Introduction
Since Iran is one of the earthquake-prone countries and, unfortunately, has suffered high casualties by earthquakes, the retrofitting of buildings in Iran is a fundamental necessity. According to records, major earthquakes in Iran occur every five years on average, resulting in significant human and financial losses. Increasing knowledge of seismic activity, public education, promoting safety culture, and assessing the vulnerability of strategic buildings are effective in reducing financial and human casualties from earthquakes.
The primary standard for reducing earthquake risks is the seismic design code applied in the design and construction phases. The regulations specify seismic design levels and performance criteria for buildings under expected ground motions, aiming to prevent life loss and minimize the direct and indirect economic and social consequences. However, some designed structures can still be vulnerable to specific seismic forces. The necessity of retrofitting a building or structure is not solely dependent on its age; there are cases where buildings undergo retrofitting even before they are put into operation. This is more important in big cities with high population density, where the likelihood of casualties and financial loss during an earthquake increases.
Most of previous studies in the field of seismic retrofitting and strengthening in Iran have focused on various methods to improve the seismic behavior of buildings. However, the challenges of implementing these methods and their acceptance by those involved in the construction industry have been neglected. In this regard, this research examines the perspectives of responsible officials in renovation and seismic retrofitting projects, contractors, and stakeholders regarding the existing challenges in retrofitting buildings in East Azerbaijan province, Iran. We seek to identify the factors affecting the implementation of building retrofitting projects.

Methods
This is a descriptive survey study. After familiarization with the execution process of building retrofitting projects and identifying the challenges based on the opinions of 5 experts from the organization for development, renovation and equipping of schools (DRES) of Iran, the identified items (n=30) were used in designing a questionnaire. The questionnaire was then completed by 6 technical experts, 15 project supervisors, and 23 contractors in East Azerbaijan province to determine the main issues that require attention for the successful implementation of retrofitting projects. Finally, practical solutions for each challenge were provided to address the barriers to retrofitting projects in East Azerbaijan province.

Results
According to technical experts, “inappropriate allocation of budgets” was deemed the most significant challenge (54.5). According to the contractors, “delays in payments and getting involved in administrative processes” was the most important challenge [87]. According to the project supervisors, “the lack of skilled and experienced contractors in specialized projects” was the most important one [85]. The “lack of a specialized cost list” was another important matter that seems to cause many financial disagreements in retrofitting projects.
The proposed solutions included the establishment of transparent budget allocation processes, the formation of groups for developing detailed specialized cost lists, the streamlining of project handover procedures, the improvement of workshop facilities, and the implementation of robust project coordination frameworks. 

Conclusion
This study unveils the key challenges in building retrofitting projects in East Azerbaijan province, Iran, and offers practical solutions to enhance the implementation of these projects. The findings can be valuable for project managers, policymakers, and stakeholders involved in construction projects. 

Ethical Considerations
Compliance with ethical guidelines
All participants in this study have become aware of the research process, the confidentiality of their information, the right to withdraw from the research at any time, and how the research findings will be published.

Funding
The paper was extracted from the master thesis of  Behroz Khalili, approved by University of Bonab, Bonab, Iran.

Authors' contributions
Conceptualization: Somayeh Mollaei; Methodology: Behroz Khalili and Somayeh Mollaei; Investigation: Behroz Khalili; Software and data collection: Behroz Khalili and Somayeh Mollaei; Writing the original draft: Milad Khezri and Somayeh Mollaei; Writing review and editing: Mehdi Babaei and Milad Khezri.

Conflicts of interest
The authors declared no conflict of interest.


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