CORD-19_Custom_license_subset  

CORD-19:d7faaf4dd7caf361022ba62c8cedcfec8bf5b896 JSONTXT 11 Projects

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Id Subject Object Predicate Lexical cue
T1 0-95 Sentence denotes Adopting 'lift-up' building design to improve the surrounding pedestrian-level wind environment
T2 97-105 Sentence denotes Abstract
T3 106-224 Sentence denotes Modern megacities are teeming with closely-spaced tall buildings, which limit air circulation at the pedestrian level.
T4 225-364 Sentence denotes The resultant lack of air circulation creates poorly ventilated areas with accumulated air pollutants and thermal discomfort in the summer.
T5 365-553 Sentence denotes To improve air circulation at the pedestrian level, buildings may be designed to have a 'lift-up' shape, in which the main structure is supported by a central core, columns or shear walls.
T6 554-698 Sentence denotes However, a lack of knowledge on the influence of the 'lift-up' design on the surrounding wind environment limits the use of 'lift-up' buildings.
T7 699-854 Sentence denotes This study aims to investigate the influence of 'lift-up' buildings and their dimensions on the pedestrian-level wind environments using wind tunnel tests.
T8 855-965 Sentence denotes A parametric study was undertaken by using 9 'lift-up' building models with different core heights and widths.
T9 966-1076 Sentence denotes The results were compared with the surrounding wind environment of a control building with similar dimensions.
T10 1077-1251 Sentence denotes The results reveal that the 'lift-up' core height is the most influential parameter and governs the area and magnitude of high and low wind speed zones around such buildings.
T11 1252-1424 Sentence denotes Based on wind tunnel test results and a selected comfort criterion, appropriate core dimensions could be selected to have acceptable wind conditions near lift-up buildings.
T12 1426-1596 Sentence denotes With the advent of light-weight construction materials and advanced structural forms, modern tall buildings are frequently designed with unusual shapes and complex forms.
T13 1597-1738 Sentence denotes Some of these atypical shapes improve the aerodynamic performances of the buildings themselves and bring economic benefits to the developers.
T14 1739-1901 Sentence denotes For example, the aerodynamic forces and wind excitations of tall buildings may be effectively minimised by tapered shapes and chamfered corners [11, 18, 19, 21] .
T15 1902-2051 Sentence denotes In addition, certain building forms have proved useful in achieving acceptable wind conditions at the pedestrian level around buildings [5, 10, 22] .
T16 2052-2336 Sentence denotes In contrast to the influence of novel building forms on the aerodynamic behaviour of high-rise buildings, which has long been a topic for academic research and hence been thoroughly investigated, their influence on the pedestrian-level wind field has yet to be systematically studied.
T17 2337-2625 Sentence denotes Considering the importance of the pedestrian-level wind fields in a tropical metropolis, it is necessary to analyse the impact of novel building forms on the pedestrianlevel wind field in order to select appropriate building forms to produce acceptable pedestrian-level urban wind fields.
T18 2626-2797 Sentence denotes Wind nuisance in cities is typically caused by tall buildings, as they frequently produce unacceptable, even dangerous, windy conditions at the pedestrian level [14, 15] .
T19 2798-3063 Sentence denotes Although high wind speeds are typically considered as the cause of pedestrian discomfort, wind-related environmental issues in cities such as Hong Kong, Tokyo, and New Delhi have switched from dangerously high wind speeds to undesirable low wind speeds [4, 6, 20] .
T20 3064-3259 Sentence denotes Undesirable low wind speeds are a result of excessive sheltering by closely-spaced tall buildings, built in such a way to cope with the high land prices and scarcity of available lands in cities.
T21 3260-3414 Sentence denotes Because developers do not want to lose usable space, there is a reluctance to reduce building dimensions so as to provide more space for air to circulate.
T22 3415-3583 Sentence denotes Newly developed building forms may be an alternative solution to improve pedestrian-level wind conditions in cities without sacrificing the useable space of a building.
T23 3584-3709 Sentence denotes However, some common building forms used in cities impede air circulations by obstructing breezeways at the pedestrian level.
T24 3710-3854 Sentence denotes Hong Kong is a classic example of a city where the use of inappropriate building forms has led to a deterioration of the urban wind environment.
T25 3855-4082 Sentence denotes For example, closely-spaced tall buildings and bulk podium structures in Hong Kong substantially reduce wind penetration into the city and consequently generate undesirable low wind speeds at the pedestrian level [16, 20, 26] .
T26 4083-4216 Sentence denotes Low wind speeds that allow air pollutants to remain near the ground also continue to exacerbate the air pollution in Hong Kong [23] .
T27 4217-4401 Sentence denotes Widespread stagnant air can be favourable to the spread of air-borne pathogens such the SARS virus (Severe Acute Respiratory Syndrome) and hence is a threat to the public health [27] .
