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A beam column junction is a key zone in a reinforced concrete moment resistant frame. It is exposed to a huge deal of stress throughout severe ground motion, and its performance has a noteworthy impact on the structure’s reaction if the ductility is inadequate, resulting in serious structural collapse. Use IS code 13920:1993 and provide ductile reinforcement according to ductile detailing of reinforcement beam column junction and ductile detailing of reinforcement beam column junction to improve the ductility of conventional beam column joints. The dimensions of the beam column junction are 700 mm*700 mm with a c/s of 200 mm*100 mm. The specimen will be cast in concrete to M30 specifications.

Studies on the performance of structures under cyclic loads have attained great significance in the recent past, in the context of increased structural damages during disasters like earthquakes. A closer observation of such damages with particular reference to R.C framed buildings reveals that beam-column junctions are very crucial in determining the performance of the total building structure subjected to cyclic loading. An experimental study is taken up in the present work to stimulate cyclic load on structural models of R.C beam-column junctions and investigate the influence of certain key parameters on their performance. Three commonly found field practices viz., Normal detailing at the junction, ductile detailing at the junctions and defective workmanship at the junction, are chosen for the study. IS 13,920 guidelines are adopted for ductile detailing while use of M−20 mix in place of supposed M30 grade to be used, is adopted as indicator of defective workmanship. Responses of the specimens were noted in terms of load-deflection behavior, first cracking, complete crushing, number of cycles taken for failure etc. From the results obtained, the performance of the specimens were noted in terms of load-deflection hysteresis loops, cracking pattern and behavior, stiffness degradation, ductility factor and energy absorption. It is observed that the specimens with good workmanship and ductile detailing are performing better under cyclic loads.

This paper presents a numerical investigation to study the seismic response of shear deficient beam column joint (BCJ) strengthened with ultra high performance fibre-reinforced concrete (UHPFRC) and/or carbon fibre-reinforced polymer (CFRP) sheet. Two strengthening schemes were planned: (i) cast-in situ UHPFRC layer of 30 mm thickness over normal concrete and (ii) cast-in situ UHPFRC layer over normal concrete followed by CFRP wrapping over the joint area of BCJ. The seismic performance of strengthened BCJs under reverse cyclic loading was determined in terms of hysteresis response, strength and stiffness degradation, ductility and energy dissipation capacity. The strengthened BCJ specimens were tested at two drift ratios, i.e. ± 5% and ± 8.7%, higher drift ratio was chosen to examine the efficacy of strengthening at higher displacements. From the numerical modelling results, it is clear that BCJ strengthened with the second scheme involving the synergistic action of UHPFRC and CFRP can increase their structural stiffness, strength and energy dissipation capacity of BCJ in contrast to other strengthening scheme. The enhanced performance is attributed to superior properties of UHPFRC as a strengthening material, and the role of CFRP, which helped in maximizing the potential of UHPFRC by providing confinement to the concrete thus delaying the damage and resulting in increased energy dissipation.

Three equivalent exterior precast concrete beam-column (PCBC) connections have been investigated in this study in orderto analyze the effect of steel fiber reinforced concrete (SFRC) as cast-in-place (CIP) on the seismic performance of the PCBC connection. The connection was designed as a ductile connection for a moment-resisting frame and consists of a precast U-beam, precast column with corbel, interlocking bars, and CIP-concrete to connect the precast beam to precast column. The volume fractions of steel fiber incorporated within the CIP-concrete were 0%, 0.5% and 1%. A quasi-static load was applied vertically to the beam tip of the PCBC specimen. The results showed that the steel fibers contained within the CIP-concrete provided 2% increase of the maximum load, 17.7% increase of the energy dissipation, and increase in the joint stiffness of the PCBC connection. The steel fibers delayed the onset of cracking and slowed down the crack propagation, resulting in shorter cracks in the joint core of PCBC specimen, which correlates well with the deflection-hardening characteristic found from the modulus of rupture test.

