• Computers and Concrete
• /
• v.34 no.1
• /
• pp.49-61
• /
• 2024

The present study concerns a removal of chloride ions and structural behaviour of concrete beam at electrochemical chloride extraction (ECE). The electrochemical properties included 1000 mA/m2 current density for 2, 4 and 8 weeks. It was found that an increase in the duration of ECE resulted in an increase in the extraction rate of chlorides, in the range of 35-85%, irrespective of chloride contamination. In structural behaviour, the strength and maximum bending moment of specimen was always lowered by ECE. Moreover, the flexural rigidity and bending stiffness were reduced by the loss of effective cross-section area in the linear elastic range. Simultaneously, the inertia moment was substantially subjected to 70% loss of the cross-section by the tensile strain at the condition of the failure. However, a lower rate of the inertia moment reduction was achieved by ECE, implying the higher resistance to the cracking, but the higher risk of deformation.

• Computational Structural Engineering
• /
• v.9 no.4
• /
• pp.135-140
• /
• 1996

Single angle or channel with thin-walled open section can be used as compression member for example as web member in truss. In this case the inevitable eccentricity due to fabrication is commonly neglected in structural design. However eccentricity effect should be considered in the member design, especially in case of compression member. The critical loads of compression members that buckle by twisting or by a combination of bending and twisting are to be determined by solving governing differential equations. In this paper, the investigations are limited to the rolled channels([), equal-leg angles(L), lipped channels(C) and the applied loads are assumed to have some eccentricities.

• Wind and Structures
• /
• v.11 no.2
• /
• pp.153-178
• /
• 2008

Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.

• Steel and Composite Structures
• /
• v.33 no.5
• /
• pp.755-765
• /
• 2019

This study examined geometric and physical nonlinear analyses of beams and arches specifically from rolled profiles used in mining and underground constructions. These profiles possess the ability to create plastic hinges owing to their robustness. It was assumed that displacements in beams and arches fabricated from these profiles were comparable with the size of the structure. It also considered changes in the shape of a rod cross-section and the nonlinearities of the structure. The analyses were based on virtual unit moments, effective flexural rigidity of used open sections, and a secant method. The use of the approach led to a solution for the "after-critical" condition in which deformation increased with decreases in loads. The solution was derived for static determinate beams and static indeterminate arches. The results were compared with results obtained in other experimental tests and methods.

• International Journal of High-Rise Buildings
• /
• v.7 no.3
• /
• pp.255-264
• /
• 2018

This paper introduces three distinctive means for the use of a 189-meter high damped structure ensuring safety against earthquake: 1. Realization of L-shaped elevational structural planning: The bottom and top of the tower have belt trusses and hat trusses respectively to restrain the bending deformation. Furthermore, large-capacity oil dampers (damping force 6,000 kN) are installed in the middle part of the tower to restrain the higher-mode deformation. 2. Realization of L-shaped planar structural planning: We devised a means of matching the centers of gravity and rigidity by adjusting planar rigidity. Moreover, viscous damping devices are located at the edges of the L-shaped plan, where torsional deformation tends to be amplified. We call this the "Damping Tail" system. 3. Composite foundation to equalize deformations under different loading conditions: We studied the vertical and horizontal deformations using sway-rocking and 3D FEM models including the ground, and applied multi-stage diameter-enlarged piles to the tower and a mat foundation to the podium to keep the foundations from torsional deformations and ensure structural safety.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.11
• /
• pp.95-99
• /
• 2008

Applications of composite materials in various engineering fields have been extended significantly. For being useful composite materials, we could modify the rigidity and strength characteristics of composite material according to structures and material direction. In this study, CFRP, which has been widely used in space leisure and general structural applications due to the weight, elasticity coefficient, high fatigue strength and lower thermal transformation ect, was selected. As the CFRP is an anisotropic material whose mechanical properties change with its stacking sequence or angle, special attention was given to the effects of the fiber orientation angle on the bending characteristics of CFRP fiat and CFEP square members. It's different on the each result of strength and rigidity of CFRP flat and CFRP square members.

