Dynamic Load Tests Research Articles

Measures to Improve Seismic Resistance by Fuse Mechanism in Pier Structures

AbstractIn Japan, temporary pier structures are designed to withstand earthquakes in consideration of their short service life, and seismic inputs exceeding the design are also expected. In order to confirm the deformation behavior of the fuse mechanism in this temporary pier structure, a fundamental study was conducted using a model specimen. The strength test results showed that the fuse mechanism behaved similar to a rigid body, and then the mortar fuse failed. After the failure of the mortar fuse, the reaction force was generated by the addition of the residual bearing capacity of the mortar fuse and the reaction force of the coil spring. The dynamic loading test results showed that the CFT columns contacted the remaining portion of the fuse after the mortar fuse ruptured, temporarily increasing the maximum response acceleration to 35 m/s2, but the response period became longer, indicating the deformation behavior of the fuse mechanism. In addition, the maximum load of the mortar fuse mechanism and the natural period after the mortar fuse rupture were calculated from the design values of the mortar fuse strength and the spring constant of the coil spring.

Road Piezoelectric Power Output Model and Experimental Study under Bidirectional Vehicle Load Excitation

Recently, piezoelectric transducers have gained significant attention for energy recovery applications in road engineering. However, in laboratory tests, vehicle loads are often simplified using vertical vibration loads, thus ignoring the role of vehicle tangential loads. In this study, a power output model of a piezoelectric transducer under vertical and tangential loads was proposed through theoretical analysis. A bidirectional cyclic dynamic load test was conducted on the piezoelectric-concrete specimens in combination with a large dynamic and static straight shear instrument, and the power output law of the piezoelectric transducer under vertical and horizontal shear was investigated. The results revealed that the vertical vibration load was the main factor affecting the output performance of the piezoelectric transducer; however, with the addition of the tangential load, the electric energy output of piezoelectric pavement increased with an increase in the horizontal shear rate and displacement. When vibrating vertically (200 kPa and 4 Hz), the electric energy output of piezoelectric pavement was 4.979 μW. However, under the action of vertical vibration and horizontal shear with the working conditions of 200 kPa and 4 Hz, and 0.1 mm and 1 Hz, the electric energy output of piezoelectric pavement was 21.04 μW, which was 3.2 times that of the vertical vibration load alone. Therefore, by considering the influence of vehicle tangential loads, the power output of piezoelectric transducers can be calculated more accurately, which provides a reference for actual installed capacities in real engineering applications.

Developing a benchmark study for bridge monitoring

AbstractStructural health monitoring is the process of implementing a continuous damage detection strategy to optimize the inspection and maintenance schedules of bridges, and extend their lifespans. One of the main challenges of automated damage detection is the lack of data on damaged states, which makes it difficult to validate new approaches in the research and development stage. To alleviate this problem, a monitoring campaign on a two‐span test bridge with defined defects is conducted and documented in this article. The bridge is a steel‐concrete composite structure with a length of 30 m, with two primary steel girders and a segmented concrete deck. The recorded data capture the long‐term ambient data from 18 test days and changing environmental conditions, as well as the short‐term ambient data and dynamic load tests from four damage scenarios with well‐defined damage extents. A mobile measurement system with numerous sensors is used for data acquisition. A shaker is placed on the bridge to excite white noise. The main goal of this article is to document the experimental procedure and perform preliminary plausibility checks on the measured data. First results demonstrate that system response data and environmental conditions are recorded reliably and that environmental effects significantly affect the long‐term measurements. Therefore, a suitable data set is provided as open‐source data for future studies on data normalization and automated damage detection.

