Beam Joints Research Articles

Anchorage performance of embedments in anchored prefabricated wall–beam joints of BLC–CCWS

The existing wall–beam joints of bundled lipped channel–concrete composite wall structures (BLC–CCWS) are mainly fabricated by welding thin–walled steel tubes and hot–rolled steel plates, and this application requires further improvement. An innovative anchored prefabricated wall–beam joint that does not require field welding was presented in this paper, and the anchorage performance of the embedment, which is the key force transfer component of the joint, was investigated by experimental research and theoretical analysis. The results indicated that (1) the embedments have good anchorage performance in the “bundled lipped channel–concrete” anchorage area, especially the “steel–stud–anchor plate” type of embedment, which clearly demonstrates a mechanical property evolution stage. (2) Embedment construction has a great influence on the anchorage performance. The ultimate bearing capacity, ultimate slip, ductility and energy storage/dissipation capacity of the “steel–stud–anchor plate” embedment are better than those of the “steel–stud” embedment. (3) The construction of the anchorage area has a great influence on the anchorage performance. The bundled lipped channel can substantially limit the range of damage to concrete. In addition, the anchorage performance of the embedment in the “bundled lipped channel–concrete” anchorage area is better than that of the “circumferential steel plate–concrete” anchorage area in terms of the ultimate bearing capacity, ultimate slip, ductility and energy dissipation capacity. (4) The established formula for calculating the anchorage bearing capacity of the embedment is accurate and conservative, and thus can meet the requirements of engineering practice.

Performance of concrete-encased CFST column-to-beam 3-D joints under seismic loading: Analysis

A numerical model of the concrete-encased concrete-filled steel tubular (CFST) column to steel beam joint was established to thoroughly discover the seismic performance of joints. The model was verified by experimental results in terms of failure patterns, hysteretic relationships and strain distributions. The stress and force distributions of different components were analyzed for joints under different loading phases, and comparisons were made between planar and 3-dimensional (3-D) joints. The parametric study was conducted to reveal effects of key parameters by verified numerical models. Furthermore, strength prediction models were proposed for both planar and 3-D joints, and the hysteretic model of panel zone for planar joint was established to describe the structural behaviour under cyclic loading.

Mathematical modeling of stress-strain state of the nodal joint of wooden beams

The article presents a study of the joint of wooden beams on a new type of aluminum composite connector. For the numerical experiment, beams with a cross-section of 150x220(h) mm made of solid wood were selected. The beams were connected at the same level in a perpendicular direction to each other. The connecting connectors were made of two types of alloys: 7075 T6 and 6061 T6. The experiment was carried out until the joint was completely destroyed under static load. The elastic operation of the node for different types of connectors under study was maintained until the load of 50… 70 kN, after which there was a sharp increase in the deformations of the beams. Conducting a numerical study of the elements of wooden structures made it possible to predict their behavior most accurately in real operating conditions.

Seismic Performances of SRC Special-Shaped Columns and RC Beam Joints Under Double-Direction Low-Cyclic Reversed Loading

Steel-reinforced concrete (SRC) special-shaped column and beam frame structure is a special structural form that can meet the requirements of high bearing capacity and satisfy the esthetic requirement of buildings. In this study, a new joint design approach is adopted to focus on the seismic behavior of SRC special-shaped column and reinforced concrete (RC) beam joints under low-cyclic double-directional reactions through pseudo-static tests with a controlled stirrup distance. The joints of SRC specimens were compared with those of RC specimens by controlling the area of steel and reinforcement, and hysteresis cycle skeleton curves and load and strain hysteresis cycles were analyzed. The specimen with profiled steel was found to have better energy dissipation capacity. The energy dissipation capacity and stiffness degradation of the nodes were analyzed. The test results showed that the energy dissipation capacity of the SRC joints was better than that of the conventional concrete column joints, and the stiffness degradation of RC joints was more significant than that of SRC joints.

