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Neupane Kamal - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Structural Behaviour of Geopolymer Prestressed Concrete Beam
2020Co-Authors: Neupane KamalAbstract:includes published articlesProduction of ordinary Portland cement (OPC) is a carbon-intensive process that generates significant amounts of carbon dioxide (CO2) gas from the combustion of fossil fuels and thermal decomposition of limestone. Overall, cement industries are responsible for around 7% of global CO2 emissions which poses a considerable threat to global climate change because of its greenhouse effects. Geopolymer is an inorganic polymer material having similar binding properties to OPC which can be produced from aluminosilicate compounds, such as fly ash when activated by alkaline solution. The recent advent of geopolymer technology shows great potential to reduce carbon footprints by utilising industrial by-products, such as fly ash and ground granulated blast furnace slag (GGBS), and convert into effective binding material. The setting and hardening process of geopolymer binder is different from hydration of OPC, called “geopolymerisation” which is the condensation process of aluminate and silicate monomers to form a polymer chain. Generally, fly ash-based geopolymer Concrete attains relatively lower early-age strength at ambient temperature due to the slow rate of reaction. However, geopolymer Concrete based on GGBS or a combination of fly ash and GGBS can set and harden in ambient temperature with comparable early age strength to OPC Concrete of same grade. In the recent past, several studies were carried out to investigate mechanical, serviceability, durability and microstructural properties of geopolymer Concrete using different aluminosilicate materials. However, limited research has been carried out on applications of geopolymer binder in structural Concrete, such as reinforced Concrete beam, column and Prestressed Concrete beam. Prestressed Concrete is a construction technique in which flexural tensile stress generated in the Concrete member due to imposed load is counteracted by applying an initial prestressing compressive force. The use of Prestressed Concrete Structures has been increasing in modern construction practices because they can withstand significantly higher flexural load with minimal deflection and cracks than conventional reinforced Concrete (RC) members of similar cross-section. Generally, tensile strength of Concrete is ignored in the design of conventional RC Structures. However, tensile or flexural strengths of Concrete are significant in the design of Prestressed Concrete Structures where tensile strength of Concrete limits the maximum permissible prestressing load according to ACI 318. Application of higher prestressing load can increase the load-carrying capacity of Prestressed Concrete Structures and minimize their deflection under service load. Previous results showed that geopolymer Concrete possesses higher indirect-tensile and flexural strength than OPC Concrete for the same compressive strength. In addition, time-dependent losses of prestressing stress are the major serviceability problems of Prestressed Concrete Structure which reduce the load-carrying capacity of Structures and increase the deflection under service loads. The time-dependent losses of prestressing stress are directly proportional to the amount of shrinkage and creep strains of Concrete. Having smaller drying shrinkage and creep strains, geopolymer Concrete can result in better serviceability than OPC Concrete in Prestressed Concrete Structures. Thus, this study investigates the application of geopolymer Concrete in the Prestressed Concrete beam which may be a worthwhile utilization of geopolymer Concrete in Concrete Structures. Despite having higher mechanical strengths and durability properties than conventional OPC Concrete, geopolymer Concrete has not been widely used in structural grade Concrete, so far. The safety hazards in mixing and handling of Concrete due to the use of liquid sodium hydroxide in geopolymer binder is one of the barriers to the adaptation of geopolymer in Concrete industry. In this study, the mechanical and serviceability properties of grade 50 MPa geopolymer Concrete from sodium hydroxide-free one-part geopolymer binder are investigated under ambient temperature curing and compared against same grade OPC Concrete. Development of strengths at an early age under accelerated curing is investigated to study the suitability of geopolymer Concrete in precast Prestressed Concrete Structures. Finite element models of Prestressed Concrete beams of three different lengths and sizes are analysed to investigate their load-deflection behaviours under imposed load for short-term and long-term durations using the Abaqus program. The effects of tensile strength of Concrete in load-deflection behaviours of Prestressed Concrete beams are studied by comparing the results between identical geopolymer and OPC Prestressed Concrete beams. This study finds that geopolymer Concrete has around 27% higher indirect-tensile and flexural strengths than OPC Concrete of same strength grade which contributes to geopolymer Prestressed Concrete beams to withstand around 20% higher first-crack load than OPC Concrete beams of same span. In addition, geopolymer Prestressed Concrete beams show a relatively smaller loss in prestressing stress which results in a smaller loss in flexural capacity of beams over the service life of the Structure
