Reinforced Concrete Short Columns Research Articles

Seismic response of RC short columns strengthened by high-strength stainless steel wire rope meshes reinforced ECC jacket

A novel strengthening scheme of high-strength stainless steel wire rope (HSSSWR) meshes reinforced engineering cementitious composite (ECC) jacket was used to strengthen the reinforced concrete (RC) short columns in this paper. The seismic performance of short columns after being strengthened was investigated, considering the changes in the strengthening scheme, and the spacing of lateral HSSSWRs. The failure mode, hysteresis behavior, envelope curve, ductility, energy dissipation, stiffness degradation, and strength degradation were introduced specifically based on the analysis of six full-scale short columns. The test results show a significant enhancement in the seismic performance of the strengthened short columns, especially in ductility and energy dissipation, which were increased by 49.4–98.4 %, and 149.3–713.2 %, respectively. The placement of HSSSWRs in ECC jacket proved to be effective in enhancing the strengthening effect of the jacket. A prediction model for the shear capacity of the strengthened columns was proposed using the Modified Compression Field Theory (MCFT), and the predicted results were in good agreement with the test results presented in this paper and in relative study.

Field Reconnaissance and Earthquake Vulnerability of the RC Buildings in Adıyaman during 2023 Türkiye Earthquakes

The 6th February 2023 Pazarcık and Elbistan earthquakes (Mw = 7.7 and Mw = 7.6) caused great destruction in many cities and were the disaster of the century for Türkiye. The greatest destruction was caused in the provinces of Hatay, Kahramanmaraş, and Adıyaman during these earthquakes, which were independent of each other and occurred on the same day. Information about earthquakes and strong ground motion records is given within the scope of this study. Reinforced concrete (RC) structures which constitute a large part of the urban building stock in the earthquake region were exposed to structural damage at different levels. The structural damage in the RC structures in the city center, Gölbaşı, and Kahta districts of the province of Adıyaman was evaluated within the scope of earthquake and civil engineering after field investigations. Insufficient RC, low-strength concrete reinforcement problems, RC frame failure, heavy overhang, short columns, soft story, and pounding effect are the main causes of the earthquake damage. The presence of these factors that reduce the earthquake resistance of RC structures increased the damage level. In addition, the fact that the earthquakes occurred nine hours apart and the continuation of aftershocks during that period negatively affected the damage levels. It has been observed that structures that receive the necessary engineering services during the construction and project phases ensure the safety of life and property, even if the structure is slightly damaged. In this study, we also tried to reveal whether the target displacements were satisfactorily represented by numerical analysis for a sample RC structure.

Delaying the Occurrence of Bar Buckling in RC Columns Confined with SRG Jacketing

This paper investigates experimentally the structural performance of substandard reinforced concrete (RC) short columns confined with steel-reinforced grout (SRG) jackets under monotonically increasing uniaxial compression. The study comprised 24 square cross section short RC columns having alternative arrangements of shear reinforcement (ratio of stirrup spacing to longitudinal bar diameter ranging from 4.2 to 12.5). The short columns were retrofitted with externally applied SRG jacketing differing by the density of the fabric (4 cords/in and 12 cords/in) and the number of fabric layers (1 and 2). The test results showed that retrofitting significantly changed the behaviour of the specimens compared to the unconfined counterparts. For columns at risk of premature failure due to insufficient support of compression bars provided by the sparse stirrups, the SRG jackets delayed bar buckling, enabling the members to achieve greater strength and deformation capacity. The well-detailed specimens helped establish the maximum effectiveness of SRG confinement.

Nonlinear behaviour of corrosion damaged low-strength short reinforced concrete columns under compressive axial cyclic loading

New codes have recently introduced seismic detailing for new structures. However, there are still older reinforced concrete (RC) structures without proper ductile detailing for earthquake resistance in seismic-prone areas. These structures are further impacted by the corrosion of their embedded reinforcing bars, which further reduces the strength and ductility under axial cyclic loading. This paper summarises the results of an experimental investigation performed on low-strength short RC columns, with different confinement configurations, subject to varying degrees of corrosion to investigate their structural responses to axial cyclic loading. The experiment was conducted on 30 short RC columns (square and circular) with three levels of confinement and steel reinforcement corrosion loss ranging from 0% to ∼ 30% subjected to cyclic compressive loading. The test results show that corrosion and inadequate confinements have a significant negative impact on the structural responses of corroded columns.

Finite element modeling of square high-strength concrete short columns longitudinally reinforced with steel equal-angles under axial loading

Conventional steel bars in Reinforced Concrete (RC) square columns are utilized as longitudinal reinforcement and steel ties are utilized as transverse reinforcement for concrete confinement. The concrete confinement in RC columns with square section is less than that with circular section. Recently, Steel-Equal Angle (SEA) as longitudinal reinforcement has been investigated for square RC columns. The RC columns with SEA as longitudinal reinforcement exhibit higher strength and ductility than the RC columns with conventional steel bars as longitudinal reinforcement. However, experimental and computational investigations have been very limited on RC columns with SEA as longitudinal reinforcement. Existing studies investigated only the effects of lateral tie spacing on the performance of RC columns reinforced with SEA sections. However, the effects of the other important column parameters, such as the width and thickness of SEA sections, yield stress of SEA sections, and the concrete compressive strength, on the axial performance of RC columns reinforced with SEA sections have not been fully investigated yet. This study develops finite element (FE) models for quantifying the behavior of axially loaded square RC short concrete columns reinforced with SEA. The inelastic buckling of SEA cross-sections and the effects of concrete confinement are considered in the simulation. The accuracy of the FE analysis is verified using available test results. The influences of material and geometric properties on the compressive behavior of square RC short concrete columns incorporating SEA are studied. The results show that the model accurately estimates the behavior of square SEA reinforced concrete short columns. Moreover, the width of the SEA sections, the concrete compressive strength, and the lateral tie spacing have the most significant effects on the performance of SEA reinforced concrete columns subjected to axial loads.

Short and Long RC Columns with Internal WWM Reinforcement under Concentric and Eccentric Compression

Recently, various types of steel meshes were used as additional internal reinforcement for improving the confinement, ductility, and strength of the reinforced concrete (RC) columns. In this experimental study, a welded wire mesh (WWM) layer was used as an internal reinforcement in addition to the traditional steel reinforcement (longitudinal bars and transverse ties) for short and long RC columns under concentric and eccentric compression. Thirty-six square RC columns with two slenderness ratios λ (height to width ratio) of 9 and 18 were tested under compression with eccentricity ratios e/t (eccentricity to section thickness ratio) of 0, 0.13, and 0.26. The reference columns were traditionally reinforced with longitudinal steel bars and transverse ties with a reference volumetric ratio ρr of 0.44%. The other columns comprised a WWM layer wrapped outside the ties whose volumetric ratio ranged from 0.22% to 0.44%. The results demonstrated that the columns reinforced with a WWM layer in addition to traditional reinforcement showed an improvement in ductility and strength compared to those reinforced with longitudinal bars and transverse ties only. A WWM layer increased the ultimate load of the columns comprising ρr ties by approximately 16% and 9% for short and long columns, respectively. These improvements were proportional to the ties volumetric ratio.

Experimental Study on the Behaviour of Short Columns Confined by Waste Plastic Bags-Epoxy Composites

An experimental study was carried out to investigate the behaviour of short column confined by waste plastic bags and nylon strips and findings of this study are presented in this paper. Eight reinforced concrete (RC) short columns were casted. Among them two specimens were named as control, while remaining six specimens were divided into three groups [two specimens for each group] based on different confinement techniques investigated in this study. In retrofitting technique 1 (RT-1), RC short columns were externally confined by full wrap of plastic bags, while in retrofitting techniques 2 (RT-2) and 3 (RT-3), confinement was provided to the short columns by stirrups of nylon and plastic bags with 25 mm clear spacing, respectively. The testing under compression loading was performed on UTM of 100T capacity. From the results obtained, seismic parameters such as ductility, fracture energy before peak and after peak, factor k* and load-displacement response were studied. The results indicated that RC short column confined by RT-1 (full wrap) gives better performance in terms of ductility and fracture energy after peak. Increase in the ductility of RT-1 specimen was about 25% as compared to the control one. Moreover, post-peak fracture energy exhibited by short column confined through techniques RT-1 and RT-2 was 132 and 125 N/mm as compared to control one with 14 N/mm of fracture energy. The experimental observations further indicated that the failure of control specimen was sudden showing high brittleness while the failure of confined specimens by RT-1 and RT-2 techniques was observed to be gradual giving some warning before final failure.

Seismic Performance Analysis of RC Frames with ECC Short Columns Based on the IDA Method

Engineered cementitious composite (ECC) is a high-performance composite material with greater shear deformation and shear strength than normal concrete, which has been proposed for use as a shear component in structures. This study modeled three frames, a pure reinforced concrete (RC) frame, an RC frame with concrete short columns and an RC frame with ECC short columns, using the incremental dynamic analysis (IDA) method to evaluate the contribution of ECC to the structural performance. A modified IMK model was applied to model the entire history of the mechanical behaviors of the short columns. The IDA curves, interfloor displacement angle distribution and limit state of the vertex displacement of the frames were analyzed to investigate the seismic responses of the frames. The model analysis results showed that an RC frame with short columns would form a weak layer on the floor where the short columns were located, which greatly weakened the seismic performance of the structure. ECC was certified to be effective in improving the shear formation of the short columns in the frames. The frame with ECC short columns improved the seismic performance of the structure to a certain extent relative to the frame with RC short columns. The deformation capacity of the frame with ECC short columns was close to that of the pure RC frame at the collapse level.

Seismic Behavior of Reinforced Concrete Short Columns Subjected to Varying Axial Load

Seismic Behavior of Reinforced Concrete Short Columns Subjected to Varying Axial Load

Experimental study on the seismic behavior of ECE corroded reinforced concrete short pier columns

• ECE tests conducted on RC short pier columns. • Experimental investigations on seismic behavior of corroded RC short pier columns. • An investigation in the influence of corrosion and axial load on bending, shear, and slip deformation components. • The prediction equations for the shear strength of corroded short piers were derived. This paper experimentally investigates the effects of corrosion and axial load on the seismic performance of reinforced concrete (RC) short pier columns. In this study, five RC columns were designed and fabricated, and the electrochemical chloride erosion (ECE) technique was used to simulate the corrosion process. The damage process, hysteresis behavior, stiffness degradation, energy dissipation capacity, and shear deformation were all considered while analyzing the seismic behavior of the test specimens. The experiments found showed that the axial load has a substantial impact on the deformation capacity of corroded RC short pier columns. With increasing corrosion level and axial load level, the energy dissipation capacity after the peak point decreases significantly, demonstrating the adverse coupling impact of corrosion damage and axial loads. Furthermore, the corrosion damage can weaken the shear capacity of the RC column and can increase the proportion of shear deformation to the total deformation. Based on the experimental results, a formula for determining the shear strength of the RC short pier column was suggested, accounting for corrosion damage and axial load level.

Experimental Analysis of Bearing Capacity of Basalt Fiber Reinforced Concrete Short Columns under Axial Compression

Adding basalt fiber to concrete can improve the mechanical properties of concrete, and it is also one of the best ways to enhance the ultimate bearing capacity of concrete structure. In this paper, the construction performance and the compressive strength of basalt-fiber-reinforced concrete (BFRC) with five kinds of fiber lengths and eight kinds of fiber volume content subjected to an axial load are systematically investigated. The optimum fiber length and fiber volume content are obtained by comprehensively considering the construction performance and compressive strength. Moreover, the prediction model and finite element analysis method of the ultimate bearing capacity of basalt-fiber-reinforced concrete are developed. The results show that the optimum fiber length is about 12–24 mm and the fiber volume content is 0.15%. Adding an appropriate amount of basalt fiber can effectively improve the ultimate bearing capacity of concrete short columns, with maximum and average increases of 28% and 24%, respectively. In addition, the comparison with the experimental results shows that both the proposed prediction method and the finite element modeling method have good applicability, and they can be used to predict the ultimate bearing capacity of the BRFC short columns in practical engineering.

