Dr. Núñez-Castellanos, Eduardo

This paper presents an experimental research to assess the cyclic behavior of a bolted moment connection with the use of optimized end-plate connected to built-up box column subassemblies subjected to bidirectional and unidirectional loading. Seven real scale specimens were tested: three specimens with four beams connected to column as interior joint, two specimens with two beams connected as corner joint configuration and two specimens with two beams connected to column as interior joint, according the protocol established in AISC Seismic provisions. The seismic performance was evaluated in terms of hysteretic behavior, failure mechanism, stiffness and dissipated energy. The joints studied were manufactured from of hot-rolled I-beams and square built-up box columns. The elements of connection such as bolts, welding, outer stiffeners and end-plates were designed to remain in elastic range from the flexural expected capacity of beams. The results showed that the required minimum moment of 0.8Mp at 0.04 rad of drift angle was achieved for all specimens tested. However, a higher stiffness and resistance was reached in configuration with unidirectional load (interior joint) in comparison to joint subjected to bidirectional load (corner joint). The damage was concentrated uniquely in beams, while an elastic behavior in columns and connection components was reached for 0.04 rad of drift angle. Finally, this moment connection configuration can be used as an alternative to design buildings with special moment frames under bidirectional loading considering the cyclic behavior of joints evaluated.

In this numerical research, the variation of cyclic behavior of beam-to-box column connection was studied. Dimensional and load conditions were parametrically evaluated with the goal of assessing the applicability and use of this biaxial moment connection according to the Seismic Provisions, such as bending strength and rotation capacity, secant and tangent stiffness, dissipated energy and strong column-weak beam relationship. A total of 83 different models of 3D connections were developed using in ANSYS software with the load at the top of the column. Results show a cyclic behavior not controlled by axial load. However, the variations of clear span to depth beam ratio caused degradation of the strength, secant and tangent stiffness as well as in dissipated energy. The 80% of plastic moment of beam and rotation at 4% interstory drift were reached for all models analyzed according to criteria established in AISC 341. Finally, the configurations designed with low levels of axial load are controlled by the design of the web panel zone shear, while configurations designed for high levels of axial load are controlled by the strong column-weak beam criterion.

In this research, the influence of global slenderness and sliding pallets factor on the seismic design of steel storage racks are assessed. Variations in span length, the height of storage levels, live load, and percentage of live load considered in the seismic mass are studied for different levels of seismic zone and soil type. The models were designed according to the Chilean Code NCh2369. Subsequently, a global sensitivity analysis was developed to analyze the influence of each studied parameter in the seismic design response in terms of fundamental period, drift, and base shear from a response spectral analysis approach. A total of 12000 simulations were performed. Two-hundred additional models were performed to evaluate the variation of seismic mass in the structural response. Results indicate a significant influence of live loads and seismic mass on steel racks designed for soft soils and unbrace conditions. The stiffness also modifies the performance of the racks, mainly in models using braces in the down-aisle direction and cross-aisle direction. In these cases, the seismic mass factor does not have a strong influence on structural response in comparison to the global slenderness.