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Masonry infilled reinforced concrete frames retrofitted with vertical post-tensioned bars
(Universiti Teknologi Malaysia, 2016) Soltanzadeh, Gholamreza
Reinforced concrete (RC) frames filled with clay brick walls are among structures that have been damaged in many past earthquakes. The main aim of this study is to propose a new retrofit method, which can increase lateral strength, stiffness, energy dissipation capacity and ductility of infilled RC frames. To achieve this aim, at first seismic behaviour of several bare and infill RC frames were studied through experimental and numerical studies. Then the proposed retrofit method which was based on external post-tensioning of infilled frames by vertical bars was developed. Finally, the effectiveness of the proposed retrofit method was evaluated through experimental test. In the test, a total eight RC frames with two different aspect ratios of 0.5 and 1.0 were constructed with the scale of 1:3. Experimental test was performed using a quasi-static cyclic loading. For all experimental test, the values of initial lateral stiffness, effective stiffness and ultimate lateral strength were determined. The ductility and energy dissipation capacity were calculated using hysteresis curve obtained from cyclic loading. Results indicated that the presence of brick walls reduced the ductility of bare frames. Ductility of bare and infill frames are dependent on the aspect ratios. Bare frames with the higher aspect ratio has 70% higher ductility compared to that of lower aspect ratio. Failure mode of frames was also dependent on the aspect ratio. The presence of brick walls increased three and half times the energy dissipation capacity of the frame with higher aspect ratio. The proposed posttensioning method increased ultimate lateral strength and ductility of infilled frames two and five times, respectively. Increase in the ultimate lateral strength of infilled frames was dependent on their aspect ratio. Increase in the ultimate lateral strength of the frame with lowest aspect ratio was three times more than that of highest aspect ratio. Similarly, the ductility of retrofitted frame with the higher aspect ratio was 45% more than that of lower aspect ratio. The post-tensioning method increased the energy dissipation capacity of retrofitted frames. The retrofitted frame with higher aspect ratio dissipated 10% more energy compared to the frame with lower aspect ratio. The proposed retrofit method using post tensioning improved ductility, energy dissipation capacity and ultimate lateral strength of infill frames with opening. However compared to fully infill frames without opening, the rate of improvements was slightly lower. In general, results of experimental and numerical studies in this research showed that post-tensioning can improve stiffness, ductility, ultimate lateral strength and energy dissipations capacity behaviour of infilled RC frame.
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Meshfree formulations of kinematic wave for channel flow routing
(Universiti Teknologi Malaysia, 2016) Hirol, Halinawati
This study concerns the development of various Meshfree formulations, namely Point Interpolation Method (PIM), Radial Point Interpolation Method (RPIM) and Element Free Galerkin (EFG) in solving numerically, St Venant’s kinematic wave equations for the hydrologic modeling of surface runoff and channel flow. It involves problem formulations derivation of governing equations, provision of the corresponding solutions by generating Matlab source codes, verification of results against established data, parametric study and assessment of performance of the newly derived Meshfree formulations against established numerical methods, namely Finite Element Method (FEM) and Finite Difference Method (FDM). The originality and the main contribution of the study are solving the Meshfree formulations of the kinematic wave equations numerically. The formulations are verified when it is found that the results produced by the source codes are in general in close agreement with the benchmark data. Although slight discrepancies have been observed in some cases, these are later validated as due to several factors, namely shape parameters values which are yet to be optimized, different number of nodes used for comparison and manual discretization of input data. In obtaining the best performance of the methods, optimum values of the shape parameters have been determined through a parametric study which once obtained are used in the performance assessment. RPIM and PIM are found to be less sensitive to the optimum values as compared to EFG. Two types of performance are assessed; the convergence rate and the computer resource consumption in terms of CPU time. Based on this study, it can be concluded that, in general, Meshfree methods perform comparably with the established methods in terms of convergence rate despite the fact it does not need the construction of mesh which can save modelling time. This shows the potential of Meshfree as numerical methods for its future development.
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Durability performance of ternary blend alkali activated mortars for concrete surface damage repair
(Universiti Teknologi Malaysia, 2017) Huseien, Ghasan Fahim
The progressive deterioration of concrete surface structures being the major concern in construction engineering requires special protection and precise repairing. The adverse physical, chemical, thermal and biological processes that cause such rapid decay need to be overcome. The durability of concrete structure is found to be strongly influenced by inappropriate use of materials as well as their physical and chemical condition of the surroundings. The immediate consequence is the anticipated need of maintenance and execution of repairs. Lately, many alkalis activated mortars are synthesized by selectively combining some waste materials containing alumina and silica compounds which are further activated via strong alkaline solution. Despite the emergence of various alkalis activated as prospective material toward emergency repairs and coating, a functional alkali activated with efficient repairing attributes and endurance is far from being achieved. Generally, the alkaline solution prepared by mixing concentrated sodium silicate and sodium hydroxide restrict the broad array of repairing applications of alkalis activated mortar. Furthermore, they are not only expensive and hazardous to the workers but negatively impact the environment. The research attempted to produce environmental friendly alkali activated by blending different ratios of sodium hydroxide and sodium silicate at low concentration. Durability and mechanical strength of the synthesized ternary blend alkalis activated mortars were evaluated to inspect their repairing effectiveness towards concrete surface damage. Tests were performed for determining the porosity, shrinkage, compressive strength and slant bond shear strength. Microstructures and thermal properties were evaluated using XRD, SEM, TGA, DTG and FTIR measurements. The prepared ternary blend contained the ground blast furnace slag, fly ash and palm oil fuel ash or ceramic waste powder. The prepared fresh, hardened and durable mortars were activated with affable alkaline solution (at low concentration) of sodium hydroxide and sodium silicate. The ground blast furnace slag that acted as the main resource of Ca++ was used to replace the low amount of Na+ in the geopolymerization process. The amount of slag in the blend varied in the range of 20 - 70%. The addition of slag to the blend had improved the strength and durability properties as well the microstructure characteristics. This improvement is majorly attributed to the participation of calcium silicate hydrate and calcium aluminosilicate hydrate beside sodium aluminosilicate hydrate bonds in reaction products. The results revealed that all the prepared mixes developed appreciable strength under mild alkaline solution. Furthermore, the alkali activated specimens prepared with high slag content displayed good durability including abrasion, thawing-freezing and shrinkage. The research has established that the ternary blend alkalis activated mortars with friendly alkaline solution contributes towards the development of high strength and durable repairing materials for concrete structures.
