• Steel and Composite Structures
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• 제37권3호
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• pp.371-390
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• 2020

One of the most common strategies for retrofitting as-built reinforced concrete (RC) columns is to enlarge the existing section through the application of a new concrete layer reinforced by both steel transverse and longitudinal reinforcements. The present study was dedicated to developing a comprehensive model to predict the seismic behavior of as-built RC jacketed columns. For this purpose, a new sectional model was developed to perform moment-curvature analysis coupled by the plastic hinge method. In this analysis-oriented model, new methodologies were suggested to address the impacts of axial, flexural and shear mechanisms, variable confining pressure, eccentric loading, longitudinal bar buckling, and varying axial load. To consider the effective interaction between core and jacket, the monolithic factor approach was adopted to extent the response of the monolithic columns to that of a respective RC jacket strengthened column. Next, parametric studies were implemented to examine the effectiveness of the main parameters of the RC jacket strategy in retrofitting as-built RC columns. Ultimately, the reliability of the developed analytical model was validated against a series of experimental results of as-built and retrofitted RC columns.

• Earthquakes and Structures
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• 제8권2호
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• pp.463-484
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• 2015

Modern codes for earthquake resistant building design require consideration of the so-called accidental design eccentricity, to account for torsional response caused by several factors not explicitly considered in design. This provision requires that the mass centres in the building floor be moved a certain percentage of the building's dimension (usually 5%) along both the x and y axes and in both positive and negative directions. If one considers also the spatial combinations of the two component motion in a dynamic analysis of the building, the number of required analyses and combinations increases substantially, causing a corresponding work load increase for practicing structural engineers. Another shortcoming of this code provision is that its introduction has been based primarily on elastic results from investigations of oversimplified, hence questionable, one story building models. This problem is addressed in the present paper using four groups of eccentric braced steel buildings, designed in accordance with Eurocodes 3 (steel) and 8 (earthquake design), with and without accidental eccentricities considered. The results indicate that although accidental design eccentricities can lead to somewhat reduced inelastic response demands, the benefit is not significant from a practical point of view. This leads to suggestions that accidental design eccentricities should probably be abolished or perhaps replaced by a simpler and more effective design provision, at least for torsionally stiff buildings that constitute the vast majority of buildings encountered in practice.

• 대한세포병리학회지
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• 제12권1호
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• pp.45-48
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• 2001

Acinic cell carcinoma(ACC) is the third common malignancy in major salivary gland. Fine needle aspiration cytology is a useful tool for the diagnosis of salivary gland lesions. However, some low grade malignancies, such as ACC and mucoepidermoid carcinoma show relatively high false negative rate, mainly due to deceptively benign cytomorphologic appearance. We experienced a papillary-cystic variant of ACC, having different cytopathologic features compared with those of classic ACC. Our case showed monolayered sheets and papillary clusters without any acinic structures or naked nuclei of the tumor cells. Foamy proteinaceous material was seen in the background. The tumor cells had a large amount of granular cytoplasm and eccentric nuclei. Many vacuolated or clear cells were also noted.

• 대한세포병리학회지
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• 제9권1호
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• pp.99-104
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• 1998

Anaplastic large cell lymphoma(ALCL) is an uncommon type of non-Hodgkin's lymphoma(NHL) populated with anaplastic, often bizarre cells that express CD30 (Ki-1) antigen. The unusual histologic and cytologic features may cause confusion with other neoplasms, such as poorly differentiated carcinoma, melanoma, Hodgkin's disease, or true histiocytic lymphoma. Although the cytologic features of ALCL have been well described, there are few reports about cytologic findings of the sarcomatold variant of ALCL. We experienced a case of fine needle aspiration(FNA) cytologic findings of ALCL which mimicks malignant fibrous histiocytoma. FNA cytology of chest wall mass in a 62-year-old female with a history of peripheral T-cell lymphoma(Lennert lymphoma) revealed a heterogeneous population of single cells and poorly cohesive cells with large, pleomorphic nuclei and spindle cells gathering around vascular structures within an inflammatory background. Additional features of the neoplastic cells were eccentric, multilobated nuclei with occasional 'wreath-like' configuration; abundant cytoplasm with vacuolization; and prominent nucleoli. The cytologic features suggested sarcoma, especially malignant fibrous histiocytoma. The diagnosis was made retrospectively with an aid of immunocytochemical staining.

• Steel and Composite Structures
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• 제14권2호
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• pp.173-190
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• 2013

The major objective of this paper is to evaluate the behavior and ultimate resisting capacity of circular CFT columns. To consider the confinement effect, proper material models with respect to the confinement pressure are selected. A fiber section approach is adopted to simulate the nonlinear stress distribution along the section depth. Material nonlinearity due to the cracking of concrete and the yielding of the surrounding steel tube, as well as geometric nonlinearity due to the P-${\Delta}$ effect, are taken into account. The validity of the proposed numerical analysis model is established by comparing the analytical predictions with the results from previous experimental studies about pure bending and eccentric axial loading. Numerical predictions using an unconfined material model were also compared to investigate the confinement effects on various loading combinations. The ultimate resisting capacities predicted by the proposed numerical model and the design guidelines in Eurocode 4 are compared to evaluate the existing design recommendation.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.393-406
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• 2016

Axially loaded reinforced concrete columns are hardly exist in practice due to the development of some bending moments. These moments could be produced by gravity loads or the lateral loads. First, the current paper presents a detailed analysis on the overall structural behavior of 15 eccentrically loaded columns as well as one concentrically loaded control one. Columns bent in either single curvature or double curvature modes are tested experimentally up to failure under the effect of different end eccentricities combinations. Three end eccentricities ratio were studied, namely, 0.1b, 0.3b and 0.5b, where b is the column width. Second, an expression correlated the decay in the normalized axial capacity of the column and the acting end eccentricities was developed based on the experimental results and then verified against the available formula. Third, based on the equivalent column concept, the equivalent pin-ended columns were obtained for columns bent in either single or double curvature modes. And then, the effect of end eccentricity ratio was correlated to the equivalent column length. Finally, a simplified design procedure was proposed for eccentrically loaded braced column by transferring it to an equivalent axially loaded pin-ended slender column. The results of the proposed design procedure showed comparable results against the results of the ACI 318-14 code.

