Strong Column-weak Beam Research Articles

Enhancing Quality Control in the Mix Design of High-Strength Concrete Using a Capacity-Based Approach

The mix design of concrete is an important aspect that affects its strength and durability. This paper aims to revisit the existing mix design method given in IS 10262:2019 through a capacity-based approach. The approach involves identifying the possible failure modes in concrete and eliminating the undesirable ones leading to significant reduction in dispersion. This is accomplished by utilizing coarse aggregates that meet a specific minimum strength requirement or threshold (e.g., ~ 77 MPa for M95 grade of concrete), which is determined through a priori estimating the cohesion and friction angle of the concrete. The methodology to estimate the cohesion and friction angle from a single unconfined compression test is proposed based on the Mohr–Coulomb theory and using the orientation of failure plane of fractured specimen as a supplemental information from the same experiment. This paper also offers a simple and approximate test procedure to estimate the aggregate's compressive strength (~ 106 MPa in this mix design) reasonably which is essential for the capacity-based mix design. An experimental programme is also carried out to design the concrete mix using the proposed capacity-based approach. The results indicate that M95 concrete is achieved with a low standard deviation and coefficient of variation (~ 3%), falling in class of excellent quality control as per ACI 214R-11. This quality control is crucial in seismic structural design as variations in concrete strength is likely to negate the underlying principle of strong column–weak beam philosophy resulting in the triggering of undesirable shear modes of failure.

Experimental and numerical investigation of failure modes in RC frame structures designed using the equivalent linearization method

The codes of many countries currently employ the column-to-beam flexural strength ratio (CBFSR) based on frequent earthquake internal forces to achieve the expected strong-column-weak-beam (SCWB) ductile failure mode. However, real earthquake damage indicates a general failure to achieve SCWB. The design method based on frequent earthquake internal forces struggles to consider factors such as internal force redistribution and variable axial forces under rare earthquakes. Therefore, developing a seismic design method directly based on rare earthquake internal forces is crucial. The equivalent linearization method is a practical approach for obtaining the internal forces of RC frame structures under strong earthquakes without extensive nonlinear computations. In this paper, nonlinear finite element analyses of RC frame structures with expected SCWB failure modes under various structural parameters were conducted to obtain ductility coefficients under rare earthquakes. Using the equivalent linearization method based on secant stiffness, the equivalent stiffness and damping of beams and columns were calculated. Simplified parameters were determined for engineering applications to facilitate seismic design based on rare earthquake internal forces. Two RC frame structures were designed using both the equivalent linearization method and the CBFSR code method, and then subjected to pseudo-static low-cycle reciprocating loading tests. The study investigated failure modes and hysteretic energy dissipation, as well as overall stiffness and bearing capacity under earthquake conditions. Results showed that the equivalent linearization method can effectively direct RC frame structures to achieve the expected strong earthquake failure mode.The dynamic time history analysis was performed on finite element models of different heights, and the results indicated that the equivalent linearization method significantly reduced plastic hinge occurrences and ductility coefficients of column ends, resulting in improved seismic performance compared to the CBFSR code method.

Research on column overdesign factor of reinforced concrete frame structures in the 2022 Ms 6.8 Luding earthquake

The strong column-weak beam failure mode of reinforced concrete (RC) frame structures is one of the most important targets of structural seismic design and is primarily realized by a reasonable column overdesign factor (COF). However, most RC frame structures in previous earthquakes were often subjected to strong beam-weak column failure modes. To address this issue, the RC frame with a strong column-weak beam failure mode and a typical strong beam-weak column RC frame in the 2022 Ms 6.8 Luding earthquake were intensively studied in this study. The differences between the two failure modes of the RC frame structure were comparatively analyzed at both the overall structure and member levels. A numerical simulation was conducted to obtain the structural response under actual ground motion. Finally, a probabilistic analysis method was adopted to process the COF data of the RC frame joints. The results indicate that the structural safety redundancy of the RC frame with the undesired failure mode cannot be fully utilized, whereas the RC frame with the strong column-weak beam failure mode allows more structural members to participate in the energy dissipation through a complex redistribution mechanism of internal forces. Damage to the infill wall further mitigates the degree of damage to the main structure and reduces the risk of soft-story failure. The COF of the actual RC frame structure shows a non-uniform distribution, and it is recommended that the COF be higher than 1.5 for the seismic design of the structure following the Chinese code.

