Dissertations for Structural Engineering (Str.E)

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    Modal Dynamics of Combined Offshore Wind Turbine and Monopile Foundation System: A Seismic Impact Assessment Study on System Dynamism
    (The British University in Dubai (BUiD), 2023-12) VENUGOPAL, HARIKUMAR; Dr Gul Ahmed Jokhio
    For the sustainability transition to evolve at a rapid pace, complex engineering systems are required to be reliable and effective in their operability. Even though offshore wind energy systems are a few decades old now, global adoption is not strong due to reliability issues, construction, operation, and maintenance complexities. The primary uncertainty in the structural engineering of this system lies in the dynamic behavior which is almost impossible to accurately compute. Seismic interactions at the seabed further complicate this. This dissertation conducts an in-depth modal dynamics analysis of an integrated offshore wind turbine and monopile foundation system, employing finite element analysis techniques. The study encompasses frequency domain analysis, eigenvalue extraction, and modal dynamic steps, incorporating seismic loads inspired by significant earthquake events, and the seismic impact on the system's dynamism is evaluated by evaluating system field and history outputs across system modal dynamics. Critical insights regarding the geometric variation effects on the dynamic traits of the combined system are retrieved by careful comparative evaluation.
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    Comparison between Nonlinear Analysis and ACI Simplified Effective Stiffness Analysis Methods for Reinforced Concrete Frames Under Lateral Load
    (The British University in Dubai (BUiD), 2023-11) ELMUTASHY, HAJER; DR GUL AHMED
    When reinforced concrete frames subjected to lateral load manifesting in inelastic damage in the form of cracks that diminish the structural element's stiffness. Evaluating this damage often employs non-linear analysis, yet simplified methods prescribed by international codes and numerous studies estimate the effective stiffness of these elements are used for elastic linear analysis. The accurate estimation of effective stiffness is crucial as it profoundly impacts the overall structural performance. This research endeavors to compare the non-linear performance of the structure with the linear performance using the assumptions proposed by ACI-318-19, permitting the use of 0.7EIg and 0.35EIg as effective stiffness values for columns and beams, respectively. To achieve this, 66 one-bay one-story frames are modelled and subjected to non-linear static analysis using ETABS software. The model parameters encompass compressive strength, reinforcement ratios, column height and axial load. The analysis presents load-deflection characteristics for the entire frame which used to calculate the effective stiffness. Results subjected to statistical analysis which indicate that increasing compressive strength augments structural stiffness, whereas heightened axial load and frame height notably diminish stiffness. Conversely, employing the non-linear analysis method result in higher effective stiffness than simplified method by mean value of 1.36, 1.44 and 1.57 for frames with compressive strength 40,80 and 120mpa respectively. Keywords: effective stiffness, static nonlinear analysis, simplified stiffness method
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    Comparative Study of the Structural Behaviour of Cast Acrylic & Laminated Glass Under the Impact of Dynamic Loading in Aquatic Applications
    (The British University in Dubai (BUiD), 2023-12) ABUZOUR, MOHAMMED A. E.; Dr Gul Ahmed Jokhio
    Laminated glass (LG) and cast acrylic (CA) materials have differences in their structural behaviors regarding the impact of dynamic loading in aquatic applications. The difference can be due to these materials' consistency and mechanical properties. This study aimed to distinguish the differences in structural behaviors of cast acrylic and laminated glass in aquatic applications under the impact of dynamic loading and what industry guidelines and standards can be developed to ensure their safe and effective use in this setting. The study starts in Phase I by selecting the strip method for both LG and CA to observe the deflection magnitudes of hydrostatical pressure of a 40mm thickness tank wall that has a depth of 6m, and then a shell element model for both materials was built using CSI SAP software to establish accurate statistical modeling of the tank with same wall thickness and exerted hydrostatic pressure depth. The results in Phase I exhibited that CA sheets had 10% to 15% more deflection than it was in LG, and experienced negative bending moments of about 90 kN.m near the base edges, and around 40 kN.m as maximum positive bending moments. Whereas LG’s straining actions recorded a magnitude close to 100 kN.m as positive bending moments and almost 180 kN.m as negative bending moments near the edges at the same parameters of the study. In Phase II of the study, the materials were submitted to dynamic loads analysis to examine their structural boundaries. The model was established using LS Dyna software to mimic an accidental collision incident of amphibians and/or mammal creatures to the LG and CA tank walls. Masses, velocities, hydrostatic pressure, and wall thicknesses were all included in Phase II of the study to assess the impact of each variable on the built model. The study achieved accurate simulations since there were four different parameters in each analysis running cycle allowing sophisticated investigations of both materials by pushing their structural behavior under the impact loads of collisions to their extreme boundaries, especially when gradual incremental changes in the magnitude of each parameter are applied. The model was adjusted to compare the actual deflection and applied stress criteria with the aforementioned four variable parameters. The obtained results exposed the superiority of CA sheets in most of the collision cases in contrast with LG. CA sheets had the least deflection and stress values in regard to wall thickness, however, they showed a gradually increasing deflection against higher velocities in contrast with LG which revealed rather constant deflections versus the same set of velocity increments. LG sheets expressed a dramatic increase in the applied stress against the increment of the colliding mass, however, they could remain more conservative against recorded deflection magnitudes under the same increment set of moving mass. Finally, CA sheets recorded slightly lower deflection values than it was in LG under the increasing effect of hydrostatic pressure (collision depth) and eventually showed almost a constant behavior of stress but significantly lower than those recorded in LG sheets.
