Port of Rotterdam has the ambition to reduce the footprint for building new quay walls, this is in line with their ambition to reduce the footprint and with national goals to limit global warming. The aim is to use less materials and/or use different design solutions. These reinforced structures are designed in a conventional way and the internal forces are determined by performing a Linear Elastic Analysis. The reinforcement is calculated using the internal forces and is based on the Eurocode 1992 -1-1. The conventional approach includes various assumptions that affect the amount of concrete and steel used, which influences the CO2 footprint, structure reliability, and costs. In order to know the effects of these assumptions, advanced nonlinear calculations are carried out using volume elements ... Read more

In the construction of subsoil structures, a common challenge is the presence of a high groundwater level in combination with the absence of a naturally impermeable layer or an environment susceptible to settlements due to lowering the groundwater level. To overcome this issue, a building pit with an underwater concrete floor (UCF) can be constructed. The UCF ensures structural rigidity and allows for the building pit to be drained such that a dry and safe subsoil construction site is obtained.

The objective of this thesis is to investigate how design efficiency of underwater concrete floors can be improved. In an effort to reduce material usage and achieve cost-effective structures, the following research question was stated:

“What is the influence of design parameters and how can parameters be adjusted to improve design efficiency of an underwater concrete floor, and to what extent can the addition of fibre reinforcement contribute to this optimization?”

A parametric model was developed to provide insight to the sensitivity of parameters and their impact on design resistance. Furthermore, the model was utilized to examine under what circumstances potential material savings can be obtained by implementing fibre reinforced concrete in UCF’s. This was accomplished through the evaluation and comparison of the minimum required thickness based on bending moment resistance in various scenarios, for both UCF’s and steel fibre reinforced UCF’s (SFUCF).

Results obtained with the parametric model established that, in order to enhance the bending moment resistance of an uncracked UCF, increasing the nominal thickness becomes relatively more effective compared to increasing the concrete strength class for higher normal forces. When utilizing a compression arch to obtain bending moment resistance, the implementation of ribbed tensile elements or an increase in nominal thickness are found to be the most suitable methods for increasing resistance. For enhanced shear force resistance, increasing the nominal thickness over the concrete class provides relatively more additional resistance for slender UCF’s. The results found that through the application of ribbed piles, most punching shear force resistance can be obtained.

Three use cases for a SFUCF were identified using the parametric model. When centre to centre (c.t.c.) distances larger than 4.4m are applied in combination with a substantial normal force, significant material savings of up to 0.3m thickness are possible, which equates to a reduction of material usage by 30%. For situations where the effective height of the compression arch is small, it was also found that material usage could be reduced by 30%. Perhaps the most significant use case for a SFUCF is when the normal force is close to zero, and additional normal force cannot be obtained through membrane action. In these situations, the application of a SFUCF can make an otherwise near impossible project feasible.

As a new design approach, a cost-based optimization tool was developed using the parametric model. An already executed UCF was evaluated using the tool, it was determined that a more cost-effective design could have been achieved, with potential savings of up to 30% in costs.
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When concrete is subjected to imposed deformations, stresses may develop. If at any point in time this stress exceeds the tensile strength of the material, the concrete will crack. Early-age cracking of concrete structures may lead to problems with durability, serviceability and aesthetics. During hardening of concrete the material properties are still in development. Therefore, to be able to predict the crack width, understanding of the stress- and strength development is required. In addition, concrete is a visco-elastic material which means that stresses are affected by phenomena such as creep or relaxation. If the design codes predict the crack width in concrete structures under imposed deformations accurately remain subject of debate. The CROW report published in 2021 [9] provided the starting point for this research. The aim of this study was to gain more insight on the background of the design codes, and to explain the fundamentals of the crack width prediction in case of imposed deformations. For this purpose, the following research question was formulated:
”What is the applicability of the design codes regarding the crack width prediction of reinforced concrete structures under imposed deformations?” From the literature study it became clear that the main difference between the design codes was related to which boundary conditions and cracking theory were applied. The majority of the design codes applied the well known tension bar model theory where both ends are fully restrained. In addition, there were also codes using the continuous base restraining theory in which the tensile member is continuously restrained along one edge. This made a huge difference in the prediction of the crack width. From the finite element analysis which was performed, it turned out that there is a difference between the steel stress development of imposed loading and imposed deformations. In addition, in case of imposed loading less cracks were developed than under imposed deformations. However, from this specific numerical analysis it turned out that the maximum crack spacing and crack width is smaller in
the imposed loading model in comparison to the imposed deformation model. The only explanation for this is that in case of imposed loading the cracks are more evenly distributed. A case study was used to simulate the hardening process of concrete in combination with autogenous shrinkage as imposed deformation and compared with a finite element analysis. The goal was to determine a set of model properties that are useful for future engineers. The accuracy of the input parameters was verified with the experimental work carried out by M. Sule. Overall, when performing a non-linear finite element analysis a lot of knowledge was required. It turned out that specific choices such as the constitutive model type, the kinematic and equilibrium condition have a major impact on the outcome. Using the modified Bar model of Lokhorst in combination with this numerical approach resulted in good agreement with the experimental findings.