• Steel and Composite Structures
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• 제5권1호
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• pp.35-47
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• 2005

This paper presents the results of a series of tests carried out on hollow and concrete-filled coldformed steel sections subjected to axial and bending forces. The effects of eccentricity ratio and strength of in-fill on the behaviour of these sections were studied. A total of forty-eight medium sized columns and six beams were tested to failure. Extensive measurements of material properties, strains, axial shortening and lateral deflection were carried out. Interaction of local and overall buckling was observed in the tests. Failure mode observations were local buckling coupled with overall buckling. A description of the specially fabricated end fixtures for applying eccentric loading to the columns and to simulate pinned end condition is also presented. The experimental results of hollow columns are compared with the existing Indian, British and American codes of practice and the results of concrete-filled columns are compared with EC4 recommendations. It is seen that in the case of hollow columns predictions based on British and American codes of practice and in the case of concrete-filled columns predictions based on EC4 recommendations agree reasonably well with the experimental results. From the experiments it is seen that the provision of in-fill substantially increases the ultimate load carrying capacity of the order of one and a half to two times and the increase in strength of the in-filled concrete from a low grade concrete of compressive strength 24.94 MPa to a high grade concrete of compressive strength 33.26 MPa increases the ultimate load carrying capacity by one and a half times irrespective of the eccentricity of loading.

• Structural Monitoring and Maintenance
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• 제3권2호
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• pp.175-194
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• 2016

Based on the change of traditional viscoelastic damper structure, a brand-new damper is designed to control simultaneously the translational vibration and the rotational vibration for platforms. Experimental study has been carried out on the mechanical properties of viscoelastic material and on its multi-dimensional seismic response control effect of viscoelastic damper. Three types of viscoelastic dampers with different shapes of viscoelastic material are designed to test the influence of excited frequency, strain amplitude and ambient temperature on the mechanical property parameters such as circular dissipation per unit, equivalent stiffness, loss factor and storage shear modulus. Then, shaking table tests are done on a group of single-storey platform systems containing one symmetric platform and three asymmetric platforms with different eccentric forms. Experimental results show that the simulation precision of the restoring force model is rather good for the shear deformation of viscoelastic damper and is also satisfied for the torsion deformation and combined deformations of viscoelastic damper. The shaking table tests have verified that the new-type viscoelastic damper is capable of mitigating the multi-dimensional seismic response of offshore platform.

• Steel and Composite Structures
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• 제16권1호
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• pp.97-114
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• 2014

This paper deals with a study on ultimate strength behaviour of eccentrically loaded CFT columns with and without shear connectors. Thirty specimens are subjected to experimental investigation under eccentric loading condition. P-M curves are generated for all the test specimens and critical eccentricities are evaluated. Three different D/t ratios such as 21, 25 and 29 and L/D ratios varying from 5 to 20 are considered as experimental parameters. Six specimens of bare steel tubes as reference specimens, twelve specimens of CFT columns without shear connectors and twelve specimens of CFT columns with shear connectors, in total thirty specimens are tested. The P-M values at the ultimate failure load of experimental study are found to be well agreed with the results of the proposed P-M interaction model. The load-deflection and load-strain behaviour of the experimental column specimens are presented. The behaviour of the CFT columns with and without shear connectors is compared. Experimental results indicate that the percentage increase in load carrying capacity of CFT columns with shear connectors compared to the ordinary CFT columns is found to be insignificant with a value ranging from 6% to 13%. However, the ductility factor of columns with shear connectors exhibit higher values than that of the CFT columns without shear connectors. This paper presents the proposed P-M interaction model and experimental results under varying parameters such as D/t and L/D ratios.

• Applied Microscopy
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• 제17권1호
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• pp.169-176
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• 1987

Naturally occurring canine transmissible venereal tumors of genital organs in mature and regressive stages from 6 dogs were examined by transmission electron microscope. The tumor cells at the stage of maturation were comprised of large round and ovoid cells with prominent nuclei and nucleoli, a few spindle-shaped cells, and irregularly shaped cells. The mature round cells were characterized by the presence of a central ovoid to irregularly round nucleus with a large eccentric nucleolus, vesicular endoplasmic reticulum, round to oval swollen mitochondria with few cristae, Golgi's apparatus, and plasma membranes with numerous microvilli. As the tumor degenerated, the tumor cells were increased in the number of spindle-shaped, fibroblast-like and irregularly shaped cells, collagen bundles, and mainly lymphocytes, in contrast to those of the stage of maturation. Regressing tumor cells were characterized by the swelling and vacuolation of mitochondria and endoplasmic reticulum, membrane-bound granules, lamellar complex, tubular structures, and dense bundles of collagen. It was suggested that transformation might occur in the course of tumor growth causing morphological change from the round to the fibroblast-like cells, and that there was the evidence of cell-mediated tumor cell lysis by lymphocyte infiltration.