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    Corrosion Monitoring Technologies for Reinforced Concrete Structures: A Review
    (The British University in Dubai (BUiD), 2023-06) SHEHADEH, KHADIJA; Dr Gul Ahmed
    Reinforced concrete (RC) structures are susceptible to many problems which would lead ultimately to the degradation of RC structures or a total loss in the worst-case scenario. Corrosion represents one of the main degradation sources. Due to the vital impact size of corrosion of RC structures in the form of high maintenance demand and an increase in the total life cycle cost, corrosion monitoring, early detection, and timely remediation is considered a necessity and a crucial proactive measure to control corrosion and limit its impact. In this work, the main classifications of corrosion monitoring systems were explored, highlighting their features, advantages, disadvantages, and future recommended works. To achieve that a state-of-the-art literature review was employed. Six main categories were identified from the literature: visual inspection, electrochemical methods, elastic wave methods, electromagnetic methods, fiber optic sensing methods, and mechanical methods. The subcategories of each of these were reviewed highlighting its concepts, pros, cons, and outlook and future works. Irrespective of the adopted processes for corrosion monitoring, it was concluded that none of these methods represent an optimum solution by itself, where employing a combination of multiple systems is one way of optimizing its results. New technology, algorithms, data processing, and AI are new approaches to improving corrosion monitoring processes. However, it needs further development and research.
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    Experimental Investigation on the Flexural Behavior of Composite Floor Panels Made of Cold-formed Steel and Timber for Sustainable Construction
    (The British University in Dubai (BUiD), 2023-07) DANDASHI, SEIFALDEEN ALAHNAF
    Composite floor made of timber and steel have gained popularity and extensive application in the construction sector over the past few years. Unlike concrete-steel composites, the composite behaviour between timber and steel is not fully explored. This research investigates experimentally the flexural behavior of three full-scale specimens composed of cold-formed double cee joists connected to laminated veneer lumber using self-tapping screws. Each specimen in the set has a different screw spacing, and the degree of shear interaction was assessed by subjecting the samples to four-points loading. The deformed shapes were described, and the displacement at the midspan was plotted against the applied load. Accordingly, the initial stiffness was calculated and validated against the predictive theoretical models available in the literature. Moreover, the conformity of the proposed system was verified against the deflection and vibration criteria available in the relevant standards. Finally, the environmental impact of implementing the suggested system was evaluated by calculating the upfront carbon. The result were discussed with respect to the outputs of a benchmark reflects the conventional construction practice. As a conclusion, the proposed system adequately fulfils the strength and stiffness criteria for domestic buildings, and significantly reduces the GHG emissions attributed to construction sector.
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    Structural design and cost comparison between a concrete structure and steel a structure of a tall residential building in Dubai subjected to seismic and wind loads.
    (The British University in Dubai (BUiD), 2022-10) ELNAIM, OSMAN OMER MEHMOUD
    There are many materials and structural systems of buildings over the world such as Steel structures, Concrete, Wood, Stone and Brick/Masonry. Apparently, each one of them is having its properties and limitation of use. Nevertheless, the famous structural systems that used for designing and constructing the skyscraper are the steel and concrete structures since the Wood, Stone and Masonry cannot be used in the tall buildings. It is very significant to compare between the steel structure and concrete structure when designing a skyscraper, to withstand the Seismic, Wind load, Live, Dead loads and to make the cost analysis related each one to choose the better one. Obviously, each structural system has advantages and disadvantages which should be taken into consideration when selecting one of them. In this dissertation, a comparison is made between the two tall buildings which made of reinforced concrete and steel in Cross section of structural element, Durability, Resistance to Earthquake and Wind loads, Load carrying capacity, Self-weight, Construction cost, and Construction speed. However, the steel and reinforced concrete skyscrapers are designed using ETABS program, the post tension slabs and beams are designed by Safe program, and the results compared by Microsoft excel.
