Shear Failure Of Columns Research Articles

Experimental and simulation research on rupture behavior of coal-based solid waste material backfilling column under non-uniformly distributed load with different loading ratios

Artificial construction backfilling columns underground based on coal-based solid waste materials is an important method to slow down surface subsidence and reduce the environmental pollution caused by coal gangue hills and fly ash. Taking the Xinyang coal mine as an example, based on a self-developed non-uniform load application device, acoustic emission (AE) and digital image correlation (DIC) monitoring technology, the evolution law of rupture behavior of coal-based solid waste material backfilling columns under different loading ratios was revealed. When the loading ratios are 1, 1.1319, 1.3585, 1.6371, and 2.0631, the average compression strength with the same material ratio is 3.96 MPa, 4.05 MPa, 4.22 MPa, 4.57 MPa, and 3.94 MPa, respectively. It is indicated that an increase in the loading ratio within the critical range is beneficial for stimulating the collaborative bearing of different parts inside the backfilling columns. From the perspective of the internal rupture behavior of the backfilling columns, the increase in loading ratio promotes a significant increase in the proportion of shear cracks, which has increased from 17.07% to 37.02%, resulting in the shear failure of backfilling columns. Meanwhile, as the loading ratio increases, the crack initiation position gathers from the left and right sides to the middle, and the final crack shape gradually transitions from two inclined and parallel main cracks to an inverted "V" shaped intersecting main cracks. The research is of great significance for improving the understanding of the failure law of backfilling columns and the safety evaluation of engineering-bearing structures under non-uniform loads.

Shear capacity model of rectangular RC columns based on Bayesian update

Reinforced concrete (RC) columns are function as structural member resisting vertical loading. The combined effects of vertical loading and transverse loading might induce shear failure of RC columns, posing a significant threat to the structure's integrity. While the accuracy of existing models to determine the shear strength of RC column is crucial for design, there is a need for further refinement. In this context, a study introduces a probabilistic shear capacity model based on the truss-arch theory and incorporating the Bayesian theory Monte Carlo Markov Chain (MCMC) method. This model delineates the shear contribution into four distinct components: concrete, stirrup, axial compression force and longitudinal reinforcement longitudinal reinforcement in the middle of the section parallel to the loading direction. A database, comprising 233 RC column specimen sets, facilitates the model's regression analysis. Calibration is achieved against the density distribution and confidence intervals of the posterior parameters. When set against four established models, the new proposal offers a mean value closely aligned with experimental data and showcases reduced variance. To substantiate the shear mechanism of the proposed model, a thorough contribution of each shear component's contribution is made with those in four existing models: Sezen, ACI 318, Priestley, and GB50010. While the Sezen and ACI 318 models recognize the shear contributions of concrete and stirrup, the Priestley and GB50010 models extend to factor in the beneficial impact of the axial compression force component. Comparative analysis underscores the superior predictive capability of the newly proposed model.

Asymmetric seismic pounding between multistorey reinforced concrete structures in a city block

Usually within city blocks land ownerships are not equal and exhibit various geometries. Therefore, it is most probable adjacent structures to be partly and in an asymmetric way in contact. Consequently, buildings asymmetrically restrained in lateral displacements during earthquake excitations carry out torsional oscillations. The interaction of an 8-storey reinforced concrete frame building designed according to Eurocodes with an adjoining structure for various parameters is thoroughly investigated. The 8-storey frame is considered with pilotis configuration and fully infilled whereas the other structure is studied for the cases of 6-stories, 3-stories and single storey. Further the two interacting structures form an L-shape plan and are studied for three cases of asymmetric contact, whereas two natural seismic excitations each one applied in two directions (positive – negative). Thereupon, for the thorough study of the problem more than 100 pounding pairs for structures having equal storey levels (floor-to-floor pounding) and 100 pairs for structures having unequal storey levels (floor-to-column or interstorey pounding) have been investigated. The whole study highlights crucial aspects of the issue such as the unfavourable role of pilotis configuration, the significant torsional vibrations induced and the almost inevitable shear failure of columns that suffer an impact by an adjacent building within their deformable height.

