Catenary Effect Research Articles

Pre-tension design and research of cable net structure for space modular deployable antenna

Modular deployable antennas represent an ideal structural form for the development of large-aperture antennas because of their flexibility, adaptability, and high versatility. To enhance the surface accuracy of the antenna after deployment, a comprehensive pre-tension design method that considers truss deformation and tension uniformity is proposed. First, the configuration design of the antenna cable net is constructed, and the mathematical models for cable length under surface accuracy requirements and boundary nodes are established considering catenary effects. Second, the distribution patterns of cable net structure nodes and segments are analyzed, leading to the creation of node coordinate matrices and cable net connection matrices. A basic model for cable net pre-tension design is developed based on the fundamental principles of force density. Furthermore, a multi-objective optimization of cable net pre-tension is performed using a genetic algorithm, considering truss structure deformation and tension uniformity as dual factors. Finally, the developed model is applied to design a single-module cable net structure, and numerical simulation is used for validation. Research results show that the overall surface form error is 0.32 mm, and the maximum tension ratio of cable net on the front cable net surface is 1.54, whereas the maximum tension ratio of tension ties is 2.28, thereby meeting the design requirements. Numerical simulation shows that the maximum deformation of the cable net structure is 0.16 mm, validating the correctness of the model. This research can provide valuable insights and references for the pre-tension design and research of cable net structures in other antennas.

Dynamic Performance of Multi-Column Removal Framed Structures Subjected to Impact and Heaped Loads

The dynamic performance of a multi-column removal frame (MCRF) suffering from accidental impacts and uniform superstructure loads has largely been neglected in previous studies. To this end, a one-fifth scaled test model was set up to study the MCRF failure state and collapse mechanism. A numerical model was established and validated according to the collapse experiment. Parametric studies were conducted to investigate the effect of the impact height, heaped load (static uniform pressure on the slab), and frame storey on the MCRF dynamic response. The results indicated that: (i) the tension membrane, compressive arch and catenary effect were the main anti-collapse mechanisms in MCRF structures; (ii) according to the peak impact force under the increased collapse impact height (1.5 ∼ 2.5 m), a stronger local response and a slightly enhanced dynamic performance were successively presented on the hammer–concrete interaction; (iii) when the heaped load was increased, the structural plastic deformation capacity provided by the catenary action was better than that given by the compressive arch effect; (iv) the transient impact interaction was almost independent of the frame storey, but the MCRF anti-collapse performance was greatly affected by it. Finally, a collapse prediction method was given to evaluate the ultimate anti-collapse capacity of MCRF structures.

Research on dynamic response prediction of semi-submersible wind turbine platform in real sea test model based on machine learning

The motion response of floating offshore wind turbine (FOWT) platform is closely related to its safety, and model test is the most direct method to fully study its dynamic characteristic behavior. In this paper the dynamic response of intermediate-scale physical semi-submersible FOWT model test under real sea environmental loads is studied and compared with the numerical model dynamic response, demonstrating that some limitations of small-scale physical model tests can be overcome, such as the catenary effect of mooring lines. It is found that the nonlinear dynamic characteristics of the physical model under actual marine environmental loads can be captured by the numerical model, which can improve the fidelity of model test data for semi-submersible FOWT structures in the existing literature. The dynamic response database of semi-submersible FOWT under complex wind, wave and current loads was established by using a numerical model with high accuracy, and was used in the prediction research of different machine learning algorithm models such as Genetic Algorithm optimization Back Propagation neural network (GA-BP), Support Vector Machine (SVM) and Gaussian Process (GP). The research shows that the relationship between the environmental load and the dynamic response of FOWT can be established by using the machine learning model, in which the number of samples has a significant impact on the prediction of the mooring line tension, and the research on the three algorithm models shows that GP performs significantly better than GA-BP and SVM in predicting the mean value of surge, pitch and mooring line force. For the dynamic response prediction of mooring line tension, GP model can get better results. In the future, this method will become an important method to predict and monitor the dynamic response of FOWT.

