Column Failure Research Articles

Dynamic response of planar frame sub-structure isolated by friction pendulum bearings subjected to a middle column removal scenario

The aim of this study is to investigate the dynamic response of planar frame sub-structure isolated by friction pendulum bearings subjected to a middle column removal scenario. The study presents and evaluates the dynamic structural behaviors, load transfer mechanisms, progressive collapse resistance, and dynamic increase factor (DIF) results of FPBs-isolated planar frame. The study explores the influence of the equivalent radius and friction coefficient of the FPB, as well as the peripheral constraints of the failed column. The results show that the compressive arching action (CAA) and catenary action (CA) cannot be fully developed for buildings isolated by FPBs due to the significant reduction in the lateral stiffness of the isolated layer caused by FPBs. The structural responses of planar frame isolated by FPBs are much larger than those of corresponding fixed-base buildings. The DIF of buildings isolated by FPBs initially decreases and then barely changes with an increase in the stabilized vertical displacement of the failed column. The presented fitted formula for DIF of planar frame isolated by FPBs describes the obtained results well. The friction coefficient and equivalent radius of FPBs show very limited influence on the dynamic response of planar frame isolated by FPBs under progressive collapse, but reinforcing the peripheral constraints of the failed column can enhance the progressive collapse resistance of isolated planar frame.

Wear factors and mechanisms of L-80 steel casings

Casing wear in directional drilling is inevitable and may result in catastrophic failure of the casing column. It is thus essential to understand its mechanisms and quantify its extent by estimating the casing wear factor. In this research, actual field casing samples, drilling pipe joints and muds were considered. An in-house built testing facility was used to test several L-80 casing samples by considering three rotational speeds of the drill pipe tool joint (DP-TJ) (115, 154, and 207 rpm) and three side loads (1000 N, 1200 N and 1400 N). The influence of the water- and oil-based muds on the coefficient of friction, wear volume, wear factor and wear mechanisms were investigated. The results revealed that under water-based mud (WBM) lubrication casing wear volume and wear factors were more than twice that of oil-based mud (OBM) lubrication. Moreover, it was observed that as the side load increased under both OBM and WBM lubrication at a constant rpm, both wear volume and wear factor increased. However, increasing the rotational speed while maintaining the side load constant decreased the wear factor, owing to the localized softening effect caused by the high heat generation at the contact area and the possible hydrodynamic lubrication regime change at higher speeds. The analysis of the digital microscopic images taken at the wear region shows that abrasive mechanism was dominant in the case of OBM lubrication. On the other hand, both abrasive and adhesive wear mechanisms were present under WBM lubrication.

Cyclic Compressive Behavior and Load-Strain Model of FRP-ECC-HSC Composite Columns

An innovative composite column, which consists of a high strength concrete (HSC) core, engineered cementitious composites (ECC) ring, and fiber-reinforced polymer (FRP) tube, has recently been developed and subjected to monotonic axial compression testing by the authors. In this study, the cyclic compressive behavior of this proposed FRP-ECC-HSC composite column was examined. Test parameters, including HSC core strength, FRP tube thickness, and ECC ring thickness, were investigated. Typical failure modes, dilation behavior, and axial load versus axial strain behavior were discussed and analyzed. It was found that the FRP-ECC-HSC composite columns exhibited improved deformability, compared with the counterpart traditional FRP-confined HSC columns, with the ultimate axial compressive strain increased by 0.7%–69.1% for the tested specimens. Meanwhile, the ultimate axial strain for cyclically loaded specimens is larger than that for monotonically loaded specimens in general, indicating a delayed column failure. Cyclic axial load-axial strain models, including the envelope model, unloading and reloading models, plastic strain equation, and stress deterioration equation, were proposed to predict the cyclic compressive behavior of the tested specimens. The proposed model was verified with the test results and exhibited good performance.

Influence of deep-cement-mixing column rows on the performance of geosynthetics-reinforced column-supported railway embankment

Knowledge regarding the stability of geosynthetics-reinforced column-supported railway embankment (GRCSE) on soft foundation is of great significance for transportation infrastructure safety design, and deep-cement-mixing (DCM) columns constructed under the toe of an embankment is used to improve the performance of GRCSEs. This study conducted two centrifuge model tests to simulate the failure of a constructed embankment in a 40-g environment. The failure mechanism of each component in the GRCSE system and the effect of additional DCM column rows near the embankment toe on the GRCSE performance were analysed. The particle image velocimetry (PIV) technique was used to draw further insights from the results. The tests revealed that a failed column within the GRCSE system led to the progressive failure of adjacent columns, coupled with the progressive and retrogressive propagation of shear strains in the soft soil, which resulted in embankment collapse. The addition of DCM column rows near the embankment toe reduced the local shear strain accumulation in the soft foundation and thus improved the overall stability. The incremental tensile strain of the geosynthetic reinforcement in various phases was different in the cases with and without additional DCM column rows. Moreover, the effects of various factors of DCM rows, including row number and length, on the GRCSE stability were numerically analysed.

