| Multi-Point Input Method is necessary in Seismic Response Analysis of large scale earth dam, because the points move unsynchronously on the interface between the structure and surrounding rock, and the researching task was initiated by M. Dibaj and J. Penzien in 1969. Whether the earth dam lapses in Seismic Response Analysis is mainly judged by two criterion, the Damage Value and the permanent displacement, so the difference of response between Multi-Point Input and One-Point Input, that is the Multi-Point Effect, is also checked by this two criterion. Therewith the method to calculate Damage Value and permanent displacement is studied too. The Multi-Point Input is two directional, one direction is along river, and another is vertical. By way of parenthesis, In One-Point Input Method the relation is studied between the response and the correlative coefficient of horizontal and vertical earthquake wave. After reviewing the past work, 6 aspects of researching is developed as following:1. A more reasonable method to calculate soil's Damage Value is advanced, which bases on extrema of irregular dynamic shear stress. Previously it bases on peaks of shearstress to calculate Damage Value, but by this method the destructive action of Multi-Point Inputted earthquake is overestimated, especially in the second half section of responding shear stress' time history the shear stress caused mainly by differential force undulate slightly on one side of its zero line. Moreover the overestimated Damage Value increases along with the Delayed Time. The new method overcomes the old methods' shortcoming.2. The idea and method to velocity-zeroize artifical accelerations is put forward. The precious method to simulate earthquake accelerations is not perfect because the points on the interface still move according to the simulated acceleration when the points' motion ends, which is obviously a paradox. If the points' velocity is not zeroized, soil's Damage Value based on shear stress's peaks or extrema is overestimated in Multi-Point Input Analysis. The new method's rationality is analyzed.3. The way to calculate the Equivalent Joint-force is consummated in the Equivalent Joint-force Method to calculate dam's permanent displacement caused by earthquake. It's thought that dam's permanent displacement by Multi-Point Input includes two parts, the first is caused by the Accumulated Damage, while the second is incidental to the basement's permanent displacement. Based on computation, the second part can be neglected because it is relatively small. The permanent displacement caused by Accumulated Damage is calculated in Equivalent Joint-force Method, while the way to calculate the Equivalent Joint-force is consummated, both in the Equivalent Joint-forceMethod of Horizontal Face and Maximal Static Shear Stress Face.4. The Multi-Point Effect in time domain is studied. If the inputted accelerations are velocity-zeroized and the Damage Value is calculated according to shear stress' extrema, as to 100-meter-high earth dam, Multi-Point Effect is not distinct; But as to 240-meter-high earth dam, in the part where permanent displacement and Damage Value is originally bigger the response is less tenser than that by One-Point Input, and in the part near basement the maximal shear stress and Damage Value is bigger, that is the Multi-Point Effect in time domain. Weaker the synchronicity of inputted accelerations is, for example, smaller the velocity of earthquake wave is, stronger the Multi-Point Effect is. The Multi-Point Effect with input of the artificial earthquake acceleration simulated by Interpolation Method is weaker than that of the directly simulated acceleration.5. The Multi-Point Effect in frequency domain is studied, and the analytical procedure is simplified to some extent, that is, the responding data is accurate enough only with the input according to the first four degressively arranged eigenvalue of earthquake power spectrum matrix. There are disaccordant conclusions of Multi-Point Input Analys...
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