Maximum Acceleration Research Articles

Agreement and Sensitivity of the Acceleration–Velocity Profile Derived via Local Positioning System

Sprint performance is commonly assessed via discrete sprint tests and analyzed through kinematic estimates modeled using a mono-exponential equation, including estimated maximal sprinting speed (MSS), relative acceleration (TAU), maximum acceleration (MAC), and relative propulsive maximal power (PMAX). The acceleration–velocity profile (AVP) provides a simple summary of short sprint performance using two parameters: MSS and MAC, which are useful for simplifying descriptions of sprint performance, comparison between athletes and groups of athletes, and estimating changes in performance over time or due to training intervention. However, discrete testing poses logistical challenges and defines an athlete’s AVP exclusively from the performance achieved in an isolated testing environment. Recently, an in situ AVP (velocity–acceleration method) was proposed to estimate kinematic parameters from velocity and acceleration data obtained via global or local positioning systems (GPS/LPS) over multiple training sessions, plausibly improving the time efficiency of sprint monitoring and increasing the sample size that defines the athlete’s AVP. However, the validity and sensitivity of estimates derived from the velocity–acceleration method in relation to changes in criterion scores remain elusive. To assess the concurrent validity and sensitivity of kinematic measures from the velocity–acceleration method, 31 elite youth basketball athletes (23 males and 8 females) completed two maximal effort 30 m sprint trials. Performance was simultaneously measured by a laser gun and an LPS (Kinexon), with kinematic parameters estimated using the time–velocity and velocity–acceleration methods. Agreement (%Bias) between laser gun and LPS-derived estimates was within the practically significant magnitude (±5%), while confidence intervals for the percentage mean absolute difference (%MAD) overlapped practical significance for TAU, MAC, and PMAX using the velocity–acceleration method. Only the MSS parameter showed a sensitivity (%MDC95) within practical significance (<5%), with all other parameters showing unsatisfactory sensitivity (>10%) for both the time–velocity and velocity–acceleration methods. Thus, sports practitioners may be confident in the concurrent validity and sensitivity of MSS estimates derived in situ using the velocity–acceleration method, while caution should be applied when using this method to infer an athlete’s maximal acceleration capabilities.

Optimization-Based Vibration Control Analysis of Dampers in High-Rise Building

Tuned mass dampers (TMDs) are a useful control of vibrations for tall buildings and can be considered equal to burdens such as breezes and earthquakes. The better limits for TMD are to reduce the earthquake vibrations of tall buildings including soil–structure interaction (SSI) influences. This study proposes the multi-objective Black Widow Optimization (BWO) with Elman neural network (ENN) computation that is brought on to find the optimal limits of TMD. Considering that this proposed model analyzed the mass, stiffness, and damping ratio of TMD to get the maximum accelerations and displacement of 40 story building model, from the execution results, starting from this proposed BWO–Elman model to the expected methodology, the most outrageous TMD limits are better, likewise, the reduction of acceleration and displacement are 25% and 19.86% in the proposed study. This study assists the researchers with a better understanding of earthquake vibration and leads the fashioners to achieve superior TMD for tall designs. The impact of vibration control on the displacements and accelerations of both controlled and uncontrolled buildings is investigated in this work. It uses a MATLAB software technique to analyze their modal replies, moreover, this proposed optimal TMD model is compared with conventional techniques by acceleration and stiffness parameters.

Seismic assessment of SSSI effects between adjacent Cross-Laminated Timber (CLT) buildings