Progressive collapse analysis and retrofit of a steel-RC building considering catenary effect

Despite their low probability of occurrence, the consequences of abnormal loads may be very important, both in economic terms and in terms of human lives. This has stimulated the development of strengthening and retrofitting techniques to mitigate the risk of progressive collapse of buildings. However, their application to real-scale buildings is still lacking. This paper describes the progressive collapse analysis and retrofit of a steel-reinforced concrete hospital building. The progressive collapse performance under different column removal scenarios is investigated using both nonlinear static and dynamic analyses. A two-step pushdown analysis procedure is developed to estimate the dynamic amplification factor (DIF) to partially compensate for the dynamic effects. The results have revealed the vulnerability of the building due to the low tensile axial resistance of the beam-to-column connections. Both the hypothesis of DIF = 2 and the almost inversely proportional relationship between DIF and vertical deflection have proven to be ineffective due to the catenary effect. A retrofit solution is proposed based on an outrigger-belt truss system on the rooftop level. The results show the effectiveness of the retrofit strategy. The displacement dynamic response of the retrofitted structure is significantly reduced if compared to the original structure since it goes from about 20 cm to less than 1 cm. However, the tensile strength of column-to-column connections of the top three floors is inadequate and should be increased. To this aim, a strengthening intervention is developed to increase the tensile strength from 565 kN to 965 kN, thus allowing the tensile axial forces caused by the column removed to be resisted.

The collapse evaluation method of steel moment-resisting frames based on dynamic increase factor

Considered the application of structural vibration characteristic parameters in the field of structural health monitoring and damage identification, the relationship between the structural dynamic increase factors (DIFs) and the collapse resistance of structure under the column removal scenario, is studied. Referring to previous researches, the load–displacement curve of structures under static collapse condition is simplified to be a multi-parameter broken line, which is used as the analysis and calculation model for the structural DIFs under the column removal scenario. Based on the model, the displacement-based DIF (DIFu) and the load-based DIF (DIFp) are derived with the help of energy balance method, and the development laws of DIFs are nalysed under different strength of catenary effect and ductility of structures. It is found that the value of DIFs in the catenary stage of structures is positively correlated with the ductility and strength of catenary effect of structures. A new structural collapse evaluation method is proposed based on the evaluation laws of DIFs. By dint of previous experiments the finite element model is established and the collapse evaluation method is verified. Finally, the different strain rates of steel are introduced in the FEM. It is found that the effect of medium and high strain rate of steel on the limit displacement of structures against column removal could be neglected, which further improves the evaluation method.

Experimental and Numerical Study on Progressive Collapse of the Midcolumn in a Glulam Timber Frame Exposed to Fire

This paper presents experimental and numerical investigations on the progressive collapse behavior of a two-story glulam frame when the middle column is exposed to ISO834 standard fire. The stress characteristics, temperature distributions, and deformation relationship curves of the bottom middle column after a fire are obtained. The collapse resistance performance and the mechanism of the glulam structure under local fire are studied in combination with the failure mode of the frame. The experimental results show that the failure time of the middle column in fire is 16.8 min, and the time to determine the progressive collapse of the structure is 17.17 min when the rotation angle exceeds the limit. The structure can remain stable for some time after the failure of the fire column, but as the fire continues to spread, the structure will collapse further. In addition, a temperature-field analysis model with the grid element type of DC3D8 and a structural field analysis model with the grid element type of C3D8R was established by using ABAQUS software under the experimental conditions. The numerical simulation is carried out by means of thermal–mechanical sequential coupling. The numerical simulation results show that the temperature of the beam end rose to more than 300 °C in about 15 min although it was not directly exposed to fire. The temperature of the whole connector at the pillar foot in the bottom column reached more than 700 °C when the fire time reached 60 min. The numerical simulation results agree well with the experimental results. The analysis results show that, in the failure process of the fire column, the junction of beam ends begins to produce stretching force to form a catenary effect. As the fire time increases, the catenary effect eventually fails. The stretching force at the beam end rapidly decreases and withdraws from the work, causing the progressive collapse of the frame.

Numerical study on the anti-impact performance of novel concrete-filled steel tubular joint with corrugated web and cover plates

To improve the impact resistance of the traditional concrete-filled steel tubular (CFST) bolt-welded hybrid joint, a novel connection configuration with the corrugated web and the cover plate was proposed in this study. The failure modes and bearing mechanism of the novel connection under vertical dynamic impact load were studied in detail based on the finite element model validated against the previous test results. The falling-debris impact on top of the joint column can be simplified as the drop hammer of the non-deformed discrete shell rigid body. The effect of the design parameters including the dimensions of the cover plate and corrugated web was analyzed numerically. Results show that the existence of the cover plate increases the bending capacity of the steel beam and delays the fracture of the connection. The fracture and local buckling of the web are delayed due to the folding effect of the corrugated web. The energy consumption of the joint with the cover plate and the corrugated web is 20.2%–52.8% higher than that of the traditional joint, in which the corrugated web and bottom flange with cover plate contribute 6.6%–8.3% and 16.3%–32.2% respectively. The time history curves of the internal force of the joints are mainly consisted of the beam mechanism stage, the catenary mechanism stage and the failure stage. Through the parameter analysis, it is suggested that the long diameter of the bolt hole is 0.08–0.09 times of the beam height and the thickness of the cover plate is 0.42–0.50 times of the flange thickness to reach the optimum impact resistance. Furthermore, a simplified calculation method for the impact resistance considering the effect of the corrugated web and the cover plate is proposed. Impact energy can be absorbed by the bending effect and the catenary effect of the joint. The relative errors of the predicted impact resistance and energy absorption by theoretical formulas are within +10% compared with the experimental and numerical results.

Axial–Flexural Interaction in Axially Restrained Beams in Progressive Collapse Column-Removal Scenarios

Progressive collapse alternate path scenarios are often characterized by restrained beam configurations that provide resistance to structural collapse after column removal. While various methods have been presented to model the behavior of restrained beams, opportunities exist for mechanics-based estimation of the complete static and dynamic load-deflection curves. This paper presents an axially restrained beam (ARB) model that incorporates axial–flexural interaction throughout the entire static load-deflection curve including the elastic material range, the plastic flexural dominant range, the range beyond plastic flexure with increasing catenary effect, and the full catenary range. Energy methods are applied to static load-deflection curves to determine dynamic load-deflection relationships. A parametric study was conducted to assess the accuracy of the ARB method compared to nonlinear, dynamic time history finite-element (FE) analyses. The model compares favorably to results of FE models with average estimates of dynamic deflection within 2.1% for ideal moment connections and 7.7% for configurations combining simple and moment resisting connections.

Experimental and Numerical Study on Progressive Collapse Analysis of a Glulam Frame Structure: I. Side Column Exposed to Fire

This paper presents experimental and numerical investigations on progressive collapse behavior of a two-story glulam frame when the side column is exposed to ISO834 standard fire. The collapse mechanism initiated by fire is identified. The experimental results show that the progressive collapse of a glulam frame could be described for three stages, namely bending effect stage, catenary effect stage and failure stage, respectively. These stages are discussed in detail to understand the structural behavior before and during collapse. It is demonstrated that the entire frame slopes towards the side of the heated column, and the “overturning” collapse occurs eventually. The catenary effect of beams is the main reason for the progressive collapse of the frame. In addition, a finite element model of a glulam frame is established to simulate the progressive collapse behavior. The effects of axial loads on the columns are summarized. The numerical simulation results agree well with the experimental results, which could verify the effectiveness and practicability of finite element simulation. Furthermore, the progressive collapse resistance of the frame in practical design were proposed.

Study on anti-progressive collapse performance of cellular steel frames with different web opening shapes

In this paper, cellular beam-column joints with different opening shapes were taken as the object of study to investigate the resistance to progressive collapse of weakened beam-column joints through a combination of experiments and numerical simulations. Opening shapes include circular, rectangular and hexagonal. The development laws of failure mode, vertical force–deformation response, internal force development and resistance mechanism of the specimens were analyzed, and based on the validated finite element model, the effects of weakening parameters of openings with different opening shapes on the performance of the beam-column joints against progressive collapse were studied. The results demonstrate that the load carrying capacity and deformation capacity of cellular joints with different opening shapes have different degrees of improvement compared with the foundation joints, and exhibit the largest deformation in the first opening area near the column flange, where the ductile failure at the weakened section occurs in the hexagonal cellular opening, and the catenary effect can be fully developed, showing the best performance under the designed opening size, rectangular is the second and circular the worst. In addition, the failure mode and load carrying capacity of the specimens can be effectively improved by changing the opening weakening parameters. Increasing the opening diameter (parameter a) and opening edge distance (parameter c) within a reasonable range can effectively improve the vertical resistance and deformability of the specimens, and the effect of opening spacing (parameter b) on the structural load response is negligible. In the design of collapse resistance of cellular beam-column joints, it is recommended to increase the values of parameters a and c appropriately and to reduce the value of parameter b appropriately under the premise of ensuring the structural load carrying capacity, which is more conducive to the catenary action.

Collapse resistance analysis of composite beam–column substructure considering the location of column failure

In actual situations, it is not possible to determine the exact location where the column will fail (in a member or building structure). Based on the location of the failure, the lateral constraint stiffness of the directly affected area of the structure will change, affecting the structure's anti-collapse performance. This study aims to explore how the location of the failure column affects the collapse resistance of composite beam–column substructures; the double-sided restraint substructure (DSRS) and the single-sided restraint substructure (SSRS) were chosen as research objects, and the two test structures were subjected to static loading tests to compare their collapse resistance. The results showed that the two specimens had similar failure modes and deformation patterns. In addition, the development trend of the internal force of the two specimens was comparable, but the axial force of the SSRS was smaller. The contribution of the catenary mechanism of DSRS was approximately 24%, while the catenary effect of SSRS was not fully exerted, leading to only 15% of the total resistance. Two specimens were modeled in ABAQUS, and the finite element method was verified by comparing the simulation results with the test results. A full-scale model was established to analyze the effects of the lateral restraint stiffness of DSRS and SSRS and the side column size on the collapse resistance of the substructure. The finite element analysis results are as follows: (1) lateral restraint stiffness had less influence on the small deformation stage of the substructure; (2) the beam end tension force played a significant role in the collapse resistance of the substructure; (3) increasing the horizontal lateral restraint stiffness can effectively improve the anti-collapse performance of composite beam–column substructure; (4) the side column can provide effective axial and rotational restraint for the beam end. Having too large or too small a side column can have an adverse effect on the structure. Moreover, the larger the side column size, the better the continuous collapse resistance of the substructure when the beam–column linear stiffness ratio is between 0.6 and 1.1.

Catenary effect of multi-story steel moment frame under asymmetric horizontal constraint

