Advanced and Robust Analysis of Wind Effects
Advanced and Robust Analysis of Wind Effects
How global warming is impacting existing infrastructures and what we can do about it?
Global warming can be defined as the rise of the average global temperature. Over the last three decades we have witnessed a constant increase in the global temperature of land and ocean which has caused changes in atmospheric moisture and rainfall. This condition is causing extreme weather events, more storm, more intense rainfall, and sea level rise. These environmental changes also have a great impact on our infrastructures. Decreased and increased precipitation, higher temperature and higher sea levels are all affecting buildings, transportation systems, and vital infrastructures for water and energy supply in different ways, accelerating their deterioration and threatening our safety.
All structures have a certain design life for which they were conceived, designed, and then built. Until a few years ago the fact that their life had a limit was not very clear. Because of that many structures all over the world have been suffering from deterioration due to inadequate maintenance, which has been worsened by global warming. Extreme weather events are, in fact, shortening our infrastructure design life even more, leading to potential great disruption and damage to our economy and to citizens’ life.
Transportation systems ensure efficient distribution of energy, food and trade, and they are essential for workers and consumers to access jobs and markets, while energy production and distribution facilities are essential for electricity provision of a region. The damage to these infrastructures due to climate change can create significant problems for our cities.
Transportation systems that provide energy distribution and commerce, similar to an icecasino that provides players with access to a variety of games and entertainment. Just as efficient energy distribution is important for regional development, online casino bonuses and promotions can stimulate player interest and provide additional benefits. A variety of casino games such as poker, slots and roulette, similar to power generation and distribution facilities, can meet the different needs of players and contribute to the growth of this industry segment.
The following are a few of the effects that climate change can have on some transportation systems.
| Climate Change | Roads | Railways | Bridges |
|---|---|---|---|
| Temperature change | Rapid asphalt deterioration and substructure damage | Expansion and buckling of railway tracks joints | Accelerated material degradation |
| Precipitation change | Accelerated erosion and construction damage, and increased flooding | Accelerated erosion and construction damage, and increased flooding | Higher bridge scour and accelerated erosion and construction damage |
In order to know how infrastructures are reacting to climate change, they must be monitored regularly. Structural Health Monitoring (SHM) is the process of determining the condition of a structure to identify variations in its response to stress or to other factor and to plan the type of maintenance needed, which helps improve their service life.
However, Structural Health Monitoring not always implemented. The truth is that traditional SHM also comes with some issues that have limited its use in real engineering practice, such as the high cost of the systems, the complex installations (due to wired sensors) and the difficult data interpretation. Smart SHM is offering a solution to all those problems: let’s see how.
Smart SHM as a strategy to help reduce the impact of global warming on infrastructures
Now more than ever we need an easy and accessible way to monitor the health of our infrastructures in order to assess their deterioration, to understand how they are affected by drastic environmental changes and to plan effective maintenance before it is too late. Thanks to the recent advancements in technology and to the Internet of Things (IoT), all that is possible! We now have access to smart devices that are disrupting the industry, allowing infrastructure owners to remotely monitor the deterioration and the overall health of structures in a quick, cost-effective and easy way.
Smart SHM allows infrastructure owners to overcome the problems related to traditional monitoring. That enables them to implement a more efficient and continuous monitoring strategy that can promptly identify the effect of climate change on infrastructures in order to plan more effective maintenance.
The following are the main advantages that come with Smart Structural Health Monitoring, compared to traditional monitoring:
Figure 1. Example of a Cloud Platform for remote and real-time monitoring of a bridge
Figure 2. Example of a Smart SHM system
Case study
The Vespucci bridge is one of the central bridges of Florence that crosses the Arno River, joining San Frediano district with the rest of the city. It has three spans, with an overall length of 162m. Designed by Riccardo Morandi and built between 1954-1957, it has been suffering from deterioration of the concrete, accelerated by climate change. The deterioration has particularly affected the two piers, due to the erosion of the riverbed caused by water and it requires continuous and real-time monitoring.
Figure 3. Vespucci bridge
In order to meet those requirements, a smart monitoring system has been set up on place, using the following sensors:
Figure 4. Monitoring system of the Vespucci bridge
Thanks to a monitoring system that leverages the latest IoT technologies, the city of Florence can continuously analyse how climate change and other factors are affecting the deterioration of the bridge, so as to plan promptly maintenance.