Urban building designs have been performed considering the behaviour of individual structures in isolation, neglecting potential seismic interactions with neighbouring buildings. In densely populated metropolitan areas, the Structure–Soil–Structure Interaction (SSSI) becomes a significant factor, capable of either amplifying or reducing the seismic response of buildings. This suggests that there is an unquantified seismic risk in densely packed urban areas, which will need to be estimated to obtain designs for more resilient infrastructure. Despite the increasing popularity of CLT as a structurally competitive material, limited attention has been given to investigating dynamic interactions between timber structures. The reduced weight of CLT structures compared to traditional materials necessitates a focused examination of the effects imposed by nearby buildings under varying soil conditions, challenging the fixed-base assumptions commonly applied in seismic analyses. This study investigates the impact of SSSI between pairs of cross-laminated timber (CLT) buildings. Three distinct building heights are considered, exploring differences in storey ratios, under five different ground motions to evaluate seismic performance comprehensively. Sixty detailed high-order three-dimensional models, treating soil and buildings as unified systems, are developed as numerical dynamic simulations. Results reveal that SSSI can significantly influence the displacement and acceleration demands of buildings, with a more pronounced effect observed in loose soil conditions. Particularly, the presence of adjacent higher buildings leads to an increase in the seismic response of the smaller structure, showing amplification effects in peak values but maintaining similar dynamic behaviour. There has been observed a clear trend of increase in the roof displacements of the smaller structure when the storey ratio of neighbouring structures increases; however, the trend of behaviour is not clear in the maximum accelerations. The study underscores the importance of understanding how nearby buildings, particularly those with more storeys, can impact the seismic response on CLT structures.

Spurious Accelerations in Finite Element Analysis of Geotechnical Problems: Cause and Remedy

Present study investigates the response of the two distinct geotechnical problems under earthquake loading. These two problems are: 1) nailed soil slope and 2) 1-D site response analysis. The aim of the study is to understand the cause of spurious accelerations and suggest a remedy. Two distinct interface conditions were considered in modelling the nailed soil slope. In first, the soil nail interface was considered to be perfectly bonded. In second case, the sliding at the interface was allowed. The analysis resulted into the physically acceptable deformations. However, the dumbbell shaped spurious acceleration pattern was observed in perfect bonding case. Further, the maximum acceleration was found to span from 4 g to 13 g. Such extremely high accelerations are unphysical and hence, unacceptable. In case of 1-D site response analysis, misleading acceleration spike of magnitude twice that of true acceleration was noted. The introduction of the numerical damping successfully removed the spurious accelerations and resulted in physically acceptable response for both problems.

Assessing the Effect of Head and Neck Orientation on Head Injury Parameters in Taekwondo

Background: Brain injuries may be caused by the linear and rotational acceleration of the head and neck; in fact, head and neck orientation are one of the factors determining the type and severity of brain injury when the impact delivered to head is a less important consideration. This investigation has analyzed the effect of head and neck orientation on linear and rotational acceleration in Taekwondo. Methods: The ADAMS software model has been used to determine the linear and rotational acceleration in the taekwondo roundhouse kick in various orientations. Results: The results revealed that the maximum linear and rotational acceleration was related to neck 0° were 99g, and 4576 , respectively. The head and neck orientation did not affect the magnitude of the linear and rotational acceleration in the sagittal plane. However, as the angle of the head and neck orientation increased in the frontal plane, the magnitude of the linear and rotational acceleration decreased. Conclusion: In general, the results indicate that only rotational acceleration was the cause of brain injury in taekwondo. Increasing the angle of orientation of the head and neck in frontal plane would lead to a reduction in intensity.

A database of shake-table tests conducted on unreinforced masonry buildings

Experimental results obtained from shake-table tests on complete unreinforced masonry buildings (URM) play a crucial role in enhancing modeling techniques and reducing uncertainties in seismic assessments for this type of building. This paper presents an open-access database comprising 69 shake-table tests on URM buildings with a scale equal to or larger than 1:4 that have been documented in the literature. The database summarizes important geometric parameters, structural characteristics, and experimental results, including maximum shake-table accelerations, story drifts, and evolution of dynamic properties, as well as qualitative information such as observed failure modes and damage progression throughout the experiments. This database is meant to serve the research community as a resource for planning future experimental campaigns, benchmarking numerical models, validating analysis methods, and improving predictive capabilities. As an example application, we generate vulnerability functions (fragility curves) from the experimental data. Our findings reveal that buildings tested in experiments are less vulnerable compared to real buildings, particularly when severe damage is observed and when the ground motion intensity is low to moderate. The ultimate objective is to facilitate the exchange of experimental data and boost collaborative approaches in the seismic assessment of URM buildings.

