Design Wind Pressures Research Articles

Test study on performance of U80 standardized glass curtain wall system

In order to study the air infiltration performance, water penetration performance, structural performance under wind pressure and seismic inter-story drift performance of U80 standardized glass curtain wall system, one full size test specimen was designed according to the actual engineering situation. The test specimen was composed of six-unit curtain walls with exposed frames and six-unit curtain walls with concealed frames. According to the specification of United Stated, the various performance of the test specimen was investigated. The results show that the rate of air leakage of the specimen is within allowable values under design pressure. No water leakage is observed when the water penetration tests with static and dynamic pressure tests. During the structural performance tests at 100% design wind pressure, the deflections of framing members as well as glass panels are all within the allowable deflection limits. No breakage is observed under the 150% design wind pressure. Permanent deformations of framing members remain less than 0.1% of clear span. After 3 cycles of elastic and inelastic inter-story drift performance tests, no damage is observed. The U80 standardized glass curtain wall system has great air infiltration performance, water penetration performance, structural performance and seismic inter-story drift performance. And it can be used in the practical engineering.

Comparative analysis of self supporting steel chimney subjected to wind load by IS: 875 (part-3) – 1987 and IS: 875 (part-3) – 2015

Steel chimneys are used for releasing smoke in various power plants, oil and gas industries. Steel chimneys are generally subjected to static and dynamic loads. Geometry of steel chimney like height, diameter at top and bottom plays key role when structure subjected to lateral loading like wind or earthquake. In this study static analysis is conducted on a self-supporting steel chimney of height 90 m subjected to wind load located in Vijayawada for categories 1, 2, 3 and 4. For comparison of IS: 875 (part-3)-1987 to IS: 875 (part-3)-2015, variation of Terrain, height and structure size factor (K2), Design wind speed (VZ), Design wind pressure (PZ), segment moment with respect to chimney base and corresponding segment base of all categories are considered in this study, as basic dimensions of chimney, basic wind speed (Vb), probability factor (K1) and topography factor (K3) are same for both codes. From the study it is found that K2,VZ,PZ, segment moment with respect to chimney base and segment base of all categories are more for IS: 875 (part-3)-2015 than IS: 875 (part-3)-1987. VZ, PZ, segment moment with respect to corresponding segment base of all categories for IS: 875 (part-3)-2015 increases because of Importance factor for cyclonic region (K4).

Comparative Study of Wind Pressure Variations on Rectangular Buildings using Python Programming

In this research article an attempt has been made to analyse the design wind pressure on the rectangular buildings using Python programming. For this purpose, design wind pressure is calculated and compared using IS 875 (Part 3) 1987 and the revised code IS 875 (Part 3) 2015. The concept have been applied to three different building heights i.e. 20, 40, and 60 m having same plan 1010 m2. It has been observed that the impact of wind pressure on the building rises with the building height along with the fact that the design wind pressures obtained from revised code show more pressures in comparison to the old one. Therefore, the design based on the revised code will be more close to the reality as it incorporates risk factor, directionality factor, area averaging factor, and combination factors. Also, the module developed for wind loads can be readily used by the researchers/designers for the better understanding of programming and the design loads.

Review on Analysis and Design of RCC Cooling Tower Using STAAD-Pro

Abstract: Cooling tower is a device which converts hot water into cold water due to direct air contact. It works on the temperature difference between the air inside the tower and outside the tower. Natural draft cooling tower is one of most widely used cooling tower. Hyperbolic shape of cooling tower is usually preferred because of its strength and stability and large available area at the base due to shape. As it is very important structure in nuclear and chemical plants, it should be continuously assessed for its stability under selfweight, and lateral loads like wind load and earthquake load. Therefore, cooling towers have been analyses for wind load by assuming fixity at the shell base. The wind loads on these cooling towers have been calculated in the form of pressures by using the circumferentially distributed design wind pressure coefficients as given in IS: 11504 -1985 code along with the design wind pressures at different levels as per IS:875 (Part 3) - 1987 code. These towers with very small shell thickness are exceptional structures by their sheer size and sensitivity to horizontal loads. The present study deals with the analysis of cooling tower maximum displacement, support reactions, support moments, stresses and bending moments in plates due to seismic loading, wind loading and dead load i.e., its self-weight on a hyperbolic cooling tower is continuous function of geometry. Keywords: Cooling Tower, Wind Load, Stresses and Moments

Estimation of directional design wind speeds via multiple population genetic algorithm

The implementation of the probability analysis method on extreme wind loads considering the directionality and uncertainties of the wind load effect coefficients and wind speeds can yield accurate design wind loads. However, it is difficult to popularize this method among structural designers because its theory and calculation process are complicated. The directional design wind speeds for a given city, which are more suitable in the commonly used simplified method for estimating the wind loads (i.e., the sector-by-sector method), are obtained in this study via multi-parameter optimization. A multiple population genetic algorithm program is established for optimization based on the time histories of the wind pressure coefficients obtained from numerous wind pressure taps of different rigid models. For different structural aerodynamic characteristics, the proposed directional design wind speeds can be combined with the sector-by-sector method to obtain results that are closest to the overall reference values of the design wind pressures of all pressure taps under a certain safety guarantee. The applicability, economy, and safety of the sector-by-sector method with the proposed directional design wind speeds are discussed in comparison to other simplified estimation methods using examples of Des Moines, IA, USA, and Shanghai, China, for non-typhoon and typhoon-prone climates, respectively.

The potency of IS 875 (Part 3) 2015 code provisions on A-type trusses in the cyclonic regions of India

SP 38:1987 Handbook for the design of trusses have been widely used by the structural engineers in India. The designs were recommended 1987 version wind load provisions. The revised version of IS 875 was released in 2015 with certain additional recommendations for computation of design wind pressures in static load consideration. In this paper comparative analysis was made on A-Type trusses for 9m and 24 m spans with STAAD Pro (8i) software to determine the extent of increase of truss forces. It was inferred that the trusses forces for smaller spans are more increased when compared to larger spans.

Comparisons of design wind pressures on roof-mounted solar arrays between wind tunnel tests and codes and standards

The current codes and standards concerning wind loads on roof-mounted solar panels are discussed and summarized. Wind pressures on flat- and slope-roof-mounted solar arrays obtained from wind tunnel tests are compared with the recommended design values in ASCE 7-16 and JIS C 8955: 2017. Different parameters, including building side ratio, aspect ratio and parapet height, are examined. Results show that the largest wind pressures on flat-roof-mounted solar panels of all zones in ASCE 7-16 tend to be 10% to 26% smaller than the experimental results when normalized tributary area An is larger than 103. Uplift wind forces on flat-roof-mounted solar panels in downstream regions obtained from experiments can be larger than the recommended values in JIS C 8955: 2017 for adverse wind, but downward force coefficients are basically smaller than those in JIS C 8955: 2017 for fair wind. 40% to 60% increase on the pressure equalization factor for slope-roof-mounted solar panels is suggested for the potential refinement of ASCE 7-16 based on this study. Meanwhile, proposed pressures of slope-roof-mounted solar panels in JIS C 8955: 2017 might be too conservative according of experimental results.

Uncertainties in prediction of local peak wind pressures on mid- and high-rise buildings by considering gumbel distributed pressure coefficients

Design wind pressures for components and cladding (C&C) are key design parameters. For mid- and high-rise buildings, design pressures for C&C are often evaluated from wind tunnel tests, especially when building geometries are irregular or surrounding environments are complex. Wind tunnel data acquisition and analysis approaches both contribute to uncertainties of predicted design wind pressure coefficients. Although there is still debate on the most appropriate probability distribution to fit the peak pressure data and the best method to obtain the design pressures, Gumbel distribution and the generalized least square method (also known as BLUE) are widely considered and adopted in engineering practices. Wind tunnel test durations and number of peaks used in the extreme value analysis also influence peak pressure predictions. Some recent studies investigated the effect of these factors for predicting design wind pressures on low-rise buildings, which typically have a model scale of about 1:30 to 1:100. It is not clear whether observations in these studies are directly applicable to mid- and high-rise buildings or stadiums, which typically have a much smaller model scale (~1:400). For this purpose, a long duration wind tunnel test was conducted by employing a model with a generic high-rise building geometry. The desired design percentile of extreme pressures is briefly discussed. The effect of test durations and number of peaks involved in the extreme value analysis was investigated. Lastly, this study investigated the influence of inconsistency between the averaging time of design wind speeds and the target reference periods, in which the design pressure coefficients were expected to occur, on the prediction of design wind pressures. The results suggest that an adequate combination of test durations and number of peaks used in the extreme value analysis reduces uncertainties significantly and results in appropriate design wind pressures for engineering applications.

