Maximum Longitudinal Displacement Research Articles

Sliding connectors for cyclic construction of steel-UHPC composite truss arch bridges: design method and feasibility study

To break through the three major technical bottlenecks of traditional long-span arch bridges, which are excessive self-weight, high cost and difficult construction, a new steel-ultra high performance concrete (UHPC) composite truss arch bridge scheme and a matching cyclic construction method were proposed. The main arch can be divided into several times for closure from the inside out. Special transverse connection devices need to be installed between the arch ribs constructed with successive closures by step. The devices can not only ensure the stability of the arch ribs constructed subsequently, but also do not cause serious stress superposition on the already closed arch ribs. Therefore, sliding connectors for the cyclic construction of new arch bridges and the corresponding simplified modeling method were proposed in this paper. Subsequently, the working mechanism was analyzed, and the design method was proposed. Finally, the feasibility of sliding connectors and the correctness of the corresponding design method were verified by the experiment. The results indicate that it is necessary to install a transverse sleeve structure in the sliding connector, which plays a key role in transverse adjustment. The design of key dimensions in sliding connectors is controlled by the maximum vertical and longitudinal displacements of the inner arch. The outer arch could slide freely under the premise of ensuring stability, and the mechanical superposition response of the inner arch was relatively small. For the inner arch, the vertical displacement at the crown only increased by 10.94 %, and the maximum compressive stress in the UHPC arch ribs only increased by 16.3 %. The sliding connector also has the potential for further optimization to achieve smaller stress superposition.

Mitral annulus disjunction in consecutive patients undergoing cardiovascular magnetic resonance: Where is the boundary between normality and disease?

BackgroundThe presence of mitral annulus disjunction (MAD) has been considered a high-risk feature for sudden cardiac death based on selected study populations. We aimed to assess the prevalence of MAD in consecutive patients undergoing clinically-indicated Cardiac Magnetic Resonance (CMR), its association with ventricular arrhythmias, Mitral Valve Prolapse (MVP), and other CMR features. MethodsThis single-center retrospective study included consecutive patients referred to CMR at our Institution between June 2021 and November 2021. The MAD was defined as a ≥1mm displacement between the left atrial wall-mitral valve leaflet junction and the left ventricular wall during end-systole. The MAD extent was defined as the maximum longitudinal displacement. Associates of MAD were evaluated at uni- and multi-variariable regression analysis. A study endpoint including (aborted) sudden cardiac death, unexplained syncope, and sustained ventricular tachycardia was evaluated at 12-month follow-up. ResultsFour-hundred-forty-one patients (55±18 years, 61% males) were included, and 29 (7%) had MVP. The prevalence of MAD ≥1mm, 4mm, and 6mm were 214 (49%), 63 (14%), and 15 (3%), respectively. Patients with MVP showed a higher prevalence of MAD greater than 1mm (90% vs. 46%; p<0.001), 4mm (48% vs. 12%; p<0.001), and 6mm (10% vs. 3%; p=0.03), and a greater MAD extent (4.2mm, 3.0-5.7mm vs. 2.8mm, 1.9-4.0mm; p<0.001) than patients without MVP. The MVP was the only morpho-functional abnormality associated with MAD at multivariable analysis (p<0.001). A high burden of ventricular ectopic beats at baseline Holter-ECG was associated with MAD ≥4mm and MAD extent (p<0.05). The presence of MAD ≥1mm (0.9% vs. 1.8%; p=0.46), MAD ≥4mm (1.6% vs. 1.3%; p=0.87), or MVP (3.5% vs. 1.2%; p=0.32) were not associated with the study endpoint, whereas patients with MAD ≥6mm showed a trend towards a higher likelihood of the study endpoint (6.7% vs. 1.2%; p=0.07). ConclusionsA MAD of limited entity was common in consecutive patients undergoing CMR. Patients with MVP showed higher prevalence and greater extent of MAD. Extended MAD was rarer and showed association with ventricular arrhythmias at baseline. The mid-term prognosis of MAD seems benign, however prospective studies are warranted to search for potential “malignant MAD extents” to improve patients’ risk stratification.

