| 1. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Industrial bridge construction: Need for a more effective bridge construction process
- 2015
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Ingår i: The Eighth International Structural Engineering and Construction Conference, Sydney, Australia, November 23-28, 2015. - : ISEC Press. - 9780996043717 ; , s. 1115-1120
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Konferensbidrag (refereegranskat)abstract
- Designing for ease of construction is something that is always demanded by contractors and a challenge for the designers. It is widely known that the ability to influence a structure and its future properties is at its greatest in early stages, i.e. the project preparation phase followed by the design phase. Despite the fact that there is an obvious need for knowledge of construction in design work, there is a lack of a consistent and structured transmission of experience between the construction stage and the designing engineers. The results in this project are achieved based upon three standalone studies. A thorough literature review, a meta-analysis of the current research covering effective bridge construction and a study of the current industrial view on how the industry intend to achieve a more effective bridge building process. Based upon these studies it is clear that using a holistic approach and a production oriented design methodology is likely to generate the progress that the construction industry needs.
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| 2. |
- Haghani Dogaheh, Reza, 1979, et al.
(författare)
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A new method for strengthening concrete structures using prestressed FRP laminates
- 2015
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Ingår i: 8th International Structural Engineering and Construction Conference: Implementing Innovative Ideas in Structural Engineering and Project Management, ISEC 2015; Sydney; Australia; 23 November 2015 through 28 November 2015. - : ISEC Press. - 9780996043717 ; , s. 1153-1158
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Konferensbidrag (refereegranskat)abstract
- Using bonded fiber reinforced polymer (FRP) laminates for strengthening and repair of structural members has been proven to be an effective and economic method. High strength and stiffness, light weight and good fatigue and durability properties of FRP composites together with advantages offered by adhesive bonding have made it a suitable alternative for traditional strengthening and repair techniques. It has also been recognized that pre-stressing the FRP laminates prior to bonding would bring additional advantages such as reduced crack widths, postponing the yielding in tensile reinforcement, increasing the load bearing capacity and saving reinforcement material. Using pre-stressed laminates, however, is associated with very high interfacial stresses in the bond line at the laminate ends, which necessitates the use of mechanical anchors. This paper presents a new method and a device for applying pre-stressed FRP laminates to flexural structural members without the need for mechanical anchorage of the laminates. The principle of the method is based on controlling the interfacial stresses in the bond line using a non-uniform pre-stressing force profile. The principle of the method along with lab verifications and field applications are presented and discussed.
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| 3. |
- Heshmati, Mohsen, 1987, et al.
(författare)
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HYGROTHERMAL DURABILITY OF ADHESIVELY BONDED FRP/STEEL JOINTS
- 2015
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Ingår i: Implementing Innovative Ideas in Structural Engineering and Project Management. - : ISEC Press. - 9780996043717 ; , s. 75-80
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Konferensbidrag (refereegranskat)abstract
- The use of fiber reinforce polymer, FRP, bonding to strengthen and repair deteriorated steel structures is increasing owing to its unique advantages over traditional strengthening and repair techniques. However, the lack of knowledge regarding environmental durability of adhesively bonded FRP/steel joints still hinders the widespread application of this method in steel structures. A number of studies have reported significant degradation of mechanical properties of these joints in hot and wet environments. In addition to that, the mechanisms of failure have been observed empirically to change from cohesive failure in the adhesive to apparent interfacial failure with increasing amount of moisture. This study presents the results of an experimental and numerical investigation to predict the mechanical behavior of FRP/steel joints after hygrothermal aging. First, moisture diffusion kinetics and mechanical degradation of a two-part commercially available epoxy adhesive and Carbon FRP material were experimentally characterized over a wide range of temperature and humidity conditions. These parameters were then incorporated in a coupled 3D diffusion-mechanical finite element, FE, model. In addition, bonded double-lap shear joints of CFRP/steel were aged for up to a year and tested to failure. It is found that the presence of moisture for less than a critical period can increase the joint strength. However, prolonged exposure to the same moisture content degrades the load-carrying capacity of the joint.
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| 4. |
- Shrestha, Kshitij C., et al.
