Interior Column Research Articles

Progressive Collapse and Post Impact Damage Assessment in a Regular Beam-Slab Building & Flat-Slab Building on the Intermediate Floor

Progressive collapse, where a localized member failure causes widespread structural collapse, has become a critical concern nowadays, due to its potential to cause significant financial losses and loss of human life. Triggers include natural disasters like earthquakes and floods, as well as accidents, attacks and explosions. Reinforced concrete flat slab structures, which are eminent for their architectural flexibility and have larger spans, are particularly susceptible to disproportionate collapse, due to the lack of floor beams, which can redistribute loads after a column failure, unlike moment frame buildings. This research examines how multi-story reinforced concrete flat slab buildings behave, under prescribed gravity load combinations, compared to conventional framed buildings. The effects of removing columns at specified locations from an intermediate floor of the multistorey building are also examined. However, this investigation covers both the column removal approaches to check a possibility of disproportionate collapse which are; static removal and dynamic instantaneous removal. Furthermore, the research also assesses the efficacy of perimeter beams, in minimising the risk of gradual collapse in flat slab structures, by scrutinising their ability to reduce joint displacement, chord rotation, and demand capacity ratio. ETABS v18 was used to analyze all the 18 models. The findings revealed that buildings are more prone to progressive collapse when corner columns are removed, as opposed to edge and interior columns, due to higher Demand-Capacity Ratios (DCR) and joint displacement. In comparison to dynamic analysis, the static evaluation exhibited greater DCR values and vertical joint displacement. Furthermore, since they have a more efficient load redistribution mechanism, traditional framed structures performed better than flat slab models. The simulations additionally indicated that, adding edge perimeter beams, substantially lowered the possibility of progressive collapse in flat slab structures. Moreover, the tested flat slab building models, with and without perimeter beams showed no indications of progressive collapse, when specified columns were removed from the intermediate floors, since the DCR values of the crucial columns stayed within the permissible range of 2.0. In conclusion, structures built in compliance with IS 1893:2016 code and designed to withstand seismic loads demonstrate stronger resistance against significant damage, brought about by column failures.

Method of Average Vertical Earth Pressure for HFCCTs Based on Differential Settlement

AbstractThis paper presents a modified and simplified calculation method, taking into account the differential settlement between the soil columns surrounding the cut-and-cover. High-filled cut-and-cover tunnels (HFCCT) are usually subjected to high earth pressures above the top of the CCT due to an ultra-high backfill. However, the estimation methods for earth pressure above the top of CCT are ambiguous. Through the theoretical analysis of the average vertical earth pressure (AEP) at the top of the CCT, it is found that an additional earth pressure above the top of the overburden pressure is induced, and the magnitude is related to the differential settlement between interior and exterior soil columns. Thus, through a combined theoretical derivation and numerical analysis, a modified formula is proposed. The results show that the vertical earth pressure increment above the top of CCT can be linearly correlated to the differential settlement. In addition, the correlation needs to be calibrated by considering several effects on sites, such as slope angle, groove-width ratios, cross-sectional shape, and the type of backfill. The change in influencing factors has no effect on the function type of the p−δ fitting curve, but it will affect the coefficient k.

A novel approach for quantifying dynamic impacts on steel frames induced by instantaneous interior column loss

This research presents an innovative approach to accurately quantify dynamic impacts on the steel frame structure resulting from the instantaneous loss of an interior column. This methodology effectively calculates the dynamic amplification factor (DAF) when the steel frame reaches its collapse limit state and predicts the structure's deformation under such a scenario. Central to this approach is the conversion of the static load-deformation curve, pertinent to a scenario of interior column loss, into a dynamic force load-deformation curve using the concept of energy balance. A comprehensive parametric analysis was conducted to study how different structural parameters, such as beam depth, span, slab thickness, rebar diameter, and slab aspect ratio, affect the enhancement factor (i.e., the ratio of collapse resistance to yield resistance). A pragmatic formula for determining enhancement factor was subsequently suggested. Moreover, this study delved into how these structural parameters influence the dynamic amplification factor at the collapse state, revealing a notable dependency of dynamic amplification factor on the slab aspect ratio that an increasing aspect ratio correlates with a rising dynamic amplification factor trend. The manuscript also presented a detailed methodology for computing the dynamic deformation of frame structures in the event of an instantaneous interior column loss. The results of the case study show that the proposed method closely matches the accuracy of numerical analyses, with differences falling within a 15% range.