In terms of the structural robustness, there have been enormous studies on the catenary effect of frame structure subjected to mid-column removal. However, it will be a more common scenario that the column at various locations will probably fail so that the asymmetric constraint from the surrounding frame will be imposed upon the affected bays. Regarding the limited studies involving these issues, a static pull-down testing is hereby performed to explore the catenary effect of the multi-story frame under asymmetric horizontal constraint. Based on the full-range structural response, the floor dependency of the catenary effect and the asymmetric constraint have been confirmed to have a significant influence on the failure sequence of bolted connections, and the evolutionary histories of internal forces. The floor dependency of the catenary effect will cause the greatest deformation demand and consequently the earliest failures of connections at the 1st floor, while the asymmetric constraint will lead to the earlier ruptures of the connection adjacent to the constraint bay than those connected to the corner column. In addition, these two factors will also result in the weak catenary effect of the overall frame, featuring the negligible vertical resistance contribution from the axial tension at the 2nd and 3rd floors due to the insufficient horizontal constraint. Eventually, the high-fidelity numerical analysis including the fracture simulation is performed and validated by the excellent agreement involving the full-range force-displacement relationship, failure modes and sequences, and the local deformation.

Force Transfer Mechanism and Component-Based Model of Cast-Steel-Stiffened Circular-Tube-Column Frames for Progressive Collapse Analysis

In this paper, the system response, stress redistribution, failure mode, and catenary effect of steel frames with circular tube columns and cast steel stiffener (CSS) joints under a sudden column removal scenario were revealed. Based on this force transfer mechanism analysis, a practical and computationally efficient component-based model considering catenary effects and CSS joint details with a series of springs was established and validated by a detailed solid-element method. By using this component-based model, the proper dynamic response increase factor of the CSS joint frames was investigated. The results show that the great overall stiffness and strength of the CSS limit the deformation of the column front shell. Therefore, the CSS joint frames have superior performance for progressive collapse prevention than the frames using welded joints without stiffeners. In addition, the component-based model is validated to be effective and the dynamic response increase factor of the frames with circular tube columns and CSS joints is smaller than 2.0.

Pull-down test and numerical validation of multi-story steel moment frame using pulley-based loading system

Regarding the structural robustness against progressive collapse, recent studies have revealed that the catenary effect is the critical resisting mechanism for the frame structures under large vertical displacement. The previous studies of the single floor beam-column subassemblies suggest that the catenary effect is greatly affected by the connection performance as well as the horizontal restraint. However, the conventional push-down testing might not appropriately represent the horizontal constraint from the surrounding bays and the vertical loading condition under the uniformly distributed gravity loads. Therefore, the static pull-down test is performed on the multi-story steel moment frame equipped with straight-reduced-section splice plates (SRSP). It is used for high deformability of beam-to-column connection. In addition, a vertical loading system using the fixed pulleys for load transferring is newly proposed for a feasible and safe loading procedure. The experimental results show that the growth of vertical resistance can be mainly attributed to the plastic hardening and the consecutive catenary effect. The maximum resistance is governed by the first rupture of SRSP at the overall chord rotation of 0.178 rad, indicating high deformability of bolted connection with SRSP. Based on the failure sequence of connections and the internal force as well as deformation response, the floor dependency of catenary effect can be significantly observed. It is characterized by the earliest failure emerging at the 1st floor, followed by the consecutive ruptures observed at the upper floors. In terms of the internal force, the vertical contribution derived from the tensile force will be gradually rising for the connection at the 1st floor, in contrast to the negligible catenary effect at the 2nd and 3rd floors. Eventually, the numerical simulation is performed based on the previously proposed material model. The simulated full-range force-displacement curve with the low percentage error of 0.8% for the first rupture displacement demonstrates the validity of the numerical model in terms of the full-range behaviors of multi-story frame structure.

