Dynamic Load Tests Research Articles

Accelerated Bridge Construction Case: A Novel Low-Carbon and Assembled Composite Bridge Scheme

Modern bridge construction towards a higher degree of low carbonization and assembly has been the general trend, while developing and broadening the low-carbon and assembled-oriented Accelerated Bridge Construction (ABC) technology can better realize the trade-offs between construction quality, efficiency, cost and sustainability. In the current mainstream ABC technologies such as precast-assembled concrete bridge and assembled steel bridge schemes, it is difficult to achieve an excellent balance between the above multicriterion trade-offs. To this end, this paper proposes a novel low-carbon and assembled composite bridge scheme as an innovative case of ABC technology based on a 26.7 km-length urban viaduct project in China with urgent environmental protection and assembly demands. Construction sustainability, the comprehensive economy and low-carbon performance are well balanced by the collaborative application of new steel–concrete composite structures, the rapid assembly interface design and low-carbon material technologies. The proposed scheme has been applied to a completed real-scale bridge, and the whole construction process only experienced 105 days of effective time, accompanied with slight environmental interference and construction noise and a small amount of labor and equipment input. In addition, the safety of the bridge, the rationality of the design concept and the calculation method have been verified by the static and dynamic loading tests of the real-scale bridge.

Three-Dimensional Discrete Element Analysis of Bearing Characteristics of Concrete–Cored Sand–Gravel Pile Composite Foundation under Cyclic Dynamic Load

Concrete-cored sand–gravel piles are a kind of composite pile formed by wrapping a concrete-cored pile with a sand–gravel shell, which has the advantages of both a rigid pile and bulk-material pile. The bearing characteristics of the concrete-cored sand–gravel pile composite foundation were investigated by establishing a three-dimensional discrete element numerical model for a cyclic dynamic loading test. The results show that the vertical stress of the core pile body fluctuates greatly at the beginning of loading, and the fluctuation amplitude decreases with the depth, and gradually tends to be stable in the middle and late stages, and the vertical-stress distribution is relatively uniform. The radial stress in the upper part of the core pile body fluctuates greatly, the fluctuation in the lower part is small, and the radial stress in each part of the core pile body gradually tends to be stable in the late-loading period. The radial stress factor of the core pile body reaches the stable speed with the foundation depth decreasing; the fluctuation amplitude of the pile-soil stress ratio decreases with the foundation depth and gradually tends to be stable with the increase in loading. The results of this study can provide a reference for the design and construction of a core sand pile composite foundation.

Static and dynamic responses of buried steel pipe under truck load: An experimental study

The behavior of a buried pipe under static and dynamic loading conditions has been investigated through full-scale field tests. A plain steel pipe with a diameter of 762 mm was gauged at the outer surface of two pipe sections. A dump truck was employed for the static and dynamic loading tests. Under static loading, the measured pipe strains increase with increasing axle load and decreasing cover depth. The measured strains under dynamic loading show three peaks, which correspond to the times at which the front, middle, and rear axles, respectively, reach the pipe centerline. The offset loading pattern produces greater strains than the non-offset one while keeping the axle load constant under both static and dynamic loads. It is discovered that the pipe strains caused by each truck axle vary with truck speed. Since the load transfer is influenced by a number of factors, including the truck load, road roughness, truck speed, and others, a moving truck load does not always result in higher pipe strains as compared to a static load. The complexity of dynamic pipe responses can be explained in part by a single-degree-of-freedom (SDOF) model.

Experimental Investigation on Mechanical, Electrical, and Fatigue Properties of Entangled Metal Wires under Cyclic Dynamic Load Test

Experimental Investigation on Mechanical, Electrical, and Fatigue Properties of Entangled Metal Wires under Cyclic Dynamic Load Test

Parameter identification and NVH characteristic analysis of automotive suspension rubber bushing

Accurate prediction of the dynamic stiffness of rubber bushings is crucial for optimizing vehicle vibration and noise performance. However, this task is highly challenging due to various influencing factors such as frequency and amplitude. Consequently, there has been limited research conducted in this area thus far. This paper presents a novel approach for predicting the dynamic stiffness of rubber bushings. The frequency and amplitude dependencies of rubber bushings were thoroughly investigated through dynamic loading tests. A comprehensive model for rubber bushings, incorporating parallel connections of elastic elements, friction elements, and higher-order fractional derivative viscous elements, was established. The model parameters were accurately identified using the GA-BP method. The results demonstrate that the proposed model exhibits a high level of precision in estimating dynamic stiffness across a frequency range of 0–200 Hz. In comparison to the conventional model, the proposed approach enables more precise computation of interior sound pressure response and enhances vehicle simulation accuracy.