Modeling the dynamic magneto-mechanical response of magnetic shape memory alloys based on Hamilton’s principle: The numerical algorithm

This paper is the second part of a variational modeling work on the dynamic magneto-mechanical response of magnetic shape memory alloys (MSMA). In the first part of this series work, the governing equations system for modeling the dynamic response of MSMA samples has been derived based on Hamilton’s principle, which contains the Maxwell’s equations, the magneto-mechanic equations, the evolution equations of internal variables and the twin interface motion criteria. In this paper, we aim to conduct comprehensive numerical simulations on the dynamic magneto-mechanical response of MSMA samples. To solve the governing system, the space–time finite element method is applied and a double-loop iterative numerical algorithm is proposed. By using this algorithm, the independent variables in the governing system and the motion of twin interfaces in the MSMA sample can be determined separately and iteratively. Besides that, a specific discretization of the sample is adopted to simplify the calculation of variant state distribution in the sample. To show the efficiency of the numerical algorithm, the magneto-mechanical response of a MSMA sample in stress-assisted dynamic field loading tests and field-assisted dynamic mechanical loading tests are studied. Based on the numerical results, some global response curves of the MSMA sample are plotted, which show good consistency with the experimental results. Furthermore, the current configuration of the sample and the distributions of some important physical fields in the sample can be simulated. The current work will be helpful for the design of novel actuators or energy harvesters with MSMA.

Electrically conductive adhesive-free interconnection of shingle solar cells

This work deals with the usage of electrically conductive adhesives (ECA) for the interconnection of shingle solar cells. In a detailed study on small-format shingle modules characterized by current-voltage, electroluminescence and magnetic field imaging measurements, the impact of an ECA reduction (usage of ECA dashes instead of a continuous ECA line) as well as the complete omission of ECA is investigated with regards to the electrical interconnection quality. Inter alia, it is demonstrated that lamination can improve interconnection quality in ECA-containing shingle joints and establish interconnection in ECA-free shingle joints by pressing adjacent shingles together and thereby forming a busbar-to-busbar contact of decent electrical quality. In a follow-up experiment, the approach of simply omitting the usage of ECA for shingle interconnection is tested with regards to thermal cycling, damp heat and dynamic mechanical load tests finding only minor compromises, if at all, in terms of long-term stability.

Dynamic response and energy evolution of sandstone under combined dynamic and static loading

Impact disturbance and bedding angle have a substantial effect on the mechanical response of sandstone under prestressed loading. Therefore, in this paper, a combined 1D static and dynamic loading test system is employed for examining the compression of sandstone at various bedding angles under a pre-applied axial pressure of 25 MPa. Under these conditions, the strength, stress-strain curves, energy usage ratio, particle size and deformation of sandstone are obtained. The results are as follows. (1) Strain rebound easily occurs in high-strength sandstone under low impact pressure. (2) The peak strength of sandstone is positively correlated with the impact pressure. The peak strength and combined dynamic‒static strength of sandstone change in a "v" shape. (3) The rock's failure particle size is controlled by the bedding plane at low impact pressure. (4) We propose a new energy calculation method in which the energy utilization rate presents an approximately inverted "v" shape. (5) The sandstone with different bedding angles has different bursting liabilities at an identical impact pressure. (6) The impact pressure is proportional to the crack growth rate of sandstone.

Talon cannulated compression device as an alternative in the fixation of acetabulum posterior column fractures: A biomechanical study

To compare the amount of displacement and rigidity at the fracture line under static & dynamic axial loading and torsional stress of conventional cannulated screw (CS), plate screw fixation including inter-fragmentary screw (PL), and talon cannulated compression device or talon screw in other words (TS) in posterior column fracture models.Synthetic hemipelvis bone models presenting a posterior column fracture were used in this study. Group PL, CS, and TS were created with ten bone models prepared for each group for dynamic and static loading tests and another ten for torsional tests. Rigidity and displacement amounts before and after loading were measured at the reference points AL, BL, and CL, located at the acetabulum's top, middle, and bottom, respectively. Torsional tests for each group were used to calculate torsional rigidity and maximum torque values.In dynamic axial loading tests, Group CS showed more displacement than PL at the BL point (p = 0,032) and Group TS at AL (p = 0,032) and CL (p = 0,004) points. In static axial loading tests, Group CS significantly displaced more than TS at AL and CL points (p = 0,05 and p = 0,014, respectively). Group PL and Group TS exhibited similar behavior in dynamic, static axial loading tests and torsional rigidity. The maximum torque that Group PL could withstand was statistically significantly higher than the other two groups (p <0,001).Talon cannulated screws had promising results in posterior column fractures of the acetabulum, which may decline the need for open surgery for stable fixation.

