The Experts below are selected from a list of 10236 Experts worldwide ranked by ideXlab platform
Raafat Elhacha - One of the best experts on this subject based on the ideXlab platform.
-
anchorage system to prestress frp laminates for flexural strengthening of steel concrete composite girders
Journal of Composites for Construction, 2013Co-Authors: Raafat ElhachaAbstract:Using externally bonded (EB) fiber-reinforced polymer (FRP) laminates for strengthening steel-concrete composite girders has recently received more attention from researchers. By Prestressing the EB FRP laminates, the material is used more efficiently because a greater portion of its tensile capacity is employed and it contributes to the load-bearing capacity under both service and ultimate conditions. This is an ideal technique because it combines the advantage of using noncorrosive and lightweight advanced composite materials in the form of bonded FRP laminates with the high efficiency offered by external Prestressing. An innovative mechanical anchorage system was developed to prestress the FRP laminates directly by jacking and reacting against the steel girder itself. The efficiency of the system was investigated using two types of FRP laminates for flexural strengthening of large-scale steel-concrete composite girders. The used FRP composite materials included carbon-fiber-reinforced polymer (CFRP) plate and steel-fiber-reinforced polymer (SFRP) sheets. The developed anchorage/Prestressing system was easy to use/apply and proved to be a feasible and practical system for Prestressing both CFRP plate and SFRP sheet. The Prestressing levels in the FRP laminates were sufficiently maintained. The Prestressing losses were insignificant.
Masoud Motavalli - One of the best experts on this subject based on the ideXlab platform.
-
mode i fatigue crack arrest in tensile steel members using prestressed cfrp plates
Composite Structures, 2017Co-Authors: Masoud Motavalli, Elyas Ghafoori, Ardalan Hosseini, Alain Nussbaumer, Xiao Ling ZhaoAbstract:Abstract Numerous studies in the literature have shown that the strengthening of steel members using carbon fiber reinforced polymer (CFRP) composites can significantly extend the fatigue life of these structures. However, not enough attention has been focused on the potential of prestressed CFRP reinforcements for fatigue crack arrest in such members. In the current study, a simple analytical model is proposed to calculate the required Prestressing level in the CFRP reinforcements in order to arrest the propagation of an existing fatigue crack in tensile steel members. Furthermore, a novel mechanical unbonded system is developed to anchor the high Prestressing forces in CFRP reinforcements to the steel substrate using friction. A set of fatigue tests are performed on unstrengthened and strengthened precracked steel plates to verify the proposed model. The experimental results of the current study showed that the application of nonprestressed ultra-high modulus CFRP plates as externally bonded reinforcements can increase the fatigue life of precracked steel plates by a factor of 4.3. However, fatigue crack arrest is only possible when prestressed CFRPs of a certain Prestressing level are used. Based on the analytical, numerical, and experimental results of the current study, it can be concluded that existing fatigue cracks in tensile steel members can be arrested using the proposed prestressed unbonded reinforcement system with the initial Prestressing level calculated using the proposed model. In addition, some design recommendations are provided for fatigue crack arrest in practical cases.
-
determining the remaining tendon force of a large scale 38 year old prestressed concrete bridge girder
Pci Journal, 2006Co-Authors: Christoph Czaderski, Masoud MotavalliAbstract:A reliable method to determine the remaining Prestressing force is often needed in routine inspection of bridges, during rehabilitation of structures, or when retrofitting for increased vehicle capacity. This article reports on a study that was undertaken to determine the remaining tendon force of a large-scale (17 meters long), 38-year-old prestressed concrete bridge girder. The authors used a semi-destructive test method and compare measurements of the Prestressing force losses determined by their method with calculations methods based on fib guidelines and Swiss code. They found that calculated and measured Prestressing force losses were generally in good agreement. A long-term Prestressing force loss of about 20% was determined. The authors conclude that their material tests on the Prestressing steel showed that 38 years of constant stress had no discernable effect on its tensile strength. This article reports on the first part of an extensive test program that will be carried out on five similar test beams.
Salman A Alduheisat - One of the best experts on this subject based on the ideXlab platform.
-
cathodic polarization behavior of the structural steel wires under different Prestressing conditions
Journal of materials research and technology, 2017Co-Authors: Amjad Saleh Elamoush, Salman A AlduheisatAbstract:Abstract Cold-drawn structural steel wires prestressed to different levels and cathodically polarized at various potentials were investigated using electrochemical techniques and slow strain rate tests. The potentiodynamic polarization revealed that Prestressing enhances the active anodic dissolution of the structural steel wires. The corrosion current density and corrosion potential were observed to vary with Prestressing levels applied to the structural steel wire specimens. The structural steel wire prestressed to 80% of its original tensile strength and cathodically polarized at −1500 mV exhibited the highest current densities and lowest corrosion potentials after potentiodynamic polarization, which indicate that the above Prestressing and cathodic polarization conditions lower the corrosion resistance of the material. Moreover, the tensile results show that the structural steel wire prestressed to higher levels and cathodically polarized at lower potentials was more susceptible to degradation of the tensile properties. The structural steel wire prestressed to 80% level and cathodically polarized at a potential of −1500 mV exhibits the lowest UTS and ductility. The tensile fracture surfaces of the steel wires prestressed and cathodically polarized under above conditions exhibit mostly quasi-cleavage brittle fracture character. Furthermore, the brittle regions were observed to increase with increasing the Prestressing levels and decreasing the cathodic polarization potentials applied to the structural steel wires.
Gangbing Song - One of the best experts on this subject based on the ideXlab platform.
-
development of a self stressing nitinb shape memory alloy sma fiber reinforced polymer frp patch
Smart Materials and Structures, 2015Co-Authors: Mossab Eltahan, Mina Dawood, Gangbing SongAbstract:The objective of this research is to develop a self-stressing patch using a combination of shape memory alloys (SMAs) and fiber reinforced polymer (FRP) composites. Prestressed carbon FRP patches are emerging as a promising alternative to traditional methods to repair cracked steel structures and civil infrastructure. However, Prestressing these patches typically requires heavy and complex fixtures, which is impractical in many applications. This paper presents a new approach in which the Prestressing force is applied by restraining the shape memory effect of NiTiNb SMA wires. The wires are subsequently embedded in an FRP overlay patch. This method overcomes the practical challenges associated with conventional Prestressing. This paper presents the conceptual development of the self-stressing patch with the support of experimental observations. The bond between the SMA wires and the FRP is evaluated using pull-out tests. The paper concludes with an experimental study that evaluates the patch response during activation subsequent monotonic tensile loading. The results demonstrate that the self-stressing patch with NiTiNb SMA is capable of generating a significant Prestressing force with minimal tool and labor requirements.
Jongsung Sim - One of the best experts on this subject based on the ideXlab platform.
-
practical crack control during the construction of precast segmental box girder bridges
Computers & Structures, 2005Co-Authors: Doyoung Moon, Jongsung SimAbstract:Cracks that occurred in the bottom slab of a precast segmental bridge were investigated through a construction sequence analysis, which revealed that the cracks were caused by excessive deformation during temporary post-tensioning while joining the segments. In addition, a parametric study was performed to evaluate the effects of the Prestressing sequence, bottom slab thickness, and position of the Prestressing anchors. The structural behavior of the girder sections was greatly affected by the thickness of the bottom slab and the position of Prestressing anchors, but not by the Prestressing sequence. Based on the results, a construction method that prevents the cracks is proposed.
