• Steel and Composite Structures
• /
• v.39 no.4
• /
• pp.383-399
• /
• 2021

In the study, three 1:3-scale unequal span steel-concrete composite substructures with top-seat angle and double web angle connection were designed and identified as specimens GTSDWA-0.6, GTSDWA-1.0, and GTSDWA-1.4. Pseudo-static tests and refined numerical model analysis were conducted to examine the anti-progressive collapse performance of a semi-rigid steel-concrete composite substructure. The results indicated that the failure modes of the three specimens revealed that the fracture occurred in the root of the long leg of the top/seat angle in tension at the connection. With increases in the span ratio of the left and right composite beams, the bearing capacities of the composite substructures decreased, and the corresponding displacement increased. With respect to GTSDWA-0.6 and GTSDWA-1.4, the resistance due to the short composite beam corresponded to 62% and 60%, respectively, and the total resistance provided by the short composite beam exceeded that of the long composite beam. With respect to GTSDWA-1.0, the resistance due to the left and right composite beams was similar. All three specimens underwent the flexure mechanism and flexure-axial mixed mechanism stages. They resisted the external load mainly via the flexure mechanism. Moreover, the addition of stiffeners on both sides of the top and seat angles is advantageous in terms of improving the collapse resistance and ductility of unequal span composite substructures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.59-66
• /
• 2020

Two octagonal RC bridge columns of small scale model were tested under cyclic lateral load with constant axial load. One in two specimens was solid cross section, the other was hollow cross section. The volumetric ratio of transverse spiral hoop of all specimens is 0.00206. The columns showed flexure-shear failure. Failure behavior and seismic performance were investigated. The test results showed that the structural performance of the hollow specimen such as initial crack pattern, initial stiffness, and energy dissipation performance was comparable to that of the solid specimen, but the lateral strength, ultimate displacement, energy dissipation performance of hollow specimen noticeably decreased after drift ratio of 3%.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.7
• /
• pp.127-133
• /
• 2009

We present a $3-{\underline{P}}RS$ compliant parallel manipulator actuated by PZTs. The motion ranges are $400-{\mu}m$ translation to the z-direction and 5.7-mrad rotation about any axis on the x-y plane. A mechanical amplifier whose advantage is approximately 5.5 is designed and integrated with flexure revolute and spherical joints in a monolithic way. We evaluated the performance of the system: kinematic and dynamic characteristics. In kinematic point of view, the flexures play the roles of conventional mechanism but any nonlinearity such as dead-zone and backlash, which make it possible to achieve the steady-state resolution less than $0.1{\mu}m$. The system shows resonance near 86 Hz with high magnitude and, therefore, poor transient response. But the settling is faster when the flexures are strained higher.

• Steel and Composite Structures
• /
• v.26 no.4
• /
• pp.407-420
• /
• 2018

Experiments were performed to explore the hysteretic performance of steel reinforced concrete (SRC) cross-shaped columns. Nine specimens were designed and tested under the combined action of compression, flexure, shear and torsion. Torsion-bending ratio (i.e., 0, 0.14, 0.21) and steel forms (i.e., Solid - web steel, T - shaped steel, Channel steel) were considered in the test. Both failure processes and modes were obtained during the whole loading procedure. Based on experimental data, seismic indexes, such as bearing capacity, ductility and energy dissipation were investigated in detail. Experimental results suggest that depending on the torsion-bending ratio, failure modes of SRC cross-shaped columns are bending failure, flexure-torsion failure and torsion-shear failure. Shear - displacement hysteretic loops are fuller than torque - twist angle hysteretic curves. SRC cross-shaped columns exhibit good ductility and deformation capacity. In the range of test parameters, the existence of torque does not reduce the shear force but it reduces the displacement and bending energy dissipation capacity. What is more, the bending energy dissipation capacity increases with the rising of displacement level, while the torsion energy dissipation capacity decreases.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.6
• /
• pp.756-760
• /
• 2011

This paper proposed an alignment stage driven by piezo actuators for alignment process of a contact-type lithography. Among contact-type lithography processes, an UV-curable nanoimprint process is an unique process to be able to align patterns on upper and lower layers. An alignment stage of the UV-curable nanoimprint process requires nano-level resolution as well as high stiffness to overcome friction force due to contact moving. In this paper, the alignment stage consists of a compliant mechanism using flexure hinges, piezo actuators for high force generation, and capacitive sensors for high-resolution measurement. The compliant mechanism is implemented by four prismatic-prismatic compliant chains for two degree-of-freedom translations. The compliant mechanism is composed of flexure hinges with high stiffness, and it is directly actuated by the piezo actuators which increases the stiffness of the mechanism, also. The performance of the ultra-precision stage is demonstrated by experiments.