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Investigation of Structural Behaviour of Geopolymer Prestressed Concrete Beam
Faculty of Engineering School of Civil Engineering, 2020Co-Authors: Neupane KamalAbstract:Production of ordinary Portland cement (OPC) is a carbon-intensive process that generates significant amounts of carbon dioxide (CO2) gas from the combustion of fossil fuels and thermal decomposition of limestone. Overall, cement industries are responsible for around 7% of global CO2 emissions which poses a considerable threat to global climate change because of its greenhouse effects. Geopolymer is an inorganic polymer material having similar binding properties to OPC which can be produced from aluminosilicate compounds, such as fly ash when activated by alkaline solution. The recent advent of geopolymer technology shows great potential to reduce carbon footprints by utilising industrial by-products, such as fly ash and ground granulated blast furnace slag (GGBS), and convert into effective binding material. The setting and hardening process of geopolymer binder is different from hydration of OPC, called “geopolymerisation” which is the condensation process of aluminate and silicate monomers to form a polymer chain. Generally, fly ash-based geopolymer Concrete attains relatively lower early-age strength at ambient temperature due to the slow rate of reaction. However, geopolymer Concrete based on GGBS or a combination of fly ash and GGBS can set and harden in ambient temperature with comparable early age strength to OPC Concrete of same grade. In the recent past, several studies were carried out to investigate mechanical, serviceability, durability and microstructural properties of geopolymer Concrete using different aluminosilicate materials. However, limited research has been carried out on applications of geopolymer binder in structural Concrete, such as reinforced Concrete beam, column and Prestressed Concrete beam. Prestressed Concrete is a construction technique in which flexural tensile stress generated in the Concrete member due to imposed load is counteracted by applying an initial prestressing compressive force. The use of Prestressed Concrete Structures has been increasing in modern construction practices because they can withstand significantly higher flexural load with minimal deflection and cracks than conventional reinforced Concrete (RC) members of similar cross-section. Generally, tensile strength of Concrete is ignored in the design of conventional RC Structures. However, tensile or flexural strengths of Concrete are significant in the design of Prestressed Concrete Structures where tensile strength of Concrete limits the maximum permissible prestressing load according to ACI 318. Application of higher prestressing load can increase the load-carrying capacity of Prestressed Concrete Structures and minimize their deflection under service load. Previous results showed that geopolymer Concrete possesses higher indirect-tensile and flexural strength than OPC Concrete for the same compressive strength. In addition, time-dependent losses of prestressing stress are the major serviceability problems of Prestressed Concrete Structure which reduce the load-carrying capacity of Structures and increase the deflection under service loads. The time-dependent losses of prestressing stress are directly proportional to the amount of shrinkage and creep strains of Concrete. Having smaller drying shrinkage and creep strains, geopolymer Concrete can result in better serviceability than OPC Concrete in Prestressed Concrete Structures. Thus, this study investigates the application of geopolymer Concrete in the Prestressed Concrete beam which may be a worthwhile utilization of geopolymer Concrete in Concrete Structures. Despite having higher mechanical strengths and durability properties than conventional OPC Concrete, geopolymer Concrete has not been widely used in structural grade Concrete, so far. The safety hazards in mixing and handling of Concrete due to the use of liquid sodium hydroxide in geopolymer binder is one of the barriers to the adaptation of geopolymer in Concrete industry. In this study, the mechanical and serviceability properties of grade 50 MPa geopolymer Concrete from sodium hydroxide-free one-part geopolymer binder are investigated under ambient temperature curing and compared against same grade OPC Concrete. Development of strengths at an early age under accelerated curing is investigated to study the suitability of geopolymer Concrete in precast Prestressed Concrete Structures. Finite element models of Prestressed Concrete beams of three different lengths and sizes are analysed to investigate their load-deflection behaviours under imposed load for short-term and long-term durations using the Abaqus program. The effects of tensile strength of Concrete in load-deflection behaviours of Prestressed Concrete beams are studied by comparing the results between identical geopolymer and OPC Prestressed Concrete beams. This study finds that geopolymer Concrete has around 27% higher indirect-tensile and flexural strengths than OPC Concrete of same strength grade which contributes to geopolymer Prestressed Concrete beams to withstand around 20% higher first-crack load than OPC Concrete beams of same span. In addition, geopolymer Prestressed Concrete beams show a relatively smaller loss in prestressing stress which results in a smaller loss in flexural capacity of beams over the service life of the Structure
Bagnaresi Silvia - One of the best experts on this subject based on the ideXlab platform.
