## 4 A Progressive Chronicle of Masonry Provisions in Turkish Earthquake Codes (1940-2018)  
The discussion of damage mechanisms presented earlier primarily pertains to structures that have not been designed or constructed in alignment with seismic regulations. However, this circumstance does not lessen the importance of examining the TBEC (2018) [13]. Instead, the significance of delineating TBEC (2018) [13] provisions lies in providing a regulatory framework that allows for a critical evaluation of the identified shortcomings of construction practices. This section aims to emphasize the contrast between the established seismic safety regulations and the prevalent informal, occupant-led construction methods observed in the rural and peri-urban areas of eastern Turkiye. The analysis of recurring structural failures, such as the lack of ring beams, the use of inferior mortar, and excessive wall slenderness, can be elucidated by assessing how these practices diverge from the standards set forth in the TBEC (2018) [13]. By engaging in this examination, the analysis makes clear that the pervasive vulnerability of masonry buildings is not merely a consequence of the absence of regulation, but instead a result of inadequate incorporation, execution, and enforcement of the existing standards within informal construction practices. Earthquake design standards of Turkiye have been impacted by several seismic events and technical advances over many decades, resulting in a sequence of codes produced from 1940 to 2018. Turkish seismic rules have changed significantly in conceptual underpinnings and prescriptive criteria, particularly for masonry, from the basic principles of the 1940s to the TBEC (2018) [13]. The rules set in 1944 [47], 1949 [48], and 1953 [49] mostly repeated the 1940 standards, although they clarified mortar strength, stone measurements, and the importance of using local resources. By 1961 [50], multi-story masonry was explicitly recognized, but it still lacked quantitative standards for wall slenderness or ring beams. In reaction to earthquakes like the 1971 Bingol disaster, the 1975 [51] code stressed ring beams (hatl) as a key approach to prevent out-of-plane failures, but did not impose them outside urban areas. The 1992 Erzincan earthquake and the recognition that occupant-driven expansions often circumvented structural regulation led the code to set stricter numerical limits on story height-to-thickness ratios and partial restrictions on earthen mortar by 1997 [52; 53]. Inspired by research from the 1999 Kocaeli earthquake, the 2007 [54] code mandated the use of ring beams in areas of moderate-to-high seismic activity and introduced preliminary capacity-based methods for the construction of reinforced or partially confined masonry. The TBEC (2018) [13] replaced zone-based hazard classifications with spectral acceleration maps, created explicit performance objectives (such as \"Limited Damage\" and \"Collapse Prevention\"), and required multi-story masonry structures to have continuous ring beams and tie columns. Occupant-driven extensions are still unclear in the 2018 [13] code, allowing many rural or informal masonry additions to occur without code enforce ment. Even as it struggles to reconcile code theory with practical application on-site, the Turkish regulatory framework for masonry has gradually evolved from basic prescriptive directives to comprehensive numerical constraints and performance-oriented principles. Table 1 summarizes how key regulatory deficiencies in past Turkish seismic codes have directly contributed to observed failure mechanisms in the field, highlighting the practical implications of these gaps for URM construction. The 2018 version delineates four degrees of seismic ground motion: DD-1, DD-2, DD-3, and DD-4. These values correspond to earthquakes with probabilities of exceedance of 2%, 10%, 50%, and 68% over a 50-year return period.