Aerodynamic Loading Due to Non-Synoptic Wind Systems

Probabilistic serviceability-performance assessment of tall mass-timber buildings subjected to stochastic wind loads: Part I - structural design and wind tunnel testing

With the advancement in material science, construction technology and structural analysis, a new building code was essential to keep pace with technological advantages. Recently introduced BNBC 2020 bridges the gap largely. A very basic change in lateral loading provision has occurred in the new code, which accounts for several newly defined parameters. For wind analysis, the new code introduces 3-second gust velocity as basic wind speed, wind pressure application in four cases that accounts for eccentricity. It considers topographic and internal pressure effect. A new seismic zoning is introduced in BNBC 2020 with revised PGA values and spectral acceleration. The code also introduces seismic design category and revised response reduction factor. All these changes will affect the design practice. To understand and compare lateral loading in different zones, a FEA of 20 storied RC building with and without core shear wall was analyzed using ETABS V18. The comparison shows that Rajshahi (Zone I) has lowest wind and seismic loading, Chattogram (Zone III) has highest seismic and wind loading while, Dhaka (Zone II) has moderate seismic and wind loading. Wall frame building has slightly larger seismic base shear while shear wall resists major portion of base shear and reduces top story displacement and story drift greatly. The cost of construction in zone III is significantly larger than in zone I and II. In all zones shear wall building imparts economic structural solution compared to bare frame against lateral loading for 20 storied buildings and the margin of economy increases with increasing lateral loading.

Advancements in computer software and hardware technology provide a new direction for analyzing engineering problems. Recently the field of wind engineering has gained significant momentum in the computer modelling process. This paper reviews the state of the art in computational wind engineering, including the finite element method, finite difference method, and control volume technique. A portion of this paper summarizes the research in this area carried out by the authors. Computations have been made for a variety of building configurations, including normal wind flow conditions for a building with different aspect ratios, and modelling wind environmental conditions around groups of buildings. The computer modelling technique may eventually enhance the design of buildings and structures against wind loading and supplement the current design practice of using building codes and standards or performing experiments in wind tunnels. Key words: buildings, computer modelling, pressure, velocity, wind engineering, wind tunnels.

Predicting the probability of ice storm damages to electricity transmission facilities based on ELM and Copula function

PurposeThe process followed in amending building code creates problems for code users within the building industry. These problems include the need and frequency of changes made to building code, access to updated documents, method of communication, amendment interval and amendment pathway. This study aims to explore the viewpoints of building code users regarding building code amendments in New Zealand.Design/methodology/approachUsing a closed-ended questionnaire survey, this paper examined the New Zealand building code amendments by evaluating the views of experienced and relevant stakeholders within the research area.FindingsA high proportion (50.90%) of the survey participants agreed to a three-years building code amendment cycle, as against the current biannual Amendment practiced in New Zealand. Findings from the study affirmed the necessity for building code amendment and the support for free amended building code documents to the public and other building standards. The study concludes with strong support to the use of intensive research and learning gained from disasters in building code amendment in New Zealand. Implementing the code users opinions encourages disaster resilience through effective application of the building code requirements in design and construction.Originality/valueThe contribution from this study offered a unique insight into the perspectives of building code users on building code amendment in New Zealand and ways of incorporating the findings in the building code later updates to improve disaster resilience in the built environment.

Computerization of building codes and standards in connection with Building Information Modeling (BIM) represents a real challenge for the AEC industry. On one hand, building rules and regulations are written by professionals to be read and applied by people since the reasoning and interpretation ability of the human brain is unlike anything implemented in computer systems. On the other hand, a smart phone app can outperform any engineer on solving a set of linear equations. However, many tasks that are easy for engineers or human in general are surprisingly difficult for computers. Examples include interpretation and expression of code and standard provisions that are characterized by subjective and descriptive rules. The perceptual abilities of engineers certainly surpass the fastest supercomputers. This gave motivation to many researches investing the efforts in creating computable representation of the building codes and standards and their link to Building Information Modeling (BIM). This paper provides critical review of the development of computable building codes rules that can be implemented into BIM-based automated rule-checking systems. It also addresses the complexity of these knowledge systems, the problems they pose for engineers and designers, and the methods for managing and advancing them.

