Load Test Method Research Articles

Experimental Study on the Flexural Performance of the Corrosion-Affected Simply Supported Prestressed Concrete Box Girder in a High-Speed Railway

Prestressed concrete box girders are commonly employed in the development of high-speed railway bridge constructions. The prestressed strands in the girder may corrode due to long-term chloride erosion, leading to the degradation of its flexural performance. To examine the flexural performance of corrosion-affected simply supported prestressed concrete box girders, eight T-shaped mock-up beams related to the girders used in the construction of high-speed railway bridges were manufactured utilizing similarity theory. Seven of the beams underwent electrochemical accelerated corrosion, and then each beam was subjected to failure under the four-point load test method. Measurements recorded and analyzed in detail during the loading process included the following: crack propagation, crack width at various loads, crack load, ultimate load, deflection, and concrete strain of the mid-span section. The results demonstrate that a corrosion rate of just 8.31% has a considerable impact on the structural integrity of the beams, as evidenced by a pronounced reduction in flexural cracks and a tendency towards reduced reinforcement failure. Furthermore, the corrosive process has a detrimental effect on mid-span deflection, ductility, and ultimate flexural bearing capacity, which could have significant implications for bridge safety. This study provides valuable insights for the assessment of flexural performance and the development of appropriate maintenance strategies for corroded simply supported box girders in high-speed railways.

BI-DIRECTIONAL STATIC LOAD TESTING

A full-scale static load testing program can optimise many of the requirements in terms of costs and remove uncertainties. The bi-directional load testing method, by eliminating the reaction structures of the traditional top-down testing methodology, opens up unseen possibilities of the testing program in the most efficient, safe, and cost-effective manner for all types of foundations, particularly for larger test loads. The benefits of using bi-directional load tests and how effective they are will be described in the paper. The revolutionary bi-directional static load testing method has also a significant side effect of reducing CO2 emissions for such tests by up to 80%.

A method for accurate extraction of three-dimensional point cloud feature data in loading test of container ships

The accuracy of container slot dimensions directly affects the efficiency and safety of container loading and unloading. However, traditional methods of container loading tests need to be improved for their long cycles, high costs, and low production efficiency. With the application of three-dimensional laser scanning devices in ship manufacturing, the use of simulated container loading test methods based on point cloud becomes a breakthrough in key technology for container ship construction. This paper presents a multi-objective segmentation method of cargo hold feature point cloud for container ship simulated loading tests. Data preprocessing algorithms are applied to remove noise and pseudo-image, and then a Random Sample Consensus algorithm is used to remove bulkhead and cargo bottom point clouds. Based on the density-based spatial clustering of applications with noise algorithm and the region growing algorithm, an algorithm for multiple segmentation of guide rail and bottom cone point clouds is devised, and a four-plane segmentation of guide rail point clouds is realized. Finally, a method for three-dimensional point cloud data flatness assessment and a Hausdorff distance based method for calculating the guide rail lateral and longitudinal spacing are proposed. These methods are validated through the loading test of a 16,000 TEU container ship.

Test methods for determination of shear properties of sandwich panels

This paper presents analysis and comparison of test methods for determining transverse shear strength and shear modulus of steel-faced sandwich panels commonly used in construction. The test methods are taken from the governing European standard EN 14509:2013. Two-point loading and four-point loading test methods as well as a full-scale test method are examined. Based on extensive experimental work on sandwich panels with varying core thickness, comprising mineral wool (MW) and polyisocyanurate (PIR) and encompassing both roof and wall panels, this study provides details of the test setup for the four-point loading and vacuum box methods with which a pure shear failure is obtained. Such details are missing from EN 14509. This paper highlights that the two-point loading method fails to consistently produce shear failure, especially in thicker panels, indicating it does not accurately measure transverse shear strength. The results of the experiments conducted in this study indicate that the four-point loading and full-scale test methods provide consistent shear failure for thicker panels while yielding greater transverse shear strength than the two-point loading test in general.

