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Fiber optic distributed sensor for condition monitoring of underground concrete structures
Published in Mark Knight, Neil Thomson, Underground Infrastructure Research, 2020
Yang Zhao, Ming Zhao, Farhad Ansari
Fiber-reinforced plastics (FRP) have been increasingly used in conjunction with civil structural materials, either as reinforcement for concrete structures or for repair and strengthening of existing structural elements (Dolan, et al, 1998). In comparison with steel reinforcement, the primary attributes of FRP bars are of reduced mass, high tensile strength, corrosion resistance, lower relaxation, high strength-to-weight ratio, non-magnetic properties ease of handling and cutting. Important applications of FRP composites pertain to rehabilitation of cracked concrete members. In such applications, it is important to ensure adequate composite action between the FRP reinforcement and the existing structures. Five types of failure modes can be expected when reinforced concrete beams are strengthened with CFRP fabrics. These failure modes include: (1) laminate rupture; (2) crushing of concrete in compression; (3) yielding of steel rebar; (4) shear failure of the beam; (5) peeling of CFRP fabric.
Casting and Foundry Work
Published in Sherif D. El Wakil, Processes and Design for Manufacturing, 2019
Cast metals are generally weaker in tension in comparison with their compressive strengths. Nonetheless, the casting process offers the designer the flexibility of distributing the masses of a section with a freedom not readily available when other manufacturing processes are employed. Therefore, when preparing a design of a casting, try to distribute masses in such a manner as to lower the magnitude of tensile stresses in highly loaded areas of the cross section and to reduce material in lightly loaded areas. As can be seen in Figure 3.27, a T section or an I-beam is more advantageous than just a round or square one when designing a beam that is to be subjected to bending.
Bending Stresses in Beams
Published in B. Raghu Kumar, Strength of Materials, 2022
Beams that are built of more than one material are called composite beams. Examples are bimetallic beams, sandwich beams, reinforced concrete beams as shown in the Fig. 5.6. Composite beams can be analyzed by the same way as that of ordinary beam. The main advantage with these beams is it can withstand with more bending load within less space/cross sectional area compared to beam with single material.
Investigation of the Optimum Height of Railway Embankments during Earthquake Based on Their Stability in Liquefaction
Published in Journal of Earthquake Engineering, 2019
S. Amir Tabatabaei, Morteza Esmaeili, Javad Sadeghi
Different failure modes of railway embankments have been reported in the technical literature [Patilakis, 2011]. The most common failure modes, such as local failure, general failure, flexural beam failure, and slumping failure, are shown in Fig. 2. Liquefaction and lateral spreading of foundation can lead to various failure modes in embankment. Since this subject has not been discussed extensively in previous researches, this study focusses on diagnosing the various failure modes of the overall system for different railway embankment heights due to liquefaction and lateral spreading. For this purpose, the horizontal strain has been recorded and analyzed in the central axis of the embankment nodes deriving the desired failure mode of the system.
Experimental investigation and analysis of pure bending plastic hinge zone in hybrid beams reinforced with high reinforcement ratio under static loads
Published in European Journal of Environmental and Civil Engineering, 2022
Figure 12 presents the crack patterns at failure of tested beams. All the beams were ruptured after yielding of steel and followed by ruptured of GFRP bars or concrete crushing. As mentioned above, after yielding of steel, the deflection and crack widths significantly increased until, finally, the top extreme concrete compressive fibre reached its ultimate strain and crushed or GFRP bars reached its ultimate strain and ruptured. During the testing, no signs of bond–slip occurred between the reinforcing bars and concrete for all tested beams. As can be seen on Figure 12, the distribution of cracks prolongs over a wide length of the test span. The number of cracks and crack spacings in hybrid GFRP/steel depends on the reinforcement ratio. As increasing the total reinforcement ratio, i.e. increasing the number of longitudinal bars, the number cracks are expanded, the crack distribution length is enhanced and the average crack spacing is reduced (Bischoff & Paixao, 2004; Yao & Wu, 2016). At the failure stage, the cracks propagate predominantly in vertical direction in the pure bending zone and the shear span for groups of B1 and B2 specimens. For group of beam B3 with higher hybrid reinforcement ratio, wide inclined cracks appear below the loading point and propagate toward the compression zone in the midspan. As an example, beam B3-3G14-2S10 at the failure load, a critical diagonal crack close to pure flexural zone develops into the compressive concrete zone at which the concrete has been crushed (Figure 12(g)). For this case, the beam tends to experience the failure mode of flexure-shear but the flexural failure is predominant because of tensile steel yielding before concrete crushing. Therefore, depending on the longitudinal reinforcements, the failure modes of tested beams are various: beam B1-2G10-2S10 is failed in flexure by rupture of GFRP bars after steel yielding; the failure of beams B3-3G14-2S10, B3-3G14-2S12 and B3-3G14-2S14 occurred due to yielding of the tensile steel bars and concrete crushing combined with shear failure, other beams are failed in flexure by crushing of concrete in compression zone after yielding of steel bars.