Prediction of Static Characteristics of Hydrodynamic Air Foil Bearing Considering Contact and Friction Between Foils

Abstract The elastohydrodynamic model of hydrodynamic air foil bearing has been built to study the influence of rotor speed, the friction coefficient between bearing components, load and other parameters on the foil displacement of hydrodynamic air bearing under steady-state conditions. The static characteristics of hydrodynamic air foil bearing are predicted by using the numerical simulation method. The results show that the radial displacement of the foil is the smallest at both ends of the bearing and the largest at the middle of the bearing, while the top foil changes gently along the width of the bearing away from the maximum pressure. After increasing the rotating speed, the maximum fluid pressure improves and the action position shifts, and the increase of rotating speed has a significant impact on the maximum pressure. Improving the friction coefficient µ2 between the bump foil and the bearing sleeve has different effects on the displacement of the foil. When µ1 is 0.1, by promoting µ2, the transverse displacement of the top foil at the pressure peak increases by 20.9%, the longitudinal displacement is reduced by 8.9%, and the transverse displacement and the maximum longitudinal negative displacement of the bump foil are decreased by 53.2% and 31.7%, respectively. Furthermore, the longitudinal displacement of bump foil at the fixed end has been reduced by increasing the load, and the relative size of the friction coefficient between the components affects the size and direction of the foil displacement at the same load.

Effect of Ambient Temperature on Current Collection Quality in Pantograph–Catenary Interaction

This paper investigates the effect of the ambient temperature change on the dynamic interaction between pantograph and catenary (PAC). Thermal expansion/contraction of the components of the overhead contact system (OCS) is considered. Simulation results show that the thermal stress has a much greater influence on the longitudinal positioning of the contact wire than on the horizontal and vertical positioning. When ambient temperature reduces to [Formula: see text] from design temperature of [Formula: see text]C, the maximum longitudinal displacement of the positioner can reach as high as 301 mm, while the maximum horizontal and vertical displacement of the positioner is within 4[Formula: see text]mm. The change of ambient temperature results in the uneven tension distribution of the contact wire, especially near the central anchor. With the increase in temperature, the tension of contact wire decreases; vice versa, with the decrease in temperature, the tension of contact wire increases. For nine-span OCS, the tension change caused by ambient temperature change shall not exceed 2%. The variation of ambient temperature also leads to the deterioration of current collection quality. It is shown that a decreasing ambient temperature results in more significant changes in contact force, close to 5%. An increasing ambient temperature environment leads to a higher uplift of pantograph, close to 30%.

Experimental Study on the Axial Compression Performance of Glued Wood Hollow Cylinders Reinforced with BFRP

The present paper investigates the impact of basalt fiber reinforced polymer (BFRP) on the axial compression performance of glued wood hollow cylinders. This study aims to facilitate the application of BFRP in the field of structural reinforcement of glued wood hollow columns. Ten glued laminated wood hollow columns of the same size were designed and placed into five groups (ZC1 and ZRC2 to ZRC5), of which one group (ZC1), with a total of two pure wooden columns, was not arranged with BFRP, and the remaining two wooden columns in each group were arranged with BFRP at different distances. The destruction mode, ultimate load capacity, load–displacement curve, load–strain curve, and ultimate load capacity–total area of the BFRP paste curve of each specimen were obtained by conducting axial compression tests on five groups of wood columns reinforced with different basalt fiber cloths, which revealed the damage mechanism, the relationship between the ultimate load capacity and total area of BFRP paste, and pointed out the most effective area ratio. The test results show that the destruction mode of axially pressed, glued, laminated wood hollow columns is typical compression buckling damage, mainly manifested as follows: the wood at the middle or end of the specimen under pressure first buckles; then, with the increase in load, the specimen is crushed; at this time, the maximum ultimate bearing capacity of each specimen is in the range of 296.77~375.85 kN, the maximum longitudinal displacement is in the range of 2.77~3.38 mm, and longitudinal cracks appear at the end. It is worth noting that the growth rate of the ultimate bearing capacity varies with the increase in the total area of the BFRP paste. When the total area of the BFRP paste is less than a 3.2 × 105 mm2 range value, the growth rate of the ultimate bearing capacity is faster, and then, the growth rate gradually becomes slower. The optimum BFRP paste area ratio can be taken as k = 0.59. The ultimate bearing capacity after reinforcement increases from 11.06% to 26.65% compared with the pure wood column. According to GB50005-2017, “wood structure design standards” improve the hollow wood column bearing capacity calculation method and fit the BFRP reinforced hollow wood column’s ultimate bearing capacity calculation formula; the errors are within ±10%, which can provide a reference for the practical application of BFRP in the field of reinforcing glued wood hollow cylindrical structures.