Effect of steel reinforcement corrosion on progressive collapse resistant of beam-slab structure with interior column failure

To investigate the effect of steel reinforcement corrosion on the progressive collapse resistance of reinforced concrete (RC) structures, this study shows a methodology for establishing a finite element model (FEM) of a beam-slab structure by LS-DYNA software considering steel reinforcement corrosion. The reliability of this methodology was validated by experimental results. The analysis results indicate that considering the effect of the slab causes the beam-slab structure to enter the stages of tensile catenary action (TCA) and tensile membrane action (TMA) at smaller displacement. Moreover, as the corrosion time increases, the influence of the TCA on the structural resistance decreases. After prolonged corrosion, the top reinforcements of the beam at the failed column sides fail to fully utilize their tensile capacity when the structure fails. Furthermore, the corrosion of reinforcement significantly weakens the TCA and TMA to the structure, and neglecting the effect of the slab may lead to an overestimation of the weakening degree of the TCA caused by steel reinforcement corrosion. Additionally, the contribution of the slab's resistance in the beam-slab structure follows an "S"-shaped curve in relation to the displacement of the failed column, and the contribution of the slab to the structural resistance ranges between 40% and 60%.

Reconstruction of Single-Bay Buddhist Architecture Based on Stylistic Comparisons in Northeast Fujian, the Core Hinterland of the Changxi River Basin—Using Gonghoulong Temple as an Example

In the Changxi River Basin in eastern Fujian, a few stone elements remain and Buddhist buildings with one bay in width and three bays in depth have been preserved dating from the timespan of the Tang to the Song dynasty. These features are characterized by a regional form of early Buddhist architecture seldom seen in Chinese history. The article focuses on the reconstruction of a Song dynasty Buddhist building at the Gonghoulou Temple site in Huotong Town, Jiaocheng District, Ningde City, and aims to analyze the potential characteristics and rules of single-bay Buddhist architecture. From the styles of the remaining stone columns, the direction of the lotus carving at the column base, and the mortises of the plinth stone, a spatial arrangement is indicated that includes an open front corridor and a closed rear section. A “reconstruction” of the ruler used in the original building reveals the possibility that a local Fujian ruler was used, shorter than the standard measurement device employed elsewhere. The analysis of the frame construction indicates that this hip-gable roof-covered Buddhist hall utilizes the horizontally layered logic of multi-storied palatial-style halls. Key elements include its gentle roof slope, restraint from the practice of shortening the roof ridge, use of the traditional chuji method, and the interior columns use of internal longitudinal architraves secured to beam supporting brackets. This research brings to light a unique architectural type that has disappeared in the course of history and was previously unknown to the academic community. It holds significant importance and value for deepening the understanding of the history of timber frame architecture technology in Fujian.

Influence of Interior Column on the Behaviour of Quasi-Rectangular Tunnel

The growing population in major cities around the world requires significant development of transportation infrastructure, especially underground system. It requires the construction of more subway lines, and larger tunnel cross-sections. In underground construction, a cross-sectional shape which is a combination of circular and rectangular tunnels is an advanced trend. This shape incorporates the advantages of both forms. There are two terminologies used to classify these shapes, including sub-rectangular and quasi-rectangular tunnels. While the sub-rectangular tunnel lacks an interior column, the quasi-rectangular tunnel includes an interior column located at the center of tunnel. Recent studies focus on separately investigating the behavior of sub-rectangular and quasi-rectangular tunnels using various methods such as numerical methods, analytical methods, and experimental methods. The present study conducted a numerical comparison of these two types of tunnels. The results indicated that the presence of an interior column help to increase the stability of the lining structure. The internal forces within the quasi-rectangular tunnel with an interior column are smaller than those of the sub-rectangular tunnel and quasi-rectangular tunnel without an interior column.

