Internal Columns Research Articles

Experimental and numerical evaluation of fibre-reinforced concrete vault forming slabs subjected to low-velocity impact loading

Vaults and dome structures are attractive in architecture due to their ability to evenly distribute weight and support substantial loads without internal columns. Fibre-reinforced concrete is ideal for these compressive structures, which experience low tensile stress. Assessing their performance under impact loading is crucial for safety, financial protection, and preserving cultural heritage. In this study, twelve arch-shaped slabs with thicknesses of 50, 75, and 100 mm, incorporating varying fibre percentages, were tested using a drop-weight impact test machine. Finite element analysis, validated against experimental results, was employed to evaluate the slabs’ behaviour under low-velocity impacts. The analysis revealed multiple flexural cracks in fibre-reinforced specimens, with maximum crack widths decreasing as fibre ratios increased. Although the number of microcracks rose with higher fibre content, crack spacing diminished. Results indicated that adding steel fibres significantly enhances tensile strength and energy absorption—showing a 90% increase in the 100 mm thick dome with 1.5% fibres—while reducing cracking. These improvements contribute to the durability, stability, and safety of concrete domes, lowering maintenance costs. Thus, incorporating steel fibres in the design and construction of impact-resistant concrete domes is highly recommended.

Effects of axial compression ratio on seismic behavior of shallow‐buried rectangular stations: Hybrid simulation and quasi‐static test

AbstractIn the absence of experimental investigations on column members of underground structures, full‐scale column specimens were tested to explore the seismic behavior of shallow‐buried subway stations at various depths. The axial compression ratios of internal column specimens were set as 0.16, 0.33, and 0.40. Both hybrid simulations and quasi‐static tests were performed on the station columns. The hybrid simulations illustrated the drift demands of internal columns, while the load‐carrying capacity and deformation capacity were obtained from the quasi‐static tests. Hybrid simulations at low, moderate, and high‐intensity levels were conducted to study the seismic responses of shallow‐buried rectangular stations. The hybrid simulations suggest that the most severe damage occurred in the station when the axial compression ratio of the tested column reached 0.40. Central columns suffered severe stiffness deterioration under high‐level earthquake excitation, especially in stations at greater depths. Meanwhile, the quasi‐static test results indicate that the ultimate load of the central columns increases with increasing axial compression, but this leads to a significant decrease in the ductility of columns. Besides, the sectional analysis results show that the central columns are prone to tension‐controlled failure, and the safety margin for flexural response deteriorates with an increasing axial compression ratio. The test results indicate that shallow‐buried rectangular stations are susceptible to flexure‐controlled structural failure when their central columns possess a relatively low axial compression ratio and a high shear span‐to‐depth ratio. The failure mechanism of station columns is revealed by both the hybrid simulations and quasi‐static tests, and the findings from the full‐scale tests are beneficial for the practical design of shallow‐buried rectangular stations.

Assessment of mitigation alternatives for differential shortening in high-rise reinforced concrete buildings

Selecting appropriate structural system for reinforced concrete (RC) buildings is essential in the design process to satisfy serviceability and strength requirements. Using ordinary analysis (OA) may result in inaccurate estimation of differential shortenings (DS) between vertical supporting elements which might lead to structural and architectural problems. Efficiency of staged analysis including time-dependent effects (SAT) has been recently recognized for the analysis of these buildings due to considering the sequential nature of construction. In this research, eight RC buildings with heights ranging between 35 and 175 m and various structural systems, namely rigid frames (RF), shear walls (SW), wall frames (WF), and tube in tube (TT), are analyzed. An assessment is conducted for the adequacy of three mitigation alternatives to decrease changes between DS estimated using OA and SAT. In Alternative 1, cross sections of all vertical elements (columns and shear walls) are increased by 50%. Alternative 2 is performed by iteratively proportioning the dimensions of internal columns without changing the cross sections of edge and corner vertical elements. One outrigger system is introduced along the height of buildings with WF and TT systems in Alternative 3. Analysis of the eight buildings is implemented by developing a numerical model considering the construction stages and time-dependent effects. The alternatives assessment is conducted by comparing differential displacements (DD), bending moments, and shearing forces before and after mitigation obtained from OA and SAT. The numerical results showed that Alternative 1 is not efficient in mitigating the differences between the OA and SAT for all the studied buildings. However, an optimum solution can be achieved using the Alternative 2 for all investigated systems. Also, Alternative 3 was found adequate in partially mitigating the differences between the two analyses for the buildings with WF and TT systems.

