• Wind and Structures
• /
• v.31 no.5
• /
• pp.459-472
• /
• 2020

This study focused on the non-synoptic, tornado-like wind-induced effects on flexible horizontal structures that are extremely sensitive to winds. More specifically, the nonuniform, intensive vertical wind-velocity and transient natures of tornado events and their effects on the global behavior of a long-span bridge were investigated. In addition to the static part in the modeling of tornado-like wind-induced loads, the motion-induced effects were modeled using the semi-empirical model with a two-dimensional (2-D) indicial response function. Both nonlinear wind-induced static analysis and linear aeroelastic analysis in the time domain were conducted based on a 3-D finite-element model to investigate the bridge performance under the most unfavorable tornado pattern considering wind-structure interactions. The results from the present study highlighted the important effects due to abovementioned tornado natures (i.e., nonuniform, intensive vertical wind-velocity and transient features) on the long-span bridge, and hence may facilitate more appropriate wind design of flexible horizontal structures in the tornado-prone areas.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.43 no.4
• /
• pp.89-96
• /
• 2001

In this study non-linear finite element analysis of dynamic response of steel arch under partially distributed dynamic load was discussed. Material and geometric non-linearities were included in finite element formulation and steel behavior was modeled with Von Mises yield criteria. Either radial or vertical dynamic load was dealt in numerical examples. Normal arch and arch with maximum shape imperfection of L/11,000 were studied. The analysis results showed that maximum displacement at the center of arch was occurred when 70% of arch span was loaded. The maximum displacement at a quarter of arch span was occurred when 50% of arch span was loaded and the displacement was larger than that of center of arch. Ratio of arch rise to arch span within 0.2∼-.3 seems to be appropriate for arch under radial or vertical load.

• Structural Engineering and Mechanics
• /
• v.58 no.2
• /
• pp.327-345
• /
• 2016

Many experimental and analytical studies have been conducted with beam-column subassemblages composed of a two-span beam to investigate the progressive collapse resistance of RC frames. Most study results reveal a strength-decreased transition phase in the nonlinear static load-deflection curve, which may induce dynamic snap-through response and increase the chord rotation demand for effective catenary action (ECA). In this study, the nonlinear static response is idealized as a piecewise linear curve and analytical pseudo-static response is derived for each linearized region to investigate the rotation demands for the ECA of the two-span RC beams. With analytical parameters determined from several published test results, numerical analysis results indicate that the rotation demand of 0.20 rad recommended in the design guidelines does not always guarantee the ECA. A higher rotation demand may be induced for the two-span beams designed with smaller span-to-depth ratios and it is better to use their peak arch resistance (PAR) as the collapse strength. A tensile reinforcement ratio not greater than 1.0% and a span-to-depth ratio not less than 7.0 are suggested for the two-span RC beams bridging the removed column if the ECA is expected for the collapse resistance. Also, complementary pseudo-static analysis is advised to verify the ECA under realistic dynamic column loss even though the static PAR is recovered in the nonlinear static response. A practical empirical formula is provided to estimate an approximate rotation demand for the ECA.

• Steel and Composite Structures
• /
• v.50 no.1
• /
• pp.107-122
• /
• 2024

Following an internal column failure, adjacent double-span beams above the failed column will play a critical role in the load transfer and internal force redistribution within the remaining structure, and the span-to-depth ratios of double-span beams significantly influence the structural resistance capacity against progressive collapse. Most existing studies have focused on the collapse-resistant performances of single-story symmetric structures, whereas limited published works are available on the collapse resistances of multi-story steel frames with unequal spans. To this end, in this study, numerical models based on shell elements were employed to investigate the structural behavior of multi-story steel frames with unequal spans. The simulation models were validated using the previous experimental results obtained for single- and two-story steel frames, and the load-displacement responses and internal force development of unequal-span three-story steel frames under three cases were comprehensively analyzed. In addition, the specific contributions of the different mechanism resistances of unequal-span, double-span beams of each story were separated quantitatively using the energy equilibrium theory, with an aim to gain a deeper level of understanding of the load-resistance mechanisms in the unequal-span steel frames. The results showed that the axial and flexural mechanism resistances were determined by the span ratio and linear stiffness ratio of double-span beams, respectively.

