Figure 4-9 showed the load versus displacement. Unfortunately during the test, two problems occurred: (1) One of the pressure sensors that was recording the load from the pushing hydraulic line, and this caused an erratic response in this part of the figure. (2) In the second phase of loading (strain control phase), some displacement data were not recorded because the tip of the beam moved away from the LVDT plunger. In these cases, data were not recorded, hence the plot shows no displacement for the earlier portion of loading in this phase. Based on the pushing up part in the Figure 4-9 above, specimen J1 showed that the load and displacement changed in a linear manner within the first twenty load cycles. After first cycles, flexural cracks at the interface between the column and the beam were created where the plastic hinge was supposed to form according to the design. The cracks’ width at this plane increased as the load progressed in the cycles. Meanwhile, some diagonal cracks developed within the joint region as well. As expected, at the start of the strain control phase of the load sequence, the specimen was still healthy, and not losing any strength especially in the first load cycle. The maximum load that the specimen was subjected to was at this cycle. At cycle 39 which represented last cycle in this test, the cyclic load dropped to about half compared with the maximum load. This could be a sign that the strength was beginning to
Guo-Lin Wang, et.al (2012) this paper presents a new shear strength model for reinforcedconcrete (RC) beam–columnjoints subjected to cyclic lateral loading. In the proposed model, the reinforcedconcrete in the joint panel is idealized as a homogenous material in a plane stress state. The contribution of the joint shear reinforcement (including both the transverse steel reinforcement and the intermediate longitudinal steel reinforcement of the column) is taken into account through the nominal tensile strength of the idealized material.
In this study, the effect of fibre reinforcedconcrete in exterior beamcolumn joint with and without basalt fibre under cyclicloading. And the fibre used in this study is basalt fibre, which is more efficient than other fibres. Mechanical properties like compression, split tension, flexural and impact load test were carried out. Cumulative energy dissipation of all mixes was taken. High performance concrete of M60 grade used. Fibres are used in different percentage (0.75%, 1% and 1.25%) with the volume of concrete. Mechanical properties of the concrete were discussed and the behavior of beamcolumn joint was studied under cyclicloading. To increase the energy absorption and load bearing capacity of the beamcolumn joint ductile detailing is provided. With the load vs deflection, beamcolumn joint curvature is made to find the load bearing capacity. Use fibre to the concrete will reduce the size of crack pattern during failure. The result shows that behavior of beamcolumn joint shows better performance. The studied properties are discussed and the fibre used shows the increase in strength with addition of different percentage of fibre respectively by cyclicloading.
By connecting the maximum story drift points corresponding to each displacement level, the load-story drift envelope curve is obtained. In Figure 14a and b, the load-story drift envelope curve of the specimens reinforced with steel and FRF are illustrated. ACI Committee  suggested provisions for a connection to be accepted as an element of a moment resistant frame in seismic regions. Based on this code, in the third cycle in which the drift of 3.5% is obtained, the maximum applied load in each loading direction should not be less than 75% of the maximum lateral strength in the aforesaid direction to satisfy the fracture criterion. Moreover, the observed energy ratio should not be less than 0.125, and the secant stiffness about zero (the secant stiffness corresponding to the drifts ranged from -0.35% to 0.35%) should not be less than 5% of the initial stiffness at the first cycle of the aforesaid direction. Based on Figures 14a and b and the requirements of ACI Committee , the seismic behavior of the specimens were assessed. Accordingly, the behavior of the specimens reinforced with the steel bars is acceptable. Moreover, the specimens reinforced with the FRP bars satisfied the acceptance criteria of ACI Committee , and the behavior of the specimen 7 and 8 with high strength concrete were acceptable as well. Note that; the specimens 5 and 6 did not satisfy the criteria of the 3.5% drift. Hence, they could not be accepted. According to Corley’s suggestions , the performance of specimens 5 and 6 was not satisfactory. Corley  suggested the third cycle in which the drift of 3% was occurred for satisfying the fracture criterion. In this displacement, the connection behavior ought to be stable. Specimens 5 and 6 were not able to reach the drift of 3% although the behavior of specimen 5 was stable in drifts beyond 3% due to the compressive forces. Based on the load-story drift envelope curves, usage of GFRP bars in connection showed an acceptable drift capacity, assuming a minimum drift demand of 3% as suggested in the literature for ductile frame structures .
