Plastic Beam Research Articles

Seismic performance of spatial beam-column connections in steel frame

This paper presents a developed spatial beam-column connection in steel frame which is suitable for widely used H-section column and beam. To provide a first insight into the hysteretic responses of the proposed spatial connections, a numerical comparative analysis was conducted for the proposed connections and also the traditional connections after verifying the validity of the finite element methods. The normalized moment versus the story drift rotation hysteretic loops, energy dissipation capacity, failure modes, Mises index (MI), triaxiality index (TI) and rupture index (RI) distribution at the beam flange welds were discussed in detail. The proposed connection could significantly improve the hysteretic performance of the strong–axis connections and also the weak-axis connections in terms of the stiffness, strength, energy dissipation capacity, and could effectively move the beam plastic hinges away from the beam-column interface. The proposed spatial connection has the characteristics of “strong connection and weak member”. The spatial loading exerted negligible effects on the structural behavior of the beam-column connections for the considered sizes and loading methods. It is recommended that the anti-lamellar tearing steel plate could be used for the side plates in the proposed connections to prevent the tearing fracture.

Effects of aluminum honeycomb filler on crashworthiness of CFRP thin-walled beams under dynamic impact

Filling structures with aluminium honeycomb is a typical method for increasing the energy absorption (EA) characteristics of thin-walled beams. This paper puts forward the new outstanding energy absorption component of aluminium honeycomb-filled Carbon Fiber Reinforced Plastic (CFRP) thin-walled beams which has good cost-effectiveness and easy availability. The effects of aluminium honeycomb filler on the crashworthiness of CFRP thin-walled beams are discussed. Dynamic impact tests of the bending and compression of aluminium honeycomb-filled beams with different configurations are carried out, and the deformation modes and force responses are investigated. Numerical simulations of the tests are also performed, and the accuracy is validated by the experimental results. The influences of such factors as aluminium honeycomb cell size and aluminium honeycomb filling on bending and compression resistance are analyzed. The results show that aluminium honeycomb filler considerably improve the performance of CFRP thin-walled beams.

Effect of different RC slab widths on the behavior of reinforced concrete column and steel beam-slab subassemblies

In this paper, a total of three reinforced concrete column-steel beam (RCS) subassemblies with different RC slab widths following the strong column-weak beam criterion were tested under the reversed cyclic to investigate the influence of the RC slab on the load transfer mechanism and failure feature of composite connections. With appropriate joint detail, the tested specimens fully developed a desirable beam plastic hinge mechanism with stable and ductile hysteretic response. It was found that the effect of the composite beam-slab sections constrained the core concrete in the connection region was able to obviously improve the seismic performance of composite connections. Additionally, results from this research presented that the RC slabs made a limited contribution to the strength and stiffness of the connections beyond a certain limiting value for the RCS composite moment resisting frame. By analyzing the mechanic mechanism of reinforced concrete column and steel beam-slab connection, it was indicated that effective flange width of the composite beam-slab sections has a significant effect on the capacity of beam moment and equivalent elastic moment of inertia values. Based on the test results, some suggestions are presented for the design of the RCS frame systems, which demonstrates a viable alternative structures in high seismic risk zones.

Multiparameter seismic behavior of castellated beam-to-column connections based on stress migration

This paper presents a study on the castellated beam-to-column connections with four regular hexagonal web openings and one solid web beam-to-column connection that considering the opening rate and whether there is a combination of floor slabs (composite action) while subjected to the cyclic loading. Furthermore, the initial geometric imperfection was carefully incorporated in the FE model and the models have been validated against published experimental results. There is a slightly different about 5% between FE and test results including ultimate bearing capacity and other hysteresis behaviors. Investigation of 38 FE models subjected to cyclic loading focuses in the variation regularity of the failure mode, plastic development, stress migration, and seismic behaviors under the coupling effect of various factors, including the composite action of the floor slab, opening rate, the distance from the first opening to the face of the column, depth-to-thickness ratio of the web, and opening spacing. It is found that the composite action can improve the stress distribution around the first opening and raise the bearing capacity and ductility of the connections to a certain extent. Further, when the opening rate is either smaller than 0.5 or higher than 0.7, the plastic hinge of the connections with the floor slab occurs at the beam-to-column connection weld, which is completely different from the failure mode that without composite action. When the distance from the first opening to the face of the column is equal to or greater than 1.375 times the depth of beam, the plastic hinge formed in the beam-to-column weld while the composite action is taken into account; when disregarding the composite action causes the plastic hinge emerged in the beam section. Also, the ultimate bearing capacity of the castellated beam-to-column connections with closely spaced web openings significantly decreases; however, widely spaced web openings make stress concentration around the first opening and hinder the migration of stress to other openings, which has an adverse effect on the ultimate bearing capacity and ductility of the connections. The depth-to-thickness ratio of the web is also an important factor affecting the damage mode either web buckling or beam plastic hinge.