The parameter study showed that regarding the tension bar models, the bar diameter has the largest influence on the crack width prediction. While with respect to the continuous models there was no onesided answer to the question which parameter had the largest influence on the crack width prediction. In one of the design codes based on the continuous model theory named CIRIA [8] the degree of restraint clearly stands out as the most important parameter. Whereas in the another design code based on this theory, namely the ICE [4], all parameters that were investigated in this thesis have limited effect on the crack width prediction. The design codes considered in this master thesis do not yet fully represent the crack width due to the hardening of concrete or due to autogenous shrinkage. The design codes are applicable for the
crack width prediction of reinforced concrete structures under imposed deformations if conservative assumptions such as a weak bond between concrete and steel reinforcement are taken into account. It is clear that the problem treated in this report has more complexity than what one initially may think.
Opinions on how to determine the crack width of reinforced concrete tensile members under imposed deformations differ. The difference is related to the type of restraint and the cracking theory which are suggested in most used analytical design models. This report contributes to a better understanding of
the crack width development under imposed deformations through non-linear finite element analyses and verification with experiments. The results from this master thesis suggest that an approach to a more consistent crack width prediction under imposed deformations should investigate how bond in the interface between concrete and steel influences cracking. This has lacked attention in the current formulas in the design codes.
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A parking garage of Eindhoven airport partially collapsed in 2017. It was caused by failure of the longitudinal joint (long-side) of the composite plank floor or breedplaatvloer on the roof level. Experimental and numerical research showed that the joint suffered high positive bending moment in its transverse direction. However, from the investigation results, there was not enough resistance at the concrete-to-concrete interface around the joint to transfer the tensile force from the precast to the cast-in-situ section, which led to delamination of the two layers of concrete and resulting in failure when the delamination crack reaches the end of the coupling reinforcements. As happened in that case, the concrete-to-concrete interface usually is the weakest link and has a critical role on behaviour of a composite concrete system, especially the one which has unreinforced interface (no stirrup near joint). Further studies have been conducted to understand the influence of various details around the joint on the interface behaviour. In this thesis, details in spacing between lap splices (coupling reinforcements in cast-in-situ layer and bottom reinforcements in precast layer), spacing between connecting reinforcements (stirrups crossing the interface near the joint), the role of connecting reinforcement, and the sensitivity of interface parameters were studied numerically using DIANA finite element analysis software. Since the spacings are in direction of the specimen’s width, interface behaviour was analysed in both longitudinal and transverse directions. An additional study about compressive membrane action or arching was also conducted to understand the influence of lateral restraint, which usually occurs in composite plank floor systems used in buildings, including the one used in Eindhoven parking garage, to the capacity of the structure. This action was suspected of providing additional strength to the existing composite plank floor