The state-of-the-art regarding repair and strengthening techniques for reinforcedconcretebeam-columnjoints has recently been reviewed by Engindeniz et al. (2005). This paper is focused on seismic rehabilitation of generic reinforcedconcrete (RC) joints with examples pertaining to actual bridges. Of particular interest are experimental and analytical studies regarding the seismic behavior of T-joints in multi-column bridge frames constructed in the 1950’s and 1960’s. The dimensions and reinforcement details of RC bridges constructed during this time make them vulnerable to failure in strong ground shaking during large earthquakes. T-joints in multi-column bridge frames, involve larger column and cap beam cross-sections, larger diameter steel reinforcement, and different geometry and anchorage conditions compared to joints in RC buildings. Moreover, in RC bridges yielding of column reinforcement is preferred rather than yielding of beam reinforcement, as is the usual case in RC buildings. The application of carbon fiber reinforce polymer (CFRP) composite jackets for the three columns and cap beam T- joints of an existing RC bridge pier, which was performed in Salt Lake City in 1996, was investigated by Gergely et al. (1998). The evaluation of the pier in the as-built condition, the rehabilitation objectives, and the CFRP wrap design were achieved by performing a pushover analysis of a structural model of the bridge pier. It was found that the shear capacity of the T-joints and the displacement ductility of the bridge pier were improved significantly. In addition, a comparison was made between analytical results and full-scale experiments of CFRP composite retrofitted T-joints carried out by Halling et al. (2001). Lowes and Moehle (1999) studied two methods for retrofitting beam-column T-joints in RC bridge structures. In the first method, addition of RC bolsters to the cap beam and joint was used; the retrofitted T-joint displayed moderate ductility capacity under simulated earthquake and gravity loading. In the second method, a post-tensioned concrete retrofit connection involving addition of post- tensioned concrete bolsters to the cap beam and joint was used; the retrofitted T-joint displayed large ductility under simulated earthquake and gravity loads. The post-tensioning improved both joint shear strength and column longitudinal reinforcement anchorage strength.
where a local stress concentration appears in the steel, may result in overestimating the structural response in the post-yielding range. Since this phenomenon is accelerated with increased deformation, an analysis of RC members subjected to cyclicloading accompanying relatively large deformations requires the use of average stress-strain relations. Accordingly, the average stress- strain relation of steel needs to be dened for tracing the cracking behavior of RC beams and/or columns up to the ultimate limit state. This can be accom- plished using a smeared crack model in which the local displacement discontinuities at cracks are distributed over some tributary area within the nite element, and where the behavior of cracked concrete is represented by the average stress-strain relations. Considering these factors, the following linear average stress-strain relation, introduced by Belarbi and Hsu  from experimental data, is used:
to the crack) and, therefore, it was modelled using the “shear retention” part of ABAQUS  concrete model. The shear stiffness of the concrete decreases when crack is propagated. Therefore, in order to allow for degradation in shear stiffness due to crack propagation, the shear modulus was reduced in a linear fashion from full shear retention (i.e. no degradation) at the cracking strain to 50% of that value at the ultimate tensile strain. The “brittle cracking model” in ABAQUS  was adopted for the present work. The model is designed for cases in which the material behaviour is dominated by tensile cracking as is normally the case for structural concrete. To make the numerical solution even more efficient, the analysis is usually carried out using the dynamic solver as a quasi-static one (i.e. with a low rate of loading). Therefore in the present study, “brittle cracking model” was used in conjunction with the explicit dynamic procedure available in ABAQUS/Explicit. This was one of the practical reasons for selecting the model for the present investigations of SFRC behaviour under reversed-cyclicloading. Moreover, the model was successfully used to predict the responses of different SFRC forms such as simply-supported beams, statically- indeterminate elements as well as the present study of joints. The studies have shown that the model is capable of predicting both brittle (i.e. shear) and ductile (i.e. bending) forms of failure, as described fully elsewhere [15, 16, 17].
