The building and construction sector play a key role in achieving a sustainable development. In European countries, buildings are responsible for 40-45% of energy consumption, leading to significant amounts of CO2 emissions. The implementation of reusable structures lead to less waste and harmful emissions to the environment. The main purpose of this thesis is to analyse and evaluate the use of a new type of demountable shear connectors, resin injected bolts, in steel-concrete composite structures through push-out tests. Steel-concrete composite structures are commonly used in flooring systems of offices, car parks and bridge decks throughout the world. The most widely used shear connectors are welded headed studs. Even though they are inexpensive and extended research has been conducted about their application, welded headed studs do not allow for the demountability and reusability of the structural components. An innovative type of shear connector consists of a coupler and a bolt which are embedded in the prefabricated concrete deck. The assembly of the concrete deck with the flange of the steel section which has oversized holes is achieved through resin injected bolts. Resin injected bolts are bolts in which the cavity formed by the clearance between the bolt and the hole is filled up with resin. Large hole clearances allow for fabrication tolerances and lead to a faster execution. Push-out tests were conducted in the laboratory in order to examine resin injected bolts in terms of shear capacity, stiffness and ductility. Two different test configurations were created, one with resin injected bolts and the other one with reinforced resin injected bolts. For each configuration three specimens were tested which were nominally identical, one was loaded until failure using displacement control and the other two were loaded initially in force-controlled load cycles and then until failure. The results obtained from the experiments are compared with the results from researches conducted on other types of demountable shear connectors. FEA models were developed with the same geometry, materials and loading as in experiments using the ABAQUS software and push-out test were performed in order to check the validity of the experimental work. In addition, a parametric study was conducted using FEA in order to evaluate the influence of certain parameters on shear resistance and stiffness. The parameters considered are: the concrete strength class, the bolt diameter, the bolt strength class, the embedded bolt height, the hole diameter of the steel section, the effect of the L-angle profile and the injection material. ... Read more

A study on the fire safety concepts used in car parks. To asses the possible damage as a result of a fire, case studies were performed and changes in the car industry were analysed. The new type of fuel systems have resulted in new risks, which are not yet covered in the current design methodology. To understand the probability of a car park fire an analysis was done on occurred fires in car parks. The changes in the car industry had resulted in larger fires and bigger fires will likely occur in the near future. ... Read more

In this research project, an assessment of an abatement measure for mitigating railway induced vibrations is carried out. Ground-borne vibrations, which are primarily generated due to wheel-rail interaction, may also result in ground-borne noise in the buildings located in vicinity of railway tracks. An example of adverse environmental impact caused by ground-borne vibration and noise is the annoyance to people living those buildings. Assessing ground-borne vibration and noise is of crucial importance, especially in soft soils in which Rayleigh wave velocity is low and amplification of vibrations is more likely to occur. For mitigating the ground-borne vibration and noise exceeding the threshold values defined by technical standards in each country, abatement measures are applied. The main objective of this research is assessing the effectiveness of ‘concrete slab beneath ballast bed’ used as the abatement measure for reducing vibrations. For this purpose, Plaxis 3D based on Finite Element Analysis method is employed. Numerical model is created and validated through measurement data available from field tests conducted in the Netherlands. After having numerical model validated, several simulations are performed in order to study the factors influencing ground-borne vibrations.
From the results of this study, one can conclude that ‘concrete slab beneath ballast bed’ is effective in reducing vibration strength at all distances when train speed is considerably lower than Rayleigh wave velocity of the uppermost soil layer. It is notable, however, that the application of this measure may bring about amplification of the vibration strength in the vicinity of the track for trains running at higher speeds. Nevertheless, regardless of the train speed, there is always a reduction in the vibration strength at further distances from the railway track. From practical standpoints, this aspect is of interest for the buildings located in the far field. From the results of a sensitivity analysis on changes to the width and thickness of the concrete slab, it can be concluded that an optimal solution of concrete slab dimensions can be found. It is observed that by changing concrete slab dimensions, the maximum vibration strength is mostly affected in close proximity to the railway track. In addition, the dispersion lines and oscillatory moving load in the Wavenumber-Frequency plane are analyzed. Their intersection indicates that the moving oscillatory load excites a wave of frequency and wavenumber given by the intersection point. If these frequencies are harmful for the environment then concrete slab application can diminish their content from response. Sleeper passing frequency content increases when the concrete slab is applied. The obtained results and recommendations from this study can be used for further studying the other factors influencing the effectiveness of the measure. Examples of these factors include, among others, various ground conditions (e.g., soft soils of different stratification, local changes in soil proper-ties, etc.), and optimization of concrete slab dimensions, material parameters, as well as, cracked and uncracked concrete stage. The numerical model developed during this research study can be further employed to analyze different aspects of railway induced ground-borne vibrations. ... Read more