Two composite SHCC-concrete beam specimens from the experimental research by Harrass [1] were used in this numerical study since the experiment had both unreinforced and reinforced interface specimens which were important for this study. The unreinforced interface beam (Sample 1) was suitable for the study of lap splice spacing and lateral restraint without any influence from reinforcement crossing the interface, while the reinforced interface beam (Sample 7) was suitable for the study of stirrups spacing. The specimens are solid beams (without weight-saving element) consisting of a SHCC (Strain Hardening Cementitious Concrete) precast layer with a joint in the mid-span, and a regular concrete cast-in-situ layer. By using DIANA 10.4 finite element analysis software, this study is able to simulate both specimens in 2D and 3D numerical models. The models represented Sample 1 failed with a horizontal crack along the interface and a flexural crack at the end of coupling reinforcement reaches the top of the cast-in-situ layer, while the models represented Sample 7 failed with a horizontal crack along the interface, a flexural crack at the end of coupling reinforcement, and a crack at the stirrup location in precast layer. From the verification study, the reinforcement bond-slip function (CEB-FIB 2010) was chosen not to be used for the rest of the study since it did not affect much the load capacity and the failure mechanism of the specimens. Consequently, pull-out failure of the stirrup is excluded for the rest of this study.

Prior to the main study, the influence of each interface parameter was studied in both unreinforced and reinforced interface models by varying the interface parameters. It was observed that interface tensile strength and stiffness are governing in the unreinforced interface model. Within the range of those parameters, the load capacity was increased and decreased by more than 50% in compared to the reference model verified by Sample 1. By adding a rectangular stirrup near the joint of unreinforced interface model, the model with reinforced interface has a different governing parameter, the cohesion, and the variability of the results decrease. Within the range of the cohesion, the load capacity was increased and decreased up to 30% in compared to the reference model verified by Sample 7. Since the interface parameters influence the capacity of both unreinforced and reinforced interface beams, two different interface types are used for the whole of the study. They are known as “smooth interface” which uses the parameters obtained from the verification with the experimental specimen, and “perfect bonded interface” which use rigid connection between the elements of the two concrete layers.

To study the influence of lap splices spacing, models with three lap splices setup from Harrass’ experiment (three coupling reinforcements and three bottom reinforcements) were compared to models with a single lap splice (one coupling reinforcement and one bottom reinforcement) with the same total reinforcement area. As a result, with perfect bonded interface, model with single lap splice has higher load capacity by more than 10% in compared to model with three lap splices though both models failed with the same failure mechanism which was the horizontal crack along coupling reinforcement and a flexural crack at the end of coupling reinforcement reaches the top of the cast-in-situ layer. Stress concentration around coupling reinforcements were observed in all models, especially in model with single coupling reinforcement. However, different horizontal crack propagation occurred in each models. Uniform horizontal crack propagation along the interface were observed in models with smooth interface, while more concentrated crack propagation around the coupling reinforcements were observed in models with perfect bonded interface, especially in model with single lap splice. This different crack propagation in models with perfect bonded interface could be the cause of different load capacity since more uncracked elements could provide more tensile force transfer from precast layer to cast-in-situ layer.

In the study of the influence of stirrups spacing, models with rectangular stirrup (two legs) setup were compared to models with a single leg vertical stirrup setup with the same total reinforcement area. In both cases the presence of the stirrup near the joint stopped the propagation of the horizontal crack. As a result, all models could reach yielding of the coupling reinforcement for both interface types although different structural stiffness is observed. The plausible cause for this difference in structural stiffness was the higher tensile stress in stirrups of model with two legs stirrups compared to model with single leg stirrup. This higher tensile stress might be resulted by the more distributed stirrups across the width of the beam.

In the additional study, models with full height lateral restraint at the support were compared with models with simple support. As a result, with perfect bonded interface, model with lateral restraint has higher load and displacement capacity by more than 14 and 2.5 times consecutively compared to the model without lateral restraint. In compared to the collapse load, the numerical result of model with lateral restraint has higher load capacity by almost 4 times. With smooth interface, model with lateral restraint has higher load and displacement capacity by more than 10 and 5.5 times consecutively compared to the model without lateral restraint. In compared to the collapse load, the numerical result of model with lateral restraint has higher load capacity by more than 2 times. These increases are in accordance with a research by Ockleston [2] which found a considerable increase of load capacity on concrete slab with lateral restraint compared to the yield line theory. Part of the increase of capacity was resulted by the fix boundary action due to bending moment at support. However, it was observed that compressive membrane action started to develop after the first flexural crack as the horizontal force at support rapidly increased after that crack. Although the models with lateral restraint of both interface types had a different failure mechanism compared to the models without lateral restraint, they have a similar final stage of the failure mechanism, which is the flexural crack at the end of coupling reinforcement. This flexural crack propagation can be prevented from occurring earlier due to the high compressive stress at the top part of the cast-in-situ layer. When the concrete crushed at the support due to limited rotation capacity of the concrete, the compressive stress dropped causing the flexural crack at the end of coupling reinforcement to develop.