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    (The British University in Dubai (BUiD), 2022-01) ABDULJAWAD, NORAN AMER
    The structural engineers are always in a challenge between the responsibility for the people life and the development in the structural engineering sector, the long spans or the height of the buildings also the modern design that needs flexibility required from the structural engineer to discover new ideas and seek for a new solution to break the limitation of the traditionally used manufacturing processes of the concrete, and move to a new page which is a smart structure-based new technology, such as 3D concrete printing, that will help the structural engineer and the construction sector to be more creative. Taking under consideration that every complex structure gives complex loads and dynamic nature, in addition to that it will increase time and cost which is very critical points in the construction stage. The present paper reviews all the properties, features, advantages, and disadvantages of 3D printing will be discussed with approval. This dissertation or thesis is surveying research, the type of the survey is a questionnaire, it was done online by using SurveyMonkey or Google Forms, and the design of the question was developed and selected carefully which includes a critical point about 3D printing, the questions were distributed between engineers with different engineering background, like civil engineers, structural engineers, MSc. in structural engineering, PhD. in structural engineering, and researchers. And it was targeting engineers in different locations and in different fields. This survey research includes questions that are divided into different sections. The types of the questions are closed-ended questions and that means quantitative research which provides numerical data that can be statistically analyzed to find correlation, trends, patterns. On the other hand, the result of the responses is static analysis, usually using computer programs like SPSS, Stata, or Excel. Knowing that survey results are organized and discussed in the conclusion.
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    (The British University in Dubai (BUiD), 2022-10) KHAN, MOHAMMED FARAAZ
    Deterioration of concrete is a prominent occurrence that happens due to several factors surrounding a structure making the place inhabitable with a risk to life and property. These factors and the impact of deterioration depend upon the surrounding environmental conditions of the structure and vary for different geographical locations. The deterioration of concrete in a structure if assessed properly can be stopped from propagating further and economical solutions can be proposed to rehabilitate the structure. This dissertation aims to find the most prominent type of deterioration using different testing methods in semi-arid environmental conditions like the United Arab Emirates. It further aims to assess the data retrieved by statistical analysis to find its effect on the structural elements, such as the slabs, column and beams. The statistical assessment of the data provides significant information about the deterioration and its effect on the structural elements. Furthermore, the dissertation progresses by investigating the effect of deterioration on the design forces by modelling a structure with the acquired data from the site and comparing it with a non-deteriorated structural model of the same. Analysing the design forces helps to assess the effect of deterioration on various structural elements. Moreover, the dissertation also portrays the effect of deterioration on the most effected structural element which are the columns and asses the loss in capacity due to deterioration. The assessment and the interpretation using statistical analysis and modelling of the structure along with design helps to understand the effect of deterioration on structural elements in semi-arid environmental conditions.
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    Comparison and Critique review of Durability Provisions and Design Requirements of Various International Design Codes and Standards.
    (The British University in Dubai (BUiD), 2022-09) AL-HADDAD, DIALA BASEM
    Codes and standards establish a standardized language and set of rules for building design, construction, and operation. Such codes and standards have long been the primary mechanism used by governments to establish agreed-upon norms within a territory. These codes are under continual development and update to respond to the outcomes of proven search and the ongoing evolvement of technology and construction processes. Building codes are primarily concerned with establishing a framework for structural capacity and serviceability; nevertheless, many do not effectively consider durability design. In the absence of clear standard guidelines for design engineers, insufficient design and failures or an expensive over-design to provide for the worst-case scenario may occur. Failures in durability design endanger public safety and put a strain on the government's budget. The ACI 318 code is the most widely used code for the design of new concrete structures. Adapting this code will result in a cost-effective concrete structure that is sufficient to withstand the applied loads, however, the provisions about durability are not well understood or thoroughly documented. The goal of this study is to compare the development of the ACI 318 durability design approach to international codes and to suggest improvements to the provisions in light of this comparison. The proposed upgrade may be a beneficial start for the ACI code committee to begin updating the following ACI code generation. The study revealed that the provisions of the ACI 318 code are not comprehensive and well documented, the requirements are prescriptive and dispersed throughout the code chapters, the terminology lacks crucial terms related to durability, and that complex structures and a highly aggressive environment are not included. On the other hand, in the European code and British standards, provisions are more detailed, harmonized, and comprehensive. Additionally, the investigation uncovered inconsistencies in the way ACI publications provided durability criteria for corrosion caused by chlorides, resistance to freezing and thawing, and chemical sulphate attack. Inadequate durability design and implementation can lead to structural failures; as a result, design codes need to be improved to enable code practitioners a coherent, understandable foundation for creating designs that can withstand the environment for their specified service lives.