Column-to-beam flexural strength ratio for rigorous strong-column–weak-beam design for steel–concrete composite frames

This study addresses the limited research and unclear principles surrounding the strong-column–weak-beam (S-C–W-B) criterion in steel–concrete composite frames, a critical aspect of structural engineering. Despite its widespread application in steel frames, the S-C–W-B criterion's adaptation to steel-concrete composite frames remains underexplored. The research aims to clarify and establish consistent guidelines for preventing column hinge formation at the joint, a key concern in S-C–W-B design. Beginning by analysing the definitions of ultimate flexural strength and flexural yielding strength of a section, essential components of the S-C–W-B criterion, the minimum column-to-beam flexural strength ratio (ηc, min) required for a robust S-C–W-B design was deduced. The methodology involves a novel parametric analysis using a fibre beam–column model. This model is used to derive a closed-form equation for ηc, min, which was then verified through time-history analysis using the finite-element software MSC.Marc. The findings indicate that the established ηc, min provides a stringent, nonetheless, reliable criterion for S-C–W-B design in steel-concrete composite frames. This research not only bridges a significant gap in existing structural engineering knowledge but also proposes a practical approach for safer and more efficient design in real-world applications.

Building Assessment Post Earthquake 21 November 2022 in Cianjur District

The earthquake that occurred in the Cianjur area, West Java on Monday 21 November 2022 at 13.21 WIB resulted in 635 fatalities and 56,000 houses that were damaged. The results of the assessment found that many houses and public facility buildings still did not meet the requirements for earthquake-resistant buildings, especially in the use of concrete materials, main reinforcement, stirrups in columns, beams, foundations and beam-column joint, and did not have a strong column-weak beam planning concept. This can be seen from the inability of the column to withstand/ carry the working load which causes the column to collapse and damage. Therefore, it is very necessary to pay attention to building planning in Disaster Prone Areas (DPA) in accordance with earthquake resistant building regulations SNI 1726:2019 and SNI 2847:2019

Pre-relaxed cables for improving progressive collapse resistance of RC frame subassemblages considering slabs

A common method to improve the progressive collapse resistance of reinforced concrete (RC) frame structures is to increase the reinforcements in beams, which might result in the undesired failure mode of strong beam-weak column for the structures under earthquakes. To improve the progressive collapse resistance of the RC frame structures without affecting their seismic behaviors, a novel retrofit has been proposed using pre-relaxed cables. This study investigated the improvement of the pre-relaxed cables on the progressive collapse resistance of the RC frame structures considering the presence of the slabs subjected to the distributed loads. A quasi-static test was carried out on two one-quarter scaled 2 × 2-bay subassemblages, i.e., a beam-slab (BS) subassemblage and a beam-slab-cable (BS-cable) subassemblage. Experimental results found that the progressive collapse resistance and deformation capacity of the BS-cable subassemblage was 55 % and 260 % larger than those of the BS subassemblage, respectively. The resistance improvement mechanism of the BS-cable subassemblages was revealed, i.e., the tensile catenary action in the beams, tensile membrane action in the slabs, and tension action in the cables. The finite element (FE) models were then developed, validated against the experimental results, and used for parametric studies with the consideration of the cable diameter and cable original length. Numerical results found that there were two failure modes for the BS-cable subassemblages, i.e., beam failure mode and slab failure mode. The upper limit of the improvement of the progressive collapse resistance using the cables is critically related to the failure mode. For the beam failure mode, the increase in the cable diameter could improve the progressive collapse resistance until the slab failure mode occurred.

A multi‐phase mechanical model of biochar–cement composites at the mesoscale

AbstractThis study presents a five‐phase mesoscale modeling framework specifically developed to investigate crack propagation and mechanical properties of biochar–cement composites. The multi‐phase model includes porous biochar particles with precise geometric construction, sand aggregates, cement matrix, and interfacial transition zone adjunct to both the biochar particles and sand aggregates. The 3D porous biochar library was first proposed and established in this study, which could provide an external interface for describing different pore shapes, wall thicknesses, and pore areas. All the simulation results were experimentally validated using a digital image correlation. Through precise geometric modeling, the unique failure modes and timing of biochar particles within the mortar were identified. This is analogous to the “strong column–weak beam” concept, accounting for the enhanced ductility observed in the biochar–cement composites under compression test. This work can advance the geometric modeling of porous aggregates broadly and elucidate their mesoscopic failure mechanisms in cementitious materials, thus providing new insights for developing high‐ductility and lightweight cement composites.

Influence of the Vertical Load Bearing Status on the Seismic Performance of Weak-Joint-Type RC Frames Strengthened by the Wing Wall Installation Method

“Strong column–weak beam, strong joint–weak member” is a core concept for the seismic design of buildings. For existing reinforced concrete (RC) frame buildings that do not satisfy this concept, installing RC wing walls beside existing columns is a simple and effective method for strengthening both columns and joints to promote a beam-hinging mechanism. In this study, a numerical simulation method is used to analyze the seismic performance of weak-joint RC frames strengthened by additional wing walls considering the column axial force ratio and to determine whether to consider the secondary load as a variable. The results show that when the secondary load is not considered, i.e. existing columns do not bear a load during the strengthening process, the strength, stiffness and energy dissipation of the structure increase with increasing axial force ratio, but the ductility of the structure decreases. When the secondary load is considered, the strength and initial stiffness of the frame are the greatest when the column axial force ratio is 0.4. When the axial force ratio is less than 0.4, the secondary load has less influence on the strength, stiffness and energy consumption. When the axial force ratio is greater than 0.4, the secondary load has a significant impact on the seismic performance of the strengthened structure, and the strength, stiffness, energy consumption and ductility are significantly greater than those in the case in which the secondary load is not considered. Additionally, the larger the axial force ratio is, the more significant the difference is. It is revealed that in engineering seismic strengthening using the wing wall installation method, the influence of secondary load on seismic performance should not be ignored, especially when the axial force ratio is large.

Evaluation of the seismic response of reinforced concrete buildings in the light of lessons learned from the February 6, 2023, Kahramanmaraş, Türkiye earthquake sequences

AbstractOn 6 February 2023, two significant seismic events occurred in the southeastern region of Türkiye. The seismic activity, which was perceptible in numerous countries beyond Türkiye, resulted in a considerable number of fatalities. A considerable number of individuals lost their lives and were rendered homeless as a result of the disaster. Two of the most significant factors contributing to the occurrence of these tragedies are the magnitude of the earthquake and structural deficiencies. The present study is concerned with a detailed analysis of these two factors. This study initially considers the seismicity of the region where the earthquakes that occurred on 6 February 2023 took place, as well as the seismic characteristics of these earthquakes. Subsequently, the findings of the field studies conducted in Hatay, Adıyaman, Kahramanmaraş and Malatya, the cities where the earthquakes caused the most destruction, are presented. The objective of the field study is to ascertain the collapse patterns, structural damages and the factors influencing these damages in reinforced concrete structures in the region. The primary causes of damage to structures can be attributed to several factors, including the presence of a strong beam-weak column mechanism, the soft story-weak story mechanism, the pounding effect, the short column damage, the long cantilever and overhangs, the short beam damage, the buckling damage, the torsion effect, the quality of the materials, the insufficient transverse reinforcement, the compressive failure due to over-reinforcement, the corrosion effect, the damage to reinforced concrete shear walls, the infill wall damage, and the damage caused by the soil and foundation system. These causes have been evaluated and recommendations have been formulated to prevent structural damage.

An Investigation of Seismic Behaviour of Prestressed Concrete Frame Structures using Pushover Analysis

Abstract: The prestressed concrete system is a prominent material in civil engineering, with applications ranging from buildings, bridges, foundations, piling, silos, stadiums, roadways, and other infrastructure. However, this work is primarily concerned with its applicability to building frame constructions subjected to seismic loading. The prestressed concrete system for frame constructions not only reduces the amount of structural components, but it is also a cost-effective technology that provides outstanding strength and stiffness, as well as quick and simple site erection. Hence, we will be able to use these prestressed concrete components to their full capacity, unlocking engineering and social benefits that were previously impossible. Prestressed concrete designs, as opposed to reinforced concrete designs, can give structures with substantially longer spans, no cracks, or fewer cracks with tiny crack widths. Nonetheless, research on the seismic behaviour of prestressed concrete frame structures is relatively restricted, with the majority of studies focusing on reinforced concrete structures. Finally, the provisional versions of modern building codes such as ACI 318, GB50010, and EC2 do not provide thorough processes for seismic design of prestressed concrete structures. In this work, the seismic design and behaviour of prestressed concrete building frames are explored using the most recent design code. Three model-building codes will be investigated and compared, including ACI 318- 14, Eurocode 2004-2, and Chinese GB500010-2010. The 10-story prestressed concrete frame system is subjected to gravity and seismic loading, and the strong-column weak beam mechanism is archived to conform with the newly implemented building design code. To examine the behaviour of prestressed concrete frame structures, nonlinear static pushover analysis is used to capture the reaction under earthquake loading. The stiffness and strength needed will be designed in compliance with the three major building codes indicated. In addition, the finite element model will be created using CSI Sap200 to capture its actions.