In conclusion, there was an influence of the interface behaviour to the failure and the capacity of composite SHCC-concrete beam. However, the influence was varied, depending on the coupling reinforcement spacing, presence of stirrup crossing the interface near the joint, spacing of stirrup, and interface type. It is also concluded that compressive membrane action in addition to fix bending action, which occurred due to the lateral restraint, increased the capacity of the structure. This increase depended on the interface type and rotation capacity of the concrete. A wider range of the influencing parameters are needed in future studies to get a more robust results which are beneficial for a more general conclusions. However, the series of experimental research based on this study are essential to provide a verification on the results of this numerical study. ... Read more

Conventional building methods are still based on the reinforced concrete industry. In the last decades, timber has become more popular because it could be a more sustainable alternative. However, pure timber is not always an option, especially when slender design is required by the client. Because of its low elastic modulus, deflections often require an increased deck height. Therefore, this research focuses on the strengthening of timber bridge decks with reinforcement and prestress in order to increase their slenderness (= the ratio of the span to the height of the cross-section). This might make timber decks more competitive to reinforced concrete designs regarding slenderness. The problem is that prestressing timber decks will lead to creep deformations that induce losses of prestress force. This research is focused on modelling the creep deformations and the resulting resistance losses of prestressed timber decks.

First, a cross-sectional model is developed to be able to find the initial resistance of a reinforced- and prestressed timber deck. This model is based on an incrementally increasing curvature so that the deck behaviour can be quantified from zero load to the failure load. Second, a time dependent model is developed to find the displacements and resistance through time. The timber bridge deck is modelled with ODE systems. The ODE's are used to find the (1) displacements and (2) strains of the deck. To obtain the time dependent behaviour of the deck, a viscoelastic E-modulus is substituted into the displacement- and strain equations. This viscoelastic E-modulus decreases with time, which causes an increase in displacements (= creep displacement). In the same way, the strains are modelled over time. The time dependent creep stains are implemented in the cross-sectional model to find the reduced resistance of the timber deck.

The outcomes of the model suggest that large prestress forces lead to negative creep deflections (= creep in upwards direction). Meaning that for the right value of the prestress force, also zero creep deflections can be obtained. Besides creep, the instantaneous deflections are a large part of the total deflections. According to the results of the model, the instantaneous deflections can be decreased by up to 70%. Regarding the resistance, the final increase of bending moment resistance can reach up to 30% by incorporating prestress (at t = 50 years, including losses due to creep). Due to creep, prestress force is lost over time, resulting in a decreased deck resistance. This research shows that the creep losses result in a bending moment resistance decrease of up to 12%. Taking this into account, a bridge deck with a slenderness of 31 to 33 will be able fulfil its requirements after 50 years of service life. Depending on the client requirements, a slenderness of over 34 can be reached.

Using Eurocode, creep deformations are calculated with a simplistic and conservative method. The model that is built in this research gives a more advanced way of determining the creep deformations of a timber deck. This leads to more realistic quantification of creep behaviour. However, Several factors still cause uncertainty in the model. Therefore, experiments with timber decks should be done to obtain more accurate data for the creep behaviour. The model from this research can be calibrated according to data from experiments, which will increase the reliability of the results. ... Read more

