Location of Semi-Rigid Connection Effect On The Seismic Performance of Steel Frame Structures

In design steel frames, combining semi-rigid and rigid connections can result in better structural performance, particularly in seismic locations. In this study, the effects of semi-rigid beam-to-column connections located on the seismic performance of steel frame structures are investigated. The analysis uses six and twelve-story moment resisting steel frames (MRSF) with rigid, semi-rigid, and dual beam-column connections. These frames are designed according to the Egyptian design codes. Drain-2Dx computer program and seven earthquake ground motions are used in the non-linear dynamic analysis. The rotational stiffness of beam-to-column connections is indicated through the end fixity factors with a value equal to 0.6. The performances of these frames are evaluated through the roof drift ratio (RDR), the maximum story drift ratios (SDR), and the maximum column axial compression force (MACF). The results indicated that the quantities of fundamental periods, roof drift ratio, the story drift ratio, and the column axial compression force are related to stiffness, rigidity, and the number of semi-rigid connections in steel frames.

Improving the robustness of steel frame structures under localised fire conditions

PurposeThe robustness of building structures in a fire has recently drawn wide attention. This study presents the progressive collapse analysis of steel frame building structures under localised fire. The main objective of this study is to propose methods to enhance the structural collapse resistance of such structures in fire.Design/methodology/approachA modelling method was developed and validated against both experimental and analytical studies. Then, a series of robustness analyses were performed to investigate the interaction among the members and the pattern of load distribution within the structures. These analyses show that lateral resistance and load redistribution have a vital role in the robustness of the building. Thus, two approaches have been adopted to enhance the robustness of the focused steel frame during a fire.FindingsIt is found that increased size of floor beams and vertical bracing systems are effective measures in preventing whole structure collapse. The larger beam section is able to prevent catenary action so that the load in the failed columns can safely transfer to the adjacent columns without buckling. On the other hand, the bracing system improves the lateral resistance that can accommodate the lateral force when catenary action occurs in the beam.Originality/valuePrevious studies have focused on the collapse mechanism of steel frame structures. However, the parameters affecting the structural robustness in a fire have not yet been explored. To address this gap, this study adopted numerical modelling to undertake parametric studies to identify effective methods to improve the robustness of such structures under fire conditions.

Optimization of concentrically braced steel frame structures based on SNI 1726:2019, SNI 1727:2020, SNI 1729:2020, and AISC 341-16

Damages resulted from earthquakes are a loss in the economic sector. The structure of multi-story buildings needs an earthquake-proof design with higher performance to reduce such losses. By utilizing the metaheuristic algorithm, this study aims to identify the most compatible brace configuration and profile used in a concentrically braced steel frame structures with minimal total weight and that will meet the safety requirements. This algorithm is suitable owing to the fact that it is able to find solutions to any known optimization problem either through Particle Swarm Optimization (PSO), Symbiotic Organisms Search (SOS), or Differential Evolution (DE). The performance of these algorithms will demonstrated in a form of comparison through a case study of optimizing a 5-span, 6-story steel frame structure. These systems will determine the lightest frame weight, which also correlates to a lower construction cost, without compromising the constraints of SNI 1726:2019, SNI 1727:2020, SNI 1729:2020, and AISC 341-16. Based on the results of data processing, SOS is shown to achieve the highest algorithm performance compared to PSO and DE.

Theoretical and Experimental Study of the Pounding Response for Adjacent Inelastic MDOF Structures Based on Dimensional Analysis

Dimensional analysis is applied to study the pounding response of two inelastic multidegree of freedom (MDOF) structures under simplified earthquake excitation. The forces and deformations of the collision processes are simulated by adopting the improved Kelvin pounding model. The inelastic characteristics of MDOF structures are described by the bilinear interstory resistance model, and the representations of dimensionless impact force and the dimensionless motion equation in the pounding process are derived. On the basis of the above-mentioned theoretical deduction, the superiority of the improved Kelvin model is verified by comparing the impact response of the improved Kelvin model and the Kelvin model. Finally, the validity of the proposed theoretical method is further proved by the comparison between results from the shaking table tests of adjacent four-story and three-story steel frame structures and the corresponding numerical results obtained by the MATLAB program.