Rotation Capacity Research Articles

Experimental investigation of the rotational characteristics of a novel hybrid laminated glass beam-column connection prototype

This article presents an experimental investigation of the rotational characteristics of a novel hybrid laminated glass beam-column connection prototype. The testing of small-scale prototype specimens is conducted to assess the effect of the main structural parameters such as glass pane thickness, interlayer and reinforcement properties on the rotational characteristics. To explore the possibility of using different lamination technologies for the realization of the joints, two different bonding technologies are considered separately: (a) autoclave and (b) UV-curing lamination. The specimens are subjected to a pair of self-equilibrated compressive forces up to failure in a custom-made setup. Digital image correlation (DIC) measurements together with strain gauges are used for tracking the kinematics of the main components. It was found that the prototype is able to develop a significant post-fracture and rotational capacity in a properly balanced combination of structural and material parameters. The results are presented in terms of moment-rotation (M - θ) curves, strains evolution in the steel and evolution of the crack patterns. Experimental observations suggest that depending on the choice of structural parameters three failure modes are possible: (a) crushing failure of the joint core, (b) plastic failure of the adjoining sections and (c) failure due to debonding of one of the bars in tension. It is concluded that one can achieve a desirable post-fracture and ultimate behaviour by properly balancing the structural and material parameters. Additionally, pull-out opening and tensile stresses in steel are measured at the interrupted section, revealing a transition in sectional behaviour from fully interrupted to a hybrid section over a certain transition length.

Test on seismic behaviors of stainless steel bolted extended end-plate beam-column joints

This study conducted tests on the seismic behavior of austenitic stainless steel bolted extended end-plate beam-column joints, which have been few reported. Considering the influence of material type, end-plate thickness, bolt diameter, panel zone thickness, and loading scheme, 11 stainless steel joints and two carbon steel joints were designed and tested. Material properties, joint failure modes, moment-rotation curves, bolt load distributions, and joint component yield sequences were reported in detail. Experimental research showed that the beam-column joints in austenitic stainless steel experienced four failure modes, i.e. plastic hinge at the beam end, fracture failure of weld between the beam flange and end-plate, bolt rupture failure, and composite failure. All the tested joints had good seismic behavior, with rotation capacity greater than 0.03 rad. The influence of joint configurations on the seismic behavior were analyzed. The results indicated that the end-plate thickness, end-plate stiffener, and bolt diameter had a substantial impact on the joint seismic behavior, while the thickness of column web in panel zone, material properties, and loading scheme had a comparatively small effect. The initial rotational stiffness and moment resistance(yield moment) of joint obtained from the experiment were compared with the predictions of the EN1993-1-8, Design Guide 16, and JGJ 82-2011. Comparisons indicated that the EN1993-1-8 overestimated the initial rotational stiffness; Both the EN1993-1-8 and JGJ 82-2011 underestimated the moment resistance, while the predictions from the Design Guide 16 were significantly higher than the moment resistance and closer to the ultimate moment.

Research on the bi-directional bending performance of plug-pin scaffold joints in low-temperature

In this paper, a pinned scaffolding node is proposed and studied with Q355 steel and sorbite stainless steel. Twelve sets of forward and reverse bending tests were designed to study the bi-directional bending performance at temperatures of +20 °C, −20 °C, and − 40 °C. The test results show that as the temperature decreases, the initial rotational stiffness and bearing capacity of the QSJ and the SSSJ both increase. Under the same temperature conditions, the yield bearing capacity and maximum bearing capacity of the SSSJ are greater than those of the QSJ. However, the SSSJ is susceptible to cracking in the weak zone of the C-shaped member subjected to forward bending moments in low-temperature environments, which requires attention in design and use. A finite element model can accurately simulate the bi-directional bending performance of the joint. The results show that increasing the thickness of the U-shaped members by 1–1.5 mm significantly increases the maximum load capacity of the joint. The wall thickness of the pipe has no influence on the bending properties of the joint, but the initial stiffness of the joint can be increased by the depth of wedging, a wall thickness of 6 mm is recommended for C-members. The form of damage to the SSSJ can be improved by increasing the curvature of the upper edge of the C-member at the wedge. The results of this paper can provide methods and references for the engineering design of scaffolding as well as for testing in low-temperature environments.