T28 4402-4650 Sentence denotes Moreover, mean wind speeds smaller than 1.5 m s À1 , the minimum mean wind speed required by the Air Ventilation Assessment stipulated in Hong Kong, can cause outdoor thermal discomfort for pedestrians, especially in the hot summer months [3, 16] .
T29 4651-4753 Sentence denotes The 'lift-up' building design is a potential solution for enhancing urban air ventilation in the city.
T30 4754-4914 Sentence denotes The main structure of a 'lift-up' building is elevated from the ground by individually, or a combination of, columns, shear walls, and a central core (Fig. 1 ).
T31 4915-5080 Sentence denotes The main structure elevated from the ground is known as 'lift-up' floors, and the ground area under the elevated main structure is referred to as the 'lift-up' area.
T32 5081-5277 Sentence denotes The main benefit of the open space between the ground and the 'lift-up' floors is to minimize obstruction to wind flow at the ground level to enhance wind circulation at the pedestrian level [7] .
T33 5278-5408 Sentence denotes In addition, the 'lift-up' area can be used as a recreational area, parking area, or a pathway to access other buildings or areas.
T34 5409-5571 Sentence denotes The 'lift-up' design is, however, not widely adopted for buildings due to unacceptable or even dangerous high wind speeds found in the 'lift-up' area [1, 5, 17] .
T35 5572-5776 Sentence denotes These high wind speeds are a result of accelerated wind flows through narrowing openings, which connect positive and negative pressures on the windward and leeward sides of a building, respectively [17] .
T36 5777-5954 Sentence denotes However, the accelerated wind flows in the 'lift-up' areas may be favourable in achieving the minimum acceptable wind speeds in cities where undesirable low wind speeds prevail.
T37 5955-6293 Sentence denotes In fact [25] , have demonstrated that the addition of 'lift-up' floors to a single building, a building array, and building(s) with podium structure(s) can considerably increase the wind circulation around the building and is effective in achieving outdoor thermal comfort even under the prevailing low wind speed conditions in Hong Kong.
T38 6294-6460 Sentence denotes However [25] , employed a single core size thus no results are available to quantify the influence of the 'lift-up' core dimensions on the pedestrianlevel wind field.
T39 6461-6615 Sentence denotes This lack of understanding on influential parameters of 'lift-up' core dimensions prevents designers to adopt the 'lift-up' design to buildings in cities.
T40 6616-6902 Sentence denotes Therefore, the present study aims to assess the influence of 'lift-up' core dimensions on the pedestrian-level wind environment, so as to be used to guide designers to adopt a 'lift-up' design for buildings to improve pedestrian-level wind conditions in a modern city such as Hong Kong.
T41 6903-7033 Sentence denotes A series of wind tunnel tests were conducted using 9 isolated building models with different dimensions of central 'lift-up' core.
T42 7034-7325 Sentence denotes Albeit being the simplest building arrangement, isolated buildings are (1) able to generate less complex flow conditions than in a group of buildings, and (2) capable of producing all important flow features in the surrounding wind environment [1, 8, 12] thus selected for the current study.
T43 7326-7543 Sentence denotes On the other hand, a central core design would minimize the influence on wind conditions in the liftup area, the main concern of this study, compared to rows of columns or shear walls at the perimeter of the building.
T44 7544-7891 Sentence denotes In the wind tunnel tests, the wind speeds at the pedestrian level near lift-up buildings were measured and subsequently compared with wind speeds near a control building model (i.e., a building without the 'lift-up' design) with similar dimensions in order to identify flow features in pedestrian-level wind field modified by the 'lift-up' design.
T45 7892-7943 Sentence denotes The rest of the manuscript is organized as follows.
T46 7944-8134 Sentence denotes After the introduction, section 2 presents the experimental setup of the wind tunnel tests, including details of the building models, measurement techniques, and approaching wind conditions.
T47 8135-8441 Sentence denotes Section 3 discusses the results of the wind tunnel tests in three subsections; (1) the overall wind environment near the 'lift-up' building models, (2) the characteristics of the high and low wind speed zones around the 'lift-up' building models, and (3) the distribution of wind speeds in 'lift-up' areas.
T48 8442-8577 Sentence denotes Concluding remarks are presented in section 4 in the form of a number of guidelines for designing 'lift-up' buildings in a modern city.
T49 8578-8762 Sentence denotes The wind tunnel tests described in this paper were conducted in the CPL Power Wind/Wave Tunnel Facility (WWTF) at the Hong Kong University of Science and Technology (HKUST), Hong Kong.
T50 8763-8955 Sentence denotes The WWTF is a closed-return type boundary layer wind tunnel (BLWT) and has two parallel test sections named as "high speed" and "low speed" with different dimensions and operating wind speeds.
T51 8956-9125 Sentence denotes The wind tunnel tests were carried out in the "low speed" section, which has a test section of 5 m  4 m (width x height) and maximum operating wind speed of 10 m s À1 .