• Wind and Structures
• /
• v.16 no.3
• /
• pp.279-300
• /
• 2013

This paper presents a new analysis framework for predicting the internal buffeting forces in bridge components under skew wind. A linear regressive model between the internal buffeting force and deformation under normal wind is derived based on mathematical statistical theory. Applying this regression model under normal wind and the time history of buffeting displacement under skew wind with different yaw angles in wind tunnel tests, internal buffeting forces in bridge components can be obtained directly, without using the complex theory of buffeting analysis under skew wind. A self-anchored suspension bridge with a main span of 260 m and a steel arch bridge with a main span of 450 m are selected as case studies to illustrate the application of this linear regressive framework. The results show that the regressive model between internal buffeting force and displacement may be of high significance and can also be applied in the skew wind case with proper regressands, and the most unfavorable internal buffeting forces often occur under yaw wind.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.968-975
• /
• 1988

The maximum feedrate generated from the hardware DDA is closely related to its calculation efficiency. The smaller interpolation span results in the lower calculation efficiency. This paper presents the method to improve the calculation efficiency for the smaller interpolation span. For the linear interpolation the higher calculation efficiency can be achieved by putting biggest value that the interpolation DDA can hold. for the circular interpolation, however, the scheme used for linear interpolation does not work since arbitrary change of value in the interpolation DDA changes the radius of the circle. The bit length of the hardware DDA is adjusted instead of adjusting the value in DDA, which results in the every same effect on calculation efficiency for the circular interpolation. The hardware circuit and supporting software are designed, and tested by two axis step motor driven milling machine. The experimental results show that the proposed method drastically increases the maximum feedrate even for the smaller interpolation span.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.519-524
• /
• 1999

A bulb-tee sectioned girder is proposed for long span bridge exceeding 40 meters. The proposed bulb-tee girder is developed by non-linear analysis process. This study investigates the structural behavior and efficiency of proposed bulb-tee sectioned girder using 1/2 scaled prototype beam specimen. Three specimens are tested under three point static loading system. The crack patterns, failure mode and ultimate load capacity of each specimen are reported in this paper and they are compared to each other.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1998.04a
• /
• pp.335-340
• /
• 1998

The apparently different physical problems of lateral vibration and elastic stability of a linear member are limiting cases of a single phenomenon, the more general expression being the mode of vibration with end thrust. For a single-span beam-column, it is generally known that the square of the frequency of lateral vibration is approximately linearly related to compressive axial force. In this paper the relationship between the frequency and axial force of multi-span compression members is investigated by means of the finite element method.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.51 no.7
• /
• pp.317-322
• /
• 2002

This paper presents a linear temperature/voltage relation over a temperature range(0~100$^{\circ}C$) with high-resolution, reasonably god response linearity, reliability, and overall improved performance. A notable feature of the proposed method is that the whole temperature span is divided by 16 subbands thus the variation span of measured voltage is narrowed. Therefore noise characteristic has been improved. The output voltage is amplified after the uniformed DC voltage component is eliminated by offset. We proposed circuit using median value and mean value of digital signal in order to reduce the noise effect. The proposed circuit offers linear temperature/voltage conversion over a wide dynamic range using DSP(TMS320C31) and steinhart equation.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1996.10a
• /
• pp.195-201
• /
• 1996

This paper is mainly forcused on the application of modal analysis In analyze the geometrically non-linear buckling behaviors of large span spatial structures, and the evaluation of each eigen mode affected post-buckling behaviors and buckling loads. Modal analysis is applied . to derivation of the system matrices transforming actual displacement space into generalized coordinates space represented by coefficients multiplied in the linear combination of eigen modes which are independent and orthogonal each other. By using modal analysis method, it will be expected to save the calculating time by computer extremely. For example, we can obtain the satisfactorily good results by using about 7% of total eigen modes only in case of single layer latticed dome. And we can decrease the possibility of divergence on the bifurcation point in the calculation of post-buckling path. Arc-length method and Newton-Raphson iteration method are used to calculate the nonlinear equilibrium path.