Tubular structures are extensively recognized as a high efficiency and economically reasonable structural system for the design and construction of skyscrapers. The periphery of the building plan in a tubular system consists of closely spaced columns connected by circumferential deep spandrels. When a cantilever tube is subjected to a lateral load, it is expected that the axial stress in each column located in the flange frame of the tube is the same, but because of the flexibility of peripheral beams, the axial stress in the corner columns and middle columns is distributed unequally. This anomaly is called “shear lag”, and it is a leading cause of the reduction in efficiency of the structure. In this paper, the possible relation between shear lag and the type of lateral load subjected to these systems is investigated. The above relation is not yet considered in previous literatures. Three various plan shapes including rectangular, triangular and hexagon were modeled, analyzed, designed and subjected to the earthquake and wind load, separately. Further work is carried out to compare the shear lag factor of these structures with distinct plan shapes against different types of lateral load. It is observed that all types of structures with various plan geometry subjected to the wind load had a greater amount of shear lag factor in comparison with structures subjected to the static and dynamic earthquake loads. In addition, shear lag in structures with the hexagon shaped plan was at the minimum.

Reinforced concrete short corbels are widely used in engineering structures, such as bridges and precast structures. Therefore, the present comparative study was conducted on the structural behavior of the reinforced concrete corbels strengthened with carbon fiber-reinforced polymer (CFRP) laminates. For this purpose, numerical analysis was done using the finite element method. Therefore, nine models consisting of eight corbels strengthened with different CFRP arrangements in addition to an unstrengthened model were studied. The maximum load capacity, stiffness, ductility, and amount of absorbed energy were compared. In one of the above structure models, an innovative hunch was added at the top side of the corbel to column connection to investigate the differences with ordinary types of connections. Results revealed that the model used three bonded CFRP laminates all around the column and outside edges showed an 81% increase in loading capacity. Moreover, the corbel equipped with hunches had an 8% increase in stiffness compared to an ordinary corbel.