Auto-parametric resonance of a continuous-beam-bridge model under two-point periodic excitation:an experimental investigation and stability analysis

The auto-parametric resonance of a continuous-beam bridge model subjected to a two-point periodic excitation is experimentally and numerically investigated in this study.An auto-parametric resonance experiment of the test model is conducted to observe and measure the auto-parametric resonance of a continuous beam under a two-point excitation on columns.The parametric vibration equation is established for the test model using the finite-element method.The auto-parametric resonance stability of the structure is analyzed by using Newmark's method and the energy-growth exponent method.The effects of the phase difference of the two-point excitation on the stability boundaries of auto-parametric resonance are studied for the test model.Compared with the experiment,the numerical instability predictions of auto-parametric resonance are consistent with the test phenomena,and the numerical stability boundaries of auto-parametric resonance agree with the experimental ones.For a continuous beam bridge,when the ratio of multipoint excitation frequency(applied to the columns)to natural frequency of the continuous girder is approximately equal to 2,the continuous beam may undergo a strong auto-parametric resonance.Combined with the present experiment and analysis,a hypothesis of Volgograd Bridge's serpentine vibration is discussed.

Influence of liquid bridge force on physical stability during fuel storage and transportation

The physical stability of solid-liquid fuel is a factor that needs to be considered for fuel product practicability for storage and transportation. To determine the Influence of liquid bridge force on physical stability, two detection devices were designed. The laws obtained from microscopic experiments are used to verify the physical stability of fuel under different component ratios. The liquid bridge force is found to increase with the droplet volume. Multiliquid bridges above one critical saturation can generate significant resultant forces compared to single-liquid bridges of the same volume. There exist four states of solid-liquid mixed fuel with increasing liquid saturation rate. The liquid bridge force between the solid and liquid plays a dominant role in the physical stability of the first three states. There may be two stages involved in the stratification process for state 4 fuel, and the liquid viscosity is another factor that cannot be ignored. In the process of selecting a fuel ratio, a larger liquid bridge force between the components can be obtained by properly improving the wetting effect so that the fuel shows better physical stability.

Nonlinear Stability Analysis of Long Span Continuous Rigid Frame Bridge with Thin Wall High Piers

By utilizing the current finite element program ANSYS, two types of finite element models (FEM), the beam model (BM) and shell model (SM), are established for the nonlinear stability analysis of a practical rigid frame bridge—Longtanhe Great Bridge. In these analyses, geometrical and material nonlinearities are simultaneously taken into account. For geometrical nonlinearity, updated Lagrangian formulations are adopted to derive the tangent stiffness matrix. In order to simulate the nonlinear behavior of the plastic hinge of the piers, the multi lines spring element COMBIN39 is used in the SM while the bilinear rotational spring element COMBIN40 is employed in the BM. Numerical calculations show that satisfying results can be obtained in the stability analysis of the bridge when the double coupling nonlinearity effects are considered. In addition, the conclusion is significant for practical engineering.

Aerodynamic stability of cable-supported bridges using CFRP cables

To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.

Study of the aerostatic and aerodynamic stability of super long-span cable-stayed bridges

With the increase of span length, the bridge tends to be more flexible, and the wind stability be- comes an important problem for the design and construction of super long-span cable-stayed bridges. By taking a super long-span cable-stayed bridge with a main span of 1 400 m as example, the aerostatic and aerodynamic stability of the bridge are investigated by three-dimensional nonlinear aerostatic and aerodynamic stability analy- sis, and the results are compared with those of a suspension bridge with a main span of 1 385 m, and from the aspect of wind stability, the feasibility of using cable-stayed bridge in super long-span bridge with a main span above l 000 m is discussed. In addition, the influences of design parameters including the depth and width of the girder, the tower structure, the tower height-to-span ratio, the side-to-main span ratio, the auxiliary piers in the side span and the anchorage system of stay cables, etc on the aerostatic and aerodynamic stability of su- per long-span cable-stayed bridges are investigated numerically; the key design parameters are pointed out, and also their reasonable values are proposed.