Resistance of Gable Structure of Nuclear Island to Progressive Collapse in Conventional Island Shield Building of Nuclear Power Plants

The gable wall of the conventional island of a nuclear power plant carries various pipeline loads connecting the nuclear island and the conventional island. If the gable wall collapses and is damaged due to the progressive collapse of the main plant structure of the conventional island, it will directly threaten the safety of the nuclear island. Therefore, it is of great significance to systematically study the resistance of the gable structure of the nuclear island to progressive collapse for the safe operation of nuclear power plants. Based on the SAP2000 finite element analysis platform, this paper established a model of the reinforced concrete frame structure of the first span of the shield building on the conventional island of a nuclear power plant, including the gable. According to the alternate path method, the node displacement and bearing capacity responses were used to determine the critical components in the gable, and single column failures of the top four in importance were selected as different analysis conditions. Nonlinear static and dynamic methods were used to analyze the displacement, internal force change, hinge sequence of the gable structure on the side of the nuclear island, and the ability of the gable to resist progressive collapse. The analysis results showed that the gable structure of the nuclear island had good resistance to progressive collapse under four single column failure conditions, whether by nonlinear static or dynamic analysis, and the overall vertical displacement obtained by the nonlinear static analysis was larger than that obtained by the dynamic analysis.

Evaluation of modelling uncertainties impact in older infilled frame RC structures

The seismic response of infilled frame reinforced concrete structures is affected by different sources of aleatory and epistemic uncertainties and is particularly sensitive to the modeling parameters evidenced by reported numerical and analytical studies. In the current study, a probabilistic sensitivity analysis is performed by nonlinear static (PNSA) and nonlinear dynamic analyses (PNDA) on a base-case infilled frame structure incorporating structural (beam, column) and non-structural (masonry infill) components behavior. Therefore, the state-of-the-art models of the most effective sources of nonlinear response employed herein as fiber section to depict the axial-moment interaction in frame components, bi-diagonal eccentric strut to capture the cracking and crushing of masonry infill, and the shear failure in columns caused by infill-frame interaction. Finally, results are illustrated by tornado plots incorporating probabilistic sensitivity to material and component parameters for operational (O), damage (D), life safety (L), and collapse (C) limit states. Results state that the building response is significantly affected by the modeling parameters of infill characteristics, mass source, and the damping of the structure.

Effect of Lateral Reinforcement on Strength and Ductility of Reinforced Concrete Columns

Abstract: Concrete confined by stirrups has a greater ductility than unconfined concrete which is widely used in reinforced concrete (RC) structures and its behavior is a classic topic ofdiscussion. Non-linear behavior of reinforced concrete is complex due to involvement of various heterogenic material properties and cracking behavior of concrete. It is very important to understand the response and failures of columns subjected to lateral loadsin order to save lives and reduce the damage to the building components. ANSYS is widely used finite element analysis (FEA) software which has the tools to analyze structural elements and their non-linear behavior based on the finite element procedure The failure prediction of reinforced concrete elements is usually carried out using experimental testing, and the observations are recorded only at critical locations due to restriction at the cost of testing equipment and accessories. To avoid the destructive testing, cost-cutting of materials and labor, the behavior prediction of reinforcedconcrete elements is typically carried out using numerical methods like Finite Element Method which responds well to non-linear analysis as each component possesses different stress-strain behavior. In this study, reinforced concrete columns were modeled having different tranverse reinforcements and subjected to axial loads along with monotonic lateral loading, their behavior is studied in terms of deformation, stress, strain, crushing/cracking and forcedisplacement curves.