The field of wind science and engineering (WSE) in relation to civil engineering (CE) applications is still considered relatively young and thus has been taught only for about 50 years in some academic institutions. Therefore, it is unsurprising that there are limited wind engineering (WE) tracks within CE programs worldwide, and no semblance of a standard or ideal curricula. An adequate education in WE is paramount to future structural and civil engineers, and ultimately to academia, because natural disasters including extreme wind events have the capability to destroy our infrastructure systems, as well as threaten people’s lives and well-being. The goal of this research is to identify and propose an ideal path for WE tracks within CE that not only enhances the quality of education, but also provides equitable learning opportunities and promotes diversity and workforce inclusion. To achieve this goal, this research (1) analyzed the different CE programs that include WE tracks offered in the US, Canada, and Europe; (2) identified the academic institutions that have academic expertise and equipment critical to the study and investigation of wind events, such as atmospheric boundary layer (ABL) wind tunnels; (3) conducted a survey of all WE faculty and students doing research on these topics at Florida International University to gather information on the courses offered as well as information on what they believe could be offered or improved to enhance the curricula; (4) compared the programs that include WE tracks to provide a modernized WE curricula; and (5) proposed ideas, tools, and strategies that can be implemented to provide better curricula for students in order to enhance their education and increase research in this paramount topic, as well as ensure equitable quality education that presents equal opportunities for all.

Understanding how regional climate, and the extremes associated with it, will change over the coming decades is a vital step towards effective local adaptation. understanding of the vulnerability and risk from severe winds is derived from a number of factors, including the frequency and intensity of the hazard, community exposure and the relationship between gust wind speed and impact/loss associated with residential structures. Australian Government, through the Australian Building Codes Board (ABCB), has responsibility for maintenance of the Building Code of Australia (BCA), which establishes performance requirements that buildings must satisfy when subjected to the actions of, among other hazards, severe winds. Australian /New Zealand Wind Loadings Standard (AS/NZS 1170.2, 2011) specifies the gust wind speeds used in calculating loads on structures in different of the country. Design wind speeds are similar to wind hazard (both described in terms of return period gust wind speeds), and the levels are set in an effort to equalise the risk between the low and high hazard across the country. Areas around the northern coastline are subject to the impact of tropical cyclones, and as such are deemed to experience the highest wind hazard. This results in Australia being divided into four regions, within which the wind speed is broadly similar. Regions C and D are those where the hazard is dominated by tropical cyclones. A recent report of climate change on design wind speeds in cyclonic regions (Holmes, 2008) prepared for the Australian Building Codes Board recommended that: • wind Region C should be extended south on the Queensland coast to 27 o S. This is justified based on the recent simulation studies on the effects of climate change, and restores the boundary to that in the Standard between 1975 and 1989. • The existing uncertainty factor for Region C, FC, should be increased to 1.10 (+5%), primarily in response to predictions of increased Category 3-5 cyclones by climate model simulations. An area where the impact of such regulatory changes would be significant is the Sunshine Coast region in Queensland. Changing the AS/NZS 1170.2 region from B to C would render most of the existing homes non- compliant, hence increasing the risk by virtue of increased hazard without reduction in vulnerability via adaptation. This study seeks to develop the underpinning science that could be used to evaluate the need for adaptation (re-classification and retrofit of existing housing to comply with revised classification). Cyclonic wind hazard for the Sunshine Coast region has been estimated using Geoscience Australia's Tropical Cyclone Risk Model, utilising synthetic tropical cyclone event sets derived from observations (1981-2006) as well as IPCC AR4 climate models. regional wind hazard levels have been modified for terrain, topographic and shielding effects to reflect localised variations in wind hazard. resulting local wind hazard maps depicting annual exceedence probabilities for severe wind gusts have been integrated with the National Exposure Information System (NEXIS) to provide an analysis of impact, in terms of residential buildings affected and the cost of replacement. Return periods (annual exceedence probabilities) associated with severe wind gust hazard were evaluated for the Sunshine Coast and Southeast Queensland for both current climate and future climate scenarios. This wind gust hazard was subsequently used to evaluate annualised loss, which represents the average annual cost to the region of exposure to wind hazard if viewed through a very wide window of time. costs and benefits of potential changes to wind loading for the Sunshine Coast area have been analysed in a Regulation Impact Statement (RIS) prepared by the Australian Building Codes Board (ABCB, 2010). RIS focuses on changes to standards for new buildings and houses; it does not address the impacts on existing buildings. This study presents analyses of risk for both existing and new buildings considering the variation in structural vulnerability within the building stock.

Wind loads on a building are sensitive to a number of factors, including the wind speed approaching the site, building height and shape, and the local influence of nearby buildings on the wind flow patterns. Building codes attempt to allow for these factors by providing simple formulae for calculating design wind loads that will be at least conservative. The American Society of Civil Engineers (ASCE) 7 Standard [1] and most other building codes recognize that for irregularly shaped buildings or structures that may have unusual response characteristics it is advisable to undertake detailed wind load studies or use wind tunnel methods of analysis. Wind tunnel methods determine the wind loading on a structure with increased precision, which leads to more economical and risk consistent structural designs than do code calculation methods. This paper describes the wind tunnel method of determining cladding wind loads, and provides comparisons between the wind tunnel method and code calculation methods for a 22-story building.