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    Numerical Evaluation of Pre-Damaged Beam Using Recycled Concrete Aggregate Strengthened by FRP Sheets
    (The British University in Dubai (BUiD), 2022-09) MOHAMMED, MOHAMMED ASHRAF MOUSTAFA
    Fiber reinforced polymer (FRP) has been increasingly used nowadays as an effective rehabilitation method in buildings due to structural flaws and aging of building structures, therefore it is an effective method to repair beams, columns, slabs. The research is conducting numerical evaluation to know the behavior of recycled reinforced concrete (RCA) beam samples, in addition to normal weigh aggregate (NWA) beam as control sample with no shear reinforcement, when strengthened by carbon fiber reinforced polymer (CFRP). The purpose of having this kind of research is trying to predict the effect of strengthening RCA reinforced beam samples with CFRP without shear reinforcement on deflection and damage mode types (Shear- Moment). As a result, four numerical models will be investigated, two models of RCA and two models as NWA (Control Samples) beams un-strengthened and strengthened with CFRP-U wrapping. The behaviour of strengthening the reinforced concrete beam with RCA without shear reinforcement, has been studied using three main parameters. The first parameter is type of loading, loads ranges from 81.7-130.9 KN for static and dynamic load. The second parameter is type of FRP carbon fiber, which has been used “Master Brace FIB 600/50 CFS” types. The third parameter is the concrete strength with different strengths varies from 64.5-77.00 MPa. All parameters mentioned above have been considered carefully in the numerical analysis of FRP strengthened the RCA beam samples. The (RCA) beam type has been modelled in two models, one with 0.75% (5D) steel fibers in self consolidating concrete matrix (SCC) and the other without it, but both models using with 100 % coarse recycled aggregate (RCA), while (NWA) beam types has been modelled without steel fibers with compressive strength 70.50 MPa and loads ranges from 120.1-130.1 KN. The advantages of using SCC and steel fibers are to enhance shear capacity by achieving the best performance of structure integrity. Moreover, ductility and post-cracking of RCA beam will be improved. The analytical model cross section of the beam is 200mm depth, 150mm width and 1600mm length with three 12mm bars diameters as bottom reinforcement and for more additional checking, it has been added two 12mm as top reinforcement for the cross section, all rebars having length of 1540mm. On other hand, the longitudinal percentage of reinforcement ρ(As/bd)=1.4% , which has been selected to warranty the shear failure. In other words, along beam no shear steel rebars has been used; although, three closed stirrups rebars with 10mm diameter used at locations along 300mm distances from supports to prevent the concertation of stress and to be steel rebars hangers as well. The research demonstrates the load path with distribution of stress/strain and defection through both models under different values and types of loads using FE software which represents in (ANSYS Workbench). The results illustrate that the 3D modelling shows some differences in deflection values between RCA by and NWA samples when strengthened or strengthened by CFRP laminates and when used compression rebars as well, while no differences have been found in shear loads values under different types of experimental loadings. In addition, 3D-FE model (ANSYS Workbench) illustrates type and location of failure which confirms that where retrofitting is needed. The normal numerical analysis and strengthening calculations has been done as per ACI 318-19& ACI 440-17 standards by using (MIDAS Gen and MIDAS design plus) and compared to experimental results. All in all, numerical evaluations using FE software illustrated good prediction of stress, load path and failures specially shear failure of recycled concrete aggregate reinforced beam strengthened by external bonded CFRP laminates, in addition to identical strengthening calculations as per ACI 318-19 and ACI 440-17R.