Development of a high-fidelity failure prediction system for reinforced concrete bridge columns using generative adversarial networks

Visual damage patterns of structural components are critical to evaluate structural performance. However, visual damage images can only be obtained by laboratory tests or in-situ tests, which require massive funding and human workforces. In this study, a novel bridge column failure prediction framework is proposed based on generative adversarial network (GAN). Trained with merely 110 damage patterns collected from experimental cyclic loading test, the proposed approach predicts the high-fidelity surface damage patterns of concrete bridge columns given the information of the column design parameters as well as the user-desirable performance level, i.e., Damage Index (DI) of the column. Two network architectures and three label encoding strategies are explored to investigate the performance in estimating the damage pattern. By incorporating DI as a numerical label, the proposed network is able to predict the unseen damage patterns which are not available in the training dataset. Also, it is found that adding classifiers and regressors in the discriminator to account for the condition vector is beneficial for network training, achieving a Frechet Inception Distance (FID) of 102.6 when producing the synthetic patterns. Extensive experiments have demonstrated that the proposed framework is capable of synthesizing decent damage patterns with superior fidelity, providing bridge engineers with a platform to evaluate the potential failure modes during seismic design and evaluation.

Spatial variability of explosive blast loading and its effect on damage risks to reinforced concrete buildings

Explosive blast loading is subject to inherent variabilities due to complex interactions between chemical reactions, air particles, fireball and shockwave. Explosive field trials have quantified this variability, and described herein is the probabilistic characterisation of spatial variability of airblast for pressure and impulse. In other words, pressure–time measurements from adjacent (close) gauges are not identical, but correlated based on the distance between adjacent gauges. The degree of correlation is moderate if distance between adjacent gauges is small (i.e., angle between gauges is small where each gauge has the same radial standoff from the charge), and reduces to a weak correlation for gauges spaced much further apart. The effect of spatial variability of airblast on damage and collapse risks is investigated for a 10 storey reinforced concrete building subject to a vehicle borne improvised explosive device (VBIED) attack, and the accidental detonation of explosive ordnance (EO). The structural reliability analysis considered load redistribution for failed columns, dead and live loading variabilities, and blast loading and resistance model errors. It was found that allowing for the spatial variability of airblast decreased progressive collapse probabilities by up to 65% when compared to the case of fully correlated airblast. Designing against progressive collapse using either a threat dependent design or the Alternate Path method reduced damage risks by over 90%, and in many cases by over 99%.

Some Considerations on the Behaviour of Bolted Stainless-Steel Beam-to-Column Connections: A Simplified Analytical Approach

Stainless-steel has proven to be a first-class material with unique mechanical properties for a variety of applications in the building and construction industry. High ductility, strain hardening, durability and aesthetic appeal are only a few of them. From a specific point of view, its nonlinear stress–strain behaviour appears capable of providing a significant increase in the rotational capacity of stainless-steel connections. This, in turn, may provide significant benefits for the overall response of a structure in terms of capacity and ductility. However, the bulk of the research on stainless-steel that has been published so far has mostly ignored the analysis of the deformation capabilities of the stainless-steel connections and has mostly focused on the structural response of individual members, such as beams or columns. For such a reason, the present study aims to contribute to the general understanding of the behaviour of stainless-steel connections from a conceptual, numerical and design standpoint. After a brief review of the available literature, the influence of the use of stainless-steel for column–beam connections is discussed from a theoretical standpoint. As a novel contribution, a different approach to compute the pseudo-plastic moment resistance that takes into account the post-elastic secant stiffness of the stainless-steel is proposed. Successively, a refined finite element model is employed to study the failure of stainless-steel column–beam connections. Finally, a critical assessment of the employment of carbon-steel-based design guidelines for stainless-steel connections provided by the Eurocode 3 design (EN 1993-1-8) is performed. The findings prove the need for the development of novel design approaches and more precise capacity models capable of capturing the actual stainless-steel joint response and their impact on the overall ductility and capacity of the whole structure.

Blast fragility assessment of aging coastal RC columns exposed to non-uniform CIC attacks using LBE function