Investigation of seismic resistant structures with various moment-resisting frame systems and pushover analysis

Earthquakes are a serious threat in the construction of multi-storey buildings in Indonesia, which are divided into several seismic design categories. The design of seismic-resistant buildings requires the management of plastic hinges to reduce seismic loads. The aspects of seismic-resistant structural design in Indonesia are regulated by SNI 1726:2019, SNI 1727:2020, and SNI 2847:2019. Intermediate Moment Resisting Frame System (IMRFS) and Special Moment Resisting Frame System (SMRFS) are used based on seismic category and earthquake intensity. Pushover analysis is used to analyze the structures behavior when exposed to seismic loads. This research designs seismic resistant structures with IMRFS and SMRFS at different locations with the aim of assessing structural performance and gaining reinforcement to the concrete ratio, which is relevant for the design and construction of multi-storey buildings in Indonesia. The results of this research are the structural performance levels, reinforcement volume, concrete volume, and the reinforcement to concrete volume ratio. Both IMRFS and SMRFS reached Immediate Occupancy to Life Safe performance levels after the earthquake because their monitored displacement was not significantly different. The structural failure modes of both systems meet the Strong Column–Weak Beam requirements. The distribution of plastic hinges also remains in the Immediate Occupancy category.

ANALISIS KINERJA STRUKTUR PADA GEDUNG BERTINGKAT DENGAN ANALISIS PUSHOVER BERDASARKAN ATC-40

Indonesia is an area prone to earthquakes. Earthquakes can cause infrastructure damage and casualties. Efforts are needed to reduce the risk of earthquake hazards by strengthening earthquake-resistant infrastructure. The design procedures for earthquake-resistant buildings are carried out using a performance-based design approach. Building performance can be estimated through non-linear static pushover analysis. This research takes a case study in Jongke Market, Surakarta. This research aims to determine the capacity curve, performance level, and structure collapse mechanism. The method used is pushover analysis with the capacity spectrum. The result of this analysis is a capacity curve that processed to determine the level of structure performance referring to the drift ratio limitation table in the Applied Technology Council (ATC-40). Based on the results of this research, displacement that occurred in the x direction is 92 mm and in the y direction is 77 mm. Building displacement is good because the displacement that occurred is smaller than the displacement limit (control). The total maximum drift in the x direction is 0.007 and in the y direction is 0.006. The maximum inelastic total drift in the x direction is 0.005 and in the y direction is 0.004. Based on the drift ratio limitation table in the ATC-40 document, this building has an immediate occupancy performance level. Based on the plastic hinge mechanism formed, the existing structure also meets the ideal collapse concept (strong column-weak beam).

Experimental and numerical investigation of bolt-free preloaded connection for steel-framed modular buildings

This paper introduces an innovative bolt-free preloaded inter-module connection for steel-framed modular buildings, referred to as the ‘AJ’ connection. It provides the vertical connection between columns by engaging a preload induced by long steel rod bolts (SRB) and specially designed couplers. The preload is applied using a torque or impact wrench. Consequently, the connection simplifies the on-site assembly and disassembly processes of the modular building, thereby enhancing both construction speed and reusability of modules. In this study, the structural performance of the AJ connection was investigated experimentally and numerically. First, the coupler was tested under a uniaxial tensile load to check its strength. Then, preloading tests on assemblies of a coupler and a 3m long SRB were conducted to determine the torque-preload relationship. Subsequently, full-scale beam-to-column joints featuring the AJ connection were tested under monotonic loading to investigate its lateral-force resisting mechanism. Lastly, the seismic performance of the AJ connection was investigated using FE joint models calibrated against a combination of test results and geometric and material nonlinear analyses with imperfections (GMNIA). A comparative analysis with a welded connection was also conducted to evaluate the seismic performance of the AJ connection. The findings indicated that the AJ connection demonstrates seismic performance comparable to the welded connection, exhibiting Strong column-Weak beam behaviour for seismic moment-resisting frames. Additionally, it satisfies the ductility requirements for structures of ductility class DCM as specified by EN 1998–1.