Structure safety is of utmost importance in modern days. Now- a- days ferrocement is gaining popularity as a retrofitting material due to ease of its application and availability. The most critical location of failure in any structure is beam column joint. The aim of this paper is to analyse the effect of retrofitting on beam column joint using ferrocement as a retrofitting material. Square wire mesh and triangular wire mesh was used for retrofitting beam column joint. Beam column joint is designed using ductile detailing code IS 13930:2016. Axial and reverse cyclic displacement load is applied on the specimen. Further unstrengthen and strengthened specimen were analysed using ANSYS software. A comparative study was done and it was concluded that after retrofitting, the specimen shows considerable decrease in total deformation. It shows that retrofitted beam column joint was more stable than the unstrengthened beam column joint. So, to increase the serviceability of any structure it is recommended to retrofit the structure. Keywords: BCJ, ferrocement, wire mesh, retrofitting

In practice, it is common for circular concrete-filled CFRP-steel tube (C-CF-CFRP-ST) member severing under eccentric load, but there are few related investigations on its mechanical behavior currently. In this study, experimental study and finite element analysis are employed to reveal the static behavior of circular concrete filled CFRP-steel tube under eccentric compression. Total 32 C-CF-CFRP-ST specimens, taking the slenderness ratio (λ) and eccentric ratio (e) as principal parameters, were designed and tested firstly, obtaining the failure modes, N-um curve and the strains in the steel tube and CFRP It was found that the damage of concrete became more serious with the decrease of the slenderness ratio but got mitigated with the increase of eccentricity. Additionally, it was indicated that the N-um curve of C-CF-CFRP-ST consisted of three stages, namely elastic stage, elastic-plastic stage and plastic stage. In the elastic-plastic stage, the damage is gradually accumulated in CFRP and concrete, and the specimens finally exhibited ductile failure in the end of plastic stage. In the entire loading process, CFRP has almost same strains compared to the steel tube. Following the experimental study, finite element analysis was conducted to investigate the static behavior of C-CF-CFRP-ST comprehensively. The proposed finite element model reproduced the compressive behavior of C-CF-CFRP-ST, in terms of failure modes and N-um curves. The influence of material strength, layers of CFRP and steel ratio on the static behavior of C-CF-CFRP-ST specimens were then studied through numerical parametric study. In the end, equations for predicting the bearing capacity of C-CF-CFRP-ST are proposed, and the predicted static strengths of the specimens are basically consistent with the experimental results.

Existing reinforced concrete (RC) beam–column joints, which are designed mainly to resist gravity load, may encounter serious problems in low to moderate seismic regions. The moderate earthquake in Ranau, Malaysia, affected numerous old buildings, mainly manifesting as uncontrolled crack propagation in RC members at the beam–column joint. Effects of shear reinforcement between shear link spacing on crack formation on four RC beam–column joints were investigated under cyclic lateral loading with acoustic emission (AE) monitoring. The control specimen (BCJ-1), which was designed in BS-8110, showed more irregular cracks thus concrete cover spall was observed at an earlier drift ratio (DR) level than for other specimens with additional shear reinforcement between shear link spacing. Sudden drop of AE hits beyond 2.25% DR level with a significant increase in crack width showed that BCJ-1 was no longer able to resist higher loads due to de-bonding between reinforcement and concrete. From the rise time/amplitude against average frequency (RA-AF) graphs, the mode of failure was determined according to DR stages concerning crack characteristics.

The impact of reinforced concrete beam-column joints on the shear strength of a building under cyclic loading depends on the types of joints applied. This study considers models of the uniaxial and biaxial joint shear strength of exterior beam-column joints. Prediction models of the uniaxial shear strength under uniaxial cyclic loading based on ACI 352, ASCE 41, and gene expression programming (GEP) have been developed. The ACI 352, ASCE 41, and GEP formulas have the potential to achieve improved results. This study considers a means by which to improve the results of previous models through a proposed deep neural network (DNN) model with three hidden layers among the artificial neural network structures. The R-squared value and mean absolute error determined through this DNN model are 97.94% and 34.13% for the uniaxial model and 98.28% and 2.70% for the biaxial model, respectively. These results indicate that the DNN model is more suitable than the ACI 352, ASCE 41, and GEP models for joint shear strength predictions.