Stability Analysis of Long-Span Continuous Rigid Frame Bridge with Thin-Wall Pier

During cantilever cast in construction of high-pier and large-span continuous rigid frame bridges, structural stability in the longest cantilevered stage is very important. Based on a practical design case of a large-span continuous rigid frame bridge in Wuhan, the longest span stability coefficient is calculated with linear-buckling and nonlinear-buckling methods, respectively. The influences of both geometrical nonlinearity and the dual nonlinearity of material and geometry are considered. Numerical results indicate that the nonlinear solution is necessary to stability analysis because linear buckling loads are much higher than those of nonlinear buckling. Thus, the edge fiber yield criterion is more convenient and faster than ultimate loading criterion when estimating nonlinear stability of structure, and can be used easily in the initial engineering design.

Aerodynamic stability of cable-stayed-suspension hybrid bridges

Three-dimensional nonlinear aerodynamic stability analysis was applied to study the aerodynamic stability of a cable-stayed-suspension (CSS) hybrid bridge with main span of 1400 meters, and the effects of some design parameters (such as the cable sag, length of suspension portion, cable plane arrangement, subsidiary piers in side spans, the deck form, etc.) on the aerodynamic stability of the bridge are analytically investigated. The key design parameters, which significantly influence the aerodynamic stability of CSS hybrid bridges, are pointed out, and based on the wind stability the favorable structural system of CSS hybrid bridges is discussed.

Rock bridge slice element method in slope stability analysis based on multi-scale geological structure mapping

The searching method of failure surface which consists of complex geological structures in high and steep rock slopes was studied. Based on computer simulation technology and Monte-Carlo method, three dimensional multi-scale geological structures such as engineering scale and statistical scale structures of the slope were simulated. The searching method of failure route which consists of joints and rock bridges was determined via simulation annealing method by considering the shear strength of joints or rock bridges in one supposed route. When shear strengths of all the supposed routes were computed, the least shear strength route was considered failure route. Then, the inclined slice of joint slices and rock bridge slices were separated according to the position of joints and rock bridges. For the rock bridge slices, by distinguishing the failure model, the force direction to the next slice was defined. Finally, the limit equilibrium equations for every slice were established, and the slope stability factor was obtained. One practical example indicates that the discussed method is more closely to the real condition.

Impedance Modeling and Stability Analysis of Dual Active Bridge Converter with LC Input Filter

The dual active bridge(DAB)converter is gaining more and more attention in various applications such as energy storage systems,electric vehicles and smart grids.To improve the quality of the input current,a LC filter is often cascaded at the input side of the DAB converter.However,there are instable problems of this cascaded system due to the impedance interactions of the DAB converter and the LC filter,although the DAB converter is stable at the individual operation mode.To assess the stability of the cascaded system of the DAB converter and the LC filter,the impedance model of the DAB converter is firstly developed based on generalized state-space averaging method.The developed impedance model can be used to accurately predict the stability of the DAB converter with its LC input filter.Based on the stability analysis,the optimum filter parameter design guideline is determined.The impedance model and stability analysis are validated by the simulation and experimental results.

Geologic Survey and Stability Analysis for the South Tower Pier of Jiangyin Yangtze Highway Bridge

Jiangyin Yangtze highway bridge is a suspension bridge with main span 1 385 m. The south tower pier is located on a 70 m bedrock slope with bedding plane of strata tipping to the river channel and several weak intercalated layers. The stability of the tower pier is one of the main engineering geologic problems. On the basis of investigation and survey of relevant geologic condition analyses, the geomechanical model experiments are carried out for stability study of various foundation alternatives’ advantages and disadvantages. Pile foundation has been finally adopted and constructed, and this is justified by practice.

Aerodynamic stability of cable-stayed bridges under erection

In this work, nonlinear multimode aerodynamic analysis of the Jingsha Bridge under erection over the Yangtze River is conducted, and the evolutions of structural dynamic characteristics and the aerodynamic stability with erection are numerically generated. Instead of the simplified method, nonlinear multimode aerodynamic analysis is suggested to predict the aerodynamic stability of cable-stayed bridges under erection. The analysis showed that the aerodynamic stability maximizes at the relatively early stages, and decreases as the erection proceeds. The removal of the temporary piers in side spans and linking of the main girder to the anchor piers have important influence on the dynamic characteristics and aerodynamic stability of cable-stayed bridges under erection.