Analytical model of compressive arch action for one-way RC beams and two-way framed substructures under column removal scenarios

This paper proposes a direct analytical model to evaluate compressive arch action (CAA) of reinforced concrete (RC) beam-column sub-assemblages under middle column removal scenario (MCRS), incorporating bending curvature of the double-span beam, and different horizontal and rotational restraint conditions at the beam ends. Based on the proposed approach, the structural engineer can easily obtain the CAA peak capacity and the corresponding CAA displacement by hand calculations. Unlike the previous models in which the accuracy highly relies on pre-assumed CAA displacement, this prediction approach directly derives the CAA displacement and CAA capacity through force equilibrium, geometric relationship, compatibility and boundary conditions, incorporating various horizontal restraint conditions, span-to-depth ratio and section profile of the bridging beam. Comparison with existing test results in available literature indicates that this model not only gives good predictions of peak capacity, displacement and maximum axial beam force in CAA, but also incorporates the effect of horizontal restraint stiffness and working stress of compression reinforcement. Besides, a further simplified explicit model is proposed to enhance usability in practical design, and sensitive studies are conducted to study how the simplification affects the prediction accuracy of vertical CAA capacity and displacement. Thereafter, the proposed model is extended to substructures with orthogonal beams in X- and Y- directions to predict CAA capacity under different column removal scenarios such as interior, penultimate, edge and corner column removal cases.

Seismic target drifts for underground railway stations. Cases of traditional rigid connections and sliding interior columns

In this study, the seismic performances of underground structures with either transverse traditional rigid layout or sliding interior columns are numerically evaluated by pushover analyses; both the horizontal and vertical components of the seismic ground motion are taken into account. Thirty-one representative actual subway stations featured with various structural forms, soil types, and burial depths are analyzed in this study; although each of these stations has rigid connections between all their structural members, alternative solutions with sliding interior columns are also designed. The seismic performance of each station (with rigid connections and sliding columns) is evaluated in the framework of the Performance-Based Design by considering four Target Drifts: Normal Operational, Immediate Operational, Reparable Operational, and Irreparable. The corresponding drift thresholds are determined for each station, and then global average values for the two considered cases (traditional rigid layout and sliding columns) are proposed. The rationality of the proposed seismic performance quantification system is verified by comparison with observed damage (Daikai station, traditional rigid solution) and experimental results (shaking table test of reduced scale station model with sliding columns).

Collapse-resistant mechanisms induced by various perimeter column damage scenarios in RC flat plate structures

This paper aims at assessing the impact of removing various numbers of perimeter columns on the integrity of RC flat plate substructures. Compared to interior columns, those at the corner and edge positions on the building perimeter are more likely to damage by accidental and abnormal loads, which in turn may cause progressive collapse of the entire structure. Given the uncertainty of the loading events, the likelihood of multiple perimeter columns being simultaneously destroyed is also high. However, existing research has primarily focused on the single column removal cases. To address this research limitation, a 3D high-fidelity finite element model of a flat plate substructure with a missing corner column (named Model C) was developed. The accuracy of the model was validated based on our previous experiment of the same substructure. The validated model was subsequently modified to cover two and multiple perimeter column removal scenarios. The two new models are namely, Model C_1e in which a corner column and an adjacent edge column were damaged and Model C_2e, with a corner column and two adjacent edge columns being removed. The simulation results reveal that flexural action was the primary load resisting mechanism in all three models. The load carrying capacity with three column removals was reduced by 75.6% compared to the removal of a single corner column. Full-depth cracks were found at the cut-off position of the top slab rebars for the columns adjacent to the removed one(s). In Model C and Model C_2e, cracks exhibited a diagonal axisymmetric failure pattern of the corner of the slab, with equal load transfer to two adjacent columns. In contrast, Model C_1e exhibited a diagonal non-axisymmetric failure pattern of the slab corner, with more loads being transferred to the adjacent column along the shorter bay. The energy-based dynamic response analyses were also performed to obtain the Dynamic Increase Factor (DIF) for the substructure models under different column removal scenarios. Based on the nonlinear regression analysis, the DIFs for the substructures with one and two column removals were found to be ranged between 1.22 and 1.51, and 1.28–1.68, respectively.