Load carrying capacity of greenhouse covering films under wind action: Optimising the supporting systems of greenhouse films

The load carrying capacity of a typical greenhouse film used as covering for a Gothic-type greenhouse was investigated under negative wind pressure. The film was simulated as a membrane through appropriate shell elements and analysed with the finite element method (FEM). The design wind pressures were calculated based on the provisions of Eurocode 1 and EN13031. The FEM model boundary conditions corresponded to the real film supporting conditions of an industrial type greenhouse structure. The film was pre-tensioned at its initial state in the longitudinal direction, and then subjected to uniform negative wind pressure. The nonlinear elastic analysis with large deformations results showed that, as the wind pressure increases, the principal tensile stress in the film increases and gradually reaches the material stress at yield value. Plastic deformation is expected to take place and the film loses its capacity to return to its initial undeformed state. Consequently, the plastically deformed film loses its prestress state and its proper elastic behaviour. Depending on the final wind pressure intensity and the degradation condition of the film, premature failure may therefore occur. The analysis revealed that the film failure is due to insufficient supporting of the film on the steel structure. This behaviour was verified by examining a real greenhouse film failure case. Various supporting systems of the greenhouse covering films with additional intermediate supports were analysed and optimal design solutions are proposed. The proposed optimised supporting systems of greenhouse films covers a gap in the current European standard for greenhouse design.

Study of Reserved Strength Capacity of Concrete Shell

Hyperbolic cooling towers have become the design standard for all natural-draft cooling towers because of their structural strength and minimum usage of material. The hyperbolic shape is particularly suited to cooling tower construction as the wide base provides a large space for the water and cooling system. As the tower widens out at the top, it supports the turbulent mixing as the heated air makes contact with the atmospheric air. Hyperbolic cooling tower is a tall structure with shells subjected to dead load and wind load. In absence of ground motion, wind becomes the major factor. In this study, 2 major models are studied with I and V column support. Each model is further divided into 2 models, i.e. one with SHELL element and another with SOLID element. All models were modelled and analyzed in ANSYS. The wind loads on these cooling tower have been calculated in the form of pressure by using the circumferentially distributed design wind pressure coefficients as given in IS: 11504 - 1985 code along with the design wind pressures at different levels as per IS: 875 (Part 3) - 1987 code. The analysis has been carried out using 8 noded shell element (SHELL281), 8 noded solid element (SOLID185) and 20 noded solid element (SOLID 186).

Assessment of ASCE 7-10 for wind effects on low-rise wood frame buildings with database-assisted design methodology

The design wind pressure for low-rise buildings in the ASCE 7-10 is defined by procedures that are categorized into the Main Wind Force-Resisting System (MWFRS) and the Components and Cladding (C&C). Some of these procedures were originally developed based on steel portal frames of industrial buildings, while the residential structures are a completely different structural system, most of which are designed as low-rise light-frame wood constructions. The purpose of this study is to discuss the rationality (or irrationality) of the extension of the wind loads calculated by the ASCE 7-10 to the light-frame wood residential buildings that represent the most vulnerable structures under extreme wind conditions. To serve this purpose, the same approach as used in the development of Chapter 28 of the ASCE 7-10 that envelops peak responses is adopted in the present study. Database-assisted design (DAD) methodology is used by applying the dynamic wind loads from Louisiana State University (LSU) database on a typical residential building model to assess the applicability of the standard by comparing the induced responses. Rather than the postulated critical member demands on the industrial building such as the bending moments at the knee, the maximum values at the critical points for wood frame buildings under wind loads are used as indicators for the comparison. Then, the critical members are identified through these indicators in terms of the displacement or the uplift force at connections and roof envelope. As a result, some situations for each of the ASCE 7 procedures yielding unconservative wind loads on the typical low-rise residential building are identified.