T52 9126-9313 Sentence denotes The approaching wind speed and turbulence intensity profiles were simulated by arranging roughness elements and spires in the upstream of the flow development section, which is 41 m long.
T53 9314-9424 Sentence denotes Fig. 2 displays the measured mean wind speed and turbulence intensity profiles at the centre of the turntable.
T54 9425-9536 Sentence denotes The mean wind speed profile followed the power law wind profile model with an exponent of 0.11 (equation (1a)).
T55 9537-9752 Sentence denotes The mean wind speed (U) and the longitudinal turbulence intensity (I u ), which is calculated as in equation (1b), measured at the 100 mm height at the centre of the turntable were 6.3 m s À1 and 9.5%, respectively.
T56 9753-9831 Sentence denotes Table 1 shows full-scale dimensions of the 9 buildings modelled in this study.
T57 9832-9922 Sentence denotes It is noted that the building models are different in terms of the dimensions of the core.
T58 9923-10107 Sentence denotes More specifically, height (h), width (w) and depth (d) of the central core vary among the 9 buildings while the total height (H), width (W), and depth (D) of buildings remain constant.
T59 10108-10205 Sentence denotes There were 3 core heights (i.e., 3 m, 6 m, and 9 m) and 3 core areas tested in the present study.
T60 10206-10370 Sentence denotes The core area is expressed as the percentage of area covered by the core out of the plan area of the building at the ground level, termed as "area percentage" (AP).
T61 10371-10444 Sentence denotes The selected core areas for this study had AP values of 9%, 25%, and 49%.
T62 10445-10527 Sentence denotes All building models were manufactured using balsa wood to a length scale of 1:200.
T63 10528-10722 Sentence denotes The wind environments surrounding the building models at the pedestrian level were evaluated using mean wind speeds measured by Irwin sensors and Kanomax thermal anemometer system (Kanomax1560).
T64 10723-10855 Sentence denotes The Irwin sensors used in the present study were fabricated according to the 1:200 length scale with a 10 mm height protruding tube.
T65 10856-10986 Sentence denotes The protruding tube is to measure the wind speeds at the 10 mm height, which is equal to 2 m measurement height in the full scale.
T66 10987-11136 Sentence denotes The mean wind speed (U) at the 10 mm height was calculated from the Irwin sensors' raw measurements according to the method proposed by Ref. [9] ; as
T67 11137-11435 Sentence denotes In equation (2), ffiffiffiffiffiffi ffi DP p is the square root of the pressure difference between two holes on the Irwin sensor, and a and b are constants, which are determined from the curve fitting of mean wind speeds (U) measured by a hot-wire anemometer and ffiffiffiffiffiffi ffi DP p values.
T68 11436-11515 Sentence denotes In the present study, a and b were estimated to be 0.15 and 1.72, respectively.
T69 11516-11643 Sentence denotes Readers are suggested to refer studies of [9, 24] ; and [20] for further information of Irwin sensor and its working principle.
T70 11644-11790 Sentence denotes The Kanomax1560 anemometer system is a multi-channel thermal anemometer system, which has multiple wind speed sensors and a data acquisition unit.
T71 11791-11943 Sentence denotes The wind speed sensor is a spherical thermistor type omnidirectional sensor, which measures resultant mean wind speed a low sampling frequency at 10 Hz.
T72 11944-12109 Sentence denotes Each sensor has a temperature compensator unit to correct any temperature effect on the measurements and is pre-calibrated with its own individual calibration curve.
T73 12110-12284 Sentence denotes Its convenience in operating, and the ability to measure lower wind speeds are added advantages of Kanomax anemometer system being used in pedestrian-level wind tunnel tests.
T74 12286-12441 Sentence denotes The normalized mean wind speed ratio (K) have been used effectively by previous researchers [2, 17, 20 ] to analyse the pedestrian-level wind environments.
T75 12442-12680 Sentence denotes The advantages of the use of K value are its ability to eliminate the differences in wind speeds and turbulence intensities of incoming wind flows and only highlight the modifications occurred in the local wind environment near buildings.
T76 12681-12832 Sentence denotes Moreover, by knowing the K values, designers can calculate corresponding wind speeds by using local meteorological wind speed data at a given location.
T77 12833-12959 Sentence denotes For this study, K value is calculated by using the measured mean wind speeds at the 10 mm height as expressed in equation (3).
T78 12960-13160 Sentence denotes where, U 10mm;x;y is the mean wind speed at the 10 mm height measured at a location (x, y), and U 10mm;ambient is the mean wind speed at the 10 mm height at the same location but without the building.
T79 13161-13335 Sentence denotes Fig. 5 (a) and (b) display the distributions of the K values around a 'lift-up' building (i.e., model M5) and the control building (hereafter referred to as CB) respectively.
T80 13336-13479 Sentence denotes The cubic interpolation method was used to plot the contours of K and all the distances were normalized with respect to the building depth (D).
