Impact Coefficient Analysis of Curved Box Girder Bridge Based on Vehicle-Bridge Coupling

In the current vehicle-bridge dynamics research studies, displacement impact coefficients are often used to replace the moment and shear force impact coefficients, and the vehicle model is also simplified as a moving-load model without considering the contribution of vehicle stiffness and damping to the system in some concerned research studies, which cannot really reflect the mechanical behavior of the structures under vehicle dynamic loads. This paper presents a vehicle-bridge coupling model for the prediction of dynamic responses and impact coefficient of the long-span curved bending beam bridge. The element stiffness matrix and mass matrix of a curved box girder bridge with 9 freedom degrees are directly deduced based on the principle of virtual work and dynamic finite element theory. The vibration equations of vehicle-bridge coupling are established by introducing vehicle mode with 7 freedom degrees. The Newmark-β method is adopted to solve vibration response of the system under vehicle dynamic loads, and the influences of flatness of bridge surface, vehicle speed, load weight, and primary beam stiffness on the impact coefficient are comprehensively discussed. The results indicate that the impact coefficient presents a nonlinear increment as the flatness of bridge surface changes from good to terrible. The vehicle-bridge coupling system resonates when the vehicle speeds reach 60 km/h and 100 km/h. The moment design value will maximally increase by 2.89%, and the shear force design value will maximally decrease by 34.9% when replacing moment and shear force impact coefficients with the displacement impact coefficient for the section internal force design. The load weight has a little influence on the impact coefficient; the displacement and moment impact coefficients are decreased with an increase in primary beam stiffness, while the shear force impact coefficient is increased with an increase in primary beam stiffness. The theoretical results presented in this paper agree well with the ANSYS results.

Dynamic Changes in Groundwater Level under Climate Changes in the Gnangara Region, Western Australia

The groundwater-dependent ecosystem in the Gnangara region is confronted with great threats due to the decline in groundwater level since the 1970s. The aim of this study is to apply multiple trend analysis methods at 351 monitoring bores to detect the trends in groundwater level using spatial, temporal and Hydrograph Analysis: Rainfall and Time Trend models, which were applied to evaluate the impacts of rainfall on the groundwater level in the Gnangara region, Western Australia. In the period of 1977–2017, the groundwater level decreased from the Gnangara’s edge to the central-north area, with a maximum trend magnitude of −0.28 m/year. The groundwater level in 1998–2017 exhibited an increasing trend in December–March and a decreasing trend in April–November with the exception of September when compared to 1978–1997. The rainfall + time model based on the cumulative annual residual rainfall technique with a one-month lag during 1990–2017 was determined as the best model. Rainfall had great impacts on the groundwater level in central Gnangara, with the highest impact coefficient being 0.00473, and the impacts reduced gradually from the central area to the boundary region. Other factors such as pine plantation, the topography and landforms, the Tamala Limestone formation, and aquifer groundwater abstraction also had important influences on the groundwater level.

The Issue of Operating Security Systems in Terms of the Impact of Electromagnetic Interference Generated Unintentionally

This article discusses issues regarding electromagnetic interference generated unintentionally by transport telematics systems and electronic security systems (ESS) located within a railway area. These systems should operate correctly, since they ensure the safety of both vehicles and passengers. The electronic devices they use are exposed to electromagnetic interference that may lead to incorrect ESS functioning. In order to determine the impact of electromagnetic interference on ESS, the authors measured unintentional low-frequency electromagnetic field generated by MV—15 and 30 kV—power lines. This enabled determining the areas with maximum values of electromagnetic interference. The next stage of the research was to develop an ESS operating process model that takes into account the impact of unintentionally generated electromagnetic interference on the operating process. Introducing the electromagnetic interference impact coefficient enables a rational selection of solutions aimed at protecting against electromagnetic interference through the application of technical and organizational measures.

Numerical Investigation on the Dynamic Performance of Steel–Concrete Composite Continuous Rigid Bridges Subjected to Moving Vehicles

Assembly construction is the main feature of industrialized bridges, and π-shaped section steel–concrete composites that are continuously rigid have been widely used in engineering fields in recent years; however, their dynamic responses and corresponding impact coefficients in positive and negative moment regions need to be further studied. First, considering the interface slip model, we established a finite element model for the π-shaped continuous region section of the steel–concrete composite on the Sutai Expressway Tongfu No. 3 viaduct. Second, the bridge deck unevenness parameters were generated by preparing a MATLAB program with random calculations and were added to the bridge deck as the excitation load along with the vehicle load. Such parameters are defined on the basis of considering the vertical degrees of freedom of the four wheels and of one vehicle rigid body. Finally, we analyzed the displacement or stress impact coefficients as the dynamic response index of the bridge by adjusting the vehicle travel speeds, vehicle weights, interface slip stiffness values, and deck unevenness values. The results show that the change in vehicle travel speed and the change in vehicle load weight have some influence on the change in the dynamic effect of the combined beam, but this change is not significant. Moreover, the unevenness and interface slip strength changes have a large effect on the dynamic effect of the combination beam, which can significantly change the impact coefficient of the combination beam bridge. The worse the unevenness of the bridge deck is, the lower the grade of interface slip for the steel–concrete composite bridges and the higher the impact coefficient. We calculated the recommended impact coefficient values of the steel–concrete composite bridge based on the specifications for various countries, and they range from 1.16 to 1.4; such values are similar to the finite element calculation results.