Study on the seismic performance of through-tenon joints with pullout tenon gaps between mortise and tenon shoulder

Through-tenon joints are widely used in ancient timber buildings. To study the influence of the gaps between mortise and tenon shoulder on the seismic performance of through-tenon joints, a 1:3.52 scaled model was constructed and used for low cyclic loading test. Finite element analysis was conducted to study the mechanical behavior of the through-tenon joint. The seismic performance parameters of the model such as moment-rotation hysteresis curves, envelope curves, degradation of rigidity, and energy dissipation capacity were compared. The analyses showed similar changing characteristics, which indicated that the finite element analysis results were reliable. Based on the results, 7 through-tenon joint finite element analysis models with different gaps between mortise and tenon shoulder were established. The seismic performance of each of the through-tenon joints with different gaps between mortise and tenon shoulder were studied. The moment-rotation hysteresis curve of the through-tenon joint had an obvious pinching effect, and the through-tenon joint had good rotational loading capacity and good deformation ability. The peak rotational loading capacity, initial stiffness, and energy dissipation capacity of the joint decreased, while the gap between mortise and tenon shoulder increased.

An analytical framework for the evaluation of the progressive collapse resistance of precast concrete hollow-core floors

Buildings may be subjected to extreme events such as earthquakes, tsunamis, explosions, fires, or terroristic attacks during their service life. The current codes and guidelines provide three methods for the structural robustness assessment of buildings subjected to unidentified accidental actions: (i) the Tie Force, (ii) the Alternate Load Path and (iii) the Key Element methods. In particular, the Alternate Load Path is a direct method based on the evaluation of the ability of the structure and/or sub-assembly to effectively redistribute the applied loads and develop alternate load paths after the loss of a load-bearing element. In the literature, several studies aimed to investigate the progressive collapse performance of monolithic reinforced concrete structures, with almost no attention paid to precast concrete structures. In this work, in the context of the Alternate Load Path methods, an analytical framework is proposed and validated for the assessment of the progressive collapse resistance of precast concrete floors composed of hollow-core units and precast concrete beams, where the role played by tying reinforcement is analysed. Firstly, the study focuses on double-span hollow-core floor units by providing: (i) the static pushdown response, (ii) the dynamic capacity curve as well as the dynamic amplification factor and (iii) a practical robustness indicator, based on geometrical and mechanical features through the calculation of the chord rotation capacity, a fundamental parameter to be adopted for progressive collapse resistance. Finally, the method is extended to an entire hollow-core floor system, where both distributed ties in slab units and concentrated ties in beams are considered in the system resistance. Due to its simplicity, the analytical framework is considered useful for practical purposes, as reported with an example in the Appendix.

Chord Rotation Capacity and Strength of Diagonally Reinforced Concrete Coupling Beams

Chord Rotation Capacity and Strength of Diagonally Reinforced Concrete Coupling Beams

Parametric Design and Shape Sensing of Geared Back Frame Shell Structure for Floating Cylindrical Reflector Antenna off the Coast

At present, numerous reflector antennas have been constructed worldwide on land. However, there are few applications of reflector antennas directly set off the coast. To expand the application region of reflector antennas, a floating cylindrical reflector antenna (FCRA) driven by the moving mass was developed to implement the elevation angle adjustment. Firstly, the structure design is introduced in detail. The design parameters are stated and analyzed to obtain the kinematic relationship while considering the water surface constraint. Then, the effects of each variable on the rotation capacity and structural stability are discussed. Further, the feasibility of the elevation angle adjustment process is demonstrated by using a prototype model test and software simulation. Finally, the deformation analyses and shape sensing of the back frame are carried out on the basis of the inverse finite element method (iFEM). We concluded that this new structure is feasible and expected to sit off the coast. In addition, the iFEM algorithm with sub-region reconstruction was proved to be suitable for the shape sensing of the over-constrained FCRA during the angle adjustment process via several quasi-static sampling moments.