Contactless Detection of Natural Bending Frequencies using Embedded Metallic-Glass Ribbons inside Plastic Beams made of 3-D Printing

In the current work, to identify the bending mode harmonics, 30 microns thin magnetoelastic ribbons made of metallic glass are embedded inside 6 mm thick PLA plastic cantilever beams made by 3-D printing. This is possible because the ribbons are of magnetoelastic nature and thus change their mechanical state inducing a corresponding change in their magnetic state. The ribbons are placed at four different depths, starting with zero depth at the beam’s external surface all the way inside to the beam’s mid-plane. This technique is capable of detecting seven harmonics, and remarkably, these frequencies remain the same within a marginal error of 1% for all the depths. The amplitude of the modes drops with the increase in depth but is still strong enough, except at the midplane, to be used as a sensing signal. The harmonics spectrum is the unique signature of the structure’s state; this is a proof of concept that in a contactless fashion, the embedded ribbons provide useful information about the mechanical health of a structure.

The Prediction of Stiffness Reduction Non-Linear Phase in Bamboo Reinforced Concrete Beam Using the Finite Element Method (FEM) and Artificial Neural Networks (ANNs)

This paper discusses the reduction of the stiffness of bamboo reinforced concrete (BRC) beams to support the use of bamboo as an environmentally friendly building material. Calculation of cross-section stiffness in numerical analysis is very important, especially in the non-linear phase. After the initial crack occurs, the stiffness of the cross-section will decrease with increasing load and crack propagation. The calculation of the stiffness in the cross-section of the concrete beam in the non-linear phase is usually approximated by giving a reduction in stiffness. ACI 318-14 provides an alternative, reducing the stiffness of the plastic post-linear beam section through the moment of inertia (I) of the beam section for elastic analysis between 0.50Ig–0.25Ig. This study aims to predict the value of the reduction in the stiffness of the BRC beam section in the non-linear phase through the load-displacement relationship of experimental results validated by the Finite Element Method (FEM) and the Artificial Neural Networks (ANN) method. The experiment used 8 BRC beams and one steel-reinforced concrete (SRC) beam of singly reinforced with a size of 75 mm × 150 mm × 1100 mm. The beams were tested using a four-point loading method. The analysis results showed that the value of the stiffness reduction in the beam cross-sectional in the non-linear phase ranged from 0.5Ig–0.05Ig for BRC beams, and 0.75Ig–0.40Ig for SRC beams.

A numerical investigation on the through rib stiffener beam to concrete-filled steel tube column connections subjected to cyclic loading

This research presents a numerical investigation on the behaviour of through rib stiffener steel beam connected to circular concrete-filled steel tube (CFT) column subjected to the cyclic loading. A nonlinear Finite Element (FE) model was established using ABAQUS/Standard program. The accuracy of the FE result was examined through comparing it with the previous experimental test results. The effects of various parameters on the failure mode and ultimate moment capacity of the connections were investigated on twenty-four FE models. The parameters were stiffener’ height, length, and thickness including varied thicknesses and diameters of the hollow circular steel tube. The FE results indicated that the larger height of the through rib stiffener improved buckling behaviour of the steel tube column and the moment capacity by 8%. Meanwhile, the longer and thicker through rib stiffener effectively shifted the beam plastic hinge’s location away from the column, which resulted in 4% improvement in ultimate moment capacity of the connection.