Punching tests on edge slab-column connections with refined measurements

Due to the significant shear forces developing around columns and the potential brittle failure associated, the punching capacity of flat slabs is the main concern at ultimate limit state. An effective way to understand the behaviour of slab-column connections has typically been by testing isolated specimens in the laboratory. While there exist many slab-column connection types in actual slabs, most research efforts have focused on the punching resistance at internal columns. Specifically, edge connections appear largely underrepresented in the literature when the number of existing tests is compared to their importance in typical building floor configurations. Furthermore, the favourable effect of slab continuity is generally neglected in this type of tests. This paper presents the results of an experimental campaign on two edge slab-column connections: one had no shear reinforcement, while the other had a large amount of shear reinforcement to evaluate maximum punching. A novel test setup was conceived to apply representative boundary conditions of actual continuous slabs, introducing moment continuity perpendicularly to the slab free edge. Refined measurement techniques were extensively used, monitoring the visible slab faces using Digital Image Correlation, and instrumenting the flexural and shear reinforcement with distributed fibre-optic sensors. The failure of the slab-column connection without shear reinforcement was triggered in the region of shear stress concentrations and propagated around the column thereafter. Well-anchored vertical legs of flexural reinforcement at the free face induced a smeared-like shear crack pattern. In the shear-reinforced slab-column connection, an initial crushing of the concrete at the column front corners was followed by the formation of a local yield line along the slab axis. In addition to the enhancement of the resistance and rotation capacity, the shear studs also served for increasing the moment redistribution capacity of the system. The experimental results are compared to different codes of practice, showing that improvements are needed to better assess the resistance of edge columns.

Investigating the seismic performance of MRF-CBF dual systems under the effects of staged construction

In steel structures with moment-resisting frame-concentrically braced frame dual systems, as the moment-resisting frame can individually withstand gravity and seismic loads during construction, the braces can be installed on a story-by-story basis simultaneous with the installation of the moment frame or after its complete construction. This issue cannot be investigated and studied using ordinary analysis, where it is assumed that the entire structure is built at once, and then all the involved loads are applied to the completed structure. Accordingly, this research investigated the effects of staged construction in the mentioned dual systems with V, inverted-V (Chevron), and split-X braces. In this regard, three-dimensional models with 5, 10, 15, 20, and 25 stories incorporating these systems were generated and subjected to pushover analysis under cyclic loading protocols. From the results, it was concluded that staged construction could lead to maximum increases of 19.6% in the axial forces in internal columns due to dead load, 9.3% in the displacement corresponding to the first plastic hinge formation, 13.3% in the base shear corresponding to the first plastic hinge formation, 22.9% in the ultimate lateral strength, and 4.6% in the effective lateral stiffness. Also, staged construction was not found to significantly affect the axial forces in corner and braced-bay columns due to dead load and the energy dissipation under cyclic loading protocols.

Barracks of the Roman Garrison in Olbia Pontica

In the article, on the basis of the discovered sites, new areas of the Roman garrison location are revealed, in the form of seven barracks (contubernia), which were added to the defensive wall and tower at the Lower city of Olbia Pontica. At the lateral quarter, which belonged to the Roman officer, there were found marble bases of the internal columns with the name of the centurion M. Emilius Severinus of the Legio I Italica. The architectural complex located to the south of the barracks in its layout resembles administrative buildings of the Roman camps like a principia – the officers’ house, which consisted of a number of rooms located along the perimeter around the courtyard: with a separate kitchen, a dining room, a central sanctuary room (aedes principiorum), where were stored legionary signs (signa militaria), altars, and statues of deities and emperors. This can be evidenced by the architectural details found during the excavations, terracotta in the shape of eagles and Roman soldiers, Roman weapons and equipment. A similar arrangement of barracks in Olbia is known on the citadel, under the Northern defensive wall. The problem of interpretation of the praetorium building in Olbia is also considered, some quarters of which could serve as Roman barracks. The construction of the barrack blocks and headquarters buildings can be attributed to the second half of the 2nd century AD – the time of the stationary Roman garrison appearance in Olbia.