After 28 days, the concrete cover around the joint was removed for the nine exterior specimens using a small hand-held chipping hammer. The removed cover extends 300 mm in the beam and 300 mm in the column above and below the joint. The surface of steel reinforcement was exposed and cleaned (see Fig. 5(a)). The edges of the removed cover were kept curved and roughened to prevent stress concentration. For the specimens prepared for retroﬁtting, staggered holes were drilled in each specimen in predeﬁned lo- cations (10–15 cm apart) as shown in Fig. 5(b) and (c)). Each hole of diameter 8 mm penetrated the core with 50 mm depth. The inner surfaces of the holes were roughened and cleaned from loose concrete pieces and dust using compressed air. The mixed anchoring grout was poured steadily into holes and a 6 mm galvanized high strength threaded bars (steel dowels) were inserted inside the holes to ensure composite action between the ferrocement layer and concrete core (see Fig. 5). The retroﬁtted specimens were wrapped by one layer of wire mesh (with overlap of 100 mm) as shown in Fig. 6. The expanded wire mesh was ﬁ xed to the embedded 6 mm, shear connectors by washers and nuts. The strengthened specimens were plastered with a thin layer of rich cement mortar (650 kg of Portland cement per 1m 3 of well graded sand with 0.4 as water cement ratio). The wrapped specimen was cured by water for 4 days. The same process was repeated for each layer of ferrocement. The specimens EJANG1, EJANG2, and EJANG3 were
In the last two decades, the study of reinforcedconcrete (RC) structures ele- ments such as bridge deck slabs, bridge girders, or offshore installations, which are subjected to cyclic action typically induced by seismic motions has received the attention of many researchers. Furthermore, the past two dec- ades have witnessed rapid growth in the use of fiber-reinforced polymer (FRP) confining jackets for the strengthening/retrofit of reinforcedconcrete (RC) columns and beams. Moreover, several theoretical and empirical models have been proposed for evaluating the shear strength of beams, columns and beam-to-columnjoints. In this paper, an overview of the models currently available in the scientific literature for evaluating the shear capacity of beams, columns and exterior beam-to-columnjoints is reported. Further, important practical issues which contribute in shear strengthening of structures with different element types especially RC beams with different strengthening techniques, such as steel plate and FRP laminate are discussed. Finally, direc- tions for future research based on the existing gaps of the existing works are presented.
strengthening of reinforcedconcretebeam-columnjoints with Fibre Reinforced Polymer Composites. Three exterior reinforcedconcretebeam-column joint specimens were tested under reverse cyclicloading. The joint region of these specimens suffered significant damage, whereas limited damage was observed in the beams. The damaged specimens were repaired and strengthened to prevent shear damage and strength deterioration inside the joint region and to achieve more ductile response. First, the damaged loose concrete was removed and replaced by high strength non shrink mortar. Then, fibre-reinforced polymer (FRP) strips were diagonally wrapped over the joint region, and longitudinal FRP strips were applied and anchored on the beams. Deformation capacities of the strengthened specimens were much larger than those of the original specimens. This goal was achieved by applying diagonal FRP strips in the joint region, and no damage was observed in the column or joint regions of the strengthened specimens.
Abstract: Beamcolumn joint subjected to seismic force will experience large shear forces, diagonal tension and high bond stresses in the reinforcement bars. Hence special attention need to be given for design and construction of beamcolumn joint subjected to seismic loading. Based on the location of joint, beam-column joint are classified as interior, exterior and corner joint. The study mainly focuses on experimental investigation on behaviour of Corner beam-columnjoints under seismic conditions. Corner beam-column joint of a multistorey reinforcedconcrete building (G + 4) in Salem Zone falling under the seismic Zone – III has been analyzed and designed using STAAD.pro. The specimens were designed for seismic load according to IS 1893 (Part-I): 2002 and detailed as per IS 13920 : 1993. The test specimen is reduced to one fifth model of beamcolumn joint from prototype specimen. Four specimens are investigated in which one is conventional specimen and other three are specimens with different reinforcement detailing. All the specimens were loaded up to failure under quasi - static cyclicloading, simulating earthquake actions. The beam - columnjoints are examined in terms of load carrying capacity, load-deflection behavior, stiffness degradation, energy absorption capacity, ductility factor and cracking characteristics. Performance of beamcolumn joint improves by suitably modifying the reinforcement details.