• Advances in Computational Design
• /
• v.4 no.4
• /
• pp.327-342
• /
• 2019

Rehabilitation and retrofitting of structures designed in accordance to standard design codes is an essential practice in structural engineering and design. For steel structures, one of the challenges is to strengthen the panel zone as well as its analysis in moment-resisting frames. In this research, investigations were undertaken to analyze the influence of the panel zone in the response of structural frames through a computational approach using ETABS software. Moment-resisting frames of six stories were studied in supposition of real panel zone, different values of rigid zone factor, different thickness of double plates, and both double plates and rigid zone factor together. The frames were analyzed, designed and validated in accordance to Iranian steel building code. The results of drift values for six stories building models were plotted. After verifying and comparing the results, the findings showed that the rigidity lead to reduction in drifts of frames and also as a result, lower rigidity will be used for high rise building and higher rigidity will be used for low rise building. In frames with story drifts more than the permitted rate, where the frames are considered as the weaker panel zone area, the story drifts can be limited by strengthening the panel zone with double plates. It should be noted that higher thickness of double plates and higher rigidity of panel zone will result in enhancement of the non-linear deformation rates in beam elements. The resulting deformations of the panel zone due to this modification can have significant influence on the elastic and inelastic behavior of the frames.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.728-733
• /
• 2001

The subject of this paper is to perform the basic research to make design guide as finding out the structural characteristics of polypropylene Ankle Foot Orthosis(AFO) for hemiplegics. Target shape of AFO is a solid standard type. In this study we measure ridity as dorsiflexion and thicknesses of AFO with three types of ankle widths and analyze correlation between rigidity and ankle widths, thicknesses. As a result, the rigidity characteristic is specified complex effect of ankle widths and thicknesses.

• International Journal of Concrete Structures and Materials
• /
• v.11 no.1
• /
• pp.45-58
• /
• 2017

Recent investigations have pointed out that current code provisions specifying that the stiffness of reinforced concrete elements is strength independent, and therefore can be estimated prior to any strength assignment, is incorrect. A strength allocation strategy, suitable for preliminary structural design of medium height wall-frame dual systems, is presented for allocating strength in such buildings and estimating the dependable rigidities. The design process may be implemented by either the approximate continuous approach or the stiffness matrix method. It is based on the concept of the inelastic equivalent single-degree-of-freedom system which, the last few years, has been used to implement the performance based seismic design. The aforesaid strategy may also be used to determine structural configurations of minimum rotation distortion. It is shown that when the location of the modal centre of rigidity, as described in author's recent papers, is within a close distance from the mass axis the torsional response is mitigated. The methodology is illustrated in ten story building configurations, whose torsional response is examined under the ground motion of Kobe 1995, component KJM000.

• Journal of the Korean Wood Science and Technology
• /
• v.19 no.2
• /
• pp.40-55
• /
• 1991

To investigate the influence of cross section geometries on the behavior of composite beams in the case of small span to depth ratio and deep beams. the static flexural behavior of composite I-beams and Box- beams was evaluated. 12 types of composite I -beams composed of LVL flanges and particleboard or plywood web and 3 types of composite Box-beams composed of LVL flanges and plywood web were tested under one-point loading. The load-deflection curves were almost linear to failure, therefore, the behavior of tested composite beams was elastic. The theoretical flexural rigidity of composite beams was calculated and compared with observed flexural rigidity. The highest value was found in I-W type beams and the lowest value was found in G-P type beams. The difference between theoretical and observed flexural rigidity was small. Theoretical total deflection of tested composite beams was calculated using flexural rigidity and compared with actual deflection. Shear deflection of these beams was evaluated by the approximation method, solid crosss section method and elementary method. The difference between actual deflection and expected deflection was not found in D, E and F type beams. This defference was small in G, H and I type beams or Box-beam.