ANALYTICAL STUDY OF SHELL THICKNESS VARIATION MODELS FOR NATURAL DRAUGHT COOLING TOWER ON VERTICAL PILE FOUNDATION

Natural Draught Cooling Tower (NDCT) is an important and essential structure in nuclear and thermal power stations as it contributes both to the energy efficient output and balance to an environment. From the structural point of view, high rise concrete structure is subject to various dynamic loads in an unfavorable way. Wind loading is important in NDCT design for structural safety, elastic stability, vibration properties and the initiation of concrete cracking in comparison to other structures. The behavior change of NDCT due to the variation of shell thickness when NDCT rested on a vertical pile foundation is very interesting. Therefore, the objective of the present paper is to briefly present the finite element modeling and analytical study of NDCT with twenty-seven different types of shell thickness models for the same height of NDCT. Each model is identified based on the separate case number from 1 to 27, and FEM analysis was carried out using Staad Pro-V8i software considering gravity loads, wind load. Further, design wind pressure at different levels along the height of NDCT was calculated as per IS 875 (part 3) 1987 code after applying Interference factor (IF) of 1.573. Due to the lack of wind study findings, the IF was considered as 1.573 while the maximum value of IF was 1.43 as per BS: 4485 (1975). Distribution of wind pressure at each level of NDCT in the circumferential direction was as per IS11504-1985. The overall study identified optimum shell thickness varying models to obtain the optimum foundation as well as super-stable structure. Further, the comparison was made between the guest and peak factor method and found that wind load due to gust factor method was critical and therefore recommended.

Analysis of Wind Effect on High-Rise Building for Different Terrain Category

This paper analyzed the effect of wind loadings on high-rise building for different terrain categories. The wind speed and design wind pressure for the different terrain categories adopted for this study were calculated as per logarithmic wind profile equation and BS6399-2:1997 respectively. Also, the nodal displacement of a 3D high-rise building model with reference to the calculated design wind loads were performed using finite element analysis software(STADDPROV8I). From the result obtained, it was shown that Terrain category IV when compared to other terrain categories recorded lower wind speed and pressure from the ground to a height of about 10m. The writers also observed that at greater terrain category(TC4), the wind speed and pressure tends to be much higher at the top floors(10m-48m) of the high-rise building whereas, terrain categories (TC3, TC2, TC1) recorded lower wind speed and pressure at that same height(10m-48m). this disparity however was discovered to be due to a phenomenon known as gust effect. Also, the nodal displacement for the different terrain category (TC4, TC3, TC2 and TC1) on each floor of the high-rise building increased uniformly in respective pattern as the height of the 3D model increases. In conclusion, the authors therefore remark “the greater the terrain category, the lowest is the wind speed in the roughness sub layer and the longer height it takes to reach gradient wind speed”.

Analysis of Wind Effect on High-Rise Building for Different Terrain Category

This paper analyzed the effect of wind loadings on high-rise building for different terrain categories. The wind speed and design wind pressure for the different terrain categories adopted for this study were calculated as per logarithmic wind profile equation and BS6399-2:1997 respectively. Also, the nodal displacement of a 3D high-rise building model with reference to the calculated design wind loads were performed using finite element analysis software(STADDPROV8I). From the result obtained, it was shown that Terrain category IV when compared to other terrain categories recorded lower wind speed and pressure from the ground to a height of about 10m. The writers also observed that at greater terrain category(TC4), the wind speed and pressure tends to be much higher at the top floors(10m-48m) of the high-rise building whereas, terrain categories (TC3, TC2, TC1) recorded lower wind speed and pressure at that same height(10m-48m). this disparity however was discovered to be due to a phenomenon known as gust effect. Also, the nodal displacement for the different terrain category (TC4, TC3, TC2 and TC1) on each floor of the high-rise building increased uniformly in respective pattern as the height of the 3D model increases. In conclusion, the authors therefore remark “the greater the terrain category, the lowest is the wind speed in the roughness sub layer and the longer height it takes to reach gradient wind speed”.

