Dynamic Field Tests Research Articles

Estimation of shear wave velocity using rock mass property of Gemlik, Turkey

ABSTRACT It is often required to evaluate the shear wave velocity (V s ) of the sub-soil stratification for the seismic site characterisation and various engineering applications where the dynamic forces are acting on the foundation. Different correlations are available based on the Standard Penetration Test (SPT) for this purpose when the sub-soil stratification consists of soil. However, limited studies were performed to develop such correlations in case of weathered and fractured rock formations. In this paper, a correlation is developed between the depth of measurement, shear wave velocity, and Rock Mass Rating (RMR) based on Multichannel Analysis of Surface Waves (MASW) test, and the borehole data conducted in the Gemlik region of Turkey. The accuracy of the proposed correlation is checked using different statistical plots and found to be acceptable for the evaluation of V s . This correlation can be used by the practicing engineers for the preliminary estimate of V s in a fractured rock mass based on the borehole information and laboratory testing in absence of dynamic field testing for this region. Based on the findings from this study, V s is observed to be increasing with an increase in depth of investigation and RMR in a fractured rock mass of Gemlik, Turkey.

Research on the mechanism and measures of riding comfort deterioration in a low floor tram

With the global widespread preference for low-floor trams, the expectation for tram riding comfort has been increasingly heightened. This paper identifies an abnormal riding comfort problem (ARCP, characterized by an excessive and W-shaped distribution of riding comfort) during dynamic field tests on a low-floor tram. To address ARCP, a multi-body dynamics model of the tram was constructed and validated its accuracy through dynamic field tests. By integrating track irregularities and wheel-rail contact analysis, the riding comfort index was assessed and reproduced the ARCP phenomenon. Linearization and time-domain integration studies were conducted on the mechanisms and measures to resolve the ARCP. The research findings reveal that the primary cause of the deterioration in the mean comfort index is the large amplitude of the track irregularity and the low equivalent conicity of the wheel-rail contact relationship. The main reason for the W-shaped distribution of riding comfort is the weaker inter-vehicle constraints and the lack of lateral energy-absorbing devices. Finally, optimization measures were proposed, including reducing the lateral stiffness of the second suspension, altering the carbody structural parameters, and modifying the inter-vehicle connection devices. This research enriches the study of tram dynamic performance and offers insights that may contribute to the resolution of ARCP.

Strategic Placement of Accelerometers for Structural Health Monitoring of a Complex Unreinforced Stone Masonry Hindu Mandir

ABSTRACT The BAPS Hindu Mandir, recently constructed in Abu Dhabi, UAE, is a complex unreinforced stone masonry structure built from thousands of sculpted sandstone and marble pieces employing ancient Indian techniques called Shilp Shastra. The entire structure is substantially large with a footprint size of 5,100 m 2 and unique so that it is not covered by modern seismic design standards. Its performance was verified by conducting dynamic field tests presented herein. The most vulnerable substructure was identified based on both engineering judgement and modal analysis of the entire structure employing a detailed 3D finite element model, which was validated via the field experiments. A “local” model was developed for the identified vulnerable substructure which significantly reduced model complexity and allowed to overcome computational limitations. Based on the response of the local model, the relative importance of the sensor locations was determined via a Displacement Index method in addition to a reduction of the total variance of spectral accelerations using conditional probability theory. Through this approach, a methodology for selecting the optimal sensor placement with application on the complex unreinforced stone masonry Hindu Mandir is proposed.