In this study, experiments were carried out to evaluate the seismic performance of a hybrid prestressed precast concrete (HPPC) system devised to ensure the integrity of precast concrete (PC) beam-column joints by introducing the post-tensioning method. A total of four full-scale HPPC beam-column joints were fabricated, and the presence of a topping slab, a post-tensioned length, and a type of tendon were set as the main variables. The quasi-static cyclic loading tests were performed to analyze the load-story drift ratio response, failure mode, ductility, residual deformation, and energy dissipation capacity of each specimen. The seismic performance of the specimen was then quantitatively evaluated based on the acceptance criteria of the ACI 374 report. The shear strength estimation model for the HPPC beam-column joints was also proposed and the proposed model was verified in detail using the test results.

Technological developments have facilitated the production of high-strength reinforcements (HSRs) with increasingly appropriate characteristics. The application of HSRs has many benefits, one of which being a decrease in overall construction expenditures. In this research, the influences of HSRs (with yield strengths of 500 and 580 MPa) as longitudinal and transverse reinforcements in three beam–column joints were experimentally studied. The effects of the HSRs on drift, stiffness degradation, displacement, energy dissipation, ductility, cracking patterns and damage indices (DIs) were investigated. The experimental results showed that all the specimens achieved drift ratios in excess of 4% before they showed a critical decay in lateral strength. The energy dissipation and ductility of the specimens were also reduced with the use of HSRs. However, HSR application as stirrups showed better effects than HSR as longitudinal reinforcement. Regarding DIs and stiffness degradation, it was found that the application of HSR increased the intensity of the damage distribution in the specimens. Finally, although crack numbers decreased by using HSRs, the crack widths and depths increased.

This study aimed to investigate the structural behavior of castellated beam-column steel elements. The benefit of castellation laid in increasing the section’s depth to induce an increase in the moment of inertia Ix and the section modulus Sx without the slightest increase in the element weight. Most of the previous researches focused on castellated beams but only few concentrated on beam-column elements. An experimental investigation was performed on twelve short and long castellated beams, columns and beam-column elements. The results of the performed experimental work were compared to the finite element analysis (FEA) to validate the applicability of FEA as a numerical tool. FEA was found to be in favorable agreement with their experimental counterparts. In this research, the behavior and strength of the castellated beam, columns, and beam-column elements were investigated by means of the verified finite element modeling. The various parameters taken into consideration in this research were respectively; load eccentricity, element length and castellation ratio.

PurposeSteel fibers reinforced concrete (SFRC) is now widely accepted as a construction material for its added benefits. The proven increases in high shear capacity, toughness, bridging action of fibers and bond improvement from addition of steel fibers into mix design is a field yet to be explored, Therefore, Reinforced Cement Concrete (RCC) beam-column joint with steel fibers was modeled and analyzed for cyclic loading.Design/methodology/approachBeam-column joint is the most critical section of a structure under mixed loading such as that during a seismic episode. Therefore, in this research a reinforced SFRC beam column joint is modeled and analyzed for cyclic earthquake loading with the help of finite element analysis (FEA) software ABAQUS to compare the results with the experimental study.FindingsNonlinear static and nonlinear dynamic analysis are carried out on the SFRC joint for the comparison of simulated results with the experimental analysis.Originality/valueIn this paper, Initially, modeling of SFRC joint was done. Then, the finite element analysis of beam-column joint with steel fibers was carried out. After number of simulations, obtained FEA results were compared with the experimental work on the based on the load vs deflection curve, shear stresses, plastic strain region and plastic strain pattern. After the comparison, it was found that the performance of the numeric model for cyclic loading verified the experimental study, and the results obtained were quite promising.

This paper presents and discusses the development of a numerical model which investigates the enhancement of overall stiffness and stress distribution in welded connections under cyclic loading. The structure under investigation, described in four fully welded T-joint (BCC5) specimens. The four specimens were modeled under different displacement loading using a finite element analysis program Solidworks and Ansys software in conjunction with test data obtained from the University of Lisbon, which was validated with the test results by matching the hysteresis loops, maximum high strain, and maximum stress at the crack location steel joint specimens. The comparison between the analysis and test results showed good agreement and also showed that the maximum strain in the enhanced model is less than the maximum strain on the base model, and the location of maximum strain is moved to the gusset plate rather than the weld zone, therefore the gusset plate makes the joint in the enhanced model more ductile than the joint in the base model. Life cycles to failure for the enhanced model are more than life cycles to failure in the base model. It is therefore found that this has useful applications in the steel construction industry.

