• Computers and Concrete
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• v.18 no.3
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• pp.297-317
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• 2016

Current codes recommend large amounts of shear reinforcement for reinforced concrete beam-column joints that causes significant bar congestion. Increase in congestion of shear reinforcement in joint core (connection zone), leads to increase accomplishment problems. The congestion may also lead to diameter limitations on the beam bars relative to the joint dimensions. Using double headed studs instead of conventional closed hoops in reinforced concrete beam-column joints reduces congestion and ensures easier assembly of the reinforcing cage. The purpose of this research is evaluating the efficiency of the proposed reinforcement. In this way, 10 groups of exterior beam-column joints are modeled. Each group includes 7 specimens by different reinforcing details in their joint core. All specimens are modeled by using of ABAQUS and analyzed subjected to cyclic loading. After verification of analytical modeling with an experimental specimen, 3D nonlinear specimens are modeled and analyzed. Then, the effect of amount and arrangement of headed studs on ductility, performance, ultimate strength and energy absorption has been studied. Based on the results, all joints reinforced with double headed studs represent better performance compared with the joints without shear transverse reinforcement in joints core. The behavior of the former is close to joints reinforced with closed hoops and cross ties according to the seismic design codes. By adjusting the arrangement of double-headed studs, the decrease in ductility, performance, ultimate moment resistant and energy absorption reduce to 2.61%, 0.90%, 0.90% and 1.66% respectively compared with the joints reinforced by closed hoops on the average. Since the use of headed studs reduces accomplishment problems, these amounts are negligible. Therefore, use of double-headed studs has proved to be a viable option for reinforcing exterior beam-column joints.

• Earthquakes and Structures
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• v.6 no.1
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• pp.89-110
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• 2014

Nonlinear dynamic analyses are carried out to investigate the influence of the pinching hysteretic response of the exterior RC beam-column joints on the seismic behavior of multistory RC frame structures. The effect of the pinching on the local and global mechanisms of an 8-storey bare frame and an 8-storey pilotis type frame structure is evaluated. Further, an experimental data bank extracted from literature is used to acquire experimental experience of the range of the real levels that have to be considered for the pinching effect on the hysteretic response of the joints. Thus, three different cases for the hysteretic response of the joints are considered: (a) joints with strength and stiffness degradation characteristics but without pinching effect, (b) joints with strength degradation, stiffness degradation and low pinching effect and (c) joints with strength degradation, stiffness degradation and high pinching effect. For the simulation of the beam-column joints a special-purpose rotational spring element that incorporates the examined hysteretic options developed by the authors and implemented in a well-known nonlinear dynamic analysis program is employed for the analysis of the structural systems. The results of this study indicate that the effect of pinching on the local and global responses of the examined cases is not really significant at early stages of the seismic loading and especially in the cases when strength degradation in the core of exterior joint has occurred. Nevertheless in the cases when strength degradation does not occur in the joints the pinching may increase the demands for ductility and become critical for the columns at the base floor of the frame structures. Finally, as it was expected the ability for energy absorption was reduced due to pinching effect.

• Journal of Industrial Technology
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• v.3
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• pp.103-116
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• 1983

Recent developments in multi-storey buildings for residential purpose have led to the extensive use of shear walls for the basic structural system. When the coupled shear wall system is used, joined together with cast-in-place concrete or mortar (or grout), the function of the continuous joints is a crucial factor in determining the safety of L.P. Precast concrete shear wall structures, because the function of the continuous joints(Vertical wall to wall joints) is to transfer froces from one element(shear wall panel) to another, and if sufficient strength and ductility is not developed in the continuous joints, the available strength in the adjoining elements may not be fully utilized. In this paper, the influence of the stiffness of vertical joints(wet vertical keyed shear joints) on the behaviour of precast shear walls is theoretically investigated. To define how the stiffness of the vertical joints affect the load carrying capacity of L.P.Precast concrete shear wall structure, the L.P.Precast concrete shear wall structure is analyzed, with the stiffness of the vertical joints varying from $K=0.07kg/mm^3$(50MN/m/m) to $K=1.43kg/mm^3$(1000MN/m/m), by using the continuous connection method. The results of the analysis shows that at the low values of the vertical stiffness, i.e. from $K=0.07kg/mm^3$(50MN/m/m) to $K=0.57kg/mm^3$(400MN/m/m), the resisting bending moment and shearing force of precast shear walls, the resisting shearing force of vertical joints and connecting beams are significantly affected. The detailed results of analysis are represented in the following figures and Tables.