Dynamic Response Analysis of RC Frame against Progressive Collapse Based on Orthogonal Test

We aimed to investigate the extent to which the initial state generated by unexpected loads, such as explosions and impacts on the remaining structure, affects the dynamic response of the structure. The study used the orthogonal test method to obtain orthogonal table L25 (53) by combining five levels of each of the three factors of column removal time and initial velocity, and the initial displacement of the remaining structure under three failure scenarios of the corner, side, and internal columns at the ground floor of the reinforced concrete frame structure. The degree of influence of different factors on the structural dynamic response, and the result of the unifactorial impact of initial velocity and initial displacement of the remaining structure on the structural dynamic response in the case of failure of the bottom side columns, were obtained by the polar difference method. The results show that the analysis using the orthogonal test polar difference method revealed that the initial displacement has a more significant influence on the dynamic response of the structure, forming the main influencing factor. At the same time, the failure time and initial velocity have a smaller influence on the dynamic response of the structure as secondary influencing factors. In the case of unifactorial influence, the initial upward displacement and initial upward velocity are detrimental to the structure, leading to progressive collapse. In contrast, the initial downward velocity and initial downward displacement are favorable.

High-precision deformation analysis of yingxian wooden pagoda based on UAV image and terrestrial LiDAR point cloud

The monitoring of wooden pagodas is a very important task in the restoration of wooden pagodas. Traditionally, this labor has always been carried out by surveying personnel, who manually check all parts of the pagoda, which not only consumes huge manpower, but also suffers from low efficiency and measurement errors. This article evaluates the feasibility of combining portable 3D light detection and ranging (LiDAR) scanning and unmanned aerial vehicle (UAV) photogrammetry to perform these inspection tasks easily and accurately. The wooden pagoda's exterior picture and inside point cloud are acquired using a UAV and a LiDAR scanner, respectively. We propose a feature−based global alignment method to register the site point cloud. The error equation of the column of observed values is utilized as the beginning value of the feature constraint for global leveling. The beam method leveling model solves the spatial transformation parameters and the unknown point leveling values. Then, the Structure from Motion (SfM) algorithm of computer vision is used to realize the fusion of the dense point cloud of the exterior of the wooden pagoda generated from multiple non−measured images by global optimization and the LiDAR point cloud of the interior of the wooden pagoda to obtain the complete point cloud of the wooden pagoda, which makes the deformation monitoring of the pagoda more detailed and comprehensive. After experimental verification, the overall registration accuracy of the Yingxian wooden pagoda reaches 0.006 m. Compared with the scanning point cloud data in 2018, the model is more accurate and complete. By analyzing and comparing the data of the second floor of the wooden pagoda, we knew that the inclination of a second bright layer and a second dark layer is still developing steadily. Overall, the western outer trough inclines thoughtfully, and the column frame slopes from southwest to northeast. Some internal columns showed a negative offset in 2020, and the deformation analysis of a single column was realized by comparing it with the standard column model. The main contribution of this method lies in the effective integration of UAV images and point cloud data to provide accurate data sources for good modeling. This research will provide theoretical and methodological support for the digital protection of architectural heritage and GIS data modeling. The analysis results can provide a scientific basis for the restoration scheme design.

Flat Slabs in Eccentric Punching Shear: Experimental Database and Code Analysis

Eccentric punching shear can occur in concrete slab–column connections when the connection is subjected to shear and unbalanced moments. Unbalanced moments occur in all floor slabs at the edge and corner columns. As such, this problem is of practical relevance. However, most punching experiments in the literature deal with concentric punching shear at internal columns. This paper presents a developed database of 128 experiments of flat slabs under eccentric punching shear, including a summary of the testing procedure of each reference and a description of the slab specimens. Additionally, a linear finite element analysis of all the specimens is included to determine the relevant sectional shear forces and moments. Finally, the ultimate shear stresses from the database experiments are compared to the shear capacities determined with ACI 318-19, Eurocode 2 and the Model Code 2010. The comparison shows that the Model Code 2010 is the most precise in the predictions with an average tested to predicted ratio of 0.82 and a coefficient of variation of 29.63%. It can be concluded that improvements to the current design methods for eccentric punching shear are necessary.