In order to investigate the influence of panel zone section size on the plastic damage distribution of H-shaped beam-column joints, a cruciform beam-column joint composed of common beams, columns a...

In the present study, the consequences and effects of CFRP-strengthening on the dynamic response of a seismically deficient building were investigated under the ground motion acceleration of selected earthquake using pushover and nonlinear time history analyses. A reinforced concrete frame building located in the Gulf of Aqaba region in Saudi Arabia, classified as a seismically active region, was selected for the study. The study building, initially designed for gravity loads only, was subjected to earthquake forces. The analysis showed that most of beam-column joints are deficient for earthquake loading and thus require strengthening. CFRP-sheets were used for seismic rehabilitation to enhance the properties of the seismically deficient building members. The number of required layers of CFRP sheets was estimated following the guidelines of ACI 440. The seismic suitability of strengthened members was then evaluated with the help of pushover and dynamic time-history analyses to verify the adequacy of CFRP-Strengthening. Numerical analysis carried out with the help of SAP 2000 program. The results of the study showed that the CFRP-strengthening of beam-column joints delayed the formation of the plastic hinges, efficiently controlled the inelastic deformation at the critical plastic hinge locations, and significantly improved the seismic performance of the building without adversely affecting the overall dynamic response.

The performance of beam-column joints in reinforced concrete (RC) framed structures have long been recognized as a significant factor that affects the overall response of structure subjected to cyclic loads. The reversal of forces in beam-column joints during earthquakes may cause distress and often failure, when not designed and detailed properly. The present work aims to study the seismic performance of exterior beam column joint with non-conventional reinforcement detailing. Four one third scaled beam-column joint sub assemblages were tested under reverse cyclic loading applied at beam end. The specimens have been looked after into two groups based on the joint reinforcement detailing. The first group of two specimens (Group-I) comprises of joint assemblages having joint detailing as detailed in construction code of practice in India i.e. IS 456:2000. The second group (Group-II) consists of two specimens, one of the specimens having additional cross bracing reinforcements for the joint detailed as per IS 456:2000 and another specimen having diagonal bars in form of development length. Here comparison between conventional and non-conventional type reinforcement has been done to study its effect on strengthening of joint. The experimental results and findings indicate that additional cross bracing reinforcements improves the seismic performance.

Cyclic loading behaviour of RC beam-column joints strengthened with externally bonded Carbon Fiber Reinforced Plastic (CFRP) was analysed through Abaqus CAE software. Effect of the number of CFRP layers and the strengthening technique on failure modes, hysteretic curves, skeleton curves, ductility, and energy dissipation capacity were studied. The results show that the strengthening of RC beam-column joints by externally bonded CFRP can effectively improve the cyclic loading behaviour. Strengthening the joint by fiber bands enhances ductility and energy absorption capacity. The increase in the number of CFRP layers leads to enhance energy absorption capacity significantly as compared to ductility.

In this study, a theoretical analysis is presented for estimating the in-plane geometric nonlinear elastic stability behavior of steel members with tapered elements under dynamic loads. Beam-column approach is adopted for modeling the structural members as beam-column elements. The formulation is based on the Eulerian description taking into consideration the influence of axial force on bending stiffness. The changes in member chord length due to axial deformation and flexural bowing are also considered. In the dynamic analysis, the system mass properties have been represented using both lumped and consistent mass matrices. The consistent mass matrix is derived in three components: translational, rotational, and axial inertia. The formulation of the mass matrices in local and global coordinate systems of tapered members, which incorporates geometric nonlinearity, has been presented. A parametric study is conducted to examine the effects of number of tapered elements, tapering the prismatic members, time step size, and tapering ratio. The dynamic responses of tapered members have been shown to be significantly affected by these parameters.

The seismic retrofit of existing reinforced concrete (RC) beam-column joints in the case of the interior reinforcement of deformed bars and plain bars, as well as the decision regarding convenient ...

