| Author | Phaiboon Panyakapo |
| Call Number | AIT Diss. no. ST-99-02 |
| Subject(s) | Earthquake resistant design
|
| Note | A dissertation submitted in paiiial fulfillment of the requirements for the degree of Doctor of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ST-99-02 |
| Abstract | The conventional seismic design approach that is based on the well-known concept of 'constant ductility' is extensively investigated for its validity. The investigation is primarily based on a simplified design-and-evaluation approach. In this approach, a designed structure is assumed to behave like a single-degree-of-freedom, inelastic inverted pendulum system, and its yield strength is assumed to be exactly equal to the mean strength demand for a target ductility ratio. More than 130 earthquake ground motions recorded on rock sites, alluvium sites, and soft soil sites are employed for the computation of site-dependent mean strength demand spectra used in this design-and-evaluation approach. The ductility capacity of the designed structure is assumed to match the minimum ductility performance described in the New Zealand .code. The response of the designed structure to each of the selected ground motions is computed, and seismic damage is estimated by the Park-Ang damage model. This design-and-evaluation process is repeated for structures with different natural periods, for different levels of ductility ratio used in the design, for different structural hysteretic behaviors, and for three different site conditions. The results are presented in the form of damage spectra. The conventional design approach is considered valid if most of the designed structures can withstand various ea1thquake ground motions without excessive damage. The obtained results for structures with either bilinear or elastic-perfectly-plastic behavior located on rock or alluvium sites indicate that the conventional design approach is valid. In contrast, the conventional design approach is found to be invalid for the case of soft soil site condition due to excessively high seismic damage. This is mainly caused by relatively high cumulative damage resulting from repeated inelastic response cycles, which is found to be associated with the long-duration and narrowband random characteristics of ground motions recorded on soft soils. For the case of structures with hysteretic behavior described by Clough, Modified Takeda or Park's general three parameter model, the conventional design approach is found to be invalid for every site condition. This is due to the high seismic damage which is primarily caused by cumulative damage contributed from a large number of small-amplitude response cycles. To improve the design approach, a new type of design spectra that is based on a concept of 'constant damage' is proposed; the spectra are called constant-damage strength demand spectra. A structure designed based on the new spectra will be guaranteed to have its seismic damage bounded at an acceptable level. The validity of the proposed spectra is also checked and found to be satisfactory. Therefore, it is believed that the constant-damage design spectra can be adopted as a reliable basis for the development of future seismic resistant design codes. |
| Year | 1999 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ST-99-02 |
| Type | Dissertation |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai; |
| Examination Committee(s) | Worsak Kanok-Nukulchai ;Wijeyewickrema Anil C. ;Noppadol Pienwej; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology |