Column Shear Research Articles

Prediction of shear capacity of RC columns and discussion on shear contribution via the explainable machine learning

The research goal of this paper is to establish a machine learning (ML) model of shear capacity of reinforced concrete (RC) columns that can reflect the shear mechanism. The main work includes building database, training ML model, and interpretability analysis of optimal model. Aiming at the core problem of interpretability of ML methods, this paper proposes an interpretability method for the shear mechanism of RC columns. An experimental database including 427 sets of results of tests on RC columns is established, and eight salient input features are discerned through both mechanical mechanism assessment and Pearson correlation analysis. Twelve models, consisting of six basic ML models and six ensemble ML models, are verified against the database. The assessment reviews that the Light Gradient Boosting Machine (LightGBM) model was demonstrated to be superior to other models, achieving R2 values of 0.999 and 0.987 in training and test sets respectively. Additionally, compared to five semi-empirical models, the results from the LightGBM model also provides more accurate predictions and adeptly considered the influence of parameters. The Shapley additive explanation (SHAP) method and the explainable method based on the RC column shear mechanism proposed by this paper are used to explain the working mechanism of the LightGBM model. The proposed explanatory method of shear contribution rate is combine the additivity of SHAP value with the additivity of shear component contribution, the proposed explanatory method of shear contribution rate. An evaluation of SHAP feature Importance and SHAP feature dependence revealed that LightGBM aligns closely with the inherent shearing mechanism of the RC column. The shear contribution ratios of the concrete, stirrup, and axial loading in RC columns for the LightGBM model are similar to those predicted based on the semi-empirical models.

Rehabilitation of steel structures using innovative brace members equipped with YSPD damper

Earthquakes are serious risks to human life and infrastructure. An earthquake's influence on human life and its socioeconomic consequences highlight the need to investigate and create the most efficient and easily adaptable ways to minimize losses. The basic concept of different control mechanisms used for protecting structures from the destructive impacts of earthquakes is to dissipate the energy efficiently, therefore ensuring that the structure remains undamaged or sustains minimum damage. To achieve this purpose, the passive control mechanism is a particularly suitable and reliable technology as it doesn't rely on external power to actively dissipate energy. The present study proposes using a passive energy dissipation device called the Yielding Shear Panel Device (YSPD) for strengthening the current steel structures. The YSPD consists of a square hollow section (SHS) that houses a diaphragm plate. The fundamental concept of the YSPD involves harnessing the lateral deformation of a steel plate to absorb and disperse the seismic energy. The Bouc-Wen-Baber Noori (BWBN) material has been used for simulating the hysteresis force-deformation relationship of YSPDs by pinching. YSPDs are simulated as spring components that connect between the beam and the V-brace. A nonlinear time history dynamic analysis was performed to assess the alteration in the structural capacity with the setting up of YSPDs. The performance of the tested structure was assessed considering story drift, story displacement, story shear, column shear, and YSPD hysteresis loops. The results indicated that YSPD installation has improved the structure's capacity. However, the use of dampers resulted in significant drift in all stories, a reduction in total floor displacement, and a decrease in the shear force of the stories. However, the results demonstrated that the YSPD dampers effectively absorbed energy and exhibited stable hysteresis loops.

Modeling of Column Shear Hinges in Pushover Analysis and Experimental Validation

Modeling of Column Shear Hinges in Pushover Analysis and Experimental Validation

Comparison of Seismic and Wind Actions on Medium to High-Rise Buildings in Muscat, Oman

This study is a comparison of wind and seismic loads on medium and high-rise buildings in Muscat, Oman. It uses the proposed Omani Seismic Code and Eurocode EN1991 for seismic and wind calculations, respectively. Muscat falls under Zone-1 in the Omani seismic code and experience basic wind speed of 30 m/sec. The research investigates buildings with varying aspect ratios (1:1 and 1:2), heights (11, 15, and 19 stories), and structural layouts (frame only, core shear wall, and corner shear wall), using ETABS for structural analysis. The findings reveal that seismic actions are generally more significant than wind actions for buildings in Muscat. In frame-only structures, wind-induced base shear ranges from 16%-33% for 1:1 aspect ratio and 21%-43% in the x-direction and 10%-20% in the y-direction for 1:2 aspect ratio, when compared to seismic actions. This difference decreases with increasing building height. Incorporating shear walls notably reduces the maximum lateral displacement across all scenarios, with core-located walls being most effective, leading to a 49% reduction in lateral displacement. Shear walls also substantially mitigate first-story column shear forces and bending moments. The study concludes that seismic actions are more critical than wind actions in Muscat for simple moment-resisting frame systems. Additionally, using shear walls in these buildings is highly beneficial for controlling lateral displacements and reducing member forces.

LOAD VERSUS SETTLEMENT BEHAVIOR OF SOFT CLAY REINFORCED WITH CEMENT STABILIZED RECYCLED ASPHALT PAVEMENT-LATERITIC SOIL COLUMN

In this paper, the performance of cement stabilized recycled asphalt pavement (RAP)-Lateritic column inclusion in soft clay was investigated via a physical model. The load-settlement response and bearing capacity of the composite ground was studied at various cement contents (0%, 1% and 3%) and at 30% RAP replacement ratio. The soft clay was consolidated in the PVC mold in a diameter of 150 mm and 300 mm high while the stabilized RAP-lateritic soil column with a diameter of 50 mm was used as a column at the center of the soft clay. The results showed that the bearing capacity of the composite ground significantly increased with the increased shear strength of column. The purposed bearing capacity equation derived from the unconfined compressive strength of column and undrained shear strength of soft clay was found to predict the bearing capacity of the composite ground satisfactorily.

Seismic response and failure mechanism of ordinary concrete and UHTCC short columns reinforced with negative Poisson's ratio steel bars

The replacement of ordinary steel bars by negative Poisson's ratio (NPR) steel bars to improve the seismic performance of short columns is investigated in this study. NPR steel bars is a new type of reinforcement with negative Poisson's ratio effect and high strength and ductility. In this paper, six short column members were designed. Among them, P-RC1 and P-UHTCC1 short columns were used as controls, and the remaining four specimens were reinforced by NPR steel bars. The failure mode, cracking pattern, hysteresis characteristics, plastic deformation capacity, shear strength, stiffness degradation and energy dissipation capacity of the specimens were investigated through lateral cyclic loading tests. The experimental results showed that the shear capacity of short concrete columns reinforced with NPR steel bars increased by 20.91%−22.64% and the cumulative energy dissipation capacity increased by 45.7%−63.3%. The short UHTCC columns reinforced with NPR steel bars showed an increase in shear capacity of 23.08%−35.48% and an increase in cumulative energy consumption capacity of 17.3%−28.5%. And the RC columns shear strength prediction model based on GB50010–2010 specification is relatively reasonable to be used for the evaluation of shear strength of short columns reinforced with NPR steel bars.

Damage analysis of a pseudoclassic reinforced concrete frame structure under the action of the Ms 6.8 Luding earthquake in China

Reinforced concrete (RC) moment-resistant frame structures are very commonly used worldwide. However, previous earthquakes have revealed the occurrence of strong beam–weak column (SBWC) failure, causing heavy human casualties and economic losses. This study analyzed the SBWC failure mechanism in RC frame structures with the pseudoclassic construction named "Que Ti" near the top of a slope topography, based on the author's recent investigation of the Ms 6.8 Luding earthquake in China. Eight refined finite element models (FEMs) were developed to simulate and analyze the influence of slope topography, pseudoclassic construction, and some structural characteristics on structural damage during an earthquake. Furthermore, discussions on using column-to-beam flexural strength ratios (CBFSRs) to mitigate SBWC failure are presented. The results demonstrated the proposed FEMs effectively simulated the performance of the pseudoclassic structure, especially the SBWC failure mode, as validated by their consistency with the observed structural damage during the earthquake. Moreover, it revealed that structures closer to the slope top experienced amplified ground motions during earthquakes, resulting in more severe damage. In addition, the Que Ti and infill walls increased the vulnerability to column damage and maximum requirement for the column shear force. Finally, to achieve the design objective of a strong column–weak beam (SCWB), the CBFSR should be at least increased to 1.8 for this pseudoclassic RC frame. This ensures a probability of the SBWC failure mode of less than 17% (meet less than 20% of recommendations) and proportion of the beam plastic energy dissipation exceeding 80% of the total plastic energy dissipation. The findings of this study are significant for enhancing seismic design and preventing earthquake disasters for the pseudoclassic structure.

Relationship between diameter and bonding strength in resin/metal interface determined by small resin column shear test.

Relationship between diameter and bonding strength in resin/metal interface determined by small resin column shear test.

Drift-based fragility assessment of nonductile reinforced concrete columns failing in shear under cyclic loading

The paper presents drift-based fragility functions for nonductile reinforced concrete (RC) columns having light transverse reinforcement steel ratio which predominantly fail in shear. These fragilities were developed for four key damage states (i.e., light cracking, severe cracking, shear failure, and loss of axial load carrying capacity) associated with their structural performance observed in laboratory tests and repairability. For this purpose, experimental results of 71 column specimens tested under cyclic lateral loading were collected from 22 research programs; particularly, drift ratios associated to the column specimens tested to reach axial collapse. It is shown that the shear span-to-depth ratio and level of axial load ratio have influence on the drift-based fragilities associated to the damage states considered in this investigation. Additionally, several sources of epistemic uncertainty due to specimen-to-specimen, finite-sample, column shear span-to-depth aspect ratio, and level of axial compression load were quantified from the experimental database. The introduced drift-based fragilities are a very useful tool to assess the expected damage of existing buildings, such as school buildings that might exhibit the short captive column effect.