Figure 5. Dynamic displacement sensor on the bridge
In a Nutshell
To summarize, Structural Health Monitoring is an important tool that helps:
Thanks to recent advancements in technology and to the development of Internet of Things (IoT) devices, all SHM systems can now be:
Adopting Smart Structural Health Monitoring systems can deliver a strong return both by reducing costs from climate-related damage to infrastructures and by avoiding significant knock-on effects in wider society.
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Recognized as the home of luxury living in the heart of Mumbai, Lokhandwala Minerva, with an impressive 91-storeys, standing at approximately 1,000 ft. tall. According to CTBUH, it will become India’s tallest skyscraper upon completion. Overlooking the Arabian Sea and lush Mahalaxmi Racecourse, Lokhandwala Minerva will soon be home to some of India’s elite, including icons of India’s business, film, and fashion industries.
Minerva is being developed by Lokhandwala Infrastructure, a renowned name in Mumbai’s real estate & internationally in Dubai and is meticulously designed and crafted by partnering with the world’s finest minds such as; Hafeez Contractor, the award-winning architect (Padma Bhushan), leading structural consultant J+W Consultants, and construction partner Larsen & Toubro. Windtech Consultants have provided the essential perfomance-based wind engineering studies to make this significant project buildable while allowing it to be optimised to operate within the relevant structural performance criteria. Emphasis has been placed on structural efficiency, construction technologies, and environmental sustainability. Advanced form-work technology, high-tech equipment, and fully mechanized systems have been utilised to ensure high-quality construction standards are being met, as well as enable the timely completion of the project.
Mr. M. A. Lokhandwala, the Chairman of Lokhandwala Infrastructure states that, “Instead of building several structures around the city, our goal was to construct one super tall skyscraper that dominates the skyline. That is how we got the idea of making Minerva, the Tallest Tower and the landmark for the country.”
Mustafa Lokhandwala, Principle Architect and Business Head at Lokhandwala Infrastructure commented that “The name Minerva is inspired by the Greek Goddess representing Art, which is a reflection of Minerva’s ultimate artistic design, engineering and construction quality. Minerva was also my late father Mr. Moeiz Lokhandwala’s (Managing Director of Lokhanadwala Infrastructure) dream project. For him, Minerva was also inspired to be a source of pride for the country. Since, Minerva is a Slum Rehabilitation Project we even had the opportunity to develop the surrounding land parcel and give people a better standard of living by constructing a government school, dispensary and residential towers for the poor. We strived to create a holistic environment and aim for a higher standard of living. Work conducted by WIndtech on wind pressure on the building model has been tested to withstand the extreme wind and climatic conditions for the foreseeable future based on the IMD data for the last 70 years.” –
Advanced form-work technology, high-tech equipment and fully mechanized systems have been utilised to ensure high-quality construction standards are being met, as well as enable the timely completion of the project. According to Mr Pai, the L&T cluster head and regional director, “It is a matter of pride for us at L&T to be part of construction for one of India’s tallest buildings. It was a massive challenge to build around a 1000ft tall structure near Mumbai’s coastal region. With the advanced technique and quality used to develop this landmark project, we have made the impossible possible.”
Karl Wadia, the Lead Designer from Hafeez Contractor comments “Minerva is a unique & inspiring piece of Architecture arranged on an impossibly narrow and linear site that overlooks the majestic Mumbai Race Course and Arabian Sea beyond. The design demanded the consumption of a very high Gross Floor Area in order to make the project commercially viable. Given the spectacular views to the West and the pressure of area consumption it became evident very early in the design evolution that a super high rise would be the eventual outcome. We designed two joined Towers having a total width in excess of 100m & a height in excess of 300m considering nearly all apartments would eventually look view side west.
The narrowness of the site resulting in a high aspect ratio & the wind forces that came into play required us to architecturally intervene & thus we wrapped the West Facing Wind side facade with end to end curved balconies for each and every apartment. This helped reduce the wind forces on the towers overall while creating precious semi-open balconies to each apartment owner.
The uniqueness of the Architectural Design also extends to the complexity where in the project had to undergo a major re-design 50% into construction catering to a new set of changing Local Bye Laws which came into effect during the life cycle of the project. This is evident @ the 2/3rd height of the Towers where the building is divided into two arms. The design language of balconies continues all the way to the top.”
Figure 1. Artistic Render of Lokhandwala Minerva (Image courtesy of Dawn Digital)
Windtech played a major role in the wind engineering for this project, which significantly assisted in the design and cost optimisation of the building. A Structural Loads and Building Motion Wind Tunnel Study was conducted using Windtech’s advanced sub-structure analysis technique (first published by Rofail and Holmes in 2007). This enables an accurate assessment of the effect of the load transfer between the two wings of the tower as the tower oscillates under the extreme wind actions.