Evaluation of Design Parameters (α and β) for Analysis and Design of Piles on Soft Clays

This paper presents the analyses of 12 prestressed concrete instrumented test piles (TPs) that were driven in different bridge construction projects of Louisiana as part of a load testing program. The 12 TPs were driven mainly in cohesive soils. Detailed soil characterizations including both laboratory and in situ tests were conducted to determine the different soil properties. The TPs were instrumented with vibrating wire strain gauges to be able to calculate the distribution of skin friction and end-bearing capacities separately. Static load tests and dynamic load tests were conducted on each TP after end of driving to calculate the ultimate load capacity. Fifty six soil layers exhibiting clayey soil behavior and sandy soil behavior dominated the remaining 15 soil layers. The total stress parameter (α) and the effective stress parameter (β) were back-calculated for each soil layer. The α values ranged from 0.22 to 1.80, and the β values ranged from 0.11 to 0.83. Regression analyses were performed on 42 soil layers (75% data) to develop an empirical model to predict α as a function of undrained shear strength. The remaining 25% of the data were used to verify the developed model, and good agreement was observed between the measured and predicted values.

Acoustic emission and failure characteristics of coal and rock under single-free-face true triaxial loading

The airside roadway is frequently identified as the predominant site for dynamical disasters involving coal and rock. For the assurance of safety in mining zones, it becomes imperative to understand the mechanical response and energy characteristics of the coal and rock system within the airside roadway during mining processes. A triaxial static and dynamic load test system was used to conduct compression experiments on coal and rock samples under single-free-face true triaxial loading at different loading rates. The research findings are summarized as follows: (1) The damage and failure of the samples gradually propagate from the free face to the deeper sections of the samples and evident stage characteristics. Revealed that the damage mechanism was “microfracture localization – localized region development through – overall instability.” (2) A rising loading rate impedes the coal and rock's ability to make adaptive adjustments, thereby amplifying the sample's resistance against crack development, and playing a positive role in stimulating coal and rock failure, and the coal and rock system changed from progressive stable failure to sudden instability failure. The mesoscopic failure pattern gradually evolves into inadequacy and irregularity. (3) Throughout the entire failure episodes of coal and rock samples, the predominant mode of failure is tensile. However, influenced by the loading rate, the principal failure mechanism transitions from tensile to shear during the Ⅳ stage of failure. (4) There is noteworthy congruence between the macrofracture sites and the spatial positioning of high-energy fracture episodes. This furnishing pivotal insights for preempting and control deep impact disasters.

Static Load Testing Of PCI-Bridges for Assessing Functional Suitability and Its Comparison with Dynamic Testing

To accommodate the rapid development of residential and commercial areas in the Bumi Serpong Damai (BSD) Region, Banten, the construction of the Kadisurung bridge is necessary to integrate road networks. Before being operational to ensure the safety of bridge users, load testing is conducted. Parameters that must be met in the testing include not exceeding the strain and deflection limits during operational conditions, including when maximum loading occurs. To assess the bridge's performance during operation, research was conducted on both sides of the central span (western side bridge, JSB, and eastern side bridge, JST) with static load testing carried out with gradually increasing loads up to 50% UDL (136 tons), followed by gradual load removal. At JSB, the maximum deflection at 100% UDL, estimated from the deflection at 50% UDL, was 39.92 mm, and at JST, it was 31.67 mm, while the allowable deflection was 43.3 mm. Based on the deflection parameters, the relative capacities of JST and JSB are expressed as 108.5% and 136.7% respectively, relative to their allowable capacities. This indicates that the estimated bridge capacity using static load testing parameters is 6%-10% greater than when using parameters from dynamic load testing. Thus, the bridge is deemed suitable for operation.