Deformation capacity evaluation for flat slab seismic design

In flat-slab frames, which are typically designed as secondary seismic structures, the shear failure of the slab around the column (punching failure) is typically the governing failure mode which limits the deformation capacity and can potentially lead to a progressive collapse of the structure. Existing rules to predict the capacity of flat slab frames to resist imposed lateral displacements without losing the capability to bear gravity loads have been derived empirically from the results of cyclic tests on thin members. These rules account explicitly only for the ratio between acting gravity loads and resistance against concentric punching shear (so-called Gravity Shear Ratio). Recent rational models to estimate the deformation capacity of flat slabs show that other parameters can play a major role and predict a significant size effect (reduced deformation for thick slabs). In this paper, a closed-form expression to predict the deformation capacity of internal slab-column connections as a function of the main parameters is derived from the same model that has been used to develop the punching shear formulae for the second generation of Eurocode 2 for concrete structures. This expression is compared to an existing database of isolated internal slab-column connections showing fine accuracy and allowing to resolve the shortcomings of existing rules. In addition, the results of a testing programme on a full-scale flat-slab frame with two stories and 12 columns are described. The differences between measured interstorey drifts and local slab rotations influencing their capacity to resist shear forces are presented and discussed. With respect to the observed deformation capacities, similar values are obtained as in the isolated specimens and the predictions are confirmed for the internal columns, but significant differences are observed between internal, edge and corner slab-column connections. The effects of punching shear reinforcement and of integrity reinforcement (required according to Eurocode 2 to prevent progressive collapse after punching) are also discussed.

Казармы римского гарнизона в Ольвии

The author has identified some new locations of the Roman garrison within previously known architectural objects, based on the mappings of the finds associated with the Roman troops. These are seven barracks (contubernia) adjoining the defensive wall and tower in the Lower City of Olbia, which were studied in 1930s. In a lateral premise, which should belong to the Roman officer according to the Roman military planning, a few marble bases of the internal columns were found, with the name of the centurion M. Emilius Severinus of the legio I Italica. The layout of the architectural complex located to the south of the barracks resembles some administrative buildings of the Roman camps like a principia — the officers’ house, which consisted of a number of rooms located along the perimeter around the courtyard: with a separate kitchen, a dining room, a central sanctuary room (aedes principiorum), where legionary signs (signa militaria) were stored, altars, and statues of deities and emperors. This can be evidenced by the architectural details found during the excavations, terracotta in the form of eagles and Roman soldiers, Roman weapons and equipment. A similar arrangement of barracks in Olbia is known on the citadel, under the northern defensive wall. The problem of interpretation of the praetorium building in Olbia is also considered, some quarters of which could serve as Roman barracks. The construction of the barrack blocks and headquarters buildings can be attributed to the second half of the II century AD — the time when a regular Roman garrison appeared in Olbia.

Numerical Study on the Behavior and Bearing Mechanism of Flat Slabs in Column Loss Events

This study investigates the behavior and the load-bearing mechanism of a typical flat slab with rectangular panels in several scenarios including the removal of a corner, penultimate, and internal columns. The scenarios are rather similar to those used in the conventional evaluation of the progressive collapse potential; however, application of the uniformly distributed loading over panels adjacent to the removed columns was not limited to twice the value of the initial load. Thus, load-deflection curves were drawn up to the point in which a great number of longitudinal slab bars ruptured. Introducing 5 stages on each curve, finite element outputs on concrete cracking pattern and rebar stress state were presented. A significant increase in the stresses along the diagonals of the slab panels accompanied by bar ruptures around columns adjacent to the removed column proved contribution of an important load-bearing mechanism in addition to the behavior called “quasiframe action.” Consecutive rupture of bars showed formation of a zipper-type collapse mode as well as a great tendency to transfer load share of missing column mainly along shorter direction of slab panels. Moreover, the findings indicated that the slab damaged zone could exceed the panels under uniform overloading.

Numerical modelling of punching shear failure of reinforced concrete flat slabs with shear reinforcement

This paper utilises non-linear finite-element analysis with three-dimensional (3D) solid elements to gain insight into the role of shear reinforcement in increasing punching shear resistance at internal columns of flat slabs. The solid element analysis correctly captures the experimentally observed gradual decrease in concrete contribution to shear resistance with increasing slab rotation and the failure mode but is very computationally demanding. As an alternative, the paper presents a novel approach, in which 3D joint elements are combined with non-linear shell elements. Punching failure is modelled with joint elements positioned around a control perimeter located at 0.5d from the column face (where d is the slab effective depth). The joint elements connect the nodes of shell elements located to either side of the punching control perimeter. The punching resistance of the joints is related to the slab rotation using the failure criterion of the critical shear crack theory. The joint-shell punching model (JSPM) considers punching failure both within the shear-reinforced region and due to crushing of concrete struts near the support region. The JSPM is shown to accurately predict punching resistance while requiring significantly less computation time than 3D solid element modelling.