Collision characteristics of the intermediate coupler of a rail vehicle

Suppose the intermediate coupler of a rail vehicle is unstable during the collision process and loses its connection and energy dissipation functions. In that case, it will significantly reduce the performance of the train crashworthiness function and increase the risk of train derailment. This paper aims to establish a refined finite element model (RFEM) that can simulate the buckling behaviour and investigate the bending resistance and buckling instability characteristics of the intermediate coupler, and the accuracy of the RFEM was verified by quoting the results of an existing intermediate coupler impact test. The results demonstrated that the proposed coupler modelling method could better simulate the energy absorption characteristics and unstable behaviour. Compared to the test results, the differences in the initial crushing force, maximum longitudinal compression displacement, minimum crushing force, and maximum crushing force were 6.5%, 1.3%, 3.6%, and 6.5%, respectively. Within the allowable range of parameters, the maximum bending force linearly increased with an increase in the initial longitudinal compression displacement. As the pitch or yaw angle increased, the longitudinal buckling load of the coupler linearly decreased and became more sensitive to the pitch angle. When pitch and yaw angles existed simultaneously, the longitudinal buckling load was further reduced.

Analysis of Wind-Sand-Load-Induced Dynamic Response of Transmission Tower-Line Systems

Sandstorms are a common natural phenomenon that has the potential to cause severe disruptions to civil infrastructure. However, the effect of sandstorms on transmission tower structures has not received much attention. This paper proposes the simulation of the wind-sand loads for the analysis of transmission tower structures under sandstorm excitation by superposing the wind loads and sand particle loads. The wind load is generated based on Kaimal fluctuating wind power spectrum and the harmonic superposition method, and the sand load is constructed based on the law of conservation of momentum and sandstorm classification. A transmission tower was modeled and simulated in SAP2000 to explore the dynamic response of the tower towards wind-sand loads. A comparison of wind-induced and wind-sand-induced responses shows that the structural dynamic responses of transmission towers due to the wind-sand effect are pronounced. Particularly, the maximum longitudinal displacements and axial forces increased greatly. The results showed that the sandstorm loads for transmission towers cannot be neglected, and more attention should be paid to the structural design of transmission towers to resist such loads.

Study on Longitudinal Stress Relaxation Effect and Reinforcement Technology of Segment Lining during Shield Docking

Shield docking technology is widely used in underwater shield tunnels. As the technology is not perfect, the instability of the tunnel face and the stress relaxation of segment lining caused by shield dismantling need to be solved. Using a cross-sea tunnel project, the segment lining reinforcement technology with steel channel in the process of shield docking is studied. The longitudinal stress relaxation effect of segment lining after thrust unloading is analyzed, and the theoretical solution of segment circumferential joint opening, with or without steel channel reinforcement, is derived. The accuracy of the theoretical model and the shell connector numerical model is verified by comparison. Then, the influence of key parameters, such as reinforcement range, steel channel quantity and steel channel model, on reinforcement effect is discussed. The results show that: (1) with the increase in the range of reinforcement, the maximum longitudinal displacement and the opening of the circumferential joints decrease first and then increase; (2) with the increase in the quantity and model of the steel channel, the maximum longitudinal displacement and the opening of the circumferential joints gradually decrease, and the reduction rate also decreases. The farther away from the shield tail, the weaker the reinforcement effect on segment lining.