T81 13480-13588 Sentence denotes In figures, the red arrow on the upstream side of buildings points in the direction of the approaching wind.
T82 13589-13811 Sentence denotes Owing to a number of flow modifications, the pedestrian-level wind environment surrounding the 'lift-up' building (model M5) is different from the wind field corresponding to the control building (CB), as shown in Fig. 5 .
T83 13812-14044 Sentence denotes The most noticeable flow modification is found on the lateral sides of the 'lift-up' building where the corner streams (CS), which is also referred as the separation layers, are larger in size and higher in magnitude than of the CB.
T84 14045-14247 Sentence denotes Moreover, the CS zones of model M5 are formed closer to the building in such a way that a portion of the corner streams is in the lift-up area, which is indicated by the dash rectangular box in Fig. 5 .
T85 14248-14390 Sentence denotes The low wind speed (LWS) areas (marked by blue) corresponding to model M5 also display some noticeable differences from those found in the CB.
T86 14391-14572 Sentence denotes Particularly, a distinct LWS area is formed next to the leeward side of model M5, whereas no downstream near-field low wind speed zone (the DNLWS zone) can be identified for the CB.
T87 14573-14816 Sentence denotes The influence of the 'lift-up' floors gradually diminishes far downstream of the building as indicated by the formation of the downstream far-field low wind speed zone (the DFLWS zone) of model M5 at the same location as in the case of the CB.
T88 14817-14919 Sentence denotes However, compared to the CB, model M5's DFLWS zone has a larger area where K values are small (K 0.6).
T89 14920-15101 Sentence denotes Apparently, K values in the Particularly, the HWS zones appearing on the lateral sides of the building display significant variations in size and magnitude with the core dimensions.
T90 15102-15233 Sentence denotes For example, taller cores, such as in model M3, create larger HWS zones further away from the side walls of the 'lift-up' building.
T91 15234-15316 Sentence denotes Shorter cores, on the contrary, produced smaller HWS zones closer to the building.
T92 15317-15464 Sentence denotes Furthermore, the HWS zones, in some extreme cases, occupy a major portion of the 'lift-up' area, such as shown in Fig. 6 corresponding to model M1.
T93 15465-15684 Sentence denotes The 'lift-up' core height has marginal influence on the LWS zones in the upstream and downstream directions of the buildings as indicated by a slight increase of K values in the ULWS zone with the 'lift-up' core height.
T94 15685-15813 Sentence denotes However, the location of the ULWS zone, whether it is attached to the building or not, is strongly dependent on the core height.
T95 15814-16011 Sentence denotes As it can be seen in model M1, the shorter core (h ¼ 3 m) creates an attached ULWS zone, but in model M3, which has a taller core (h ¼ 9 m), produced a ULWS zone that is detached from the building.
T96 16012-16264 Sentence denotes Compared to the 'lift-up' core height, the core area has some distinct influences on the LWS zones both in the upstream and downstream directions of the buildings including the formation of bigger DNLWS zones with smaller K values by larger core areas.
T97 16265-16506 Sentence denotes The observed flow modifications near the 'lift-up' buildings are qualitatively compared to the wind-tunnel test results corresponding to the control building (CB) by using the normalized difference of K values (DK) as defined in equation (4)
T98 16508-16735 Sentence denotes In equation (4), K Mðx;yÞ denotes the normalized wind speed ratio (K) at a location (x,y) in the surrounding of a 'lift-up' building, and K CBðx;yÞ denotes the K value at the same location but in the wind environment of the CB.
T99 16736-16760 Sentence denotes As is evident from Figs.
T100 16761-16888 Sentence denotes 6 and 7 the lift-up buildings modify their surrounding wind environment differently than the building without 'lift-up' floors.
T101 16889-17121 Sentence denotes The differences in the pedestrian-level wind field around buildings with and without 'lift-up' designs are a result of the formation of HWS and LWS zones and their variations in size and magnitude with the 'lift-up' core dimensions.
T102 17122-17256 Sentence denotes Therefore, the rest of the discussion focuses on examining the variations of the HWS and LWS zones with the 'lift-up' core dimensions.
T103 17257-17460 Sentence denotes Furthermore, the pedestrian-level wind field in the 'lift-up' area is systematically investigated to show the characteristics of the wind environment beneath the main structure of the 'lift-up' building.
T104 17461-17563 Sentence denotes Both the size and magnitude of the HWS zones vary with the 'lift-up' core dimensions as shown in Figs.
T105 17564-17572 Sentence denotes 6 and 7.
T106 17573-17758 Sentence denotes A new parameter, the area averaged high wind speed ratio (K HWS ), is introduced to estimate the general effect of the 'lift-up' core dimensions on the HWS zones through a single value.
T107 17759-17856 Sentence denotes It should be noted that only the areas with K values larger than 1.3 are considered as HWS zones.