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A hybrid multi-criteria decision making method for risk assessment of public-private partnership projects
(Universiti Teknologi Malaysia, 2016) Sarvari, Hadi
As governments embark on Public Private Partnership (PPP) projects to develop their infrastructure, effective risk assessment has become an important step to ensure success of these projects. However, there are many unsuccessful stories of PPP projects that have been reported all around the world. Thus, it is essential for both public and private sectors to apply efficient risk assessment approaches to allocate and manage risks more effectively. Literature review revealed a continuous endeavor for better PPP project risk modelling and assessment. Various techniques have been developed for use in the management of risks in construction. However, these techniques are limited to addressing risks relating to only cost, schedule, or technical performance individually or at best a combination of cost and schedule risks. Previous work so far is lacking a comprehensive model capable of handling impact of risks on all project objectives simultaneously; namely cost, time and quality. Thus, the main objective of this study is to develop a hybrid risk assessment method that capable of capturing impact of risks on the three project objectives comprehensively. To achieve this aim, this research explores the risk assessment approaches and proposes a hybrid alternative method based on the Fuzzy Analytic Network Process (FANP) and Multiple Objective Particle Swarm Optimization (MOPSO). The Fuzzy logic was used to convert linguistic principles into systematic quantitative-based analysis. Also, in order to consider the dependency and feedback between risks and criteria, ANP method is applied as a Multi-Criteria Decision Making (MCDM) method. Then, MOPSO, as a MCDM method, was used to assess the risks based on the project objectives. Objective functions have been developed to minimize the total time and cost of the project and maximize the quality. The research approach was a mixed-method approach and the field work included a series of questionnaires and interviews. It started with semi-structured interviews with PPP professionals. A mail survey was administered and more than 114 questionnaires were sent to construction and PPP professionals based in Malaysia. Out of 114, 88 valid responses have been received. An on-line survey was carried out as well in order to enrich the findings of the mail survey. The proposed hybrid approach was used to assess the collected data. A total of 30 significant risks were identified and evaluated. According to the results, it was found that “construction completion”, “construction cost overrun” and “interest rate volatility” are the highest ranks associated with the Malaysian PPP projects risks. Finally, the viability of the proposed hybrid approach was investigated through conducting semi-structured interviews with PPP professionals from construction and administration sector. It is concluded that the proposed hybrid MCDM method for risk assessment is a viable alternative to the existing practice. This may help bridging the gap between theory and practice of risk assessment in construction projects. It also can be applied through the public and private sectors to improve risk assessment and management. The research findings recommend further exploration of the potential applications of hybrid MCDM methods in construction management domain.
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The development of green construction site index
(Universiti Teknologi Malaysia, 2016) Firmawan, Ferry
The development of construction industry in Indonesia has been substantially contributing to the enhancement of social and economy of the country. However, its expansion may also give negative effects to the environment if the practices of implementing the construction project neglected the rules and regulations of sustainable construction concept. The aim of this study is to develop Green Construction Site Index (GCSI) with the consideration of assessing the staff commitment level on the implementation of the sustainable construction practices. Therefore, Project Organizational Commitment Index (POCI) is also developed. Data were collected by on site direct observation, distribution of questionnaire and interview with key personnel and project documentation review. All the data were tabulated and analyzed by using descriptive elaboration method. The development of GCSI and POCI was based on the opinion and validation of selective experts in the importance of sustainable elements in construction by using Average Index Analysis. Evaluations of GCSI and POCI have been conducted toward ten selected construction projects in Indonesia. The findings have revealed that the overall GCSI value of all ten construction projects was 3.39 which indicated that level of sustainability was in a good category. Meanwhile, the POCI value of all the projects was 3.31 showing that the commitment level of staffs in implementing the sustainable construction project practices was also in a good category. The result shows and proves that the establishment of GCSI and POCI were able to be used to assess level of sustainability construction project in the perspective of project progress and level of staff commitment. It shows that the capability of GCSI and POCI in assessing level of sustainability construction project, based on sustainability concept of construction project. In conclusions, GCSI and POCI are beneficial and suitable to be used in measuring level of sustainability in construction project by respective construction stakeholders like government bodies, local authorities and contractor.