(författare)
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Effect of surface roughening on concrete/trm bond
- 2017
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Ingår i: Proceedings of International Structural Engineering and Construction. - : ISEC Press. - 2644-108X. - 9780996043748 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Textile reinforced mortar (TRM) is applied on the concrete surface with the aim of strengthening reinforced concrete structures. The performance of the strengthened structural system is directly related to the bond between the existing concrete substrate and the freshly applied TRM layer. This paper presents the results of an experimental study carried out to investigate the significance of concrete surface preparation, performed prior to strengthening, on the bonding behavior of the TRM system. For this purpose, concrete slabs of size (500 mm × 500 mm × 100 mm) were prepared and strengthened using a 10-mm thick TRM layer. After that, the bond performance of the strengthening layer with the concrete slab was assessed using the pull-off test. Three different levels of surface roughening were considered before strengthening: (i) no roughening (regarded as the reference), (ii) low roughening level, and (iii) high roughening level. Two types of textile materials are used in strengthening systems: carbon and polyparaphenylene benzobisoxazole (PBO). A total number of 72 pull-off tests were performed, of which the results were analyzed to examine the significance of the test variables. Results revealed that as the concrete surface is more roughened before strengthening, the bond between concrete substrate and TRM layer becomes stronger. Moreover, the PBO-TRM systems exhibit more desirable bonding behavior compared to the carbon-TRM counterpart.
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| 5. |
- Strömberg, Larissa, et al.
(författare)
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Optimization parameter sets for sustainable concrete in tunnels
- 2019
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Ingår i: ISEC 2019 - 10th International Structural Engineering and Construction Conference. - : ISEC Press.
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Konferensbidrag (refereegranskat)abstract
- Public and private clients are beginning to set complex optimization requirements, taking into consideration environmental and cost-efficiency parameters over the built construction’s lifetime. The early design process is currently irreversible, and this makes it difficult to change a concrete structure in the later detailed design stage, when more accurate information is available regarding environmental impact and life-cycle costs. There is a dilemma in complying with existing standards to achieve technical requirements while optimizing a concrete structure in order to reduce the climate impact. The long-term goal of the project is to develop a new theoretical concept for dynamic optimization strategies which can be applicable to the early design, the client-requirement preparation, the detailed design, the production and the follow-up stages. This paper presents the results of the up-start phase of the project. The work has focused on the identification of current practice regarding clients’ requirements for technical, environmental and cost-efficiency parameters. An analysis of these requirements with sprayed concrete (shotcrete) in a number of ongoing projects has led to the identification of optimization parameter sets. The project has also shown how the physical values of those parameters can be collected from existing statistics, experience recovery databases and previous project requirements, or calculated according to standardized methods and tools. The concept developed will be used in a demonstrative modeling in the next project step.
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| 6. |
- Younis, Adel, et al.
(författare)
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A perspective on seawater/frp reinforcement in concrete structures
- 2017
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Ingår i: ISEC 2017 - 9th International Structural Engineering and Construction Conference. - : ISEC Press. - 2644-108X. ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Predictions show that more than half of the world population will lack sufficient freshwater by 2025. Yet, the construction industry uses a considerable amount of freshwater to produce concrete. To save resources of fresh water, using seawater seems to be a valid potential alternative that can replace freshwater for mixing concrete. This paper presents a short review performed on existing literature related to the usage of seawater in concrete structures. As a summary of the work presented: (a) It is noticeable that the current literature, generally, reports little or no negative effect of seawater on the characteristics of plain concrete, both in the short and in the long term; (b) steel corrosion caused by the presence of chloride appears to be the sole reason for not accepting the use of seawater in concrete preparation; (c) Fiber reinforced polymer (FRP) is discussed as a promising alternative to steel for seawater-concrete reinforcement, owing to their light weight, high tensile strength, and adequate corrosion resistance; and (d) A future outlook for using seawater accompanied by FRP reinforcement in concrete structures is discussed in terms of achieving sustainability goals.
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| 7. |
- Younis, Adel, et al.
(författare)
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Bond and shear-strengthening performance of FRCM composites
- 2019
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Ingår i: Proceedings of International Structural Engineering and Construction. - : ISEC Press. - 2644-108X. - 9780996043762 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- This paper is aimed at studying the bond and shear-strengthening performance of fabric reinforced cementitious matrix (FRCM) systems. Three FRCM systems were compared, namely, polyparaphenylene benzobisoxazole (PBO)-FRCM, Carbon-FRCM, and Glass-FRCM. At first, six double-shear specimens were tested to investigate the FRCM/concrete bond, with the test variables including the fabric type and the bond length. After that, seven shear-critical reinforced concrete (RC) beams were tested under three-point loading, considering the fabric type and strengthening configuration (full/intermittent) as the test variables. As for the double-shear test results, the failure observed was fabric/matrix debonding in carbon-FRCM, matrix/concrete debonding in PBO-FRCM, and fabric rapture in glass-FRCM. The FRCM/concrete bond increased with the bonded length, and the PBO-FRCM showed the highest bond to concrete. Regarding the RC beam tests, the FRCM-strengthened beams showed the same failure mode that is debonding at the FRCM/concrete interface. Nonetheless, FRCM had successfully strengthened the beams in shear: an average gain of 57% in the load carrying capacity was achieved as compared to the non-strengthened reference. Indeed, the full-length strengthening resulted in a better structural improvement compared to the intermittent-strengthening configuration. Amongst the three systems, carbon-FRCM systems were the most efficient in shear-strengthening RC beams.
