Seismic Analysis and Measurement of a Intake tower of reservoir.

(1)地震测量：1995年2月，将地震仪安装在钢筋混凝土、42米高的“NAGARA”大坝进水塔闸门操作室。从4月初到7月，地震仪记录了10次地震。其中8个事件的最大记录加速度小于10 gal， M<5.0。离相上湾地震发生在1995年7月3日，最大水平加速度为42加仑，震级为5.6级，震中距离为60公里。该记录用于塔的响应分析。(2)利用坝基加速度作为塔的输入运动：由于没有合适的装置来指定塔的输入地震运动，“NAGARA”坝基地震仪采用了另一种记录。为此，“水资源开发合作”提供的各种援助得到赞赏。(3)塔体力学模型的确定：采用常规梁柱有限元模型和能够表达基础晃动的修正梁柱模型进行响应分析。由于材料力学常数通常是未知的，无法最好地表达结构的观察到的自然周期，因此选择这些常数是为了使模型分析能最好地表达观察到的自然周期。在这些条件下，与观测到的加速度过程相比，正常模型在统计意义上具有相当好的符合性。但在某些材料常数的组合作用下，摇摆振动模型给出的响应值较大。

(1) Earthquake Measurement : In February 1995, the seismometer was installed in the gate operation room of the "NAGARA" dam intake tower which is RC and is 42m high. From the beginnings of April to July, 10 events were recorded by the seismometer. The maximum recorded acceleration of 8 events among them were smaller than 10 gal and M<5.0. The off-SAGAMI bay event occurred in '95,7,3 took the maximum horizontal acceleration of 42 gal, and of which magnitude is 5.6 and epicentral distance is 60 km. This record was used for the response analysis of the tower.(2) Use of acceleration in the dam foundation as a input motion to the tower : As there are no suitable devices which specify the input earthquake motion to the tower, an alternative record was adopted by the "NAGARA" dam foundation seismometer. To use this, various aids by "Water Resources Development Cooperation" were appreciated.(3) Approval of the mechanical model of the tower : Response analyzes using both normal beam-column FEM model and modified beam model which is able to express rocking of the foundation were carried out. Because the material mechanical constants are generally unknown to best expressing the observed natural period of the structure, these constants were chosen so that the model analyzes best express the observed natural periods. Under these conditions, normal model gave considerably good coincidence in the statistical sense comparing to the observed acceleration process. But under some combination of material constants, rocking vibration model gives a larger response value.