Research on the Multidimensional Constraint Stability of Bridge Structure Modeling based on Optimization Model

In this paper, we conduct research on the multidimensional constraint stability of bridge structure modeling based on the optimization model. The current internal and the external research results to the truss web structure, the high internode the aspect ratio and the stiffness of the middle truss brace of the truss web, deffection of composite beams of the impact of stress is a very important problem in the design of the bridge. Structural health monitoring is the use of the field of the non-destructive sensing technology, including the structural response, including structural system characteristics analysis, to achieve the purpose of monitoring structural damage or degradation. Under this basis, this paper proposes the new idea on the modelling and simulates the performance.

Study on stability of road and bridge based on stress analysis and computer modeling

In this paper, some concepts and problems in the stress analysis design method are discussed. Based on the introduction of various types of stress characteristics, the differences between stress decomposition and stress classification are emphasized. We pointed out that the stress decomposition only relates how stress is decomposed into uniform stress, the equivalent stress distribution of linear and nonlinear stress components, how will break out of stress classification, entirely by the stress position and stress the external decision. At the same time, it also gives a valuable perspective on the distribution twe ofoeak stress, the self limitation and the stress decomposition and classification.

Long-Time Behavior of Solution for Autonomous Suspension Bridge Equations with State-Dependent Delay

This work is devoted to the following suspension bridge with state-dependent delay: . The main goal of this paper is to investigate the long-time behavior of the system. Under suitable hypothesis, the quasi-stability estimates of the system are established, based on which the existence of global attractor with finite fractal dimension is obtained. Furthermore, the existence of exponential attractor is proved.

The stability safety factor calibration based on the reliability index

When the bridge structure stability safety factor of the first type is 4, the research that whether the structure reliability index will reach target reliability index under the more-likely-to-happen collapse situation of the second type is necessary. The stability calculations of the first and the second type are made respectively for single layer and single span rigid frame bridge. Based on the critical load obtained from the stability calculation of the first type, the stability safety factor of the first type is taken as 4, and the first order reliability method is used to program and calculate the reliability index. Then, the load effect under the stability reliability index cal- culation of the first type and the critical load of the second type are employed to calculate the reliability index of the second type. The evaluation of structure stability safety factor is discussed according to reliability index. Based on the discussion above, parameter analysis of the stable critical loads of two types is made, and the in- fluence of critical load change on reliability index is researched. The result shows that stability analysis should identify collapse state; when the stability safety factor of the first type is 4, but the structure has the collapse of the second type, the reliability index cannot be ensured to reach the target reliability index under certain condi- tions.

Spatial gust impact analysis on safety and comfort of a train crossing cable-stayed bridge combining statistical method

In order to study the safety and the comfort of high-speed trains running on a single-tower cable-stayed bridge under spatial gust,a dynamic model of wind-train-bridge analysis model is built based on the autoregressive method,the multi-body dynamics method and the finite element method.On this basis,the influence of spatial gust model loading,the suspension parameters change,wind attack angle and speed on the train-bridge system are analyzed by combining the time/frequency domain analysis and statistical methods.The results show that the spatial gust environment is one of the most important factors affecting safety and comfort and can make the calculation result tend to be conservative and more conducive.The response changes caused by K_(py),K_(px) and K_(sx) changes are nearly linear,while Ksy shows nonlinear characteristics and the most sensitivity.Wind attack angle at 75°and 90°has the greatest influence on the vehicle-bridge system.For ride comfort index,when pre-set wind speed(α=75°)reaches 20 m/s,the vertical acceleration firstly exceeds the limit value;when wind speed(α=90°)reaches 21.5 m/s,the lateral acceleration firstly exceeds the limit value,and the ride comfort of the vehicle cannot be guaranteed.For running safety index,when pre-set wind speed(α=75°)reaches 24.6 m/s,the wheel unloading coefficient firstly exceeds the limit;when pre-set wind speed(α=90°)reaches 24.5 m/s,the derailment coefficient firstly exceeds the limit,and the running safety cannot be guaranteed.The results can provide a suitable reference for the safe and stable operation of trains on the bridge.

Research on key technologies in design of middle pylon of Taizhou Bridge

At the middle pylon of a three-pylon two-span suspension bridge, the effect of unbalanced loads on the adjacent spans may result in a series of technical bottlenecks in design, such as stability and anti-slippage between saddles and main cables. This article presents the researches conducted on structure selection and behavior characteristics of middle pylon, interaction mechanism between main cables and saddles and their anti-slippage safety performance, elastic and plastic stability analysis and safety assessment of steel middle pylon, and fatigue design load and method for steel pylon of Taizhou Bridge. According to the research results, a longitudinal inverted Y shape steel middle pylon is used in design, effectively solving many technical difficulties, and this type of pylon has become a suitable middle pylon structural form for many three-ovlon two-soan susoension bridges.