Bearing Capacity of Precast Concrete Joint Micropile Foundations in Embedded Layers: Predictions from Dynamic and Static Load Tests according to ASTM Standards

In this paper, joint precast piles with a cross-section of 400 × 400 mm and a pin-joined connection were considered, and their interaction with the soil of Western Kazakhstan has been analyzed. The following methods were used: assessment of the bearing capacity using the static compression load test (SCLT by ASTM) method, interpretation of the field test data, and the dynamic loading test (DLT) method for driving precast concrete joint piles, including Pile Driving Analyzer (PDA by ASTM) and Control and Provisioning of Wireless Access Points (CAPWAP) methods. According to the results, the composite piles tested by the PDA (by ASTM) method differ by 15 percent compared to the static load method, while the difference between the dynamic DLT (by ASTM) method and the static load (by ASTM) method was only 7 percent. So, according to the results, the alternative dynamic method DLT (by ASTM) is very effective and more accurate compared to other existing methods.

Air-conditioning load characteristics and grey box predicting model in subway stations

With the continuous expansion of metro, energy conservation of air-conditioning system in subway stations draws the attention of the whole world. Most of the researches are focused on improving the energy efficiency of the system, while the load characteristics of subway stations are paid little attention. The inaccurate load prediction in the designing of air-conditioning system results in redundancy and low operating efficiency. Therefore, accurately predicting the air-conditioning load is crucial for energy saving in subway stations. In this paper, an innovative three-stage subway air-conditioning load test method was proposed and implemented in nine subway stations in Qingdao. Based on the test data, the special air-conditioning load characteristics of subway stations as underground buildings were analyzed. The results showed that electrical equipment load accounted for the largest part, reaching 53.7 %, while only 42 % of the equipment power was converted into air-conditioning load. The positive role of the envelope should not be ignored, especially in the case of entrance and exit walls, which bore almost all of the fresh air load. Based on the three-stage test, a grey box model was established and the error was validated to be within 6 %. With this model, the load of air-conditioning system can be calculated by inputting passenger flow, power of electrical equipment and public area. This paper provides a reference for the design and operation of air-conditioning system in subway stations.

Experimental Study on Repairing/Restoration and Reinforcement Methods of the Reinforced Concrete Structures Damaged by Earthquakes

For earthquake-damaged reinforced concrete structures, the static loading test method is adopted to carry out loading tests under cyclic loading on reinforced concrete beams with different reinforcement rates and columns with different axial compression ratios, and the effect of reinforcing and repairing the damaged reinforced concrete structure by using adhesive steel plates and carbon fiber cloth is investigated. Through comparative studies of structural hysteresis curves and skeleton curves under different reinforcement methods, it is concluded that reinforcement has significantly improved the hysteresis characteristics and ductility of members, and the seismic performance of the carbon fiber reinforcement method is better than that of the steel plate reinforcement. This study provides valuable references and suggestions for practical earthquake-damaged building reinforcement and repair works and seismic reinforcement works.

Prediction of bridge structure deformation and strain based on dynamic testing and intelligent algorithms

The field load test is a direct and effective method for evaluating the performance of bridge structures. However, existing bridge field static load tests are costly and inefficient; moreover, they obstruct traffic and cause unavoidable damage to the bridge structure. As an alternative the the static load test, a random model update method based on bridge dynamic load tests and the Bayesian inference is proposed in this paper. The bridge static load test results were predicted with a high accuracy. To speed up the Bayesian method to infer the posterior probability density of the updated parameters, the Gaussian process was used in place of the finite element model, and the Bayesian inference used the Markov chain Monte Carlo method based on the delayed rejection adaptive Metropolis algorithm. First, the parameters to be modified for the bridge structure analysis model were determined based on the global sensitivity analysis method. Second, a uniform design sampling method was used to establish the Gaussian process optimization model to update the random model of the bridge structure. Finally, a reinforced concrete truss arch bridge was used to verify the correctness of the static load results of the bridge predicted by the random model update method based on dynamic load testing and Bayesian inference. The research results reveal that the prediction results of the bridge static load test based on the dynamic load test and Bayesian inference method agree with the actual test results.