A composite slab consisting of in-situ casted reinforced concrete on profiled sheeting, which is connected to steel beams by shear connectors, is a common structural flooring system in office and multi-storey car park buildings. The headed welded studs, which are most widely used shear connectors, are inexpensive and easy to install because they can be welded to the steel beam through the profiled sheeting. A permanent link is created between the composite slab and steel beams leading to a time-consuming and expensive deconstruction process.

Various types of bolted shear connections, recently investigated by various researchers in Europe, Australia, and the USA, provide a demountable alternative for the flooring system. A part of this thesis describes the experimental study using a bolted shear connector consisting of an embedded bolt/coupler and external bolt, originally developed for a prefabricated solid concrete deck.

A full-scale composite beam was tested in two life cycles under total working loads up to $200kN$ in a 4-point bending set-up. In addition to bolted shear connectors, a timber joist was embedded in the composite slab over the web of the steel beam. After the first life cycle, the timber joist provides the cut edge of the slab. The experiment is used to model behavior of the composite beam in the first life cycle. The slab is then cut, demounted, re-assembled and tested again in the second life cycle. The load was applied up to $200kN$ and finally to failure. Multiple arrangements of shear connectors were investigated in second life cycle to analyze the performance of a prefabricated composite beam

Experience gained by the experiments on the composite beam in the first and the second life cycles is accompanied by FE analysis. Recommendations for practical use of the demountable composite floor system are proposed based on the experimental and numerical findings.

In addition, an investigation in the field of BIM (Building Information Modeling) functionality in the context of demountable structures was conducted. In order to identify the potential benefits of the BIM a case study of an in-situ casted car park was conducted. A number of software packages were used to conduct structural analysis, modeling and visualization of the construction sequence. As a result of this case study, valuable experience was gained on an application of BIM technologies for a design of demountable and reusable structures. ... Read more

Differential vertical shortening (DVS) is the relative vertical shortening between two adjacent vertical load bearing elements. DVS originates because axial loading conditions on- and the design of adjacent vertical load bearing elements are different. Due to these differences, the reaction of the adjacent vertical structural elements expressed as length change can be different.

The aim of this thesis is to research differential vertical shortening effects in high-rise buildings that use a concrete core as a lateral stability system and a timber pendulum structure as a gravitational system. The Tallwood House in Brock Commons is a perfect example of such a structural system where the engineers have considered the shortening effects which will be reviewed in this research. Furthermore, this research will look for measures in the design and implementation phase that have influence on the magnitude of differential vertical shortening deformations.

In the Tallwood House project the problem was only tackled on basis of the individual column shortening and the effect it would have on vertical mechanical systems. A clear understanding of the relative difference between core and column shortening (DVS) and the effect it can have on secondary building systems is lacking. The determination of criteria on which the DVS deformations are assessed in the Brock Commons building, are based on the deformation capacity of the vertical mechanical systems, which does not necessarily relate to the DVS deformations. A more methodological approach is necessary for the prediction of DVS deformations and the determination of criteria regarding DVS deformations.

The sub question have the aim to reach to a more general and methodological approach in predicting DVS deformations and determining criteria for DVS deformations.

“What are the criteria on which differential vertical shortening deformations in the building structure should be assessed in order to guarantee the functional performance of the building during its service life?”

“How can differential vertical shortening deformations be quantified for a timber-concrete high-rise structure?”

After answering the sub-questions that relate to the criteria on DVS deformations and the quantification of DVS deformations, a research can be conducted to the influence of some input variables for the design and construction process to answer the main question of this research:

“What are effective measures which can be applied in the design and construction phase to mitigate the differential vertical shortening during the service life of high-rise buildings that uses a timber gravitational load bearing system with stabilizing concrete cores?’’