Seismic retrofit of URM-infilled RC frames by the steel-jacketed hybrid walls

The present study aims at using the hybrid wall technique to prevent the occurrence of shear failure of the reinforced concrete (RC) columns in the unreinforced masonry walls (URMs) infilled in the RC frames and to increase their lateral strength, stiffness, and ductility. The hybrid wall integrates a boundary RC column with its adjacent URM infill with the help of jacketing steel plates, to make them perform as a unified member. Two series of experimental tests, including one element test (RC column with URM wing-wall) and five frame tests (one-bay one-story RC frames with URM infills), were conducted under reversed cyclic loading. The interaction between the masonry infill wall and the boundary RC columns before and after retrofitting by the hybrid wall technique is studied, and a corresponding design framework is suggested. The experimental results of the retrofitted frames demonstrated not only enhancing lateral strength, stiffness, and ductility of the URM-infilled RC frames but also the prevention of the shear failure of the boundary RC columns and postponement of the occurrence of the URM infills’ failure to larger drifts. The columns’ shear failure is a significant concern due to infill-column interaction in URM-infilled RC frames. However, one of the important impacts of the thick hybrid walls is that the boundary RC columns remained undamaged even in large lateral drifts due to flexural behavior. From the viewpoint of applicability, the thick hybrid walls technique does not require relocation of occupants and does not disturb RC buildings’ operations during construction. Moreover, it is not a labor-intensive technique.

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.

Pseudo-static tests of reinforced concrete pier columns confined with pre-tensioned superelastic shape memory alloy wires

To enhance the seismic performance and self-centring capacity of reinforced concrete (RC) pier columns, a novel self-centring shape memory alloy (SMA) wire-confined–RC-composite column was proposed and experimentally tested in this study. One common RC-pier specimen and eight SMA-wire-constrained–RC-pier specimens were constructed for experimentation. The effects of the axial-compression ratio, SMA pre-strain level, and SMA configuration rate on the seismic performance of the RC piers were investigated. The failure mode, hysteresis curve, skeleton curve, bearing capacity, ductility, stiffness, energy-dissipation capacity, and self-centring capacity of the novel column are illustrated and discussed. The test results show that, compared with the shear failure of normal RC-pier columns, the failure mode of the SMA-wire-confined–RC-pier columns were transformed into bending failure or bending-shear failure with certain ductility. With an increase in the SMA-wire configuration rate, the shear bearing capacity, ductility, energy-dissipation capacity, and self-centring capacity of the RC-pier columns were improved. Pre-tensioned SMA wires were attributed to the earlier activation of force restraint and provided a greater binding force, providing more shear restraint and improving the deformation capacity of the core concrete. The ductility and bearing capacity of the strengthened specimens decreased with an excessively large axial-compression ratio; however, they were higher than those of unreinforced specimens. The research results provide new ideas and an experimental basis for the external strength gain and rapid recovery of existing RC piers after an earthquake.

Strengthening method by using ultra-high-strength fiber-reinforced concrete panels for a column on the soft first story of a reinforced concrete building

This paper presents a simple and efficient strengthening method by using ultra-high-strength fiber-reinforced concrete (UFC) panels on the soft first storys of reinforced concrete (RC) buildings at the risk of story collapse or shear failure of column due to earthquakes. Five 1/3 scale specimens, which replicated RC columns on the soft first story of a 10-story condominium building heavily damaged by the 2016 Kumamoto Earthquake, were constructed and tested. One of these was a reference specimen (no strengthening), and the other four were strengthened by attaching UFC panels on the two faces parallel to the assumed loading direction with or without an UFC or a RC wing wall on either column side. Cyclic lateral and varying axial loads were applied to the specimens to emulate earthquake loads. Load–deformation hysteretic responses, failure modes, and the responses of the UFC panels and the wing walls, are discussed in detail. The experimental results revealed that the reference specimen (without strengthening) had a low-load-carrying capacity and exhibited brittle shear failure, as observed in the actual building during the earthquake. Conversely, the strength and deformation capacities of the strengthened specimens improved considerably, and the effectiveness of the proposed strengthening method was validated quantitatively.