Sensitivity Analysis of Tubular-Web Reduced Beam Section Connections Under Cyclic Loading

Recently a new type of Reduced Beam Section (RBS) connection called “Tubular Web RBS (TW-RBS)” has been numerically and experimentally studied. TW-RBS connections are made by replacing a part of web with a tube or pipe at the desirable location of the beam plastic hinge. This paper aims to numerically investigate the effect of key factors such as position, diameter, and thickness of the tube on the hysteretic behavior of the connection under cyclic load using ABAQUS finite element software. First, a model is used for verification purposes where good correlation with experimental results was achieved. Then, 14 models are defined by varying the key parameters and subjected to cyclic loading. The effects of such factors on the behavior of the connection are investigated in order to find out consequences of probable defects during the implementation of TW-RBS connections or intentional utilizing of other pipes in TW-RBSs. Based on the results, the position of the tube is the most sensitive factor in the behavior of TW-RBS connections and its improper location leads to unreliable design, probable plastic hinge formations in unpredicted regions, and possible failure in the connection zone. On the contrary, diameter and thickness of the tube have negligible effect on the energy dissipation mainly depending on beam section properties.

Experimental research on seismic performance of precast cogging high-strength bolt composite joint and influence of its arrangement location

The connection of precast joints is an important factor that affects the seismic and endurance performance of precast concrete structures. Currently, the seismic performance of existing precast joints cannot satisfy the application requirements of complex and harsh environments. This paper proposes a cogging high-strength bolt composite joint (C-HSB joint), and introduces its main components and assembly methods. Two precast beam-column joint (B-C joint) specimens are designed and manufactured using C-HSB joints. The C-HSB joints are arranged outside (SJ2) and inside (SJ3) the plastic hinge area of the beam. For comparison, a B-C joint specimen using a traditional cogging joint (T-C joint) is also designed and manufactured. The T-C joint is arranged outside of the plastic hinge area of the beam (SJ1). Then, quasi-static tests of these three specimens are performed. The seismic performance of the C-HSB and T-C joints are systematically analysed through the following parameters: damage phenomenon, bearing capacity, displacement ductility, rigidity deterioration, energy dissipation, operating state of the cogging seam, and bond-anchorage performance of rebar. Moreover, the influence of the arrangement location and HSB settlement of the C-HSB joint is discussed in detail. The results show that cogging can limit the development of seam cracks and improve the shear capacity of the joint. The HSB can delay the seam cracking, improve the bond-anchorage performance of rebar, and increase the crack resistance and self-resetting capacity of joints. The C-HSB joint can delay the development of seam cracks. The longitudinal rebar of the specimen can utilise more effectively using a C-HSB joint. The location of the C-HSB joint significantly affects the failure mode of the specimen. The internal arrangement (inside the plastic hinge area) of the C-HSB joint will induce the upward motion of the beam plastic hinge and exacerbate the core area damage. The external arrangement (outside the plastic hinge area) will increase the bearing capacity and energy dissipation of the specimens, and the rigidity deterioration will also be slowed. Compared with the C-HSB joint, the T-C joint has a lower displacement ductility, lower energy dissipation, and more rapid rigidity deterioration. The seismic performance of the T-C joint is significantly inferior. The C-HSB joint can be applied to precast concrete structures under complex and harsh environments. The external arrangement (close to the upper boundary of the plastic hinge area) of the C-HSB joint is a better choice.

Comparison of monotonic and cyclic pushover analyses for the near-collapse point on a mid-rise reinforced concrete framed building

The near-collapse performance limit is defined as the deformation at the 20% drop of maximum base shear in the decreasing region of the pushover curve for ductile framed buildings. Although monotonic pushover analysis is preferred due to the simple application procedure, this analysis gives rise to overestimated results by neglecting the cumulative damage effects. In the present study, the acceptabilities of monotonic and cyclic pushover analysis results for the near-collapse performance limit state are determined by comparing with Incremental Dynamic Analysis (IDA) results for a 5-story Reinforced Concrete framed building. IDA is performed to obtain the collapse point, and the near-collapse drift ratios for monotonic and cyclic pushover analysis methods are obtained separately. These two alternative drift ratios are compared with the collapse drift ratio. The correlations of the maximum tensile and compression strain at the base columns and beam plastic rotations with interstory drift ratios are acquired using the nonlinear time history analysis results by the simple linear regression analyses. It is seen that these parameters are highly correlated with the interstory drift ratios, and the results reveal that the near-collapse point acquired by monotonic pushover analysis causes unacceptably high tensile and compression strains at the base columns, as well as large plastic rotations at the beams. However, it is shown that the results of cyclic pushover analysis are acceptable for the near-collapse performance limit state.

