As buildings get taller and lighter, structural engineers are increasingly faced with the consequences of the dynamic response of high-rise buildings to wind. Damping is an important property for the dynamic response of high-rise structures, but is a combination of many mechanisms, which makes it a complex phenomenon to account for in the structural design. Empirical damping predictors currently exist, but a large scatter is found among predictors, as well as between predictors and identified damping from measurements. Damping values are prescribed in codes, but are not consistently conservative. Therefore, there is a strong desire from both structural engineers and researchers to obtain further understanding of damping behaviour in high-rise structures.

Damping identification techniques, such as the Half-power Bandwidth method and the Random Decrement technique are commonly used. However, these are not applicable to buildings with closely spaced modes, and require extensive measurements. Besides, they only provide a damping value, and cannot find damping of separate components of a system. A novel technique, the Energy Flux Analysis, approaches damping from an energy point of view, making it more widely applicable, and allowing for damping identification in components of a structure. The Energy Flux Analysis has been verified to lab structures, but its performance when applied to a high-rise structures using in situ measurements is still unknown.

The aim of this research is to investigate the sensitivities of and prerequisites for the application of the Energy Flux Analysis to high-rise buildings excited by wind using spatially limited measurements. The sensitivities were sought for in the uncertainty of required input for the Energy Flux Analysis: structure motion, which includes internal forces, wind load, data acquisition, and structural properties. The research was performed through application of the Energy Flux Analysis to the New Orleans tower in Rotterdam.

While the sensitivity to structural properties and the magnitude of measurements is limited, the Energy Flux Analysis demonstrated to be highly sensitive to the phase of structural motion, internal forces, and wind load. The first two points are relevant for computing the energy flux at the boundary of a system, when one is interested in damping in the superstructure and due to soil-structure interaction separately. The last point is relevant when one is interested in the total or superstructure damping.

The phase differences occurring between structure motion and internal forces are a direct result of damping. Material damping resulted in a phase difference between stress and strain in the numerical model, while a local damper resulted in a phase difference between structure motion at different locations. The many damping mechanisms occurring in a high-rise structure may each affect the phase of structure motion and internal forces differently. When these phase differences are not taken into account in the Energy Flux Analysis, for instance due to extrapolation of measurements, an erroneous result will be obtained. A brief investigation was performed as to whether these effects can be expected in true structures, but additional research is required.

The fluctuating wind load at the natural frequency of the structure is dominant for the flux of energy from wind to the structure, which is obtained by multiplication of the wind load with the structure velocity. Again, the phase of this wind load is highly important. When measured at one location, little is known about the phase of the wind load at other heights. Different approaches of extrapolating the measured wind load demonstrated a large scatter in the Energy Flux Analysis results. In this research, the Energy Flux Analysis found not to be repeatable, which was proven to be a direct result of the phase difference between the measured wind load and structure velocity. Possible causes for this varying phase difference were formulated.

It is essential, but due to the major advantages of the Energy Flux Analysis also profitable, to perform further research into its application to high-rise structures. Therefore, this study provides extensive recommendations mostly focused on simple numerical and lab experiments. ... Read more

All around the world floods are a growing problem. Dealing with high water levels in residential areas is of great importance. The delta area of Macabebe, in the Manila Bay, has to cope with daily flooding, caused by the river and the sea. Groundwater is pumped and used for local industry, causing land subsidence and worsening the problems. Where once rice fields were the main source of income, these fields are now fishponds where fish escape during a large flood. Additionally, typhoons strike the region regularly. Due to climate change and the ongoing ground subsidence the problems won’t lessen, so a solution needs to be found. In the Netherlands, multiple organizations are working daily on finding solutions. One of these is Finch Floating Homes, who designed a typhoon resilient, floating home for in the Philippines. This design had to be elaborated on before construction of a pilot project. This report contains the needed changes and advice for the design of the floating home. Through research, local interviews and analysis, the design of the house has been improved on the roof, sanitary system and mooring system and a construction plan has been created for the pilot project.

Based on a revision of the roof shape, the hip roof turned out to be the best shape in a typhoon prone area. During the design, the geometry of the housing unit was slightly changed into a double symmetrical geometry, increasing constructability and simplicity of the house. The design of the roof structure and its connections, consisting of four identical prefabricated frames, is presented. After prefabrication, the frames will be connected on-site, after which the newly designed foldable balconies will be placed in the frames. The material used in the design is corrugated steel roof sheeting.
The final roof shape is used to calculate the rainwater collection. The floating house requires a self-sustaining system that fulfils the needs of drinking water and wastewater treatment. This
system consists of three separate systems: (1) rainwater harvesting, consisting of a drainage system, first flush barrel system and sand filter. (2) Storage of water, capable of storing sufficient water for one-third of the total usage over 80% of the year. (3) Wastewater, based on natural treatment before discharge into the surface water, containing a septic tank and wetland filter.
The water management system within the foundation, the wind load on the house, waves and currents influence the motions of the floating structure and the forces on the mooring system. An analysis of the options for mooring systems leads to the decision of using mooring piles. The total stiffness of the piles influences the horizontal motion and rotation of the platform. The vertical motion is a free behaviour; it is not influenced by the mooring piles. It is needed to choose a specific combination of pile length and bending stiffness, after which the strength of the pile is checked.
The design is used for the project construction plan, focussing on the time, risk and change management of the pilot project. The resources and construction activities and their duration were identified to develop a schedule for controlling the construction phase. Preparations and construction of the pilot will take 13 weeks, but includes several risks. Response strategies for these risks are proposed, to use for a risk mitigation plan. Finally, advice is given on how to manage possible design changes regarding new research, development of design and up-scaling changes after a successful pilot project.

With the use of this report and more detailed research and design, the pilot project will be an optimal test of the floating house in the Philippines.
... Read more