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Strengthening and Rehabilitation
Published in Wai-Fah Chen, Lian Duan, Bridge Engineering, 2003
F. Wayne Klaiber, Terry J. Wipf
Lightweight concrete for deck replacement can be either cast in place or installed in the form of precast panels. A cast-in-place lightweight concrete deck can easily be made to act compositely with the stringers. The main disadvantage of a cast-in-place concrete deck is the length of time required for concrete placement and curing.
Materials
Published in Bjørn N. Sandaker, Arne P. Eggen, Mark R. Cruvellier, The Structural Basis of Architecture, 2019
Bjørn N. Sandaker, Arne P. Eggen, Mark R. Cruvellier
In terms of type of structural load-carrying capability, concrete on its own is strong in compression but very weak in tension. (See Table 5.1 and Fig. 5.4.) In structural elements, therefore, concrete is typically reinforced with steel bars so as to provide the resulting composite material with tensile as well as compressive strength. There are two primary ways of producing structural components: cast-in-place or precast concrete. Cast-in-place concrete (also called “in situ” concrete) is poured directly on site and allows for monolithic structural systems in a wide variety of shapes. By creating the appropriate formwork, concrete has a remarkable sculptural potential, so that establishing shape, size, texture, color, etc. can be significant design factors. Precast concrete, on the other hand, is generally made in a factory, where the mixing of concrete and casting of elements take place in a controlled environment and the finished structural element is later transported to the building site. Common precast concrete components are beams, columns, slabs, and wall panels, as well as unreinforced products like concrete masonry blocks. Notably, reinforcement of such precast elements may be of the pre-stressed type, whereby compression forces are introduced into the concrete cross-section by the pre-tensioning of steel strands before the concrete is cast and hardens in the manufacturing plant. Such a strategy is typically used to anticipate and counter the loading that will eventually be applied to the structural element by partly or totally eliminating tensile stresses in the cross-section. Pre-stressing of cast-in-place concrete can be done by means of the post-tensioning technique, whereby steel strands that are threaded through channels within the concrete are stressed after the concrete has hardened. Pre-stressed concrete is generally a more efficient material than is conventionally reinforced concrete, resulting in the opportunity for a lighter, more slender structure, or one that spans greater distances or carries greater loads.
Recent Application of and Research on Concrete Arch Bridges in China
Published in Structural Engineering International, 2023
J.P. Liu, B.C. Chen, C. Li, M. J. Zhang, T.M. Mou, H. Tabatabai
The Melan method refers to a construction method for concrete arches patented by an Austrian engineer—Josef Melan—at the end of the nineteenth century. The first Chinese bridge built using this method is the Mayisha Bridge, which was completed in 1980 with a span length of 60 m. This was followed by three other bridges built before 1990. In those four bridges, the embedded steel framework was made by small members to reduce steel consumption, and auxiliary measures were employed to decrease the deformation during the pouring of concrete. In some cases, water tanks hung on the framework were evenly loaded by filling with water before concreting and then emptied when concrete was poured into the respective segments. In other cases, the framework was loaded by prestressed cables anchored to the ground, and the pre-applied forces in the cables were adjusted according to the concreting process. After 1990, the CFST arch was incorporated into the Melan method, which is called the CFST Melan method in this paper. An embedded CFST framework can greatly improve the stiffness of the arch while reducing the consumption of steel material and enable a more economical construction for long span concrete arch bridges.17 During construction, the hollow and relatively lightweight and stiff trussed arch members are first erected using steel tubes. Then the core concrete is pumped into the tubes to form the CFST framework that will serve as a stiff and strong supporting structure for the formwork and the cast-in-place concrete. Finally, concrete is cast to produce the concrete arch.
Finite Element Study: Rocking Wall-Floor Connection of Precast Concrete Load-Bearing Structures Subjected to Quasi-Static Lateral Loading
Published in Journal of Earthquake Engineering, 2023
Mohd Asha’ari Masrom, Nor Hayati Abdul Hamid
The arrangement of part instances in the connection assembly can be seen clearly in Fig. 11. The steel shaft, hexagonal nut, and washer were simplified by modeling them as a single body, as depicted in Fig. 9. The threaded part of the steel shaft was ignored. Meanwhile, the L-angle and shear stud was modeled individually and merged later into one component, as demonstrated in Fig. 10. The full grout coupler did not model explicitly. This was considered by assuming that the reinforcements did not fracture in the coupler region which is usually observed in many coupler tensile tests. The protruding and connected bars in the precast plank were simplified as one continuous element which was not exactly modelled, as per the detailed drawing shown in Fig. 2. The recess formed in the precast plank (to be cast-in-place after precast member installation) as shown in Fig. 2 also did not model explicitly. Instead, the cast-in-place concrete was modeled as part of the precast concrete plank. This was considered by assuming that they behaved similarly, and no separation occurred between them.
Modelling of cast-in-place concrete tunnel liners condition
Published in Structure and Infrastructure Engineering, 2020
Mohamed S. Yamany, Emad Elwakil
Tunnels are lined to support and stabilise the surrounding ground and prevent the ingression of the groundwater. Tunnel liners are temporary or permanent, and they are constructed using various methods such as cast-in-place concrete, shotcrete/sprayed concrete, precast concrete, steel, timber, or masonry. The analysis of the data collected for the current study shows that about 62% and 7.5% of the highway tunnels across the U.S. are lined using cast-in-place concrete and sprayed concrete, respectively. The precast concrete liners have been reinforced by steel reinforcement, but lately, they have been reinforced by steel fibre due to its advantages such as strong corrosion and cracking resistance. However, only 3.8% of tunnels across the U.S. are lined using precast concrete. Due to their extensive usage across the U.S., the current research focuses on modelling the condition of cast-in-place concrete tunnel liners.