Enhanced Repair Techniques of Corroded Reinforced Concrete Short Columns

Enhanced Repair Techniques of Corroded Reinforced Concrete Short Columns

Axial Compression Test and Bearing Capacity Analysis of Biaxial Prestressed Angle Steel Plate Fully Wrapped Reinforced Concrete Short Column

A new external reinforcement method is proposed in this research by using the prestressed angle steel plate to fully wrap a reinforced concrete column with a rectangular cross section. To study the axial compression characteristics of the new proposed structure, twenty pieces of the concrete columns were built using the normal reinforcement: five control columns and fifteen reinforced concrete columns, with three groups of different prestressed angle steel plates. These columns were tested under axial compression after the completion of the reinforcement. The experimental results showed that the ultimate load‐bearing capacities of the three groups of the reinforced concrete columns with different prestress levels were increased by 35.6%, 52.7%, and 61.7% compared with the control columns. Both the ultimate strain and the deformation were improved significantly. The load‐bearing capacity equation of the reinforced column was deduced based on the unified strength theory, and the accuracy of the equation was validated. Moreover, a finite element simulation was performed for the new structure, and the simulation results were in good agreement with the test results. Simulation results are in good agreement with the experimental results.

Fire Behavior and Modeling of Short RC Columns in Pure Axial Compression: Role of Volume, Configuration, and Spacing of Lateral Reinforcement

AbstractThis paper studies the role of volume, spacing, and configuration of lateral reinforcement on the axial load resisting capacity of reinforced concrete (RC) columns at elevated temperatures....

Shear strengthening of RC short columns with CFRP grid-reinforced FRC matrix: Cyclic loading tests

This study investigated the shear behaviors of reinforced concrete (RC) short columns retrofitted with a new textile-reinforced mortar (TRM) system made of carbon fiber-reinforced polymer (CFRP) grid-reinforced short-fiber-reinforced concrete (FRC) (referred to as “TR-FRC”). Six RC specimens, including two control specimens and four specimens strengthened with TR-FRC jacket, were tested under the combined action of constant axial load and cyclic horizontal load. The experimental parameters were the reinforcement ratios of CFRP grid and shear span-to-depth ratios. The test results indicated that the shear capacity, deformability, ductility and energy dissipation capacity of the strengthened columns were superior to those of as-built counterparts. The stiffness degradation of the strengthened columns was further delayed as the reinforcement ratio of the CFRP grid in composites overlay increased. Under smaller shear span-to-depth ratio, the TR-FRC system was still very effective in increasing the shear capacity of the RC columns. Moreover, based on the current code and superposition principle, considering the effective strain of the fiber grid, a design equation was proposed to predict the shear capacity of strengthened members.

Experimental Research on Axial Compression of Reinforced Concrete Short Circular Columns Strengthened with Prestressed Semicircular Steel Plates

According to the statistics of relevant departments, the total area of various existing buildings in China is at least 10 billion m2, of which about one-third of the houses have reached the design life and the safety reserve is insufficient. It is not economical to demolish these houses and rebuild them, and the benefits of new buildings are far less than those of extending the service life of old buildings through reinforcement. Therefore, reinforcement technology is increasingly indispensable. Currently varying methods for the prestressed reinforcement of concrete columns are developed, but they are generally not practical. Strengthening concrete columns with prestressed semicircular steel plate is a new prestressed strengthening technology. In this article, the experimental study on the axial compression of a reinforced concrete circular section short column strengthened with prestressed semicircular steel plate is carried out by combining experimental and numerical simulation methods, and the calculation formula of the bearing capacity of the reinforced short column is established by finite element analysis.