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    Effect of location of thickened concrete slabs and type of material on the seismic behavior of structure buildings
    (The British University in Dubai (BUiD), 2021-11) EL-FEQY, KHALED HAMED ABD ELHADY
    The design against lateral force (wind load and seismic load) is mandatory for high rise buildings. There are many factors that should be considered while estimating the seismic force that shall be applied to a building as well as certain checks to ensure building safety against that seismic force. Many structural engineers attempt to keep the seismic drift within the allowable value given by code of practice. The common problem is the seismic drift exceed the allowable values. Different solution is used to overcome this issue such as increasing in shear wall size, use larger size of beams, use thickened slab, use bracing, use advanced mass damper etc.. Practically, the idea of use thickened slab appears to author while design building with transfer slab. The more thickened transfer slab, the less seismic drift is obtained. This idea may not studied before from this point of view. Thus, this research focuses on the estimation of seismic behavior of concrete structures by performing many structure models with different heights at moderate seismic zones. The seismic force in this research is based on UBC97 code of practice. All the structural models have been analyzed and compared in similar circumstances. The research also attempts to find a practical solution which doesn’t need advanced technology by increasing the slab thickness in certain floors to reduce the seismic drift. The increase in slab thickness causes a complete change in all structural analysis results of a building (the total displacement and the total base shear). This research covers the results of increasing the slab thicknesses to obtain a good comparison between all models. Results show that the thickened slabs is good solution for seismic drift. The thickened slab should be located at certain floors to get the optimum reduction in seismic drift as well as the seismic drift shape of the structure. On the other hand, another approach using Ultra High Performance Concrete (UHPC) is used in certain floors without changing the slab thicknesses to observe the effect of using UHPC on the seismic behavior of structural building. Results of second approach show using of UHPC has a minor effect on the seismic behavior compared to results using the thickened slabs.
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    Advanced Composites as Reinforcement for Concrete
    (The British University in Dubai (BUiD), 2021-05) Alsamaraie, Ibrahim
    Recently, the demand for building concrete structures reinforced with steel rebars is gradually increasing worldwide. The serviceability of these reinforced concrete structures is affected by multiple factors, one of which is exposure to extreme weather conditions. Deterioration of steel rebars is one of the most common issues caused by the harsh environment's weather. The degradation of concrete structure is mainly driven by steel corrosion. Fiber-reinforced polymer (FRP) rebar is considered an innovative and durable choice rather than conventional steel reinforcement for concrete structures. GFRP bars were classified as an excellent corrosion resistance compared to conventional steel due to their mechanical performance. Several researchers have performed numerous studies out to explore the flexural response of GFRP bars. As a result, it is crucial to establish effective FE models that can be employed to comprehend the essential structural behavior of such systems and the performance under applied loads. The flexural behavior of structural reinforced concrete beam components was presented in this study utilizing 3D ANSYS 21 FEA simulation. This study compares an FE model with experimental findings from previous works and the ACI 440.1 model. Graphical representations were discussed, including the deflection of the mid-span stress-strain relationship. The specimens are rectangular beams that are simply supported and have spans and clear spans of 2.4 m and 2.1 m. A four-point pseudo-static experiment was performed on the samples. The findings indicate that fibre-reinforced composites can be evaluated using ANSYS software with an adjusted model. The difference between FEA model results, experimental tests, and ACI 440.1 theoretical formulas predicting failure loads is within a 10% margin of error. The results have demonstrated the ACI 440.1 code conservatism compared to the remainder of the results obtained from environmental findings or FE simulations.
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    Evaluation of Compressive Strength for Recycled Aggregate Concrete Reinforced with Polypropylene Fibers
    (The British University in Dubai (BUiD), 2021-05) Omar, Turk
    The compressive strength of recycled aggregate concrete reinforced with polypropylene fibers was investigated. The possibility of using polypropylene fibers (PPF) in the recycled aggregate concrete (RCA) was extensively studied. Moreover, the mixes experimented were using different RCA replacement ratios and different PPF content. The results present the compressive strength behavior of Recycled Aggregate Concrete (RAC) with and without addition of Polypropylene (PP) fibers. The normal coarse aggregate was replaced by recycle aggregate in the percentage of 0, 25, and 50%. The polypropylene fibers (PP) were used in the recycle aggregate concrete by 0.2% and 0.35% by volume. The values of compressive strength of the natural aggregates concrete (NAC) were set as a control. 27 concrete cubes (150x150x150mm) for each RAC and NAC were casted making a total of 54 concrete cubes. Three cubes for each designed mix were also cured for 7 days and 28 days. The test results revealed that the incorporation of PP fibers did not considerably change the compressive strength and the density of concrete, but the compressive strength of RAC was satisfactory at the early ages until the later ages where NAC was higher than RAC. Therefore, use of recycled aggregate concrete showed tolerable performance with respect to compressive strength and will have a better employment at fast setting concrete where early strength is required. Furthermore, more studies are necessary to determine the effect on durability and enhancement to the workability.