This paper investigates the experimental and analytical behaviour of beam-column joints that are subjected to a combination of torque, flexural and direct shear forces, where different Carbon Fibre Polymer (CFRP) strengthening wraps have been applied only to the beam. These wrapping schemes have previously been determined by the research community as an effective method of enhancing the torsional capacities of simply supported reinforced concrete beams. In this investigation, four 3/4-scale exterior beam-column joints were subjected to combined monotonic loading; three different beam wrapping schemes were employed to strengthen the beam region of the joint. The paper suggests a series of rational formulae, based on the space truss mechanism, which can be used to evaluate the joint shear demand of the beams wrapped in these various ways. Further, an iterative model, based on the average stress-strain method, has been introduced to predict joint strength. The proposed analytical approaches show good agreement with the experimental results. The experimental outcomes along with the adopted analytical methods reflect the consistent influence of the wrapping ratio, the interaction between the combined forces, the concrete strut capacity and the fibre orientation on the joint forces, the failure mode and the distortion levels. A large rise in the strut force resulting from shear stresses generated from this combination of forces is demonstrated and leads to a sudden-brittle failure. Likewise, increases in the beams’ main steel rebar strains are identified at the column face, again influenced by the load interactions and the wrapping systems used.

In the present study, an experimental and theoretical investigation is carried out on the reinforced concrete exterior beam-column joints strengthened with the hybrid fibre reinforced polymer (HFRP). The effect of reversible distress that develops in the joint region due to seismic force is determined experimentally by applying reverse cyclic loading on the tip of the beam. In theoretical analysis, the shear strength of strengthened joints was determined, and satisfactory correlations with experimental results were established. Hence, the proposed physical model provides valuable insight into the strength behaviour of the joints.

In a post-tensioned precast concrete beam–column connection, the precast beams are post-tensioned to ensure the integrity of the connection and to provide recentring characteristics when the connection is subjected to seismic loads. In this study, the post-tensioned precast concrete beam–column connections were tested under reverse-cyclic loading with the test variables of grout strength at the beam–column interface and prestressing stress of stands. The test results showed that the post-tensioned precast concrete beam–column connections have a seismic performance equivalent to that of a conventional reinforced concrete beam–column connection. When high prestress is applied, however, confinement reinforcement is required at the beam ends to secure sufficient deformation capacity without crushing of concrete. An analysis model for post-tensioned precast concrete beam–column connections is also proposed; the model considers the bond properties of prestressing strands, and provides good agreement with the experimental results.

A large number of low to moderate earthquake incidents have been witnessed in the northern and western parts of Thailand. These incidents usually lead to various damage levels in various structures. Therefore, a sufficient lateral force resisting structures should be designed for the construction in such earthquake-prone areas. This paper presents the relevance of using a typical composite wide U beam-column system for mitigation of structural failure and collapse from the seismic hazard in Thailand. The investigated composite structural system consists of precast U beams, precast columns, and cast-in-situ concrete over the precast U beams and in the joint regions. The system also includes post-tensioning in the cast-in-situ area of the composite beams. The system has widely been used in low- to mid-rise commercial building in Thailand. In order to scrutinize the seismic performance of the system, a half-scale specimen of the post-tensioned precast U beam-column joint was tested under an incremental displacement-controlled lateral cyclic load. The laboratory test revealed the drift capacity, damage pattern, strain development in the rebars etc. of the precast wide U beam-column interior joint. Based on the obtained drift capacity, displacement-based assessment of the system was carried out. In addition, the observed damages on the tested structure were evaluated using damage grading criteria for building subjected to earthquake. The assessment showed a high potential of the post-tensioned precast wide U beam-column system to mitigate the structural failure and collapse from the earthquake hazard. However, some improvements in the current seismic performance of the system are required to employ the system in high seismic zones.