Seismic fragility of lightly reinforced concrete school building typologies with different masonry infill configurations

This paper presents the outcome of a research study conducted to establish seismic fragilities of school building typologies in Sri Lanka. The school buildings in Sri Lanka can be characterised as lightly reinforced concrete (RC) buildings, infilled with masonry walls (IMW). However, they are categorised into two typologies based on the structural layouts used (1) Type 1 (T01) and (2) Type 2 (T02). Although, the school buildings can be grouped into two typologies, variabilities in terms IMW configurations and their arrangements are observed among those school buildings. These variabilities in terms of building typologies as well as IMW arrangements were taken to establish seismic fragility curves. The seismic performances of the school buildings were numerically assessed, where in total 640 building cases were analysed by varying typologies, IMW configurations, and stochastic material properties. Since, the RC school buildings are lightly reinforced, a simplified, yet a novel approach was followed to account the shear failure of RC columns under seismic actions. Then, four damage thresholds were established (slight, moderate, severe and collapse) and the corresponding fragility curves are presented in terms of school building typologies considered. Finally, based on the fragility curves, damage probability matrices of the building typologies were established.

Rapid report of seismic damage to buildings in the 2022 M 6.8 Luding earthquake, China

The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province, China. They include base-isolated buildings, multi-story reinforced concrete (RC) frame buildings, and masonry buildings. The near-field region is known to be tectonically highly active, and the local intensity level is the highest, that is, 0.4g peak ground acceleration (PGA) for the design basis earthquake, in the Chinese zonation of seismic ground motion parameters. The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy. The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings. It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement. Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field. However, careful forensic analyses are needed before any conclusive judgment can be made.

Effectiveness of Lateral Load Resisting Systems for Open Ground+20 Storied RC Framed Structure

Abstract: In a highly populated country like India, problem of parking of the vehicles arises, this problem leaves no option for design of open ground storey buildings. Since there are no infill walls in ground storey, stiffness in the upper storey is much more than the ground storey. The columns in the ground storey are heavily stressed, therefore it is required that the ground storey columns must have sufficient strength and adequate ductility, the increased base shear is resisted entirely by the columns of ground storey only. These buildings are vulnerable due to the sudden lowering of stiffness and strength in the ground storey. This results in the attraction of more earthquake forces for the lower time periods, which also results in snapping of lateral ties in column, crushing of core concrete, buckling of longitudinal bars and finally shear failure in open ground storey columns due to lateral earthquake forces. Solution for this problem is to prevent the failure of open ground storey columns due to lateral earthquake forces by providing the lateral load resisting system. Many times, stiffness of walls is not considered while designing, this results in inaccurate designing of elements. An Open Ground +20 storied RC frame subjected to strong motion earthquakes viz. Duzce in Turkey (12/11/1999), Erzincan in Turkey (13/03/1992), Imperial valley at El-centro (19/05/1940), Landers (28/06/1992) and Nahanni in Canada (23/12/1985) creating soft storey effect at ground storey so it should be provided with lateral load resisting systems viz, Shear wall, steel bracing, lead rubber bearing base isolator with different configurations. Performance of equivalent diagonal strut provided to structure is compared with brick work modelled as actual brick work, equivalent diagonal struts, and considering only the mass of brick work. Time History Analysis is used in a RC framed building using ETABS Version18 and SAP2000 Version20 software in comparison with Response quantities Roof displacement, soft storey check, Base shear, overturning moment and storey drift. In this research, equivalent diagonal struts are provided as brick masonary, which shows accurate behavior of structure under strong ground motions as mass and stiffness both are considered during analysis. When Open ground storied structure is subjected to strong ground motions, stiffness at ground storey is drastically reduced. When structure is assigned with Lateral Load Resisting Systems, shear wall with configuration shear wall at ground storey and 1st storey, stiffness at ground storey is increased to 81% and 82% in X and Y direction respectively within permissible limits. Hence it can be concluded that when there is soft storey effect at open ground, structure becomes hazardous in presence of strong ground motions. When structure is subjected to strong ground motions, the vulnerability condition is high. Since we have performed non-linear dynamic time history analysis, more accurate results can be obtained as non-linear analysis considers vertical irregularities