To date, many fire accidents have occurred in tunnels all over the world. In the worst cases, there were catastrophic consequences with numerous human casualties and significant economic impacts. In the occurrence of such tunnel fires, besides the primary concern of saving human life, ensuring a certain level of structural integrity is also desired. Looking from the latter perspective, this thesis is focused on the fire-induced thermal exposure in concrete tunnels, aiming at coupling numerical simulations of idealized fire scenarios in computational fluid dynamics (CFD) software with the use of FEA for the analysis of structures, moving towards a performance-based approach in replacement of the currently adopted prescriptive approach.
In this sense, fire imposes one of the most hazardous conditions for concrete structures, characterizing severe thermal degradation of the mechanical properties of the material. During fire exposure, steep thermal gradients are formed within the concrete structure. Those will always lead to the development of thermal stresses, the state of which being determined by several conditions (i.e. elastic modulus, thickness and supports). Besides the structural consequences of a fire, this thesis also deeply investigates the interface between a fire and the structure, which involves the interaction of three different modes of heat transfer, namely conduction, convection (related to the gas temperatures generated by a fire), and radiation (related to the radiation temperatures generated by a fire). While conduction within the solid phase regulates the amount of heat absorbed by the structure during a fire, radiation overcomes convection and becomes the primary mode of heat supply to the structure. The adiabatic surface temperature (AST) combines both the radiation and convection contributions to the total heat transfer to the structure into a single term, fully characterizing the fire phase in the structural analysis. Based on this concept, the differences between the two methodologies (i.e. prescriptive-based and performance-based) are exposed. From the prescriptive-based perspective, the development of the RWS curve and its indistinct use among protected and unprotected concrete tunnels is deeply discussed, together with the current fire resistance furnace tests. For the performance-based approach, the thermal exposure generated by two pool fire scenarios (200 MW and 30 MW) within the Piet Hein tunnel is addressed and the effects of longitudinal ventilation are highlighted.
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New and existing bridges in the Netherlands must abide by structural safety codes, such as the Eurocode. In this code, structural safety is expressed through the reliability index 훽. For certain reference periods a threshold value for 훽 exists. When applying prescribed load models given in the Eurocode, the structure is guaranteed to at least fulfil to this threshold value. However, these prescribed load models are deterministic in nature and can be rather conservative for bridges in urban areas. This thesis focusses on creating a probabilistic load model based on actual traffic loading by making use of a camera system that registers license plates to check whether the vehicle is allowed to enter the inner city of Rotterdam due to environmental zones. From this camera system data, technical information such as wheelbase, legally allowed axle loads, gross vehicle weight and such can be extracted since they are coupled to license plates. This technical information is then used to create load models based on actual registered traffic. This load model represents trucks as point loads with interspatial axle distances. In total, one year of collected data by the camera system is stored, called the LP data. This load model is then used in a probabilistic reliability analysis as a load variable input. When comparing the LP data with available weigh-in-motion (WIM) data from two measurement locations in Rotterdam, it turned out that the LP data does not incorporate under- and overloaded axles and was overestimating the accompanying reliability index. Hence to account for this, an axle load factor 휂௜ is introduced to simulate under- and overloaded axles. This factor 휂௜ is based on the WIM data and is different for each vehicle type. With the use of this factor, a second, improved load model is constructed. This is referred to as the modified LP data. A third and final load model was constructed from the available WIM data, called the WIM model. For each of these three load models the load effects were calculated, and distributions were fitted accordingly for simulating several 25 year periods of traffic. The output of these load models is a loadeffect maxima distribution that can serve as a direct input in a probabilistic reliability analysis. With these three load models, a hypothetical slab with a span length of 10 m was probabilistically analysed where the LP model, the modified LP model and the WIM model resulted in reliability indexes of 4.8, 4.1 and 3.7 respectively. When compared to the requirement in the Eurocode, all load models comply. Concluding from this, the modified LP model suggested in this thesis can be used as a load input in a probabilistic verification for this very considered bridge location. For this load model to be applicable to multiple bridges, more research must be done since only one location was considered in this thesis. However, the suggested approach to construct load models based on license plates can be used verify the applicability to multiple bridges. ... Read more