The behavior of RC beam-columnjoints strengthened with FRP was investigated. Five half- scale RC beam-column joint specimens strengthened with GFRP were tested and their performance was compared to that of the reference specimens that were tested in the earlier research (Li 2003). All the specimens were designed in compliance with BS 8110 (BSI, 1997) in which no transverse reinforcement was provided in the joint panel, to simulate those that might be prone to non-ductile joint shear failure under seismic action. Three types of loading routines were adopted in the study. The specimens were tested under reversed cyclic quasi- static loading, non-reversed cyclicloading and monotonic loading. Two Renewal schemes using externally bonded GFRP laminates aiming to improve the joint shear capacity and ductility performance were proposed.
Rehabilitation of structures to higher seismic zones of several cities and towns in the country has also necessitated in evolving new strategies. Recent earthquakes have demonstrated that most of the reinforcedconcrete structures were severely damaged during earthquakes and they need major repair works. One of the techniques of strengthening the RC structural members is through external confinement by high strength fibre composites which can significantly enhance the strength, ductility and will result in large energy absorption capacity of structural members. Fibre materials are used to strengthen a variety of reinforcedconcrete elements to enhance the flexural, shear and axial load carrying capacity of elements. Beam-columnjoints, being the lateral and vertical load resisting members in reinforcedconcrete structures are particularly vulnerable to failures during earthquakes and hence their rehabilitation is often the key to successful seismic rehabilitation strategy. FRPC based strengthening strategy could be an attractive option in order to restore joints. In addition to being lighter, thinner and easier to implement FRPC reinforcedjoints have the virtue of making the joints more ductile. This property is extremely desirable for seismic rehabilitation of structures. However, a direct extension of the strategies adopted for beams and columns are difficult as such the behavior of beam-column connections are complex and still not completely understood.
the longitudinal rebar yielding, +𝑉′ 𝑦 = 2.68 𝑘𝑖𝑝𝑠 and Δy′ = 0.9 inches. Based on these results, the yielding displacement and the drift ratio were calculated, Δy = 0.87 inches, φy = 0.0207, respectively. During the first cycle of this level, a popping sound was heard and small cracks were observed on the CFRP layer, ~ 6 inches from the column- stub intersection where there was an increase in the width of the flexural cracks, as shown
Hybrid fibre reinforcedconcrete is the one in which more than one or two types of fibers are used as secondary reinforcement. Fibres have been used to reinforce materials that are weaker in tension than in compression. However for any reinforcement to be effective, it must be stiffer than the concrete matrix that is reinforcing. Generally the less stiff fibres only offer benefits in improving the tensile strength of plastic and semi-hardened concrete and are therefore mainly used to reduce plastic shrinkage and plastic settlement cracking until now, most of the production of HFRC has been for non-structural applications, with the fibres added primarily for control of cracking due to plastic or drying shrinkage. The aim of this project is to determine the behaviour of the hybrid fibre reinforcedconcrete slabs under cyclicloading. The fibres used here are polyolefin and steel corrugated fibres. The percentage of fibres used here are 0.5%, 1%, 1.5% and 2%. So far the experimental works has been done under impact loading. The main aim of this project is to determine the flexural behaviour of hybrid fibre reinforcedconcretebeam under cyclicloading .the beam size adopted here is 1000mmx 150mmx170mm.