Drop-weight impact tests on free from damage beam to column connections

Modern standards require the design of resilient structures, highlighting the need for systems able to assure life safety and an easy repairability. Indeed, a resilient design includes the conception and the realization of a structure able to sustain accidental or exceptional events with limited and easy-to-repair damages. Within this framework, steel Moment Resisting Frames (MRFs) equipped with Slide Hinge Joints, have proved to be extremely efficient for the seismic performance and damage avoidance. However, to date, limited knowledge exists on their behaviour under exceptional events and significant research efforts are still required.In order to provide a contribution to fill this gap, this paper focuses on the behaviour of SHJs with Symmetric Friction Dampers (SFDs) under drop-weight impact. SHJs are normally designed to act as the dissipative fuse of MRFs under seismic loadings. However, they can be also effectively exploited to improve the robustness of steel buildings through the increase of the local ductility, which may ensure also the activation of catenary effects in beams and tying forces.The response of MRFs equipped with such a joint under extreme dynamic loading condition is not straightforward. It requires a deep knowledge of their behaviour as a function of the strain rate. In this paper the results of six drop weight impact tests on double-sided SHJs are presented and a 3D finite element model is developed in ABAQUS software. A parametric analysis is then performed to investigate the influence of the key parameters affecting the joint behaviour, namely: the impact velocity, the impact mass and the impact energy.In order to characterize the joint behaviour under impact, the paper provides a correlation between the dissipation rate of the joint, under impact, and the input energy. The work is limited to a geometric range and to the joint typology here considered, however, the methodology and the results can be generalized.Overall, the joints perform better under higher velocities rather than higher masses due to strain rate effects. However, a clear correlation between the DIF and the velocity of rotation of the joint is difficult to establish.

Progressive Collapse Performance of Steel Beam-to-Column Connections: Critical Review of Experimental Results

Background: The steel beam-to-column connections are vulnerable structural elements when a building loses one or more of its vertical load-carrying components due to abnormal or accidental loading conditions. After a column is destroyed by abnormal loads, the tensile axial force of the beam gradually increased, while the bending moment decreased, and the load-resistance mechanism shifts from a flexural mechanism to a catenary mechanism, with the axial force becoming the prevailing factor. Aims: This paper investigates the progressive collapse performance of steel beam-to-column connections. While undergoing large deformation, the beam-to-column connections are subjected to moment, shear, and tension in conjunction with high ductility demand. Their behavior under monotonic loading depends on the moment-axial tension interaction and greatly affects the progressive collapse resistance of the structure. This paper presents a critical review of experimental tests of different types of steel beam-column joints (flexible, rigid, and semi-rigid) under a central-column-removal scenario. Methods: The experimental results, including load-deformation relationships, failure modes, and catenary effects, are described in detail. The findings are used to evaluate the rotation capacity of different types of steel beam-to-column connections. The results are compared to the acceptance criteria specified by the main progressive collapse guidelines for several beam-to-column connection categories. Results: In simple (flexible) joints, the stiffness and strength at higher drift angles essentially depend on the tensile capacity of the connection that prevents, in some cases, the full development of the catenary mechanism. The connection depth alone does not seem to be an effective parameter to predict the rotational capacity of beam-to-column connections, since different connections with similar values of the connection depth result in very different values of the maximum rotation capacity. In fully rigid and semi-rigid connections, after the column removal, the flexural resistance controls the behavior at the preliminary phase, and the tensile force is almost zero. With increased downward displacement, the axial tensile force also increases, developing a catenary mechanism. Although the stiffness of rigid and semi-rigid connections is higher than flexible connections, both categories result in similar rotation capacity. Conclusion: In all the simple connections herein considered, the plastic rotation capacity obtained by tests was found much higher than the code recommended values that are probably too conservative. On the contrary, for one rigid and two semi-rigid connections, the values of the plastic rotation capacity obtained by tests are lower than the corresponding recommended values. Thus, the suggested acceptance criteria proved to be out of the conservative side.

Numerical study of the robustness of steel moment connections under catenary effect