Experimental and analytical studies of size effects on compressive ductility response of Ultra-High-Performance Fiber-Reinforced concrete

Ultra-high-performance fiber-reinforced concrete (UHPFRC) has gained a great deal of increasing interest in structural engineering applications, particularly where high ductility, strength, and high impact resistance are of prime concern. This study focuses primarily on the size effects ductility characteristics of UHPFRC with varying fiber concentrations subjected to uniaxial compressive load. It shows how to process the data from compression cylinder tests to extract the size-dependent strain at peak stress to provide a generic size-dependent stress–strain analytical model. For a slenderness factor of 2, the predicted peak stress from the analytical model deviated 0.34%, 0.26%, and 10.5% from the experimental peak stress results for a fiber concentration of 1%, 2%, and 3%, respectively, indicating good estimate of the analytical model with the experimental results. Furthermore, a numerical flexural segmental moment-rotation approach is applied to incorporate an analytical model to quantify apparently disparate UHPFRC member strength and ductility. Tests have shown that it is not the enhancement in the material concrete compressive strength but the phenomenal brittle ductility nature, observed as a result of increasing the slenderness of the specimen; in contrast, a substantial increase in ductility was achieved after crushing of concrete due to the addition of fibers. A size-dependent analytical approach has estimated good fit with the experimental and other published results. Finally, numerical simulation using a segmental approach at the ultimate limit state of rotation dealing with flexural ductility is significantly influenced by the increase in slenderness factor of the specimens and fiber concentrations.This is evident as the rotation capacity decreased by 62% and 75% for a slenderness factor of 3 and 4, respectively, compared to the slenderness factor 2, when the fiber concentration was 1%. Furthermore, for 2% fiber concentration, the decrease was 54%, and 80%, and for 3% fiber concentration, the decrease was found to be 49%, and 79% for the slenderness factor of 3 and 4, respectively in comparison to the slenderness factor 2, suggesting both slenderness factor and fiber concentration have a significant impact on the flexural ductility.

Seismic Performance and Calculation Method of Precast Reduced Beam Section Connection

To prevent brittle damage and improve the post-earthquake rapid repair capability of beam–column connections, a precast reduced beam section (PRBS) connection joint that can be rapidly repaired under earthquake action was proposed in this study. Four specimens, including a repaired specimen, were subjected to a quasi-static test to investigate the seismic performance and repair ability of the connection. Seismic performance indices such as the failure mode, hysteresis curve, skeleton curve, strain distribution, and ductility were obtained through observations and analyses. The results indicated that the novel connection exhibited superior load-bearing, energy dissipation, and rotation capacities, compared to the welded flange-bolted web and traditional bone-weakened connections. This novel connection effectively relocated the plastic hinge to alter the failure mode and prevent brittle damage. Additionally, rapid post-earthquake repair was achieved by replacing the dog-bone-style splice section, maintaining a high load-bearing capacity and seismic performance. Finite element (FE) models were established to analyze the mechanical behavior of the specimens, and a parametric analysis was conducted to study the influence of different parameters on the load-bearing capacity of the connection. Based on the experimental and FE analysis results, the possible yield and failure modes of the connection were analyzed, and a calculation method for the bearing capacity of the PRBS connection was proposed. A comparative result demonstrates that the proposed calculation method can accurately predict the load-carrying capacity of a connection.

Numerical modelling of moment-transmitting timber connections

In recent years, the use of timber in construction substantially increased due to the material’s renewable nature, lower climate impact and increased economic competitiveness. Another driving factor is great improvements in modelling techniques for the design of timber structures. Suitable prediction of the connection behaviour, as a fundamental part of the structural behaviour of timber structures, is crucial for a more economic and reliable design. However, the more realistic and complete connection models, the more complex and difficult to handle they are, which might hinder their practical application. A good trade-off between complexity and computational efficiency can be achieved with the so-called Beam-On-Foundation (BOF) method, which is applied herein in a 2-step hierarchical model to analyse and predict the rotational stiffness, ductile capacity and load distribution among fasteners of four different configurations of moment transmitting beam-to-column timber-to-timber connections. The connection model is validated with experiments on the global response of the connection as well as with a 3-D solid FEM model. The herein proposed connection model well predicted the overall connection response and provided insight into the local fastener behaviour. As compared to the 3-D solid model, which additionally gives access to more realistic local stresses in the timber, the 2-step model is however much more efficient with a great reduction of computation time. This makes the approach suitable for parametric studies and the analysis and engineering design of timber structures.