Experimental Investigation of the Heaving Motion Effect on Critical Heat Flux Phenomena and Wall Temperature Fluctuation Using R134a for Floating Nuclear Applications

This study experimentally investigated the flow boiling critical heat flux (CHF) under heaving conditions pertinent to floating nuclear power plants (FNPPs). Experiments were conducted using R134a to simulate the operational pressure of pressurized water reactors, extending the CHF database to a pressure range of 5 to 18 MPa. The tested heaving motion reached up to 0.6 g of maximum acceleration, with a period that varied from 3 to 5.3 s. A parametric trend involving mass flux, critical quality, and motion conditions was analyzed through extensive tests encompassing static and heaving conditions. The results showed that CHF reduction was observed due to the effect of heaving acceleration, even in the absence of oscillations in other thermal-hydraulic factors. The CHF reduction was up to 9% in the present experimental conditions. The heaving motion effect was prominent under two specific thermal-hydraulic conditions: when the critical quality was close to zero and when it exceeded the value of 0.6. Furthermore, an examination of wall temperature responses suggested that a longer period of heaving motion can lead to an earlier occurrence of CHF. This fundamental effort was conducted to enhance the understanding of the CHF mechanism under motion conditions, with the aim of contributing to the safe and efficient design of FNPPs.

Safety padding performances to protect from severe head injuries during alpine skiing

To protect skiers from the collisions with obstacles (CWOs), ski areas place padding on these obstacles. Padding behavior was previously experimentally investigated for few specific head impact conditions. The goal of this study is to numerically evaluate padding ability to reduce head injury risks in multiple scenarios of CWOs. A multibody model of a skier colliding with an obstacle was associated with a padding model, calibrated based on experimental tests. Different obstacle protections (unprotected, 15-, 20-, 30-cm thick padding), skier speeds, obstacle shapes and distances were investigated to model 3692 scenarios of CWOs. Head injury risks were evaluated based on HIC15 and maximal linear accelerations (Amax). Kruskal-Wallis tests were used to investigate the injury risks regarding the initial conditions, impact conditions and obstacle protection. These simulations resulted in high head impact speeds (30.4 ± 14.2 km/h). The padding modeled significantly reduced Amax (368 ± 275 g unprotected VS 215 ± 240 g with 15-cm thick padding) and severe injury risks ( p < 0.001). For low head impact speeds (<20 km/h), all pads were able to protect from severe injuries, whereas for moderate impact speeds (<40 km/h), the 30-cm thick padding offered better protection from severe injuries. However, even thick padding could not protect the skier model from high-speed impacts (>40 km/h). This study evaluated padding performances in various accident conditions and brought quantitative information for field evolutions regarding padding protection. These results constitute useful information to improve the padding standard and to design more efficient padding.

The role of liquefaction in the evolution of shallow submarine canyon heads from a geotechnical perspective: A case study of the Garrucha Canyon (SE Mediterranean)

This work aims to establish the role of liquefaction in a shallow submarine environment defined by a canyon head reaching the coast. The study area is the Garrucha submarine canyon head, which is located in the western Mediterranean Sea.The potential of liquefaction is approached empirically by two methods in parallel, undrained cyclic direct simple shear (UCDSS) test and piezocone penetration test (CPTu) analyses. For both approaches, considering the regional earthquake records, a cyclic load linked to Mw ≤ 6.5 earthquake events or a maximum ground surface acceleration amax of 0.25 g is considered.The sediment samples analysed are nonplastic sands with low silt/clay contents and can be defined as liquefiable. Geotechnical analysis reveals a high probability of triggering liquefaction in this kind of sediment at depths greater than 3 m below the seafloor. CPTu records are used to assess and improve the liquefaction model for the study area by defining 3 different stratigraphic configurations or liquefiable conditions: uniformly liquefiable, interbedded liquifiable and nonliquefiable.This work highlights the importance of liquefaction—a process normally underestimated in submarine environments—in the downslope transport of sediment from the upper part of a canyon and, more generally, in canyon head evolution with different potential morphosedimentary consequences.