The local fracture will directly result in the consequent decrease in the vertical resistance of the beam-to-column assembly in the steel frame structure, which emphasizes the necessity of the ductile fracture prediction in the numerical study. In this paper, a monotonic plasticity and ductile fracture model is used to characterize the stress state and loading path dependency of the yield surface, as well as the combined effects of the shear stress and hydrostatic pressure on the damage evolution. On the basis of the validated material model, five push-down tests of the beam-to-column assemblies with different moment connections are chosen for the validation of this modeling method in terms of overall vertical force–displacement curves and the local crack initiation and propagation. Thereafter, the numerical studies of the weld access hole reveal that the gentle slope of transition cutting and larger distance between toe of weld access hole and flange weld will raise the connection ductility. The relationship between ultimate chord rotation and these two variables can be formulated by the empirical formulas. As for the bolted web-to-column connection, the deformation capacity can be improved by using compact bolt arrangement and larger bolt size. The implementation of the shear tab with long-slotted holes will also enhance the connection ductility under catenary mechanism. In general, these findings will be benefit to improve the robustness of the steel frame structure, along with the quantitative estimation of connection ductility for checking the structural safety.

Fracture behavior of high-strength bolted steel connections at elevated temperatures

In fire events, to utilize catenary effect and accommodate large deformation in beams demands a sufficient deformation capacity and ductility in steel bolted connections, which is not well considered in design practice. Therefore, for performance-based fire safety design, it becomes very essential to accurately predict the fracture behavior of steel bolted connections at elevated temperatures. However, experimentally predicting their fracture behavior is very costly at elevated temperatures and limited by the scale of structural components. Therefore, this paper proposes a numerical analysis approach and investigates the fracture behavior of high-strength bolted steel connections at elevated temperatures based on the validated numerical analysis approach. The temperature-dependent material properties including true stress-strain curves and fracture parameters in a three-stage fracture model (describing the pure tension, pure shear, and combined tension and shear fracture behavior) for high-strength ASTM A325 bolt and A572 Grade 50 steel are firstly calibrated from and validated against their tensile and shear test results. They are further validated against the test results on single-bolted and multi-bolted connections at elevated temperatures, which were not used in the calibration of these material properties. The validated material properties and fracture parameters are finally proposed for fracture prediction of different types of bolted connections under various loading conditions at elevated temperatures. This study shows the potential of reasonable prediction of the fracture behavior for the steel bolted connections at elevated temperatures and under complicated loading conditions using a numerical analysis approach. According to the numerical analysis results, the degradation of shear fracture resistance of A325 bolts at elevated temperatures is more significant than that of A572 Grade 50 steel plate, which may lead to a bolt shear failure mode for these connections with a large end distance at high temperatures (>400 °C). It is also found that the fracture failure mode can significantly influence the degradation of the load and deformation capacities of high-strength steel bolted connections at elevated temperatures. With the bolt shear failure mode, the degradation of load and deformation capacities of steel bolted connections are more significant than that with plate tearing-out failure mode.

Push-out behaviour of demountable injected vs. blind-bolted connectors in FRP decks

The main challenge for realizing competitive hybrid steel-FRP structures, such as bridges, carparks, is to make the steel and FRP components work together. In this study shear resistance, stiffness and ductility of three types of demountable bolted shear connectors are examined. Two blind-bolted M20 shear connectors and a novel, injected steel-reinforced resin (SRR) connection are selected to perform push-out experiments in web-core FRP decks. Failure modes of excessive bearing in FRP and bolt shear failure for blind-bolted and injected connectors, respectively, are identified. Nonlinear, highly detailed finite element (FE) models were also built and validated by results of the push-out tests to provide insights to the load-transfer mechanism. Analysis of internal forces and deformation through FE results reveals that blind bolted shear connectors provide high shear resistance and slip capacity thanks to the shear sleeves and catenary effects. The injected SRR connector shows distinct and centric load transfer owing to gapless design.

Numerical Simulation of Catenary Effect of (RC) Frame Structure Based on MSC.Marc

Since the collapse of Ronan point apartment in 1960s, progressive collapse has become a research hotspot in civil engineering. In order to study and verify the catenary effect on the resistance of the reinforced concrete frame structure to the progressive collapse. Based on MSC.Marc software, a single-story plane frame structure of reinforced concrete frame structure was selected to establish a finite element model for numerical simulation, and the numerical simulation results was compared with the experimental data.