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    Study of Life Cycle Cost Analysis and Value Engineering and their use in UAE
    (The British University in Dubai (BUiD), 2021-06) AL SHELEH, ZEIN BASHAR
    When planning a project, the main stakeholders' concern is always about the potential for failures, defects, delays, overruns, and conflicts that the project might face. According to studies and statistics, most projects take around 20% longer than scheduled to complete and frequently go much over budget. There are several techniques to plan a project effectively, but they all need a thorough strategy, managing, supervision, and collaboration. Life cycle cost analysis and value engineering are some of the most recently used techniques that evaluate and analyse all costs related to the project over its service life and give the essential project functions at the lowest possible cost. This research calculates the life cycle cost of a residential building in Sharjah city, in UAE over 40 years life span. Including the three main phases: initial cost, operation & maintenance cost and decommissioning cost. And then the same calculation was done for 60 years of life span for the same project. in the end, a comparison between both cases is made to find out which case will be more financially beneficial. Results show that investing more money in the initial phase, mainly the construction phase, to improve the materials and construction quality would increase the service life by up to 20 years. which will result in more profit to the owners/stakeholders taking into consideration safety requirements.
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    Comparison of the Provisions of ACI318-19 Code and Eurocode on the Structural Design and Cost Analysis, of a High-rise Concrete Building Subjected to Seismic & Wind Forces
    (The British University in Dubai (BUiD), 2021-05) Oussadou, Samy Elhadi
    This work aims to compare two codes; ACI 318-19 and Eurocode in terms of lateral effect on high-rise building, focusing on the seismic and wind provisions, and since these two forces effect the structural elements geometry, thus the cost comparison was included, by comparing the amount of reinforcement used. Since both of the codes have different standards and factors, therefor it is expected that there will be some differences in the structural design. This research contain design and analyses of a high-rise building consisting of 50 storeys reinforced concrete structure and comparison of several provisions. This research study investigates the difference between seismic and wind results between the two codes and if there might be any differences in the structural elements reinforcement amount, which will affect the cost of the building.
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    Seismic strengthening of Reinforced Concrete Structures using External Lateral Post Tensioning
    (The British University in Dubai (BUiD), 2021-04) Murugesan, Usha
    The constructions of buildings before the 1970s where not in coherence with the seismic design or any type of seismic codes hence the buildings have to be investigated and do the necessary strengthening to withstand the seismic effect. Those vulnerabilities of structures which has added forth and raised cognizance for seismic Strengthening needs. Design codes now consist of seismic provisions, and those buildings which are constructed in the future are earthquake-resistant structures. Surveys after earthquakes have been analysed to interpret the collapsed structures to study and learn the possible failure causes and mechanisms. The most destructive natural hazards is earthquake. A seismic event may cause a huge loss of property as well as life. It is estimated that around 10000 people are killed every year due to calamity. This, in turn, results in a huge annual economic loss. Hence the construction industry takes critical steps to prevent and avoid the collapse as well as reduce damages caused to the structures. The method of externally applied post tensioning of tendons (EPT) is a powerful method of strengthening and repair of structure which are in existence. The technique of EPT can be used in all types of framing i.e.; to concrete buildings, structural steel buildings and wood structures. It’s a unique method of strengthening in which the strength of an existing structure is increased for its stability and also reduces the deflection in an existing structure which have been through an earthquake damage.