Dynamic impact of unsupported sleepers on railway infrastructure with a coupled MBD-DEM-FDM model

This paper introduced a numerical simulation model of vehicle-track-substructure system, which combines the multi-body dynamics method (MBD), the discrete element method (DEM) and the finite difference method (FDM). In this model, rail, fastener, sleeper and ballast particles were built based on the DEM by using Particle Flow Code (PFC) software, substructure (including subgrade and foundation) was built based on the FDM by using Fast Lagrangian Analysis of Continuum (FLAC) software, and the vehicle was built based on the MBD by self-programming. Here, two-way coupling calculation is implemented to satisfy the force equilibrium and displacement compatibility between railway components established by different method. And then, this coupled MBD-DEM-FDM model was validated by comparing the results with those from the classical vehicle-track dynamic model (VTCD model) and field test results. Afterward, the influence of unsupported sleepers on meso and macro dynamic behaviour of railway infrastructure was investigated. The coupled MBD-DEM-FDM model possesses the capability to accurately simulate the interaction between trains and tracks, analyze the meso mechanical responses of railway infrastructure, and capture significant subgrade deformations. Consequently, the proposed model offers a comprehensive understanding of the deterioration processes within railway infrastructure.

Investigation of the influence mechanism of shield on the strong magnetic field during electromagnetic launch

The electromagnetic launch process generates low-frequency pulsed magnetic fields with peak values reaching Tesla-levels, imposing greater demands on the interference immunity of electronics within projectiles. However, during the propagation of low-frequency pulsed strong magnetic fields, their characteristics are affected by the shielding properties of the surrounding medium materials, resulting in modifications to the actual internal magnetic fields of the devices. This paper presents a theoretical analysis, numerical simulation, and experimental investigation based on the shielding mechanisms of conductive and magnetic materials to elucidate their impact on the pulsed magnetic fields. Additionally, leveraging previous work on electromagnetic railgun projectile magnetic field calculations, the shielding model is established to determine the shielding effects of different material combinations on the magnetic field during electromagnetic launch. The results reveal that both conductive and magnetic materials influence the amplitude, pulse width, and initiation time of the pulsed magnetic field, a finding validated through dynamic projectile-borne magnetic field testing.

Inspection, structural analysis, and assessment of the existing condition of the tunnel beneath the National Palace of Culture, Sofia, Bulgaria

The current paper considers and summarize the elaborated inspection of the existing condition and operational capacity of the structure of a tunnel beneath the National Palace of Culture and together with the collected data and conclusion concerning the capacity of the top slab of the structure to undertake an additional load from a secondary track from a light rail load. It also includes an assessment concerning the durability of the structure and the compliance with the regulation requirements. The report includes - review and analysis of the available design and other documentation for the site; Surveying and scanning of the main structural elements, incl. localization and registration of visible defects of the structure; performing static and dynamic field testing; structural analysis and calculation of the actual bearing capacity of the reinforced concrete slab of the tunnel according to the regulatory requirements.

Evaluation of the Wind Field and Deposition Effect of a Novel Air-Assisted Strawberry Sprayer

Strawberry is a widely cultivated cash crop in China. In order to control pests and diseases on strawberries, there must be sufficient deposits on the abaxial surfaces of the leaves. Air-assisted technology can effectively increase the deposition on the abaxial surfaces of the leaves; however, most air-assisted equipment is not suitable for application due to the pattern of strawberry planting. Therefore, a novel air-assisted strawberry sprayer was developed, the static and dynamic wind fields were measured using a 3D anemometer, and the effectiveness of the application at different spray angles and wind speeds was evaluated. In addition, a comparison of the deposition effect in the strawberry canopy between the air-assisted strawberry sprayer, knapsack sprayer, and spray gun was conducted. The results showed that in the static wind field test, a difference between the center and edge wind fields was obtained, which was correlated with the distance and the outlet wind speed. In the dynamic wind field test, the wind field was found to be rolling backward during the movement, and an inward vortex was obtained. In the field, the data showed that a spray angle of 30° and a wind speed of 16 m·s−1 had the best deposition on the abaxial surface, with a coverage of 36.5% and 38.3% in the upper canopy and 6.2% and 7.9% in the lower canopy, respectively. Moreover, the air-assisted strawberry sprayer was found to have a higher deposition efficiency on abaxial surfaces than the knapsack sprayer and spray gun at a lower spray volume, the values of which in the upper and lower canopies were 42.8% and 29.7%, respectively. In conclusion, the air-assisted strawberry sprayer has the potential for the crop protection of greenhouse strawberries, and more evaluations are needed to improve the sprayer in the future.