Optimizing the architectural layouts and technical specifications of curtain walls to minimize use of aluminium

During the recent decades it has become common to enclose large buildings with lightweight, weathertight walls that hang, like curtains, from the floor edges. The frames of these curtain walls are, usually, extruded aluminium – a material whose production is highly energy-intensive. Although means of enhancing the thermal performance of building envelopes have been scrutinized, comparatively little attention has been given to the cost and embodied energy savings that can be achieved through efficient structural design. No guidelines for efficient use of aluminium in a curtain wall have been published, and architects therefore have not known the impact that their decisions have upon the facade's material content.In this study more than 1000 unique curtain wall systems have been optimized numerically, each one to a different set of design criteria, and the results show the extent to which aluminium content is influenced by floor height, locations of supports, number of horizontal members per panel, width of the extrusions, spacing between mullions, design wind pressure, and the minimum allowable thickness of aluminium. The conditions in which the amount of metal required to construct a window wall (glazing spanning between two floors) might be less than that required for a curtain wall (an uninterrupted, multi-floor shroud), also have been explored. The results show that substantial metal savings – reductions of 40% or more – can be realized by making modest changes to the layout geometries and specifications that are in common use. The value of the corresponding construction cost reductions is significant: in the worldwide construction market, the potential savings are in billions of dollars per year.The practical steps that an architect and specifier should take in order to reduce metal content in a curtain wall are set out in a list. These savings are separate from, and in addition to, any that might be attained by optimizing the cross-sectional shapes of extrusion profiles.Unlike improvements in a facade's thermal performance, which usually require capital investment in insulating materials for returns that accrue over decades, material-efficient design methods are free to apply, and the benefits can be enjoyed immediately.

Wind-Pressure Coefficients on Low-Rise Building Enclosures Using Modern Wind-Tunnel Data and Voronoi Diagrams.

External pressure coefficients specified in the ASCE 7-10 Standard, used to determine design wind pressures for the components and cladding of buildings, are developed from wind tunnel test data that date back 30-50 years. In recent decades, advances in pressure measurement and computer technology have made it possible to obtain simultaneous pressure records, with high sampling rates, at many more wind tunnel pressure taps than was the case in the past. This paper proposes a method to calculate external pressure coefficients using aerodynamic wind tunnel databases such as Tokyo Polytechnic University's large, publicly available database. Voronoi diagrams are used to assign tributary areas to irregularly spaced pressure taps. User-defined grids of various sizes and shapes are placed at various offsets over the building surface to perform area-averaging of the pressure time series. Considering all wind directions for which measurements are obtained in the wind tunnel, the peak pressures are determined assuming a Gumbel distribution, and are extrapolated to a standard storm duration. The external peak pressure coefficients are then plotted as functions of their corresponding area for various zones of the building enclosure to produce plots similar to the ASCE 7-10 specifications on components and cladding. Results for three gable buildings analyzed in the paper show that the current ASCE 7-10 specifications can severely underestimate the external pressure coefficients for components and cladding of low-rise buildings.

엔지니어링 PE방수.방근시트가 결합된 박스 유닛형 옥상 녹화 시스템 적용을 위한 성능평가

도심지 건물의 증가는 친환경 공간에 대한 요구를 발생시키고, 이에 따라 옥상 및 인공지반 녹화의 보급이 급속히 증가되고 있다. 본 연구는 녹화시스템의 보급 확대를 위해 공법의 단순화, 일체화, 프리훼브화 개념을 적용, 연속 토양층 형성 박스 유닛형 녹화시스템을 개발하고, 이 시스템의 주요 성능으로 부착성, 내풍성, 단열성을 평가하여 적용 가능성을 검토하였다. 부착성 및 내풍성 시험결과, 설계 풍압 및 풍속과 비교하면 100m 높이의 건물에 설치해도 안전한 것을 확인하였고, 단열성 평가를 위해 120일간 측정한 내부 온도의 변화를 분석한 결과, 개발 시스템이 연속된 토양층을 형성하여 기존 유닛박스 시스템보다 주간은 17%, 야간은 45% 우수한 단열성능을 보여 주었다. According to the increment of urban buildings, the demand of eco-environment space will be also increased. Therefore, the artificial ground green system on a roof will be supplied gradually. In this study, the concept of simplification, unification and prefabrication was widely applied to supply green system. Consequently, the box unit system with a continuous soil layer was developed, and adhesive property, wind resistance and insulation property of this system were evaluated for site application. As a results of adhesive property and wind resistance test, comparing with design wind pressure and wind velocity, this system was safe at the height of 100m building located in urban. In addition, results of temperature measurement for 120 days showed 17% higher insulation property at daytime and 45% higher insulation property at night than normal box unit system owing to continuous soil layer.