Clot waveform analysis to differentiate mild, moderate, and severe hemophilia A

Background Clot waveform analysis can be used to evaluate clot formation profiles. This waveform can be obtained from activated partial thromboplastin time (APTT) assays without additional reagents and shows different patterns in hemophilia patients with coagulation factor VIII (F VIII) deficiency or abnormality. Objective To determine the clot wave pattern and its process in clot formation phases (pre-coagulation, coagulation, and post-coagulation) in normal and hemophilia A subjects, analyze for possible correlations between clot wave parameters and F VIII activity, and obtain the pattern of coagulation curves in hemophilia subjects as a step to assess clot waveform analysis as a possible screening tool for hemophilia. Methods In this cross-sectional study, we performed clot wave analysis in 145 adult and pediatric subjects with hemophilia to obtain the clot wave pattern in this condition. Clot wave analysis was also done in 160 subjects with normal hemostasis to obtain reference clot wave parameters. Results In this study, the starting point of coagulation phase in normal subjects was between 30-40 seconds, with a shorter pre-coagulation phase and steeper slope. Hemophilia patients had a longer pre-coagulation phase and flatter slope, especially in severe hemophilia A patients, who had longer and more variable coagulation starting points (P<0.001). The absolute values of maximum coagulation velocity (Min1), maximum coagulation acceleration (Min2), and maximum coagulation deceleration (Max2) of hemophilia A patients were also lower than those of normal hemostasis patients, with lower absolute value seen in severe than in mild-moderate hemophilia A patients. A moderate correlation was found between Min1, Min2, and Max2 with F VIII activity (P<0.001). Conclusion Clot wave analysis may be considered as a method for screening hemophilia patients to distinguish mild-moderate and severe hemophilia A patients in health facilities that lack the ability to perform F VIII assays.

A sensitive wavelength-enhanced reconstruction algorithm for track quality assessment based on measured data and vehicle dynamics

High-speed railways are extensively utilized worldwide. However, with prolonged operation, track irregularities increasingly pose significant challenges, adversely affecting the safety and stability of train operations. This paper proposes a sensitive wavelength-enhanced reconstruction algorithm based on the cmplete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) method to address this issue. This method evaluates the influence of reconstructed track irregularities on vehicle dynamic response, considering sensitive wavelengths and amplification factors. The algorithm effectively enhances these sensitive wavelengths while maintaining the integrity of the input signal, utilizing measured track irregularities. After applying the algorithm, the maximum vertical body acceleration rises by 206.09%. The study validates a coupled train model and analyzes the mapping relationship between single-wave irregularities and vertical body acceleration. Compared to random irregularities, the maximum vertical acceleration can amplify up to 122.80% under various operating conditions. The periodic sensitive wavelengths of track irregularities significantly impact the train’s dynamic response.

Ditching characteristics of a seaplane under various wave conditions and effects of biomimetic floats

This paper presents a numerical investigation into the hydrodynamic loads and motions experienced by two seaplane models during ditching in calm water and regular waves. The original bare model is susceptible to jet flows and wave overwash at the nose, which can adversely impact the aircraft's ditching performance. To address these issues, we introduced two biomimetic floats symmetrically to the original model and assessed their influence on the ditching dynamics. A comparative analysis was conducted on the accelerations, impact loads, and the coupled heave and pitch motions of both the original and the redesigned model equipped with floats during ditching in both calm waters and regular waves. For the wave ditching scenario, a detailed investigation of the slamming phase was first carried out, involving impacts at the wave's zero-crossing, crest, and trough. The cases with a variety of wave heights, wave lengths, and wave headings were evaluated. A particular focus was placed on understanding how the biomimetic floats affect the seaplane's performance during ditching in both calm and wavy conditions. The analysis of maximum accelerations and pitch angles during wave ditching revealed that slamming at the wave trough presents the most significant hazards. Additionally, the phenomena of gliding and wave overwash were identified as substantial risks under wave conditions. The results suggested that the biomimetic floats can effectively mitigate the maximum horizontal acceleration and pitch angle of the original model, enhancing the safety of ditching operations in both calm water and waves.

