港珠澳大桥青州航道桥主体防雷设计

桥梁多位于水陆交界处，地势空旷，极易遭受雷击。对桥梁雷电暂态特性及相关效应进行定量分析，可为桥梁的防雷设计提供科学的数据支撑。本文以单塔斜拉索桥梁为例，利用CDEGS (Current Distribution Electromagnetic Interference Grounding and Soil Structure Analysis)软件建立桥梁三维仿真模型，模拟一般斜拉索结构桥梁的塔顶、斜拉索和桥面分别遭受直击雷时，桥梁磁场、跨步电压及雷电流分布情况。结果表明：(1)雷击斜拉索时，桥梁电子信息设备安装处磁场强度峰值最大，雷击塔顶时次之，雷击桥面时最小；雷击斜拉索时桥梁下方地面处的跨步电压峰值最大，雷击桥面时桥梁下方地面处的跨步电压峰值最小；(2)斜拉索上雷电流的大小分布与雷击点位置、斜拉索与接地体之间的距离以及斜拉索长度有关，斜拉索离接地体位置越近，长度越短，其上流过的雷电流越大；(3)接地体上雷电流的大小分布与雷击点位置及接地体的布设位置相关。距离雷击点位置越近，接地体上的雷电流幅值越大，布设在中间位置的接地体由于屏蔽效应雷电流呈现大幅减小的现象；布设在边缘位置的接地体上的雷电流波前时间变化不大，对原始雷电波陡度的削减作用不明显，而布设在中间位置的接地体上雷电流波前时间呈大幅升高的趋势，降低了雷电波因陡度大而造成的危害。

Lightning protection design for the main structure of Hong Kong-Zhuhai-Macao Qingzhou Bridge

Bridges are usually located at the junction of land and water, where the surrounding area is open terrain, making them to be easily damaged by lightning strikes. The quantitative analysis of lightning transient characteristics and the impulse effect on bridges can provide scientific data to support the lightning protection design for bridges. In this study, a single-tower cable-stayed bridge is taken as a representative case. The CDEGS (Current Distribution Electromagnetic Interference Grounding and Soil Structure Analysis) software is used to establish a three-dimensional simulation model of the bridge. With this model, the magnetic field, step voltage, and lightning current distribution on the tower top, stay cables, and bridge deck under the most severe direct lightning strike scenario typical for cable-stayed structures are simulated. The results are as follows: (1) when the stay cables are struck by lightning, the peak of the magnetic field intensity is highest at the location of electronic information equipment, followed by that at the top of the tower, and the lowest at the bridge deck. The peak step voltage at the ground below the bridge is the largest when lightning strikes the cable, and that is the smallest when lightning strikes the bridge deck. (2) The magnitude distribution of the lightning current on the stay cables is related to the strike location, the distance between the strike point and the grounding system, and the length of the stay cables. When the stay cables are closer to the grounding system and the length is shorter, the lightning current that flows through them is larger. (3) The magnitude distribution of the lightning current on the grounding system is associated with the location of the strike and the position of the grounding system. The closer the grounding system is to the strike point, the larger the amplitude of the lightning current on the grounding system. The grounding system positioned in the middle significantly reduces the lightning current due to the shielding effect. The grounding system located at the edge shows minimal variation in the time domain characteristics of the lightning current, resulting in less reduction of the initial steepness of the lightning wave. However, the grounding system at the middle position experiences a significant increase in the temporal characteristics of lightning current, reducing the hazards caused by the steepness of the original lightning wave.