Composite Frame Research Articles

Design and Evaluation of Hybrid Passive Spring Damper Ankle Foot Orthosis for Gait Performance in Drop Foot Patients: A Feasibility Study.

Passive and hybrid passive Ankle foot orthoses (AFOs) are the prevalent prescription in drop foot patients to prevent toe dragging during the swing phase. While, these AFOs have some limitations like inability to overcome foot slap, limitation in forward propulsion and inappropriate power generate at the push off. The aim of this study was to design a novel spring damper and evaluate the immediate effects of this AFO on improving the ankle kinetic and kinematic in drop foot patients. This AFO was generated from carbon composite frame and foot section with posterior hinge and spring damper actuator that controlled plantar flexion resistance at the early stance, freely dorsi flexion movement with the ability to store energy during mid-stance movement as well as restore this energy at the pre swing phase. This AFO was assessed on ten drop foot patients who used Posterior Leaf Spring AFO conditions and walked at their self-comfortable walking speed. Then the ankle kinetic and kinematic data in two conditions of with PLS (Posterior Leaf Spring) AFO, and novel spring damper AFO were assessed. Results showed a significant improve in the immediate effect of the kinetic and kinematic parameters. In conclusion, spring damper AFO improved all ankle angles in entire gait cycle as well as the ankle moments and power. Therefore, this AFO should be consider as a selective AFO in drop foot patients.

Experimental assessment of an asymmetric steel–concrete frame under a column loss scenario

Several noteworthy accidents clearly pointed out the risk of disproportioned collapse of framed structures. Design codes recently recognized it by adding a new requirement: the structural robustness. Among the different approaches to check robustness, the most popular is associated with the column loss scenario: the analysis should verify that, in case of a column loss, an alternative load path does exist, limiting the portion of structure affected by collapse. Consequently, numerous experimental and numerical studies of 2D and 3D structures were carried out in recent years to identify the mechanism of load transfer from the damaged to the undamaged part of the structure. This knowledge becomes an essential and fundamental key for assuring adequate resistance against progressive collapse by the development of catenary action in the beams and membrane action in the floor slab. Studies of reinforced concrete systems and of bare steel sub-assemblies are numerous. More recent is the focus on the response of steel–concrete composite structures subjected to accidental events. Furthermore, most of these studies focused on the characterization of 2D sub-assemblies or 3D in-scale framed structures. This paper presents an experimental assessment of the structural response of a 3D full-scale steel and concrete composite frame under the column loss scenario. The results are finally compared with the response of a frame with the same overall geometry but different columns’ layout, tested by the Authors within the same research programme.

Optimal Roving Winding on Toroidal Parts of Composite Frames.

Frames made of polymer composites are increasingly used in the aerospace, automotive, and agricultural industries. A frequently used technology in the production line of composite frames is winding rovings onto a non-load-bearing frame to form the structure using an industrial robot and a winding head, which is solidified through a subsequent heat-treatment pressure process. In this technology, the most difficult procedure is the winding of the curved parts of a composite frame. The primary concern is to ensure the proper winding angles, minimize the gaps and overlaps, and ensure the homogeneity of the wound layers. In practice, the curved frame parts very often geometrically form sections of a torus. In this work, the difficulty of achieving a uniform winding of toroidal parts is described and quantified. It is shown that attaining the required winding quality depends significantly on the geometrical parameters of the torus in question. A mathematical model with a detailed procedure describing how to determine the number of rovings of a given width on toroidal parts is presented. The results of this work are illustrated with practical examples of today's industrial problems.

Numerical assessment of an enhanced stiffened extended end-plate joint for composite frame structures

This paper presents the numerical assessment of a novel enhanced Bolted Stiffened Extended End-Plate (BSEEP) connection for steel frames with composite beams and H-shaped columns in the strong direction. Strain demand is a critical local response that directly controls rupture initiation, and it is more crucial in composite beams since the neutral axis shifts upwards due to the composite action. The proposed connection, called URBS-BSEEP, employs a reduced section in the beam upper flange to mitigate the strain demand problem and provide a stable and symmetric plastic hinge in the desired location. Nonlinear FEM is employed to study joint cyclic behavior. Eleven specimens are designed to compare the proposed connection with existing configurations and to investigate the effects of the slab isolation from the column, shear stud removal, reduced section geometry, and slab thickness. Hysteresis curves, ductilities, failure modes, strain profiles, and energy dissipation capacities are compared. The results indicate the superior performance of the connection compared to the conventional counterparts.