Damage evaluation of column bases in steel moment-resisting frames based on fishbone model and Bayesian model updating

This paper presents a method of evaluating seismic damage of column bases in steel moment-resisting frames based on fishbone model and hierarchical Bayesian updating method. In this study, a fishbone model considering the flexibility of column bases was presented instead of the traditional fishbone model with rigid column bases and shear building model with unobtainable stiffness of beam ends and column bases. The fishbone model could be used to update the rotational and shear stiffness of column bases, and also to update the stiffness of the beam ends. First, the eigenvalue problem of the fishbone model considering the flexibility of column bases was formulated. Then, the method of identifying the shear and rotational stiffness of column bases in steel frames was proposed based on the hierarchical Bayesian model updating algorithm using incomplete modal data. The seismic damage of column bases was evaluated by comparing the identified stiffness before and after earthquakes. The effectiveness of the proposed method was numerically investigated with a 5-story building model. The influences of the selection of parameters in algorithm, structural modal data and degrees of freedom on the identified results were studied. Finally, the applicability of the method to realistic damage evaluation of column bases was also examined by a serial of shaking table tests on a 3-story 2-bay large-scaled steel frame specimen.

An innovative model to estimate the tension field inclination considering crack growth for steel plate shear wall

The Steel Plate Shear Walls (SPSWs) are known as a capable system to use in steel structures due to their significant advantages. Despite extensive studies concerning this system, few researchers have scrutinized thecrack effect on SPSW behavior. However, the crack dramatically affected the experimental results. In the currentpaper, the effect of central and edge cracks, therefore, has been studied in jointed plates at mid-height of SPSW.Results indicated that the central crack is more destructive than the edge crack. The central crack having a long initial length also makes a sudden wall fracture in the elastic zone and consequently cannot be used in high seismic regions. Due to the dependence of the wall on the diagonal tension field and its angle, an equationis proposed taking into account shear, axial, and moment actions in columns, axial and moment actions in beams, as well as shear and axial actions in the plate which conform to finite element results. Because of thecomplication of the stress intensity factor for mode I and mode II calculations, this confidence is derived and offered.

Study on the RC Frame with the Partial Infill Wall in Pushover Analysis

The short column effect is a major contributor to structural failure during seismic events. However, while most investigations concentrate on its influence on external walls, it also causes damage to interior walls. This underscores the significance of exploring interior wall damage due to this effect. This study involves four variations of RC frames with infill walls, analyzed using the Pushover method within the SAP 2000 software. The Pushover analysis vividly portrays the behavior and performance of interior wall systems. A comprehensive comparison of metrics like base shear, column shear force, and plastic hinge behavior underscores the pivotal role of interior walls in the entire structure, accentuating the necessity of delving into interior wall research.

Ultra-High-Toughness Concrete Retrofitted Boundary Column Shear Walls: Tests and Capacity Prediction

Ultra-High-Toughness Concrete Retrofitted Boundary Column Shear Walls: Tests and Capacity Prediction

Performance evaluation of low-rise infilled reinforced concrete frames designed by considering local effects on column shear demand

Performance evaluation of low-rise infilled reinforced concrete frames designed by considering local effects on column shear demand

Multimode Free-Vibration Decay Column: Small-Strain Stiffness and Attenuation

This study presents a simplified resonant column testing method to obtain small-strain dynamic properties of soils in both torsional and flexural vibrations. The method exploits free vibration decay responses of the system produced by manual excitation while the specimen is subjected to an isotropic effective confining stress produced by a vacuum pressure. This method is readily applicable to standard resonant column and torsional shear devices and triaxial cells by attaching a metal bar with one or two accelerometers for manual excitation, but not using an electromagnetic driving plate. This paper describes the apparatus design, test procedure, system calibration, and data analyses, as well as the test results of dynamic properties of a dry sand, including small-strain elastic moduli and damping ratios obtained from the torsional and flexural modes. The results confirm that the suggested method can capture strain-dependent characteristics up to the strains of ∼10−4 beyond typical elastic threshold strains, although the isotropic effective confining stress is limited to ∼90 kPa. This unique testing method provides remarkably consistent and reliable measurement for the dynamic properties of soils, and it avoids any possible bias from the counterelectromotive force.

