Beam-column Joints Research Articles

Seismic evaluation of post-tensioned precast concrete frames with non-grouted fuse-type dissipaters under successive excitations

In recent years, demands for mitigating structural damage and post-earthquake repair costs have spurred considerable research on self-centering seismic force-resisting systems. This study evaluates the Post-tensioned Precast concrete Frame with non-grouted fuse-type Dissipaters (PPFD) through experimental and numerical methods. Quasi-static tests were conducted on a one-bay, single-story PPFD to investigate its seismic response. The tested PPFD was shown to effectively control damage to concrete components and limit residual displacements; imperfections at the beam-column interface joint had a negative effect on the initial stiffness and self-centering performance of the PPFD. Parametric analyses were then performed to discuss the force and deformation responses of the beam-column joint in the PPFD with dissipaters solely beneath the beam. A design method for the PPFD was developed based on the formulas derived and verified from the parametric analyses. Nonlinear dynamic analyses were then employed to evaluate prototype designed multi-story PPFDs subjected to individual earthquakes in addition to mainshock-aftershock sequences. The findings indicated that both configurations of PPFD, with dissipaters either symmetrically arranged on the beam or located exclusively below the beam, exhibited comparable maximum inter-story drifts and significantly smaller residual inter-story drifts than a comparable reinforced concrete frame. Moreover, the PPFD demonstrated only a minor increase in both the maximum and residual inter-story drifts when subjected to aftershocks, compared to a much larger increase for the reinforced concrete frame.

New reinforcements combining a steel plate and screws to enhance beam-column contact surfaces for prestressed timber joints

ABSTRACT The beam-column contact surface of joints in prestressed timber frames is one of the key factors determining structural performance. In this paper, a new reinforcement combining a steel plate and screws was proposed, and the effect of the reinforcements on the performance of joints was investigated by quasistatic tests for 5 beam-column edge joints. First, compared with the conventional joint, the joints reinforced by the steel plate and screws had an average increase in capacity of 25.8% and an average reduction in the degradation rate of the secant stiffness of 14.5%, which were beneficial for resisting repetitive loading. Then, the rate of the final prestressing loss and residual drift of the joint reinforced by the flat steel plate and screws were reduced by 20.5% and 85.7%, respectively, compared with those of the conventional joint. The enhancement effect of the reinforcement combining a U-shaped steel plate and screws was difficult to realize due to the susceptibility to the initial clearance. Finally, the mechanical mechanism of the new reinforcement was clarified, and a method for calculating the compression zone height of the beam in joints with the reinforcement was suggested, which improved the calculation accuracy by 13.7%.

Static Behavior of UHPC Corner Beam–Column Joint Under Constant Axial and Increasing Bi-Directional Bending Loads

Static Behavior of UHPC Corner Beam–Column Joint Under Constant Axial and Increasing Bi-Directional Bending Loads

Welded beam-to-column steel joints: Assessment of European design rules

Properly validated high-quality Finite Element (FE) models with experimental tests permit an accurate description of the load-deformation path and stress state of steel joints and are nowadays accepted as “experimental results”. Changes to the design of welded joints in Eurocode 3 are currently proposed that affect the resistance and stiffness of the components associated with the column web panel. This paper presents an assessment of the design formulations included in the current Eurocode 3, part 1–8, and its forthcoming update in terms of stiffness and moment resistance, compared against a large parametric study of strong-axis beam-column welded joints for open sections carried out using validated sophisticated FE models. The results show that both the old and new Eurocode formulations provide a large scatter and no big differences between both methods. Additionally, the presence of axial force in the column shows a clear increase in the ratio between design resistance vs numerical resistance that, particularly in the case of transversally stiffened joints, may be unconservative.

Sosialisasi Penggunaan Kawat Anyaman Pada Bangunan Tahan Gempa Di Desa Karang Bayan Kabupaten Lombok Barat

In Lombok, West Nusa Tenggara, major earthquakes triggered by transform margin or plate shift often arise, leading to casualties, not only claiming lives but also affecting the livelihood of locals. Karang Bayan Village is a region division of Segerongan Village, these areas are often affected by major earthquakes, the last one took place not too long ago, in 2018. Due to its area located on the mountain slope of Rinjani, Karang Bayan has captivating scenery with a rather mild temperature, making it a perfect tourist destination. Karang Bayan offers various tourist attractions, starting from tours of traditional houses, durian orchards, horse riding, rafting, waterfalls, and many more to explore around the village. To boost tourism, Karang Bayan needs to establish proper accommodations along with other tourist facilities like restaurants. Ferrocement-coated buildings are suitable options considering their strength to withstand an earthquake. Mesh wire application on a ferrocement is more economical and practical compared to applying reinforced columns, reinforced beams, or beam-column joints reinforcement detailing. Both planning and construction are integral parts of founding strong buildings, miscalculations will pose threats to the inhabitants of the building. Karang Bayan community has limited knowledge of mesh-wired ferrocement walls for earthquake-resistant buildings, this community service is carried out in the hope people of Karang Bayan will be capable of constructing earthquake-resistant buildings with mesh-wired ferrocement walls. Positive feedback is shown by enthusiastic discussion between the Karang Bayan community with the community service team.

Seismic behaviour of Exterior RC beam-column joints repaired and strengthened using post-tensioned metal straps

Exterior beam-column joints are the most vulnerable part of substandard reinforced concrete (RC) buildings and are often the first to be damaged during earthquakes. This article presents an experimental and numerical investigation into the behaviour of exterior RC beam-column joints repaired and strengthened using Post-Tensioned Metal Straps (PTMS) for active confinement. The study focused on full-scale beam-column joints with an inadequate core zone detailing, thus emulating the deficiencies found in existing substandard RC buildings. Initially, four “bare” joints were subjected to cyclic tests to induce substantial damage within the core zone. Subsequently, the damaged core of the joints was repaired and recast with new concrete, and PTMS were applied to strengthen the joints, followed by another round of cyclic testing. The experimental findings were compared with predictions generated through established models from existing literature. The results revealed that ASCE/SEI 41–17 guidelines accurately predict the shear capacity of the bare joints. It is shown that recasting the core with new concrete significantly increased the joint’s shear capacity by up to 42% compared their bare counterparts. The use of PTMS strengthening further enhanced the capacity by up to 25%. A “scissors model” was employed for numerical simulations of both bare and PTMS-strengthened joints using DRAIN-2DX, which proved effective at predicting their nonlinear load-displacement envelope response. This article contributes towards the development of new cost-effective post-earthquake strengthening techniques for beam-column joints, with the potential to reduce the vulnerability of substandard RC buildings in developing countries.

Experimental study on large deflections of beam–column joints with reinforced flange plates

Web openings facilitate the passage of pipes and enable plastic hinge transfer. However, because these openings reduce the ultimate load at certain values, reinforced flange plates are introduced into the beam–column connections with web openings. In this study, five experimental specimens were constructed and tested, including one base specimen with only web openings, one base specimen with only flange plates, and three specimens with both flange plates and web openings. The failure modes, load–displacement responses, deflection shapes, and deformation capacity were mainly considered. Subsequently, after experimental verification, the thickness and length of the flange plates, as well as the position and diameter of the web openings were studied by numerical simulation. The results indicate that the catenary contribution coefficients and internal energies of the specimens with reinforced flange plates were higher than those of the base specimens. We also concluded that the optimal thickness of the flange plate is equal to that of the beam flange, and the optimal diameter is the maximum web opening that meets the specification requirements. In addition, the mechanical properties gradually increased with an increase the distance a from the web opening to the beam end for a ≤ 190 mm and then decreased for a > 190 mm.

Design optimization of obstacle avoidance of intelligent building the steel bar by integrating reinforcement learning and BIM technology

In promoting the construction of prefabricated residential buildings in Yunnan villages and towns, the use of precast concrete elements is unstoppable. Due to the dense arrangement of steel bars at the joints of precast concrete elements, collisions are prone to occur, which can affect the stress of the components and even pose certain safety hazards for the entire construction project. Because the commonly used the steel bar obstacle avoidance method based on building information modeling has low adaptation rate and cannot change the trajectory of the steel bar to avoid collision, a multi-agent reinforcement learning-based model integrating building information modeling is proposed to solve the steel bar collision in reinforced concrete frame. The experimental results show that the probability of obstacle avoidance of the proposed model in three typical beam-column joints is 98.45%, 98.62% and 98.39% respectively, which is 5.16%, 12.81% and 17.50% higher than that of the building information modeling. In the collision-free path design of the same object, the research on the path design of different types of precast concrete elements takes about 3–4 minutes, which is far less than the time spent by experienced structural engineers on collision-free path modeling. The experimental results indicate that the model constructed by the research institute has good performance and has certain reference significance.

Mechanical property of bolted-assembled reinforced concrete column-steel composite joints

Herein, a new type of bolted-assembled reinforced-concrete column-steel (RCS) beam composite joint is proposed by analysing the force and force transmission process of RCS beam composite joints. The practicality and uniqueness of the structure apply to beam–column joints in large shopping malls, mid- to high-rise office buildings, factories, garages and other building structures. By the finite-element software modelling, a numerical simulation is established and used to analyse the variation of stress and equivalent plastic deformation, hysteresis curve, skeleton curve, stiffness degradation and energy dissipation coefficient under monotonic displacement–load and cyclic displacement–load. Results elaborate that the RCS composite connection has good ductility under monotonic displacement–load. Besides, under the cyclic displacement–load capacity, the hysteresis curve is full, the stiffness degradation is not obvious and the ductility and energy dissipation are good. This study is expected to promote the engineering application and guide follow-up research of the new nodes.

Shaking table test of a dry-connection fully precast frame structure system

In view of the construction difficulties and ecological environment sensitivity of building construction in extremely cold and high seismic intensity areas, a new type of dry-connection fully precast frame structure system was proposed. The connections of the structure are easy to assemble, which can greatly improve the construction efficiency and provide convenience for the upgrading and replacement of components during service. In order to provide essential insights into the seismic performance of the dry-connection precast structure, a three-story precast frame structure specimen with a scale ratio of 1/2 was designed, constructed, and tested on a shaking table subjected to a series of ground motions with increasing seismic intensities. The connections of the specimen structure include beam-column joint, beam-floor joint and column-foundation joint, precast components were processed in the factory and assembled in the laboratory. The vibration characteristics, damage development, acceleration response and displacement response of the structure were investigated. The experimental results illustrated the excellent seismic performance of the structure with sufficient strength and relatively confined damage. The gradually decreasing frequency and increasing damping ratio were attributed to the slippage and plastic deformation of the connectors and the cracking of beam concrete. And the maximum story drift under rare earthquake of intensity 8 was within the design limit, indicated that the precast frame structure could achieve the performance target of no collapse under severe earthquakes. The data of this test provided support for further study on the design methods and numerical modeling of dry-connection fully precast frame structure systems.

Probabilistic identification method for seismic failure modes of reinforced concrete beam-column joints using Gaussian process with deep kernel

Identifying the seismic failure modes of beam-column joints (BCJs) is crucial for the safety and integrity of reinforced concrete (RC) buildings or structures withstanding seismic forces. However, traditional identification methods fail to provide any indication about the uncertainties within their predictions, which is beneficial for evaluating, interpreting and improving these predictions. This study develops a probabilistic identification method for seismic failure modes of BCJs using Gaussian process (GP) with a deep kernel, which integrates the representational power of deep neural networks with the flexible structure of kernel functions to accurately represent the evolution characteristics of seismic failure modes of BCJs. Analysis results demonstrated the potential of the proposed method for improving the classification accuracy of traditional GPs, as well as its superiority over the prediction accuracy of traditional shear-resistance design methods and machine learning techniques. Furthermore, the proposed method also provides an efficient approach to estimate the uncertainties within their predictions for seismic failure modes of BCJs.

Bi–axially loaded RC beam–column joints and haunch retrofit

AbstractIn this study, seismic bi–axially loaded RC beam–column joints are investigated. An experimental campaign on shear–critical corner joints is presented, including two as–built specimens and one retrofitted using fully–fastened–haunches (FFHR). Bi–axial tests adopted hexagonal protocol which is essentially to apply load in one direction double with respect to the other. Results obtained for as–built condition were included in a database of corner joints tested bi–axially and discussed in the light of the impact of bi–axial load on joint’s shear strength. Further, non–linear finite elements were employed to thoroughly evaluate the bi–axial response. Haunch retrofit was capable to reduce both shear stresses and distortion at joint. Experimentally–derived internal forces were used to validate three–dimensional Strut-and-Tie model of the joints. Such design tool is recommended for practice cases adopting FFHR.

Investigation on effect of ECC coverage condition on seismic behavior of beam-column joint

There is a renewed interest around the world to do fundamental research on novel materials to enhance the overall response of structures under seismic loading. Engineered cementitious composite (ECC) is a special class of concrete with good ductility, which is widely adopted in engineering structures. In this paper, the seismic behavior of beam-column joints incorporated with ECC materials is numerically and experimentally investigated. A database containing available related test results in literature is collected and analyzed to investigate the relations between ECC coverage area and failure characteristics. An interior and an exterior beam-column joint with ECC adopted in the joint region are prepared and tested in this study. The effect of ECC coverage area on the overall joint seismic response is analyzed through a validated finite element model. A modified strength hierarchy analysis is proposed and conducted to consider the application of ECC on the joint. Based on the analytical investigation, the weakest structural element in the joint region is found. The strength hierarchy analysis results have a good correlation with the experimental failure pattern, which shows a potential application as a preliminary analysis to evaluate ECC joint failure mechanisms under seismic loading.

Guided wave-based damage assessment on bolt in precast beam-to-column joints

This paper deals with theoretical, numerical, and experimental investigations of guided wave-based damage assessment on bolts in the precast joints under cyclic loads. The mechanical behavior of precast bolted joints is analyzed, and the relationship between the force and drift ratio of the energy-dissipating (ED) bolt is derived. The propagation characteristic of guided wave in ED bolt is revealed through finite element simulation. The influence of tensile damage and looseness damage on the received signals is further studied, and two indexes are developed for evaluating the health status of ED bolts. Cyclic loading tests were carried out on four precast bolted beam-column joints with different precast beams, and the guided wave signals of ED bolts under each level of loading were monitored by arranging lead zirconate titanate (PZT) sensors. The bolt yield drift ratios were obtained by skeleton curves and FBG strain detectors respectively. The relationships between the two damage indexes and the drift ratio are obtained, and the two developed damage index trends were very well reproduced by analytical expressions. The health state assessment of ED bolts and precast bolted structures is realized by the proposed damage limit method, whether in daily maintenance or after the earthquake.

Performance of Fire Damaged Beam-Column Joints Strengthened with Slurry Infiltrated Fiber Concrete

Performance of Fire Damaged Beam-Column Joints Strengthened with Slurry Infiltrated Fiber Concrete

An Improved Anchorage System for L-Shaped FRP Composites to Enhance the Seismic Response of Beam-Column Joints in a Low-Strength Substandard Reinforced Concrete (RC) Frame

Reinforced concrete buildings are prone to collapse during seismic events due to the brittle shear failure of non-seismic beam-column joints (BCJ). In this study, two one-third scale reinforced concrete (RC) frames incorporating various non-seismic details were tested under lateral cyclic loading. One of the RC frames was used as control, while the other was strengthened using externally bonded carbon-fiber-reinforced polymer (CFRP) sheets in a L-Shaped configuration with particular attention to anchorage to evade debonding. For the strengthening process, L-shaped CFRP sheets were bonded to the inner face of columns, extended on beams both above and below the joint up to a hinge length. To avert debonding, the L-shaped CFRP sheets were fully wrapped with CFRP sheets around the column, both near the joint and at the end of the sheet. The sheets were also wrapped around the beam, through two slots in the slab that were adjacent to the beam-column interface and at the far end of the sheet. Test results confirmed that the installation of CFRP sheets in an L-shaped configuration altered the brittle-shear failure mechanism of the beam-column joints to a ductile failure by repositioning the hinges away from the columns. Additionally, the proposed anchorage method successfully eradicated the debonding and peel-off of the CFRP sheets. Moreover, strengthening with the CFRP sheets in the L-shaped configuration enhanced the strength and ductility of the RC frame by 45% and 43%, respectively. According to the findings of this study, the application of L-shaped CFRP sheets proved effective in strengthening RC frame structures.

Retrofitting RC beam-column joint subassemblies using UHPC jackets reinforced with high-strength steel mesh

Outdated building codes in seismic zones often did not require seismic detailing on beam-column joints, leaving many existing structures vulnerable to earthquakes. To address this issue, three different ultra-high-performance concrete (UHPC) jackets were proposed for retrofitting seismically-deficient exterior beam-column joints, with variables including construction method (cast-in-place or precast) and inclusion of high-strength steel bar meshes. The effectiveness of these jackets was investigated using cyclic loading tests on beam-column joint subassemblages. The results demonstrated that all three UHPC jackets considerably improved the strength, stiffness, and energy dissipation of the beam-column joint subassemblage, as well as both repairable and collapse drifts. However, the cast-in-place UHPC jacket, when not reinforced with steel meshes, failed to effectively improve the ultimate drift capacity of the original beam-column joint subassemblage. Moreover, retrofitting with precast UHPC jackets using chemical anchors failed to generate sufficient composite action. Only the cast-in-place UHPC jacket, when reinforced with high-strength steel meshes, successfully delayed localized joint shear damage and allowed for effective utilization of beam flexural capacity. It improved the joint shear strength by 66%, initial stiffness by approximately 35%, and total energy dissipation by 140%. Finally, strength models were suggested for evaluating the joint shear strength and beam flexural capacity of UHPC-retrofitted beam-column joints.

Numerical Investigations on the Seismic Behavior of a Reinforced Concrete Frame Structure

Recent seismic events that took place during the past two decades and struck densely populated areas caused significant material losses and, sometimes, casualties. Taking into account the ageing of the building stock around the world coupled with unavoidable degradations, urgent measures need to be taken to either strengthen or retrofit such structures based on data obtained from analytical, experimental or numerical investigations. The present paper presents the results of numerical simulations, using time-history analyses, on a scaled-down reinforced concrete (RC) frame structure subjected to two multidirectional seismic scenarios. The obtained results are discussed from the point of view of maximum displacements, accelerations and equivalent stresses. Considering the dynamic characteristics of the model, neither considered seismic event were able to produce large lateral displacements or accelerations. Damages were localized at the beam-column joints in case of Turkey 2023 earthquake scenario.

Structural performance of detachable precast concrete column-column joint

A novel type of detachable precast concrete column-column joint (DPC) is proposed in this study to solve the problems in current column-column dry connections including complex load path, uncertainty of structural stiffness of beam-column joints and inconvenience for disassembly. The dry connection technology is applied by composing of steel plate and concrete. Finite element models of DPC were created to study its structural performance including hysteresis curve, skeleton curve, ductility, and energy dissipation capacity. The benchmark models are firstly established and validated against the test data and after that a small-scale parametric study is prepared. The effect of axial pressure ratio and eccentricity distance size on the seismic performance of DPC was studied. Results indict that the optimal value of axial pressure ratio ranges from 0.5 to 0.7. With increase of the axial pressure ratio, the ductility coefficient shows a decreasing trend in general. The eccentricity has little effect on the energy dissipation capacity of the joint.

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.