A supplemental seismic design procedure for US-Code conforming RC moment frames constructed with masonry infills | |
| Author | Matrin Suthasit |
| Call Number | AIT Diss. no.ST-19-01 |
| Subject(s) | Earthquake resistant construction Buildings--Earthquake effects--Evaluation |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Structural Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ST-19-01 |
| Abstract | US-code conforming RC moment frames infilled by masonry walls constitute a distinct class of building structures. This type of structures is of widespread use in many seismic prone areas, especially those in Asian and European countries. Based on numerous researches carried out by earthquake engineering community, there is a general consensus that the presence of infills can alter the dynamic characteristics and lateral load resisting mechanism of bare frames to a large extent. Considering seismic performance, the alteration of infills may either result in overall beneficial or adverse effects depending on numerous factors such as intensity level of ground motions, the code to which frame members are designed to conform, mechanical properties of local masonry materials, and etc. Despite of such knowledge, the current building design practice of many countries still entirely ignore the presence of infills, most likely because relevant seismic codes/standards are almost silent on this issue. In the present study, a comprehensive numerical experiment is performed with twofold objectives: it is firstly aimed to investigate potential effects of infills on the seismic behavior of US-code conforming RC moment frames, and secondly is to formulate a supplemental design procedure for counteracting detrimental effects of infills. In the numerical experiment, nonlinear structural modeling technique adopted is extensively verified against existing experimental testing results. Subsequently, nonlinear structural models are constructed to represent a wide variety of case study buildings. By subjecting these models to pushover and nonlinear dynamic analysis, it is revealed that the presence of infills causes two major opposing effects on the code-intended system behavior: (1) the system deformability is reduced because infills resist the spread of inelasticity along the building height and (2) the roof drift demand is reduced because infills stiffen and strengthen the lateral force resisting system. When the former effect prevails, infilled RC frames analyzed are found to exhibit inferior seismic performance relative to their bare frame counterparts, and vice versa. This finding leads to a conclusion that it is not always conservative to disregard influence of infills in the seismic design. Recognizing that the seismic performance of RC moment frames can be degraded due to the presence of infills, a design-oriented method for assessing the severity of such degradation is developed. This method allows structural designers to evaluate whether infilled frame being considered would perform satisfactorily under MCER shaking level (seismic performance satisfaction is judged on the basis of interstory drift limit). If infilled frame being considered is expected to poorly perform, another design method proposed in this study can be employed. This method, which is formulated on the basis of capacity design principle, provides seismic design demands for columns. Since these seismic design demands are generally higher than those provided by the US code, the columns of infilled frame being designed would become relatively stronger. The intention of applying higher seismic design demands is to provide greater ability of infilled frame to spread inelasticity upward the building height and, thus, to enhance system deformability. By using this newly developed method, the previously analyzed case study buildings are redesigned and subjected to the same analyses. It is found that the proposed procedure is effective in mitigating the adverse effect of infills. |
| Year | 2019 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ST-19-01 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| 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) | Anwar, Naveed;Punchet Thammarak;Sutat Leelataviwat;Nakano, Yoshiaki; |
| Scholarship Donor(s) | Royal Thai Government;Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2019 |