Control of vibrations in high-rise structures using base isolation technology

Vibrations pose a threat to the structures and diverse construction models, including space stations and enormous mechanical carriers. In the case of low-rise structures, seismic vibration generates bottom shear in columns. The base isolator is capable of mitigating shear deformation, but the use of isolators alone in skyscrapers can result in flexural deformation of the entire structure when vibration is applied. Seismic waves can generate amplitude with increasing wavelength, resulting in horizontal deflection and warping. This bending and deflection can be mitigated with dampers that aid in the loss of energy. To prevent excessive vibrations from being transmitted to the superstructure, isolators must be provided. In this study, the base isolator model is optimized and implemented as a tension integrity suspension isolator. The effectiveness of the isolator was observed by an experimental investigation of sloshing of waves in a water tank. As a test model, the performance of the isolator is evaluated on a model of a wooden high-rise structure. Using the fast Fourier transform algorithm and the vibration analysis software Kampana, effective results were obtained.

Analysis of the handling and preparation of samples in the resonant column and cyclic torsional shear equipment

In many geotechnical applications, the shear modulus G is the one that governs the dynamic behaviour of the soil, and many fields and laboratory methods are focused on calculating it. This is the case of the resonant column and cyclic torsional shear tests, which allow both the modulus G and the damping D to be obtained in different strain ranges. These laboratory tests are carried out in a triaxial cell and in both tests, torsion is applied to the upper part of the specimens, which has allowed new commercial devices to group both techniques in a piece of a single equipment. The combination of the two tests makes it possible to obtain the dynamic properties of the soil over a wide range of strains, 10-4≤γ≤1%.Due to the small strains reached in these tests, less than 1%, the correct preparation of the specimens and their mounting in the triaxial cell are factors of vital importance for the reliability of the test results. In undisturbed samples, the sample should be handled, and the specimen carved with special care, trying not to alter the structure of the original soil. For remoulded clay specimens, static compaction in an external press and subsequent mounting on the triaxial cell pedestal are recommended. Saturation can present difficulties, as in these tests drainage and saturation can only be carried out from the bottom of the specimen. Consolidation times can be long. Sand specimens should be made by placing a mould on the pedestal of the triaxial cell and applying a vacuum. The method of freezing the specimen is discarded due to the long assembly time.

Behaviour and design of monotonically loaded reinforced concrete external beam-column joints

This paper describes an experimental investigation into the influence of beam reinforcement detailing, column axial load and shear reinforcement on the joint shear strength of reinforced concrete external beam-column connections. A series of twelve external beam-column joint specimens were tested in three groups of four specimens. Series 1 investigated the influence of beam reinforcement anchorage type and bend radius. Series 2 studied the influence of column axial load on joint shear strength while series 3 studied the influence of intermediate column bars and joint shear reinforcement. The paper presents the experimental results and describes the influence of the considered variables on joint shear strength. Three existing empirical design equations for external beam-column are evaluated using data from this program and previously tested beam-column joint specimens. Finally, design recommendations are made.

Thermal Effect on the Design Loads of Multi-Storey RC Buildings on Sloped Terrain in Saudi Arabia

Abstract This research investigates the impact of thermal loads on reinforced concrete (RC) buildings in Saudi Arabia and how they behave on sloped terrain. The study analyzed the effects of different types of support systems (hinged and fixed supports) and strengthening systems (with and without bracings) using the software ETABS-V20. Ground + 9 typical floors frame RC models on sloped terrain subjected to seismic loads were used for the investigation. The dynamic analysis of the ETABS models was performed to evaluate the lateral displacement, storey drift, column shear forces, and base shear forces of the buildings. The study found that using a bracing system and fixed supports under seismic loads increases the model’s displacement and storey drift compared to models with hinged supports and no bracing system. The maximum shear forces values were also higher for models with bracing systems and fixed supports, while the minimum values were for models without bracing systems and with hinged supports.

Performance-Based Assessment of RC Building with Short Columns Due to the Different Design Principles

Many factors affect the earthquake vulnerability of reinforced concrete (RC) structures, constituting a large part of the existing building stock. Short column in RC structures is one of the reasons for earthquake damage. Significant damages may occur due to brittle fractures in structural elements when the shear resistances are exceeded under the effect of high shear stress in short columns formed due to architectural and topographic reasons. This study created structural models for three situations: the hill slope effect, band-type window and mezzanine floor, which may cause short column formation. The structural analyses by SAP2000 were compared with the reference building model with no short columns. Structural analyses were performed separately according to strength-based and deformation-based design approaches in the updated Türkiye Building Earthquake Code (TBEC-2018). Short column formation; the effects on soft-storey irregularity, the relative storey drifts, column shear force, plastic rotation in columns, roof displacement, base shear force and column damage levels were investigated. As a result of the analysis, it was determined that the relative drifts from the first floor of the building decreased significantly due to the band-type window and slope effect, which caused the second storey to fall into the soft-storey status. In addition, short-column formation caused a significant increase in both plastic rotation demand and shear force in short columns.