Application of Random Forest Algorithm in Estimating Dynamic Mechanical Behaviors of Reinforced Concrete Column Members

In this paper, an innovative method is put forward for estimating the dynamic mechanical behaviors of reinforced concrete (RC) column members by applying the random forest algorithm. Firstly, the development of dynamic modified coefficient (DMC) predictive models and the realization of the proposed method were elaborated. Then, due to the lack of dynamic loading tests on RC column members, a numerical model of RC columns considering the dynamic modification on flexural, shear and bond-slip behaviors was developed on the OpenSees platform, and the model accuracy and the effectiveness were verified with the available test results. Moreover, by comparing the simulated results of the hysteretic curve using numerical models with different complexities, the influences of dynamic modification and the deformation sub-element were investigated. Furthermore, a numerical experiment database was established to obtain the training data for developing the DMC predictive models of critical mechanical behavior parameters, including the yielding bearing capacity, ultimate bearing capacity and displacement ductility. Finally, the results of feature importance for different input parameters were studied, and the model accuracy was evaluated using the test set and available experimental data. It was revealed that the predictive models developed using the random forest algorithm can be employed to reliably estimate the dynamic mechanical behaviors of RC column members.

Dynamic Deflection Measurement on Stiff Bridges with High Piers by Preloaded Spring Method

The deflection dynamic load allowance (DLA) of stiff bridges with high piers requires sub-millimeter accuracy. New technologies such as the vision-based optical method and GNSS are not yet recognized for use in DLA measurements due to their smaller SNR. Presently, the scaffolding method is widely utilized for dynamic deflection measurements in dynamic load tests owing to the reliability of employing rigid contact. When scaffolding is not available, engineers have to resort to a suspension hammer system. However, the mass eccentricity of the hammer, stretched-wire length, and wind will decrease the measurement accuracy. To overcome these drawbacks of the suspension hammer method (SHM), a preloaded spring method (PSM) and the related stretched-wire-spring system (SWSS) are proposed in this paper. The dynamic deflection of the coupled vehicle-bridge-SWSS was obtained by vehicle-bridge interaction (VBI) analysis. The sensitivity parameters of the PSM were analyzed and optimized to minimize the measurement error. Indoor experiments and field dynamic load tests were conducted to validate the feasibility and accuracy of the PSM. Additionally, the differences in dynamic deflection measurements between the PSM and SHM in windy environments were compared. The results show that, in a windless environment, the DLAs of the PSM are affected by the spring stiffness, stretched-wire length, and stretched-wire section stiffness, independently of the preload force. When the wind speed is less than or equal to 8 m/s and the pier height is less than 30 m, the maximum deflection measurement error of the PSM is −2.53%, while that of the SHM is −15.87%. Due to its low cost and high accuracy, the proposed method has broad application prospects in the dynamic deflection measurement of stiff bridges with high piers.

Research on distributed strain monitoring of a bridge based on a strained optical cable with weak fiber Bragg grating array.

The foundation of an intelligent highway network is the construction of a high-density distributed strain monitoring system, which is based on sensing elements that can sensitively capture external information. In this research, the development and application for the structure of a novel strained optical fiber cable based on the weak fiber Bragg grating (wFBG) arrays are discussed. A modulation and demodulation solution of wavelength division multiplexing combined with time division multiplexing is developed by utilizing the property by which the wavelength of the strained optical fiber cable is periodically switched. Further, the strain transfer model of the optical cable is analyzed hierarchically using the theory of elasticity. The strain transfer coefficients of the overhanging region and the gluing region are combined to deduce the sensitivity model of the strained optical fiber cable. Moreover, the finite element technique is integrated to optimize the structural parameters of the optical cable for high-sensitivity or large-scale range. The strained optical fiber cable based on wFBG arrays is applied to a steel-concrete composite bridge. The static and dynamic loading tests show that the sensing optical cable can be monitored for strain variation in order to realize the functions of lane identification, weighing vehicle tonnage as well as velocity discrimination.

Coupled Vibration Analysis of Multi-Span Continuous Cable Structure Considering Frictional Slip

As important load-bearing structures, suspension cables have been widely used in suspension bridges, engineering ropeways, cable suspension systems and other special equipment. Their dynamic problems have always been a research hotspot. Especially for complex cable systems such as engineering ropeways and cable lifting equipment, there will be moving loads acting on multi-span continuous friction-slip cable structures, resulting in nonlinear coupled vibration. Therefore, few scholars have studied how to calculate the nonlinear coupling vibration effect between such moving loads and multi-span continuous cables considering friction slip. Therefore, this paper proposes the use of the combination of the direct stiffness method and the Newmark-β integration method to solve the nonlinear system of equations of motion, which can be derived from the coupled vibration response between the moving load and the main cable. The corresponding calculation program is prepared. Combined with the dynamic load test and simulation results of engineering cases, the correctness and reasonableness of the coupled vibration equations and the program can be verified through comparative analysis. The results show that the calculation results of the self-programmed program are in good agreement with the dynamic load test results, in which the maximum error of the vertical displacement in the span is −4.40% and 0.86%, and the error of the static calculation reaches −13.90%. The impact effect is more obvious when hoisting the weight out of the pulling cable, in which the impact coefficient of the main cable can be up to 2.0. The impact coefficient of the deviation of the cable tower is 4.0. During the traveling process of the moving load, the vertical downward deflection of the main cable at the action point is the largest, and the upward deflection is in the region of 0.2~0.8L from the action point.