Analysis and comparison of conventional slab and grid slab for symmetric and asymmetric structures

Grid slab consists of ribs spaced at regular interval in perpendicular directions which are monolithic with slab. These grid slabs are generally used for architectural purpose for large spans such as public assembly halls, show rooms, auditoriums, were to avoid internal columns in the structure. The square voided pattern is used in present study. In the present study 12 stories structure of symmetric and asymmetric for regular, plan irregular and vertical irregular structure for both conventional slab and grid slab is considered, analyzed and compared for both gravity load and lateral load conditions as per IS codes. The structures are analyzed using ETABS software. For regular and plan irregular structures static analysis is done as per IS code 1893:2002(Part 1) and for vertical irregular structures dynamic analysis is done for both conventional and grid slab structure as per IS code 1893:2002(Part 1). And compared the results of conventional slab and grid slab for parameters of deflection, storey shear, displacement and storey stiffness.

Creating and designing repairable regular steel buildings with seesaw motion to achieve seismic resilience

Using seesaw structural system in buildings is a way for creating earthquake-resilient buildings, namely buildings which can be easily and quickly repaired with little cost, even after major earthquakes. To create such a system, all internal columns at the lowest story are removed and instead, a central mega support is used, combined with a grid of orthogonal strong girders as the first floor, and all circumferential columns at the lowest story are equipped with energy dissipaters at their bottoms. In this article, after presenting a simplified dynamical model for seesaw buildings, to create the analytical base for proposing the preliminary design rules for this type of buildings, the proposed rules have been developed and supported by conducting several non-linear time history analyses (NLTHA) cases on a set of regular steel buildings with concentric bracings, having 3, 5, 7 and 9 stories with different number of bays, and various bay sizes. NLTHA results indicate that the immediate occupancy performance level is mostly achieved in the designed seesaw buildings. The efficiency of this system in low-rise buildings is more than mid-rise ones. Although seesaw buildings respond relatively well to both near- and far-field events, they behave less effectively in near-field pulse-like earthquakes.

Advanced and Intensified Seawater Flue Gas Desulfurization Processes: Recent Developments and Improvements

Seawater flue gas desulfurization (SWFGD) is considered to be a viable solution for coastal and naval applications; however, this process has several drawbacks, including its corrosive absorbent; low vapor loading capacity since the solubility of sulfur oxides (SOx) in seawater is lower than that of limestone used in conventional methods; high seawater flowrate; and large equipment size. This has prompted process industries to search for possible advanced and intensified configurations to enhance the performance of SWFGD processes to attain a higher vapor loading capacity, lower seawater flowrate, and smaller equipment size. This paper presents an overview of new developments as well as advanced and intensified configurations of SWFGD processes via process modifications such as modification and optimization of operating conditions, improvement of spray and vapor distributors, adding internal columns, using square or rectangular shape, using a pre-scrubber, multiple scrubber feed; process integration such as combined treatment of SOx and other gases, and waste heat recovery; and process intensification such as the use of electrified sprays, swirling gas flow, and rotating packed beds. A summary of the industrial applications, engineering issues, environmental impacts, challenges, and perspectives on the research and development of advanced and intensified SWFGD processes is presented.

Robustness of RC building structures with infill masonry walls: Tests on a purpose-built structure

Structural robustness is a significant property towards improving resilience of buildings, i.e. enhance their ability to withstand and recover from extreme events which often can cause local damage and progressive collapse. It is widely accepted that robustness depends on the capacity of the structure to activate alternative load paths (ALPs) after the failure of load-bearing elements, e.g. columns. Early evidence during World War II showed that progressive collapse of some buildings was avoided by the presence of masonry infill walls. Subsequent studies focused on this effect for cases of sudden column removal although most of these studies were analytical, numerical and only looked at internal columns which are generally less vulnerable to accidental events compared to corner and edge columns. The aim of this study was to analyse how infill walls can improve the robustness of reinforced concrete (RC) buildings in corner columns failure scenarios. A purpose-built 3D two-storey full-scale RC building structure with infill masonry walls was tested. The contribution of masonry infill walls was analysed in terms of: (i) load redistribution, (ii) ALPs, and (iii) Dynamic Amplification Factors (DAFs) to be applied in linear-static analyses. The test was highly monitored by 38 strain gauges, 38 LVDTs and 2 accelerometers to register the vertical and lateral response. The results showed that masonry infill walls had a significant influence on the structural response and activated the predominant ALPs at very small deflections.