Analysis of Biomechanical Characteristics of External Fixators with Steel and Composite Frames during Anterior–Posterior Bending

This paper presents a comparative analysis of the biomechanical characteristics of an external fixator with a frame made of two different materials (stainless steel and composite material) during anterior–posterior bending. Before the test itself, two representative configurations of the Sarafix fixator were selected for application on the lower leg and upper extremities under the designations B50 and C50, which are most widely used in orthopedic practice. The examination of the biomechanical characteristics of the external fixator was carried out using the structural analysis of the construction performance of the Sarafix fixator using the finite element method, the results of which were verified through experimental tests. The developed experimental and FEM models study the movement of the fracture crack and enable the determination of the stiffness of structural designs as well as the control of the generated stresses at the characteristic locations of the fixator. The results show that the fixator with a carbon frame has lower stresses at critical points in the construction compared to the fixator with a steel frame, in the amount of up to 49% (at the measuring point MT+) or up to 46% (at the measuring point MT−) for both fixture test configurations. The fixator with a carbon frame has greater displacements at the fracture site compared to the fixator with a steel frame, in the amount of up to 45% (for configuration B50) or up to 31% (for configuration C50). The stiffness of the structure for both test configurations of the fixator is lower in the fixator with a carbon frame compared to the fixator with a steel frame by up to 27%. Based on the findings of this study, we can conclude that a fixator with a steel frame has better biomechanical characteristics compared to a carbon frame.

Damage Evaluation of a Three-story Composite Steel Frame subjected to External Explosion

Damage Evaluation of a Three-story Composite Steel Frame subjected to External Explosion

Research and development of the control system of space multi-dimensional profiling and planing based on PLC

Aiming at the complex processing problem of a rectangular composite plate with warpage in space to remove both sides of the frame and ensure the maximum of the inner core plate of the composite plate after removing both sides of the frame, a space multi-dimensional profiling and planing control system based on PLC is developed. According to the process requirements, the overall design of the space profiling and planing system is carried out, focusing on solving the problem of planing the space warping of the composite board frame. In the aspect of system hardware, the scheme selection, mechanical structure design, pneumatic control scheme design and electrical control scheme design are carried out; In the aspect of system software, based on the TIAPortal software platform, the PLC profiling program is compiled, and the human-computer interaction of the touch screen is designed. The profiling and planing process of composite plate is realized on the prototype, which improves the production efficiency while realizing automation.

Seismic behavior of concentric and eccentric New-RCS through-beam joints

Composite frame structures with high-strength reinforced concrete columns (New RC) and steel beams (S) are called New RCS systems. The key to the development of the New RCS system is the development of beam-column joint details. Thus, in this study, four large-scale beam-column subassembly specimens: three interior joint specimens, and one exterior joint specimen, were designed and cyclically tested to investigate the seismic behavior of the New RCS joint. Two tested interior joint specimens had beams framing to the New RC column with eccentricities, while the other specimens had concentrically framing beams. All the specimens exhibited stable and ductile hysteretic responses. The experimental study showed that the proposed joint details could develop the desirable beam flexural yielding while limiting joint damage for drift levels up to 6%. However, at very high drift levels (≥ 6%), the overstrength of the highly compact cross-section of the steel beams of the test specimens resulted in significant joint damage for the interior joint specimens. The experimental study demonstrated that the proposed New RCS joints were able to accommodate eccentrically framing beams without hampering the seismic response.