How embodied is cognition? fMRI and behavioral evidence for common neural resources underlying motor planning and mental rotation of bodily stimuli.

Functional neuroimaging shows that dorsal frontoparietal regions exhibit conjoint activity during various motor and cognitive tasks. However, it is unclear whether these regions serve several, computationally independent functions, or underlie a motor "core process" that is reused to serve higher-order functions. We hypothesized that mental rotation capacity relies on a phylogenetically older motor process that is rooted within these areas. This hypothesis entails that neural and cognitive resources recruited during motor planning predict performance in seemingly unrelated mental rotation tasks. To test this hypothesis, we first identified brain regions associated with motor planning by measuring functional activations to internally-triggered vs externally-triggered finger presses in 30 healthy participants. Internally-triggered finger presses yielded significant activations in parietal, premotor, and occipitotemporal regions. We then asked participants to perform two mental rotation tasks outside the scanner, consisting of hands or letters as stimuli. Parietal and premotor activations were significant predictors of individual reaction times when mental rotation involved hands. We found no association between motor planning and performance in mental rotation of letters. Our results indicate that neural resources in parietal and premotor cortex recruited during motor planning also contribute to mental rotation of bodily stimuli, suggesting a common core component underlying both capacities.

Component Modeling for Fire Behavior of Shear Tab Connections

During a building fire scenario, the behavior and capacity of gravity connections can significantly contribute to the integrity of steel-framed building structures. Because gravity connections are subjected to axial and flexural force demands and have a limited rotational capacity due to large beam rotations during a fire scenario, a connection model is needed to simulate their behavior when using analytical models to simulate the behavior of a steel structure in fire. This study develops a component model for shear tab connections at ambient and elevated temperatures in the opensource finite element program, OpenSees, to further enable the use of OpenSees for simulating steel structures in fire. Although the developed component model is not limited to implementation within OpenSees. The developed component model is benchmarked against experimental tests of isolated connections and a structural assembly with shear tab connections subjected to mechanical and thermal loads. Through benchmarking, it is shown that (1) the developed component model could be used to simulate connection behavior during a fire scenario and (2) simulating the ductility of connections and connecting components due to damage is critical when simulating the behavior of shear tab connections exposed to fire.

Performance Test of Hotong Seed Billing Machine (Setaria italica (L.) P. Beauv) Abrasive Roll Type with Grinding Stone

Indonesia has a lot of diversity, one of which is in food. Carbohydrates are basic food needs that must be met, in Indonesia there is the potential for various alternative foods. One of the alternative food ingredients producing carbohydrates is hotong. Hotong is a plant that is often found in Indonesia but has post-harvest constraints, namely in the sowing process. Therefore, research was conducted to determine the performance of an abrasive roll type grinding machine with the characteristics of hotong seeds. The research was conducted at PT. Daud Teknik Maju Pratama in November 2022. The treatment of hotong seeds that are sprayed as many as three passes with various levels of rpm speed, namely 806, 940, and 1128 rpm and carried out three repetitions at each rpm. The performance test results of the crushing machine showed the highest scattered capacity and shrinkage at a rotating speed of 1128 rpm, the highest yield and effectiveness of skin separation at a speed of 806 rpm, while at the highest polishing quality at a speed of 940 rpm. Rotating speed affects the sowing results, the faster the engine rotation speed, the quality and capacity of the sowing will increase. In addition, the tilt angle of the machine also affects the result of the sowing capacity. The terminal velocity value is influenced by the weight of the hotong seeds, the higher the weight on the sample, the higher the terminal velocity value obtained. Keywords: Abrasive Roll, Hotong, Polisher.