Effect of splitting bond on shear response of reinforced engineered cementitious composite short columns under cyclic loading

The effect of splitting bond on shear response of reinforced engineered cementitious composites (RECC) short columns under cyclic loading is experimentally investigated in this paper. Nine RECC short columns were designed to test the effect of axial load ratio, stirrup spacing and shear span-to-depth ratio on their cyclic response, and one reinforced concrete (RC) short column was prepared for comparison. The test results show that the RC short column failed in shear-splitting bond failure (shear accompanied by splitting bond) with poor plastic deformation and low energy dissipation. Splitting bond failure was effectively delayed in RECC short columns due to the high tensile strength and ductility of ECC, the RECC short columns failed in shear-splitting bond failure with ductile characteristics and thus exhibited improved cyclic response. In particular, the RECC short column corresponding to the control RC short column gained a 54.5% and a 60.7% improvement in ultimate drift ratio and cumulative energy dissipation, respectively. Additionally, a series of formulas based on truss-arch model was proposed to predict the shear strength of RECC short columns controlled by splitting bond, and the proposed model gives reasonable calculated results compared with the test results.

Seismic Performance of RC Short Columns Retrofitted with a Novel System in Shear and Flexure Using CFRP Composites

Abstract Shear is the predominant failure mode in most reinforced concrete (RC) short columns under seismic loads. The overall structural performance of short columns can be improved by shear stren...

Repair of Fire Damaged Axially Loaded Short RC Columns Using GFRP Wrap

Fire damaged columns can be repaired with glass fibre reinforced polymer (GFRP) wrap to regain its full strength or even more. In the present work, short reinforced concrete (RC) rectangular columns which are exposed to elevated temperature at 4000℃ for 2 hours duration are repaired using GFRP wrap glued with epoxy resin. Strengthening of existing columns using GFRP wrap is a simple, easy and economical solution. GFRP wrap enhances the stiffness of the column in lateral direction, which improves the load carrying capacity of the column. The behaviour of GFRP wrapped column is different from the behaviour of column without GFRP wrap in response to the applied load. The behavior of GFRP strengthened column depends on various factors such as column cross sectional area aspect ratio, radius of rounded edges of the column, number of GFRP layers wrapped, width of GFRP strip, wrap pattern, epoxy properties etc. Various wrap patterns are tried to obtain effective one which greatly enhances the load taking capacity of short axially loaded columns. GFRP wrapping using strips showed good results than using continuous layer. The load carrying capacity of fire damaged GFRP repaired columns is increased by 42.3% compared with undamaged column without GFRP wrap and increased by 112.6% compared with fire damaged column without GFRP. Designer should fairly estimate the capacity of the strengthened column. Mathematical models are developed to predict the strength of repaired columns.

Enhancement of circular RC columns using steel mesh as internal or external confinement under the influence of axial compression loading

Reinforced concrete (RC) columns cannot get supreme confinement by using the customary steel stirrups reinforcement because of the requirements for the spacing distances between the stirrups in addition to concrete continuance trouble. For this, Steel Mesh (SM) externally wrapped around the outer perimeter of the column as contributory confinement are being widely used due to its features. Limited tests focused on using SM for the internal confinement around the reinforcing cage of RC columns. Moreover, no experimental comparison was presented between RC columns internally and externally confined using SM. This paper investigates experimentally the behavior of circular RC columns confined internally or externally by SM. Six short RC columns have been subjected to axial loading until failure. The main studied parameters were SM schemes, number of SM wraps, SM position (internally or externally), and the steel stirrups existence. Results demonstrated that SM could decrease the crack opening, diminish the concrete spalling, increase the maximum failure load, and enhance the ductility, energy absorption, and column stiffness. Furthermore, the partially internal confinement using two wraps of SM around the steel ties presented the maximum capacity with reasonable ductility. In general, internally confined columns showed better behavior than the externally confined one.