• Earthquakes and Structures
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• v.18 no.1
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• pp.113-127
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• 2020

In this study, the behavior of external beam-column joints reinforced by plain and deformed bars with non-seismic reinforcement details is investigated and compared. The beam-column joints represented in this study include a benchmark specimen by seismic details in accordance with ACI 318M-11 requirements and four other deficient specimens. The main defects of the non-seismic beam-column joints included use of plain bar, absence of transverse steel hoops, and the anchorage condition of longitudinal reinforcements. The experimental results indicate that using of plain bars in non-seismic beam-column joints has significantly affected the failure modes. The main failure mode of the non-seismic beam-column joints reinforced by deformed bars was the accumulation of shear cracks in the joint region, while the failure mode of the non-seismic beam-column joints reinforced by plain bars was deep cracks at the joint face and intersection of beam and column and there was only miner diagonal shear cracking at the joint region. In the other way, use of plain bars for reinforcing concrete can cause the behavior of the substructure to be controlled by slip of the beam longitudinal bars. The experimental results show that the ductility of non-seismic beam-column joints reinforced by plain bars has not decreased compared to the beam-column joints reinforced by deformed bars due to lack of mechanical interlock between plain bars and concrete. Also it can be seen a little increase in ductility of substructure due to existence of hooks at the end of the development length of the bars.

• Journal of Welding and Joining
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• v.14 no.4
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• pp.99-108
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• 1996

The microstructure and bond strength are examined on the SiC/SiC and SiC/mild steel joints brazed by the Ag-Ti based alloys with different Ti contents. In the SiC/SiC brazed joints, the thickness of the reaction layers at the bond interface and the Ti particles in the brazing alloy matrices increase with Ti contents. When Ti is added up to 9 at% in the brazing alloy. $Ti_3SiC_2$ phase in addition to TiC and $Ti_5Si_3$ phase is newly created at the bond interface and TiAg phase is produced from peritectic reaction in the brazing alloy matrix. In the SiC/mild steel joints brazed with different Ti contents, the microstructure at the bond interface and in the brazing alloy matrix near SiC varies similarly to the case of SiC/SiC brazed joints. But, in the brazing alloy matrix near the mild steel, Fe-Ti intermetallic compounds are produced and increased with Ti contents. The bond strengths of the SiC/SiC and SiC/mild steel brazed joints are independent on Ti contents in the brazing alloy. There are no large differences of the bond strength between SiC/SiC and SiC/mild steel brazed joints. In the SiC/mild steel brazed joints, Fe dissolved from the mild steel does not affect on the bond strength of the joints. Thermal contraction of the mild steel has nearly no effects on the bond strength due to the wide brazing gap of specimens used in the four-point bend test. The brazed joints has the average bond strength of about 200 MPa independently on Ti contents, Fe dissolution and joint type. Fracture in four-point bend test initiates at the interface between SiC and TiC reaction layer and propagates through SiC bulk. The adhesive strength between SiC and TiC reaction layer seems to mainly control the bond strength of the brazed joints.

• Steel and Composite Structures
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• v.43 no.1
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• pp.19-30
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• 2022

The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft's skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, composite/composite and composite/metal) with riveted, adhesive bonded, and hybrid joining techniques are investigated with experiments and finite element analysis. The fatigue tests were tension-tension because of the typical nature of the loads on aircraft skin panels susceptible of experimenting fatigue. Experiment results suggest that the fatigue life of hybrid joints is superior to adhesive bonded joints, and these in turn much better than conventional riveted joints. Thanks to the fact that, for hybrid joints, the adhesive bond provides better load distribution and ensures load-carrying capacity in the event of premature adhesive failure while rivets induce compressive residual stresses in the joint. Results from FE tool ABAQUS analysis for adhesive bonded and hybrid joints agrees with the experiments. From the analysis, the energy release rate for adhesive bonded joints is higher than that of hybrid joints in both opening (mode I) and shear direction (mode II). Most joints show higher energy release rate in mode II. This indicates that the joints experience fatigue crack in the shear direction, which is responsible for crack opening.

