Moment-rotation Characteristics Research Articles

Mechanical properties of prestressed tendon-planted glulam beam-column connections under cyclic loading

Traditional glulam beam-column connections have the disadvantages of low bearing capacity, low stiffness, low ductility and poor energy dissipation ability. This paper proposed a new prestressed tendon-planted connection for glulam beam-column joints. Six groups of the connections were tested under reversed cyclic loading. The effects of the number and prestressed value of steel bars, tendon reinforcement ratio and tendon anchorage length on the performance of the connection were analyzed. The results indicated that the proposed connection showed ductile failure, involving the splitting failure of the beam and the bearing failure around the planting holes. The proposed configuration improves the ultimate bearing capacity, initial stiffness and energy dissipation performance, and slows down the stiffness degradation of the glulam beam-column connections. The number of steel bars and prestressed value have a positive effect on the initial stiffness of the joint, whilst the tendon reinforcement ratio has a significant positive influence on the bearing capacity of the joint. The bearing capacity of the joint no longer increases with the increase of the tendon anchorage length, when the anchorage length is 12.5 times greater than the tendon diameter. The prediction formula for the flexural capacity of the new joint is proposed, whilst the moment-rotation characteristics of the connection are also assessed.

Modeling the joint rotational stiffness of a radial-type flight intersection joint: An analytical approach, numerical simulation, and experimental validation

Joint rotational stiffness (JRS) of a flight intersection joint (FIJ) and its accurate quantification play an essential role in studying the dynamic modal characteristics of a flight vehicle. This JRS of a FIJ is mostly determined through elaborate experiments due to the non-availability of a reliable predictive model. Therefore, in this paper, an analytical model is proposed to evaluate JRS of a radial type FIJ when subjected to external bending moment. In this model, at first, the tensile and compressive part of the FIJ section is identified by determining the neutral axis position. The respective part's contributing stiffness is then estimated by employing a spring-mass model. Later, the JRS expression is derived from the moment equilibrium condition and expressed as a function of the stiffness of the tensile and compressive part and neutral axis position. Subsequently, finite element analysis (FEA) is conducted with different numbers of screws, followed by detailed experimental investigations. The proposed analytical model is validated with the results from FEA and experiments for different screw configurations of FIJ. Further, the proposed model is extended to account for the effect of joint clearances on the JRS and the corresponding moment-rotation characteristics of the FIJ.

Experimental behaviour of large-size beam-to-column steel joints for the DUNE Neutrino Experiment

This paper reports on an experimental investigation on a very large, bolted beam-to-column steel joint that will be extensively used in a new experimental facility for the study of neutrinos (DUNE experiment), hosted by the U.S. Department of Energy’s Fermilab. The dimensions of the members (HL 1100 in S460 steel) are uncommonly large at an experimental level and, consequently, the gathered experimental data is of utmost importance for the validation of the component method for large-size steel joints. The steel joint is subjected to static monotonic loading. Relevant instrumentation was used to monitor and assess the moment–rotation characteristics, experimental stiffness, and moment resistance. The experimental results are presented and analysed. Comparisons with design predictions according to EN 1993-1-8 and state-of-the-art FEA, show an excellent agreement, validating the application of the component method for very large joints.

Performance of baseplate connections in CFS storage rack systems: An experimental, numerical and theoretical study

The moment-rotation characteristic of a baseplate connection in cold-formed steel rack systems significantly depends on the floor anchoring arrangement and the axial compression of the uprights. Hence, this study aims to present the results of an experimental, numerical and theoretical investigation on baseplate connections of storage racks with six different anchoring configurations under various axial loads. First, the experimental results on three types of baseplates under monotonic lateral load and six different axial compression loads are presented. Then, a numerical simulation is performed and verified using the experimental test results. The validated numerical method is also utilized for evaluation of three new types of baseplates which are different in anchoring configuration. Finally, a theoretical approach is developed to determine the moment capacity and stiffness of the baseplate system. The results indicate that different anchoring arrangements result in different baseplate behaviour. In addition, the stiffness and moment capacity of the baseplate connections are influenced by the magnitude of axial compression loads.

Performance of SRC column-RC beam joints under combined axial and cyclic lateral loadings

Strong column-weak beam behavior of a concrete structure with reinforced concrete (RC) beams and steel reinforced concrete (SRC) columns can only be ensured during a seismic event if the premature failure of beam-column joints could be avoided. The RC beam-SRC column joints, however, require special design and reinforcement detailing due to the presence of structural steel sections in the columns. Two different detailing schemes have been explored in this study for the exterior RC beam-SRC column joints. The key parameters varied in these detailing schemes are the anchorage length of beam longitudinal bars and the provision of transverse stiffeners in the structural steel sections. Three large-scale test joint specimens have been tested under the combined axial load and the varying lateral cyclic displacements. The crack propagation patterns, hysteresis behavior, moment-rotation characteristics, lateral stiffnesses, and joint shear-distortion behaviors of the composite specimens have been compared with the RC specimen to verify the suitability of the studied configurations. The experimental moment-rotation behavior of the test specimens has been compared with the theoretical moment-rotation curves derived using the current code provisions. Finally, the recommendations for the suitable configuration of the composite connection between the SRC column and RC beam have been proposed.

