•Six half-scale 3D RC beam-column joint specimens were retrofitted with FRP sheets.•X-shaped FRP sheets were used with the EBROG technique.•The proposed strengthening pattern prevented the joint ...shear failure.•The plastic hinge was relocated away from the column interface into the beam.
Beam-column joints are fundamental structural components of a stable structure. Corner joints are more likely to fail due to their small size and inferior confinement. This calls for three-dimensional (3D) strengthening of corner joints with fiber reinforced polymer (FRP) sheets to improve the load carrying capacity and ductility of beam–column connections. The present study investigates the shear strength of non-seismic 3D corner joints lacking adequate transverse reinforcement in their joint panel but strengthened with carbon fiber reinforced polymer (CFRP) sheets. The externally bonded reinforcement on groove (EBROG) technique is used in the joints to delay the debonding of CFRP sheets off the concrete substrate. Maximum expected moment resistance of a beam/connection is typically obtained at the column interface. This, therefore, requires sufficient bonding strength provisioned between the FRP sheet and the concrete substrate over an acceptable range of the bonding length. Practical limitations, however, do not allow for enough length of the column interface to be strengthened. A new anchorage system of FRP fans is, therefore, provisioned to attain the required bonding strength. The results are verified by studying the hysteretic response of the 3D corner joints strengthened via the proposed EBROG method and with the provisioned FRP fans. For this purpose, six half-scale 3D joint specimens were constructed and subjected to relevant tests. The specimens included a control, one reference specimen that satisfied the current building codes, and four FRP-retrofitted specimens with X-shaped strengthening patterns. The results revealed that the proposed strengthening pattern prevented joint shear failure. Furthermore, the proposed EBROG technique outperformed the externally bonded reinforcement (EBR) techniques as evidenced by the higher values of maximum load-carrying capacity and ductility recorded by the joint while CFRP debonding off the concrete substrate was also delayed. Maximum loading led to a drift ratio of 4.5%, indicating that application of the EBROG technique combined with FRP fans inhibited load reductions throughout the test period.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study aimed to design and evaluate the detachable corner joints used in wooden furniture frames, including a commonly used detachable joint (control) form using mortise and tenon with plug ...reinforcement and three novel proposed joints, i.e., novel joint I ~ III, which adopted in-line double-hole nuts, metal sheet connector, and embedded nuts and screws respectively, via numerical and experimental methods. The numerical analysis results indicated that the optimal proposed joint (novel joint І) had good mechanical performance when subjected to bending load with proper stress distributions and relatively low maximum stress compared with the other two proposed joints. The experimental results showed that the bending load resistance of the control and the optimal proposed joints were 1920 N (0.14) and 4390 N (0.05), respectively. The bending moment capacity and bending stiffness of the optimal joints were remarkably higher than the bending moment capacity and bending stiffness of the control joint. In addition, the combination of the numerical and experimental methods could effectively simplify the steps of furniture connection design and development and save costs in terms of time and materials.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study investigates frame corner joints built of birch plywood plates and glulam elements connected via self-tapping screws. Analytical calculations based on the fastener group’s torsional moment ...resistance, the proposed fastener group’s elastic and post-elastic load-bearing criteria, and the design formulas in Eurocode 5 were performed to predict the connection capacity in both elastic and post-elastic stages. A combined action check formula was adopted to predict the capacity of birch plywood plates and glulam elements. Frame corner specimens constructed with three different plywood thicknesses were planned to study the influence on global behavior and rotational stiffness. The specimens were intentionally designed so that failure occurred either in plywood or in glulam, in order to examine the robustness and validity of analytical calculation models. Another supplementary test group with 21 mm plywood and fewer fasteners was also designed and tested, in which the plastic yield of fasteners was expected. The test results of this supplementary group served to calibrate the analytical model that predicts the elastic and post-elastic capacity of the connection group. As a result of the comparison, the analytical calculations gave reasonable predictions on the failure of plywood, glulam, and the capacity of the fastener group. Only when the exposed moment exceeded the post-elastic limit of the fastener group did the plastic yielding of fasteners become observable. Moreover, numerical finite element models adopting the foundation zone-modeling scheme were constructed, which were proven to capture all test configurations' linear loading stiffness satisfactorily.
•Frame corner joints consisting of birch plywood, glulam elements, and self-tapping screws were constructed and tested.•Analytical models based on combined load action checks were able to predict the failure capacity of timber elements.•Analytical models based on polar moment of inertia well-predicted fastener groups' elastic and post-elastic capacities.•Global mechanical behavior and rotational stiffnesses were measured and compared among different test configurations.•The numerical model well-predicted the stiffnesses of frames with 21 mm plywood and underestimated that with thin plywood.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Cyclic behavior of RC OMF corner joints was investigated under bidirectional loading.•Noticeable difference between ASCE 41-17 force-deformation curves and measured curves was observed.•Minimal ...amount of transverse reinforcement in OMF corner joints played an important role in joint cyclic behavior.