ИССЛЕДОВАНИЕ НЕСУЩЕЙ СПОСОБНОСТИ СВАЙ НА ОСНОВЕ ЭМПИРИЧЕСКИХ ДАННЫХ, ДИНАМИЧЕСКИХ ИСПЫТАНИЙ И ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Axial bearing capacity is an important factor in designing of foundation. It must be able to carry the load of upper structure without any significant deformation due to important role in pile design. A part from empirical and numerical methods, axial pile bearing capacity can be predicted by pile driving analyzer test that use wave equation analysis during the test. Prediction of the axial bearing capacity and its distribution can be achieved by combining wave equation analysis with dynamic pile monitoring. This paper compares the axial capacity of pile obtained from PDA records with predicted axial capacities obtained using empirical, numerical, and interpretation of static load test method. The empirical method used NSPT data from bore testing that conduct in site, finite element method that uses in this study is Plaxis 8.6. Both of them was compared with PDA test result of axial bearing capacity. There is a difference value of the calculation results of axial pile bearing capacity and foundation settlement. Comparing with PDA, from empirical method has smallest deviation for axial bearing capacity which equal to -268.45 kN with percentage -6.05%, smallest settlement equal to 0,0044 m. Plaxis result shows that distinction between Qult result equal to -11.00 kN with percentage -0.24% and settlement of foundation equal to 0,005 m. From interpretation of static loading test method smallest deviation for Qult which equal to -40,00 kN, with percentage -0,90%, and smallest settlement equal to 0,0055 m. So, from all method the smallest deviation for Qult and PDA result is used finite element method. This is due to many data parameters has been inputted and analyzed in the Plaxis program, so the results of calculation analysis are more detailed and closer to the situation in the research site. Differences in axial bearing capacity can be caused by the test was carried out which depends on the accuracy of operator and parameters that used in the calculations.

Out-of-plane characteristics of cross-laminated bamboo and timber beams under variable span three-point loading

Given the exceptional mechanical properties of cross-laminated bamboo and timber (CLBT) and its ability to efficiently utilize bamboo and timber resources, CLBT holds considerable potential for applications in modern sustainable timber and bamboo structures. CLBT panels, when used as floors or roofs, typically experience out-of-plane loads. This study investigates the out-of-plane bending and shear characteristics of 5-layer CLBT and cross-laminated timber (CLT) specimens using the variable span three-point loading test method. The results indicated that the developed CLBT exhibited superior mechanical properties compared to CLT, offering a preliminary demonstration of its value in engineering applications. In addition, factors such as the span and outermost lamination influenced the failure modes, vertical deflections, strain distributions, ductility indices, and energy absorption characteristics of CLBT and CLT specimens. This study provides a foundational reference for using CLBT as floor and roof panels subjected to out-of-plane loads and lays the foundation for further research.

Bridge finite element model updating using stochastic vehicle-induced static response monitoring data

Finite element model updating (FEMU) is a frequent method for minimizing the differences between actual and predicted bridge structural behavior. However, static model updating for long-span bridges usually requires load tests to obtain the response under known static loads, which is costly due to long traffic interruptions. To offset this disadvantage, a static FEMU method based on long-term monitoring data is proposed to update the model in real-time by taking stochastic traffic loads with certain statistical characteristics as known static loads. First, the theoretical relationship between stochastic traffic flow statistical characteristics, static response statistical characteristics, and structural stiffness parameters is established. An objective function based on the probability characteristics of the long-term vehicle-induced response is constructed. Then, the FEMU process based on monitoring data is introduced, including the acquisition of the finite element model vehicle-induced response, the extraction of the actual vehicle-induced response based on the monitoring data, the selection of model updating parameters, and the application of the global-local parameter updating optimization method. Finally, the effectiveness of the proposed method is verified by applying numerical examples and real bridge examples to a long-span suspension bridge. It can be concluded that the proposed method can achieve FEMU based on long-term monitoring data, avoiding the inconvenience and large cost caused by load tests. The accuracy and efficiency of the model updating can meet the engineering requirements well through comparison with the result of the traditional load test method.