This study aimed to investigate the moment carrying behavior of typical Tibetan timber beam-column joints under monotonic vertical static load and also evaluate the influence of length ratio of Gongmu to beam (LRGB) and dowels layout on the structural performance of the joint. Six full-scale specimens were fabricated with same construction but different Gongmu length and dowels position. The moment carrying performance of beam-column joints in terms of failure mode, moment resistance, and rotational stiffness of joints were obtained via monotonic loading tests. Test results indicated that all joints are characterized by compressive failure perpendicular to grain of Ludou. Additionally, it was found that greater LRGB leads to greater initial rotational stiffness and maximum moment of the joint by an increase of restraint length for beam end; however, offsetting dowels toward column resulted smaller stiffness and ultimate bending moment of joints, particularly, offsetting Beam-Gongmu dowels toward column changed the moment-rotation curve pattern of the beam-column joint, accompanied by a hardening stiffness at last phase. Furthermore, a simplified trilinear model was proposed to represent the moment-rotation relationship of the typical Tibetan timber beam-column joint.

This paper presents a nonlinear finite element analysis of RC beam-column joints. A numerical study carried out through a simulation on beam-column joints failed in flexure presented by experimental study. A verification procedure was performed on two joints by finite element analysis with ANSYS APDL. The verification with the experimental work revealed a good agreement through the load-displacement relationship, ultimate load, and displacement, and crack pattern. Also, the parametric study was implemented which including strengthening the concrete members by a variable ratio of steel fibers with normal ratios (0.5%, 1%, 1.5%, and 2%) and ratios of slurry infiltrated fiber concrete SIFCON (steel fibers up to 4%, 6%, and 8%) in addition to using of partial and full strengthening with and without stirrups. The test results revealed that steel fibers enhanced the flexural strength and ductility of the tested joint. Increase the ratio of steel fibers increased the flexural capacity by (101%, 153%, 177%, and 193%) for the four normal ratios of steel fibers respectively. SIFCON concrete ratios (4%, 6%m and 8%) enhanced ultimate strength by (521%, 802%, and 906%) respectively. The use of steel fibers reinforcement instead of steel rebar enhanced the ultimate load capacity by (101%) with large displacement. Full strengthening method by use of SIFCON presented pure flexural failure with cracks spread in the joint region but use the SIFCON concrete as a partial strengthening changed the failure mode to the shear failure.

Due to the frequent occurrence of natural disasters and terrorist attacks, research on resisting progressive collapse has attracted increasing attention from the engineering and academic communitie...

This paper presents the effect of sisal-fiber reinforced concrete in exterior beam-column joints under monotonic loading. Fifteen exterior beam-column joints were designed per British standard using the strong column-weak beam concept. Sisal fibers were added to the concrete mix at 0.5%, 1.0%, 1.5% and 2.0% by weight of cement. The performance of the joints was observed under gradually increasing load. The result shows that in comparison to the control specimen, exterior beam-column joints with sisal fiber have a higher yield and ultimate load, exhibited lower deflection, and showed improved shear strength. The shear strength of the joint was compared with theoretical models proposed by previous studies The proposed models did not accurately capture the effect of the fiber, hence, a modification was proposed and tested to improve joint shear strength of sisal-fiber reinforced concrete in exterior beam-column joints.

The high-strength bolted end plate connection is widely used in the construction industry with its green environmental protection and excellent seismic performance. The joints of the joints are semi-rigid, the force performance is extremely complicated, and the experimental research cost is relatively high, and the cycle is very long. Therefore, the establishment of an efficient numerical model is of great significance for evaluating the force performance of high-strength bolt end plates. In this paper, the influence of different material models on the rotation performance of the joint is studied by numerical simulation, and the bending moment-rotation curve is obtained. The numerical simulation and the experimental results are in good agreement, so as to provide a reference for the design and application of this kind of joint.

In the design of steel or composite structures, the connections are usually considered infinitely rigid or perfectly pinned. However, the real behavior of these connections is semi-rigid. Consequently, this semi-rigidity can influence the overall behavior of the composite structures, especially the moment-resisting frames. Seismically, the most critical parameter that characterizes the frames behavior is the response factor R. In this context, the research work consists of studying the semi-rigidity effect of the connections on the behavior of the composite frames by evaluating the response modification factor R by using the Pushover method. To accomplish this task, three types of portal frames of 3, 4 and 5 storeys were analyzed for different degrees of connection (beam-column). An easy and practical solution has been proposed to determine the approximate value of the coefficient behavior R for the composite frames with semi-rigid connections.