Comparative study on failure mechanism of multi-storey planar composite frames with RC beams to CFST columns subjected to compartment fire

This paper presents a theoretical study of the failure mechanism of planar composite frames composed of reinforced concrete (RC) beams to concrete-filled steel tubular (CFST) columns subjected to compartment fire. The numerical analyses on the planar composite frames with multiple stories and spans are meant to reproduce the conditions of framed members in multi-storey composite structures in real buildings. A refined finite element model is established and calibrated against the thermal and mechanical results from physical testing and shows good reliability in general. Using this model, this study proposes comparative analyses on the failure mechanisms of three typical composite frames, and discusses the effects of two significant parameters: the beam-to-column linear stiffness ratio and the fire protection thickness of the composite column. The responses of the heated composite frames, including the rotational deformation and stiffness degradation of framed joints, the internal force redistribution within framed members, and the failure mode of framed structures are investigated and discussed. The results indicate that there are two important parameters should be considered in the design of composite frames in fire.

Artificial bi-functional layers promoting Zn2+ desolvation and homogeneous deposition for reversible zinc metal anodes

Rechargeable aqueous zinc-ion hybrid supercapacitors (ZHSs) are drawing extensive attention because of their cost-effectiveness and diminished safety hazards. Nevertheless, large-scale application of ZHSs has been hindered by the severe side reactions and rampant dendrites growth on the surface of Zn metal anodes. Herein, we propose a three-dimensional organic–inorganic composite frame material as an artificial bi-functional layer coated on the zinc foil, featuring nitrogenous functional groups with zincophilicity (abbreviated as NCFM@Zn). The nitrogen (N) site's strong adsorption capacity and synergistic effect of the sub-nanopore size promote rapid desolvation of zinc ions and reduce side reactions, while also prolonging galvanized nucleation's Sand's time and allowing for even nucleation. Moreover, the uniform distribution of N on the layer results in homogeneous zinc ions flux and supports consistent zinc plating while inhibiting dendrites generation. As a result of this unique artificial bi-functional layer, symmetric Zn cells can survive 2500 h at 2.5 mA cm−2. High-areal-capacity zinc||activated carbon hybrid supercapacitors also demonstrate 20,000 cycles at high Coulombic efficiency, thus highlighting the utter convenience and potential of this strategy for modifying rechargeable metal hybrid supercapacitor surfaces.

Seismic performance of bidirectional bolted drilled cut RBS-CFT connections under cyclic loads

Welded connections were widely used in different regions of the world for ease of fabrication and good performance under gravity load. However, Northridge (1994) and Kobe (1995) earthquakes demonstrated that seismic performance of welded connections has been inferior as compared to that of bolted connections. Reduced beam section (RBS) has been one of the effective methods to enhance seismic performance in terms of energy dissipation capacity and ductility. Drilled-cut RBS-CFT connections have been gaining acceptance for enhancing overall seismic performance of steel moment resisting frames. However, no comparative study has been reported in the literature on RBS-CFT connection with bidirectional bolts for evaluation of their seismic performance. In view of the above, experimental study has been carried out for evaluation of seismic performance of two variants of RBS-CFT connections with constant drilled cut (CD-cut) and varied drilled cut (VD-cut) RBS. Both the drilled cut RBS-CFT connections are found to be semi-rigid in nature and exhibited stable hysteretic behavior. Test results showed that the cumulative energy dissipation capacity in the VD-cut connections is marginally higher than CD-cut connection. VD-cut RBS-CFT connections effectively reduced the lateral-torsional deformation. The load-carrying capacity and stiffness degradation ratio of VD-cut RBS-CFT connection is higher than CD-cut RBS-CFT connection. Damping of the both connections are nearly of similar order. Recorded strain data of both connections showed that plastic hinge confined only on drilled zone of the beam. Further, a detailed numerical simulation of force-deformation envelope curve of RBS-CFT connections was carried out using ABAQUS software. Simulated force-deformation envelope curves are found to be in close agreement with those obtained from experimental investigation. Both connections meet the seismic requirements of the AISC specified for composite special moment-resisting frames (SMRFs) by achieving rotational capacity of 0.04 radians without any damage in the joint panel region.