Windtech’s regional director for Asia, Aaron Lefcovitch, comments that: “Minerva was an interesting project in that it included two separate sub-structures, that while connected, responded dynamically independent. For a typical tower we would normally provide the structural engineer floor-by-floor loads about a single axis, however the same approach could not be applied to this tower because the sub-structures do not vibrate in a unified way. As such, we used a method called multi-substructure analysis, which allows us to generate a set of floor-by-floor loads for each sub-structure, taking into consideration their influence on one another via the rigid links that connect them. We have worked on many structures that are configured in this way using advanced techniques published by Tony Rofail, a Director at our Sydney Office and Dr John Holmes of JDH. The techniques we currently employ for multi-substructure analysis represent currently the world’s best practice for analysing rigidly connected substructures”.
In addition, Wind loads on the roof crown were also tested via a wind tunnel study, due to the fact that simply utilising the cladding pressure for the design of the primary structural elements supporting the roof crown would be far too conservative since peak pressures do not occur at the same time over long spans. Hence the area averaging method was employed to provide accurate loads cases in the form of equivalent static loads for 12 critical wind direction sectors.
Figure 2. Photograph of our 3D-printed Wind Tunnel Model of Lokhandwala Minerva in our testing facility (View from the west)
We would like to congratulate Lokhandwala Infrastructure, Hafeez Contractor and the rest of the team responsible for the progress of this iconic tower which will become a dominant landmark in the Mumbai Skyline for many years to come.
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As a symbol of faith and reverence in the tutelary deity Maa Umiya, Vishv Umiya Foundation has taken on the challenging task of building the tallest temple in Asia, and one of the tallest temples in the world at 144m. UmiyaDham is rooted in the ancient Vedic traditions. It has been touted as being a distinctive place where the devotee will be able to gather and experience the tranquil divinity.
Figure 1. Image of Vishv Umiadham Temple (Image courtesy of the Vishv Umiya Foundation)
The temple is planned for city of Ahmedabad (near Vaishno Devi circle) on land admeasuring 60 acres, and is budgeted to cost over Rs. 10 billion to build. Along with the temple it will be house a socio-economic empowerment hub for our community’s well-being.
Given the complexity of the building form and the apparent structural design constraints, the consultancy team, made up of Colliers as Project Manager and Kling Consult as the Structural Consultant, were acutely aware that the structure and cladding systems could not be designed using basic code-based principles, and that a performance-based wind design approach was needed.
Aaron Lefcovitch who covers Windtech’s projects in Asia comments that “Codes only address the typical case and applying code-based principles for a building as complicated as the Vishv Umiadham Temple Project could potentially be misleading, assuming the designer does not properly compensate for the fact that there is a significant departure from the regular form. It is not unusual for us to conduct a code-based desktop analysis and structural data reviews. We do this on most of our projects as part of a QA process and first glance at expected, albeit usually slightly conservative loads and accelerations. This helps us align with the structural engineer early on in our program, however, care must be taken in the application of code-based wind desing. In general, the code can be used when the height to minimum with ratio is less than 5:1, when the natural frequency is higher than 0.2Hz, and when the building height does not exceed 150m (i.e. as per the Indian Standard IS875). In some circumstances, we may refer to coefficient data obtained from past testing of similar structures, however in general the above principles still apply.
As part of the commission for this project, Windtech was appointed to carry out the following wind tunnel studies which assisted in the efficient design of the structural and cladding systems as well as the ensuring adequate wind conditions in all the critical outdoor areas:
Figure 2. Layout of Pressure Sensors
Figure 3a. Elevation Drawing with Pressure Contours
Figure 3b. Roof Plan Drawing with Pressure Contours
We would like to congratulate the team made up of Vishv Umiya Foundation, Colliers, Kling Consult, and many others for pulling off this unique and innovative award-winning project. It is truly an iconic temple and will be for the next 500 years.
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Architects and engineers continue to push the traditional boundaries of their disciplines, and by using ultra-modern materials and state-of-the-art structural design techniques, they’re often able to create buildings and structures that are cutting edge works of art.
Key to the design of buildings and structures is the ability to have on hand accurate wind loading. However, the wind loads produced by building codes are conservative at best or can produce wind loads that depart away from reality. Most codes and standards base their predictions assuming a building with a regular rectangular form with typical height, aspect ratio, and stiffness. Many writers of codes recognise the limits of their application hence often place clauses that recommend the use of wind tunnel testing when these limits have been exceeded. For buildings that are designed to be within the limits of the code, wind tunnel testing can still be used and is being used by many project teams as a way to reduce the costs of construction due to the elimination of overdesign while ensuring that structure and cladding systems have been designed to be robust during extreme wind events over their design life.