Compression deformation and fracture behavior of additively manufactured Ti–6Al–4V cellular structures

Corresponding research was carried out to assess if the porous structures with modified diamond-shaped lattice cells can provide better integrity of the constructions in the case of overloading. The aim of the study is designing the structures with high porosity for the biomedical applications (implants) having good load bearing capacity. Studied lattice structures are based on the modified tetrahedral beam-based cells with spherical reinforcements at the beam joints and variable beam diameter. Samples with a porosity of 50–80% were studied in present research. Structures were additively manufactured from a titanium alloy Ti–6Al–4V using SLM. Sample compression tests were carried out according to the ISO 13314 standard. Loading experiments were carried out and critical parameters extracted from the stress-strain curves. Finite element modeling was carried out for the analysis of the stress and assessment of the potential failure mechanisms. Corresponding hypothesis explaining the appearance of shear bands in porous structures under compression is formulated. Obtained results show that when the sample porosity rises from 50% to 80%, corresponding plateau stress decreases by 13 times, first maximum compressive strength decreases by 12 times, and compression offset stress decreases by 12 times, while the plateau end does not change significantly. The experiments revealed the barrel distortion of the samples geometry, which corresponds to the general knowledge how the friction between the solid compressing surfaces (anvils of the compression testing machine) and the lattice affects the sample deformation. Compression experiments also revealed the formation of shear bands during sample deformation. The stochastic nature of their development suggests that the main reason of shear bands appearing is the initial inhomogeneity of the boundary conditions of the experiment.Suggested modifications of the basic cells show a good potential for achieving regular beam-based lattice structures with high porosity and increased load bearing capacity. More experiments are needed for statistical analysis, and improvements of the loading experiments methodology for better failure mode analysis are planned for the future.

Mapping Relation between Rail and Bridge Deformation Considering Nonlinear Contact of Interlayer.

This paper examines the effect of structural deformation on the unit slab-type ballastless track structure of high-speed railway. The principle of stationary potential energy was used to map the relation between girder vertical deformation and rail deformation considering the effect of subgrade boundary conditions and the nonlinear contact of interlayer. The theoretical model was verified by comparing with the finite element analysis and experimental results. The theoretical model was used to analyze the effects of several key parameters on the rail deformation, such as vertical deformation amplitude, elastic modulus of the mortar layer, and vertical stiffness of the fasteners. The results show that the track slabs suffered significant disengagement, which makes the deformation of the track structure at the position of the beam joint tend to be gentle when nonlinear contact between the mortar layer and the track slabs was considered. The track slabs disengagement mainly occurs near the beam joints (the side of the deformed beam). As the deflection amplitude of the girder increases, the track deformation, the fastener forces and the disengagement length of the track slabs are obviously nonlinear. When the vertical stiffness of the fastener and/or the elastic modulus of the mortar layer increase, the fastener force and the track plate disengagement length increase monotonically and nonlinearly, which will adversely affect the life and safety of the track structure.

Analysis on the value of stiffness of the dual joint straightness notch joint of beams due to cyclic lateral load

Precast concrete is an answer to the demands of building structures that save time, but cannot be used widely because of the reliability of the connection, especially during an earthquake, the desired earthquake-resistant building structure must have sufficient strength and rigidity. Stiffness is one of the factors that determine the response of a structure to earthquake loads. When connected with earthquake loads, a structure must have sufficient rigidity so that its movement during an earthquake can be limited. This study aims to determine and analyze the stiffness in the double columns straight joint beam notches due to lateral cyclic load. By dividing 3 (three) types of test specimens, namely Monolithic column Beam, Type 1 Column Joint (SBK), and Type 2 Column Beam Joint (SBK). The connection used is a double straight notch and using the grouting method. Testing and analysis using the Displacement Control Method with the European Convention for Constructional Steelwork (ECCS) 1986 standards. The results showed the monolith column Column (BK) specimens have a greater stiffness value compared to SBK 1 specimens and SBK 2 specimens.

Behavior of T-shaped CFST column and U-shaped steel-concrete composite beam joints

This paper intends to study the seismic and shear behavior of joints for T-shaped concrete-filled steel tubular (CFST) column and U-shaped steel-concrete composite beam (USCB). In the joint details, the C-shaped slots cut in the T-shaped steel tube allowed the double-C channels used to connect the thin-walled U-shaped steel (USS) passing through the panel zone directly. A total of six full-scale specimens constructed according to the concept of strong column-weak beam were tested: two specimens were tested under the monotonic loading to obtain the load-carrying capacity and the other four specimens under cyclic loading to evaluate the seismic performance . The variables included the details of USCB, the axial load level, and the beam-column linear stiffness ratio . Test results demonstrated that the proposed joint details exhibited good seismic and shear performance. Three typical failure modes, i.e. welding fracture between the double-C channels and the steel tube, local buckling of the steel tube, and fracture of the double-C channels were observed. Some indexes of seismic performances, such as load-carrying capacity, deformability , degradation of load-carrying capacity, stiffness degradation , and energy dissipation capacity were evaluated. Finally, the joint shear resistance of the specimens was discussed according to the ASCE design guidelines. • An innovative joint details for T-shaped concrete-filled steel tubular column and U-shaped steel-concrete composite beam was proposed. • Some indexes of seismic performances for the joints, such as load-carrying capacity, deformability, degradation of load-carrying capacity, stiffness degradation, and energy dissipation capacity were evaluated. • The joint shear capacity was evaluated according the methods given by the ASCE Task Committee and by the previous findings of the authors.