Moment–rotation curve characteristics and initial rotational stiffness calculation method of angle connections

SummaryDue to recent advances in computational power, high efficiency and high precision semi‐rigid calculation methods of steel connections are necessary. In this paper, four connection experiments were designed to study the mechanical behavior of the top and seat angle connections. In the experiment, a monotonic load was applied at the end of the beam to study its moment–rotation characteristics. In addition, this paper proposed a second derivative method to determine the yield point, the starting point of the plastic strengthening stage, and the initial rotational stiffness of the connections according to the moment–rotation curve. Loading test experiments (EX) results and finite element analysis (FEA) results showed that the compression side angle stiffener has little effect on the initial rotational stiffness. Nevertheless, it can delay the top and seat angle connection in entering the elastoplastic stage and the starting point of the plastic strengthening stage. The results also showed that the tension side angle stiffener could significantly increase the initial rotational stiffness, but makes the angle connection enter the yield stage earlier. When the connection's top and seat angles have no stiffener, the elastoplastic deformation range on the curve is smaller. Finally, based on the theory of Plates and Shells, this paper proposed the calculation method for the deformation stiffness of the key components and the initial rotational stiffness of the connection. Results from the theoretical calculation method showed high calculation accuracy and high calculation efficiency, as compared with the EX and the FEA results.

Numerical and analytical study of stainless steel beam-to-column extended end-plate connections

Based on a shell finite element modeling protocol developed and verified by the first author in a previous study, a comprehensive investigation on stainless steel extended end-plate beam-to-column connections was carried out. A total of 180 connection configurations were numerically investigated, to establish a thorough understanding of the influence of a wide range of geometrical parameters on the behavior of this connection type commonly-used in earthquake-resistant steel structures. The initial stiffness; ultimate moment; rotation capacity; dissipative energy; ductility index; and failure patterns were compared and discussed. Furthermore, based on the data acquired from this parametric study, a simple analytical method, for predicting the moment-rotation (M-Φ) characteristics of stainless steel extended end-plate connections, was developed and validated. The results demonstrate that stainless steel extended end-plate connections can be designed to have substantial ductility and rotation capacity, more than satisfactory for beam-to-column joints of structures in seismic zones. In particular, connections with end-plate stiffeners displayed superior performance with enhanced ultimate moment and energy dissipation capacity. The recommended analytical method for M-Φ response of the joints is accurate, with an average error of less than 4% for the ultimate resistance and is robust as evidenced by its prediction of M-Φ response for models that were withheld from its initial calibration. The proposed equations provide, for the first time, a powerful analytical tool that can predict the complete moment-rotation curves of unstiffened and stiffened stainless steel extended end-plate joints, using easy-to-obtain geometric and material properties.

Moment-rotation behavior of semi-rigid web cleat connections

The behavior of beam-column semi-rigid connection plays an important role in the response of a steel moment resisting, stiffness and rotation capacity framed structure, especially under static loading conditions. In this study, the moment-rotation characteristics of semi-rigid bolted connections using web cleat connections with IPE standard profile is discussed, based on the experimental investigation. The study revealed that the moment resistance of beam-column semi-rigid connection is improved by increasing the height of the beam to the height of web cleat joint (H), and the increasing thickness of web and flange in web cleat joints. The aim was to provide necessary data to improve the Eurocode 3 and efficiently use residue IPE standard profiles, rather than send them back to the consumption cycle. While the resistance moment increased with an increase in H from Hmin to Hmax.

Numerical study of top-and seat-angle with double web-angle connection with high-strength steel

Past experimental research on top-and seat-angle with double web-angle connection (TSACW) was limited by the rate and magnitude of actuator displacement and hence results did not give information on failure mode and ultimate capacities of connection. Furthermore, extensive literature review on TSACW revealed the need for developing an accurate finite element approach to represent the characteristics of the moment-rotation behavior. Therefore, this study examined the influence of connection parameters on flexural resistance, stiffness, rotation, ductility and failure modes obtained for such joints. Explicit Finite element (FE) analyses of connection models were carried out by using ABAQUS/CAE to explore the effect of material properties of bolts and angles on moment-rotation (M-ϕ) characteristics of TSACW under monotonic loading. Applicability of six currently available M-ϕ functions was assessed by comparing them with those obtained from FE analyses. In most cases, the ultimate flexural resistance of TSACW was increased whilst its rotational capacity was decreased with the use of A572 or A514 angles with less pronounced effect on the initial stiffness. The connection failure was controlled via large deformations achieved by the top angle. Among the six selected M-ϕ functions, Richard-Abbott model was found suitable for fitting the normalized moment-rotation curves for TSACW joints.