Database of tall pre-Northridge steel moment frames for earthquake performance evaluations

This article describes a detailed database of tall steel moment frame buildings that are representative of the construction practices in San Francisco prior to the 1994 Northridge earthquake. The database contains design details that affect the structural performance of steel moment frames, including frame geometry, member cross-section sizes, and gravity system characteristics. This database also captures irregularities that might impact seismic response, such as podiums, setbacks, mass concentrations (mechanical, electrical, and plumbing (MEP) floors), interrupted column lines, and atriums. The database includes information on 89 moment frame buildings, 14 of which were built before 1960 and are constructed with riveted connections, while the remaining 75 have welded flange connections like those that suffered brittle fracture during the 1994 Northridge earthquake. The buildings are further distinguished between space frame, perimeter frame, and partial space frame systems. For about half (41/89) of the buildings in the database, section sizes of representative structural members were collected, which enabled the evaluation of the seismic design, elastic, and inelastic response using computational workflows. The design diagnostics indicate that most of the buildings meet the minimum seismic strength and strong-column weak-beam requirements of modern building codes, even though they were not necessarily designed with this intent. On the contrary, about one-third of the buildings do not meet the seismic design drift limit of current codes, and about half of them have weak beam-column panel zones. This database, associated structural analysis models, and processing scripts are published at DesignSafe https://doi.org/10.17603/ds2-wjad-r340 to facilitate collaboration and continued development of open-source data for high-resolution simulations to inform risk mitigation strategies on a regional scale.

Shaking table tests on inclined collapse mechanism of RC frame structures subjected to earthquakes

Inclined collapse of structures under strong earthquakes threatens the adjacent infrastructures. The collapse mode and collapse direction should be considered with caution to curb the secondary disaster in the urban area. However, current studies on the inclined collapse mechanism are predominantly limited to the qualitative and intuitive understanding. To fill this gap, this study presents an insight into the inclined collapse mechanism of the reinforced concrete (RC) frame structures with two typical features subjected to earthquakes, i.e., the structures with slab opening on one side of the first floor and the structures with disparate axial compression ratios of the first story columns on the opposite sides. First, shaking table tests were performed on two 1/10-scale three-story RC frame structure models undergoing inclined collapse. Then the multi-scale finite element models were established, validated against the test results and used for parametric studies. In the parametric studies, two coefficients were considered to describe the typical features of the RC frame structures, i.e., the strong column-weak beam ratio η and differential rate of the axial compression ratios λ. The test and numerical results found that the inclined collapse mechanism was attributed to the different distributions and discrepant resistance deterioration of the plastic hinges among the first story columns of the RC frame structures with the two features. This causes the inconsistent damage levels among the first story columns, the dominant direction of the lateral displacement, and the inclined collapse of the structures. Finally, the collapse mode and collapse direction can be controlled by appropriately adjusting the two coefficients η and λ for the structures with the typical features concerned in this study.

Retrofitting of Damaged Crumb Rubber Concrete Frame Using Fiber Reinforced Polymers

Abstract: The research work is focused on the retrofitting of damaged crumb rubber concrete frame. The retrofitting of these frames was carried out using Carbon Fiber Reinforced Polymers (CFRP) wrapping technique accompanied with beam weakening technique, carried out at certain locations to achieve the desired failure mechanism. Two previously tested 1/3rd reduced scale models Crumb rubber concrete (CRC) and Normal concrete (NC) were CFRP retrofitted along with beam weakening and then tested dynamically. From the as-built testing strong-beam weak-column effect was observed, for that purpose beams weakening through cores removal away from the face of the column equal to two times depth of the beam, so as to shift the damage from the brittle failure mechanism of column and joint damage to more ductile damage in the beam. In addition to beam weakening the damaged beam column joints were CFRP retrofitted. A comparative study between the retrofitted and as-built models was done. The results obtained from testing has recovered the ductility up to 82% and response modification factor up to 90% for normal concrete while in case of crumb rubber concrete frame the ductility is recovered up to 76% and its response modification factor up to 81%. As intended, a much-distributed damage behavior/cracking pattern as compared to the reference models, especially in the case of normal concrete model. The intended purpose of the retrofitting in recovering seismic properties and a comparatively distributed damage/cracking pattern was achieved. The purpose of beamweakening through core removal for shifting the damage from columns and joints towards the beams for achieving a more ductile failure mechanism was achieved to some extent.

