• Wind and Structures
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• v.6 no.2
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• pp.127-140
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• 2003

An investigation into the effect of corner cuts on the Strouhal number of rectangular cylinders with various dimensional ratios and various angles of attack is described. The Strouhal number given as a function of corner cut size is obtained directly from the aerodynamic behavior of the body in a uniform flow through a series of wind-induced vibration tests. For a quick verification of the validity of the Strouhal numbers obtained in this way, they are compared with the approximated the Strouhal numbers based on Shiraishi's early research. The test results show that the Strouhal number of the model with various corner cuts has a fluctuating trend as the angle of attack changes. For each cutting ratio as the angle of attack increases at each cutting ratio above $15^{\circ}$, the Strouhal number decreases gradually, and these trends are more evident for larger corner cut sizes. However, a certain corner cut size which is effective in reducing the wind-induced vibration can be identified by larger Strouhal numbers than those of other corner cut sizes. Three distinct characteristics of Strouhal number variation can be identified in three regions which are termed as Region I, II, and III based on the general trend of the test results. It is also found that the corner cut is effective in one region (Region-II) and less effective in another one (Region-III) when only the vortex-induced vibration occurs.

• Wind and Structures
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• v.2 no.3
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• pp.173-187
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• 1999

The flow around a structure has been an important subject in wind engineering research. There are various kinds of unstable aerodynamic phenomena with regard to a bluff body. In order to understand the physical mechanism of aerodynamic and aeroelastic instability of a bluff body, the relations between the flow around structures and the motion of body with various section shapes should be investigated. Based on a series of wind tunnel tests, this paper addresses the aerodynamic stability of square cylinder with various corner cuts and attack angles in the uniform flow. The test results show that the models with corner cut produced generally better behaviour for the galloping phenomenon than the original section. However, the corner cut method can not prevent the occurrence of the vortex-induced vibration(VIV). It is also shown that as the attack angle changes, the optimum size of corner cut changes also. This means that any one specific size of corner cut which shows the best aerodynamic behaviour throughout all the cases of attack angles does not exist. This paper presents an intensive study on obtaining the optimum size of corner cut for the stabilization of aerodynamic behaviour of cylinders.

• International Journal of High-Rise Buildings
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• v.8 no.4
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• pp.303-311
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• 2019

The effectiveness of aerodynamic modification to reduce wind loadings has been widely reported. However, most of previous studies have been investigated dynamic forces and pressure distributions on tall buildings with various unconventional configurations. This study was investigated dynamic characteristics and aerodynamic instability of super-tall buildings with unconventional configurations through extensive aeroelastic model experiments. Seventeen types of supertall building models were considered such as basic and corner modification with corner cut, chamfered, oblique opening, tapered, inversely tapered, bulged, helical with twist angles of $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, $360^{\circ}$ and composite with $360^{\circ}$ helical & corner cut, 4-tapered & $360^{\circ}$ helical & corner cut, setback & corner cut, setback & $45^{\circ}$ rotate. As a result, aerodynamic characteristics of helical models with single modification are superior to those of other models with single modification. However, effect of twist angle for helical model is negligible. Further, the 4-tapered & $360^{\circ}$helical & corner cut model is most effective in reducing the along- and across-wind fluctuating displacement responses in all of experimental models.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.339-348
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• 2022

The bored tunneling method is generally preferred for urban tunnel construction, However the cut & cover tunnel is still necessary for special conditions, such as metro station and access structures. In some case, deep excavation for cut & cover construction is planed of irregular and unusual shape, as a consequence, the convex and concave corner is often encountered during that excavation. In particular, discontinuity or imbalance of the support structure in the convex corner can lead to collapse, which may result in damages and casualties. In this study, the behavior of the convex corner of retaining structure were investigated using 3-dimensional numerical models established to be able to simulate the split-shaped behavior of convex corners. To improve the stability in the vicinity of the convex corner, several stabilizing measures were proposed and estimated numerically. It is found that linking two discretized wales at the convex corner can effectively perform the control of deformation. Furthermore, it was also confirmed that the stabilizing measures can be enhanced when the tie-material linking two discretized wales is installed at the depth of the maximum wall deflection.

• International Journal of High-Rise Buildings
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• v.8 no.4
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• pp.283-290
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• 2019

Corner cut, corner chamfered or a building shape change are adopted in the design of tall buildings to achieve aerodynamic superiority as well as response reduction. Kikuchi et.al pointed out that large negative peak external pressures can appear near the inside corner of set-back low rise buildings. It is therefore necessary to pay attention to facade design around steps in building surfaces. Peak wind pressures for corner cut or corner chamfered configurations are given in the AIJ code. However, they cannot be applied where there are many variations of vertical and horizontal steps. There has been no previous systematic research on peak wind pressures around steps in building surfaces. In this study, detailed phenomenon of peak wind pressures around steps in buildings are investigated focusing on vertical and horizontal distances from the building's corner.