In Search of Optimal Laser Settings for Lithotripsy by Numerical Response Surfaces of Ablation and Retropulsion

Even though ureteroscopic laser lithotripsy (URSL) has become the preferred treatment option for urolithiasis due to shorter operation time and a better stone-free rate, the optimum laser pulse settings for URSL with the shortest operative times remain unknown. In this chapter, two sets of design of experiments (DOE) were conducted with response surface methodology: 1) the quantitative responses of calculus ablation and retropulsion in terms of the pulse energy, pulse width, and the number of pulses of a prototype Chromium (Cr3+), Thulium (Tm3+), Holmium (Ho3+) triple doped yttrium aluminum garnet (CTH:YAG) laser system. The ablation or retropulsion is inversely proportional to the pulse width, and the pulse width has a higher impact coefficient for the ablation than for the retropulsion. The quadratic fit of the response surface for the volume of ablation has a nonlinear relationship with the pulse width and number of pulses. 2) the laser setting optimization of laser lithotripsy of a commercially available CTH: YAG laser system. The experimental setup is based on a benchtop model first introduced by Sroka’s group. Comparing to frequency, the laser pulse energy or peak power has a higher impact coefficient to stone retropulsion as compared to stone ablation in CTH: YAG laser lithotripsy. The most efficient way to curtail stone retropulsion during laser lithotripsy is to lower the laser pulse peak power.

Analysis of Customization Strategy for E-Commerce Operation Based on Big Data

In order to improve the efficiency of customization and reduce the cost of customization under Big data environment, this paper uses cost-sharing contract, pricing mechanism, Hotelling model, and game theory tools and research methods, for C2B Electronic Commerce (e-commerce) mode of Supply Chain Pricing Strategy for in-depth discussion. This paper first gives the architecture of the customization service system based on big data. The paper studies the game equilibrium of supply chain members under four scenarios: centralized decision-making, decentralized decision-making, C2B-dominated decision-making, and traditional enterprise-dominated decision-making in a supply chain composed of a supplier and C2B e-commerce enterprises with horizontal price competition, and examines the cross-price. Important parameters such as impact coefficient, impact coefficient of effort degree of personalized customization, and so on have an impact on variables such as effort degree of personalized customization, retail price, and profit of supply chain members of C2B e-commerce enterprises. Research shows that with the increase of cross-price impact coefficient, C2B e-commerce will enhance its personalized customization efforts in different situations in order to pursue higher profits.

Dynamic load test and lateral load distribution of a modified rigid frame bridge

In order to evaluate the stress state and working performance of a rigid frame bridge after reconstruction and extension, load test and transverse load distribution were carried out. Static load test is the test of stress at each section of main beam under the action of partial load and medium load. Dynamic load test is used to test the inherent fundamental frequency, damping ratio and impact coefficient of the bridge through pulsation test and sports car test. The results show that the first order vibration of the bridge is mainly transverse vibration from the measured modal parameters, which is consistent with the characteristics of higher pier and greater flexibility. The vibration characteristics of the bridge structure are low frequency and small damping vibration, the value of which belongs to the normal range among similar bridge structures, the overall stiffness of the bridge structure is normal, and the measured impact coefficient during the test of sports car is less than the design impact coefficient, indicating that the dynamic stiffness of the bridge meets the design and specification requirements.

Research on the evaluation method of bearing capacity of existing Bridges based on dynamic load test

The author carried out dynamic load test research on a prestressed concrete rigid frame bridge. Under dynamic load, the ratios of the measured and theoretical frequencies of the first four vertical vibrations of the bridge were 1.081, 1.153 respectively. The corresponding measured damping ratios are 0.011, 0.010 respectively. The maximum dynamic coefficient of bridge sports car test is 1.049, and the corresponding dynamic strain increment coefficient is 0.059. The measured impact coefficient is between 0.012 and 0.049, which is basically equivalent to the design impact coefficient of 0.05.The test results show that the existing bridge works well under the test load, and the bearing capacity of the structure meets the requirements of the design load level.