T108 17857-17919 Sentence denotes According to this criterion, the K HWS value is calculated as;
T109 17921-18130 Sentence denotes In equation (5), K is the contour level when the mean wind speed ratios are larger than 1.3, A HWS is the total area of the HWS zones, and A (K,Kþ0.1) is the area within the contour line between K and K þ 0.1.
T110 18131-18248 Sentence denotes Fig. 8 shows the calculated K HWS values corresponding to the with larger areas, marginally reduces the K HWS values.
T111 18249-18402 Sentence denotes Therefore, an appropriate combination of core height and size would maximise the accelerated wind flows near 'lift-up' buildings as observed in model M6.
T112 18403-18801 Sentence denotes The model M6, which has a taller core and a moderate core area (h ¼ 9 m, AP ¼ 25%) has recorded the largest K HWS value of 1.495 among all the tested 'lift-up' buildings in this study However, if the given objective of the design is to minimize the formation of HWS zones near 'lift-up' buildings, then the designer should select a short and bulky central core for the building such as in model M7.
T113 18802-19059 Sentence denotes Although the overall influence of the 'lift-up' core dimensions on the HWS zone is indicated by the K HWS value, it does not provide detailed information on the composition of the pedestrian-level wind speeds in the HWS zones created by 'lift-up' buildings.
T114 19060-19215 Sentence denotes Consequently, the areas within the contours corresponding to different K values are employed to assess the composition of the wind speeds in the HWS zones.
T115 19216-19329 Sentence denotes The area is then divided by the plan area of the building (B x D) to determine the normalized indicator: AP cum .
T116 19330-19429 Sentence denotes Fig. 9 shows the variation of AP cum with the corresponding K values for different building models.
T117 19430-19557 Sentence denotes The variation of AP cum corresponding to the control building (CB) is also included in Fig. 9 , as shown by the red solid line.
T118 19558-19697 Sentence denotes Fig. 9 clearly shows that 'lift-up' buildings have higher wind speeds (e.g. K ¼ 1.5 and K ¼ 1.6) distributed over larger areas than the CB.
T119 19698-19876 Sentence denotes In the case where the K value is higher than 1.6, all the 'liftup' buildings generate AP cum values larger than 0, whilst there is no measurable area of K > 1.6 found for the CB.
T120 19877-20051 Sentence denotes The variations of wind speeds and corresponding areas in the HWS zones in lift-up buildings are attributed to differences in core heights and areas of the 9 tested buildings.
T121 20052-20296 Sentence denotes For example, the influence of the 'lift-up' core height is more prominent at the higher end of the K values, such as K ¼ 1.6, while core size governs the wind speeds and areas of the HWS zones at the lower end of K values in HWS (e.g. K < 1.4).
T122 20297-20500 Sentence denotes Similar to the HWS zones, the influence of the 'lift-up' core dimensions on the low wind speed (LWS) zones is quantified using the area averaged low wind speed ratio (K LWS ) as defined in equation (6) .
T123 20501-20600 Sentence denotes For the calculation, only areas with K values lower than 0.7 (K < 0.7) are considered as LWS zones.
T124 20601-20823 Sentence denotes In equation.(6), K denotes the contour level corresponding to the mean wind speed ratios lower than 0.7; A LWS is the total area of the LWS zones, and A (K,Kþ0.1) is the area within the contour lines between K and K þ 0.1.
T125 20824-21077 Sentence denotes In compliance with the selection criterion of the LWS zone, two distinct LWS zones are identified on the windward and leeward sides of the 'lift-up' buildings (Fig. 6) , and one noticeable LWS zone is observed upstream of the control building (Fig. 5) .
T126 21078-21250 Sentence denotes To distinguish the variation of LWS in the upstream and downstream of buildings, the K LWS values are separately calculated for the two directions in following subsections.
T127 21251-21408 Sentence denotes Fig. 10 displays the calculated K LWS values in the upstream low wind speed (ULWS) zones of the 'lift-up' buildings and the control building (red dash line).
T128 21409-21560 Sentence denotes Except for models M2 and M3, K LWS values in the ULWS zones of the 'lift-up' buildings are smaller than in the ULWS zones of the control building (CB).
T129 21561-21730 Sentence denotes The higher K LWS value of the CB than of 'lift-up' buildings is attributed to the difference between the LWS zones formed upstream of the 'lift-up' buildings and the CB.
T130 21731-21920 Sentence denotes In general, there are two LWS zones formed upstream of the CB, which is a building without 'lift-up' design, one next to the windward side, and the other far upstream of the building [20] .
T131 21921-22075 Sentence denotes However, the LWS zone far upstream is not visible for the CB in Fig. 4(b) because it was formed outside the measurement area owing to the strong backflow.
T132 22076-22282 Sentence denotes On the other hand, leakage of the downwash flow through the 'lift-up' area has weakened the backflow, and subsequently forms the second LWS zone in the far upstream of measurement area, as shown in Fig. 6 .
