• Wind and Structures
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• 제11권5호
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• pp.361-376
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• 2008

This paper considers internal pressure fluctuations for a range of building volumes and dominant wall opening areas. The study recognizes that the air flow in and out of the dominant opening in the envelope generates Helmholtz resonance, which can amplify the internal pressure fluctuations compared to the external pressure, at the opening. Numerical methods were used to estimate fluctuating standard deviation and peak (i.e. design) internal pressures from full-scale measured external pressures. The ratios of standard deviation and peak internal pressures to the external pressures at a dominant windward wall opening of area, AW are presented in terms of the non-dimensional opening size to volume parameter, $S^*=(a_s/\bar{U}_h)^2(A_W^{3/2}/V_{Ie})$ where $a_s$ is the speed of sound, $\bar{U}_h$ is the mean wind speed at the top of the building and $V_{Ie}$ is the effective internal volume. The standard deviation of internal pressure exceeds the external pressures at the opening, for $S^*$ greater than about 0.75, showing increasing amplification with increasing $S^*$. The peak internal pressure can be expected to exceed the peak external pressure at the opening by 10% to 50%, for $S^*$ greater than about 5. A dominant leeward wall opening also produces similar fluctuating internal pressure characteristics.

• 한국건축시공학회지
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• 제8권6호
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• pp.161-166
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• 2008

This study is focused on the welding performance of automatic gas pressure welding machine adapted to korean construction site by external appearance investigation. As gas pressure welding is more economical and has good performances compared with other steel bar jointing methods, as arc welding and mechanical joint etc, in Japan, the gas pressure welding is one of the typical connection of steel reinforcement when connecting the D29 and thicker steel bars, But in Korea, gas pressure welding joint method is not widely used caused by the shortage of skilled workers. so to activate the gas pressure welding in Korea, the automatic gas pressure welding machine is developed. In this study, the welding performances of gas pressure welding joint samples using korean automatic gas pressure welding machine are measured by external appearance investigation - blown diameters, blown length, welding face disagreement, central axis eccentric ratio, bending, sag and crack. The results of welding performances on the gas pressure welding joint samples show that samples are satisfied with the standard value regulated in KS D 0244 and JIS Z 3120.

• 한국철도학회논문집
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• 제12권2호
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• pp.309-314
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• 2009

열차가 터널에 진입하면 열차의 전두부에 의해 압축파가, 후마부에 의해 팽창파가 터널 내에 각각 발생하게 된다. 터널내부에서 압축파와 팽창파가 열차와 서로 상호작용하면서 열차 실내/외의 양력은 급격하게 변화한다. 본 논문에서는 한국형 틸팅차량이 터널 주행 시 나타나는 차량의 실내 및 실외(차량표면) 압력변화 및 압력변화율을 분석하여, 터널길이와의 상관관계를 분석하였다. 또한, 현 틸팅차량의 기밀상태에서 터널주행 시 실내압력변화율을 검토하였다. 그 결과 길이가 짧은 터널에서는 압력파의 중첩이 발생하지 않아서 차량 실내/외 압력변화는 크게 나타나지 않았다. 하지만, 긴 터널에서는 압력파의 중첩과 차량과의 상호작용이 동시에 일어나면서 급격한 압력변화가 뚜렷하게 발생하였다. 또한, 특정한 길이의 터널에서는 압축파와 팽창파가 중첩되어 압력변화 및 변화율을 크게 완화시켰다.

• Structural Engineering and Mechanics
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• 제18권5호
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• pp.627-644
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• 2004

In this study, the endochronic theory was used to investigate the collapse of thick-walled tubes subjected to external pressure and axial tension. The experimental and theoretical findings of Madhavan et al. (1993) for thick-walled tubes of 304 stainless steel subjected to external pressure and axial tension were compared with the endochronic simulation. Collapse envelopes for various diameter-to-thickness tubes under two different pressure-tension loadings were involved. It has been shown that the experimental results were aptly described by the endochronic approach demonstrated from comparison with the theoretical prediction employed by Madhavan et al. (1993). Furthermore, by using the rate-sensitivity function of the intrinsic time measure proposed by Pan and Chern (1997) in the endochronic theory, our theoretical analysis was extended to investigate the viscoplastic collapse of thick-walled tubes subjected to external pressure and axial tension. It was found that the pressure-tension collapse envelopes are strongly influenced by the strain-rate during axial tension. Due to the hardening of the metal tube of 304 stainless steel under a faster strain-rate during uniaxial tension, the size of the tension-collapse envelope increases.