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| 8. |
- Younis, Adel, et al.
(författare)
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FRCM shear strengthening for concrete beams
- 2017
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Ingår i: ISEC 2017 - 9th International Structural Engineering and Construction Conference. - : ISEC Press. - 2644-108X. - 9780996043748
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Konferensbidrag (refereegranskat)abstract
- This paper presents the results of an experimental study carried out to examine the efficacy of Fabric-Reinforced Cementitious Matrix (FRCM) in strengthening RC beams susceptible to shear failure. In this paper, seven shear-critical RC beams, of 2,500 mm in length, 150 mm in width, and 330 mm in depth, were tested under three-point loading until failure. Two main test variables were considered, which are: A) Strengthening material: carbon, polyparaphenylene benzobisoxazole (PBO), or glass FRCM, and b) Strengthening application pattern: A single full-length FRCM plate or a set of intermittent and spaced FRCM strips were applied along the critical shear zone. The test results confirmed the efficacy of FRCM strengthening in improving the load capacity of shear-critical RC beams. The FRCM-strengthening contributed to increases in the load capacity ranged between 31% and 100% compared to the reference specimen. The full-length strengthened specimens generally showed a better strength enhancement compared to the intermittent counterparts when using the same FRCM material. Such intuitive observation assures the importance of the amount of strengthening material applied in the critical shear zone. Besides, specimens utilizing carbon fibers in its FRCM strengthening material showed the highest strength enhancement among the three systems.
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| 9. |
- Younis, Adel, et al.
(författare)
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Microstructure investigation of seawater vs. Freshwater cement pastes
- 2019
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Ingår i: ISEC 2019 - 10th International Structural Engineering and Construction: Interdependence between Structural Engineering and Construction Management. - : ISEC Press. - 9780996043762
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Konferensbidrag (refereegranskat)abstract
- Recently, seawater has emerged as viable mixing water for concrete, especially in the case of non-reinforced concrete applications or with the use of non-corrosive reinforcement. Previous studies concerning seawater-mixed concrete mostly revealed an initial slight increase in its strength performance (i.e., till Day 14 following mixing), followed by a strength reduction of 7–15% (i.e., after 28 days or longer) as compared to the conventional freshwater-mixed concrete. With an attempt to explain such observations, this paper aims at comparing the microstructure of freshwater- and seawater-mixed cement pastes. Scanning electron microscopy was utilized to observe the microstructure of freshwater and seawater pastes at Days 3 and 28 following mixing. At Day 3, seawater paste was observed to have more densified microstructure as compared to that of the freshwater counterpart, resulting in relatively higher strength performance. At Day 28, the microstructure was almost similar for the two cement pastes. However, seawater paste was observed to have salt impurities as a result of seawater ions, which possibly cause a slightly lower strength performance as compared to the freshwater paste.
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| 10. |
- Younis, Adel, et al.
(författare)
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Strength, shrinkage, and permeability performance of seawater concrete
- 2019
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Ingår i: ISEC 2019 - 10th International Structural Engineering and Construction: Interdependence between Structural Engineering and Construction Management. - : ISEC Press. - 9780996043762
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Konferensbidrag (refereegranskat)abstract
- Given the increasing global concern of freshwater scarcity, the use of seawater in concrete mixtures appears to be a way forward towards achieving sustainable concrete, especially in the case of non-reinforced concrete applications or with the use of noncorrosive reinforcement. This paper reports on the results of an experimental study to compare the freshwater- and seawater-mixed concretes in terms of their strength, shrinkage and permeability performance. The experimental program included the following: (i) compressive strength test (at 3, 7, 28, and 56-day ages); (ii) concrete shrinkage test (at Days 4, 7, 14, 21, 28, and 56 following mixing); and (iii) permeability tests (rapid chloride permeability and water absorption at Days 28 and 56 following mixing). As for the study results, seawater concrete showed a slightly higher early-age (i.e., till Day 7) strength performance than that of freshwater-mixed counterpart, followed by a strength performance that is 7–10% inferior to the freshwater concrete after 28 days or later. Also, the shrinkage of seawater concrete was slightly higher than that of freshwater concrete, with a difference of 5% reported after 56 days following mixing. Finally, the permeability performance of hardened concrete in seawater and freshwater mixtures was similar.
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