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As an optimization that starts from a randomly selected structure generally does not guarantee reasonable optimality, the use of a systemic approach, named the ground structure, is widely accepted in steel-made truss and frame structural design. However, in the case of reinforced concrete (RC) structural optimization, because of the orthogonal orientation of structural members, randomly chosen or architect-sketched framing is used. Such a one-time fixed layout trend, in addition to its lack of a systemic approach, does not necessarily guarantee optimality. In this study, an approach for generating a candidate ground structure to be used for cost or weight minimization of 3D RC building structures with included slabs is developed. A multiobjective function at the floor optimization stage and a single objective function at the frame optimization stage are considered. A particle swarm optimization (PSO) method is employed for selecting the optimal ground structure. This method enables generating a simple, yet potential, real-world representation of topologically preoptimized ground structure while both structural and main architectural requirements are considered. This is supported by a case study for different floor domain sizes.
One of the main criteria determining the thermal comfort of occupants is the air temperature. To monitor this parameter, a thermostat is traditionally mounted in the indoor environment for instance in office rooms in the workplaces, or directly on the radiator or in another location in a room. One of the drawbacks of this conventional method is the measurement at a certain location instead of the temperature distribution in the entire room including the occupant zone. As a result, the climatic conditions measured at the thermostat point may differ from those at the user's location. This not only negatively impacts the thermal comfort assessment but also leads to a waste of energy due to unnecessary heating and cooling. Moreover, for measuring the distribution of the air temperature under laboratory conditions, multiple thermal sensors should be installed in the area under investigation. This requires high effort in both installation and expense.
To overcome the shortcomings of traditional sensors, Acoustic travel-time TOMography (ATOM) offers an alternative based on measuring the transmission sound velocity signals. The basis of the ATOM technique is the first-order dependency of the sound velocity on the medium's temperature. The average sound velocity, along the propagation paths, can be determined by travel-times estimation of a defined acoustic signal between transducers. After the travel-times collection, the room is divided into several volumetric grid cells, i.e. voxels, whose sizes are defined depending on the dimension of the room and the number of sound paths. Accordingly, the spatial air temperature in each voxel can be determined using a suitable tomographic algorithm. Recent studies indicate that despite the great potential of this technique to detect room climate, few experiments have been conducted.
This thesis aims to develop the ATOM technique for indoor climatic applications while coupling the analysis methods of tomography and room acoustics. The method developed in this thesis uses high-energy early reflections in addition to the direct paths between transducers for travel time estimation. In this way, reflections can provide multiple sound paths that allow the room coverage to be maintained even when a few or even only one transmitter and receiver are used.
In the development of the ATOM measurement system, several approaches have been employed, including the development of numerical methods and simulations and conducting experimental measurements, each of which has contributed to the improvement of the system's accuracy. In order to effectively separate the early reflections and ensure adequate coverage of the room with sound paths, a numerical method was developed based on the optimization of the coordinates of the sound transducers in the test room. The validation of the optimal positioning method shows that the reconstructed temperatures were significantly improved by placing the transducers at the optimal coordinates derived from the developed numerical method. The other numerical method developed is related to the selection of the travel times of the early reflections. Accordingly, the detection of the travel times has been improved by adjusting the lengths of the multiple analysis time-windows according to the individual travel times in the reflectogram of the room impulse response. This can reduce the probability of trapping faulty travel times in the analysis time-windows.
The simulation model used in this thesis is based on the image source model (ISM) method for simulating the theoretical travel times of early reflection sound paths. The simulation model was developed to simulate the theoretical travel times up to third-order reflections.
The empirical measurements were carried out in the climate lab of the Chair of Building Physics under different boundary conditions, i.e., combinations of different room air temperatures under both steady-state and transient conditions, and different measurement setups. With the measurements under controllable conditions in the climate lab, the validity of the developed numerical methods was confirmed.
In this thesis, the performance of the ATOM measurement system was evaluated using two measurement setups. The setup for the initial investigations consists of an omnidirectional receiver and a near omnidirectional sound source, keeping the number of transducers as few as possible. This has led to accurately identify the sources of error that could occur in each part of the measuring system. The second measurement setup consists of two directional sound sources and one omnidirectional receiver. This arrangement of transducers allowed a higher number of well-detected travel times for tomography reconstruction, a better travel time estimation due to the directivity of the sound source, and better space utilization. Furthermore, this new measurement setup was tested to determine an optimal selection of the excitation signal. The results showed that for the utilized setup, a linear chirp signal with a frequency range of 200 - 4000 Hz and a signal duration of t = 1 s represents an optimal selection with respect to the reliability of the measured travel times and higher signal-to-noise ratio (SNR).
To evaluate the performance of the measuring setups, the ATOM temperatures were always compared with the temperatures of high-resolution NTC thermistors with an accuracy of ±0.2 K. The entire measurement program, including acoustic measurements, simulation, signal processing, and visualization of measurement results are performed in MATLAB software.