Time-Dependent Reliability Analysis for Deflection of a Reinforced Concrete Box Girder Bridge

Prior to casting of concrete, proper supervision and attention to camber provision in bridge construction are required. It is also critical to use an appropriate quality control manual, pay due attention to reinforcement bar placement, and have a high level of formwork design before construction begins. If these issues are not properly addressed, performance of structures will be affected. In this research, performance of a 40.5m box-girder reinforced concrete bridge which was constructed without having proper camber is studied. As camber was the most important issue of the bridge under investigation, the impact on strength and serviceability requirements is compared to the standard. A dynamic load test with an Arduino type accelerometer is performed to assess the bridge's current condition in relation to the serviceability limit requirement. The deterioration of reinforced concrete (RC) sections due to reinforcement corrosion, creep, and an increase in load intensity, as well as the corresponding statistical distributions are considered to estimate the long-term effect of bridge deflection. The time-variant analysis results show that a linear decrease in deflection reliability indices with the bridge's expected service life of 58 years and strengthening it increased to 85 years.

Quality control of fine-grained embankments using penetration tests

The compaction control of earth works is an essential task in geotechnical engineering. In order to build more sustainably and to reduce project costs, fine-grained materials are more often used for embankment construction nowadays. The quality control of compacted soil layers is usually defined in terms of deformation moduli obtained from static and dynamic plate load tests or based on the degree of compaction, which is generally related to the Proctor density. Penetration tests, such as cone penetration tests (CPT), seismic flat dilatometer tests (SDMT) or dynamic probings (medium heavy dynamic probings (DPM)), show a potential for assessing the compaction along vertical profiles but no standardized quality criteria have been elaborated yet. The present work investigates the effects of different water contents and degrees of soil stabilization on results of CPT, SDMT, DPM, plate load tests and Proctor tests for an 8 m high trial embankment, characterized by a clayey to silty material. CPT and DMT results were found to strongly correlate with deformation moduli of static and dynamic plate load tests, enabling the definition of new quality criteria for compaction control.

Dynamic Mechanical Properties and Damage Evolution Characteristics of Beishan Deep Granite under Medium and High Strain Rates.

To study the dynamic mechanical properties and damage evolution mechanism of Beishan deep granite under medium and high strain rates, dynamic mechanical tests for the deep granite specimens with different strain rates were conducted using the split Hopkinson pressure bar (SHPB) device. The improved Zhu-Wang-ang (ZWT) dynamic constitutive model was established, and the relationship between strain rate and strain energy was investigated. The test results show that the strain rate in the dynamic load test is closer to the strain rate in the rock blasting state when the uniaxial SHPB test is applied to the granite specimens in a low ground stress state. Peak stress has a linear correlation with strain rate, and the dynamic deformation modulus of the Beishan granite is 152.58 GPa. The dissipation energy per unit volume and the energy ratio increase along with the strain rate, whereas the dissipation energy per unit volume increases exponentially along with the strain rate. There is a consistent relationship between the damage degree of granite specimens and the dissipation energy per unit volume, which correspond to one another, but there is no one-to-one correspondence between the damage degree of granite specimens and the strain rate. To consider the damage and obtain the damage discount factor for the principal structure model, the principal structure of the element combination model was improved and simplified using the ZWT dynamic constitutive model. The change of damage parameters with strain rate and strain was obtained, and the dynamic damage evolution equation of Beishan granite was established by considering the damage threshold.