Effect of load level of corner columns on punching shear resistance of flat slabs

The problem related to the effect of the corner column load on the punching shear resistance of the slab was presented. Existing experimental studies on internal columns demonstrated that the column pressure could lead to an increase in the punching shear resistance. Because of different confinement conditions of corner column-slab connection joints, it is unclear if such an effect exists for corner columns. New experimental investigations were initiated to clarify this issue. They covered a total of three corner column-slab connection specimens – slabs with a thickness of 140 mm and a longitudinal reinforcement ratio ρl = 1.09% connected with columns of a cross-section of 200×200 mm. The only variable parameter was the column load equal to 500, 1000 and 1500 kN.
 A reduction of the slab load-carrying capacity of about 9% due to a three-fold increase in the column load was noted. Therefore, the effect of the column load turned out to be opposite to that observed for most previous tests on internal column-slab connections, which could have a result of a limited capacity of the slab reinforcement due to additional tensile forces from the lateral expansion of joint concrete.
 Comparison in the light of test results demonstrated, that EN 1992-1-1 procedure allowed for safe, yet conservative estimation of the punching shear resistance. An average ratio of experimental to theoretical load of 1.82 was obtained.

Seismic Behavior of Extended End-Plate Connections Subjected to Cyclic Loading on the Top-Side of the Column.

The extended end-plate connections provide excellent performance in resisting seismic loads in high-risk areas. Most scholars’ experiments and finite element studies on this type of joint are focused on the method of applying displacement loads on the beam tip, while the method of applying displacement on the column side has not been the subject of further study. However, the load transmission mechanism of this type of connection is not completely consistent in actual engineering, as the design concept of “strong column weak beam” does not apply to all joints. Therefore, in this paper, the lateral displacement of the applied column is used to simulate the seismic horizontal force to study the mechanical properties of the connection joints of the “weak column and strong beam” under the limit state of earthquake action. Based on the two internal columns (IC-EP1/2) and two edge columns (EC-EP1/2), the failure modes, strength, stiffness, moment–rotation curve, skeleton curve, ductility, and energy dissipation of this type of connection were studied. Experiment results indicated that this type of connection features semi-rigid and partial strength joints. The connection rotation angle of all specimens in the test exceeds 0.05 rad, which suggests it is an ideal seismic joints. Besides, the relationship between the thickness of the end-plate and the diameter of the bolt has a greater impact on the failure mode of the joint. The finite element (FE) analysis models were established for the above connection. The numerical model was validated against experimental results and showed acceptable consistency.

Progressive collapse vulnerability assessment of irregular voided buildings located in Seismic-Prone areas

Nowadays, many special architectural forms of voided buildings such as hotels, commercial complexes, etc. are constructed in famous cities. In this paper, the effects of opening in the volume of low- and mid-rise irregular voided structures with low to high seismic resistance on the progressive collapse vulnerability are investigated. The structures are three and nine stories high, seismically designed with a steel moment frame system based on the AISC seismic code, and are located in sites with high, moderate, and low levels of seismicity. Detailed three-dimensional nonlinear dynamic analysis is performed to investigate spatially distributed damage to frame members and the structural robustness against abnormal loads according to the GSA 2016 guidelines. The response quantities are expressed in the form of the displacement of the node above the removed column, the spatially distributed formation of plastic hinges, the stress growth in nearby columns after progressive collapse occurrence, and the connection robustness analysis. The results show moment connections that govern the robustness of the structure and they are the most critical components in the structure. In addition, larger openings and proximity of the column removal scenario to position of the opening play a significant role in reducing the progressive collapse vulnerability of voided structures. However, in the scenarios of removing the internal column away from the opening, the progressive collapse mechanism of the structures with or without opening does not differ. Therefore, in the structural robustness analysis, internal columns away from opening of the voided buildings should be considered as critical and controllable elements in the progressive collapse capacity of structures. Among the modeled buildings, only the buildings located in high seismic areas can pass progressive collapse analyses and the seismicity level of the site is the most important parameter in robustness of the structure in comparison with the height or irregularity of the structure. Increasing the height of structures also reduces the amount of stress growth in the columns adjacent to the demolished column and the taller structures are safer structures in this regard.