"Thesis" and "dissertation" are used interchangeably, but in architecture, a "dissertation" refers to the textual work, whereas a "thesis" consists of both the dissertation and the design proposal, drawings and models.
The hardcopy of ALL dissertations by SDE students can be found at IRC. If you are searching for a dissertation in Central Library that is older than 2002, use the call no. NA25 and limit your search to Theses (NUS) collection only.