Static and dynamic compression load tests of conically connected, screw fixed dental abutment

The basis of the long-term success of dental implants is the mechanical stability of the implant and the superstructure anchored in it. In order to investigate the mechanical behaviour of the conical connection in implant-abutment units, static and dynamic load tests were performed with different conical angles and various Grade 4-5 titanium implant materials. The assembled units were mounted in self-developed loading machine and in an Instron ElectroPuls E3000 fatigue machine. For static loading, the samples were loaded with a force from 0 N to 500 N in steps of 100 N. For dynamic loading, the samples were loaded for 30,000 cycles with a force of 250 ± 150 N. In case of static testing, the compression caused by the load was measured in both horizontal and vertical directions, while in the case of dynamic fatigue, only horizontal deformation was defined. In both cases, the drive-out (reverse) torque values of the fixing screws were determined after loading. No significant differences were found between the tested materials in the reverse torque after the static load, however, significant differences were shown with regards to the alterations in cone angle (p &lt; 0.001). After dynamic loading, significant differences (p &lt; 0.001) were also observed between the reverse torques of the fixing screw in different angles. The static and dynamic test results showed the same tendency: under the same load conditions, the conical angle value of the implant-abutment connection revealed significant differences in the loosening of the fixing screw. In summary, it is recommended to use higher conical angle connection to avoid larger deformations in lengths and diameters of the implant at the connection and essential torque reduction of the fixing screw. Our results may contribute to the understanding of the long-term success of dental implants.

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.

Effects of fiber type and yarn production technique on pile yarn and carpet performances

Pile yarns, which are commonly used for machine-made carpets, are produced from fibers such as wool, polypropylene, acrylic, polyamide, and polyester by using different yarn production techniques. In this study, drawn textured polyester pile yarns (DTY), bulked continuous polyester pile yarns (BCF PES), and bulked continuous polypropylene pile yarns (BCF PP) were produced with trilobal cross section, same number of filaments and linear density. In order to determine optimum fiber type and yarn production technique for machine-made carpets, both physical, thermal properties of pile yarn samples and resilience, appearance retention of carpet samples were investigated. Breaking strength-elongation, crimp contraction and shrinkage tests, were applied to the pile yarn samples. Compression/recovery, dynamic loading, static loading, hexapod tumbler, and soiling tests were also carried out to analyse carpet resilience and appearance retention performances. According to the yarn physical test results, it was revealed that pile yarn samples have similar performance and DTY samples have highest crimp contraction and shrinkage values among all pile yarn samples. Better compression/recovery properties and less thickness loss after dynamic and static loading tests were observed with DTY PES carpet samples. However, BCF PP carpet samples showed better resilience behaviour than other carpet samples. Hexapod test results showed that DTY PES carpet samples have the best appearance retention results. For soiling performance, it was observed that there was no significant difference between the carpet samples.

STATIC AND DYNAMIC TESTS OF METAL PILE-SHELLS OF A SEA PIER MARINE TERMINAL

The behavior of the piles in the engineering and geological conditions of the construction water area of a new two-way pier of the berth on the territory of the sea trade port of Chornomorsk as a part of the expansion of production capacities for transshipment of grain, food products, processing of oil and grain crops was studied. During the construction, it is envisaged to use shell piles made of metal pipes 35.0...42.7 m long with the outer diameters 1020, 1220 and 1440 mm. The layers include Neogene sediments of the upper Miocene subdivision of the Sarmatian and Meotic horizons, which are represented by clayey soils from plastic to hard consistency with the lenses of silty sands saturated with the water and the interlayers of limestone. The piles cut through the sporadic layering of loams and clays, and their bottom ends are stopped in clay and dusty sands. A comprehensive approach to conducting the control tests of the piles was developed, which included conducting the tests in two stages. At the first stage, a group of four piles with the diameters 1020 and 1220 mm were tested under both static and dynamic loads at the construction site on the first supporting structures. The values of η and М coefficients, which are used to determine the bearing capacity of metal pile-shells during the dynamic tests under special geological conditions, were adjusted. At the second stage, only dynamic loads were tested on the rest of supporting structures. The inventory metal beam was as a jack pad when testing the piles with static loads, which was fixed to the anchoring piles with the welded terminations, and the movement of the head was recorded by deflection gauges. Pile driving during the dynamic load test was performed with a hydraulic hammer, which was used for their driving. According to the received data analysis of the pile test results with static and dynamic loads, it was determined that in order to obtain the values of allowable pile design loads, close to those ones determined by the static test results, it is necessary to adjust the values of η and М coefficients. It was established that for metal pile shells, which driven in the marine environment, when their bearing capacity is determined based on the results of test comparisons with static and dynamic loads, the coefficient η should be taken as 2500kN/m2, and М=1.0 – when the bottom end of the pile stopped in clay soils and M=1.6 – when in the sand.