Joint Beam Training and Positioning for Intelligent Reflecting Surfaces Assisted Millimeter Wave Communications

Intelligent reflecting surface (IRS) offers a cost-effective solution to link blockage problem in mmWave communications, and the prerequisite of which is the accurate estimation of (1) the optimal beams for base station/access point (BS/AP) and mobile terminal (MT), (2) the optimal reflection patterns for IRSs, and (3) link blockage. In this paper, we carry out beam training designs for IRSs assisted mmWave communications to estimate the aforementioned parameters. To acquire the optimal beams and reflection patterns, we firstly perform random beamforming and maximum likelihood estimation to estimate angle of arrival (AoA) and angle of departure (AoD) of the line of sight (LoS) path between BS/AP (or IRSs) and MT. Then, with the estimated AoDs, we propose an iterative positioning algorithm that achieves centimeter-level positioning accuracy. The obtained location information is not only a fringe benefit but also enables us to cross verify and enhance the estimation of AoA and AoD, and it also facilitates the estimation of blockage indicator. Numerical results show the superiority of our proposed beam training scheme and verify the performance gain brought by location information.

Measurement and identification of the nonlinear dynamics of a jointed structure using full-field data; Part II - Nonlinear system identification

The dynamic responses of assembled structures are greatly affected by the mechanical joints, which are often the cause of nonlinear behavior. To better understand and, in the future, tailor the nonlinearities, accurate methods are needed to characterize the dynamic properties of jointed structures. In this paper, the nonlinear characteristics of a jointed beam is studied with the help of multiple identification methods, including the Hilbert Transform method, Peak Finding and Fitting method, Dynamic Mode Decomposition method, State-Space Spectral Submanifold, and Wavelet-Bounded Empirical Mode Decomposition method. The nonlinearities are identified by the responses that are measured via accelerometers in a series of experiments that consist of hammer testing, shaker ringdown testing, and response/force-control stepped sine testing. In addition to accelerometers, two high-speed cameras are used to capture the motion of the whole structure during the shaker ringdown testing. Digital Image Correlation (DIC) is then adopted to obtain the displacement responses and used to determine the mode shapes of the jointed beam. The accuracy of the DIC data is validated by the comparison between the identification results of acceleration and displacement signals. As enabled by full-field data, the energy-dependent characteristics of the structure are also presented. The setup of the different experiments is described in detail in Part I (Chen et al., 2021) of this research. The focus of this paper is to compare nonlinear system identification methods applied to different measurement techniques and to exploit the use of high spatial resolution data.

Mechanical behavior of T-shaped CFST column to steel beam joint

The seismic performance of T-shaped CFST column to H-shaped steel beam joint with vertical rib stiffeners was investigated experimentally and numerically in this study. Specifically, the joint shear deformation, inter-story drift ratio, joint stiffness, and energy dissipation capacity were analyzed. The test results demonstrate that the joint with vertical stiffeners has good seismic behavior and meets the requirements of Eurocode 3 for rigid joints in a braced frame. A finite element model for the multi-cell T-shaped CFST column to H-shaped steel beam joint with vertical rib stiffeners was established to investigate the influences of the following parameters on joint strength and joint stiffness: the width-to-thickness ratio of steel tube, vertical rib dimensions, and the axial load ratio of column. The numerical results indicate that the width-to-thickness ratio of steel tube and vertical rib dimensions play an important role in improving the joint strength and stiffness. A mechanical model for the joint strength was also developed, in which the contributions from the front face and side faces of steel tube and the vertical rib stiffeners were considered. To facilitate the practical design, a simplified design method for joint strength as well as the design suggestions for detailing are proposed based on the mechanical model.

