拥堵状态下城市桥梁与汽车的共振分析

发布时间：2018-10-24 18:02

【摘要】：随着机动车辆保有量的迅速增长，交通拥堵现象在各大城市频频出现。研究发现，，汽车拥堵在静力荷载作用下，不会对城市桥梁造成直接的危害。但在动力荷载作用下，情况大不相同，车辆拥堵时发动机处于怠速状态，此时发动机转速在600~800转/分钟（频率为10.0~13.3Hz）内，此频率处于很大部分桥梁的基频（1.23Hz~14Hz）范围内。考虑发动机怠速振动，桥梁的位移和应力水平与静力荷载相比有显著的增加，当汽车发动机怠速转速与桥梁的某一阶频率相同或相近时，甚至可能发生车桥共振的现象。本文结合前人结构动力理论研究成果，查阅城市桥梁堵车状况相关统计资料，选取了一座具有代表性的城市桥梁来展开这方面研究。本文选取了深圳市某一三跨连续梁桥作为实例，根据城市车辆组成的统计分析和城市桥梁的车辆通行特点，对城市桥梁的车辆类型、车长、轴重、轴距、车间距等参数进行调查。选用大客车拥堵荷载作为荷载模型，研究了大客车怠速时的静力、动力荷载，并取发动机引起的动荷载幅值为静载的20%。由于拥堵动荷载效应与发动机的初相位有很大关系，本文从最不利荷载角度出发，设计了同相位或反相位的7种较为不利的堵车工况。利用ANSYS有限元模型，对桥梁实例进行仿真分析，获取桥梁的自振特性，并计算出桥梁在7种工况下的振幅-频率关系，以及3种最不利堵车工况下的桥梁瞬态响应。从而发现该桥梁双向堵车作用效应较单向堵车不利，竖弯振动比扭转振动的动载响应系数更大。最后通过修改该桥的约束条件，对简支梁桥及连续刚构桥的堵车共振效应进一步研究得出，同一堵车共振条件下，简支梁桥的振动效应最小；连续刚构桥竖弯振动响应比连续梁桥大，而扭转振动响应比连续梁桥小。可知对于小跨径城市桥梁，选择简支梁结构形式更有利于减少堵车共振引起的桥梁结构破坏。
[Abstract]:With the rapid growth of vehicle ownership, traffic congestion occurs frequently in major cities. It is found that vehicle congestion under static load will not cause direct harm to urban bridges. However, under the dynamic load, the situation is very different, the engine is in idle state when the vehicle is congested, and the engine speed is in the range of 600,800 rpm (frequency is 10.0~13.3Hz), which is within the 1.23Hz~14Hz range of most bridges. Considering the engine idling vibration, the displacement and stress level of the bridge are significantly increased compared with the static load. When the idling speed of the automobile engine is the same or close to the bridge's first order frequency, even the bridge resonance may occur. In this paper, based on the previous research results of structural dynamic theory, we select a representative urban bridge to carry out this study by referring to the relevant statistical data of the traffic jam situation of urban bridges. Based on the statistical analysis of urban vehicle composition and the traffic characteristics of urban bridges, this paper selects a one-three-span continuous girder bridge in Shenzhen as an example to study the vehicle types, vehicle length, axle load, wheelbase of urban bridges The distance between vehicles and other parameters were investigated. In this paper, the static and dynamic loads of bus at idle speed are studied by using bus congestion load as load model, and the dynamic load amplitude caused by engine is taken as 20 parts of static load. Due to the fact that the congested dynamic load effect is closely related to the initial phase of the engine, this paper designs seven unfavorable traffic jam conditions in the same phase or inverse phase from the point of view of the most unfavorable load. The ANSYS finite element model is used to simulate and analyze the bridge examples to obtain the natural vibration characteristics of the bridge. The amplitude-frequency relationship of the bridge under 7 working conditions and the transient response of the bridge under the three most unfavorable traffic jam conditions are calculated. It is found that the effect of two-way traffic jam of the bridge is more adverse than that of one-way traffic jam, and the dynamic load response coefficient of vertical bending vibration is greater than that of torsional vibration. Finally, by modifying the constraint conditions of the bridge, the resonance effect of traffic jam of simply supported beam bridge and continuous rigid frame bridge is further studied. It is concluded that the vibration effect of simply supported beam bridge is the least under the same condition of traffic jam resonance. The vertical bending vibration response of continuous rigid frame bridge is larger than that of continuous beam bridge, while the torsional vibration response is smaller than that of continuous beam bridge. For small span urban bridges, simply supported beam structure is more favorable to reduce the bridge structure damage caused by traffic jam resonance.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U491.265;U441.3

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