Carrier Phase Ranging with DTMB Signals for Urban Pedestrian Localization and GNSS Aiding

China developed its Digital Television (DTV) standard in 2006, known as Digital Television Terrestrial Multimedia Broadcasting (DTMB), which employs time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) as the modulation method. In contrast to Global Navigation Satellite Systems (GNSSs), DTV signals have higher transmitting power, wider coverage, larger bandwidth, and fixed transmitter location. This paper explores the positioning performance of DTMB signals, and the potential to improve GNSS positioning accuracy in urban environments. Specifically, a solution is proposed, and a software-defined radio receiver is developed for wireless localization. Without changing the current signal structure, the pseudorandom noise (PN) sequences in the signal are used for signal acquisition and carrier phase ranging. The carrier phase of the first arrived path is extracted by the least squares matching pursuit method. Both static and dynamic field tests were conducted to verify the proposed ranging and positioning method. Centimeter-level ranging accuracy was achieved in the static scenario, while meter-level ranging accuracy was achieved in the dynamic scenario. As one possible application, the proposed ranging method was combined with GPS pseudorange measurements to achieve higher accuracy position results in an urban pedestrian scenario, especially when there is only a limited number of visible satellites.

Real-time measurement on dynamic temperature variation of asphalt pavement using machine learning

Temperature segregation of asphalt mixture is one of the major reasons for pavement damage. The premise of ensuring desired properties of the asphalt mixture is to propose a reliable measuring method to monitor temperature variations before paving. Few existing studies focus on this issue due to the absence of suitable and efficient measuring instruments. This study proposes an innovative method to evaluate the temperature variation of asphalt mixture throughout the transportation process by combining the infrared camera and machine learning algorithms. Static and dynamic field tests are performed to measure the contact and non-contact temperatures of the asphalt mixture. A set of temperature measuring probes is specially designed. Influences of the measuring depth, measuring location, and environmental conditions are considered. Correlations between the infrared temperature and the contact temperature are identified using regression model, Support Vector Regression (SVR), and Extreme Gradient Boosting (XGBoost). The accuracy of the proposed model is verified against the experimental result.

MLC performance prognosis using a degradation model based on trajectory log data from a daily test.

This paper investigates the feasibility of implementing a predictive maintenance program for a multileaf collimator (MLC) based on data collected in trajectory logs (TLs) obtained by conducting a simple daily test, with the aim of minimizing unscheduled downtime. A dynamic field test was designed, and the TLs generated in the course of daily administration in a linear accelerator were collected to evaluate trajectory deviations of the MLC leaves as well as interlocks (COL 420219/20, COL 420207/08) reported by the machine. During this evaluation, we observed that the trajectory deviations of some leaves increased up to a threshold value beyond which certain interlocks began to appear in treatment fields in those leaves. An exponential degradation model was therefore developed to predict this drift and determine each leaf's remaining useful life (RUL). Once the applicability of the model was confirmed, we added a second accelerator equipped with an MLC with the same configuration to validate the model. The model was able to predict certain COL 420219/20 interlocks resulting from primary readout/expected position discrepancies and to estimate each leaf's RUL. In total, 11 cases (8 interlocks + 3 potential interlocks avoided due to service interventions [27.3% of the total]) were detected over 7 days in advance, with no false positive results. Scheduling of service interventions several days prior to MLC failure would therefore be possible. When these types of interlocks were not predicted by the model, they were always generated by leaf motor failure. Consequently, intervention time could also be optimized by directly replacing the motor. During the study period, for these types of interlocks, our approach would have reduced downtime from 35.25 to 4.00h (88.7%) and from 34.75 to 22.83h (34.3%) for each accelerator, respectively. For COL 420207/08 interlocks, which are generated by primary/secondary readout discrepancies, no correlation with leaf trajectory deviation increases recorded in the TLs was found. Throughout the study period, these types of interlocks requiring service intervention, also mainly for motor replacement, represented a downtime of 9.50h for the first accelerator (21.2% of total downtime) and by 4.33h (11.1% of total downtime) for the second accelerator. This study demonstrates that by applying a predictive MLC maintenance program based on information collected in TLs, it is possible to predict certain interlocks and therefore schedule preemptive interventions to avoid their occurrence. This could optimize health-care delivery performance and minimize the loss of treatment sessions.

