• Steel and Composite Structures
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• v.30 no.2
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• pp.123-140
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• 2019

This paper presents experimental study on effects of width-to-thickness ratio and loading history on cyclic rotational capacity of H-shaped steel beams subjected to pure bending. Eight Class 3 and 4 H-shaped beams with large width-to-thickness ratios were tested under four different loading histories. The coupling effect of local buckling and cracking on cyclic rotational capacity of the specimens was investigated. It was found that loss of the load-carrying capacity was mainly induced by local buckling, and ductile cracking was a secondary factor. The width-to-thickness ratio plays a dominant effect on the cyclic rotational capacity, and the loading history also plays an important role. The cyclic rotational capacity can decrease significantly due to premature elasto-plastic local buckling induced by a number of preceding plastic reversals with relative small strain amplitudes. This result is mainly correlated with the decreasing tangent modulus of the structural steel under cyclic plastic loading. In addition, a theoretical approach to evaluate the cyclic rotational capacity of H-shaped beams with different width-to-thickness ratios was also proposed, which compares well with the experimental results.

• Steel and Composite Structures
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• v.23 no.1
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• pp.53-66
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• 2017

Structures submitted to Fire-After-Earthquake loading situations, are first experiencing inelastic deformations due to the seismic action and are then submitted to the thermal loading. This means that in the case of steel framed structures, at the starting point of the fire, plastic hinges have already been formed at the ends of the beams. The basic objective of this paper is the evaluation of the rotational capacity of steel I-section beams damaged due to prior earthquake loading, at increased temperatures. The study is conducted numerically and three-dimensional models are used in order to capture accurately the nonlinear behaviour of the steel beams. Different levels of earthquake-induced damage are examined in order to study the effect of the initial state of damage to the temperature-evolution of the rotational capacity. The study starts with the reference case where the beam is undamaged and in the sequel cyclic loading patterns are taken into account, which represent earthquakes loads of increasing magnitude. Additionally, the study extends to the evaluation of the ultimate plastic rotation of the steel beams which corresponds to the point where the rotational capacity of the beam is exhausted. The aforementioned value of rotation can be used as a criterion for the determination of the fire-resistance time of the structure in case of Fire-After-Earthquake situations.

• Structural Engineering and Mechanics
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• v.49 no.2
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• pp.147-161
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• 2014

In this paper a nonlinear finite element analysis model is established for cold-formed steel zed-section purlins subjected to uplift loading. In the model, the lateral and rotational restraints provided by the sheeting to the purlin are simplified as a lateral rigid restraint imposed at the upper flange-web junction and a rotational spring restraint applied at the mid of the upper flange where the sheeting is fixed. The analyses are performed by considering both geometrical and material nonlinearities. The influences of the rotational spring stiffness and initial geometrical imperfections on the uplift loading capacity of the purlin are investigated numerically. It is found that the rotational spring stiffness has significant influence on the purlin performance. However, the influence of the initial geometric imperfections on the purlin performance is found only in purlins of medium or long length with no or low rotational spring stiffness.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.37-41
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• 2011

This paper presents the capacity-control characteristics in an industrial cooler with a variable speed compressor. The inverter-type compressor is controlled by the rotational speed of the operational frequency. This type of the compressor performs the wide range of load compared to the on-off type. When the load of the system reduces, the rotational speed will be reduced. Thus, the system leads to the less power consumption and extends the longer durability of the compressor. With the variable rotational speed of the compressor the cooling capacity of the cooler is about 1.6-3.6 kW and the capacity control is about 40-100%. The system showed the highest efficiency when the rotational speed is about 45-70 Hz. The results can be used as the basic design data to control an industrial cooler.

• Earthquakes and Structures
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• v.8 no.3
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• pp.591-617
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• 2015

Standards for seismic assessment and retrofitting of buildings provide deformation limit states for structural members and connections. However, in order to perform fully consistent performance-based seismic analyses of soil-structure systems; deformation limit states must also be available for foundations that are vulnerable to nonlinear actions. Because such limit states have never been established in the past, a laboratory testing program was conducted to study the rotational capacity of small-scale foundation models under combined axial load and moment. Fourteen displacement-controlled monotonic and cyclic tests were performed using a cohesionless soil contained in a $2.0{\times}2.0{\times}1.2m$ container box. It was found that the foundation models exhibited a stable hysteretic behavior for imposed rotations exceeding 0.06 rad and that the measured foundation moment capacity complied well with Meyerhof's equivalent width concept. Simplified code-based soil-structure analyses of an 8-story building under an array of strong ground motions were also conducted to preliminary evaluate the implication of finite rotational capacity of vulnerable foundations. It was found that for the same soil as that of the experimental program foundations would have a deformation capacity that far exceeds the imposed rotational demands under the lateral load resisting members so yielding of the soil may constitute a reliable source of energy dissipation for the system.