T133 22283-22438 Sentence denotes It should be noted that the wind flow through the 'lift-up' area not only creates the second LWS zone but also controls the K LWS values in the ULWS zones.
T134 22439-22777 Sentence denotes Higher wind blockages induced by shorter cores with larger areas tend to stagnate more air on the windward side of the building and produced smaller K LWS values as observed for model M7. 'Lift-up' buildings with taller cores with smaller AP values, on the other hand, produce higher K LWS in the ULWS zone such as in the M2 and M3 cases.
T135 22778-22902 Sentence denotes The 'lift-up' core height has a more influence on the K LWS values in the ULWS zone than the core area, as shown in Fig. 10.
T136 22903-23041 Sentence denotes Fig. 11 further substantiates the greater influence of the 'lift-up' core height on the K values and corresponding areas of the ULWS zone.
T137 23042-23248 Sentence denotes Taller 'lift-up' cores reduce considerably the size of areas with lower K values and are sometimes able to eliminate undesirable low wind speeds completely in the upstream direction of a 'lift-up' building.
T138 23249-23446 Sentence denotes No areas with K < 0.4 found in the ULWS zone for model M3 is an example of the effectiveness of taller cores with smaller core areas to minimize stagnated air in the upstream of 'liftup' buildings.
T139 23447-23550 Sentence denotes Fig. 12 displays the K LWS values in the DNLWS zone calculated only for the tested 9 lift-up buildings.
T140 23551-23718 Sentence denotes The K LWS value cannot be calculated for the control building (CB) as no LWS area (i.e., an area with K < 0.7) is formed next to the leeward sides of the CB (Fig. 5) .
T141 23719-23864 Sentence denotes The absence of DNLWS zone of the CB is attributed to the steady horseshoe vortex generated by the strong downwash along the front face of the CB.
T142 23865-24027 Sentence denotes The steady horseshoe vortex of the CB wraps firmly around the base of the building and prevents the formation of a DNLWS zone on the leeward side of the CB [20] .
T143 24028-24180 Sentence denotes The horseshoe vortices in each of the 'lift-up' buildings are, on the other hand, weaker because of the downwash flow passes through the 'lift-up' area.
T144 24181-24394 Sentence denotes As a result, an LWS zone appear next to the leeward side of the 'lift-up' buildings, which have smaller K LWS values than the K LWS values obtained in the pedestrian-level wind field on the leeward side of the CB.
T145 24395-24533 Sentence denotes In fact, the calculated K LWS value of the CB is 0.85 and thus it does not appear in Fig. 12 , which has a set maximum K LWS value of 0.7.
T146 24534-24645 Sentence denotes In addition, Fig. 12 reveals that the 'lift-up' core height further reduces the K LWS values in the DNLWS zone.
T147 24646-24822 Sentence denotes It is reasonable to link the reduced K LWS values to the increase of downwash passing through the taller 'lift-up' areas, which further weakens the horseshoe vortex generation.
T148 24823-24956 Sentence denotes Fig. 13 displays the variation of the area within a specific contour line (AP cum ) in the DNLWS zone with the corresponding K value.
T149 24957-25098 Sentence denotes It should be noticed that Fig. 13 does not show data related to the control building (CB) as its K values in the DNLWS are not less than 0.7.
T150 25099-25298 Sentence denotes In other words, Fig. 13 depicts that the most of 'lift-up' buildings, generally, corresponds to smaller K values (such as K < 0.4) when comparing to higher K values (K > 0.7) corresponding to the CB.
T151 25299-25423 Sentence denotes Moreover, AP cum values increase considerably with the 'lift-up' core height, especially when K values are smaller than 0.6.
T152 25424-25699 Sentence denotes Furthermore, a distinct increasing trend of AP cum is identified with the increase of 'lift-up' core area from the smallest (AP ¼ 9%) to moderate (AP ¼ 25%) values but such an increasing trend is interrupted as the core area increases from moderate to the largest (AP ¼ 49%).
T153 25700-25816 Sentence denotes In fact, larger core areas (AP ¼ 49%) are linked to the smaller AP cum value under the condition that 0.7 < K < 0.4.
T154 25817-26003 Sentence denotes The decrease of AP cum with larger core areas may have resulted from the UNLWS zone shifted inside the 'lift-up' area rather than stretched into the downstream direction of the building.
T155 26004-26124 Sentence denotes Therefore, a part of the DNLWS zone within the 'lift-up' area is not counted in the calculation of AP cum (see Fig. 6 ).
T156 26125-26263 Sentence denotes The inward expansion of the LWS zone is further analysed in the section focusing on the distribution of wind speeds in the 'lift-up' area.
T157 26264-26476 Sentence denotes Details of the distribution of pedestrian-level wind speeds in the 'lift-up' area are important in determining the comfort level and safety of people who use the 'lift-up' area for various purposes (see Fig. 1 ).
