著者

小島 紘太郎 五月女 義人 竹脇 出

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.82, no.735, pp.643-652, 2017

被引用文献数

7

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&nbsp;After Parkfield earthquake in 1966 and San Fernando earthquake in 1971, various aspects of near-fault ground motions have been clarified and the effect of near-fault ground motions on structural response have been investigated extensively. The fling-step and forward-directivity inputs have been characterized by two or three sinusoidal wavelets. For this class of ground motions, many sophisticated analyses have been conducted from various viewpoints. However, as far as a forced input is employed, both a free-vibration term and a forced-vibration term appear and the closed-form expression of the elastic-plastic response may be difficult. In order to overcome this difficulty, the double impulse has been introduced as a good substitute of the near-fault ground motion and the closed-form expression of the undamped elastic-plastic response of a structure under the critical double impulse has been derived in the previous works.<br>&nbsp;In this paper, the double impulse is introduced again and the closed-form solution of the maximum deformation of the elastic-perfectly plastic single-degree-of-freedom (SDOF) system with viscous damping under the &lsquo;critical double impulse&rsquo; is derived. Because only the free-vibration appears after each impulse of such double impulse, the energy approach plays an important role in the derivation of the closed-form solution of the maximum elastic-plastic response of the SDOF system with viscous damping. However, it is difficult to treat exactly both of hysteretic damping and viscous damping even in the theory using double impulse. The quadratic-function approximation for the damping force-deformation relationship and the assumption that the critical timing of the second impulse is characterized by the stage of the zero restoring force after the first impulse are introduced to derive the maximum elastic-plastic response with viscous damping by using the energy balance formulation.<br>&nbsp;The validity of the proposed theory using the quadratic-function approximation and the assumption of the critical impulse timing has been investigated through the comparison with the critical elastic-plastic response under double impulse using the time history response analysis. The validity of the proposed closed-form solution has also been demonstrated through the comparison with the response analysis to the corresponding one-cycle sinusoidal input as a representative of the fling-step near-fault ground motion. Furthermore, in order to investigate the applicability of the proposed theory to actual recorded ground motions, two recorded ground motions have been taken into account. It has been demonstrated that the maximum response to the critical double impulse and the response to the selected ground motion coincide fairly well. This supports the validity of the proposed theory.

著者

小島 紘太郎 竹脇 出

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.81, no.726, pp.1209-1219, 2016

被引用文献数

15

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&nbsp;The near-fault ground motions have special characters and the effects of such near-fault ground motions on structural response have been investigated extensively so far. The fling-step (fault-parallel) and forward-directivity (fault normal) inputs have been characterized simply by two or three wavelets. For this class of ground motions, many sophisticated analyses have been conducted from various viewpoints. However, as far as a forced input is employed, both a free-vibration term and a forced-vibration term appear and the closed-form expression of the elastic-plastic response may be difficult. In order to overcome this difficulty, the double impulse input is used as a good substitute of the near-fault ground motion and the closed-form expression is derived of the bilinear elastic-plastic critical response of a structure under this double input.<br>&nbsp;For guaranteeing the equivalence of the double impulse and the corresponding one-cycle sinusoidal input as a substitute of a near-fault ground motion, the equivalence of the maximum Fourier amplitudes of both inputs is introduced together with the equivalence of input frequency. Because only the free-vibration appears after each impulse of such double impulse input, the energy balance formulation using the kinetic energy and the strain and dissipated energy leads to the derivation of the closed-form expression of a complicated bilinear elastic-plastic response. It is shown that the maximum inelastic deformation of a structure with a positive post-yield stiffness can occur after the second impulse different from the case for elastic-perfectly plastic models. Furthermore it is made clear that, as the positive post-yield stiffness becomes larger, the correspondence between the double impulse and the corresponding sinusoidal input becomes better.<br>&nbsp;The closed-form expression is also derived for the non-critical case. The introduction of the concept of critical excitation enabled this derivation of the closed-form expression of the maximum elastic-plastic response. The validity and accuracy of the proposed theory are investigated through the comparison with the response analysis to the corresponding one-cycle sinusoidal input and recorded ground motions (Imperial Valley 1979, Northridge 1994, Hyogoken-Nanbu 1995). It is demonstrated that the proposed method using the double impulse is applicable to actual recorded pulse-type ground motions within a reasonable accuracy.