Numerical modelling and analysis on axial loading behaviors of composite column-in-column system

Previous studies have showed that severe earthquake could cause damage to concrete filled steel tube (CFST) column. Although the energy dissipator can be used to improve the seismic performance of the CFST column, its enhancement is limited. Based on a new passive control strategy, the authors recently proposed a novel composite column-in-column (CIC) system to enhance the seismic performance of the CFST column. The CIC system was composed of an exterior column, an interior column, and a series of connecting springs and dashpots, and its load-bearing capacity and seismic mitigation effectiveness was experimentally and numerically demonstrated respectively. The test results revealed that under compression tilting might occur to the interior column when the interior column was not restrained by the springs and dashpots, which resulted in the underestimation of the ultimate axial loading capacity of the CIC system. This paper extends the previous experimental study by further conducting numerical investigation to clarify the restraint effect provided by the springs and dashpots on the axial loading behaviors of the CIC system. The influences of the length-to-diameter ratio, diameter-to-thickness ratio, concrete strength and steel strength on its axial loading capacity are comprehensively examined. Moreover, according to the codes EC4, AISC 360–16, GB 50936–2014 and T/CCES 7–2020, formulae for predicting the ultimate axial loading capacity of the system are developed and validated by the test and numerical results. Results show that, by employing the optimized springs and dashpots, the exterior and interior columns can work compatibly to avoid the tilting and global buckling in the CIC system, providing a good axial loading behavior with favorable ductility and post-peak performance. The prediction formulae are reliable for the CIC system design and analysis.

An Investigation of a Post-tension Problem in a Conference Hall Roof

Introduction: Post-tensioning is a technique for strengthening concrete members by embedding tendons into the concrete before casting. When the concrete has acquired the desired strength, these tendons are tensioned using hydraulic jacks. This study deals with structurally analyzing and designing a 21 m × 25 m conference hall without interior columns contained within eleven stories building. Methods: The hall was located on the 9th floor. Many structural floor systems were proposed for the hall such as composite steel-concrete, waffle concrete, and post tensioned girder slab. The structural system of post-tensioned concrete girders with a top reinforced slab was chosen due to its advantages: low deflection and low risk of cracking, and increase of net floor height. Stressing of strands (live ends) was applied from the four sides of the concrete slab. Twenty-three live ends were placed in north-south direction and 20 live ends in east-west direction. Results: The ultimate strength of the stands was 1860 MPa. The jacking force, 209 kN, was applied in each strand which represented 75% of ultimate strength. The post-tension concrete slab was analyzed with Ram concept software, which revealed that the total elongation of strands in the E-W direction ranged from 116 mm to 152 mm, and the total elongation of strands in the N-S direction ranged from 120 mm to 172 mm. Conclusion: The problem of warping of nine live anchorage ends in the south-north direction was encountered during post-tensioning, which resulted in the movement of strands from their original locations. A rehabilitation plan was proposed to overcome the aforementioned problem.

Innovative scheme for RC building progressive collapse prevention

Progressive collapse of reinforced concrete (RC) building due to column failure can cause human casualties and severe irreparable damage or total collapse of the building. Different methods have been presented to mitigated progressive collapse of RC buildings; however, most of them are installed externally after construction and are costly, demanding, and require manufacturing mitigating elements such as steel cables, steel devices, or composites. This study presents an innovative mitigating scheme to improve the progressive collapse resistance of such buildings. The proposed scheme applies during construction and comprises of adding short wasted leftover steel bars from the construction site with special configuration in the slab around potential failed interior column. To examine the effectiveness of the proposed scheme, three-dimensional nonlinear fiber element-based model was developed, validated, and utilized for the analysis of such buildings. The findings of the study show that the proposed scheme improved progressive collapse behavior of the building with a percentage increase in total dissipated energy up to 241.8%. The scheme is eco-efficient and cost effective as it requires minimum amount of material, saves energy required to produce new steel bars, and can serve as an effective solution to mitigate progressive collapse of RC buildings subjected to column failure.