Reinforced concrete (RC) ordinary moment frames (OMFs) are commonly used for building construction in low-to-moderate seismic regions. Unlike those in special moment frames (SMFs), beam-column joints in RC OMFs are susceptible to damage during earthquakes because the joints are not designed to resist the large shear forces transferred from adjoined members in the elastic range. For this reason, they are more vulnerable when subjected to bidirectional seismic loading. Beam-corner column joints (corner joints) especially are exposed to bidirectional seismic loading. The aim of this study was to explore the cyclic behavior of RC OMF corner joints. Three full-scale corner joint specimens with slabs were built and tested under unidirectional and bidirectional loadings. It was observed that minimal joint transverse reinforcement placed in the OMF joints played an important role on the cyclic performance of the joints, particularly under bidirectional loading. Noticeable difference existed between measured and ASCE 41-17 force-deformation curves, particularly in bidirectionally loaded specimens and in the specimen without joint transverse reinforcement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The shear resistance of 3D printed periodic auxetic chiral mechanical metamaterial was quantified via a picture-frame apparatus. The experimental set-up allowed the accurate measurement of the ...effective shear modulus of the material. Also, a rigid-rod-rotational spring model shows that the effective shear modulus of the material is directly related to the chiral geometry and the rotational rigidity of the center joints and the corner joints in the chiral cell. To facilitate practical design, design guidelines were developed through an integrated analytical, numerical and experimental approach. The influences of the chiral geometry and the joint rigidity on the shear resistance of the periodic auxetic chiral mechanical metamaterial were quantified. The design guidelines were verified by systematic finite element (FE) simulations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Five beam-column joints were tested to investigate the seismic behaviour of beam-column joints.•The D/t ratio had a dominant impact on the yield and plastic moment.•The stress on the annular ...stiffener showed a double hump shape.
In this study, two two-dimensional (2D) and three three-dimensional (3D) beam-column joints are tested under pseudo-static loadings to investigate the influence of loading types on the seismic behaviour of beam-column joints, especially for the hysteretic behaviour and failure modes. The main experimental parameters are the loading types (uniaxial loading, biaxial symmetrical loading (BS loading), and biaxial centre symmetrical loading (BCS loading)) and the width-to-thickness ratio of the steel column (D/t = 22 and 33). In a 3D joint, BS loading comprised of two equal forces applied at the two beam ends in the same direction while BCS loading comprised of two equal forces applied at the two beam ends in the opposite directions. The results indicate that the loading types affect the bearing capacities of the specimens. The bending moment of the specimens under BCS loading are 20% lower compared to specimens under unidirectional loading, while the bending moment of the specimens under BS loading are similar to those under unidirectional loading. Width-to-thickness ratio of the square steel column is one of the key factors that affect the bending moment of the specimens. According to the test results, FEM models of test specimens are established by using ABAQUS. The numerical results are in good agreement with the experimental results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
For extending the application of hybrid welding to the fabrication of steel bridge structures, a series of experiments were performed. One-pass full-penetration corner joints of SBHS500 with 12 mm ...thickness were fabricated by laser-arc hybrid welding. Four passes were required to produce the same-dimensional full-penetration corner joints by conventional arc welding. Monotonic compressive loading experiments were performed to investigate the load-carrying performances of hybrid-welded and arc-welded corner joints. Compared to arc-welded specimens, the elastic stiffness of hybrid-welded specimens was greater by 24%, and the maximum compressive load of hybrid-welded specimens was greater by 5%, demonstrating that the load-carrying performances of hybrid-welded corner joints may outperform arc-welded corner joints.
•Experimental stand for testing of carpentry corner joints is designed and presented.•Experiments on two types of joints, dovetail and saddle-notch are performed.•Numerical models of the joints are ...defined and the experiments are simulated.•The numerical models are validated on the base of the experiments.•Mechanics of both types of joints is shown and some advice on the modelling is given.
This work concerns experimental and numerical research on carpentry joints used in historic wooden buildings in southeastern Poland and western Ukraine. These structures are mainly sacred buildings, and the types of corner log joints characteristic of this region are primarily saddle-notch and dovetail joints; thus, these two types of joints were analysed in this study.
The modelling of historic timber structures is a complex issue, so the following steps are necessary to obtain accurate solutions: verification, validation and uncertainty quantification. The first and third steps were performed in a previous study, so the current research aimed to validate the numerical models and perform simulations of carpentry joints. Herein, the authors created finite element models of two types of joints and subsequently analysed the mechanical behaviour of these joints.
Due to issues concerning model validation, the authors designed a testing stand for corner joints, which formed a part of a biaxial testing machine. The joints were subjected to horizontal loads (deformations), which may cause damage to the connection. Thus, special parts were designed for the stand, which made it possible to fix the joint and prevented eccentric forces that could possibly damage the machine during testing.
The authors presented the differences and similarities in the behaviour of both types of joints, emphasizing the corresponding advantages and disadvantages. In addition, the authors determined which type of joint was the most susceptible to damage and what elements failed first.
This paper also showed the complexity of modelling timber structures and the accuracy of the proposed numerical models for both types of joints through comparisons of the numerical and experimental results. This work primary addressed the problems in accurately reflecting material, load and boundary conditions in numerical modelling of tested carpentry corner log joints.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
AbstractThe vulnerability of conventional RC structures to structural failure caused by the loss of corner columns has been emphasized over the past years. However, the lack of experimental tests has ...led to a gap in the knowledge for the design of RC building structures to mitigate the likelihood of progressive collapse caused by losing a ground corner column. Seven one-third scale RC beam-column substructures were tested to investigate their performance. The variables selected for the test specimens included beam transverse reinforcement ratios, type of design detailing (nonseismic or seismic), and beam span aspect ratios. Shear failure was observed to have occurred in the corner joint, and a plastic hinge was formed at the beam end near the fixed support in the nonseismic detailed specimens. However, plastic hinges were also formed in the beam end near to the corner joint for the seismically detailed specimen. Vierendeel action was identified as the major load redistribution mechanism before severe failure occurred in the corner joint, but a cantilever beam redistribution mechanism dominated after the corner joint suffered severe damage. The test results were compared with the Department of Defense design guidelines to highlight the deficiencies of the recently updated guidelines.
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DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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