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    Horizontal Shear Strength at the Interface of the Concrete Beams Cast in Two Time Stages
    (The British University in Dubai (BUiD), 2020-12) Abushaaban, Hatem Ady
    Composite concrete is a method of construction that uses both precast and cast in situ concrete to produce a structural element. In framing big slabs areas, the use of precast slabs and beams is being an economical way of construction. The best procedure is to employ beams of inverted T section, which bottom flange will act as a ledge to seat the precast slab. Topping concrete slab is then cast on top of the precast slabs and beams. It is cleaner and safer than the full cast in place construction. This kind of construction which is cast in two stages at different times reduces the quantities of formworks at site and reduces the back propping which in some cases is required to be extended below to multiple levels according to the expected construction loading. Accordingly, more clear spaces for lower levels will be available so that other site activities can be accomplished to complete the job faster with less building materials and reduced risk levels. The bond strength between the precast concrete part and the cast in place part is essential to provide the monolithic behavior for the composite concrete members. The integrated monolithic behavior is achieved only if all forces including the horizontal shear are fully transferred at the interface. From the structural normal practice, the word “interface” means the plane between two different materials; such as concrete to steel or concrete to concrete that is cast in stages at different ages. This interface which is studied in this dissertation is that the plane between the precast and the cast in situ parts of the composite concrete beams. The rough surface of the precast beam part, aggregate interlock, concrete strength and the steel bars crossing the interface between the cast in place and precast parts are the main factors that affect the horizontal shear strength of the that interface. The international design codes propose semi empirical equations to determine the horizontal shear strength considering adhesion, friction caused by normal stress and friction caused by interface steel rebar clamping stress. Usually the experimental tests are done on series of specimens of small size and in some other cases, are done on small sized composite beams of short span that can be accommodated in a concrete testing facility. The small specimens testing somehow reduced the level of reliability of the results. Accordingly, there is a considerable difference in the proposed interface shear strength limits between the different structural design codes. This dissertation presents a study of four composite beams with different sections, properties and reinforcement that were experimented for shear friction in a previous research. The beams are modeled using a 3D finite element software. A shear friction design hand calculation is provided as well using the provisions and equations proposed by the code of practice. The dissertation provides a comparison between simplified code approach, 3D finite element model and results from the experimental work published by Anil Patnaik at 1992.
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    The behavior of Tapered High Strength Concrete Filled Steel Tube (CFST) Column connected to Encased Steel Reinforced Concrete Composite (SRC) Column
    (The British University in Dubai (BUiD), 2020-06) Abdelhamid Azzazy, Yasser
    The use of Convectional Concrete Column is often limited in high-rise Buildings due to the constraint from the architects on increasing size of the columns, so the composite columns provide appropriate solution to satisfy the architect and the Client with smaller column size. Nowadays, Composite Columns have been widely developed in the construction of the high-rise buildings, long span structures, and bridges. Composite columns have two main types, encased composite columns (SRC) and concrete filled steel tube columns (CFST). This research is focusing on the behavior of a tapered concrete filled steel tube column (CFST) connected to encased composite column (SRC). The purpose of having two different sections along the column height is to enhance the flexure resistance of the column at the top edge by introducing CFST element, while the lower part is modeled as SRC element and it is mainly subjected to axial compression with significant reduction in bending moments compared to the top part of the column. The behavior of the tapered CFST column connected to SRC column has been studied using two main different parameters. The first parameter is the type of loading, such as pure axial compression, axial compression and uni-axial bending, and axial compression and bi-axial bending. The second parameter is the concrete strength, with different concrete strengths ranging from C40MPa to C70MPa. Both parameters have been carefully considered in the analysis of the composite column. The steel section used in the research design model has a yield strength of 355MPa. The steel reinforcement used in the model has a yield strength of 500MPa. The column has been modeled using 3D-Fiber (Solid) Finite Element Method. The cross sectional of the columns has been divided into tiny fiber (solid) elements. The advantage of using a fiber (solid) element is easy to assign the tiny element as concrete or steel, even stiffeners plates have been modeled by adopting the fiber element methodology. The maximum size of the fiber (solid) element is (10mm x 10mm) which warrant more accurate results in terms of stress and strain. The vertical rebar was ignored from the 3D Fiber Model. The stresses and strains extracted from the 3D-FE models have been compared to the simplified formulas adopted by EUROCODE-4 and American Standards AISC / ANCI . The research illustrates the load path and stress / strain distribution through different structural elements connected to each other under deferent type of loading. The results demonstrate that the 3D-FEM displays some differences in the composite section capacity under different type of loading compared to the simplified formula adopted by Eurocode and AISC/ANCI. The stress and strain distribution demonstrate a smooth transition between CFST element and SRC element with local stress concertation on the concrete and steel at the interface between CFST element and SRC element. The concentration in the stresses is not considered in the simplified formula by the standards codes, so it should be carefully considered in the section capacity.