Analysis on excavation stability of tunnel portal with different design methods

The stability of tunnel portal has its particularity. Due to the influence of natural or human factors, it is easy to produce cracking, landslide, collapse and other diseases. Taking the No.5 highway tunnel of F3 bid in Georgia as the background, using the finite element analysis software MIDAS-GTS to establish a three-dimensional model to simulate the tunnel construction process. The tunnel portal adopts two design schemes of micro pile wall support and bolt mesh shotcrete support. Through the analysis and comparison of the transverse and vertical displacement and stress field characteristics of surrounding rock caused by two schemes of tunnel excavation, the influence of tunnel excavation on the stability of tunnel portal is studied. The numerical results show that the maximum transverse and longitudinal displacements of surrounding rock are 3.55mm and 8.73mm respectively, and the maximum tensile stress is 1.91mpa. Compared with the micro pile wall support design, the bolt mesh shotcrete support scheme is more feasible. The conclusion has a certain guiding role for the construction of highway tunnels in mountain areas.

A Simplified Analysis Method for the Deformation Response of an Existing Tunnel to Ground Surcharge Based on the Pasternak Model

Surface surcharge changes the existing equilibrium stress field of the stratum and adversely affects the existing tunnel. This paper presents a simplified analytical solution for calculating the longitudinal displacement of existing tunnels that are subjected to adjacent surcharge loading. Based on the Boussinesq solution, the distribution of the additional load matrix caused by the surface surcharge on the existing tunnel was obtained. A Euler–Bernoulli beam with a Pasternak foundation was used as a simplified model for tunnel stress analysis. Using the corrected reaction coefficient of the foundation bed, the differential equation of tunnel deformation was established, and the solution matrix of the longitudinal displacement of the tunnel was obtained by using the finite difference method. The reliability and applicability of the proposed method were verified by comparing the results with finite element simulation results, field test data, and the calculation results of three simplified elastic analysis methods with different foundation bed coefficients. On this basis, the parameters of the load–tunnel model were analyzed, and the effects of the buried depth, the size of the load, the relative positions of the load and the tunnel, and the relative stiffness of the tunnel soil on the maximum displacement of the existing tunnel were calculated. An empirical formula is proposed for calculating the maximum longitudinal displacement of the existing tunnel subjected to surface surcharge. The findings of this research can provide a basis for the theoretical verification of the deformation response of an existing tunnel subjected to adjacent surface surcharge.

Research on the longitudinal mechanical behaviours of subway turnouts of large slope under train braking force.

To study subway turnouts' adaptability to steep gradients, a finite element model of a metro No. 9 simple turnout was established. The main works include: (1) The train's most unfavourable loading condition was modelled. (2) The turnout's longitudinal displacement and stress were analysed with different gradients under the train braking load, temperature change load and a combination of the two, to determine the structure's safety and stability under the most unfavourable working conditions. (3) The turnout structure's cumulative longitudinal deformation under reciprocating load was studied. Both a fastener longitudinal resistance-displacement experiment under reciprocating load and a numerical simulation of No. 9 turnout modelled by the finite element modelling software, ANSYS, were carried out to study the gradient's influence on the turnout's longitudinal mechanical characteristics. (1) The turnout's longitudinal displacement and stress increase linearly with an increase in gradient and temperature change, both of which are unfavourable to the turnout structure. As the gradient increases from 0‰ to 30‰, the longitudinal stress and displacement increase by more than 10%. (2) The turnout's rail strength and displacement on a 30‰ slope under the most unfavourable load conditions are within the specification limitations. (3) Under reciprocating load, the fastener longitudinal stiffness decreases and the maximum and residual longitudinal displacement of the switch rail increase; an increased gradient intensifies these effects on the turnout.