• Wind and Structures
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• 제21권1호
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• pp.1-23
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• 2015

Wind tunnel testing of a low-rise building with openings (holes) of different sizes and shapes on a roof corner is conducted to measure the internal and external pressures from the building model. Detailed analysis of the testing data is carried out to investigate the characteristics of the internal and external pressures of the building with different openings' configurations. Superimposition of the internal and external pressures makes the emergence of positive net pressures on the roof. The internal pressures demonstrate an overall uniform distribution. The probability density function (PDF) of the internal pressures is close to the Gaussian distribution. Compared with the PDF of the external pressures, the non-Gaussian characteristics of the net pressures weakened. The internal pressures exhibit strong correlation in frequency domain. There appear two humps in the spectra of the internal pressures, which correspond to the Helmholtz frequency and vortex shedding frequency, respectively. But, the peak for the vortex shedding frequency is offset for the net pressures. Furthermore, the internal pressure characteristics indirectly reflect that the length of the front edge enhances the development of the conical vortices.The objective of this study aims to further understanding of the characteristics of internal, external and net pressures for low-rise buildings in an effort to reduce wind damages to residential buildings.

• Nuclear Engineering and Technology
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• 제42권4호
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• pp.450-459
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• 2010

The present paper investigates the collapse pressure of cylinders with intermediate thickness subjected to external pressure based on detailed elastic-plastic finite element (FE) analyses. The effect of the initial ovality of the tube on the collapse pressure was explicitly considered in the FE analyses. Based on the present FE results, the analytical yield locus, considering the interaction between the plastic collapse and local instability due to initial ovality, was also proposed. The collapse pressure values based on the proposed yield locus agree well with the present FE results; thus, the validity of the proposed yield locus for the thickness range of interest was verified. Moreover, the partial safety factor concept based on the structural reliability theory was also applied to the proposed collapse pressure estimation model, and, thus, the priority of importance of respective parameter constituting for the collapse of cylinders under external pressure was estimated in this study. From the application of the partial safety factor concept, the yield strength was concluded to be the most sensitive, and the initial ovality of tube was not so effective in the proposed collapse pressure estimation model. The present deterministic and probabilistic results are expected to be utilized in the design and maintenance of cylinders subjected to external pressure with initial ovality, such as the once-through type steam generator.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.355-360
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• 2013

A wireless intraocular (IOP) pressure sensor based on micro electro mechanical system (MEMS) technology is proposed. The proposed IOP sensor uses variable inductance according to the external pressure. The proposed sensor is composed of two flexible membranes: a ferrite bottom part, an inductor, and a capacitor. The inductance of the sensor varies according to the external pressure. The resonance frequency of the sensor is also varied, and this frequency is detected using an external coil. The external coil is designed with an FR-4 printed circuit board. The feasibility of the proposed sensor structure using variable inductance to detect the external pressure is successfully demonstrated.

• Wind and Structures
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• 제11권6호
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• pp.479-496
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• 2008

In this paper, computer simulation of wind flow around a single cooling tower with louver support at the base in the KAZERUN power station in south part of IRAN is presented as a case study. ANSYS FLOTRAN, an unstructured finite element incompressible flow solver, is used for numerical investigation of wind induced pressure load on a single cooling tower. Since the effects of the wind ribs on external surface of the cooling tower shell which plays important role in formation of turbulent flow field, an innovative relation is introduced for modeling the effects of wind ribs on computation of wind pressure on cooling tower's shell. The introduced relation which follows the concept of equivalent sand roughness for the wall function is used in conjunction with two equations ${\kappa}-{\varepsilon}$ turbulent model. In this work, the effects of variation in the height/spacing ratio of external wind ribs are numerically investigated. Conclusions are made by comparison between computed pressure loads on external surface of cooling tower and the VGB (German guideline for cooling tower design) suggestions.

• 한국기계가공학회지
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• 제6권2호
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• pp.3-8
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• 2007

Nonlinear property and contact matter are analyzed about the pipe applied with internal pressure through this study. The weakest part and its safety can be examined. Maximum equivalent stress is shown at the contact surface between bolt and nut. The value of contact stress with the pressure of 12MPa is increased 1.4 times as large as that with no pressure. The maximum contact pressure is shown at the clamp corner of the external surface on pipe. The value of contact pressure with the pressure of 12MPa is increased 1.4 times as large as that with no pressure. The radial deformation with no pressure is also increased greatly at the middle part of internal surface on pipe. But this maximum deformation on pipe with the pressure of 12MPa is shown at the part far away the support of pipe. This value is increased 5.7 times as large as that value with no pressure. As contact status, the sticking occurs most at the external surface of pipe. It also tends to occur at the contact surface between bolt and nut. At the external surface of pipe, the sticking in case of the pressure of 12MPa occurs more than that in case of no pressure.

• Structural Engineering and Mechanics
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• 제6권7호
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• pp.827-839
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• 1998

This paper presents a study of buckling of the multi-vaulted cylindrical shell ("Aster"), under an axial compression alone or combined with an external pressure. This shell which was presented in a recent paper is a self-stiffened structure having a satisfactory behaviour and a higher buckling strength under external pressure than a circular cylindrical shell with the same dimensions. The results of this study emphasize the interest of the behaviour of the "Aster" shell under two other types of loading, revealing an acceptable level of strength which is favorable for an expansion of its use in other areas.