T158 26477-26607 Sentence denotes For example, high wind speeds in the 'lift-up' area may cause walking instabilities and ultimately cause to lose the body balance.
T159 26608-26813 Sentence denotes Consequently, knowledge of the wind speed distributions in the 'lift-up' area provides the guidance for positioning the building entrances in order to prevent the high wind speed from worrying pedestrians.
T160 26814-26874 Sentence denotes Low wind speeds, eventually lead to inadequate air Fig. 11 .
T161 26875-27136 Sentence denotes The distribution of normalized mean wind speed ratio (K) with the corresponding normalized area (AP cum ) of the ULWS zone for the 9 'lift-up' buildings and the control building (CB). ventilations to cause outdoor thermal discomfort of people in 'liftup' areas.
T162 27137-27302 Sentence denotes Moreover, the prevailing low wind speed could lead to accumulation of air pollutants in the 'lift-up' area, exposing people in lift-up areas to harmful health risks.
T163 27303-27518 Sentence denotes Fig. 14 shows the distribution of K values in the 'lift-up' areas of the 9 'lift-up' building models to reveal the influence of the 'lift-up' core dimensions on the pedestrian-level wind field in the 'lift-up' area.
T164 27519-27657 Sentence denotes For example, shorter cores with smaller core areas create larger high wind speed zones, which cover a major portion of the 'lift-up' area.
T165 27658-27783 Sentence denotes On the other hand, low wind speeds prevail in the 'liftup' areas corresponding to the cores with the largest area (AP ¼ 49%).
T166 27784-28062 Sentence denotes Moreover, the cores with the smallest area (AP ¼ 9%) results in the low wind speed zone having a width approximately equal to the 'lift-up' core but in the 'lift-up' areas where the cores have larger areas (AP ¼ 25% and 49%) then the low wind speed zone is wider than the cores.
T167 28063-28346 Sentence denotes The low wind speed zones at the leeward side of the largest core (AP ¼ 49%), on the other hand, expand laterally rather than stretch downstream, which could explain the high K LWS values and smaller AP cum values corresponding to the buildings with the largest core, as seen in Figs.
T168 28347-28357 Sentence denotes 12 and 13.
T169 28358-28532 Sentence denotes The 'liftup' core dimensions not only modify the pedestrian-level wind speed distribution but also define the location where the maximum and minimum wind speeds are observed.
T170 28533-28725 Sentence denotes The maximum wind speeds in the 'lift-up' area of model M1 are found near the upstream corners of the building, while the maximum wind speeds in model M6 exist on the lateral sides of the core.
T171 28726-28886 Sentence denotes In the extreme case, the location of the maximum wind speed may lie outside of the 'liftup' area, as seen in the models M8 and M9, which have larger core areas.
T172 28887-29107 Sentence denotes The distribution of pedestrian-level wind speeds in the 'lift-up' area can be employed to indicate appropriate 'lift-up' dimensions in terms of providing acceptable pedestrian-level wind conditions in the 'lift-up' area.
T173 29108-29273 Sentence denotes The acceptable wind speeds at a given location depend on several factors such as the prevailing wind speed, air temperature, physical activities, and clothing [13] .
T174 29274-29500 Sentence denotes Since the scope of the present study is limited to determining the effects of wind speeds on pedestrian comfort and safety, only a criterion based on the mean wind speed is presented to select appropriate 'lift-up' dimensions.
T175 29501-29770 Sentence denotes The selected criterion considers K values within the range of 0.7e1.3 as acceptable wind conditions by assuming K < 0.7 indicates undesirable low wind speeds that cause the outdoor thermal discomfort and K > 1.3 results in pedestrian discomfort due to high wind speeds.
T176 29771-30019 Sentence denotes Since residential building sites usually have areas allocated for kids' playing areas, or sitting areas, the less perturbation concept, and hence the selected acceptable K value range, is reasonable and practical for the building design evaluation.
T177 30020-30227 Sentence denotes However, the selected comfort criterion is arbitrary such as the criterion used by Ref. [22] and only intends to demonstrate how to select appropriate lift-core dimensions based on a given comfort criterion.
T178 30228-30512 Sentence denotes To achieve a higher accuracy in determining 'lift-up' core dimensions and to compatible with the prevailing wind conditions, it is advisable to employ a comprehensive comfort criterion together with meteorological data rather than a simple criterion similar used in the current study.
T179 30513-30733 Sentence denotes Fig. 15 displays the percentages of the areas (AP acp ), which is the area with acceptable wind conditions normalized with respect to the usable plan area of the building (i.e., 1-AP) for the tested 9 'liftup' buildings.
T180 30734-30927 Sentence denotes As shown in Fig. 15 , model M3 has the most appropriate 'lift-up' dimensions to produce the largest area (AP acp > 50%) with acceptable wind conditions (i.e., K values in the range of 0.7e1.3).