Вопросы аэродинамики зданий всегда считались достаточно важными, а в настоящее время они являются решающими для проектирования многоэтажных высотных зданий и расчета воздушных потоков снаружи здания, оценки влияния здания на аэродинамический режим прилегающей территории, выбора ограждающих конструкций и т.п. Кроме того, внутри зданий могут возникать сильные воздушные потоки, что требует специальных расчетов и решений. Расчет обтекания ветровым потоком зданий нелинейных форм необходим для определения ветровых нагрузок на конструкции здания. Основной интерес представляют сильные кратковременные ветра (скорость потока 20–35 м/с), а также слабые ветра со скоростью потока на уровне 5 м/с. При проектировании, строительстве и эксплуатации высотных зданий и комплексов часто приходится сталкиваться с тем, что действующие строительные нормы и правила не содержат рекомендаций по назначению аэродинамических коэффициентов для оригинальных по форме и крупногабаритных сооружений. Ныне действующая методика определения ветровой нагрузки была разработана в начале 70-х годов в ЦНИИСК им. Кучеренко и реализована в СНиП 2.01.07-85* «Нагрузки и воздействия». При выпуске данного СНиП выражения, описывающие динамическую реакцию сооружений при действии ветра, были приведены к системе коэффициентов, что сильно упростило реальное взаимодействие здания с ветровым потоком. В новой редакции СП 20.13330.2016 методика расчета ветровых нагрузок существенных изменений не претерпела. Несмотря на включение в него ряда схем и положений из Еврокода, принципиальных отличий от «старого» СНиП документ не содержит. Необходимо отметить, что новые строительные нормы Украины переработаны коренным образом, что привело к заметному увеличению расчетных нагрузок. В настоящее время в практике проектирования используются методики, которые позволяют проводить оценку ветровых нагрузок на здания. В данной статье рассмотрены вопросы моделирования и решения задач, связанных с определением ветрового давления на здания нестандартной формы в программных комплексах Autodesk Revit + Autodesk Robot Structural Analysis на примере расчета здания в форме, образованной путем вращения треугольника Рело относительно оси симметрии. Выполнен сравнительный анализ двух способов решения задачи. Показаны изополя давлений и перемещений в элементах. Сделаны выводы о расхождениях в результатах решения задачи двумя способами. The issues of building aerodynamics have always been considered quite important, and today they are crucial for designing multi-storey high-rise buildings and calculating air flows outside the building, assessing the impact of the building on the aerodynamic regime of the surrounding area, choosing enclosing structures, etc. Apart from that, strong air flows can occur inside buildings, which require special calculations and solutions. Calculation of wind flows around buildings of nonlinear forms is necessary for determining wind loads on the building structure. Strong short-term winds (flow rate of 20-35 m / s, as well as weak winds with a flow rate of 5 m/s) are in the focus of our research interest. When designing building and operating high-rise constructions, engineers and architects face the lack of guidelines and recommendations that would assign aerodynamic coefficients to nonstandard and large-sized buildings. The current method for determining wind loads was developed in the early 70s at the Central Research Institute of Building Structures and was documented in the building codes SNiP 2.01.07- 85* "Loads and impacts". When SNiP 2.01.07-85 "Loads and impacts" was released, the expressions describing the dynamic response of structures under the impact of wind were reduced to a system of coefficients, which greatly simplified the actual interaction of the building with the wind flow. In the new version of the Building Codes СП 20.13330.2016, the method for calculating wind loads has not undergone significant changes. Despite the inclusion of a number of schemes and provisions from the Eurocode, the document does not contain any fundamental differences from the earlier edition of the SNiP. It should be noted that the new building codes of Ukraine have been radically revised, which has led to a noticeable increase in design loads. The current design practices allow the assessment of wind loads on buildings. This research deals with modeling and solving problems related to determining wind pressure on buildings of non-standard shape in the Autodesk Revit + Autodesk Robot Structural Analysis software packages using the example of calculating a building in the shape formed by rotating the Reuleaux triangle relative to the axis of symmetry. The authors have carried out the comparative analysis of two approaches to deal with this problem. Isofields of pressures and displacements in elements have been shown. Conclusions are made about the discrepancies in the results of solving the problem in two ways.