Estimation of wind load on a greenhouse and evaluation of its structural stability

Among all the loads that act on the greenhouse, wind load is the major one. In India, the basic wind speed varies from 33 to 55 m/s. Along with wind speed, wind load also depend on the geometry, height to width ratio, effective frontal area etc. So greenhouse design should be customized as per the localized wind load. 'One size fits all approach' in greenhouse design may leads to failure of the structure or being expensive. Unfortunately the standard for greenhouse design is lagging far behind in India. In this experiment, wind load for the double arch type naturally ventilated greenhouse was estimated as per IS code 875 (part 3) and IS 14462: 1997. The design wind pressure estimated to be 772 N/m 2 and wind load on the roof of the greenhouse is 222 kN (Suction) and 185 kN (Pressure). A model of the greenhouse is developed by means simulation with Finite Element Method using ANSYS 15.0 to test its stability at the calculated wind load. The truss and columns are studied with deflections and failure zones diagrams and possible failures were found out to redesign the elements.

Evaluation of Roofing Systems in Malaysia Based on MS 1553 BS 6399, EC1-1-4 and IS 875 Wind Codes

This paper evaluates the performance of different roofing sheet systems for different roof types using four different codes namely MS 1553, EC1-1-4, IS 875 and BS 6399. The maximum roof pressures using different codes (MS 1553, EC1-1-4, IS 875 and BS 6399) on critical and general area of the different roof types considering buildings with non-dominant opening, dominant opening and canopies have been evaluated. The maximum recommended wind speed in MS 1553 namely 33.5 m/s has been used as the reference for the numerical comparison. The major differences in the codes include averaging time for wind speed, terrain, reference height, and pressure coefficients. The study examines the conservativeness or not of the codes if used in the Malaysian context, even though they have been developed for a different wind climate and region. Further, the results of static test on different steel roofing sheets used in Malaysia using AS 1562.1 available as the limit state wind pressure capacities in the technical brochures are compared with design wind pressures for critical and interior regions of the roof for different wind zones. The suitability of a particular roofing sheet system for a particular wind zone is then assessed.

Wind Uplift Capacity of Foam-Retrofitted Roof Sheathing Panels Subjected to Rainwater Intrusion

Widespread damage to residential roofing systems during Hurricane Andrew in 1992 highlighted the structural inadequacy of wood roof sheathing attachment in existing Florida homes. Prior research found that retrofitting wood decks with closed-cell spray-applied polyurethane foam (ccSPF) could provide adequate wind resistance to pre-1994 roofs. However, it is unknown whether this retrofit method increases the potential for moisture to accumulate in the roof sheathing, and if so, what effect this has on the strength of the bond between the ccSPF and the wood substrate. Five full-scale roofs were subjected to natural weathering for 3 months, and 131 small-scale laboratory samples of ccSPF bonded to wood sheathing were intermittently sprayed with water and stored in a high-humidity environment for up to 16 weeks. These tests enabled systematic assessment of the effects of water leakage on ccSPF-retrofitted roof structures. The attic roofs were retrofitted with two ccSPF configurations and covered with three-tab asphalt-shingle roofing subjected to extreme leakage conditions. A control attic roof was not retrofitted with ccSPF. Moisture content and temperature were continuously monitored in the wood truss members of the roofs over 3 months of exposure to both natural and simulated rainfall conditions. At the conclusion of the exposure period, sheathing panels were harvested and subjected to wind uplift structural tests. Tensile tests were conducted on the small-scale samples after 0, 1, 2, 4, 8, 12, and 16 weeks of exposure. The results demonstrated that with extreme leakage conditions, ccSPF-retrofitted roofs experienced significant moisture buildup in the wood substrates. However, the ccSPF-retrofitted sheathing panels maintained high wind uplift failure capacities. The tensile tests on small-scale samples demonstrated as much as 54% reduction in tensile strength of the wood-ccSPF bond with time as a result of moisture-induced bond degradation, although the strength of this bond after 16-week exposure remained above design wind pressures by a minimum factor of 3.75.