Starting from the late eighties induced seismic activity is present in the Northern part of the Netherlands. Cause of these earthquakes is the extraction of natural gas. In this region, most of the building stock comprises out of unreinforced masonry (URM) buildings. Multiple experimental campaigns are performed since 2014 to investigate the structural integrity of these type of structures. Both static and dynamic, full-scale and smallscale, experiments are executed to identify both in-plane and out-of-plane failure mechanisms. Strengthening, or retrofitting, of these already existing structures, is of interest and different researchers propose multiple techniques. From the literature, it is found that the application of strain hardening cementitious composites (SHCC) results in the required improved structural performance of the retrofitted masonry. The SHCC material is characterised by high ductility in the range of 3-7%, tight crack widths of around 60 μm and a relatively low fibre content equal to 2% (maximum by volume). In this experimental campaign small-scale, both inplane and out-of-plane (i.e. shear strength and flexural strength, respectively), experiments are performed on masonry samples retrofitted using a single-sided applied SHCC overlay. Different thicknesses of this overlay, masonry surface preparations, and overlay curing conditions are considered. With the help of these experiments the material properties of retrofitted masonry are investigated. From the initial shear strength experiments, it is concluded that the retrofitting approach did not work as intended. Results of all the different specimen examined shows similar capacities to the non-retrofitted masonry triplets. With the help of digital image correlation, it is shown that for all of the retrofitted specimen, the overlay material is not activated during the tests. Additional experiments and numerical simulations are performed to investigate the several parameters possibly influencing these experiments. The bond strength of the interface between the SHCC and the masonry substrate is determined to be too low. This is one of the main factors resulting in the absence of cracks in the retrofitting overlay. Additionally, the high cracking strength of the SHCC mixture considered, and the applied pre-compression, have influenced the cracking behaviour of the retrofitting overlay. Besides the shear strength of the retrofitted masonry material also the flexural strength is investigated with multiple out-of-plane four-point bending tests. Retrofitted masonry beams are used for these experiments. The plain masonry beams are not able to carry their self-weight, therefore all of the additional capacity is accommodated to the applied overlay. The experimental results are governed by shear failure. For eight out of ten specimens debonding of the masonry units is prevalent. Two of the retrofitted masonry beams showed flexural failure. A thicker overlay will result in higher flexural strength. Again, the bond strength between the overlay and the masonry substrate seems to be governing. No numerical analyses are performed to analyse these experiments in more detail. From this research, it is concluded that a single-sided SHCC overlay can be a very attractive method for retrofitting unreinforced masonry. However, both the interfacial bond strength and the material properties of the SHCC material must be taken into account. The bond strength must be sufficiently high, and the cracking strength of the overlay material sufficiently low, for the overlay to be activated. With the help of numerical simplified micro-models, the requirements of both parameters can be estimated. ... Read more

Compressive membrane action is a phenomenon commonly found in reinforced concrete structures after significant cracking and deformation have taken place. In this thesis report, the potential benefit of CMA in immersed tubes subjected to fires is quantified through a finite element study. Furthermore, sensitivity studies are conducted in order to determine the boundary conditions necessary in immersed tubes to induce CMA. ... Read more

A lot of concrete structuressufferingfrom ASR show a decrease in material properties. However, it is not clear what might be the influence of ASR on structural behavior. Influence of restraint is often ignored in material property measurement, while reinforcement is present as a restraint of ASR expansion in most structures.Thisresults in so called chemical prestresseffect, whichshould not be neglected. In the presented study,the result indicatesthat neglecting the chemical prestresswould miss the failure mechanism transition and lead to a lowerbeam stiffness. Therefore, a newway to model ASR-affected structures is proposed, called the ASR-layered model.The numerical analysis is done with ATENA.Depending on the reinforcement arrangementand amount, with longitudinal reinforcement acting as a restraint, expansion to the greatest extend occurs in the direction of least confinement and the cracks become parallel to reinforcement. Considering the potential to connect with each other and form long horizontal cracks, the ASR crackingin restrained structuresare modelled as horizontal layers with reduced material properties. The propertyreduction is concentrated in ASR layers only, this local reduction is more realistic than the traditional method done by (Ferche, Sheikh, & Vecchio, 2017)in which a global reductionon material propertiesis applied. For chemical prestress, it is difficult to separate the influence of prestressin experiments,so experimentalresult is always affected both by the reduction of properties and prestress and probably some other phenomena that exist. The chemical prestress effect is modelledherein the way of physical prestress, but the expansion of ASR gel in chemical prestress would possibly influence the bond strength between concrete and reinforcement, so bond model is also considered.Some conclusions can be drawn on this study. The material reduction caused by ASR would only result in a decrease of load capacity. While in combination with prestress, the load capacity of ASR affected beam may be increased to be even higher than the unaffected beam. The application of prestress could also lead to the possible change of failure mechanism from shear to bending failure, whichis also observed in experiments. Including the bond-slip effect in prestressed ASR-layered model provides a better fitting with experimental results,but the influence of ASR on bond strength remains unclear. With parameter study, no obvious influence on ASR-affected structures could be linked to a/d ratio and reinforcement ratio. 1 or 2 ASR layers will only influence slightly on the ultimate load. The limitations of this model exist, the expansion caused by ASR is not directly modelled. Information on ASR layer property is quite limited, it would be difficult to measure the cracking part of ASR affected structures alone. In addition, the chemical prestress and possible cracking depend on the amount of ASR expansion as well as the reinforcement arrangement and amount, but they are not considered to correlate with each other in this model. ... Read more