EXPERIMENTAL STUDY ON THE MECHANICAL PROPERTY OF STEEL BAR-PIERCED JOINTS OF RC BEAMS AND RECTANGULAR CONCRETE-FILLED STEEL TUBULAR COLUMNS

To overcome the problems of RC beam-and-rectangular concrete-filled steel tubular column joints in high-rise buildings such as the indirect force transmission, complex construction and unguaranteed construction quality, a steel bar-pierced joint of RC beams and rectangular concrete-filled steel tubular columns was proposed for the Z13 project of the Beijing CBD core area. Low-cycle reciprocating loading tests were performed on the steel bar-pierced joints of RC beams and rectangular concrete-filled steel tubular columns with different reinforcement ratios to study the hysteretic performance, failure mode, energy dissipation capacity and ductility, which were compared with those of the conventional welded bracket joints and the joints of sleeves and brackets for RC beams and rectangular concrete-filled steel tubular columns. Based on the experimental results, the theoretical analysis of the mechanical properties of the steel bar-pierced joints of RC beams and rectangular concrete-filled steel tubular columns was conducted. Practical design formula were derived. It was indicated that the steel bar-pierced joint of RC beams and rectangular concrete-filled steel tubular columns had higher bearing capacity than the other two types of joints, which could meet the structural design requirements of “strong joints and weak components” and vertical load transmission. They are convenient to construct and reliable in quality. On this basis, the design formula for the bending bearing capacity of the joint is proposed. The section design of the steel corbel section is recommended to bear 80% of the beam end shear force to provide technical support for the optimization of the design of the rectangular concrete-filled steel tubular column-concrete beam through-reinforced joints.

Joint Real-Time Phase Shifter Network Calibration and Beam Tracking for mmWave Communication

The time-varying deviations of the phase shifter network (PSN) may cause significant performance degradation in the millimeter-wave (mmWave) multiuser communication system, especially when serving fast-moving users. In this letter, we propose an efficient joint real-time phase shifter network calibration and beam tracking (JRTPSNC-BT) algorithm. In each tracking period, the exploration strategy is determined according to the previously tracked beam directions. Then based on the latest observation and the historical observations, the time-varying channels and the time-varying PSN deviations are jointly tracked and updated. Simulation results show the superiority of our algorithm both in calibration error and spectral efficiency.

Macro‐modelling of 3D tubular column‐to‐truss beam joints

AbstractThe European Research Project “Innovative 3D joints for robust and economic hybrid tubular construction” aims at developing innovative plug‐and‐play joints for hybrid tubular construction where square (or rectangular) tubular columns are combined with truss‐beams composed of cold‐formed lightweight steel beams. This kind of joints provides a highly efficient structural system for modular solutions that are essential for fast‐track construction. An important task of this project is to develop a 3D joint model that takes into account 3D behavior of joints. The 1D component method presented in the Eurocode 3 part 1‐8 is extended to a 3D level by considering all relevant components and interactions between them.In the literature, some studies showed that the out‐of‐plane deformation of the tubular column faces depends on the loading and boundary conditions of the other faces. The first objective of this article is thus to propose a new 2D springs model taking into account the correlation between out‐of‐plane deformations of the faces of rectangular hollow section (RHS) columns. Then, a formulation of a 3D macro‐element of the joint is presented. Finally, the model is validated using two distinct procedures: 1) an analytical procedure implemented in a symbolic calculation software; 2) a modelling by finite elements.

Joint precoding schemes for flexible resource allocation in high throughput satellite systems based on beam hopping

Beam hopping technology provides a foundation for the flexible allocation and efficient utilization of satellite resources, which is considered as a key technology for the next generation of high throughput satellite systems. To alleviate the contradiction between resource utilization and co-frequency interference in beam hopping technology, this paper firstly studies dynamic clustering to balance traffic between clusters and proposes cluster hopping pool optimization method to avoid inter-cluster interference. Then based on the optimization results, a novel joint beam hopping and precoding algorithm is provided to combine resource allocation and intra-cluster interference suppression, which can make efficient utilization of system resources and achieve reliable and near-optimal transmission capacity. The simulation results show that, compared with traditional methods, the proposed algorithms can dynamically adjust to balance demand traffic between clusters and meet the service requirements of each beam, also eliminate the co-channel interference to improve the performance of satellite network.

Calculation Model of Shear Capacity of Multiple Composite Core Column Joints Based on Softened Tension-Compression Bar Model

This paper aims to study the seismic performance of multiple composite core column joints. The influence of the stress mechanism, axial compression ratio, and shear span ratio on the failure mode, hysteretic performance, and shear capacity of the multiple composite core column joints was studied through the low-reversed cyclic loading tests of three specially designed and manufactured multiple composite core column joints. The angle ratio method is used to calculate the effective area of the vertical tie bar, and based on the mechanism of the softening tension-compression bar, the formula for calculating the shear capacity of the joint with multiple composite core column is established. In addition, it is also verified by the test data in this paper. The experimental results show that when the axial compression ratio increases from 0.26 to 0.45, the number and width of cracks at the beam end decrease. When the shear span ratio increases from 1.67 to 2.22, the number and width of cracks at the joint beam end increase. The average value and standard deviation of the ratio between the measured value and the calculated value of the shear capacity are 0.97 and 0.16, indicating that the proposed calculation method has a high agreement with the actual value and strong engineering application.