Code requirements are usually fulfilled during the design of a building. On the other hand, reinforced concrete (RC) frames (particularly in the developing regions of the world) are found deficient due to unregulated constructions. Majority of such deficient structures lack shear reinforcement in beam-column joints. Collapse of these deficient buildings (as a result of limited ductility) triggered many socio-economic and human losses which is evident from recent earthquake disasters. This paper presents an experimental study which was conducted on a 1:4 reduced scale three-storey RC special moment resisting frame (SMRF) lacking shear reinforcement in the beam-column joints. The lack of confinement bars causes shear hinging of joints that reduces the displacement ductility of the frame. Shake-table tests were conducted on test model that was subjected to acceleration time history of 1994 Northridge earthquake, having a peak ground acceleration of 0.57g. The acceleration was linearly scaled to multiple levels and to sinusoidal base excitations of various frequencies and displacements. Moderate to severe damage at each storey level was observed in the joint panels due to the lack of lateral reinforcing ties in the joints. The data obtained from shake table tests were processed and analysed to develop a lateral force-deformation capacity curve, which was bi-linearized as an elasto-plastic curve to compute various response parameters of frame. The ductility factor (Rμ) of the tested model was found to be equal to 1.95, which is thirty-five percent less than the code recommended value of Rμ for RC SMRF structures.

This article investigates the effectiveness of geogrid material on upgrading the cyclic performance of nonductile exterior reinforced concrete (RC) beam-column joints by experimental observations and non-linear finite element simulations. Conventional RC beam-column joints without seismic detailing confined internally with geogrid material and compared these specimens with control RC beam-column joint specimens with and without seismic detailing. A detailed 3D non-linear finite element (FE) analyses of the RC beam-column joints internally confined with geogrid in ANSYS are carried out. All the beam-column specimens are subjected to reverse cyclic loading under controlled amplitudes to explore the cyclic performance on the parameters such as failure patterns; load–displacement envelope curve; ductility factor. The test results showed that internal geogrid confinement are effective for enhancing the load-carrying capacity and also ductility of the test specimens. The load–displacement behaviour and damage predicted from finite element analysis almost show the similar behaviour with the experimental result. Hence geogrid with conventional steel bar can be used as a hybrid reinforcement which having excellent ductile behaviour for increasing the seismic performance of RC beam-column joints.

This paper presents the high-fidelity finite-element-based numerical models for modeling the behavior of prestressed concrete (PC) beam-column substructures to resist progressive collapse under column removal scenario. After careful calibration against data, the validated numerical models are further employed to shed light on the influence of bonded post-tensioned tendons (BPT) with a parabolic profile on the load transfer mechanisms of PC frames against progressive collapse. The effects of parameters, including initial effective prestress, profile of tendon and lateral constraint stiffness at the beam ends, are also investigated. The study shows that, due to the presence of prestressed tendons, the mobilization of compressive arch action in the beam at small deflections demands stronger lateral constraints, and the ultimate load resistance of PC beam-column substructures depends on combined catenary action from non-prestressed reinforcement and BPT at large deflections. For a given constraint stiffness, the initial effective prestress of BPT has less significant effect on the overall structural behavior. For prestressed tendon, a straight profile usually employed in structural strengthening can improve the initial structural stiffness and yield strength, but is less effective in enhancing the ultimate resistance against progressive collapse than the parabolic profile.

The structural performance of a frame joint is particularly important, which can determine the safe state of the global structure. For this reason, the seismic performance of the truss steel reinforced concrete (SRC) beam-column frame joints is investigated by the experimental study and the nonlinear finite element modeling. The main design parameters include the section size of the web rods, the axial compression ratio and the section size of I-steel. The failure mechanism, load-displacement skeleton curve, the ductility and energy dissipation capacity, and shear deformation in the core zone of the truss SRC beam-column joints are studied. A formula is put forward to describe the shear bearing-capacity of the joints. The results indicate that the truss SRC beam-column frame joints generally have good seismic performance. The size of steel and web members have impact on the seismic performance of the truss SRC beam-column joints, and the axial compression ratio is an important factor that impacts the hysteresis behavior and energy dissipation. The proposed shear bearing-capacity formula can objectively reflect the performance of the joints.