Highly discriminative simultaneous measurement of level, refractive index and temperature of liquid by dual-wavelength fiber ring-cavity laser sensor

In this paper, a novel dual-wavelength fiber laser sensor is proposed and completed by the parallel configuration of modified fiber Bragg grating and modal interferometer. The stable lasing emissions are realized and the comprehensive tests are performed in terms of level, refractive index and temperature of liquid. By the demodulation of joint wavelength and intensity matrix, high-discriminative simultaneous measurement is achieved, and the obtained sensitivities are 19.88 pm/°C, 159.32 dB/RIU and 568 pm/mm, respectively, with the errors below 2.52 %. Additionally, the dynamic field tests are performed, and the limits of detection of 0.15 mm, 0.42°C and 9 × 10-4 RIU are experimentally verified.

The Normative Effect of Harmonic Loads on Pile Group Depends on the Characteristics of Dynamic Response

Pile-supported machine foundations are examined in this work to identify the dynamic features of linear and nonlinear theories. A three-pile group with a 3 m pile length and an outer diameter of 0.114 m is given axial harmonic loading before field-based forcing vibration testing. For four distinct eccentric moments, tests are carried out at a static load of 12 kN. Each eccentric instant's reaction in terms of frequency and amplitude is examined. The continuum approach technique is also used for theoretical analysis, which employs both linear and nonlinear solutions. All of the eccentric moments' dynamic field test findings are compared to theoretically expected frequency-amplitude responses. In comparison to the actual test findings, the linear solution's anticipated responses show lower resonant amplitudes and substantially higher resonant frequencies. The dynamic response curves predicted by the nonlinear solution fit the test findings rather well in this situation. To achieve this degree of agreement with nonlinear analysis results, precision in border zone parameters and soil-pile separation lengths was necessary.

Investigation of Time-Varying Cable Tension of Bridges Using Time-Frequency Reassignment Techniques Based on Structural Health Monitoring Data

Cables have been increasingly utilized in modern long-span or tied-arch bridges as the main bearing structures. Real-time identification of time-varying cable tension is essential for assessing the service performance of bridges. Vibration-based methods have been an increasing research focus in recent decades. However, a long time interval is needed to estimate structural frequency using vibration-based methods, increasing the calculating time of cable tension. The time-varying cable tension is thus difficult to extract. This study proposes a time-frequency reassignment-based algorithm to reduce the detection time to address this issue. Combined with a time-frequency analysis tool and vibration theory of cables, the algorithm can identify the time-varying frequency and further quickly calculate the time-varying cable tension within 12.8 s. The features of the proposed algorithm are mainly threefold: identifying the time-varying frequencies with high precision; without some prior knowledge of vibration; having no other requirements for sensor modes. Moreover, the experimental validation is conducted using a quasi-static loading in a workshop and a dynamic field test on Sutong Bridge, respectively. The results show that the proposed algorithm can be used to identify time-varying tension and assess the service performance of cables, providing a new path for real-time condition monitoring of bridges in service.

Selective adsorption of trace gaseous ammonia from air by a sulfonic acid-modified silica xerogel: Preparation, characterization and performance