Post-fire properties of beam-slab specimens with different restraints on interior beams

This study investigated the influence of the vertical restraint of the interior beam and columns on the post-fire mechanical behaviours of four beam-slab specimens. Two vertical restraints and interior beams with and without a rigid vertical restraint were investigated. In addition, a numerical model was developed to analyse the load–deflection curves and membrane actions of the beam-slab specimens after exposure to fire. A plane equation and deflection parameter were proposed to predict the yield-line and ultimate loads of fire-damaged beam-slab specimens with different vertical restraints. The results revealed that, compared with the vertical restraint of the interior beam, the restraint of the columns has a greater effect on the ultimate loads of the beam-slab specimens after exposure to fire. Compared with the experimental and numerical results, the proposed elliptic equation method can be used to analyse the ultimate loads and membrane action distribution of the beam-slab specimens with different restraints of the interior beams.

Structural property of stainless steel minor-axis joints of interior columns with box panel

With the component method, a design approach was derived for predicting the structural properties of stainless steel end-plate joints with box panel, where box panel was formed using the skin-plates welded between the column flanges along the minor-axis. Four end-plate minor-axis joints with box panel were tested under static and cyclic loading, involving beam-to-interior column joints made of austenitic and duplex stainless steels. The monotonic and hysteretic properties of the experimental joints were discussed, including the failure characteristics, experimental curves (F-Δ), and degradation and energy dissipation behaviour. Meanwhile, elaborate finite element (FE) models were developed for further analysis of the structural behaviour of the tested joints, and a parametric study was conducted afterwards. The proposed design approach provided reasonable estimations for the experimental and FE results of stainless steel minor-axis joints with box panel, demonstrating the applicability of this proposal.

Confinement effect of two‐way beam‐and‐slab system on the effective compressive strength of interior concrete columns

AbstractMultistory concrete buildings may resort to the strategy to cast columns and slabs with high and normal compressive concrete strength, respectively. Current design codes propose expressions to specify the effective compressive strength of interior columns confined only by flat slabs or beams with the same width as the column. However, when thin slabs and narrower beams are used, the confinement may not be enough to increase the lateral stress. The structural behavior of these interior columns is investigated in this paper using numerical nonlinear models. The influence of concrete strength column‐slab ratio, the steel reinforcement ratio of the column and the beam, beam height and the column width ratio and the biggest dimension of the column's cross section were tested with and without vertical load on the beam. The results were compared with expressions found in the literature.

Progressive collapse mode induced by slab-column joint failure in RC flat plate substructures: A new perspective

Majority of progressive collapse incidents of concrete flat plate structures were caused by slab overloading in the form of punching shear failure at a slab-column joint, which exhibit distinctive resistance mechanism from those triggered by column losses. Relevant studies on the slab overloading scenario are scarce. To fill this gap in research and to broaden the perspective on different collapse modes, an experimental test was conducted on a 1/3-scale 2 × 2-bay flat plate substructure specimen by applying an increased downward uniform load on the slab, until the structure was completely damaged following the initial punching shear failure at the interior slab-column joint and was unable to take any further load. In addition, the flexural capacity of the specimen was evaluated using the yield line theory, and an analytical model was also proposed to estimate the post-punching peak load of the specimen. Finally, the experimental results obtained from this study were compared to those of a similar test under an interior column removal scenario. Comparisons indicate that the specimen under the slab overloading scenario displays better collapse resistance than that under the column removal scenario. Nevertheless, the residual resistant capacity of the overloaded specimen may not be adequate enough to prevent the collapse of the entire structure after the initial punching failure.

Traces of Islamic Architecture in the Design of the 'Gedung Sate' in Bandung

Gedung Sate was built to accommodate various architectural styles derived from local and foreign elements. The local elements have been widely studied, such as those relating to the architecture of the 'Candi' on the island of Java. Many external elements are associated with the Moorish European style and that of the Dutch. However, according to the elements, it also indicates the existence of Indian Islamic architecture, the Mughal style. This study of the Islamic elements of Mughal India has not been pursued or presented any further. This study aims to identify the traces of Islamic architecture in the Gedung Sate, especially those derived from the Mughal, Moorish and local styles. This research method used a qualitative approach by studying the morphology of Gedung Sate and Mughal or Moorish buildings to identify the relationship between their architectural elements. The results show that Gedung Sate does indeed show the use of Mughal architectural elements, especially in the outer layout and mass, processing of the figure section, and the ornamental exterior column, while the Moorish influence is more visible in the processing of curved elements and column heads and slender interior columns showing light elements. The idea of using Islamic architecture is carried out to represent the splendor in the typology of new buildings in the prospective capital city of the Netherlands Indies, namely Bandung. Indian architecture is used as a reference because it is considered to have a close relationship with Candi as an important resource in Java.