Cold formed steel storage racks subjected to axial, shear and bending interactions

This research article aims to study the behaviour of expansion bolts under axial, shear and bending interaction of base plate connected cold form steel storage racks. The bilinear moment rotation relationship was adopted to identify the ultimate moment of resistance and stiffness of the base plate connected to a concrete block using M10 grade anchor bolt at different range of axial loads ranging from 25% to 100% there by the design strength of upright profile was studied. The dimension of the upright and the base plate thickness has to be changed so that the extreme stability under various ranges of axial and transverse loads had been studied. Using finite element analysis software (Abaqus), a model has been created and designed to observe moment rotation characteristics, behaviour of base plate under simultaneous axial, shear and bending interactions and compared with experimental analysis. Comparative studies reveal that there was no failure in the concrete block and when the upright thickness increases, the stiffness and moment of the base plate increases despite having a similar cross section. An interaction equation was developed to find the stiffness and ultimate moment of resistance of the base plate connection.

Spot and Adjust Filter: a New Image Filter for Image Enhancement and Noise Reduction

Wind and earthquake disasters in the world often cause billions of dollars of damage to buildings, most of which is to non-engineered buildings-especially homes. Wood-frame homes use connectors which exhibit partial rotational rigidity at the member ends, making analytical solutions difficult. This is due to the lack of information about the complex behavior of the connections used in this type of buildings, and the lack of a methodology to analyze light-timber frame buildings with flexible joints. In order to address the problem, tests were carried out to determine the moment rotation characteristics of wood joints made of conventional and mechanical fasteners. During testing, it was discovered that rotational stiffness of timber connections is a function of the axial load as well as the shear load. Comparison of ordinary timber connections with metal connectors were made. Resisting moment capacity of joints with different connectors were also determined. This paper presents a new method of testing for joint stiffness and the experimental results obtained during testing for stud-to-bottom-plate, rafter-to-ridge-board, and top-plate-to-rafter connections using different connectors.

Behaviour and modelling of connections in cold-formed steel single C-section portal frames

The flexural behaviour of eaves, apex and base connections for cold-formed steel single C-section portal frames is investigated through a series of connection tests and analyses of corresponding finite element models. The moment-rotation characteristics of the eaves, apex and base connections from the respective connection tests and the numerical models indicate good agreement between. The attainment of ultimate load by the eaves and the apex connection was normally preceded by significant deformation of connecting brackets. The eaves connections reached its ultimate load capacities upon fracture of screws or ply bearing of M8 bolts on the C-section lips while the apex connections attained their ultimate load capacities with the formation of inelastic buckling near the compression flange-web junction of one of the adjoining beams. The base connection tests exhibited large rotational deformation and capacity to deform with inelasticity mostly concentrated in the connector bracket. Based on the tests and numerical analyses, simplified nonlinear moment-rotation relations are established for eaves, apex and base connections.

Theoretical Bending Collapse of Hat-Section Tubes

This paper presents an attempt to modify an existing theoretical model to predict the bending collapse response of hat-section tubular structures. The analytical collapse model was based on Kim and Reid. Additional hinge lines created during deformation of the tube were examined and integrated with existing model to forming a modified analytical solution. Variation of the hinge moments were solved using limit analysis technique. Procedure for developing the finite element (FE) models of tube specimens was also presented. Moment-rotation characteristics from pure bending simulation were compared with analytical model and good agreement was achieved. The average of differences between simulation and calculation were found to be <5% within plastic region. In conclusion, the modified analytical solution has adequate capability to predict the moment-rotation relationship of hat-section tubes subject to pure bending..

Behaviour of stainless steel beam-to-column joints-part 2: Numerical modelling and parametric study

This paper reports a detailed numerical (FE) study on planar stainless steel beam-to-column joints. A nonlinear FE model is developed and validated against the first set on full-scale tests on stainless steel beam-to-column joints reported in the companion paper. The FE model is shown to accurately replicate the experimentally determined, initial stiffness, ultimate resistance, overall moment-rotation response and observed failure modes. Parametric studies are conducted to obtain the moment-rotation characteristics of a wide range of beam-to-column joints classified as semi-rigid and/or partial strength. Due to the low ductility of the bolts compared to the high ductility exhibited by all other stainless steel joint components, in all cases the strength and ductility of the simulated joints is limited by the failure of the connecting bolts. The design rules for stainless steel connections, which are based on the specifications of EN 1993-1-8 for carbon steel joints, are reviewed and are found to be overly conservative in terms of strength and inaccurate in terms of stiffness thus necessitating the development of novel design guidance in line with the observed structural response. These conclusions are in agreement with the ones reported in the companion paper.

