## 1 Introduction  
Although the concept of a special moment frame (SMF) is a relatively recent development in international building codes, steel moment-resisting frames have been applied for over a hundred years in construction [1]. In recent decades, the structural methods for calculating and constructing these steel structures have been constantly updated to meet the needs and challenges generated by new projects [2; 3]. Therefore, building codes, such as AISC 360-16 [4], AISC 341-16 [5], and AISC 358-16 [6], have adopted a design philosophy aimed at providing greater safety to avoid collapse induced by earthquakes of different magnitudes. Diaphragm connections are also often used in SMF to ensure structural safety [7; 8; 9]. In this context, regulations such as AISC-358 [6] include several pre-qualified connections. When a connection is not prequalified, specific tests are required and it must pass the seismic design criteria for SMF buildings, specified in AISC 341 [5], including connections with external diaphragms. [PERSON] et al. [10] analyzed the seismic behavior of a joint composed of steel beams and steel-reinforced concrete columns (MPCJ). These authors studied three types of connections: bolted, welded, and bolted-welded beam-column. The connections were subjected to a low cycle with inverse load, to investigate the elastic-elastoplastic development, the failure characteristics, and the seismic response. Results showed bending failure at the end of the beam following the buckling of the flange connection plate. The research found stable hysteretic curves, strength and stiffness degradation, good ductility, and energy dissipation performance. Today, in civil construction, the demand for special moment frames is greater, due to their good dissipation response to seismic events and their versatility in complex applications. The foundation systems become more economical with these frames because they impose smaller forces on the foundation [7; 8; 11]. SMFs comprise three basic elements: beams, columns, and beam-column connections. Concrete-filled tubular Steel Columns (CFSTC) are widely used in complex architectural proposals for their load-bearing capacity under several conditions [12]. CFSTCs and steel-reinforced concrete columns are extensively used in current steel-structure residential projects [13; 14], combining the respective advantages of concrete and steel. Many in-depth studies on these structures have been conducted [15; 16]. In [17] it is reported on experimental and finite element research of three full-scale Wall Concrete-Filled Steel Tubular Columns (WCFSTCs). Studies have established that this structure exhibits an attractive energy dissipation capacity and beneficial seismic performance. Due to their geometry, structural tubular or hollow section profiles are currently one of the most effective in terms of resistance to axial compression load. Among the advantages of such structures are larger radii of gyration compared to open profiles of similar dimensions, ease of production, adequate design versatility, and a greater polar moment of inertia. However, in the Ecuadorian construction sector, these do not comply with the corresponding regulations, which puts the safety and stability of the structures at risk. In Ecuador, steel constructions are increasingly common in buildings for different purposes: housing, shopping centres, etc., however, these present fillet welds that do not adequately conform to the recommendations to generate rigidity (consult, for example, in [[http://biblioteca2.ucab.edu.ve/anexos/biblioteca/marc/texto/AAT6499.pdf](http://biblioteca2.ucab.edu.ve/anexos/biblioteca/marc/texto/AAT6499.pdf)]([http://biblioteca2.ucab.edu.ve/anexos/biblioteca/marc/texto/AAT6499.pdf](http://biblioteca2.ucab.edu.ve/anexos/biblioteca/marc/texto/AAT6499.pdf)) (accessed on January 2024)).