• Steel and Composite Structures
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• v.46 no.3
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• pp.417-433
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• 2023

The maximum ductility and cumulative ductility of connection joints of Buckling-Restrained Braced Frames (BRBF) are critical to the structural overall performance, which should be matched with the BRB ductility. The two-story and one-span BRBF with a one-third scale was tested under cyclic quasi-static loading, and the top-flange beam splice (TFBS) rotational connections were proposed and adopted in BRBF. The deformation capacity of TFBS connections was observed during the test, and the relationship between structural global ductility and local connection ductility was studied. The rotational capacity of the beam-column connections and the stability performance of the BRBs are highly relevant to the structural overall performance. The hysteretic curves of BRBF are stable and full under large displacement demand imposed up to 2% story drift, and energy is dissipated as the large plastic deformation developed in the structural components. The BRBs acted as fuses and yielded first, and the cumulative plastic ductility (CPD) of BRBs is 972.6 of the second floor and 439.7 of the first floor, indicating the excellent energy dissipation capacity of BRBs. Structural members with good local ductility ensure the large global ductility of BRBF. The ductile capacity and hysteretic behavior of BRBF with TFBS connections were compared with those of BRBF with Reduced Beam Section (RBS) connections in terms of the experimental results.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.6
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• pp.353-360
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• 2018

This paper is to investigate the micro-behavior of the double-span beams with WUF-W seismic connection under combined axial tension and moment and to propose the rational rotational capacity of it for progressive collapse-resistant analysis and design addressing the stress and strain transfer mechanism. To this end, the behavior of the double-span beams under the column missing event is first investigated using the advanced nonlinear finite element analysis. The characteristics of fracture indices of double-span beams with WUF-W connection under combined axial tension and flexural moment are addressed and then proposed the rational rotational capacity as the basic datum for the progressive collapse-resistant design and analysis. The distribution of fracture indices related to stress and strain for the double-span beams is investigated based on a material and geometric nonlinear finite element analysis. Furthermore, the micro-behavior for earthquake and progressive collapse is explicitly different.

• Structural Engineering and Mechanics
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• v.10 no.1
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• pp.27-36
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• 2000

The Oktalok nodal connection system is an aesthetic and efficient system. It has been widely used throughout Australia. The paper will briefly introduce the concept and application of the Oktalok nodal system. The existing design method is based on the assumption that the joints are pin-ended, i.e., the rotational stiffness of the joints is zero. However the ultimate capacity of the frame may increase significantly depending on the rotational stiffness of the joints. Stiffness tests and finite element simulations were carried out to determine the rotational stiffness of the Oktalok joints. Column buckling tests and non-linear finite element analyses were performed to determine the member capacity of columns with semi-rigid end conditions. A simple formulae for the effective length factor of column buckling is derived based on the above experimental and theoretical investigations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2646-2653
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• 1993

A rotational torque calibration system is developed to measure rotational torque of power generating systems and to calibrate non-contact rotational torque measurement systems. The maximum capacity of the developed system is 4.5 N-m. It is composed of a DC motor, a DC generator, a control system, a master torque cell, a slip ling/brush set, supporters, a bed etc. The control system is characterized by the closed-loop control with differential intergrator. Rotational torque measurement test and unit response test are conducted to estimate the accuracy of the developed system. It is found that system maintain high consistency and accuracy with the maximum error of 0.25%, Therefore the developed system can be used to measure the rotational torque of power generating systems and to calibrate non-contact rotational torque measurement systems.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.348-354
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• 2003

This study outlines the analysis of toggle system and the vibration control performance when the toggle-rotational inertia damper system was applied to a structure. Numerical analysis shows that the relative displacement of the structure can be amplified by amplification mechanism of the toggle system and the capacity of the damper can be reduced without the loss of vibration control performance. It is also observed that vibration control effects is caused by the increase of equivalent mass due to the rotational inertia of damper.