Problem areas where DVS deformations can have a negative effect on secondary building structures are researched. A general approach for the determination of criteria for DVS deformations is elaborated, based on principles for vertical deformation criteria that are described by the Eurocode.

The response mechanism of axially loaded concrete load bearing elements and axially loaded timber load bearing elements on external influences is researched qualitative by a literature study. The CEB-fip 2010 strain model is used to predict deformations in concrete. For timber, the strength class system is used according to Eurocode 5 to determine the elastic strains. The creep and shrinkage strains in timber are determined by experimental results that are found in a literature study.

The influence of the building process on DVS deformations is researched by a literature study. Staged construction analysis provides the possibility to simulate the sequential loading in a building process and to distinguish the DVS-deformations that can affect secondary building elements (post-DVS deformations) from the total-DVS deformations.

A case study on the Tallwood House at Brock commons in Vancouver is conducted to provide a basic geometric model in which DVS deformations can be predicted in which all previous research in this thesis serves as input properties of the model. From this basic model, variables in the design and building process are altered to conduct a sensitivity analysis of these variables. The building height expressed in number of floors, column cross section and the building speed of finishings in a building are taken as the analysed variables.

Increasing the column cross section can be an effective measure to decrease post- and total-DVS deformations due to elastic and creep strains. The effectiveness decreases with the increase of the column cross section because shrinkage strains are not affected. The post-DVS deformations can be decreased by postponing the building process of secondary structural elements in the construction schedule. The effectiveness decreases with increasing building duration because DVS-deformations due to loads of the finishes itself are not affected. Total-DVS deformations are not affected. Compensation has effect on the total difference in vertical position between the floor supports. The vertical translational movement is not prevented. This means that post-DVS deformations cannot be influenced by compensation.
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Ordinary Portland Cement (OPC) consumption has grown nearly exponentially in the last twenty years. OPC has become the highest-volume manufactured product on the planet. Production of OPC is energy-intensive, consumes unrenewable natural resources and is one of the primary contributors to global warming (accounting for at least 5-8% of worldwide anthropogenic CO2 emissions). An alternative for OPC concrete is Alkali-Activated Concrete (AAC), for which Portland cement is completely substituted by an alternative binder. Instead of using OPC and water, precursors (raw materials) like Blast Furnace Slag (BFS) or Fly Ash (FA) are activated with an alkaline activator solution.
Although AAC seems to have promising qualities for structural application in terms of sustainability, worldwide use is not yet established. One of the reasons for this is the fact that there are no available regulations or codes to apply it, the material is relatively new and limited research has been conducted. For OPC concrete, the design codes are based on compressive strength at 28 days (strength at later ages stays either constant or is higher) and most other mechanical properties used in calculations are estimated based on this compressive strength. For AAC it is not yet sure if the same relations and assumptions as for OPC are also valid. First, because mechanical properties that have been reported for AAC in literature vary a lot, depending on mixture composition and curing conditions. Second, the long-term strength development of AAC is scarcely investigated and it is not clear if the compressive strength at 28 days can be used as a safe reference for design. Namely, a few researchers reported a decrease of strength or stiffness over time, for AAC mixtures that contain blast furnace slag. The observed decrease might not be a very desirable phenomenon and should be well-understood prior to wider structural application of AAC. Therefore, the main research question of this thesis is: Can a decrease of stiffness and strength over time, as sometimes reported in literature for AAC, also be found for AAC used at TU Delft and if so, what could be an explanation for this behaviour? Does the amount of BFS in the binder play a role, as a decrease over time has only been reported for AAC containing BFS? And if not, what other cause could lead to a decrease of properties over time? The intention is to make some first steps towards a better understanding of this phenomenon.
The research question is investigated in an experimental manner. Compressive strength, elastic modulus, splitting tensile strength and flexural strength are tested at different ages (28, 56 and 91 days) after being wet-cured (20°C and 95% RH) for 28 days. Two different AAC mixtures are investigated, S100 and S50, characterized by a BFS/FA binder ratio of 100:0 and 50:50 respectively. Furthermore, the flexural behaviour of reinforced beams is investigated by conducting four-point bending tests on both S100 and S50 concrete of two different ages (33/34 days and 69/70 days) and compared to an OPC concrete control beam.
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