• Earthquakes and Structures
• /
• v.16 no.1
• /
• pp.41-54
• /
• 2019

Reinforced Concrete (RC) shear walls are widely used in Nuclear power plants as effective lateral force resisting elements of the structure and these may experience nonlinear behavior for higher earthquake demand. Short shear walls of aspect ratio less than 1.5 generally experience combined shear flexure interaction. This paper presents the results of the displacement-controlled experiments performed on six RC short shear walls with varying aspect ratios (1, 1.25 and 1.5) for monotonic and reversed quasi-static cyclic loading. Simulation of the shear walls is then carried out by Finite element modeling and also by macro modeling considering the coupled shear and flexure behaviour. The shear response is estimated by softened truss theory using the concrete model given by Vecchio and Collins (1994) with a modification in softening part of the model and flexure response is estimated using moment curvature relationship. The accuracy of modeling is validated by comparing the simulated response with experimental one. Moreover, based on the experimental work a multi-linear hysteretic model is proposed for short shear walls. Finally ultimate load, drift, ductility, stiffness reduction and failure pattern of the shear walls are studied in details and hysteretic energy dissipation along with damage index are evaluated.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1860-1863
• /
• 1997

Transfer alignement is the process of initializing attitude of slave INS using the data of master INS. This paper presents the performance analysis of transfer alignment at sea using convariance analysis method. Velocity & angle matching and angular rate & acceleration matching are used for analysis, and the performance of two matching methods are compared. We propose a new method for angular rate & acceleration matching. Under the assumption of accurate modeling of ship flexure, the performance of transfer alignment time and accuray is improved very much for the new method.

• Journal of Korean Society of Steel Construction
• /
• v.21 no.4
• /
• pp.403-411
• /
• 2009

In the present study, nonlinear earthquake analysis was carried out for a steel girder bridge that had been damaged by the 1995 Kobe earthquake. For such analysis, the use of hysteretic models describing flexure-axial and shear-axial interaction was suggested. The models were incorporated into a structural analysis program in terms of the joint elements representing hinge models, and then a simplified analysis scheme using the hinge models was employed for bridge piers. The analytical predictions of the flexure-axial interactive hinge model show a good correlation with those of the detailed fiber element model. In addition, the analytical predictions of the flexure-shear-axial interactive hinge model enable a displacement component to be separately captured. It is thus recognized that the present study can be a useful scheme for the healthy evaluation of the global displacement performance of piers subjected to earthquake excitation.

• Journal of the Korea Concrete Institute
• /
• v.21 no.4
• /
• pp.523-530
• /
• 2009

For designing concrete structures, engineers are provided data from unidirectional flexure test in most cases. But real structural components such as pavements and deck panel are subjected to multiaxial stress throughout their body. Therefore, biaxial flexure test for concrete may be considered as a gage of the performance of concrete in service. In this paper, we propose the optimum biaixial flexture test (BFT) to measure the biaxial flexural strength of concrete. This method are an improved version of the ring-on-ring test which have been used extensively in the fields of ceramics and biomaterials. The optimum geometry of the test specimen was determined by using a three-dimensional finite element analysis. A series of test data obtained from the proposed test method is provided to show that the proposed optimum biaxial flexure test method can be used to identify the biaxial tensile strength of concrete.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.2 s.48
• /
• pp.1-10
• /
• 2006

Reinforced concrete bridge columns with relatively small aspect ratio show flexure-shear behavior, which is flexural behavior at initial and medium displacement stages and shear failure at final stage. Since the columns with flexure-shear failure have lower ductility than those with flexural failure, shear capacity curve models shall be applied as well as flexural capacity curve in order to determine ultimate displacement for seismic design or performance evaluation. In this paper, a modified shear capacity curve model is proposed and compared with the other models such as the CALTRANS model, Aschheim et al.'s model, and Priestley et al.'s model. Four shear capacity curve models are applied to the 4 full scale circular bridge column test results and the accuracy of each model is discussed. It may not be fully adequate to drive a final decision from the application to the limited number of test results, however the proposed model provides the better prediction of failure mode and ultimate displacement than the other models for the selected column test results.