Effect of Ambient Temperature on Catenary System

This paper investigates the effect of the ambient temperature change on the overhead catenary system (OCS). Thermal expansion/contraction of the components of the overhead catenary system (OCS) are considered. Simulation results show that the temperature stress has a much greater influence on the longitudinal positioning of the contact wire than on the horizontal and vertical positioning. When ambient temperature reduces to -60°C or rises to 60°C from design temperature of 20°C, the maximum longitudinal displacement of the positioner can reach as high as 304 mm, while the maximum horizontal and vertical displacement of the positioner is within 4 mm. The decrease of temperature leads to the increase of cable tension, and the increase of temperature leads to the decrease of cable tension. When the temperature decreases from 20°C to -60°C or rises to 60°C, the tension change rate of contact wire is less than 1%, while that of messenger wire is not more than 0.01%.

One-dimensional semi-analytical model on longitudinal thermal loads of a tram track pile-plank structure buried beneath the pavement

A novel pile-plank-supported ballastless tram track is employed in southeast of China to mitigate the foundation differential settlement in soft soil regions. In this structure, the channel rails are directly combined with the plank by fasteners and pads. In situ measurement data reveal that the foundation differential settlement is well controlled by this structure and the internal forces of the plank mainly depend on temperature variation. To assess the structural safety and improve the reinforcement design for the pile-plank structure, an efficient and precise calculation algorithm for internal forces of the structure is urgently required. In this work, a one-dimensional (1D) model is proposed to evaluate the longitudinal forces of the embedded pile-plank structure due to temperature variation. The constraints of rails and surrounding concretes (i.e., overlying pavement and the supporting layer) on the embedded structure are considered. The semi-analytical solution of this model is derived and a comprehensive calculation procedure is proposed. Based on the project of Shanghai Tram Line T1, a case study is undertaken to validate the proposed model. The results indicate that the maximum longitudinal displacement of the plank increases with the temperature variation. The critical displacement appears when the temperature variation rises to 15 ℃. The calculated longitudinal forces of the plank are in accordance with the in situ measurement data. This model provides a strong base to the reinforcement design of the pile-plank-supported ballastless tram track.

Numerical Simulation Study on Cross Construction of Seawall Engineering and Bridge Foundation

In view of the overlapping project between the double track bridge of Ningbo-Taizhou-Wenzhou expressway and seawall, the large-scale three-dimensional finite element calculation is carried out by using the finite element software ABAQUS, the displacement limit of bridge pier top is studied, the internal force deformation of bridge pile foundation and its variation law in the process of seawall filling and later consolidation settlement are analyzed, and the influence of sea seawall filling on the stress and deformation of bridge pile foundation is studied. The calculation results show that: the main pier in the enclosure side of the two main piers in the design scheme is most affected by the construction of seawall. At the end of seawall construction, the longitudinal displacement along the bridge is 25.56cm, the transverse displacement is -10.68cm, and the settlement is 3.49cm. From the beginning of seawall construction to 15 years after the completion of seawall, the maximum longitudinal displacement along the bridge is -80.87cm, the maximum transverse displacement is -38.94cm, and the maximum settlement is 382.2cm, in which the settlement during the construction period is 346.0cm, accounting for 90.5%. The calculation results of design scheme show that the displacement of bridge pier top is too large, and the tensile stress of bridge pile is also large, therefore, it is necessary to optimize the design scheme to reduce the displacement of the bridge.

MMP-2 and TIMP-2 expression, quantitative analysis and biomechanical changes in scar hypertrophy after autologous free transplantation of rabbit oral mucosa and scrotal skin.