Along the service period of aging coastal reinforced concrete (RC) structures, chloride-induced corrosion (CIC) is a major cause affecting their life-cycle performance and durability. RC columns are the important vertical members of many long-span highway bridges and high-rise buildings, and they are vulnerable to the deterioration effects caused by non-uniform CIC and the intentional terror activities or accidental explosive attacks. The catastrophic failure of RC columns could trigger the progressive collapse of buildings and bridges, leading to huge economic losses and casualties. Very few studies have investigated the time-dependent blast fragilities of deteriorating coastal RC columns exposed to non-uniform CIC. To this end, we proposed an integrated time-dependent blast fragility assessment framework for aging coastal RC columns, considering the deterioration effects caused by non-uniform CIC in marine conditions. Firstly, a three-phase time-variant deterioration rate model for steel bars that considers the accelerated increase of the steel corrosion rate after the cover concrete cracking was incorporated in the analytical modeling of non-uniform CIC of aging RC structures. Secondly, Load-Blast-Enhanced (LBE) function in LS-DYNA was implemented to numerically simulate blast loads, and the effectiveness of the numerical models was validated by the available field blast test results reported in the literature. Subsequently, the performance damage states (e.g., low, medium, and high) of RC columns under intensive blast loads were defined in terms of the damage degree index (D) by using the LBE method, and the pressure-impulse (P–I) models were constructed accordingly. Finally, by using the scaled distance (Z) as the blast loading intensity measure (IM), Monte Carlo Simulations (MCS) were used to conduct the blast fragility analysis for a typical aging coastal RC column. The proposed time-dependent blast fragility assessment framework for aging RC columns is demonstrated to be appropriate and effective in evaluating their deteriorated blast loading-resistance, and it is also a good candidate to estimate the time-dependent blast fragilities of deteriorating coastal RC columns.

Damage and failure of underground subway stations under different soil constraint conditions.

Investigations from past earthquakes have shown that underground subway stations can suffer excessive deformation under strong seismic loads, leading to the damage of critical components and the collapse of structures. This study presents the results of finite element analyses on the seismic damage of underground subway stations installed under different soil constraint conditions. The plastic hinge distribution and damage characteristics of cut and cover double-storey and three-storey subway stations are analyzed using the finite element method software ABAQUS. Combined with the static analysis results of the column sections, a discriminant method for bending plastic hinges is presented. The numerical results show that the collapse of the subway stations begins with the failure of the bottom columns' bottom sections, which leads to the bending of the plates and the destruction of the whole structure. The bending deformation at the end section of columns has an approximatively linear relationship with the inter-storey drift ratio, and the change in soil conditions shows no apparent influence. The sidewall deformation behavior varies significantly under different soil conditions, and the bending deformation at the bottom section of sidewalls increases along with an increase in the soil-structure stiffness ratio at the same inter-storey drift deformation level. The sidewall bending ductility ratio of the double-storey and three-storey stations at the elastic-plastic drift ratio limit increases by 61.6% and 26.7%, respectively. In addition, the fitting curves between the component bending ductility ratio and inter-storey drift ratio based on the analysis results are also presented. The findings may provide a helpful reference for the seismic performance evaluation and design of underground subway stations.

Influence of the tie reinforcement on the development of a collapse caused by the failure of an edge column in RC flat slab system

Influence of the tie reinforcement on the development of a collapse caused by the failure of an edge column in RC flat slab system

Cyclic Behavior of Beam–Column Pocket Connections in GFRP-Reinforced Precast Concrete Assemblages

This paper presents details of an experimental program evaluating the behavior of six half-scale glass fiber–reinforced polymer (GFRP) reinforced concrete beam–column precast members connected together through pocket connections, which are subjected to cyclic loading. The novel beam–column connection was constructed by incorporating either epoxy resin or tensioned or untensioned GFRP rock bolts in conjunction with different-sized pocket connections. The effects of an additional connection bar between the column and beam components in the connection, as well as the confinement of the concrete around the pocket region, were also investigated. An innovative test setup was designed so that the beam–column joint could rotate without restraint provided by the supports. All specimens were tested under an incrementally increasing cyclic load. The load-carrying capacity, deformational behavior, failure modes, energy dissipation, and hysteretic damping were all recorded and evaluated. All specimens failed as a result of column failure within the pocket connection region. This was attributed to the relative rotational flexibility of the column with respect to the beam, owing to the low elasticity of the epoxy resin used in the pocket region, and hence the stress concentration at the column ends within the pocket area. According to the results, a pocket connection containing GFRP reinforcement providing confinement around the embedded area yielded the highest capacity, ductility, and energy dissipation under cyclic loading. The connection containing a GFRP bolt, regardless of whether or not the bolt was prestressed, did not significantly improve the performance of the connection. The findings presented here can be used for the design of precast elements reinforced with GFRP bars. Of particular relevance is application to jetties and other offshore concrete infrastructure where steel reinforcement (because of corrosion issues) needs to be replaced with GFRP reinforcement.

Prediction of column failure modes based on artificial neural network

Prediction of column failure modes based on artificial neural network

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.