Evaluation of ultimate load - bearing capacity of piles based on static compression test and pile dynamic analysis (PDA)

Determining the load bearing capacity of piles from field tests is a reliable method that allows for the verification of load carrying capacity according to theoretical calculations, thereby the ultimate load-bearing capacity of the piles can be evaluated, serving as the basis for selecting the design load-bearing capacity that is suitable for the site conditions. Among the various pile load testing methods, static compression testing is a traditional method known for its high reliability and early adoption. However, when piles are constructed at significant depths or large diameter drilled piles have higher load bearing capacities, static compression testing encounters difficulties due to the large experimental load and extends testing times. In contrast, the pile dynamic analysis method (PDA) introduced by the Case Institute of Technology in the United States in the 1960s determines the load bearing capacity of piles based on stress wave propagation theory in elastic bars. It offers several advantages, including shorter testing times and no need for static loading, making it suitable for challenging terrain conditions. Nowadays, this method is widely used and integrated into the design guidelines and testing standards of many countries. In this article, base on the results of axial static compression tests and PDA method on reinforced concrete piles and drilled piles at several real project to compare and evaluate the load bearing values of the piles and assess the reliability of the testing methods.

PERFORMA MICROFRAMEWORK PHP PADA REST API MENGGUNAKAN METODE LOAD TESTING

The need for flexibility in application development by minimizing the constraints of a server production environment makes n-tier architectures increasingly used. This architecture is implemented in the form of middleware or often called API. REST API is an API architecture that is currently the most widely used for middleware-based application development.
 PHP is an easy-to-use programming language for developing REST APIs with its microframework. Each microframework has features such as database connection handling, URL routing, and performance is the top one. The large number of PHP microframeworks with different performance issues makes the selection of API-based application development cores very important. Especially if it is projected to handle data exchange or client requests in large numbers. As a basis for selection, performance testing needs to be carried out on each microframework to determine its suitability for API-based application development.
 Performance testing uses the load testing method and develops the popular PHP microframework as a basis for creating test applications. The microframework includes FatFree, Lumen, Phalcon-micro, and Slim. Testing is carried out systematically using a test plan that has been designed for performance testing needs. The focus is to analyze the RPS (Request Per Seconds) and latency to the percentile that the wrk2 test tool generates on a predetermined test type

Enhancing static load test of pipe pile composite foundation with innovative elastic cushioning technology

Pipe piles have been widely used in composite foundation treatment by virtue of the advantages of assembly line production, easy control of pile quality, fast construction, high bearing capacity of single pile and green environmental protection. By introducing elastic cushion in the static load test method of pipe pile composite foundation, and using theoretical analysis and field test to study the change rule of settlement, pile-soil stress ratio and pile top stress of pipe pile composite foundation with different cushion stiffness. It is concluded that it is feasible to replace the sand cushion layer recommended by the current specification with elastic cushion layer. The study shows that the elastic cushion method of static load test of pipe pile composite foundation is closer to the bearing state of real working condition. The elastic cushion has better pile-soil stress adjustment effect, which is more responsive to the stress adjustment effect of actual engineering cushion, and the elastic cushion provides an improved method for the static load test method of composite foundation.

Analysis of Complex Tests of the Module Piles in Difficult Soil Ground

The purpose of the scientific work is comparative analysis using Static compression load test (SCLT) and Dynamic load test (DLT) methods to determine of bearing capacity of pile foundations in difficult soil ground. Mega project is the construction site of Cargo offloading facilities (COF) in Atyrau region. In project used 2 consists module piles. Precast concrete module piles have 16 meter piles and 11.5 meter (9.5 m) piles with joint a total length of 25.5 m and 27.5 m, cross section 40×40 cm. The design of pile foundations was carried out in accordance with the requirements of regulatory standards. DLT testing method is also need for assessment of bearing capacity for module piles. Numerical modeling of piles was carried out in the Plaxis 2D program. The interaction of module piles with difficult of soil ground of West Kazakhstan is presented.