This study aimed to investigate the long-term scar hypertrophy in the rabbit transplanted oral mucosa and scrotal skin with changed matrix environment, as well as the scar location expression, quantitative analysis of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2) and biomechanical changes in the transplanted tissues. The split-thickness skin grafts were collected from the oral mucosas and scrotal skins of 30 male rabbits, and prepared into reelpipes for autologous transplantation into the rabbit back muscular tissues. Samples were collected to carry out elastic tensile mechanical detection and histological observation. The maximum longitudinal tensile displacement of scrotal skin before 8 weeks of transplantation was greater than that after 8 weeks of transplantation (P < 0.05). The expression intensities of MMP-2 and TIMP-2 in the oral mucosa and in scrotal skin at 2 W time point were higher than those at To time point (P < 0.05). The expression quantities of TIMP-2 in oral mucosa and scrotal skin during 8–24 W were higher than those of MMP-2 (P < 0.05). At 8 W time point, the TIMP-2/MMP-2 ratio in scrotal skin was higher than that in oral mucosa (P < 0.05). MMP-2 and TIMP-2 expression in normal oral mucosa and scrotal skin is weak, but their expression is remarkably up-regulated after 2 weeks of transplantation, revealing that scar formation was related to the high expression of MMP-2 and TIMP-2. At the 8th–24th weeks, the AOD values of TIMP-2 in oral mucosa and scrotal skin are apparently higher than those of MMP-2; moreover, the TIMP-2/MMP-2 ratio in scrotal skin at the 8th week was higher than that in oral mucosa, which can well explain the earlier scar formation in scrotal skin than in oral mucosa, and it also suggests that the different expression levels between TIMP-2 and MMP-2 may account for the important cause of scar formation.

Study on the Influence of Mud Properties on the Stability of Excavated Face of Slurry Shield and the Quality of Filter Cake Formation

In the construction of subsea tunnels, the stability and control of the excavation surface are the main concerns of the engineering community. In this paper, the Xiamen Metro Line 2 is used as the study case. The filter cake formation of mud shields is experimentally studied, and the excavation surface is numerically simulated. It is found that the formation of filter cake does not require a large pressure difference, and can be formed under 0.06 MPa. With the increase of pressure, the quality of filter cake is further improved, and a small amount of seawater (volume ratio less than 3%) also has a significant effect on the viscosity of mud. Under different cross-section geological conditions, with the decrease of the support pressure of the excavation face, the vertical displacement and vertical (Y-direction) displacement of the excavation face dome gradually increase, the maximum longitudinal displacement is 9.7 mm, the maximum longitudinal displacement can reach 23.9 mm, and the growth trend is nonlinear. According to different stratum conditions, during the excavation of the tunnel, the plastic area of the excavation face is different.

Influence of Fluid Viscous Damper on the Dynamic Response of Suspension Bridge under Random Traffic Load

Fluid viscous dampers (FVDs) are widely used in long‐span suspension bridges for earthquake resistance. To analyze efficiently the influences of FVDs on the dynamic response of a suspension bridge under high‐intensity traffic flow, a bridge‐vehicle coupling method optimized by isoparametric mapping and improved binary search in this work was first developed and validated. Afterwards, the traffic flow was simulated on the basis of monitored weigh‐in‐motion data. The dynamic responses of bridge were analyzed by the proposed method under different FVD parameters. Results showed that FVDs could positively affect bridge dynamic response under traffic flow. The maximum accumulative longitudinal girder displacement, longitudinal girder displacement, and longitudinal pylon acceleration decreased substantially, whereas the midspan girder bending moment, pylon bending moment, longitudinal pylon displacement, and suspender force were less affected. The control efficiency of maximum longitudinal girder displacement and accumulative girder displacement reached 33.67% and 57.71%, longitudinal pylon acceleration and girder bending moment reached 31.51% and 7.14%, and the pylon longitudinal displacement, pylon bending moment, and suspender force were less than 3%. The increased damping coefficient and decreased velocity exponent can reduce the bridge dynamic response. However, when the velocity exponent was 0.1, an excessive damping coefficient brought little improvement and may lead to high‐intensity work under traffic flow, which will adversely affect component durability. The benefits of low velocity exponent also reduced when the damping coefficient was high enough, so if the velocity exponent has to be increased, the damping coefficient can be enlarged to fit with the velocity exponent. The installation of FVDs influences dynamic responses of bridge structures in daily operations and this issue warrants investigation. Thus, traffic load should be considered in FVD design because structural responses are perceptibly influenced by FVD parameters.