公铁两用大跨度斜拉桥-无砟轨道体系变形适应性研究

高速铁路大跨度斜拉桥结构变形受其复杂服役环境影响显著,而无砟轨道对工后变形的调整能力有限,因此大跨度斜拉桥的复杂变形条件将直接影响其上无砟轨道结构的适应性。以沪渝蓉高铁长江北支公铁两用大跨度斜拉桥应用无砟轨道为工程背景,建立无砟轨道-大跨度斜拉桥一体化精细空间有限元模型,分析铁路、公路以及温度等多种荷载联合作用下大跨度斜拉桥-无砟轨道体系平顺性、无缝线路稳定性和无砟轨道层间变形协调性,从而对大跨度公铁两用钢桁梁斜拉桥-无砟轨道体系变形适应性开展深入研究。结果表明:在运营荷载及温度荷载最不利组合作用下,大跨度斜拉桥主梁线形平顺,变形平缓,桥梁整体刚度较好,桥上无砟轨道几何形位可以满足静态验收标准;大跨度斜拉桥上无缝线路的强度和稳定性满足要求,扣件工作性能良好,钢轨伸缩调节器的设置可有效释放梁端钢轨的纵向应力;无砟轨道层间设置橡胶隔离层且不跨主梁桁架节间的布置方式可提高大跨度斜拉桥上无砟轨道的变形协调性能,使得桥上无砟轨道层间始终处于受压状态,达到“隔而不离”的桥上轨道层间理想服役状态;大跨度公铁两用钢桁梁斜拉桥-无砟轨道体系变形适应性良好。本文研究成果可为公铁两用大跨度钢桁梁斜拉桥上无砟轨道的应用提供技术参考。

大跨度上承式钢管混凝土拱桥受力性能分析

研究目的:为系统地掌握西北地区大温差、峡谷风、高震区共存的复杂建设条件下上承式钢管混凝土拱桥的力学性能,以一座净跨400 m的公路同类型拱桥为例,按照现行设计规范,采用统一模量法建立三维杆系有限元模型,对概率极限状态设计方法要求的静力性能、稳定性、动力特性、抗震性能的组合工况进行全面、系统地分析和计算,为同类型桥梁设计提供参考。研究结论:(1)温度效应大于汽车荷载效应,拱脚处横风效应突出;(2)双向偏压、偏拉组合受力为单弦杆控制设计状态,拱顶为桁式拱肋承载力的薄弱位置;(3)腹杆、横撑、平联等构件与弦杆构造匹配性较好时,承载力及疲劳性能等易满足受力需求;(4)温度、徐变预拱度比车道荷载大很多;(5)主拱圈在材料、几何、双重非线性下稳定性分别下降了5.5%、11.9%、17.1%;(6)振型相对密集、频率值较小,主振型为面外弯扭振动,具有多方向和多角度耦联性;(7)时程分析结果大于反应谱分析结果,但小于静力工况,拱桥抗震性能好;(8)上承式钢管混凝土拱桥在复杂建设条件下具有良好的受力性能。

桥梁缆索用87MnSi钢线材微观组织演变对力学性能的影响

针对桥梁缆索用87MnSi钢线材的异常断裂现象,对其盘条和生产工艺过程中钢丝的微观组织和力学性能演变规律进行系统分析。结果表明,盘条组织由珠光体和少量的先共析铁素体组成,且渗碳体片层随机分布。冷拉拔后,渗碳体片层发生扭转弯曲或减薄纤维化,且部分渗碳体发生破碎溶解,溶解量为1.40%(占比9.69%)。热镀锌后,溶解的渗碳体发生球化。盘条(329.8HV)在冷拉拔-热镀锌-稳定化处理过程中的显微硬度呈现先增大(450.2HV)后减小(447.9HV)再增大(469.6HV)的变化趋势;冷拉拔过程中溶解的渗碳体使得钢丝硬度值上升至468.3HV,而热镀锌过程渗碳体的球化,导致硬度值下降至439.8HV,并恶化拉伸性能。当边部的渗碳体球化程度明显时,使得钢丝内外组织和力学性能存在较大差异,并在稳定化处理过程中因受力不均匀而导致断裂。