| Author | Sia, Pie King |
| Call Number | AIT Thesis no.ST-94-24 |
| Subject(s) | Structural dynamics
|
| Note | A Thesis submitted in partial fulfilment of the requirements for
the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Ideally, TV-tower with perfect axisymmetry cross-section will exhibit planar
motion when subjected to planar excitation. In reality, large displacement and some
degrees of imperfection may induce nonplanar motion on the structural systems. Based
on continuum mechanic and the concept of generalized coordinates, finite deformation
and imperfection effects are incorporated into the governing equations of motion by using
the principle of virtual work. Modal analyses are employed to obtain the decoupled
equations of motion. From these uncoupled equations, we found that the imperfection
effects will be significant when two orthogonal modes have closely spaced natural
frequencies. In addition, after conducting order analysis, nonlinear coupling terms due to
the finite deformation are neglected. Therefore, in the present dissertation we focus on
the imperfection effect of the TV-tower.
Since it is difficult to predict the vibration characteristics of the imperfect
structural systems, thus the experimental studies were necessary to carry out for further
investigation. A scaled TV-tower was constructed for the shaking table test. Both
preliminary and comprehensive harmonic tests were conducted. Of particular interest,
steady state response of in-plane and out-of-plane motions was measured to identify the
imperfection coefficients and damping ratios. Consequently, the obtained experimental
results were compared qualitatively with the theoretical results, and very good
agreements were found between both.
Furthermore, earthquake excitation tests were carried out to verify the calibrated
analytical model. The time histories of the earthquake response were measured and
compared with those predicted from the calibrated analytical model. From time histories
of the in-plane motion, fairly good agreements were found between the theoretical
predictions and the experimental results especially for the earthquake contain low
frequency components; but some discrepancies were found in the out-of-plane motion.
Both in-plane and out-of-plane motions from earthquake contain high frequency
components were found to have significant discrepancies between theoretical predictions
and experimental results. Finally, we can conclude that the higher modes must be
considered in analytical model in order to predict more accurate earthquake responses.
The present study is believed to provide essential background for further
research of the imperfection effects on structural systems. Moreover, the experimental
studies on scaled TV-tower also give more physical insight various response
characteristics of imperfect structures. |
| Year | 1994 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai |
| Examination Committee(s) | Worsak Kanok-Nukulchai ;Karasudhi, Pisidhi ;Jiaru, Qian
|
| Scholarship Donor(s) | Japanese Government |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1994 |