Study on model test of the new O-cell load test method with two loading directions

Aiming at the possible problems of the new O-cell load test method with two loading directions in engineering practice, the operability and feasibility of this new method is studied by using indoor model tests and finite element numerical simulations. According to the similar principle, three groups of the traditional static load test, the O-cell load test and the updated O-cell load test under the same working conditions are designed and poured to obtain the pile ultimate compressive bearing capacity for comparison. Strain gauges and optical fibers are also used to detect the strain of the outer surface of the pile and the soil layer around the pile. The research results show that based on the bearing capacity results of the traditional static load test, the results of the physical model under the updated O-cell load test are compared with the results under the O-cell load test. The deviation is reduced by 3.54%-7.34%. At the same time, based on the physical test, the finite element analysis shows that the longer the pile length, the greater the deviation reduction. When the pile length is twice the physical model test, the contrast deviation reduction value is 9.15 %-15.71%. The strain results in the physical test also reflect the mechanism of pile-soil interaction well, and there is also a deficiency that the position of the equilibrium point needs to be determined.

Prediction of mechanical behavior of reinforced concrete bridges following a fire based on the fire dynamics simulator–kriging model

AbstractThe performance degradation and degree of damage of bridge materials are more extensive at the fire source compared to other bridge locations. The traditional finite‐element model (FEM) modification method leads to a large error and is unable to achieve a good correction effect. In addition, as the traditional static load test method is used to evaluate the bearing capacities of bridges postfire, the risk of bridge damage, or collapse‐induced by secondary loading—remains unaddressed. To solve these problems, this paper proposes a modified FEM of a bridge following a fire based on the fire dynamics simulator (FDS)–artificial intelligence algorithm. The static behavior of a bridge is predicted using the modified FEM. First, a numerical simulation of a bridge fire is conducted using the FDS to obtain the temperature field distribution and determine the influence ranges of local design parameters of the bridge at the fire source. Second, a response surface model with a high fitting accuracy is constructed to modify the initial FEM by using the artificial intelligence algorithm proxy model together with dynamic load test results for the bridge postfire. Finally, the static behavior is predicted using the updated model. In this study, an actual hollow girder bridge postfire is taken as the research object, and the static behavior prediction results obtained via the proposed method are compared with the static loading test results. The results indicate that the response‐predicted value of the modified FEM is close to the measured value of the bridge postfire.

Proof Load Testing Method by the American Association of State Highway and Transportation Officials and Suggestions for Improvement

Because of the aging of infrastructure, methods are explored by which the reliability of existing bridges and viaducts can be assessed. In cases in which limited information of the structure is available or its condition is of concern, proof load testing may be used to demonstrate sufficient live load carrying capacity. Proof load tests in the U.S.A. are typically performed using the Manual for Bridge Evaluation (MBE) published by the American Association of State Highway and Transportation Officials (AASHTO). The proof load is expressed by the regular live load model magnified by the target proof load factor. The level of reliability obtained using the target proof load factor is not explicitly stated in the MBE, but is of particular interest. In this article, relevant background documents are investigated to uncover the underlying calculations, assumptions, and input data. Current challenges in proof load testing are described in which the considerations of time dependence, stop criteria, available information, and system-level assessment are highlighted. Subsequently, improvements to the MBE proof load testing background are suggested. An example calculation using traffic data from the Netherlands shows that the HL93 load model and Eurocode LM1 provide a reasonably constant proof load factor with span length for bending and shear. However, the HS20 load model does not scale well with increasing span length. It is found that the magnitude of the target load as specified through the proof load factor is directly related to the desired level of reliability. Although the MBE proof load testing method is practical, several challenges remain.

Load Test Method Using Two Power Supplies for High-Frequency Transformers

Load Test Method Using Two Power Supplies for High-Frequency Transformers

Experimental Study on Load of Continuous Steel Truss Bridge Stiffened by Rigid Suspension Cable for Highway and Rail

In order to reveal the stress law of rigid suspension stiffened continuous steel truss bridge under highway and crowd loads, a highway rail bridge is taken as the supporting project, and the load test method is used to verify it. Firstly, the completed bridge state (the dead load of the lower track) is simulated by laying water bags on the lower deck, which solves the problem of asynchronous construction of highway and track. Then, the stress, deformation results and change rules of this kind of bridge under the test load are summarized by simulating the load action of highway and crowd through the loading vehicle, which can provide a reference for the load test of similar bridges.