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.

Seismic Performance and Damage Evaluation of Reinforced Concrete Structures Based on Field Investigation Made After February 6, 2023, Kahramanmaraş Earthquakes

On 6 February 2023, an earthquake doublet occurred, the first at Kahramanmaraş Pazarcık district ([Formula: see text]) at local time 04:17 and the second, which approximately 9 hours after the first earthquake, occurred at Kahramanmaraş Elbistan district ([Formula: see text]) at local time 13:24 in Türkiye. It is a disaster affected 11 cities in the eastern region in Türkiye and is referred as “Disaster of the Century”. Earthquake disasters allow humanity to investigate seismic behavior under related construction details and revising the seismic codes. The authors conducted observational research to obtain interpretive information and digital data by investigating structural damages of moderately and heavily damaged buildings from earthquake sites. In this paper, performance evaluation is done based on existence of soft storey, weak column-strong beam, deficiencies and pounding effect. Damages are classified as beam, column, beam-column joint and shear wall, infill wall, roof and scaffolding damages. Ampleness of soft storey, column damages, inadequate joint reinforcement, inadequate structural ductility and low capacity, strong beam-weak column effect, and infill wall damages have been observed from the field. As a result of field observation, structural deficiencies, irregularities and mismatching capacity design principles have been concluded as common problems of reinforced concrete buildings in the Kahramanmaraş earthquake site.

Assessment of the impact of column-to-beam strength ratio on seismic response of RC beam-column connections

Beam-column joints play an important role in the overall resistance of reinforced concrete frames during seismic events. The Earthquakes of Al Asnam on October 10, 1980, and Boumerdes on May 21, 2003 in Algeria, have highlighted the failure of beam-column joints as a cause of building collapse. 3D nonlinear finite element analysis with ANSYS software has been used in order to examine exterior RC beam-column joints under monotonic loading. The research has investigated the influence of the value of the column-to-beam strength ratio (CBSR) of these joints on shear strength and seismic performance of concrete structures by changing the height and longitudinal reinforcement of the beam while keeping column dimensions constant. It has been shown that the beam-column depth ratio and the beam longitudinal reinforcement ratio have a significant effect on the shear capacity and seismic behaviour of exterior beam-column joints. An appropriate value of the flexural strength ratio between the column and beam is crucial in order to establish a "strong column-weak beam" mechanism in reinforced concrete frames, because inadequate values can lead to premature failure or reduced shear capacity at the junction. The Algerian seismic code – RPA99/version2003 suggests a minimum value of column-to-beam strength ratio equal to 1.25 at joints for seismic design when building codes in other countries call for higher ratios. Nevertheless, this approach might not accurately represent the actual behaviour and could constrain the optimal performance of structures.

Cyclic loading response of precast concrete beam-column connections with partially bonded draped prestressing tendon

An emulative precast concrete beam-column connection consists of prefabricated columns, T-shaped composite beams with partially bonded post-tensioned (PT) tendon, and cast-in-place (CIP) core region is proposed in this study. Experimental study was carried out to examine the hysteretic behavior of four full-scale beam-column connections under a high axial compression ratio (μ = 0.4). The specimens included a precast interior connection (PC1), a precast exterior connection (PC2), and two corresponding conventional CIP control specimens (RC1 and RC2). Performance assessment of the suggested connection was conducted by evaluating various factors, including failure mode, hysteresis curve, deformation, stiffness, and energy dissipation capacity. Test results revealed that all specimens fulfilled the design objective of strong column-weak beam with flexural failure showed at beams ends. In comparison to RC1, PC1 exhibited a 6.4 % increase in peak load-carrying capacity in the positive loading process and a 7.1 % decrease in the negative loading process. On the other hand, PC2 demonstrated approximately 11.9 % higher load-carrying capacity in the positive loading and a 2.0 % lower capacity in the negative loading when compared to RC2. The ductility coefficients of PC1 and PC2 was 3.39 and 2.64, respectively, which were slightly higher than that of RC1 and RC2 (3.01 and 2.43). All specimens exhibited good deformation restoring capacity and plump hysteretic loops, demonstrating satisfactory energy dissipation capacity. Overall, the proposed connection with partially bonded PT tendon showed comparable seismic performance with their CIP counterparts, indicated its promising potential for use in practical engineering applications.