Discrete element method using cohesive plastic beam for modeling elasto-plastic deformation of ductile materials

This paper introduces a three-dimensional (3D) simulation to model the elasto-plastic deformation of ductile materials by discrete element method (DEM) using cohesive plastic beam approach. The Euler–Bernoulli beam theory is applied to calculate force and torque reactions of the cohesive beam bond that can account for plastic strain. In order to simulate the elasto-plastic behavior of materials, a coupled model of plasticity and damage is proposed for the cohesive beam bond. The von Mises yield criterion, a modified perfectly plastic law and an exponential damage law are implemented to simulate behaviors of ductile materials such as steel and aluminum in tensile tests. It is then further applied to investigate the ductile fracture modes such as localized shear fracture and necking phenomenon with cup-and-cone shape. Finally, the proposed DEM model using cohesive plastic beam is applied to visualize the compression test of cylindrical steel sample and wrinkle deformation of steel tube under bucking due to axial compression. This paper is the first attempt to model ductile materials by DEM with cohesive beam bond in tension, compression and buckling. All of the numerical benchmarks demonstrate the power of DEM using cohesive beam bond to model ductile materials with fracture, large deformation and elasto-plastic behavior.

The use of effective full penetration of T-butt welds in welded moment connections

Full-penetration butt welds are often specified to connect the beam flanges to the column flange in welded moment resisting connections. Partial-penetration butt welds are cheaper than full-penetration butt welds and also more cost effective when compared to large fillet welds. EN 1993-1-8 standard includes a definition of an “effective full penetration of T-butt welds” implying that it can be used to replace butt welds leading to cost savings. This study evaluates the seismic performance of welded beam-to-column connections using effective full penetration of T-butt welds. Three full-scale T-shaped specimens were tested under cyclic loading. The results demonstrate that the effective full-penetration butt welds work very well under seismic loading, forcing the failure mode into the beam and enabling considerable energy to be dissipated within the beam plastic hinge, with no failure in the beam to column welds. Mock-up specimens were fabricated under real workshop conditions to examine the feasibility of reliably fabricating the weld penetration profiles required by EN 1993-1-8. This paper makes recommendations to the use of “equivalent strength” partial-penetration butt welds that can be used by the designer and/or fabricator to replace full-penetration butt welds.

Experimental study of intermeshed steel connections manufactured using advanced cutting techniques

Advanced manufacturing techniques, such as plasma, waterjet, and laser can facilitate field assembly and disassembly of steel structural components, and therefore potentially transform how steel structures are designed and constructed. These techniques have opened up an opportunity to create a new class of steel connections that rely on intermeshed (i.e. interlocked) components in lieu of traditional connectors such as weld and bolt. This paper presents an experimental investigation on the mechanics of such intermeshed steel connections manufactured by high-definition plasma and waterjet cutting. Four full-scale specimens with an intermeshed connection were designed to resist gravity loading in steel frames. The experimental testing program focused on the behavior of intermeshed connections under vertical loads including pure flexural and combined flexural-shear loading. Both global load-deflection response and local deformation were measured to provide insights into the complex load transfer mechanisms. The experiments demonstrated ample load carrying capacity, approaching the beam plastic moment, and ample ductility, approaching a deflection over span length ratio of 1/60 to 1/40, through the interaction of individual components. Analysis of the test data also raises important questions that must be addressed for the practical design of these connections.

Вплив режиму електронно-променевого зварювання, термічної обробки і пластичної деформації на міцність з’єднань алюмінієвого сплаву 1570

Вплив режиму електронно-променевого зварювання, термічної обробки і пластичної деформації на міцність з’єднань алюмінієвого сплаву 1570

Effect of mode of electron beam welding, heat treatment and plastic deformation on strength of joints of aluminium 1570 alloy

Effect of mode of electron beam welding, heat treatment and plastic deformation on strength of joints of aluminium 1570 alloy