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    Structural use of composite materials
    (The British University in Dubai (BUiD), 2020-10) Alansari, Ali
    The construction world is changing daily. Research on new materials that can be used to replace traditional ones has been aggressive. The fibre-reinforced polymer is one of the new technologies that has been adopted in the market. Fibre-reinforced polymers are composed of more than two materials bonded together. FRPs have widely been used in the industry, such as bridge construction, counterparts, buildings construction and among other vital uses. FRP materials have superior properties that make them more pronounced in the field of construction. Some of the known advantages that make these materials quite important include strong bonding. The most important advantage of fibre composite material is the fact that they have high strength properties. There are various types of FRP materials; the type variety is dependent on the arrangement of the fibres. The direction of bonding includes multidirectional, bidirectional, random mat, and woven type. The most important one is the multidirectional one that offers high strength. This research aims to conduct extensive research on the application and the usage of FRP material in the construction industry. Among the methods that have been exploited in this study include pultrusion, which is the most popular process used in the industry. The materials used in the manufacturing process include reinforcing fibres and fibre fabrics. Fibre composite materials have several advantages and disadvantages. However, the advantages are the most exploited part, which is why they have been adopted in the industry. Various case studies have been explored in the research to verify how much the FRP has been used globally. One of the cases is the use of GFRP in Netherlands. The case study that has been considered in this research is the 22 m bridge that was constructed in Bronlibelle. The bridge was built using GRPR, and various standards were used in the design process. The measures that were used for this case include CUR96, EN991, and EN990. Among the details that have been discussed in this study is the contractor and the challenges they met while constructing the bridge. Other composite materials such as Carbon Fibre Reinforced Polymers (CFRP) have been discussed in detail. The details given light in this study include composition, uses, and advantages that these materials can have compared to others used in the construction industry. The research has established that most of the advantages and disadvantages are the same for fibre material. The research used secondary sources of data that have already been done elsewhere to develop the final judgment. The research shall use case studies that have already been done. To use the material for construction, it is essential to consider the economic part of it. In this study, the economy involved when using this material has been discussed. This research established that the FRP materials are among the best since they are economical. The research demonstrated that carbon fibre cost is lower as long as production is high. Among the costs that have so far been discussed in this study include material cost, process material cost, the energy needed for the production process, labor cost, capital, and other costs. Therefore, the research shall help the reader with alternative construction materials.
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    The Influence of the Alkaline Activator on the Life Cycle Assessment of Alkaline Activated Natural Pozzolan Geopolymers Concrete
    (The British University in Dubai (BUiD), 2020-07) Kamil, Marwah
    This paper studies the effectiveness of replacing cement in concrete with natural pozzolan, originated from Saudi Arabia, on the reduction of the harmful gasses, carbon dioxide equivalent gases, during the production process of the concrete. Life cycle assessment is done on the alkaline activated natural pozzolan geopolymer concrete, global warming potential of 100 years GWP100 category. The life cycle assessment exercise was also done on alkaline activated natural pozzolan geopolymers where the natural pozzolan was activated with different types of alkaline activator to reduce the GWP100 of the geopolymer concrete even further. The results of the study showed that the geopolymer with natural pozzolan activated by sodium hydroxide and sodium silicate have the lowest GWP100 of 106 kg.𝐶𝑂􀬶.eq, which is lower than that of the PC concrete by 72%. Also, it is found that the alkaline activator is responsible for the largest amount of the carbon dioxide equivalent gases produced during the production of 1 𝑚􀬷 of the geopolymer concrete. Two further life cycle assessment exercises were done to replace the sodium silicate alkaline activator with sodium hydroxide and silica extracted from rice husk ash. The results of the life cycle assessment, GWP100 category, showed that both geopolymer concretes have higher GWP100 than that of the natural pozzolan activated with sodium hydroxide and sodium silicate. The GWP100 of the natural pozzolan alkaline activated by sodium hydroxide geopolymer and natural pozzolan activated by sodium hydroxide and silica extracted from rice husk ash are 114 kg.𝐶𝑂􀬶.eq and 197 kg.𝐶𝑂􀬶.eq respectively. However, all of the alkaline activated natural pozzolan geopolymer concrete showed GWP100 less than that of the PC concrete by at least 48%. The results of the life assessment exercise are then compared to life cycle assessment exercises done by other researchers on alkaline activated natural pozzolan geopolymer concrete as well as other types of geopolymer concretes. The recommendations of this study is that further research needs to be conducted to study the properties of the alkaline activated natural pozzolan geopolymer concrete and further life cycle assessments need to be conducted on different mix design option on both raw and calcinated natural pozzolan to encourage the consultants and contractors to replace cement with more sustainable and durable material like the natural pozzolan.