Citation: Lotfy, S.; Mortagi, M.; El Madawy, M.E. Variable Factors Affecting Progressive Destruction of Composite Steel Tall Building. Buildings 2022, 12, 1704. https:// doi.org/10.3390/buildings12101704 Academic Editors: Hezi Grisaro and Sam Rigby Received: 26 September 2022 Accepted: 13 October 2022 Published: 16 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). buildings Article Variable Factors Affecting Progressive Destruction of Composite Steel Tall Building Sameh Lotfy 1 , Mohamed Mortagi 2, * and Mohamed E. El Madawy 2 1 Civil Engineering Department, MISR Higher Institute for Engineering and Technology, Mansoura 7651012, Dakahlia Governorate, Egypt 2 Department of Structural Engineering, Faculty of Engineering, Mansoura University, Mansoura 35516, Dakahlia Governorate, Egypt * Correspondence: eng_mortagy@mans.edu.eg Abstract: In recent years, the presence of progressive collapse in tall buildings induced a catastrophic event which attracted the majority of the community’s attention. The purpose of this paper is to develop a 3D numerical analysis of tall building under column loss. A composite steel frame building with 25 stories with five spans in both directions is proposed. The building has 3 m story height and 8 m span in both directions. The building is designed through the commercial software SAP2000 software against wind loads based on Eurocode 1-2005. The focus here is to investigate various parametric studies under abrupt column loss of multi-story composite building. The effect of composite slab is considered with full composite action between beam and slab. The findings of a parametric formulation incorporating important parameters for the progressive collapse design technique are given and confirmed using nonlinear dynamic time history analyses. The assessment of results has been introduced based on deformation, axial force in columns, equivalent plastic strain, major moment and axial force in the considered beams above the column loss. Next, a probabilistic analysis has been performed to assess the behavior of composite steel buildings against column loss. The study investigates the critical column loss and pinpoints the location of the next critical column. The results show that the concrete grade, position of the removed column, beams cross-section, and place of bracings have a significant effect in the response of the building rather than the steel grade and bottom reinforcement density. The removal of exterior column has the significant increase of the axial force percentage by 111.4% for the corner column. The corner column removal gives the maximum equivalent plastic strain with a value of 0.00449. Furthermore, the results reveal the potential impact of uncertainty on the structural elements of the considered buildings through the progressive collapse analysis. The vertical displacement above the column is fitted with mean value of 0.0251387 m and with a coefficient of variation 0.01664. Keywords: progressive collapse; uncertainty; tall building; finite element; modelling; parametric study 1. Introduction Progressive collapse has received a lot of attention in recent years after the catastrophic events affiliate the partial collapse of Ronan Point [1], the Murrah Federal Building [2] and the total collapse of the World Trade Center [3]. Progressive collapse is described as the failure of a main vertical element of a structure, which may lead to the failure of adjoining elements and, as a result, the partial or whole collapse of the building occurs [4]. This phenomenon has been produced by additional abnormal loads which are not considered in the design process. These loads are categorized as pressure or impact loads (gas explosions, blast, wind, environmental, aircraft impact, hazardous materials, earthquakes, and fire). Three conditions must be realized in the propagation of progressive collapse: the local failure of an element, the spreading of failure to the other elements, and the final collapse Buildings 2022, 12, 1704. https://doi.org/10.3390/buildings12101704 https://www.mdpi.com/journal/buildings