Design and test of a contactless damper for HTS maglev systems via electromagnetic shunt dampers

High-temperature superconducting (HTS) maglev system is promising to become the future high-speed transport due to its numerous advantages. However, the low-damping dynamic characteristics of superconductors make the system vulnerable to external disturbances, which present a significant challenge to its implementation. To enhance the vibration attenuation effect of the HTS maglev system, a non-contact damper that employs electromagnetic shunt damping (EMSD) and negative resistance is incorporated into the HTS maglev system. This study elucidates the principles of EMSD and negative resistance, and establishes the governing equations to describe the behavior of the HTS maglev model equipped with EMSD. Subsequently, the EMSD coupling coefficients are analysed via the finite element method (FEM) under varying conditions. Finally, a dedicated vibration test rig is designed and fabricated to validate the effectiveness of the proposed damper. The results demonstrate that the proposed damper, in combination with negative resistance, is capable of effectively suppressing vibration in HTS maglev systems. The maximum acceleration of the test model can be reduced by 86% compared with the original system without the damper. This work may provide valuable guidance for future practical implementations.

Chaotic behaviour in the dynamical response of coaxial magnetic gears during acceleration

Slippage during acceleration has been a significant issue in coaxial magnetic and has been thoroughly investigated in the recent years. Depending on the applied outer load it is important to know the maximum acceleration that can be induced so that the system will not diverge. In the present work a non-dimensional analysis has been conducted in order to develop a stability criterion for the maximum acceleration that can be applied to the system as a function of the outer load. A closed-form relation for the period of the oscillations of the system that will be caused by the acceleration, has also been derived. Furthermore, the case of acceleration with ripple has been investigated. It was demonstrated that during acceleration with ripple under constant applied outer load, the system showcases a chaotic behaviour similar to the driven pendulum. In particular, a thorough analysis on the frequency of the ripple has been conducted. It was observed that when the ripple frequency was slightly lower than the frequency of the oscillation under steady acceleration, the system could potentially diverge even if the acceleration of the system was lower than the critical value. With the present work, a detailed non-dimensional model has been derived that could be a useful tool for determining the stability of coaxial magnetic gears without the requirement of numerical solution of the governing equations. In addition, some interesting observations are made regarding the chaotic behaviour of the dynamical response of coaxial magnetic gears during acceleration with ripple.

Visual Navigation of Caged Chicken Coop Inspection Robot Based on Road Features.

The speed and accuracy of navigation road extraction and driving stability affect the inspection accuracy of cage chicken coop inspection robots. In this paper, a new grayscale factor (4B-3R-2G) was proposed to achieve fast and accurate road extraction, and a navigation line fitting algorithm based on the road boundary features was proposed to improve the stability of the algorithm. The proposed grayscale factor achieved 92.918% segmentation accuracy, and the speed was six times faster than the deep learning model. The experimental results showed that at the speed of 0.348 m/s, the maximum deviation of the visual navigation was 4 cm, the average deviation was 1.561 cm, the maximum acceleration was 1.122 m/s2, and the average acceleration was 0.292 m/s2, with the detection number and accuracy increased by 21.125% and 1.228%, respectively. Compared with inertial navigation, visual navigation can significantly improve the navigation accuracy and stability of the inspection robot and lead to better inspection effects. The visual navigation system proposed in this paper has better driving stability, higher inspection efficiency, better inspection effect, and lower operating costs, which is of great significance to promote the automation process of large-scale cage chicken breeding and realize rapid and accurate monitoring.

