Concrete-filled steel tube (CFT) has gained popularity in the building industry in recent years due to its unique static and earthquake resistance features. The interaction between steel tube and concrete provides the most benefits such as: the occurrence of local buckling of steel tube is delayed by the restraint of concrete, and the strength of concrete is boosted by the confining effect supplied by the steel tube. Hence, in the present study a mild steel-encased portal frame that employs shear connections inside the frame to increase ductility and ultimate load bearing capacity was studied. The ultimate load bearing capacity of the concrete-filled mild steel tube (CFT) frame structure was determined experimentally. During the horizontal cycle load testing of the portal structure, an axial force was applied. The material used was 1.2mm thick mild steel plates that are used in different widths. The concrete used was M25-grade. The specimens have shear connections that distribute shear, causing the two elements to work together as a unit was provided with spacing varied such as 75mm, 100mm, and 125mm, and they were evaluated at a pace of 0.1 tons per cycle. The shear connector section's strength and stiffness can be improved without the need of additional steel. All the loads versus axial elongation were investigated by drawing hysteresis curve. In comparison to standard concrete, it was observed that CFT supports had greater rigidity, ductility factor and ultimate load bearing capacity. Shear connections can greatly improve the specimen's total strength and load-carrying capacity.