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.

Comparison of Dynamic Amplification Factor of Deflection and Bending Moment of Highway Continuous Box-Girder Bridges by Mode Superposition.

There are differences between the dynamic deflection and bending moment (strain) in the same section of continuous girder bridges. However, the selection of the response for calculating dynamic amplification factors (DAFs), which are essential for bridge health monitoring and safety assessment, remains controversial. Modes may play a role in the relationship between the deflection DAF and the bending moment DAF in both numerical analysis and field tests. To investigate the distinctions between the DAFs of the deflection and bending moment in a continuous girder bridge, functional expressions of the DAFs were derived, taking into account multi-factor coupling under concentrated forces. The interaction effects of the mode and road surface condition (RSC), vehicle speed, bridge span length, and span number on the deflection DAF, the bending moment DAF, and the ratio of the deflection DAF to the bending moment DAF (RDM) of precast continuous box-girder bridges were analyzed using vehicle-bridge interaction. To ensure the accuracy of the DAF in numerical computations and experimental tests, two types of accuracy indexes and the corresponding cut-off modes were provided. Validation was conducted by performing dynamic load tests on two field bridges. The results indicate that different modes have a significant effect on the RDM of the mid-span section of a bridge. When considering multiple factors, the deflection DAF and bending moment DAF of the mid-span section increased rapidly with the considered modes and then stabilized. Statistically, the RDM of all nine bridges ranged from 1.00 to 1.12, indicating that the deflection DAF was greater than the bending moment DAF. The suggested cut-off modes can be utilized for efficient and accurate calculation of the DAF and response signal fidelity.

A proposed correlation between dynamic and static plate load test moduli for gravelly soils

ABSTRACT Egypt is currently developing huge housing projects at the New Capital, Alamein, and other Egyptian cities. These projects often require soil replacement for roads and buildings. Among the causes of problems observed in some housing projects in the last decade are improper type of soil replacement material and inadequate compaction. Pit-run gravelly soils are commonly recommended for soil replacement because they have the advantages of providing high stiffness, low permeability inherited from their fines’ content and wide availability in Egypt. It is common to use sand cone test and/or static plate load test (SPLT) to assess the quality of compaction. The sand cone test is simple, cheap and rapid; however, it is not reliable with gravel sizes usually found in pit-run gravel, which may exceed 38 mm. Although the SPLT is efficient to assess the quality of compaction and the deformation modulus, it is relatively expensive and time-consuming. The dynamic plate load test is a reliable solution to combine the advantages of both the sand cone test and SPLT. This research includes a detailed laboratory characterization of pit-run gravel collected from Suez deserts and a field testing program including static and dynamic plate load tests on pit-run gravelly soil carried out at several sites in the new capital of Egypt to obtain static and dynamic plate load tests moduli. A statistical approach based on percent of exceedance criterion is adopted to obtain a simple correlation between the static and dynamic plate load test deformation moduli.

Dynamic cyclic loading tests for investigating the influence of loading rate and axial force on the lateral response of RC columns

AbstractThe material properties of steel and concrete vary depending on the loading rate to which they are subjected. To realistically evaluate the seismic performance of reinforced concrete (RC) columns, it is necessary to simulate the loading rate that structures will experience during seismic events as accurately as possible. Real‐time dynamic testing is preferred over quasi‐static testing for this purpose. On the other hand, the seismic performance of RC columns also depends on the axial force applied to the column. However, due to the large axial stiffness of RC columns, accurately controlling the axial force during the test, particularly in real‐time testing, is challenging. Consequently, only a few component‐level dynamic tests have been conducted for RC columns. This study aims to explore the influence of axial force and loading rate on the seismic performance of RC columns. To this end, both slow and fast cyclic loading tests were conducted on square cross‐section RC columns subjected to four different axial forces. By utilizing a robust actuator control method along with a specially designed load transfer element, the axial force was successfully controlled, while the lateral displacements were imposed on the columns in real‐time. The results include lateral strengths, postyield responses, damage patterns, rebar strains, and their rates, all of which constitute unique experimental data that can contribute to a deeper understanding of the actual seismic response of RC columns.