Rapid extraction of gas in the north-eastern Groningen province of the Netherlands has led to an increase in the occurrence of induced earthquakes in the region due to subsidence of gas bearing sandstone layers. This process manifests itself in the form of ground motions at the surface. Netherlands, historically being an inactive tectonic zone, has not paid much attention to detail structures withstand lateral seismic forces in the past. This has led to an alarming situation amongst the residents and government authorities since damage has been reported in the form of claims for compensation. The predominant presence of old masonry houses has further aggravated the situation because of quasi-brittle material characteristics weak in tension. A large-scale research campaign was launched after the historical seismic event at Huizinge in 2012 with an aim to assess and safeguard building structures in the region although much of the research has been focussed on behaviour of masonry houses. NPR 9998 which serves as a national guideline in the Netherlands for seismic assessment and retrofitting was published and is continuously being updated with the latest developments. However, it is equally important to address other typology of structures in terms of material and geometry. With this objective, it was decided to start with a fundamental study on the seismic analysis methods with specific regards to steel structures.

The present thesis provides a comprehensive review of the lateral behaviour of affected structure initially and the fundamental differences in the induced earthquakes when compared with deep tectonic earthquakes. This is followed by state-of-the-art of linear and nonlinear seismic analysis methods which forms the basis of guidelines & codes presented in the NPR 9998 and EN 1998 context. Further, an understanding on the generation of seismic action in response spectrum format from recorded ground motions which is the most widely adopted one across seismic design codes worldwide. The case study adopted for this study is a steel office building preliminary designed for non-seismic actions. Global seismic demands are determined using linear-static and linear-dynamic analysis methods with verification of specific criteria to be satisfied for safety of steel structures. Modelling parameters and methodologies are discussed in detail with regards to using simplified numerical models for analysis based on recommendations from Eurocodes and Internaltional codes. A variation model to assess the likely performance level using nonlinear static pushover analysis for a specific intensity of ground motion in terms of peak ground acceleration was made. Conclusions in the form of applicability of analysis methods are made towards the end with affected structures primarily vibrating in the fundamental mode, the present study can serve as a reference guide for a practicing engineer carrying out seismic analysis. Discussions about the background of design principles is made alongside the analysis for a clear understanding.