Behaviour of stainless steel beam-to-column joints — Part 1: Experimental investigation

Research on stainless steel structures has primarily focused on the structural response of individual members, whilst the response of joints has received far less attention to date. This paper reports for the first time full-scale tests on stainless steel beam-to-column joints, subjected to static monotonic loads, whilst the companion paper reports numerical studies on similar connection typologies to the ones studied herein. The joint configurations tested include one flush and one extended end plate connection, two top and seated cleat connections, and two top, seated and web cleat connections of single-sided beam-to-column joints. All connected members and connecting parts including bolts, angle cleats and end plates are in Grade EN 1.4301 stainless steel. The full moment-rotation characteristics were recorded for each test and the experimentally derived stiffness and moment resistance for each joint was compared to the codified provisions of EN1993-1-8. It was verified that the connections displayed excellent ductility and attained loads much higher than the ones predicted by design standards for carbon steel joints.

Numerical Modelling of a Novel Joint System for Grid Shells with T Cross-sections

A novel joint system developed for single-layered steel grid shells with T cross-sections is presented in this paper. The joint system is bolted to facilitate quick and easy on-site assembly. First, a solid finite element model was built to investigate the behaviour of the developed joint system. The moment-rotation characteristics of the joint system were determined and the joint strength and stiffness was investigated. Key parameters influencing the behaviour of the joint were studied, such as bolt diameter, pretension, component geometry and normal force. As a second step, free-form roof structures with a span of 40÷80 meters were chosen and analysed with the developed joints. The previously obtained moment-rotation results were used as spring moment-rotation characteristics in beam finite element models. The load bearing capacity of the structures were determined. The results were compared to that of grid shells with rigid joints, and it was shown that the joint system is stiff enough.

Modified Three-Parameter Power Model to Predict Moment-Rotation Curve of Top- and Seat-Angle Connection

This study conducted on improving three-parameter power model [1] to estimate ultimate moment of connections based on the failure mechanisms developed by more practical means and finally, to predict moment-rotation relations of top- and seat-angle connections for intrinsic replacement of experimental curves and/or finite element (FE) analysis results. Bolt stiffness, shear and bending deformation of tension angle and prying force acted on tension angle are considered to determine the ultimate moment of connections implementing two possible failure mechanisms. These failure mechanisms are developed based on the concept of T-stub model [2] and adjusted the position of plastic hinges applying advanced FE analysis method [3-6]. Then, moment-rotation (M_r) characteristics of top- and seat-angle connections are constructed applying proposed modified three-parameter power model. Applicability of the proposed formulation is examined by comparing M_r curves and ultimate moment capacities with those of Kishi-Chen power model, FE analyses [3, 4] and experiments [7, 8]. The comparison implies that proposed formulation and Kishi-Chen’s method both achieved closer approximation for maximum of cases and better accuracy for the modified cases to drive M_r curves of the connections; but ultimate moments of the connections defined by the proposed method is more realistic than that predicted by Kishi-Chen power model.

Static balancing of an inverted pendulum with prestressed torsion bars

This paper presents a method for the design of a statically balanced inverted pendulum. The non-linear moment-rotation characteristic of the pendulum's weight is approximated by a piecewise linear characteristic. Each transition is realized by engaging or disengaging one or more torsion bars, by means of mechanical stops. The whole set of torsion bars is located along the hinge axis of the pendulum. A prototype with three parallel torsion bars was built. Experimental evaluation of the prototype revealed a 99% work reduction of the balanced pendulum with respect to the unbalanced one.

Axial force–bending moment interaction in a jointing system part I: (Experimental study)

In a space structure, each connection can be subjected to different ratios of axial force to bending moment. In this paper, a test procedure was presented that enables realistic testing of a steel space structure jointing system by applying different combinations of axial forces and bending moments to the connection. The main objective of the test programme was the experimental study of the effects of compressive axial force on the moment–rotation characteristic of a joint. A suitable test set-up was designed and constructed to achieve a reasonable simulation of real connection behaviour. From the experimental results, it has been found that the compressive axial force has three important effects on the moment–rotation characteristics. It increases the initial slope of the moment–rotation curve with the reduction in the stiffness occurring more slowly to begin with but increasing more rapidly afterwards. It decreases the ultimate moment capacity of the connection. It also gives rise to softening of the connection behaviour.

Moment-Rotation Characteristics for Flexible Beam-to-Column Steel Joint Exposed to Fire

Moment-Rotation Characteristics for Flexible Beam-to-Column Steel Joint Exposed to Fire