Simulation of Shear Capacity of Reinforced Concrete Column with Variation of Stirrups Using Finite Element Method Analysis

Shear failure of column causes the column to have shear reinforcement that cannot withstand shear forces so that it loses of lateral strength quickly. This research aims to see the effect of the configuration with the addition of shear reinforcement in the direction and perpendicular to the direction of the shear force on the capacity of reinforced concrete columns that are loaded with axial and lateral loads. The test was carried out by providing a constant axial load (0.3 P0) followed by a shear load until the test object failed. The numerical analysis was carried out using software based on the finite element method, namely ATENA Version 5 and GID Version 13.0.1 developed by Cervenka Consulting. This study used reinforced concrete with three variables of shear reinforcement. It can be the normal columns without stirrup reinforcement (S0P2), the addition three (3) stirrups in the direction of the shear reinforcement (S4P2) and the addition of two (2) stirrups in the direction of the shear reinforcement and one (1) stirrups perpendicular to the shear reinforcement (S5P2). After the numerical analysis is carried out, the results are verifies using experimental testing. The numerical analysis and experimental results give the load and deflection relationship results that are almost close. Therefore, the difference in shear loads compared to the experiments results and numerical analysis on columns S0P2, S4P2, and S5P2 is 0.11%, 3.95% and 1.16%, respectively, with a deflection ratio of 4.72%, 37.80% and 9.44%. The pattern of column destruction in the numerical model resembles the destruction pattern of the experimental results, both of which indicate that the column has shear cracks.

Nonlinear truss modeling method for masonry-infilled reinforced concrete frames

This paper presents a new modeling approach for masonry-infilled, reinforced concrete (RC) frames, based on the nonlinear truss analogy. The unreinforced masonry infill walls are modeled with truss cells containing horizontal, vertical and inclined elements. Zero-length macroelements are also used to account for the localized damage on mortar joints. The frame members are modeled with a recently proposed scheme that can account for inelastic response and can capture the effect of shear damage and failure of RC columns. The modeling approach is validated through analysis of experimentally tested masonry-infilled frames, and its capability in capturing the strength and damage patterns is evaluated. A sensitivity study is also provided, to elucidate the impact of several model parameters on the obtained analytical results.

Study on Numerical Simulation of Seismic Collapse of RC Frame Structure with Infilled Wall

The infilled wall plays an important role in the formation of the survival space and life‐saving passage of the seismic collapse of reinforcement concrete (RC) frame structure. Here, with the numerical modeling method of the infilled wall, the connection between infilled wall and RC frame was primarily investigated. The combined finite element (FE) and finite‐discrete element (F‐DE) method is proposed to simulate the multispan and multistory RC frame structure with infilled wall. The reliability of the numerical simulation method was verified by the shaking table test; the evaluation criterion includes the collapse mechanism and mode. The results show that the numerical simulation is highly consistent with the shaking table test; it is easy for RC frame structure to form short columns due to the influence of the low or half‐height infilled wall, and the structural collapse is caused by the shear failure of columns; the overall structure shows pancake type of collapse; the survival space becomes smaller and smaller on the direction of structural collapse. The proposed numerical simulation method can be valuable in simulating RC frame structure with infilled wall for postearthquake rescue.