In addition, to reduce the uncertainty of the positioning of the transducers, the acoustic centre of the loudspeaker was determined experimentally for three types of excitation signals, namely MLS (maximum length sequence) signals with different lengths and duration, linear and logarithmic chirp signals with different defined frequency ranges. For this purpose, the climate lab was converted into a fully anechoic chamber by attaching absorption panels to the entire surfaces of the room. The measurement results indicated that the measurement of the acoustic centre of the sound source significantly reduces the displacement error of the transducer position.
Moreover, to measure the air temperature in an occupied room, an algorithm was developed that can convert distorted signals into pure reference signals using an adaptive filter. The measurement results confirm the validity of the approach for a temperature interval of 4 K inside the climate lab.
Accordingly, the accuracy of the reconstructed temperatures indicated that ATOM is very suitable for measuring the air temperature distribution in rooms.
The release of the large language model-based chatbot ChatGPT 3.5 in November 2022 has brought considerable attention to the subject of artificial intelligence, not only to the public. From the perspective of higher education, ChatGPT challenges various learning and assessment formats as it significantly reduces the effectiveness of their learning and assessment functionalities. In particular, ChatGPT might be applied to formats that require learners to generate text, such as bachelor theses or student research papers. Accordingly, the research question arises to what extent writing of bachelor theses is still a valid learning and assessment format. Correspondingly, in this exploratory study, the first author was asked to write his bachelor’s thesis exploiting ChatGPT. For tracing the impact of ChatGPT methodically, an autoethnographic approach was used. First, all considerations on the potential use of ChatGPT were documented in logs, and second, all ChatGPT chats were logged. Both logs and chat histories were analyzed and are presented along with the recommendations for students regarding the use of ChatGPT suggested by a common framework. In conclusion, ChatGPT is beneficial for thesis writing during various activities, such as brainstorming, structuring, and text revision. However, there are limitations that arise, e.g., in referencing. Thus, ChatGPT requires continuous validation of the outcomes generated and thus fosters learning. Currently, ChatGPT is valued as a beneficial tool in thesis writing. However, writing a conclusive thesis still requires the learner’s meaningful engagement. Accordingly, writing a thesis is still a valid learning and assessment format. With further releases of ChatGPT, an increase in capabilities is to be expected, and the research question needs to be reevaluated from time to time.
Die Planungsforschung hat sich spätestens seit der „kommunikativen Wende“ intensiv damit beschäftigt, wie mit Konflikten umgegangen werden soll und wird. Ansätze der „agonistischen“ Planungstheorie widersprechen der normativen Prämisse, Konsensbildung unter den Planungsbeteiligten anzustreben. Vielmehr wollen sie widerstreitende Positionen normativ für die räumliche Entwicklung fruchtbar machen. Zugleich betonen sie eine vermeintliche Dualität von Planung und Protest, die in der neueren Protesttheorie infrage gestellt wird. Dieser Beitrag zeigt aufbauend auf einer Diskussion von planungs- und protesttheoretischen Ansätzen und einer empirischen Analyse planungsbezogener Proteste in Deutschland, dass diese Proteste von den Planungsakteuren zwar immer stärker als „Normalität“ aufgefasst werden und antagonistische Partizipation trotz zunehmender Konflikthaftigkeit und vermeintlicher Infragestellung der repräsentativen Demokratie kulturell regelgebunden bleibt. Protesthandeln ist Teil ausdifferenzierter „Partizipationsbündel“, die situationsbezogen auch Teilnahme an Beteiligungsverfahren, direktdemokratische Verfahren und Klagen umfassen. Protestierende verfolgen dabei meist eine eher reformorientierte Agenda, die keiner „Zähmung“ bedarf. Allerdings können die zugrunde liegenden Konflikte häufig gar nicht „gelöst“ werden. Planenden hingegen können auch innerhalb eines agonistischen Planungsumfelds rationalistische und deliberative Ansätze zur Verfügung stehen, die sie situationsbezogen und strategisch nutzen.
Experimental Validation of Dynamic Response of Small-Scale Metaconcrete Beams at Resonance Vibration
(2023)
Structures and their components experience substantially large vibration amplitudes at resonance, which can cause their failure. The scope of this study is the utilization of silicone-coated steel balls in concrete as damping aggregates to suppress the resonance vibration. The heavy steel cores oscillate with a frequency close to the resonance frequency of the structure. Due to the phase difference between the vibrations of the cores and the structure, the cores counteract the vibration of the structure. The core-coating inclusions are randomly distributed in concrete similar to standard aggregates. This mixture is referred to as metaconcrete. The main goal of this work is to validate the ability of the inclusions to suppress mechanical vibration through laboratory experiments. For this purpose, two small-scale metaconcrete beams were cast and tested. In a free vibration test, the metaconcrete beams exhibited a larger damping ratio compared to a similar beam cast from conventional concrete. The vibration amplitudes of the metaconcrete beams at resonance were measured with a frequency sweep test. In comparison with the conventional concrete beam, both metaconcrete beams demonstrated smaller vibration amplitudes. Both experiments verified an improvement in the dynamic response of the metaconcrete beams at resonance vibration.