Evaluation and story drift ratio limits of structures with separated gravity- and lateral-load-resisting systems using pushover analysis

In recent years, China has strongly advocated the development of prefabricated buildings. To meet the growing demand for housing construction, it is necessary to develop high-rise prefabricated structures. To increase the construction efficiency of high-rise prefabricated structures, an innovative composite structural system with separated gravity- and lateral-load-resisting systems (referred to as an ‘innovative structural system’) was developed, and its seismic performance was evaluated. At the component level, efficient numerical models of the composite frames, reinforced-concrete (RC) shear walls, RC coupling beams, and braces in the innovative structural system were developed using the general finite-element software MSC.Marc. The fragility curves of these components were developed through parametric analysis and a literature review of previous research and database documents. At the system level, through finite-element analysis, the seismic mechanism of the innovative structural system under lateral loads, including the lateral displacement pattern, plastic development pattern, and failure mode, was compared with that of the traditional composite frame–shear wall system. A static pushover analysis was performed, and the displacement response results of the innovative structural system under the maximum considered earthquake strength were obtained. The damage to the components was evaluated via fragility analysis, and the seismic performance of the innovative structural system was compared with that of the traditional system according to the safety factor. The results indicated that for high-rise composite structural systems with separated gravity- and lateral-load-resisting systems under frequently occurring earthquakes, the reasonable range of the story drift ratio limit in design is 1/800 to 1/1000, and a limit value of 1/1000 is recommended conservatively.

Long-term thermal productivity of polystyrene concrete in a new composite wall in a fixed formwork

Purpose. Determination of the term of long-term thermal productivity of expanded polystyrene concrete in a new composite frame wall in a fixed formwork. Methodology. Methods of analysis and synthesis were used to conduct a patent search and develop a research methodology. The search was conducted using the patent database of Ukrainian Institute of Scientific and Technical Expertise and Information. Experimental studies were carried out in accordance with State Standard of Ukraine B V.2.7-38-95. The essence of the experiment consisted in reproducing the natural conditions of the “freeze-thaw-heat” cycle and measuring the thermal insulation characteristics of the main insulating material – polystyrene concrete – before and after the tests. Based on this, a conclusion was made about the long-term thermal productivity of the expanded polystyrene concrete in a new composite wall in the fixed formwork. The calculation of the dependence of thermal productivity on the number of cycles was carried out by arithmetic means using standard methods and programs such as Microsoft Excel. Findings. New technical solution of a composite wall made of expanded polystyrene concrete in a fixed formwork using light steel thin-walled structures has been created. A methodology for researching the long-term thermal productivity of this composite wall has been developed. An experimental study was conducted to research the influence of cyclic temperature changes (“freeze-thaw-heat”) on the long-term thermal productivity of the main heat-insulating element of the composite wall – expanded polystyrene concrete. An appropriate analytical model of the dependence of long-term thermal productivity of expanded polystyrene concrete samples on the number of “freeze-thaw-heat” cycles was calculated. The possibility of effective operation of the structure was confirmed by checking the normative values of the resource index and the factor of climatic destruction influence of materials during operation on their long-term thermal productivity. Implementation of a new composite wall solution in construction was conducted. Originality. For the first time, the dependence of cyclic temperature effects on the long-term thermal productivity of expanded polystyrene concrete in a new composite wall made in a fixed formwork using light steel thin-walled structures was determined, which made it possible to establish its effective operation life. This scientific result makes it possible to reduce material consumption, ensure economy, increase operational reliability and energy-efficient properties, and increase the service life of the composite wall. Practical value. New solution for installing a composite wall made of expanded polystyrene concrete in a fixed formwork using light steel thin-walled structures was developed and its effective thermal operation within the legally established term was substantiated. The period of effective exploitation of expanded polystyrene concrete as the least durable component of a composite wall is substantiated. Approbation of this design was carried out by installing it on a real construction site, which showed an increase in the manufacturability of construction processes compared to traditional enclosing structures.