• International Journal of CAD/CAM
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• v.3 no.1_2
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• pp.1-12
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• 2003

When milling concave corners, cutter load increases momentarily and fluctuates severely due to concentration and uneven distribution of material stock. This abrupt change of cutter load produces undesirable machining results such as wavy machined surface and cutter breakage. An important factor for studying cutter load in 2.5D pocket milling is the instantaneous Radial Depth of Cut (RDC). However, previous work on RDC under different corner-cutting conditions is lacking. In this different corner shapes. In our work, we express RDC mathematically in terms of the instantaneous cutter engage angle which is defined as Cutter Swept Angle (CSA). An analytical approach for modeling CSA is explained. Finally, examples are shown to demonstrate that the proposed CSA modeling method can give an accurate prediction of cutter load pattern at cornering cut.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.67-75
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• 2000

virtual computer numerical control(VCNC) arises from the concept that one can experience pseudo-real machining with a computer-numerically-controlled(CNC) machine before actually cutting an object. To achieve accurate VCNC, it is important to determine abnormal behavior, such as chatter, before cutting. Detecting chatter requires an understanding of the dynamic cutting force model. In general, the cutting process is a closed loop system the consists of structural and cutting dynamic. Machining instability, namely chatter, results from the interaction between these two dynamics. Several previous reports have predicted stability for a single path, using a simple cutting force model without run out and penetration effects. This study considers both tool run out and penetration effects, using experimental modal analysis, to obtain predictions that are more accurate. The machining stability during a corner cut, which is a typical transient cut, was assessed from an evaluation of the cutting configurations at the corner.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.195-204
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• 2001

Virtual computer numerical control(VCNC) arises from the concept that one can experience pseudo-real machining with a computer-numerically-controlled(CNC) machine before actually cutting an object. To achieve accurate VCNC, it is important to determine abnormal behavior, such as chatter, before cutting. Detecting chatter requires an understanding of the dynamic cutting force model. In general, the cutting process is a closed loop system that consists of structural and cutting dynamics. Machining instability, namely chatter, results from the interaction between these two dynamics. Several previous reports have predicted stability for a single path, using a simple cutting force model without tool runout and penetration effects. This study considers both tool runout and penetration effects, using experimental modal analysis, to obtain more accurate predictions. The machining stability in the corner cut, which is a typical transient cut, was assessed from an evaluation of the cutting configurations at the corner.

• Wind and Structures
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• v.30 no.3
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• pp.245-260
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• 2020

Wind load and responses are the major factors which govern the design norms of tall buildings. Corner modification is one of the most commonly used minor shape modification measure which significantly reduces the wind load and responses. This study presents a comparison of wind load and pressure distribution on different corner modified (chamfered and rounded) Y plan shaped buildings. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and Shear Stress Transport (SST), are used in the simulation of the building and the data are compared with the previous experimental results in a similar flow condition. The variation of the flow patterns, distribution of pressure over the surfaces, force and moment coefficients are evaluated and the results are represented graphically to understand the extent of nonconformities due to corner modifications. Rounded corner shape is proving out to be more efficient in comparing to chamfered corner for wind load reduction. The maximum reduction in the maximum force and moment coefficient is about 21.1% and 19.2% for 50% rounded corner cut.

• International Journal of High-Rise Buildings
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• v.8 no.4
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• pp.235-253
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• 2019

This paper reviews shape optimization studies for tall and super-tall building design. Firstly, shape effects on aerodynamic and response characteristics are introduced and discussed. Effects of various configurations such as corner modifications, taper, setback, openings, and twists are examined. Comprehensive comparative studies on various configurations including polygon building models, and composite type building models such as corner-cut and taper, corner-cut and taper and helical, and so on, are also discussed under the conditions of the same height and volume. Aerodynamic characteristics are improved by increasing the twist angle of helical buildings and increasing the number of sides of polygon buildings, but a twist angle of $180^{\circ}$ and a number of sides of 5 (pentagon) seem to be enough. The majority of examined configurations show better aerodynamic characteristics than straight-square. In particular, composite type buildings and helical polygon buildings show significant improvement. Next, shape effects on pedestrian-level wind characteristics around tall and super-tall buildings are introduced and discussed. Corner modification buildings show significant reductions in speed-up areas. On the other hand, setback and tapered models with wider projected widths near the ground show adverse effects on pedestrian-level wind characteristics.