Carbonation-Induced Corrosion of Reinforced Concrete Elements according to Their Positions in the Buildings

Most regulations on the manufacturing of concrete for reinforced concrete structures rest on durability models that consider the corrosion of reinforcements. Those models are based on factors such as humidity, frost, presence of chlorides, and internal characteristics of the concrete itself, like resistance, porosity, type of cement, water/cement ratio, etc. No regulations, however, adopt a purely constructive perspective when evaluating the risk of corrosion, i.e., the relative position of the reinforced concrete in buildings. The present work focuses on the relationship between the position of the damaged element and the building envelope. A total of 84 elements (columns and reinforced concrete beams) across twenty buildings were analysed in the provinces of Alicante and Murcia (Spain). The reinforcement concrete of these elements underwent carbonation-induced corrosion according to their positions in the buildings: (A) façade columns in contact with the ground; (B) interior columns in contact with the ground; (C) columns of walls in contact with the ground; (D) columns and external beams protected from rain; (E) columns and external beams exposed to rain; (F) columns and beams in air chambers under sanitary slabs; and (G), columns and interior beams. Of all types, elements (E) and (F) suffered carbonation-induced corrosion faster than the models used in the regulations, and type (G) underwent slower carbonation.

Hybrid simulation of a steel dual system with buckling‐induced first‐story column shortening: A mixed control mode approach

AbstractThis paper presents a hybrid simulation (HS) with a proposed substructuring technique that captures the effect of first‐story column local buckling and axial shortening on the frame behavior. The HS is applied to examine the seismic response of a two‐dimensional seven‐story, two‐bay steel dual system. The experimental substructure consists of a full‐scale interior column and beam cruciform subassemblage, including a moderately ductile first‐story built‐up box column and two I‐shaped beams. Under combined axial and lateral loads, local buckling can occur near the column base, resulting in column shortening. The specimen is loaded through a four‐degree‐of‐freedom (DOF) mixed‐mode control (three displacement‐ and one force‐control) actuation system that simplifies the actual complex boundary conditions of the frame structure. To account for column shortening in the HS, a new approach consisting of a set of fictitious equivalent forces applied to columns in the numerical model to achieve compatible displacements with the experiment is implemented. Shortening of the two exterior columns in the model is simulated through finite element analysis using the computer program ABAQUS in an attempt to capture the redistribution of axial loads with column shortening. The test results confirm that the proposed modeling and control methods successfully integrate the experimental substructure and ABAQUS simulation into the HS, resulting in a more realistic frame response that captures the effect of column shortening in the analysis. The moderately ductile built‐up box column is verified to perform well in near‐fault earthquake loadings.

Critical collapse deformation of 3-D steel frame with composite floor system

Determination of the CCD (critical collapse deformation) for frame structures is crucial to calculate their final collapse resistance due to a column loss. This paper studies the CCD of 3-D (three-dimensional) steel frame structure in an interior column loss. The work presented in this paper is an extension of previous work by authors on two-dimensional (2-D) steel frame, by further introducing the effects of concrete floor slab. The fracture of steel is considered by Bai-Wierzbicki model, in which the effects of Lode angle and stress triaxiality on fracture of steel are accounted for. The Bai-Wierzbicki model is imported into software ABAQUS by a user-defined subroutine. The CCDs of 2-D steel frame, 3-D steel bare frame, and 3-D steel frame with floor slab due to an interior column loss are compared. The effects of beam span, beam height, slab thickness, and slab aspect ratio on the CCD of 3-D steel frame are studied. For steel frame with different slab span-to-thickness ratios, explicit calculation formulae are established to calculate the CCD of steel frame. It is found that due to the existence of floor slab, the CCD of steel frame is significantly reduced. A larger span-to-depth ratio for steel beam ensures a greater CCD of steel frame. For a certain slab span-to-thickness ratio, the CCD-to-depth ratio of steel beam is almost linear against the span-to-depth ratio of steel beam. Moreover, the CCD of steel frame increases when the slab aspect ratio increases.