Exergoeconomic Analysis of a Direct Expansion Solar Assisted Heat Pump for Humid and Tropical Climates

A direct expansion solar assisted heat pump (DX-SAHP) is a heating water technology that convey a conventional solar heating system with a heat pump. This technology with great potential should overcome economics aspects to be available commercially soon. An exergoeconomic analysis of a DX-SAHP has been performed for three collector configurations and three compressor displacement capacity under the meteorological condition of Portoviejo city in Ecuador, a location with a tropical and humid climate. The present work is aimed to study the relationship between exergoeconomic data under various operations conditions. In addition, the exergy destruction, exergetic efficiency, cost rate per exergy unit product and fuel, cost rate associated to exergy destruction, exergoeconomic factor for each component of a DX-SAHP are evaluated. The exergoeconomic factor is found lowest for the solar collector for all the configurations, with estimated values of 5 to 21%. The component that needs more improvement for a tropical and humid climate is the solar collector based on exergoeconomic factor. On the basis of the present study, it can be concluded that a solar collector area of 1,5 m2 and a rotational displacement capacity of 1350 rpm performs better in all respects.

Experimental and numerical investigation of bolted steel endplate with bonded sleeve end connections for pultruded GFRP circular tubular hollow beams

The paper presents an experimental and numerical investigation of bolted steel endplates with bonded sleeve connections developed for connecting pultruded glass fibre-reinforced polymer (GFRP) circular tubular beams. The moment-rotational responses were investigated in detail in terms of initial rotational stiffness, moment capacity, and rotation capacity for all the connections. The effect of endplate thickness and bonded sleeve length was also investigated. Predominant failure modes include bending and yielding of thinner endplates, while thicker endplates with low bonded sleeve lengths exhibit splitting failure in the bonded GFRP beam region. Available design codes for steel joints were used to classify the developed connections in terms of rigidity and strength. The failure modes from the finite element models were well matched by the experimental observations, which include the deformation of the endplate and the cohesive failure within the bonded sleeve region with the GFRP beam.

Hysteretic and rotational performance study of outwardly extending shape-steelprefabricated beam-column joints

This paper proposes fully-bolted extending shape steel prefabricated beam-column joints to achieve rapid construction and reliable connection of the precast reinforced concrete frame. The prefabricated component uses steel tube-concrete composite structures with outwardly extended shape steel, which achieves efficient installation and internal force transfer. Horizontal hysteresis tests were conducted on four components to determine the joint mode of failure and seismic performance index. The results show that the joint exhibits a “double plastic” failure mode, with plastic deformation occurring at the end of the reinforced concrete beam and buckling deformation at the shaped steel. Compared to cast-in-place joints, the new joints have a 30% increase in yield load, a 51% increase in peak load, an approximately 50% increase in initial stiffness, a 33% increase in equivalent viscous damping coefficient, and a ductility coefficient greater than 4.0. Analysis of strain showed that the stiffness of the connection area was too high, which will have a significant extrusion effect on the concrete at the end. Reducing the thickness of the steel plate in the joint space and weakening the shape stee by opening holes can significantly improve the rotational deformation capacity of the joint - further developing the plastic zone of reinforced concrete beams to improve the mechanical performance of the joint. Finally, the finite element model of the joint is established, and the numerical calculation is in good agreement with the experimental results. The research in this paper can provide technical support for the engineering application of the prefabricated joint.

Experimental investigation of rigid khorjini connections using reduced beam sections with diagonal and horizontal-vertical stiffeners

Steel structures with khorjini beam–column connections, used to be a popular construction practice in Iran. This paper presents a new rigid khorjini connection with reduced beam sections (RBS) for earthquake-resistant steel structures. In rigid khorjini connection, two beams pass next to the column faces without interruption and are connected to the column by vertical plates. In this research, Rigid khorjini connections with Reduced beam sections were investigated. RBS method has some disadvantages such as web local buckling and lateral torsional buckling. Therefore, to prevent these weaknesses and improve the performance of khorjini connections with reduced beam sections, web stiffeners were employed. Four different specimens were constructed and tested using IPE 140 profiles for beams: one without an RBS (KHORJINI), one with reduced beam section (KRBS), and two with RBS and web stiffeners (KRBS-HVS and KRBS-DS). Through these experimental tests, it was revealed that all specimens sustained the interstory drift angle greater than 0.06 rad without any significant loss of strength, which indicates that the Rigid khorjini connection with reduced beam sections for IPE140 profiles can perform acceptably under the conditions of AISC regulations and the use of Diagonal and Horizontal-Vertical stiffeners increased the energy dissipation and plastic rotation capacity of connections.