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Fire safety verifications of a Prestressed Concrete Structure: natural fire vs ISO 834 curve
Alma Mater Studiorum - Università di Bologna, 2020Co-Authors: Bagnaresi SilviaAbstract:During years, the codes that regulate verifications against fire change a lot. They allow the use of engineering methods to approach problems by using Fire Safety Engineering. This thesis keeps in consideration the most recent fire prevention code (DM 16/10/2018) and highlights the difference between a compliant and an alternative solution for fire verification with a performance level III of a Prestressed Concrete warehouse with an ESFR shutdown system. To do it, has been done a comparison between the ISO 845 curve and a natural fire curve. For the natural fire case has been considered all the factors that influence the propagation or mitigation of the fire scenario (e.g. materials, fire load, ESFR system, type of activity and so on). Once do that, two FDS® simulations has been performed. The first one detects the ESFR time activation and the second has the aim to know time-temperature curves on load bearing elements through the implementation of the assumed final natural fire curve. Then, the behavior of the precast and Prestressed Concrete Structure has been investigated, both with the ISO curve and the natural fire curve. In order to apply time-temperature curves in cross sections, some SAFIR® simulations has been done on the principal structural elements with both the fire curves. On the thinner cross section has been done also some hand-made verifications (from EC 1992-1-2). Then 2D and 3D mechanical analysis has been performed with SAFIR® considering the previous thermal mappings. The case analyzed with the ISO curve present wide displacements and the collapse of secondary beams, instead the case analyzed with the natural fire curve meets the requirements
Xiu Yan Fu - One of the best experts on this subject based on the ideXlab platform.
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formula of unbonded tendon stress increment based performance
Applied Mechanics and Materials, 2014Co-Authors: Yuan Yuan Yu, Xiu Yan FuAbstract:Unbonded tendon stress calculation of unbonded precast Concrete Structure is defferent from Prestressed Concrete Structure, as tendon strain caused by the external load is not in accordance with relevant sections of the Concrete strain obtained. As the deformation of unbonded tendons are not subject to the deformation of plane-section assumption, therefore, arise due to external loads of unbonded tendon stress calculation is more complex. In this paper, based on theoretical analysis and derivation, the pre-stress deformation of the unbonded steel stress formula was given, this can provide more scientific basis for the stress Analysis of unbonded precast frame Structure.
Febyanti Rizka - One of the best experts on this subject based on the ideXlab platform.