T181 30928-31090 Sentence denotes In contrast, model M7, which has the shortest core with the largest area (h ¼ 3 m, AP ¼ 49%) has the smallest area with acceptable wind conditions (AP acp ¼ 11%).
T182 31091-31296 Sentence denotes Under the definition of acceptable wind conditions adopted in this study, the smallest core (AP ¼ 9%) yields, in general, a better wind environment in the 'liftup' area with AP acp values greater than 25%.
T183 31297-31608 Sentence denotes The cores with larger areas, such as AP ¼ 25% and AP ¼ 49%, fall short of achieving the acceptable pedestrian-level wind environment in the 'lift-up' area, and the worst conditions are found for models M7, M8, and M9, which have the areas with acceptable wind speeds less than 20% of the useable 'lift-up' area.
T184 31610-31763 Sentence denotes In the present study, the pedestrian-level wind fields around 'lift-up' buildings were systematically investigated through a series of wind tunnel tests.
T185 31764-31911 Sentence denotes The influence of the 'lift-up' core dimensions was determined by testing 9 'lift-up' buildings with different 'liftup' core heights and core areas.
T186 31912-32311 Sentence denotes The investigation used mean wind speeds measured at the 10 mm height (i.e., 2 m height in full scale), and the normalized mean wind speed ratio (K) to analyse: (1) the overall features of the pedestrian-level wind environment around the 'lift-up' buildings, (2) the distribution of high and low wind speeds near the 'lift-up' buildings, and (3) the distribution of wind speeds in the 'lift-up' area.
T187 32312-32551 Sentence denotes Moreover, a control building of the same overall dimensions but without a 'lift-up' core was tested using the same wind-tunnel setup, and the results were compared to identify any wind conditions resulting from the 'lift-up' configuration.
T188 32552-32627 Sentence denotes Based on the wind tunnel test results, the following conclusions are drawn:
T189 32628-32795 Sentence denotes (1) A 'lift-up' building modifies its surrounding wind environment differently than a building without 'lift-up' design (the control building) with similar dimensions.
T190 32796-33081 Sentence denotes The flow modifications include (1) increases in area and magnitude of high wind speed (HWS) zones, (2) the formation of a pronounced low wind speed (LWS) zone on the leeward side of the 'liftup' building, and (3) a weakened LWS zone in the upstream direction of the 'lift-up' building.
T191 33082-33188 Sentence denotes All of these modifications are the direct results of the wind flow that passes through the 'lift-up' area.
T192 33189-33632 Sentence denotes Therefore, it is possible to maintain the desired wind environment near a 'lift-up' building by controlling the amount of wind flow passing through the 'lift-up' area or in other words, by adjusting the 'lift-up' core dimensions. (2) The area-averaged high wind speed ratio (the K HWS value) of a 'lift-up' building is considerably higher than of a building without 'lift-up' design due to the increases in size and intensity of the HWS areas.
T193 33633-33772 Sentence denotes The K HWS value increases appreciably with the increase of 'lift-up' core height and slightly decreases with the increase of the core area.
T194 33773-33909 Sentence denotes The effect of the 'lift-up' height is more pronounced for larger core areas (e.g. AP ¼ 49%) than for smaller core areas such as AP ¼ 9%.
T195 33910-34308 Sentence denotes Consequently, the 'lift-up' core dimensions that consist of a moderate core area with the tallest core height (AP ¼ 25%, h ¼ 9 m) would result in the highest accelerated wind flows near a 'lift-up' building. (3) The area averaged low wind speed ratio (the K LWS value) of the two low wind speed (LWS) zones around 'lift-up' buildings are smaller than the K HWS value of a building 'lift-up' design.
T196 34309-34466 Sentence denotes Moreover, the core area has a greater influence on generating smaller wind speeds in the upstream low wind speed (ULWS) zones than the 'lift-up' core height.
T197 34467-34607 Sentence denotes The 'liftup' core height is effective in reducing the size of the ULWS areas of 'lift-up' buildings with larger cores areas (e.g. AP ¼ 49%).
T198 34608-34736 Sentence denotes The increase of both height and area of the core decreases wind speeds in the downstream near-field low wind speed (DNLWS) zone.
T199 34737-35201 Sentence denotes However, K LWS values in the DNLWS zone are slightly increased for the largest core size of AP ¼ 49% due to the expansion of the LWS area from the leeward side to the lateral sides of the core. (4) Appropriate lift-up dimensions can be determined by combining a wide range of wind speed data and meteorological wind data with a selection criterion, which depends on the required wind conditions so as to increase or decrease the wind speeds near lift-up buildings.
T200 35202-35480 Sentence denotes As the wind tunnel test results indicate that the 'lift-up' core height is the most influential parameter, the most appropriate 'lift-up' design can be determined by first selecting the core height and then choosing a suitable core area from examining the wind tunnel test data.