Dinamička analiza portalne dizalice pri većem broju pokreta kolica i korisnog tereta

The aim of this research is to study the dynamic behaviour of a real gantry crane subjected to the actions induced by the trolley and payload movement. A specific numerical procedure was developed and implemented in the finite element method in order to simulate different trolley movement modes on the crane's main beam. From the results, it is clear that the crane displacement, especially the longitudinal one, is strongly dependent on the acceleration both in the starting phase and in the stopping phase to which the trolley is subjected during its movement on the crane main beam. The last part of this research simulates the sudden stop of the trolley movement and subsequent payload swinging; in this case, the length of the rope that suspend the payload to the trolley has a fundamental role in the trend and maximum longitudinal crane displacement value.

An analytical calculation method for displacement and force on continuous welded rails in temperature-transition zone

Abstract The rails at the transition between a bridge or subgrade and a tunnel tend to creep longitudinally because of a temperature gradient on the rail, which can cause irregularity in the track. The longitudinal temperature distribution along the rail and the longitudinal resistance of the fasteners are the main influences on rail creep. In this paper, the linear and nonlinear models of longitudinal temperature distribution on rails and the longitudinal resistance of fasteners are tested for their accuracy in predicting rail creep. By researching the rail at the temperature-transition zone, differential equations for the longitudinal displacement and force of the rail are established. To predict the changes that a rail will experience in a temperature-transition zone, expressions for the longitudinal displacement and force are derived from these differential equations. The derived calculation scheme is tested for three conditions: linear models of both rail temperature and longitudinal resistance, linear rail temperature and nonlinear resistance, and nonlinear models of both rail temperature and displacement. The maximum longitudinal rail displacement and the maximum longitudinal additional force in all three conditions are compared to reveal the influence of the maximum temperature force gradient multiple and the maximum fastener resistance on longitudinal displacement.

Theoretical modeling of spatially varying ground motions under ice-seawater interface and earthquake analysis of cable-stay bridges

The ice-seawater interface has a significant effect on earthquake-induced ground motion. This paper proposed a new method of modeling spatially varying ground motion due to ice-seawater layer. The reflection function was derived to evaluate the effect of ice-seawater layer on earthquake ground motion. Moreover, the coherence function and site transfer function were used to calculate the loss of spatial coherent and the corresponding local effects, respectively. Furthermore, the effects of water saturation on ground motion was considered. Taking the above factors into consideration, the spatial variance of seismic ground motions in an area with an ice-seawater interface was synthesized. The ground motion was assumed to consist of SH and P-SV waves, which included horizontal out-of-plane SH wave, horizontal in-plane P-SV waves and vertical in-plane P-SV waves. By comparing simulated ground motions with different site conditions, we observed that the vertical in-plane motion at the seafloor was noticeably attenuated when an ice-seawater interface was present. At the same time, the soil layer greatly amplified the acceleration of out-of-plane and in-plane ground motions. In order to verify the ability of the above method for synthesizing seismic time history, a three-dimensional seismic analysis of a large span cable-stayed bridge was conducted. Three of such case studies were used to investigate the effect of the ice-seawater interface on the bridge. Analysis of the displacement and bending moment of the bridge deck and tower demonstrated that the ice-seawater interface had a great effect on the seismic response of the cable-stayed bridge. In particular, the maximum vertical deck displacement with the ice-seawater interface present was 74% of the case in which the interface was absent. Likewise, the maximum longitudinal displacement of the bridge tower with the interface present was 70% of the case in which the interface was absent.