The grand building code called Yingzao fashi, drafted in the twelfth-century Song dynasty, was used as a technical reference guide and assisted previous researchers in analyses of premodern Chinese building structures and construction, yet how the building code entangled with contemporary society, coetaneous challenges and the changing courses of political power deserves a comprehensive investigation. This study applies the research approach of textual analysis to track the vicissitude of the grand building code, examine these contemporary reforming attempts related to the building code, and scrutinise the consequence of the national building code when it was implemented in the later Song dynasty. By tracing the formation, promulgation and implementation of Yingzao fashi in premodern China, this paper reveals that the building standards are the product of emerging philosophical theories and the standardisation of practices is the key strategy in the building and construction reforms. It also concludes that the political and power factors would dominantly influence the evolution of the building code and thwart its effectiveness, thus producing a result opposite to its initial intention in practice.

The beam-column joint is a critical structural element in reinforced concrete structures, especially under lateral loading conditions. These joints are prone to failure due to high shear stress concentrations, making their accurate design and assessment essential for structural safety.This study aims to assess the accuracy of existing building code provisions for predicting joint shear strength of interior beam-column joints and to develop an advanced predictive model that addresses the code provisions limitations. By analyzing a database consist of 158 tested specimens, a significant discrepancy was observed between code provisions and experimental joint shear strengths, highlighting the unreliability of existing code provisions. To address this, an artificial neural networks (ANNs) were employed to create a model considering key factors influencing joint behavior. Statistical analysis demonstrated the ANN model’s exceptional accuracy in predicting joint shear strength of interior beam-column joints, achieving a correlation coefficient of 0.98 with experimental data. This performance significantly outperformed the 0.66–0.73 range observed for code-based predictions. The model's parameters are presented in a user-friendly format for easy implementation using spreadsheet software, making it a valuable tool for enhancing shear strength predictions in future building codes.

Although the main structural systems of fully engineered buildings perform adequately during extreme wind events, costly losses happen to buildings once the components of the exterior walls and claddings fail. In response to these failures, new design methods have been developed that result in higher design wind loads applied to components, and prescribe additional tests on cladding to determine the structural resistance of exterior wall elements. This paper discusses some recent changes to the wind load design provisions of the American Society of Civil Engineers (ASCE) Standard, ASCE 7-98, that apply to exterior building walls. ASCE 7-98 includes new concepts for cladding design that consider impact resistance and topographic effects on overall wind loads. Examples compare the wind design loads obtained using ASCE 7-98 with loads obtained with 7–95 and 7–88 for regular-shaped buildings. The changes may eventually influence the exterior wall design throughout the U.S. because the recently published International Building Code (IBC-2000), formed under a partnership agreement of the three existing model building codes, has adopted ASCE 7-98. Improving the wind performance of exterior walls depends equally on improved wind design codes as well as on improved test procedures that determine the structural capacity of installed cladding systems. The current state-of-the-art in full-scale testing of building components is discussed, and a summary of current full-scale tests is presented. The author proposes that the current fragmented design process for different cladding materials and the reliance on materials-specific performance tests is too complex and needs to be streamlined in order to improve the overall performance of building envelope systems.

High wind events such as hurricanes are one of the leading causes of electricity transmission line failures. There are two main failure mechanisms associated with de-energized transmission systems during hurricanes: 1) failure of the super-structures or the support towers; and 2) breakage of the transmission lines due to extreme wind loads. This paper presents a methodology for analyzing the reliability of spatially distributed transmission lines under hurricane wind hazard. As a case study, the vulnerability of the spatially distributed 230kv transmission lines in south Carolina was analyzed using 40,000 years of simulated hurricane events. Since the response of transmission lines under wind loads is highly nonlinear, a simplified nonlinear analytical model, verified by a 3-dimentional finite element model, was developed to simulate the tension forces considering the geometric nonlinearity induced by the sagging of the transmission lines. The reliability analysis results are presented in a GIS map, which can be easily used in pre-hurricane planning by power

In order to solve the problem of transmission line galloping breakage under ice storm, a probability prediction model of transmission line breaking based on improved particle swarm optimization is proposed. Firstly, the generalized extreme value (GEV) distribution parameters of wind load and ice load of transmission lines under ice storm disasters are determined by improved particle swarm optimization (PSO) algorithm, then the excess distribution of the ice load and wind load of the transmission line is obtained according to the critical wind speed and critical icing density as the transmission line begins to gallop. And then, based on the binary t-Copula function, the joint probability distribution of ice load and wind load is obtained, and breaking probability of transmission line galloping under ice storm disaster is realized. Finally, using actual historical data of transmission line breaking in winter in Hunan Province, the superiority of the improved PSO algorithm and the accuracy of the proposed prediction model are verified, which can lay a foundation for transmission line galloping breakage prediction and provide a basis for pre-deployment of anti-galloping measures.