Experimental investigation on monotonic bending behaviour of TSOBs bolted beam to hollow square section column connection with inner stiffener

In the reported research results on T-head Square-neck One-side Bolts (TSOBs) bolted Endplate Connection (TSOB-EC), the failure of TSOB pulling-out due to the punching shear failure of Hollow Square Section Column (HSSC) wall is typical, which should be avoided. Two types of inner stiffeners that have H-section and double channel section are used to improve the punching shear resistance of the HSSC wall. At the same time, the inner stiffeners are used as connection splices to connect the upper column and the lower. The effect of the length and plate thickness for the stiffener on the connection performance are also studied. A total of six TSOBECs with stiffeners were tested under monotonic bending moment. The test results show that the stiffeners can avoid the bolt pulling-out failure and improve the deformation capacity of TSOBEC. The yield bending moment and peak bending moment of TSOBEC can be increased by 8.1%∼31.8% and 11.6%∼21.7% by double channel stiffeners, respectively, and improved by 69.3%∼72.6% and 22.5%∼39.4% by H-steel stiffeners, respectively. The analytical models for predicting the bending moment capacity of TSOBEC with stiffeners are proposed and the prediction results are accurate with an error within 5%. In addition, extended H-steel stiffener is recommended for designing the strengthened TSOBEC, and the cross-section of the stiffener needs to be calculated by the proposed models to ensure that the H-steel stiffener and HSSC do not deform even if the joint fails.

Dynamic Response Characteristics that Lead to Direct Shear Failure in Blast-Loaded Columns

Blast-loaded structures respond dynamically to impulsive loads generated by an explosion. Individual components must possess adequate flexural and sectional shear capacity to survive such extreme loads. Unlike static loads, blasts can cause a unique limit state known as direct shear failure, which occurs early in the response history of a blast-loaded member. While various researchers have observed this phenomenon in past testing, the fundamental mechanics underlying this behavior are not completely understood. Multiple analysis approaches for capturing direct shear behavior of blast-loaded members have been proposed in the research literature, suggesting that further study is needed to understand this phenomenon. In this paper, direct shear response is explored in detail, demonstrating that this behavior originates from high-frequency contributions that are often neglected in modal analyses or misrepresented as a feature of traditional flexural response in single-degree-of-freedom analyses.

Seismic design method for preventing column shear failure in reinforced concrete frames with infill walls

The presence of masonry walls has a significant effect on the seismic response of structures. The infill panels can increase the overall lateral stiffness and strength of structures. This increase in strength and stiffness is normally beneficial to the overall seismic resistance unless the presence of masonry walls creates an irregularity in the structure or the infill-frame interaction induces excessive forces in the frame, leading to local failure. This study evaluated a proposed design method to prevent local shear failure of RC columns due to infill-frame interactions. The proposed method is based on local plastic mechanism analysis of the column considering the variation in the column shear demand and column shear capacity at different deformation states. Simplified equations based on the equivalent strut concept together with finite element analysis (FEA) are used to determine the demand of the surrounding frame due to infill-frame interaction and to assess key response parameters for the design. An RC frame with a concrete block masonry wall was designed with the proposed method and tested under cyclic loading. The test showed that local failure of the surrounding frame could be prevented, resulting in a ductile behavior. Only horizontal cracks were observed at the ends of the frame members, indicating only the flexural yielding. Finally, since a large variation in the infill wall strength may exist, the implementation and limitations of the method are also discussed.

Investigating the reliability of shear strength equations in TS500 and ACI318-19

Lateral loads (e.g., wind and earthquake loads) lead to shear forces as well as the axial loads and moments on the structural members. Although reinforced concrete (RC) columns are commonly assumed as slender members and are not expected to represent shear dominant response characteristics, experimental studies have shown that even slender columns have shear responses. Hence, in seismic design, the shear strength of columns must be accurately predicted to prevent shear failure of columns. Validation of Requirements for Design and Construction of RC structures (TS500) for shear strength calculation of RC columns by a broad range of test data has been neglected in the literature. In this study, 57 test results of rectangular RC columns were collected from available laboratory tests to verify the shear strength calculation approach in TS500. Additionally, a statistical comparison of results obtained from TS500 with Building Code Requirements for Structural Concrete (ACI318-19) has been studied in this study. Maximum shear strength of RC columns obtained from the previously studied test data was compared with shear strengths calculated according to TS 500 as well as with the results obtained from ACI318-19. Comparisons are scrutinized in terms of shear-span-to-depth ratios, reinforcing ratios, material properties, and stirrup spacing as well as axial load ratios applied on top of the columns. Investigation of existing design equations reveals a significant difference in prediction. This study will be extended by adding further test results from the literature to provide crucial comments about the shear strength calculation of RC columns in TS500.