Performance-based blast-resistant design of RC bridge piers under vehicular bombs

Bridge piers are the critical components to support the superstructures and the blast resistance of piers has attracted extensive attention considering the ever growing deliberate and accidental explosion attacks on bridge structures. However, most of the existing studies focus on the blast-induced dynamic response of a single pier without considering the bridge redundancy, even less the actual traffic performance of the entire bridge. This paper aims to propose a performance-based blast-resistant design approach of RC bridge piers under explosions of vehicular bombs. Firstly, the distribution model of blast impulse on bridge piers is proposed with considering both the ground reflections and diffractions of piers based on the validated finite element analysis (FEA) approach. Then, the fiber beam element-based model and the above blast impulse distribution model were validated based on the dynamic monotonic loading test and the explosion test on RC frame column. Furthermore, the simplified fiber element beam-based prototype RC bridge was established and the parametric studies were performed. Finally, the response surface methodology was adopted and the performance-based blast-resistant design procedure for three design basis threats specified in FEMA, i.e., cargo van bomb, small moving van bomb, moving van bomb, was proposed with utilizing the relative vertical displacement of the mid-bent as the performance index. It derives that, (i) the proposed distribution model of blast impulse is applicable to explosions at scaled distances of 0.5–2.1 m/kg1/3; (ii) the fiber beam element-based model can well describe the global response of the blast-exploded columns/piers; (iii) the proposed performance-based blast-resistant design approach can provide an efficient tool for bridge engineers.

Investigation on permanent deformation of unbound granular material base for permeable pavement: Laboratory and field study

• Deformation of Unbound Granular Materials was investigated in laboratory and field synchronously. • The confining pressures and Shear Stress-strength Ratios affect the deformation greatly. • The deformation prediction model was consistent with the trends of laboratory test results. • A deformation model based on laboratory triaxial load tests, dynamic triaxial repeated load tests and filed LWD tests was developed. Unbound Granular Materials (UGM) base is widely used in permeable pavement structure for infiltration, water storage, and load bearing. However, because of large void content, UGM base easily deforms under repeated loads, resulting in surface rutting and even reducing durability of permeable pavement. Thus, research on practical deformation prediction model of UGM base is necessary to improve the pavement structure design and evaluate the base layer construction quality. This study conducted laboratory and field tests to develop a deformation prediction model of UGM base under varied stress states. The deformation of UGM specimen was tested and analyzed through triaxial shear test and dynamic triaxial repeated load test, with varied confining pressures and Shear Stress-strength Ratios (SSR). A laboratory deformation model based on SSR was developed, and the linear relationship between total deformation and permanent deformation was obtained. The deformation of UGM base in situ was tested with Light Weight Deflectometer (LWD). The trends of laboratory deformation model and field test results were similar, and deformation prediction model for field was fitted. The values of parameters in permanent deformation model were recommended in varied stress ranges, based on mathematical analysis. Accordingly, the deformation of UGM base can be estimated. This study developed a model to estimate the permanent deformation of UGM based on deformation data from field and laboratory tests.