Experimental and analytical study on steel-concrete-ECC composite frames with URSP-S connectors

To improve the slab crack resistance in the hogging moment region of steel-concrete composite frames, this paper proposes using Engineered Cementitious Composite (ECC) and Uplift-Restricted and Slip-Permitted Screw-type (URSP-S) connectors near the columns of the frames, the structural behavior of the innovative steel-concrete-ECC composite frames were experimentally and numerically investigated. Firstly, five 1/2-scaled steel-concrete composite frames were experimentally studied under vertical uniform slab loading and horizontal low cyclic loading. The failure mode and cracking, load-displacement relationship, stiffness and strength degradation, energy dissipating, and strain of composite frames with ECC and URSP-S connectors were analyzed, and good cooperative behavior and overall seismic performance were found. Then, it was compared with the results of the other four specimens with different slab materials and shear connector types. The experimental results showed that the use of ECC and URSP-S connectors improved slab crack resistance 55% in terms of crack width, and rarely influenced the structural performance of the composite frames. ECC played a major role in controlling the crack width while URSP-S connector played a major role in controlling the crack number. In addition, based on the test specimen with ECC and URSP-S connectors, an elaborate finite element (FE) model was developed and validated by the test results in terms of cyclic curves and failure mode. Moreover, supplementary modeling analyses with various parameters on the influence of the frame capacity were performed, where steel beam height was the most influential parameter.

Structural performance of rigid shear connectors in concrete encased steel composite columns

Concrete encased steel (CES) composite columns possess a wide variety of advantages in constructing concrete-steel composite frames. In order to achieve the composite behaviour of these columns, it is necessary to transfer the force between steel and concrete, effectively. Therefore, shear connectors should be used on the contact surface between concrete and steel. In this research, behaviour of the rigid shear connectors in CES composite columns is numerically studied. The results – obtained from the finite element analysis – were validated against the experimental results. Afterwards, parametric studies were conducted to investigate the effective parameters on the behaviour of the rigid shear connectors. The results show that the length, the thickness and the penetration depth of the shear connector, the compressive strength of concrete and the thickness of concrete cover have a noticeable effect on the strength and stiffness of the shear connector. Moreover, increasing the length and the penetration depth of the shear connector, and the thickness of the concrete would increase the residual strength level. In general, the rigid shear connector is mobilized under a much smaller slippage (between concrete and steel), as compared to the stud shear connector, and provides greater stiffness and strength. Moreover, due to being encased in reinforced concrete, it can also provide sufficient ductility. Finally, based on the parametric studies, a formula is suggested to predict the ultimate shear capacity of the rigid shear connector in the CES composite columns.

Anti-collapse mechanism and reinforcement methods of composite frame with CFST columns and infill walls

Masonry infill walls serve as building partitions and are generally considered non-structural components. Their weights are considered in progressive collapse analysis, but the resistance of the infill walls is normally ignored in design standards. Based on the reasonable selection of constitutive models, a refined finite element (FE) model for the collapse resistance of concrete-filled steel tubular (CFST) composite frame with infill walls was established by ABAQUS/Explicit. Cohesive elements were inserted between different masonry blocks to simulate the mortar joints. The collapse resistance contribution and reinforcement methods analysis of the CFST frame with infill walls were carried out based on the validated FE models. Results show that the infill walls significantly contribute to resisting vertical load in the initial loading stage, with a maximum contribution of 55.3%. The infill walls, which are treated as the equivalent compressive struts, change the load-resisting path and effectively improve the load redistribution ability of the frame. The V-type oblique arrangement of tie rebars has better tie effect and collapse resistance of the frame than other arrangements. After pasting the CFRP sheet and spraying the ECC material to reinforce infill walls, the peak load can be increased by 25.1% and 22.9% respectively, and the ultimate load can be increased by 96.2% and 74.5% respectively. X-type pasting the CFRP sheet reinforcement has a better collapse resistance than others. Furthermore, based on the simplification of the infill walls as the diagonal struts, the simplified calculation formulas of anti-collapse capacity of CFST frame with infill walls were studied.

