction. The in-situ 𝐸𝑚 values are initially estimated through back analysis of static pile load test data. Secondly, the rock mass deformability estimated from back analysis (𝐸𝑚b) are tested statistically against selected established empirical equations to determine whether the latter are appropriate for use in metamorphic rock terrain of Sri Lanka. It is found that the existing empirical criterion based on the square root of intact unconfined compressive strength (𝜎𝑐) derived from back analysis of pile load test results is appropriate for weak-poor rock masses. For strong-poor rocks, it is recommended to employ the equation based on 𝜎𝑐', and in general the two equations generate lower and upper bound solutions. The equation based on intact deformability modulus (𝐸𝑖) performs well in strong-excellent quality rock masses, while the equations based on 𝐸𝑖 and rock quality designation (𝑅QD) are found to be appropriate for weak-fair to excellent rock masses. Finally, a new set of equations appropriate for different rock mass types have been proposed through regression analysis along with appropriate design measures to be adopted.