Experimental study on the effects of whole heating cycle on post-fire behavior of restrained high strength structural steel columns

This paper presents the results of an experimental study of post-fire behavior and residual strength of restrained high strength structural steel (HSSS) columns, including loading tests of columns at ambient temperature to failure, restrained columns under sustained loading going through heating and cooling cycle in fire and then followed by post-fire loading tests to failure. All the columns were axially restrained in fire. The investigated parameters include with and without rotational restraint, load eccentricity, load ratio and maximum experienced temperature. It was found that if the column failure mode was predominantly overall buckling (columns without rotational restraint in this study), the heating and cooling process would result in a large residual lateral deflection in the column, and the post-fire load carrying capacity of the column would be much lower than without fire exposure. On the other hand, if the column slenderness was low and its failure mode was mainly cross-section yielding (columns with rotational restraint in this study), the post-fire residual lateral deflection was low and the post-fire column would be able to retain a very high proportion of its load carrying capacity without fire exposure, and sometimes even exceeded this value due to strain hardening, which indicated complete reusability of such columns.

Experimental and numerical studies on seismic behavior of new cross square hollow column-truss beam connections

Five cyclic tests on the specimens were conducted to investigate seismic behavior of new cross square hollow column-truss beam connections. The variables are beam, column section size and axial force ratio. The paper reports on the failure modes, hysteretic curves, ultimate load carrying capacity, ductility, energy dissipation capacity, and stiffness degradation of the specimens. Two types of failure modes, i.e., column failure and beam failure mode, were found from the tests. The specimens experiencing the column failure mode exhibit poor seismic performance due to the overall instability induced by the occurrence of the plastic hinge of the column. While, the specimens displaying the beam failure mode exhibit well seismic behavior owing to the redistribution of the plastic stresses among the members of the truss beam. Noteworthy, the failure mode will change from column failure to beam failure when the column thickness increases and the axial force ratio decreases. Additionally, in the beam failure mode, the increase of the column thickness can improve the connection’s bearing and energy dissipation capacity, while the impact of the axial force ratio can be ignored. Based on the test results, the limit value of axial force ratio corresponding to the boundary failure mode under different column thicknesses is determined by using the nonlinear numerical model.

Seismic performance of circular concrete-filled steel tube columns reinforced with inner latticed steel angles

The seismic behavior of circular concrete-filled steel tube (CFST) columns with inner latticed steel angles under combined axial load and reversed cyclic horizontal load was studied in this paper. A total of 8 specimens was tested, including two CFST specimens and six latticed steel angles reinforced CFST specimens. The main parameters studied were the diameter-to-thickness ratio of steel tube, the cross-sectional area of inner latticed steel angles and the axial compression ratio. Firstly, the load-displacement curves and load-strain curves were obtained experimentally; secondly, the failure modes, hysteretic behavior, skeleton curves, stiffness degradation, ductility index, hysteretic energy dissipation capacity were analyzed; thirdly, the seismic performance of the tested specimens were simulated by the established finite element (FE) models, and parametric studies were subsequently performed; finally, the modified calculation method for the horizontal bearing capacity was proposed. The research results showed that the failure of the composite columns was caused by the local buckling of the latticed steel angles and steel tube, and the latticed steel angles could effectively participate in the overall loading process. It was also found that latticed steel angles are able to improve the energy dissipation capacity.

Numerical Analysis on Dynamic Response of CFRP-Wrapped RC Columns under Lateral Impact Loading

This paper presents a numerical study examining the dynamic response and resistance mechanism of reinforced concrete (RC) columns strengthened with or without carbon-fiber-reinforced polymer (CFRP) wraps under lateral impact loading by using the software LS-DYNA. First, the information of eight column models was briefly introduced as part of the laboratory experimental program from the literature. Secondly, finite element (FE) models were established in terms of the geometries of impact tests. Then, a detailed comparison between numerical results and experimental results was made, and FE models showed a relatively high simulation accuracy. Subsequently, a series of parametric analyses were carried out with a focus on the effects of axial compression ratio, the boundary condition at the column top, the layer number of CFRP wraps, and the impact velocity and impact height on the dynamic responses of plain and strengthened columns. The results demonstrated that the CFRP retrofit mechanism was not activated during the initial Stage-I when the impact force rapidly increased to the first peak and then decreased to zero. CFRP strengthening came into play in the second stage, Stage-II, and affected the response of the shear force and moment along the column height, as well as had a great influence on the control of shear damage. The dynamic response of RC columns was more sensitive to the impact velocity than to other parameters, regardless of whether CFRP wrapping was applied. The axial compression ratio would have a different influence on the column failure mode if the impact velocity was varied. The variation in impact height and boundary condition at the column top had little influence on the damage mode of strengthened columns.