• Journal of the Korean earth science society
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• v.37 no.6
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• pp.332-345
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• 2016

The columnar joints in Goheung are developed in three places of Yuju-san area, Palyeong-san and Yongbawi area. Vertical and fan-shaped columnar joints which have maximum width 100 m and maximum heigh 50 m are developed in the Yuju-san area Columnar joints are developed next to the road near the the Yuju-san and along the coast of Jijuk-do. Thick columnar joints of maximum width 1m are developed in the Paryeong-san area. Horizontal columnar joints of maximum width 50 cm at length of polygon side are developed on dyke in the Yongbawi area. The columnar joints show high rate of rectangles and pentagons in the number of polygons. The length of polygon side of columnar joints in study area ranges from 10 to 100 cm, and 20 cm among the range appears in high frequency. Columnar joints are developed vertically to the ground from the cooling surface in Yuju-san and Palyeong-san area. Columnar joints in Yongbawi area are developed vertically to the contact of country rocks. As a result, the columnar joints began cooling from the country rock contact. And columnar joints are developed vertically to contact surface. The rocks in columnar joints is rhyolitic welded tuff in Yuju-san and Palyeong-san area, dacite in Yongbawi area. In the acid volcanic rocks flow structure well developed. The white phenocryst mineral about 2 mm size by eye, is usually feldspar, and includes some quartz. The rate of $SiO_2$ is 70wt.% or more. It is the last stage of differentiation to calc-alkaline series. The columnar joints of the Yuju-san area are expected to be distributed along a band that extends to about 1km east of the stone pit.

• Structural Engineering and Mechanics
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• v.14 no.3
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• pp.307-330
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• 2002

This study aims at postulating a simple methodology for predicting the failure modes of monotonically loaded reinforced concrete beam-column joints. All the factors that affect the failure modes of joints are discussed in detail using an experimental database of monotonically loaded exterior beam-column joints. The relative contributions of the strut and truss mechanisms to joint shear strength are determined based on the test results. A simple design equation for the beam longitudinal reinforcement ratio for joints with low, medium and high amount of stirrups is developed. The factors influencing the failure modes of monotonically loaded exterior beam-column joints are investigated in detail. Design charts that predict the failure modes of exterior beam-column connections both with and without stirrups are developed. Experimental data are compared with the design charts. The results show that the simple methodology gives very accurate predictions of the failure modes.

• Tunnel and Underground Space
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• v.3 no.2
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• pp.142-151
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• 1993

In this study, the deformation characteristics of atrtificially fractured joints of granite under normal and shear loading were investigated. To obtain the characteristics of joint deformation, compression and shear tests were performed in the laboratory on three different sizes of rock specimens. The rock used in the experimens was Iksan granite. Joints were produced artificially by fracturing using the apparatus for generating extension-joint. Joint normal deformability was studied by conducting cyclic loading tests on the joints. Joint closure varied non-linearly with normal stress through cyclic loadings. As normal stress increased, the joints gradually reached a state of maximum joint closure. The relation between normal stress and joint closure for mated and unmated joints was well described by the hyperbolic and exponential function, respectively. Joint shear deformability was studied by performing direct shear tests under normal stresses on the joints. it was shown that the behaviour in the prepeak range was non-linear and joint shear stiffness depended on the size of specimen and the normal stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.471-478
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• 2002

In real structures, multi-spot welded joints are more frequently used than a single-spot welded joint. Most researches, however, have been focused to a single-spot welded joint until now. In this paper, the fatigue behavior of multi-spot welded joints are investigated using the finite element solutions of the multi-spot welded specimens. The local strain approach is used rather than the stress intensity factor approach to estimate the fatigue life since the former is quite simple and straightforward. It is found that the fatigue behavior of multi-spot welded joints is different from that of single-spot welded joints. The local strain approach is still applicable to multi-spot welded joints.