The toxic and corrosive gaseous ammonia (NH3) poses serious environmental and health risks. However, removal of low concentration NH3 from air remains challenging. In this work, a SO3H-modified silica xerogel (MPTS-X) with good porous structure stability and abundant Bronsted acid sites was fabricated, and its physicochemical properties and adsorption performance for NH3 were systematically investigated. Static adsorption experiments showed the MPTS-1.0 had high NH3 adsorption capacity of 4.02 mmol⋅g−1 at 0.1 bar and 7.00 mmol⋅g−1 at 1.0 bar, which was much higher than that of MPTS-0 (3.19 and 1.95 mmol⋅g−1). Langmuir-Freundlich isotherm model fitted the experimental data of NH3 adsorption well, implying that the MPTS-1.0 surface is not homogeneous and there are different adsorption sites, which was further confirmed by temperature programmed desorption spectrum analysis. According to IAST calculation, the adsorption selectivity of MPTS-1.0 for NH3/N2 (1: 9) and NH3/CO2 (1: 1) was 6175 and 165 at 1.0 bar, respectively, indicating the MPTS-1.0 has excellent adsorption selectivity. Dynamic adsorption experiments and field test demonstrated the MPTS-1.0 could quickly capture trace NH3, even if the initial concentration is as low as 2 ppm. Successive adsorption–desorption experiments demonstrated the MPTS-1.0 had good regenerability. In-situ infrared spectroscopy analyses indicated NH3 adsorption on the MPTS-1.0 was mainly due to hydrogen bonding interaction and proton transfer to form Si-OH…NH3 and -SO3-NH4+, respectively. NH3 molecules bound firmly to acidic sites on the xerogel surface, which reduced re-release risk. This work may provide a feasible way to develop promising adsorbents for the removal of gaseous ammonia from air.

Polyurethane grouting materials with different compositions for the treatment of mud pumping in ballastless track subgrade beds: properties and application effect

Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines, reduce the smoothness of the railway lines, and seriously affect the comfort and safety of the trains. Due to their good mechanical properties, two-component polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping. To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping, we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios, to determine an optimal composition ratio of the raw materials. Then, we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio. The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area, coordinating the dynamic response between the track structure and the subgrade bed. Thus, the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.

Preventing algae adhesion using lubricant-modified polydimethylsiloxane/polythiourethane nanocomposite

To meet the need for an environmentally friendly fouling-release coating with high mechanical strength and good adhesion to substrates, a four-component nanocomposite was developed by a simple and industrially applicable blending approach. The nanocomposite consists of mechanically stable matrix polythiourethane (PTU), 1 wt% low surface free energy and rubber-like polydimethylsiloxane (PDMS), 1 wt% lubricant silicone oil, and 1 wt% tetrapodal shaped micro-nano ZnO (t-ZnO) filler particles, hereafter named PPZO. The rubber-like PDMS formed microdomains at the PTU/air interface, while silicone oil was distributed between the PDMS microdomains. The tensile strength of PPZO nanocomposite was approximately 63 MPa, two to four hundred times higher than the tensile strength of previously reported oil-modified coatings. The adhesion strength of PPZO to the substrate was 30 times higher than that of pure PDMS. After a five-month dynamic field test, the PPZO surface revealed much less biofouling than the references (AlMg3 and PTU), confirming its long-term biofouling control property. The attached algae on PPZO could easily and completely be removed by gentle brush cleaning. The good biofouling control property of PPZO can be attributed to the increased water repellency (signified by the increased water contact angle) and the surface slippage by silicone oil incorporation.

Carrier-Aided Dual-Frequency Vectorized Tracking Architecture for NavIC Signals

A new carrier-aided dual-frequency vectorized tracking (CA-DFVT) architecture for the Navigation with Indian Constellation (NavIC) is presented. CA-DFVT tracks both NavIC L5 (1176.45 MHz) and S-band (2492.028 MHz) signals concurrently. It uses the precise carrier phase measurements from the S-band signal and the unambiguous code phase measurements from the L5 signal to form a new measurement model for the extended Kalman filter (EKF) to estimate the position, velocity, and time (PVT) solutions. The new measurement model takes advantage of the benefits of the higher frequency S-band signal, i.e., less ionospheric delay and carrier phase noise, as well as the L5 signal’s inherent noise mitigation capabilities. Compared to the single-frequency approach, the dual-frequency approach in CA-DFVT eliminates the ionospheric effect and minimizes other errors, resulting in better navigation solutions. The proposed CA-DFVT enhances the reliability and robustness of NavIC signal tracking and position estimation in interference and high dynamics environments. We used static and dynamic field tests to validate the performance and robustness of the proposed CA-DFVT receiver architecture. In comparison to single-frequency (L5/S-band) vector tracking, the CA-DFVT receiver demonstrated consistent signal tracking and position estimation with higher position accuracy. In the static case, the mean horizontal position accuracy of CA-DFVT improves by approximately 2–4 and 9–14 m compared to L5-only VT and S-only VT, respectively, while, in the dynamic case, it improves by approximately 2–5 and 25–42 m, respectively.