Study on high temperature dynamic characteristics and mesoscopic simulation of HFRC under dynamic and static combined loading

The Φ50mm SHPB system was used to carry out three-dimensional dynamic and static combined loading tests on hybrid fiber reinforced concrete (HFRC) treated at different temperatures (25 °C, 200 °C, 400 °C) under different confining pressure ratios (0, 0.1, 0.2, 0.3). The temperature effect, confining pressure effect and failure characteristics of HFRC under impact load were studied. The effect of fiber was equivalently treated in mortar, and the meso-aggregate model of HFRC considering aggregate, mortar and interfacial transition zone (ITZ) was established. The simulation results were compared with the experimental results. The results showed that the higher the confining pressure ratio, the more significant the temperature effect of peak stress is. The higher the temperature is, the less obvious the enhancement effect of confining pressure on peak stress is. Compared with the influence of confining pressure on dynamic peak strain, the influence of temperature effect on dynamic peak strain is higher. The established three-dimensional meso-aggregate model and calculation method can accurately reflect the dynamic response characteristics of HFRC at different temperatures and confining pressure ratios. Prestress will affect the internal stress distribution of the specimen, thus affecting the compression failure characteristics of the specimen. The confining pressure can constrain the damage course of the specimen and has a good protective effect on the specimen.

Research on intelligent analysis device for dynamic error of electric energy

With the development of smart grids, the introduction of intermittent energy and the increase in dynamic loads have led to more and more dynamic characteristics of electricity loads in the grid. Intelligent energy meters that passed calibration under steady-state load may not necessarily meet the measurement error requirements under the excitation of dynamic load test signals, and some may even produce significant errors. At present, research on dynamic error testing of intelligent energy meters mainly focuses on establishing models of dynamic error testing signals, and the reasons for the generation of dynamic errors are still unclear. In order to analyze the sources of dynamic errors in intelligent energy meters, this article adopts a mechanism modeling method to establish a full system model of intelligent energy meters, in order to analyze the influence of model parameters of each unit on the dynamic errors of active energy, and provide important theoretical reference for further improving the dynamic error characteristics of energy meters. In addition, identifying the sources of errors has important application value for improving the algorithm of energy metering chips, optimizing the overall design of energy meters, and selecting energy meters in dynamic load scenarios for the power sector.

Gear Up for Change: Unveiling 3D Printing's Potential for Appliance Repair through Dynamic Testing of Gears

This study delves into the static and dynamic load testing of 3D-printed gears, addressing the potential of utilizing FDM 3D printing for repairing household appliances. The failure of electronic household appliances attributed to plastic gear malfunction has prompted an alarming number of products to be prematurely discarded due to a lack of available spare parts. The research emphasizes the transformative potential of 3D printing to streamline gear repairs, enabling rapid local production of gear replacements, and reducing costs and downtimes associated with conventional spare parts. PLA and ABS, the two most widely used 3D printing materials, underwent exhaustive static tests to determine maximum load-bearing capacities and accelerated fatigue tests to assess long-term performance. Results underscore the potential of the 3D printing process itself, highlighted by flexibility and shortened production timelines. However, limitations arise from the inferior mechanical properties of PLA and ABS as compared to traditional plastic gear materials such as nylon. PLA demonstrates promise under controlled temperatures but only with lubrication or metal contact, while ABS reveals inadequate mechanical and fatigue characteristics at higher torques.

A comparison between static and dynamic load tests of Tapered steel jacking piles in Baskarp sand

In this study, four full scale static compression tests were performed on a tapered steel jacking pile with diameters 76 mm and 89 mm in both dry and saturated soil conditions. Each test consists of multiple sub-tests with respect to determination of in-situ Baskarp Sand No.15 conditions and bearing capacities of the piles. Further, a finite element methodology has been developed to predict the load-displacement response of tapered piles installed in sand, incorporating the effects of jacking installation. The methodology is based on the identification of the failure mechanism and shear strain formation at failure around the pile as well as adoption of soil-soil interface elements. The nonlinear soil model parameters for a fully wished-in-place (fully-WIP) condition were obtained through piezocone penetration tests where various methods were applied to obtain the relative density, among which those providing best fit according to Jamiolokowski et al., (2003) were selected for further assessment. Finally, the hammer tests were performed from which the dynamic bearing capacities and the relation between static and dynamic bearing capacities were obtained.