Wind tunnels have been used as a tool to investigate different flow phenomena which could not be predicted using empirical or computational tools. Quality Assurance manuals drafted by the American Society of Civil Engineers (ASCE) and Australasian Wind Engineering Society (AWES) specifically mention that Computational Fluid Dynamics (CFD) cannot be used for the determination of wind effects on structure and cladding as there are limitations when determining the complex gust wind speeds which is one of the primary drivers for the assessment of peak wind loads. This is also supported by Cochran and Derickson 2011. When it comes to buildings, wind tunnel testing can have the following advantages:
Wind tunnel tests consider various project-specific factors that influence the results and can be modelled in detail.
Wind tunnel testing has been proven to be the most accurate tool for simulating wind effects on and around buildings and other structures. This has been backed up by numerous benchmark studies comparing results from full scale/model scale studies. For the determination of load on structure and cladding, it remains to be the only reliable tool that can be used in the bid to ensure a robust building from a serviceability and strength design point of view.
The proposed Integrated Waste Management Facilities (IWMF) Phase 1 developed by the Environmental Protection Department of Hong Kong Government is the first such facility in Hong Kong that will adopt the state-of-the-art technologies to substantially reduce the bulk size of mixed municipal solid waste, to generate energy and to recover useful resources. The IWMF Phase 1 will comprise an advanced thermal incineration plant with a tall chimney tower and a mechanical sorting and recycling plant located at an artificial island to the south of Shek Kwu Chau in Hong Kong. An artist’s impression of the IWMF Phase 1 is shown in Figure 1.
Figure 1. An Artist Impression of the Proposed IWMF Phase 1 Development (image from https://iwmfhk.com/en/)
The proposed chimney tower has a complex aerofoil prismatic cross-section and will be equipped with a complex cladding system to achieve the visual appearance of a sail-like profile. The wind performance of this unusual and asymmetrical chimney tower cannot be predicted by the analytical approach provided in the “Code of Practice on Wind Effects in Hong Kong 2004” or other international wind codes. Especially the potential vortex shedding and localised wind effects on the cladding elements can only be assessed reliably through a wind tunnel study. Furthermore, as illustrated in Figure 1, there is significant topography near the project site and a topographical model wind tunnel study was undertaken to assess the impact of this topography on the wind climate at the site.
As emphasises in the recently released Prestandard for Performance-Based Wind Design (2019) by the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE), “wind tunnel testing is the only approach consistent with reliable application of performance-based design principles and shall be used to determine the local wind pressures and global wind-induced structural loads and responses”. Similarly, in the ASCE Manual of Practice No. 143 it states: “Wind tunnel testing . . . is the only current method that allows the designer to determine aerodynamic characteristics for specific shapes and over a full range of wind speeds”. Hence, with the view of designing an optimised, economical and safe chimney tower, Windtech has been appointed by Arcadis (the design consultant) on behalf of Zhen Hua / Keppel Seghers Joint Venture (the main contractor) to carry out a purposely designed boundary layer wind tunnel study to accurately determine the wind loads for the structural and façade cladding.
The wind tunnel study was carried out in two stages to allow the design team to improve the efficiency of the structural and façade cladding systems by using the results from the first stage wind tunnel test to modify and optimise the external geometry, the structural arrangement, and the design of the façade cladding elements. The wind performance of the optimised design was then verified through the second stage wind tunnel test.
A pressure model wind tunnel test was adopted to determine both the structural wind loads through High-Frequency Pressure Integration (HFPI) technique and the façade cladding pressures. HFPI technique is the preferred technique in the Prestandard for Performance-Based Wind Design for the determination of structural wind loads and responses as it obtains a more accurate distribution of the mean and background responses.
It was expected the chimney tower will experience significant aerodynamic damping effects due to its height and shape, and an aero-elastic model wind tunnel study was also carried out to determine the amount of aerodynamic damping for the structure. The wind tunnel results illustrated that the chimney tower exhibits positive aerodynamic damping for the critical wind directions for the peak response along the X and Y axes, which helps to reduce the peak structural wind loads and allow the design team to further improve the efficiency of the structural system.
We would like to congratulate the team made up of Arcadis, China Harbour Engineering Company, Zhen Hua / Keppel Seghers Joint Venture, Aecom, Environmental Protection Department, and many others for delivering a great design for this unique and innovative project, which could not have been achieved without the esteemed team.
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