Analysis of Polynomial Interpolation Characteristics Based on 6DOF Manipulator Trajectory Planning

Aiming at the problems of choosing and using polynomials of different times and mixed polynomials in the process of manipulator trajectory planning, such as difficulty, wide range of light and low accuracy, in this paper, the application of different polynomials in manipulator trajectory planning is systematically analyzed by using MATLAB Robot Toolbox simulation platform and Polynomial interpolation algorithm. Using a 6-dof robotic arm Puma560 as a simulation object, the effects of three-, five-, and seven-Polynomial interpolation on joint position and pose in joint space trajectory planning were analyzed, a preliminary understanding of the application of different polynomials, and secondly, the more complex application of the fifth and seventh degree polynomials in Descartes space for the trajectory planning of the manipulator, the influence of trajectory planning with different degree polynomials on the position and pose of manipulator joint is clarified. The results show that the higher the number of polynomials, the smoother the transition of the joint at the critical path points, but the greater the maximum angular velocity and angular acceleration of the joint, the Polynomial interpolation of joint space and Descartes space trajectory planning are 14% and 23% lower than the average of absolute maximum angular velocity and absolute maximum angular acceleration of the Polynomial interpolation, respectively. Based on the analysis of the research results, this paper presents the applicable conditions and applications of Polynomial interpolation method in trajectory planning, and further summarizes the application conditions and methods of mixed polynomials.

Impact of Stimulation Duration in taVNS-Exploring Multiple Physiological and Cognitive Outcomes.

Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique that modulates the noradrenergic activity of the locus coeruleus (LC). Yet, there is still uncertainty about the most effective stimulation and reliable outcome parameters. In a double blind, sham-controlled study including a sample of healthy young individuals (N = 29), we compared a shorter (3.4 s) and a longer (30 s) stimulation duration and investigated the effects of taVNS (real vs. sham) on saliva samples (alpha amylase and cortisol concentration), pupil (pupillary light reflex and pupil size at rest) and EEG data (alpha and theta activity at rest, ERPs for No-Go signals), and cognitive tasks (Go/No-Go and Stop Signal Tasks). Salivary alpha amylase concentration was significantly increased in the real as compared to sham stimulation for the 30 s stimulation condition. In the 3.4 s stimulation condition, we found prolonged reaction times and increased error rates in the Go/No-Go task and increased maximum acceleration in the pupillary light reflex. For the other outcomes, no significant differences were found. Our results show that prolonged stimulation increases salivary alpha-amylase, which was expected from the functional properties of the LC. The finding of longer response times to short taVNS stimulation was not expected and cannot be explained by an increase in LC activity. We also discuss the difficulties in assessing pupil size as an expression of taVNS-mediated LC functional changes.

Research on the Design of Multi-Rope Friction Hoisting System of Vertical Shaft Gravity Energy Storage System

Renewable energy generation methods such as wind power and photovoltaic power have problems of randomness, intermittency, and volatility. Gravity energy storage technology can realize the stable and controllable conversion of gravity potential energy and electric energy by lifting and lowering heavy loads. The hoisting system is an important component of a gravity energy storage system, and its lifting capacity and speed seriously restrict its energy storage capacity, energy conversion efficiency, and operational safety and reliability. In this paper, a design method for a multi-rope friction hoisting system of a vertical shaft gravity energy storage system is proposed. The parameter design and calculation of the hoisting rope, balance rope, and friction wheel of the friction hoisting system under typical conditions were carried out. The static and dynamic anti-slip capabilities of the friction hoisting system under the typical condition were explored. The results show that the maximum acceleration and deceleration speed of the compacted strand wire rope scheme is the largest, and the lifting and lowering time is the shortest. The maximum acceleration and deceleration speed of the triangular strand wire rope scheme is the lowest, and the lifting and lowering time is the longest. The dynamic tension of the hoisting rope at the heavy-load end is positively correlated with the acceleration, and the maximum value occurs in the accelerated lifting stage and decelerated lowering stage of the heavy load. The static anti-slip safety factor between the hoisting rope and the friction lining and the specific pressure between the hoisting rope and the friction lining comply with the requirements of China’s Safety Regulations for Coal Mines. The dynamic anti-slip safety factor of the hoisting system under different rope selection schemes is greater than the minimum value of 1.25 stipulated in the Safety Regulations for Metal and Nonmetal Mines. The research results are of great significance for the safety, reliability, and stable and efficient energy storage of a gravity energy storage system.