Bayesian Theory-Based Seismic Failure Modes Identification of Reinforced Concrete Columns

ABSTRACT The aim of this research is to develop a probability method that can identify the flexure, shear or flexural-shear failure of RC columns. A total of 336 columns of cyclic load test results were collected, and a probabilistic model was constructed using the Bayesian procedure. Then, the model was simplified by Bayesian updating. The boundaries for each failure mode were selected through an internal search optimization. The results show that the Bayesian methodology can accurately predict the seismic failure modes of RC columns and the comparison of the identification with other methods underscore the validity of Bayesian method.

Experimental study of jacket height and reinforcement effects on seismic retrofitting of concrete columns

This study evaluates the jacket height and reinforcement effects on reinforced concrete (RC) square columns retrofitted with normal concrete. Five one-third scale columns with non-ductile reinforcement were tested. Four columns were retrofitted with RC jackets with quarter height (h/4) and half height (h/2) where h is the column height. Subjected to cyclic loading, the failure pattern, lateral load capacity, stiffness, ductility, and energy dissipation of the column were investigated. Results show that increasing the jacket height significantly affected the failure pattern and lateral load capacity. Increasing the jacket height from h/4 to h/2 showed a pronounced shear failure and steeper diagonal cracks. Columns jacketed with h/2 jacket almost doubled the original lateral load capacity. The difference in the lateral load capacity of columns with h/2 jackets and h/4 jackets was above 23%. The jacket reinforcement confinement reduced the level of jacket damage and increased the damage and concrete crush in the column above the jacket. However, the unreinforced jacket increased the jacket damage and reduced the damage above the jacket. The jacket reinforcement increased the lateral load capacity by the shear transfer mechanism while the jacket height enhanced the energy dissipation of the jacketed columns by arch (strut) action. In addition, the jacket height and reinforcement increased the column’s stiffness and consequently, the stiffness irregularity produced short column shear failure above the jacket. From the results, a simplified analytical model was developed to predict the structural capacities of the jacketed column.

Influence of exterior infill walls on the performance of RC frames under tsunami loads: Case study of school buildings in Sri Lanka

This paper assesses the structural performance of RC frame buildings subjected to tsunami-induced loads, accounting for the influence of exterior masonry infill walls on the overall structural performance. Both the in-plane and out-of-plane contributions of masonry infill walls are considered in the analysis. To illustrate the importance of accounting for exterior infill walls in the response of structures to tsunami, two case study buildings are considered and modelled in 3D. The first case study is a typical two-storey school building in Sri Lanka, and the second is a modified version of this design configuration proposed in Sri Lanka after the 2004 Indian Ocean Tsunami to provide more redundancy against scour. Through these case studies, the effect of the non-uniform distribution of infill walls in the building and their failure (or “breakaway”) on building performance is considered. The building performance is characterized by a number of response parameters (i.e., first yielding, development of two hinges, and shear failure in ground floor columns). The paper shows that the in-plane behaviour of exterior infill walls increases the flexural capacity and lateral stiffness of the structure, as would be expected. However, it also shows that an assumption of non-breakaway infill walls consistently leads to premature structural failure mechanisms, associated with the concentration of drag forces on seaward columns only. The results demonstrate that a good estimation of the location and occurrence of shear failure in structural elements can only be achieved by explicitly considering the out-of-plane behaviour and failure of exterior infill walls during an incremental tsunami load analysis. Finally, the Froude number assumed for the analysis is seen to strongly affect the performance of both structural and non-structural components, highlighting the importance of choosing realistic tsunami properties to perform a reliable capacity assessment.