Study on seismic behavior of reinforced concrete column-steel beam side joints

ABSTRACTIn this paper, a steel beam insert RCS side joint specimen is designed, and the low-cycle reciprocating loading test has been studied by designing a similar form of side joint specimen. At the same time, the hysteretic curve, skeleton curve, ductility, energy consumption, stiffness, bearing capacity degradation, and other seismic performance indexes are studied. The test results show that the failure mode of the specimen under the low-cycle reciprocating loading is the failure of the steel beam plastic hinge, which conforms to the seismic conceptual design principle of “strong column and weak beam”. The hysteresis curve of the specimen is relatively full, and the equivalent viscous damping coefficient is higher than that of ordinary reinforced concrete joints, showing better ductility and energy dissipation capacity. On the basis of experiments, Combined with ABAQUS finite element software, the variables of five parameters including insert length of steel beam, width of steel beam end plate, height of beam, axial compression ratio and embedded carrier board are analyzed, and the influence of these factors on the seismic performance of joints is also researched. By the method of variable analysis, the optimum value of each parameter is provided, which provides a reference for joint design.

Computer Simulation of Composite Beams Dynamic Behavior

The paper is devoted to the computer simulation of polymer composite beams dynamic behavior. The use opportunity of one-dimensional beam models for the design of composite elements instead of three-dimensional ones is discussed. The tree-dimensional modeling is implemented using the finite-element software SIMULIA Abaqus considering the orthotropic properties of the composite material. For the one-dimensional modeling two hypothesis of the internal friction – local and nonlocal – are applied and compared. The Kelvin-Voigt hypothesis is used as a local damping model. The nonlocal model is based on the nonlocal mechanics principals and obtained using the Galerkin method. The example glass fiber reinforced plastic beam with the fixed ends is considered under an instantly applied load. The parameters of the nonlocal damping model are defined using the least squares method. The flexibility of the nonlocal damping model is shown and the use opportunity of one-dimensional beam models for the design of composite elements is justified.

Defining of nonlocal damping model parameters based on composite beam dynamic behaviour numerical simulation results

The nonlocal model of internal damping is considered in this paper using the Euler-Bernoulli beam with fixed ends as an example. Equation of beam motion considering nonlocal damping is solved by Galerkin method to develop the model. The required number ofeigenmodes is obtained for the beam under an instantly applied distributed load. The influenceof nonlocal damping model parameters variation on the beam vibration process simulation results is shown. The beam is considered under a periodic deterministic distributed load. Defining of nonlocal damping model parameters is carried out using results of numerical three-dimensional finite element simulation. The parameters are defined for the glass fibre reinforced plastic beam with the fixed ends under the instantly applied distributed load. The parameters obtained for two different kernel functions and corresponding standard errors are compared. An opportunity of one-dimensional beam model use for the design of composite elements is shown and justified.

Anisotropic elastic-plastic behavior of architected pyramidal lattice materials

The initial and subsequent yield surfaces for architected pyramidal lattice materials are investigated analytically. Considering lattice struts as elastic-perfectly plastic thin beams subjected to both axial force and bending moment, a set of nonlinear elastic-plastic constitutive relations for a strut is proposed. Moreover, we phenomenologically present anisotropic pressure-dependent yield functions for pyramidal lattices. Comparison of planar yield surfaces of pyramidal lattices predicted by analytical approach to the ones obtained from phenomenological models shows a good agreement for the type of external loads and range of strains investigated in this study. Investigating the normality between the plastic strain vectors and yield surfaces, the obtained results demonstrate the associative nature of the flow rule. We have also emphasized on utilizing hollow-tapered struts as the constituent of pyramidal lattices. To this end, we analytically found that hollow-tapered struts can remarkably improve the effective stiffness and yield strength of bending-dominant pyramidal lattices.

Effect of cyclic flange local buckling on the capacity of steel members

Cyclic flange local buckling typically occurs when plastic hinges form in the beams and columns of special moment resisting frames subject to seismic excitation. While local buckling in beam plastic hinges has been investigated in the past for monotonic loading situations, the effect of cyclic flange local buckling on beam and column behaviours is not yet well understood. In order to address this shortcoming, nineteen half-scale T-section specimens are tested under cyclic axial loads in a configuration intended to replicate the cyclic demands imposed on flanges of beams and columns in their plastic hinge region. The main experimental variables are flange slenderness ratio, level of web restraint, and loading scheme (monotonic versus cyclic). Validated computational studies are performed to expand the parameter space. The test data and computational results show that T-section members that meet the current highly ductile limit can suffer excessive axial strength degradation under cyclic axial loading. The effect of slenderness ratios on column compression capacity due to strength degradation of flanges is evaluated and quantified.