Enhancing highway Loop Safety Level through proactive risk-based assessment of geometric configuration using lateral acceleration

Objective Loop ramps are complex due to their combination of horizontal curves and vertical alignments. Analyzing driving behavior and measuring safety levels can provide insights for designers, helping to improve the performance and alignment of design assumptions with actual driving behavior on loops. Therefore, the primary objective of this research is to explore the safety, performance and geometric configuration of the main body and general shape of free-flow loop ramps in the free-following mode. Methods The study uses data from a UAV to investigate vehicle demand behavior. Maximum lateral acceleration (a y,i) in loops is used as a Surrogate Safety Measure (SSM), along with a new parameter, the a/b ratio, to determine the general shape of loop bodies. The study presents the Loop Safety Level (LSL), an approach for proactive risk analysis and ranking that relies on threshold lateral acceleration (a t), 85th percentile maximum lateral acceleration ( a y,max,85%), and crash analysis. Results A higher LSL value points to a more critical safety concern regarding the loop’s shape in relation to lateral acceleration caused by driving behaviors. Comparing crash statistics with lateral acceleration results enables the LSL to provide appropriate safety ratings and diagnose loop segment safety. A prediction model for maximum lateral acceleration, based on loop geometry, demonstrates a good fit (R2=0.88) between observed and predicted data. Conclusions The study enhances understanding of safety considerations in geometric configuration and general shape enhancement of loops during the design process.

Study on Ground Motion Amplification in Upper Arch Bridge Due to “W”-Type Deep Canyon Using Boundary-Integral and Peak Frequency Shift Methods

The study of the dynamic response characteristics of “W”-type deep canyon terrain to double-span concrete arch bridges under earthquake action holds great practical significance. In this research, a bridge in Sichuan Province is taken as the object of study. The boundary-integral equation method and peak frequency shift method are combined to apply an embedded linear time–history analysis algorithm to the finite element spatial dynamic calculation model of the entire bridge, resulting in an improved model. By comparing these two methods with model test results, the seismic response characteristics of the middle part of a “W” concrete arch bridge under different foundation depths and seismic intensities are examined. The boundary integral equation method was utilized to calculate ground motion response at any point on site, revealing a significant amplifying effect of increased seismic wave intensity on acceleration response at the top of the arch bridge. When input seismic wave intensity increased from 0.1 g to 0.3 g, maximum acceleration at buried depths of 3 m and 8 m in the middle of the arch bridge foundation increased by 102.63% and 79.16%, respectively, indicating that shallow buried depth structures are more sensitive to seismic wave intensity. Furthermore, using peak frequency shift rules for analyzing seismic wave propagation characteristics in “W”-type deep canyon topography confirms the sensitivity of shallow buried depth structures to seismic wave intensity and reveals the mechanism through which topography influences seismic wave propagation. This study provides a helpful method for understanding the propagation law and energy distribution characteristics of seismic waves in complex terrain. It was observed that the displacement at the top of the arch bridge increased significantly with an increase in seismic intensity. When subjected to 0.1 g, 0.2 g, and 0.3 g EI-Centro seismic waves, the maximum displacement at the top of the arch bridge model with a foundation buried depth of 3 m was 8 mm, 32 mm, and 142 mm, respectively. For arch bridge models with an 8-m foundation buried depth, these displacements were measured at 6.2 mm, 21 mm, and 68 mm, respectively. The results from model tests verified that increasing the depth of foundation burial effectively reduces the displacement at the top of the structure. Furthermore, by combining a boundary-integral equation method and peak-frequency shift method, this study accurately predicted significant influences on W-shaped double deep canyon topography from seismic response, and successfully captured stress concentration and seismic wave amplification/focusing effects on arch foot structures. The calculated results from both methods align well with model test data which confirm their effectiveness and complementarity when analyzing seismic responses under complex terrain conditions for bridge structures.