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Desain Ulang Jembatan Thp Kenjeran Surabaya Dengan Menggunakan Balok I Girder Bentang 40m
2016Co-Authors: Febyanti RizkaAbstract:Jembatan Taman Hiburan Pantai Kenjeran atau yang lebih dikenal dengan Jembatan THP Kenjeran dibangun pada jalur lintas jalan Tambak Deres sampai dengan jalan Sukolilo Kenjeran, Kota Surabaya. Jembatan THP Kenjeran yang dibangun di pinggir pantai dan sekaligus menjadi tempat wisata karena dilengkapi dengan anjungan dan air mancur. Kondisi existing jembatan saat ini yaitu terdiri dari struktur beton prategang bentang 30 m dan struktur slab on pile bentang 6 m dan 8,5 m. Jembatan THP Kenjeran direncanakan menggunakan beton prategang I-Girder dengan bentang 40 m, type struktur slab on pile bentang 6 m. Struktur utama dari Jembatan THP Kenjeran berupa balok prategang I (PCI), dengan metode post tension dan mutu beton K-800. Untuk plat lantai menggunakan konstruksi beton bertulang dengan metode cast insitu sehingga terjadi aksi komposit antara balok precast dan plat cor. dan untuk pilar juga direncanakan menggunakan beton bertulang dengan metode cast insitu. Sedangkan untuk struktur Slab On Pile berupa plat slab tebal 35 cm direncakan dengan metode half slab yaitu setengah precast setebal 24 cm dan overtopping setebal 11 cm. Dari hasil pengujian SPT didapatkan tanah keras pada kedalaman 24 m sehingga digunakan pondasi tiang pancang. Desain jembatan ini menggunakan acuan/pedoman dari Design Struktur Beton Prategang (T.Y Lin dan Burns, 1982), RSNI T-02-2005 (Peraturan Pembebanan untuk Jembatan), RSNI T-03-2004 (Perencanaan Struktur Beton untuk Jembatan) dan Bridge Design Manual (BMS BDM, 1992), Bridge Design Code (BMS BDC, 1992) Selain itu perencanaan jembatan ini juga mengambil beberapa sumber pustaka sebagai bahan referensi.. ================================================================================================== Amusement Park Kenjeran Beach Bridges, better known by THP Kenjeran bridge built in Tambak Deres traffic lane road until Sukolilo Kenjeran, Surabaya . THP Kenjeran bridge built on the beach and also become a tourist spot with a pavilion and a fountain. The existing condition of the bridge is comprised of Prestressed Concrete Structure spans 30 m and pile on slab Structure span 6 m and 8.5 m. The THP Kenjeran bridge planned using Prestressed Concrete I-Girder span of 40m, type pile on slab Structure span 6 m. The main Structure of the THP Kenjeran bridge form Prestressed I beam (PCI), a method of post-tension and quality of Concrete K-800. To use the floor plate of reinforced Concrete construction with cast insitu method resulting in composite action between the beams precast and cast plate. And to the pillars also Structure planned to use reinforced Concrete cast insitu method. As for the Structure of slab on pile form of plates 35cm thick slab planned mothod that is half precast slab half as thick as 24 cm and 11 cm thick overtopping. SPT test results obtained the hard ground at a depth of 24m so used pile foundation. Bridge Design using a references/guidelines of Prestressed Concrete Structures Design (TY Lin and Burns, 1982), SRNIT-02-2005 (Loading Regulation of Bridge), RSNIT0302004 (Concrete Structural Design for Bridge) and Bridge Design Manual (BMS BDM, 1992), Bridge Design Code (BMS BDC, 1992). In addition, the bridge design is also taking some literature sources as references
Jiabao Yan - One of the best experts on this subject based on the ideXlab platform.
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tests and analysis on thermal expansion behaviour of steel strand used in Prestressed Concrete Structure under low temperatures
International Journal of Concrete Structures and Materials, 2018Co-Authors: Jian Xie, Jiabao YanAbstract:This paper presents the results of the tests and analysis on the coefficient of thermal expansion for the steel strand under combined low temperatures and prestressing forces. A test program was firstly carried out to study the thermal expansion behaviour of the seven-wire strand under combined different low temperatures ranging from 20 to − 165 °C and different prestressing levels ranging from 0 to 0.75 ft/ftk. The test results exhibited the thermal expansion behaviours of the steel strand under low temperatures in terms of thermal strain versus temperature curves, transit linear thermal expansion coefficient, and average thermal expansion coefficient. The influences of the low temperature and prestressing levels on the thermal expansion behaviours of the steel strand were separately discussed and analysed. Based on the test data, mathematical models were developed to predict the thermal expansion coefficients including transit and average of the steel strand. The developed regression models fully considered the influences of the low temperature and prestressing stresses acted on the strand. Finally, design equations were proposed to predict the transit and average thermal expansion coefficient of the steel strand under combined low temperature and prestressing forces.