Full-scale model testing of a graded crushed stone sandwich structure within the ballastless track subgrade

ABSTRACT This paper aims to analyse the static and dynamic characteristics of the sandwich structure consisted of an upper ballastless track structure layer, middle graded crushed stone interlayer, and lower foamed concrete subgrade layer, and clarifies its long-term dynamic stability. A full-scale test model of the sandwich structure being optimized was established, and then the static and dynamic loading tests were carried out. The results show that the use of foamed concrete as the subgrade filler can make the sandwich structure subgrade have better static stress and vibration diffusion effect compared with the traditional ballastless track subgrade. Under the loading conditions of this model test, the sandwich structure does not produce a resonance phenomenon when the loading frequency increases from 1 Hz to 10 Hz. And the sandwich structure has good vibration characteristics and long-term dynamic stability under cyclic loading. All these indicate that the graded crushed stone sandwich structure of the ballastless track foamed concrete subgrade can provide a smooth and long-term stable foundation for the line.

Experimental, Theoretical and Numerical Research Progress on Dynamic Behaviors of RC Structural Members

In this paper, research on dynamic behaviors of RC structural members was reviewed using experimental, theoretical and numerical perspectives. First, in a basic overview, measurement methods, main conclusions and current limitations of available dynamic loading tests were presented. Then, theoretical studies on the dynamic constitutive models of RC materials, the dynamic increase factor (DIF) model for concrete and reinforced steel and proposed modified models of dynamic behavior parameters at the structural member level were summarized. Finally, the available modeling approach and method for incorporating dynamic effects in numerical simulations of RC structures were reviewed. Moreover, the work involved a brief introduction to a dynamic hysteretic model established using experimental data, which was designed to provide an alternative approach to the commonly-used DIF method for considering these dynamic effects. This paper, therefore, aimed to provide a valuable reference for experimental studies and numerical simulations on the dynamic behaviors of RC structures—while also putting forward issues that need to be addressed by future work.

Predicting driving transferred energy without needing the hammer efficiency: three case studies

This study presents case studies on the implementation of an innovative method of calculating effective driving energy with no need to account for hammer efficiency. The approach is based on measurements of set and elastic rebound, as well as a site-specific parameter (λ) calibration. The study applied this method to steel piles located in the cities of Santos (SP), Itaguaí (RJ), and Óbidos (PA), with the latter site being built in the Amazon region, near the Amazon River. Following coefficient calibration, the effective driving energy estimation technique exhibited a strong correlation with realistic and accurate energies directly obtained from dynamic loading tests. The method provides a highly accurate means of calculating effectively transferred energy to piles due to hammer blows, without relying on knowledge of the driving system performance. In that way, it can be applied to all the piles at the site (100% of them), including those that are not tested. This optimized and agile approach represents a significant breakthrough in foundation engineering and an enhance of pile foundation quality control.

Study of Cross-Scale Micro-Motion Wear Characteristics of Metallic Rubber

Abstract Metal rubber (MR) is a kind of elastic porous material with a complex and disordered internal structure, which results in wear characteristics that can only rely on tests but cannot meet the engineering application. This paper presents an exciting method for studying wear characteristics based on its virtual fabrication technology. By developing the intricate internal multipoint random contact mesh model of MR, a virtual real-time dynamic tracking contact point in a different state is captured. A thorough investigation is conducted into the contact point properties, point distribution, and the interaction of discrete contact points in MR interior space. Accordingly, a cross-scale micro-motion wear study method from micromorphology to macroscopic performance is proposed. The continuous wear cycle of MR is discretized into multiple single-turn metal wire elements by applying the principle of equal spacing. A statistical model of internal contact point wear of MR at the microlayer is developed considering the metal wire’s single-turn fretting wear prediction model. The cumulative prediction model of macroscopic wear damage of MR is based on the superposition of micro-element interval. Finally, the difference between the mass loss and that obtained from the simulation analysis after performing dynamic loading tests at different cycles was studied and found to be insignificant.