Weak structures whose capacity is insufficient, or for repairing damaged structures, has many advantages compared to conventional methods. The Canadian Armed Forces, with operations overseas in support of the United Nations, sees the potential of this technology as a fast and effective method of increasing the capacity of existing roadway bridges or buildings; Four point bending flexural test are conducted on four concrete control beams with externally bonded carbon fibre reinforced polymer sheets/ fabric. The effectiveness of externally bonded CFRP on the flexural strength of the concretebeam is studied
Test setup for RC column under eccentrically loading The test program consists of casting and testing of four columns, all having size of 2200X150X1550mm length and designed as slender column with two different reinforcement is 4number of 12mm diameter and 4number of 12mm diameter rod as longitudinal reinforcement. The column was casting using M50 grade concrete and Fe415 grade steel. OPC cement, Fine aggregates and the coarse aggregates of maximum size 20mm were used. High yield strength deformed (HYSD) bars of 12mm and 8 mm diameter were used as the longitudinal reinforcement. After 28 days curing specimen were tested in UTM to determining the compressive strength, split tension strength. The column was tested under biaxial bending with different eccentricity and details shown in Table-3 from Centre gravity of column. Test setup shown in
In our country many of the existing reinforcedconcrete structures are in need of repair or reconstruction, rehabilitation, because of deterioration due to various factors like corrosion, lack of detailing, failure of bonding between beam-columnjoints, increase in service loads, improper design and unexpected external lateral loads such as wind or seismic forces acting on a structure, environment and accident events etc., leading to cracking, spalling, loss of strength, deflection, etc. Strengthening of existing reinforcedconcrete structures is necessary to obtain an expected life span and achieve specific requirements. The need for efficient rehabilitation and strengthening techniques of existing concrete structures has resulted in research and development of composite strengthening systems. Recent experimental and analytical research have demonstrated that the use of composite materials for retrofitting existing structural components is more cost-effective and requires less effort and time than the traditional means. Fiber Reinforced Polymer (FRP) composite has been accepted in the construction industry as a capable substitute for repairing and strengthening of RCC structures. The superior properties of (FRP) polymer composite materials like high corrosion resistance, high strength, high stiffness, excellent fatigue performance and good resistance to chemical attack etc., has motivated the researchers and practicing engineers to use the polymer composites in the field of rehabilitation of structures. During past two decades, much research has been carried out on shear and flexural strengthening of reinforcedconcrete beams using different types of fiber reinforced polymers and adhesives. A detailed Literature review based on the previous experimental and analytical research on retrofitting of reinforcedconcrete beams is presented. Proposed method of strengthening the RC beam is decided based on the previous experimental and analytical research. Behaviors of retrofitted reinforcedconcrete beams wit h externally bonded CFRP with various types of resins (Epoxy, Orthophthalic Resin (GP), ISO resin) after initial load (60 % control beam) is investigated. Static load responses of all the beams under two point load method had evaluated in terms of flexural strength, crack observation, compositeness between CFRP fabric and concrete, and the associated failure modes. Keywords: Fiber Reinforced Polymer (FRP), CFRP fabric, reinforcedconcrete structures
The thermal properties for steel, including H-shaped steel and all the bars, were adopted according to the expressions provided by Lie and Denham (1993). Thermal properties of concrete are mainly affected by the mixture, type of aggregate and moisture content. Here, the carbonate aggregate concrete thermal model proposed by Lie and Denham (1993) were used in column, beam and slab. The effect of water on the thermal properties of concrete was taken into account using the method suggested by Lie (1994). This method assumes that all the water vaporizes at 100˚C, and the effect of water vaporization on the heat transfer is ignored, the influence of water on density and specific heat of concrete was considered by combining the properties of water into concrete, as shown below:
The experimental instruments were shown in Fig. 9. Each column was placed in an existing frame with a 200t hydraulic actuator. The column stubs were fastened to the rigid floor with four high-strength rods to prevent slip and overturning under large lateral loads. The actuator with a 200t load cell was mounted vertically onto the frame to apply the vertical axial load. Another two 30t horizontal hydraulic actuators with load cells were used to apply lateral reversal load. All instruments were connected to IMC data acquisition system for data selection. Before yield of the longitudinal bars, the horizontal load was applied in accordance to the load control mode, and the displacement control mode was adopted after yielding of longitudinal bar.