Tensile and shear behavior of box connector for precast concrete shear walls

As precast concrete (PC) shear walls have been widely used in housing industrialization, reliable connections are important to ensure structural integrity of prefabricated shear walls. In the present study, a pair of innovative steel sleeve and box connections were proposed for rapid installation of fully assembled PC shear walls. Pull-out tests were performed on six PC specimens with sleeve and box connectors. Further, monotonic and cyclic lateral loading tests were performed on eight PC wall-ground beam joints. The test parameters were the configuration of connectors in the pull-out tests, and screw bolt strength, axial compression ratio (ACR), and loading type in the lateral loading tests. The test results showed that early pull-out failure occurred in the embedded sleeve due to flexural deformation of the horizontal pin rod, while fracture of the screw bolt occurred in the box component. Shear strength of the wall joint was developed by adhesive/interlock action, dowel action, and shear friction action. As screw bolt strength and ACR increased, the shear strength increased. To investigate the characteristic failure behavior of the connector and wall joint specimens, nonlinear finite element analysis (FEA) was conducted using ABAQUS program. A parametric study was performed to investigate the effect of design parameters on the pull-out and shear strength of the wall joint. Further, the test results were compared with the current design code requirements. Finally, an improved connection was suggested to increase the structural performance of the wall joint.

Experimental and Numerical Investigations of PVC-FRP Confined Concrete Column-RC Beam Joint Reinforced with Core Steel Tube under Axial Load

The axial compressive behaviors of the PVC-FRP Confined Concrete (PFCC) column-Reinforced Concrete (RC) Beam Joint reinforced with Core Steel Tube (CST) are investigated thoroughly using experimental and numerical methods in this study. The test programme is carried out on nine PFCC column-RC beam joints reinforced with CST (PCRBJ-CST). To systematically investigate the PFCC column-RC beam joints and reasonably design this structural connection components, all specimens are designed by principle of “strong column-weak joint”. Different variable parameters including the stirrup ratio of joint core, joint height, length of CST and reinforcement ratio of CST are considered. The test results demonstrate that, as the design expected, all the specimens fail by crushing of the concrete of joints, while the PFCC columns aren't damaged. Test results indicate that the stirrup ratio of joint core, joint height and reinforcement ratio of CST have significant impacts on carrying capacity, deformation and stiffness. Subsequently, a verified finite element (FE) model for the PCRBJ-CST under axial load is developed. Additionally, the applicability of existing codes to predict carrying capacity of PCRBJ-CST is evaluated based on experimental data.

Modeling of dowel action for cast-in and post-installed anchors considering bond property

In reinforced concrete structures, cast-in anchors are applied to beam–column or slab–beam joints. Furthermore, in seismically strengthened structures, post-installed anchors are used to connect new members to existing members. These anchors are subjected to shear and tensile stresses during an earthquake. However, a mechanical model that can estimate the behavior of these anchors when subjected to combined stress has not yet been proposed. Therefore, in this study, various anchors were tested under combined stress conditions. The test parameters were the type of anchorage method, shape of anchor bolt, anchorage length, hole diameter of the drilling, type of adhesive, and tensile stress ratio. It was observed that the shear force of the post-installed anchors was larger than that of the cast-in anchors. Moreover, as the diameter of the hole increased, the shear force also increased. Subsequently, the mechanical model, which was proposed for a post-installed anchor in a previous study, was modified for application to various anchors. By considering the diameter of the hole in the bearing resistance and introducing the bond strength to catenary action, the test results of the various anchors could be reasonably estimated.

Numerical Study on Performance of Prefabricated RCS Joint under Normal Temperature and Fire

To study the mechanical behavior and fire resistance of the prefabricated reinforced concrete column and steel beam (RCS) joints with endplate, this paper presented a numerical investigation on the joints under normal temperature and fire. The full 3D solid finite element models were implemented in ABAQUS. The simulated results show that under normal temperature, the yield moment and initial rotation stiffness increase with the increase of the endplate thickness, the failure mode changes from deformation of the endplate to yield of the extensional part. Increasing the thickness of stiffeners and changing the form of stiffeners can effectively improve the yield moment of the joint, but the initial rotational stiffness keeps invariant basically. Under fire condition, the load ratio has a significant effect on the fire resistance of the prefabricated RCS joint; the thickness of the endplate and stiffener, the stiffener form have less influence on the fire resistance of the joint.