Wave propagation analysis in laminated composite periodic frame structures using spectral finite element method

In this article, wave propagation in a one-dimensional (1-D) composite periodic frame structure is analyzed using spectral finite elements (SFE) method together with Bloch’s theorem. Each element in the periodic frame structure is modeled as a first-order shear deformation theory (FSDT) beam element and wave equations for the beam elements are derived using FSDT considering axial, flexural, and shear deformations. Next, these equations are solved using the frequency domain SFE method to obtain an elemental dynamic stiffness matrix which on assembly gives the dynamic stiffness matrix for the unit cell of the periodic structure. A polynomial eigenvalue problem is formulated thereafter using Bloch’s theorem to evaluate the dispersion coefficients and wave amplitude ratios. Finally, the entire periodic frame is modeled as homogenized two-noded elements capturing the wave response of the PS with a drastic reduction in computational cost. The results obtained using the present method are validated with finite element simulation using ANSYS mechanical Ansys Parametric Design Language (APDL). The frequency band gaps observed in the frequency domain responses are investigated and corroborated with those predicted by the dispersion relations. This is followed by a detailed parametric study on the influence of different parameters on the band gap characteristics. The present method provides a scheme of wave propagation analysis of composite periodic frames with substantial computational efficiency.

Seismic evaluation of composite moment frames subjected to near-fault ground motions

This paper investigates the seismic behavior of composite special moment frames (CSMF) under near-fault ground motions. For this purpose, two factors, response modification and deflection amplification are chosen. 3-, 9- and 20-story frames of SAC joint venture are modeled in OpenSees software. The nonlinear behavior of the panel zone was modeled using a 2D joint element and a tri-linear relation. FEMA p695 near-fault ground motions are applied in Incremental Dynamic Analysis (IDA). Ultimately, the obtained results are compared to the values recommended by ASCE provisions. The average results indicate that the ASCE provision can appropriately predict the response modification factor; however, in the case of deflection amplitude, IDA results may not show good agreement with ASCE/SEI 7 suggested value. Also, by comparing the results of composite special moment frames with steel moment frames from literature, it has been revealed that, unlike ductility, overstrength increases significantly when concrete filled tube columns are employed in special moment frames.

Imaging across multiple spatial scales with the multi-camera array microscope

This paper experimentally examines different configurations of a multi-camera array microscope (MCAM) imaging technology. The MCAM is based upon a densely packed array of “micro-cameras” to jointly image across a large field-of-view (FOV) at high resolution. Each micro-camera within the array images a unique area of a sample of interest, and then all acquired data with 54 micro-cameras are digitally combined into composite frames, whose total pixel counts significantly exceed the pixel counts of standard microscope systems. We present results from three unique MCAM configurations for different use cases. First, we demonstrate a configuration that simultaneously images and estimates the 3D object depth across a 100×135mm2 FOV at approximately 20 µm resolution, which results in 0.15 gigapixels (GP) per snapshot. Second, we demonstrate an MCAM configuration that records video across a continuous 83×123mm2 FOV with twofold increased resolution (0.48 GP per frame). Finally, we report a third high-resolution configuration (2 µm resolution) that can rapidly produce 9.8 GP composites of large histopathology specimens.

The influence of component defect states on bandgaps of 2D composite beam frame structures

This paper investigates the vibration bandgap properties of two-dimensional (2D) periodic composite beam frame structures with component defects. Combined with the topological characteristics of the structure, a generalized position coordinate system is proposed, and an assembly method of the stiffness matrix for the virtual full component model is presented. Then the spectral equations of motion of the whole 2D periodic composite beam frame structures and the ones with component defects are established. Compared with the frequency-domain solutions calculated using the finite element method, the accuracy and the feasibility of the spectral element method (SEM) solutions are verified. It can be shown that the SEM is suitable for analyzing the vibration bandgap properties, and the influence of different component defects and their combination on the bandgap characteristics of 2D periodic frame structures is studied. The results show that forbidden gap splitting will occur in the main bandgap of the structure, but the degree of influence varies. The results also show that the influence of component defects on unsymmetrical or irregular positions of the vibration bandgaps of periodic frame structures is greater than the one in symmetrical or regular positions.