Experimental studies on improving progressive collapse resistance of RC beam–column assemblies using kinked steel plates

One of the commonly applied methods to improve the progressive collapse resistance of reinforced concrete (RC) frame structures is to increase the amount of longitudinal rebars in beams. However, this method may lead to the unfavorable failure mode of “strong beam-weak column” for the RC frame structures under earthquakes. To prevent from this failure mode, a novel method is presented in this study using kinked steel plates (KPs) that were locally debonded and longitudinally embedded in the RC beams to improve the progressive collapse resistance of the RC frames. First, quasi-static loading tests were conducted on four 1/3 scale RC beam − column assemblies, including an equal-span specimen without the KPs, an equal-span specimen containing the KPs, an unequal-span specimen without the KPs, and an unequal-span specimen containing the KPs. Test results indicated that the ultimate resistance was improved by 89% and 81%, and the deformation capacities were increased by 39% and 38% for the equal-span and unequal-span beam − column assemblies containing the KPs compared to those without the KPs, respectively. Afterwards, high-fidelity finite element (FE) models were established to analyze the resistance contributions of the RC beam − column assemblies at the catenary action stage. Combining the experimental and FE analysis results, the mechanism was revealed for the RC beam − column assemblies using the KPs, i.e., the KPs could improve the ultimate rotational capacity of the beam-ends and induce the behavior of “two batches of plastic hinges”, resulting in fully mobilizing the catenary action to resist progressive collapse. Finally, an analytical model was developed to predict the ultimate resistance of the RC beam − column assemblies.

Enhancing the cyclic performance of shear links using longitudinal stiffeners

Shear links constitute the most crucial part of eccentrically braced frames. Their main responsibility is to dissipate the earthquake input energy away from the main structural members; therefore, keeping them responding within the elastic stage. However, the rotation capacity of vertical shear links directly influences the allowable interstorey drift of the eccentrically braced frame and the energy dissipation capacity. To enhance their rotation capacity and performance, transverse stiffeners in vertical shear links are proposed to be replaced with longitudinal stiffeners in this research. A numerical study is conducted, using Ansys Workbench, on fourteen shear links with different parameters to investigate their cyclic behaviour. The considered parameters are the stiffener configuration (transverse or longitudinal), web thickness, stiffeners number, stiffeners thickness, flanges width, and web aspect ratio. The influence of these parameters on the failure mode, hysteretic response, mechanical parameters (strength, rotation capacity, etc.), ductility, cyclic web shear buckling, and energy dissipation is analysed and discussed. The results demonstrate that longitudinally stiffened shear links surpass conventional transversely stiffened ones in terms of strength, overstrength, rotation capacity, ductility, web shear buckling resistance, and energy dissipation. Additionally, it is found that the current design provisions of EN 1998–1 cannot accurately predict the yield shear strength of longitudinally stiffened shear links. Moreover, numerous remarks involved with the influence of different parameters on the cyclic performance of longitudinally stiffened shear links are presented and discussed.

Failure analysis and retrofitting of reinforced concrete beams in existing moment resisting frames

During the structure lifetime, the design loads can modify because of a changing in the use destination. In common practice, any architectural change of existing buildings, which modifies the magnitude of loads, requires the evaluation of the load-carrying capacity of structural members. To this aim a nonlinear analysis considering the rotation capacity of critical regions until the failure of the structure can be advantageous compared to a simple elastic analysis. Plastic deformations of ductile elements allow for attaining a more accurate evaluation of the ultimate load, once the strength of brittle mechanisms has been averted. Exploiting the actual rotation capacity of critical regions, where plastic hinges form, this paper presents new analytical closed-form equations to evaluate the ultimate load and the failure mode of an interior span of a multi-span moment resisting frame, as impacted by the strength of beam–column joints and the elastic and post-elastic structural response of adjacent elements. Taking advantage of derived equations, a retrofitting design procedure to identify the proper structural strengthening of critical regions is proposed. The accuracy of the method is checked through a comparison with numerical results. The procedure represents a new useful tool for engineers for the local strengthening of existing reinforced concrete buildings.