7 results for Pan, T.C.

  • Structural Response to High Frequency and Short Duration Impulsive Ground Motions

    Dhakal, R.P.; Pan, T.C.; Lan, S. (2001)

    Conference Contributions - Other
    University of Canterbury Library

    This paper presents a conceptual discussion on structural response to high frequency and short duration impulsive ground motion based on numerical analysis of a single degree of freedom system subjected to explosion-induced ground motion. Parametric study is performed to investigate the effect of impulse duration to natural period ratio on the maximum response of a single degree of freedom system to different types of impulsive loadings. As the loading duration of explosion-induced ground motion is smaller than half of the natural period of most civil engineering structures, maximum displacement response to underground explosion increases with the increase in total impulse, and it generally occurs in the free vibration phase. It is, therefore, necessary to consider longer time domain than the loading duration in the analytical prediction of structural damage due to high frequency and short duration loading. Numerical analyses are carried out on single degree of freedom systems with different natural periods to simulate and investigate the contribution of vibration modes on the overall displacement, velocity and acceleration responses. High frequency vibration modes, which are activated within the forced vibration phase, cause smaller displacement and larger acceleration response. However, free-vibration response is dominated by lower frequency fundamental mode that yields larger displacement and smaller acceleration response. Hence, structures are more likely to undergo displacement-induced damage in the free vibration phase, but relatively larger inertia force due primarily to high acceleration might be detrimental in the forced vibration phase.

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  • Characteristics of Structural Response to Ground Shocks

    Dhakal, R.P.; Pan, T.C. (2002)

    Conference Contributions - Published
    University of Canterbury Library

    This paper presents a conceptual discussion on structural response to ground shocks. Numerical parametric analyses are performed on a simplified linear structural model to investigate the special features of structural response brought by short duration, large amplitude and high frequency excitations, which are the basic characteristics of ground shocks induced by blasting. Nonlinear FEM analyses on a 2-storey RC frame subjected to ground shocks are carried out to qualitatively understand building response to blasting. This study shows that maximum structural response to blasting depends primarily on the amount of impulse, and it generally occurs after the major ground shock has ceased. To capture the maximum response, it is hence necessary to consider additional time duration beyond ground shock period in blasting analysis. It is found that the response in the forced-vibration phase includes high frequency vibration modes with small displacement but large acceleration, thus inducing high inertial shear force. However, the free-vibration response is dominated by lower frequency modes with larger displacement but smaller acceleration. Hence, buildings subjected to strong ground shocks might experience sudden shear failure of its components. Nevertheless, if a building strength is enough to avoid shear failure during the major shock, it may be damaged after the ground shock, and the extent of damage depends on the ground shock magnitude.

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  • Qualitative Assessment of Structural Damage due to Underground Explosion

    Dhakal, R.P.; Pan, T.C.; Lan, S. (2001)


    University of Canterbury Library

    This paper investigates numerically the response of a reinforced concrete frame to explosion-induced ground motions simulated at different distances from the explosion source. The results indicate that nearby structures might experience sudden shear failure and distant structures might undergo less severe damage due to high frequency response that causes larger strain in spite of smaller displacement.

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  • Joint Contribution to the Deformation of RC Beam-Column Sub-Assemblies

    Dhakal, R.P.; Pan, T.C. (2004)


    University of Canterbury Library

    In this paper, the contribution of joint shear deformation to the overall storey-drift of reinforced concrete (RC) beam-column sub-assemblies is investigated experimentally. Two lightly reinforced beamcolumn sub-assemblies, one without any hoops inside the joint core and the other with hoops significantly less than that required by the incumbent seismic design codes, were tested under a constant axial compression and gradually increasing reversed cyclic displacements. Both specimens experienced severe damage in the joint due to excessive shear deformation of the joint core. Unlike in seismically designed ductile frames, joint shear deformation accounted for more than 50% of the overall storey-drift in the tested specimens. Comparison of the two test results showed that a small amount of hoops in the joint core, though not enough to satisfy seismic requirements, helps to confine the joint core and to inhibit the joint shear deformation to some extent.

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  • Response of non-seismic RC frames to high-speed excitations

    Dhakal, R.P.; Pan, T.C. (2005)

    Conference Contributions - Published
    University of Canterbury Library

    The main aim of this study is to investigate the factors governing the post -peak cyclic response of laterally loaded reinforced concrete cantilever columns. A series of experiments are conducted, in which five reinforced concrete columns are subjected to cyclic lateral displacement. Much attention is paid to cover concrete spalling and the large lateral displacement of reinforcement. Specimens are designed so that the buckling of reinforcement and cover concrete spalling can be clearly observed. Finite element analyses are also performed using enhanced nonlinear fiber models, which are verified in member level by comparing with experimental results.

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  • Characteristics of High-Speed Cyclic Test of Beam-Column Joints

    Dhakal, R.P.; Pan, T.C. (2003)

    Journal Articles
    University of Canterbury Library

    The detailed procedures for high-speed cyclic loading test and the authors’ first-hand experience during the tests of reinforced concrete beam-column connections subjected to cyclic displacements at frequencies as high as 20 Hz is documented in this paper. It is found necessary to give special attention to the quality of the instruments to successfully perform high-speed data acquisition. Problems faced in different phases of the high-speed tests that are not common in pseudo-dynamic tests are highlighted. The applicability of some basic criteria established for quasi-static and seismic performance in gauging the high-speed dynamic performance is also discussed. Unlike in pseudo-dynamic tests, the inertia force contributed significantly to the readings of load cells integrated with the actuators that apply the high-speed displacement cycles. The shear capacity of the tested joints was higher than that computed with the empirical equation in seismic design codes.

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  • Experimental study on the dynamic response of gravity-designed reinforced concrete connections

    Dhakal, R.P.; Pan, T.C.; Irawan, P.; Tsai, K.C.; Lin, K.C.; Chen, C.H. (2005)

    Journal Articles
    University of Canterbury Library

    This paper reports an experimental program aiming to shed some light on the response of non-seismic RC beam-column joints to excitations of different frequencies. The RC connections tested were designed only for gravity loads, thus rendering the joint cores weaker than the adjoining members when subjected to a lateral load. Altogether, six tests were conducted on full-scale specimens, which were subjected to reversed cyclic displacements applied at different speeds varying from slow quasi-static loading to high-speed dynamic loading as fast as 20 Hz. Although all specimens expectedly suffered joint shear failure, the maximum joint shear stresses observed in the tested specimens, despite lacking transverse hoops inside the joint cores, were more than the horizontal shear stresses allowed in ductile RC joints with the same grade of concrete according to the existing seismic design codes. The damage patterns and failures of the specimens showed a better correlation with the residual storey shear stiffness rather than with the loss of storey shear strength during the repeated cycles. By analysing the test results, this paper also discusses how an inadvertent inertial force develops during high-speed displacement reversals.

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