This thesis is expected to fill the knowledge gap for a design engineer carrying out seismic assessment of structures in the Groningen region of the Netherlands by providing a fundamental understanding of seismic demands imposed on a structure and assessment of capacity deficiency by carrying out non-linear pushover analysis. Recommendations based on NPR, Euro codes and International codes have been made to simplify numerical modelling of the structure. Similar analysis can be undertaken for other types of structures prone to be affected by induced earthquakes by adopting corresponding material nonlinear models and considering level of interaction with the ground in terms of soil-structure interaction where the same may lead to modification of structural response.
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It has been reported that due to the rapid urbanization and economic growth the municipal solid waste (MSW) would double in volume from 1.3 billion tons per year (in 2012) annually by the end of 2025, challenging environmental and public health management worldwide. Given that, most of the MSW incineration (MSWI) bottom ash (BA) are disposed in landfill currently, and technically and economically viable techniques for the reuse and recycling of MSWI BA is still at a premium. This issue would seriously challenge the environmental and public health management worldwide.
In some European countries and the US, MSWI BA has been utilized as aggregate in pavement construction or as aggregate in concrete. Previous studies also proved the feasibility of using MSWI BA in concrete, either as aggregates or binder substitute materials. However, it is worth noticing that there are several significant drawbacks of using MSWI BA in concrete, including the potential risk of leaching due to the existence of heavy metals and harmful salts, the low reactivity due to high content of quartz and unburned organic matters, and the metallic aluminum-induced expansion.
Therefore, in this study, a characterization of as-received MSWI BA was conducted at the beginning to find out the potential problems when used in concrete, namely the metallic aluminum content, low reactivity and unburned organics. A comprehensive pretreatment was performed subsequently to solve the problems. Specifically, both physical and chemical treatments were carried out to get rid of the metallic aluminum in BA. Afterwards, thermal treatment was conducted to enhance the reactivity of BA and remove the unburned organics. Pre-treated BA samples were characterized again to reveal the effectiveness of pretreatment. The results showed that both chemical and physical treatment were highly effective in removing metallic aluminum. Meanwhile, thermal treatment was proved to be a proper activation method which also removed the remaining organic matters through the high-temperature process.
Subsequently, the investigations of the effects of pre-treated BA addition on compressive strength, reaction products and hydration heat development were conducted on cement paste level by varying the replacement material (BA with different treatment methods) and ratio. A proper method of pretreatment was proposed as well as an optimization of a maximum replacement level of BA in cement paste without detrimentally influence the performance of concrete paste was studied. Compared with nonreactive micronized sand (only works as filler) and pure cement, the addition of physically treated BA has a certain amount of contribution to the hydration process from the viewpoint of heat release. Results show that BA do have pozzolanic activity but is much lower than cement, and physically treated BA is suitable to be used as filler in concrete. Additionally, physically treated BA was further activated through thermal treatment according to the result of compressive strength test, which delivered the highest strength among all the treated BA under the same replacement ratio.
Finally, to extend the application of MSWI BA in concrete, the mix design was made by blending treated BA with the highest compressive strength into concrete and make it suitable for structural application. The effects of treated BA addition on the workability and compressive strength of concrete were investigated. The addition of treated BA brought slight negative impact both in workability and strength due to the existence of nonreactive phases in BA (quartz and organics).
Accordingly, this study proved the potential of BA with proper treatment to be used as a cement substitute material in concrete as well as promoted the understanding of the influence of BA on the hydration process, which also brings the possibility that BA could be widely reused in concrete system in future industry.
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Underground infrastructures and the importance of the people’s safety and structures robustness are relevant and contemporary issues in the civil engineering industry. The demand for this infrastructural typology has developed to such an extent that the need for a better and cost-beneficial knowledge of the risks is necessary.
This thesis aims at bridging and developing further the knowledge on Fire safety engineering and structural engineering on the particular topic of spalling failure. Another objective of this thesis is the discussion over the possible replacement of the used procedures used to assess and guarantee tunnel safety. Both from a fire safety and structural engineering point of view, prescriptive measures and solutions are mostly proposed to accomplish a safe tunnel design. This causes the design to be non optimised and in some cases more costly than what is actually needed.
From the fire safety side, the use of pre-given fire curves is put under discussion. Research has been conducted to asses which are the origins of the most widely used curves. Studies have also been performed to develop a practical analytical engineering method to analyse and estimate the consequences of a given fire scenario tailored to the specific tunnel under consideration. Subsequently the results of the analytical models have been compared with the results obtained with advanced Computational Fluid Dynamics tools. Finally, more complicated scenarios have been studied with the use of this software.
On the other hand, from a structural engineering point of view, a new model able to describe the spalling mechanism has been proposed. The model predicts the spalling time for NSC elements and at the same time verifies which is the optimal thickness for the piece to spall. On top of that the possibilities for further use of the model in the description of the spalling mechanism for HSC and PPFRC elements have been investigated.
Finally this two topics have been combined together and conclusion have been drawn.
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