City Development and Cladding Design
Implication of city growth on wind-induced loads for cladding design
Presented on October 13, 2022 at Facade Tectonics 2022 World Congress
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High-rise buildings in growing cities could become more vulnerable to variations in wind flow due to the continuous changes in urban topology. The aerodynamics become more complex due to the interaction with the evolving surrounding environment and can lead to changes in wind pressure on building cladding. In this paper, boundary layer wind tunnel tests are conducted to investigate the impact of city growth on the cladding load of a typical rectangular tall building model. The city growth is represented by five different generic surrounding configurations, varying in height ratios compared to the study building. The configuration includes an isolated case scenario with 0% in surrounding height ((0000SH) , with 25% (0025SH), 50% (0050SH), 75% (0075SH) and 100% (0100SH) of height H surrounding, respectively where H is the height of the building. Based on the study analysis, city growth has a different impact on structural and non-structural elements from wind hazard perspectives. The overall recorded mean wind pressures are reduced while fluctuations within these pressures are increasing as the urban environment becomes denser creating wake-induced turbulence. Due to Bernoulli and Venturi's effects, increases in the local cladding pressures are observed for certain cases. The results show a 40% and 20% increase in the negative peak pressures Čp for cases 0025SH and 0050SH respectively compared to the isolated case scenario 0000SH at an Angle of Attack (AoA)=120° and 90° which subject the building to higher risks of cladding failure. This consideration is not currently included in the national building codes, which affects the current design approaches and sensitivity analysis for new or existing high-rise developments. This research provides additional critical information for cladding design that can serve as an extension to wind tunnel studies and numerical simulations for the design community.
As the city grows, the wind phenomenon becomes more complex, changing directions according to the obstructing element. This variation in wind flow is due to the interaction of fluid flow with the built environment (Holmes 2018). As a result, the change in the urban topology can either increase or decrease both the global wind loads on the building structure and the local peak pressures acting on the nonstructural components such as cladding elements. Several studies were performed on the effect of existing surrounding buildings on high-rise building loads. It started in the early seventies after the collapse of the three natural draft cooling towers at Ferrybridge, England in 1965 which was highly correlated to the existing built environment (Amrit 1980). Since then, several experimental and numerical studies available in the literature were investigating and assessed the behavior of high-rise buildings under different urban topologies. (Bailey and Kwok 1985), (Taniike 1991) and (Khanduri et al. 2000) performed a series of boundary layer wind tunnel tests to study the dynamic response of a square high-rise building under the effect of a neighboring twin building. Most of the past mentioned studies focused mainly on the overall wind loads and the wind-induced structural responses due to the surrounding effect aiming for structural design. However, only a few pieces of literature were found supporting the design of nonstructural elements for the effect of future buildings on the built environment. For instance, (Irwin 1998) studied the variation in cladding pressure due to the effect of future buildings and developed a methodology to adjust wind tunnel results to compensate for the obtained uncertainty. They reported high suction near the ground and at the top corner of the studied building. (Surry and Djakovich 1995) explored the highest peak suctions developed on the building surfaces of an isolated case only and their relation to the building geometry and turbulence intensity. (Hui et al. 2013) also, investigate the interference effects between two high-rise buildings with the same heights but different shapes and arrangements, the results show an increase in the negative pressures for some cases up to 50% larger than in the isolated case and a decrease of around 30% in other cases depending on the wind direction.
On the other hand, computational fluid dynamics (CFD) simulations were also utilized to predict wind-induced responses in high-rise buildings. (Dagnew and Bitsuamlak 2014), (Elshaer et al. 2016) and (Elshaer et al. 2017) evaluated the aerodynamic response of a typical tall building with and without surrounding buildings (i.e. isolated building, two adjacent buildings, complex surrounding buildings) using computational fluid dynamics. They investigated different numerically generated inflow boundary conditions to assess their suitability for Large Eddie Simulations (LES).
However, previous research was limited to a defined number of surrounding buildings with fixed heights not taking into consideration the predicted city growth which did not represent the real development of a surrounding city. Therefore, in this paper, boundary layer wind tunnel tests were performed to investigate and evaluate the impact of city growth on the cladding load of a typical high-rise building adopted from the Commonwealth Advisory Aeronautical Research Council (CAARC) building model. The city growth is represented by different generic surrounding configurations, varying in height ratios compared to the study building. The configurations include an isolated case scenario (0000SH), and surrounding buildings of 25% increase (0025SH), and 75% increase (0075SH) in surrounding height ratios. Maximum positive and minimum negative peak pressures are presented for each tap (i) and evaluated from the cladding design point of view. A realistic case study was also introduced in this paper for further elaboration on the effect of surroundings on cladding design loads.
Experimental Setup - Model Description and Wind Profile
Wind tunnel experiments on a high-rise building with several surrounding configurations of varying height ratios were conducted at the Boundary Layer Wind Tunnel Laboratory (BLWTL I) at the University of
Test Configurations and Cases
The surrounding models were made from high-density foam of different heights, see Table 1. They cover an area around the study building of around 500m radius in full scale). They
Results and Discussion
Mean and Fluctuation Pressure Distributions
There is a significant change in the mean pressure coefficient distribution on the windward wall of the CAARC building with the increase in surrounding
To relate previous observations from this study to an actual building, we compared the available cladding wind tunnel results (1983 and 2020) of a 174m. (570 ft.) tall building. The
The previous study aimed to investigate the impact of city growth on high-rise buildings, focusing on cladding loads. High-Frequency Pressure Integration (HFPI) tests were conducted at the Boundary Layer Wind
The current study discusses several topics related to urban city development and the effect of generic configurations development on non-structural cladding elements of tall buildings. For future research, the following
Rights and Permissions
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