Experiment-based estimation of the settlement potential due to dynamic loads from heavy vehicle traffic on the A 44n motorway built on the dump of the Garzweiler opencast mine

The A44 motorway was rebuilt on the dump of the Garzweiler opencast mine over a length of 7 km. The maximum thickness of the dump beneath the motorway is 185 m. Mostly sands showing a loose relative density were dumped. This leads to time-delayed settlements of the dump. In order to reduce these settlements of the dumped subsoil, which could jeopardise the serviceability limit state of the motorway, a top layer consisting of gravel and sand, with a minimum thickness of 10 m, was dumped using opencast mining equipment. This layer was compacted in the upper part using earth-moving machinery. To what extent vibrations from traffic loads can lead to grain rearrangements and thus settlements of the freshly dumped and compacted subgrade is the question of the investigation presented herein. Based on results of a customized exploration of the subsoil and dynamic field tests, in which loaded trucks drove over a measuring cross-section, it could be demonstrated that shear strain amplitudes induced by road traffic loads in the underlying compacted and loose granular soils do not exceed the strain threshold required for the accumulation of plastic deformations. Therefore, admissible settlements should not be exceeded even at very high numbers of traffic load cycles.

ANALISIS DAYA DUKUNG DAN PENURUNAN TIANG PANCANG MENGGUNAKAN DATA PDA TEST DAN PROGRAM PLAXIS PADA PEMBANGUNAN GEDUNG LABORATORIUM DAN KULIAH TERPADU UNIVERSITAS BORNEO TARAKAN

The foundation is the structure of the lower part of a building that is directly related to the ground or part of the building that is located below the ground surface which has the function of bearing the load of other parts of the building above it. There are various kinds of dynamic bearing capacity of the pile foundation, one of which is used with dynamic field test results, namely the PDA Test. The purpose of this research is to determine the carrying capacity of piles using PDA Test data then the results of the analysis will be compared with the results of calculations with Plaxis 2D V.8. The results of the calculation of the bearing capacity of the pile using PDA Test data obtained the largest value, namely 103 tons and the results of the carrying capacity using the Bagemann method obtained the value of 149.51 tons. The calculation of the pile settlement in the CAPWAP data is 12.97 mm at the P 113 pile and the calculation result of the maximum settlement of the pile in the Plaxis calculation is 3.50 mm the estimated single pile settlement meets the safe/permitted requirements.

Preserved arachnoid membrane acts as a predictor of postoperative visual improvement in clinoidal meningioma

ObjectivesImprovement of patient visual outcome is very important in the treatment of clinoidal meningioma (CLM). The purpose of this study is to determine the association between arachnoid preservation and visual outcome. PatientsFifteen patients with CLMs that caused visual impairment underwent surgery in our hospital. The patients included 4 men and 11 women, and the mean age was 53.3 years. MethodsThe clinical findings of these patients were retrospectively reviewed. We divided the patients into two groups based on the presence or absence of the arachnoid membrane. Group 1 comprised cases in which arachnoid preservation was intraoperatively confirmed. Group 2 comprised cases in which the arachnoid membrane was not preserved. The Landolt C chart was used to evaluate visual acuity, and dynamic visual field tests using Goldmann perimetry were used to evaluate the visual field. Results were compared before and after surgery. ResultsThe visual acuity of the ipsilateral eye was significantly improved in Group 1 (p = 0.038). There were no other significant differences between the two groups in terms of tumor volume, patient age, and symptom duration. ConclusionsPatients in which arachnoid preservation could be intraoperatively confirmed had good improvement in visual acuity. Further research with an increased number of cases is needed to confirm these findings.