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Structure and architecture
Published in Angus J. Macdonald, Structure and Architecture, 2018
The neglect of structural issues in the determination of the form of a building can therefore be problematic if a large span is involved. The small scale of the buildings already mentioned meant that the internal forces were nowhere so large that they could not be resisted without the use of excessively large cross-sections. Eero Saarinen’s terminal for TWA at Idlewild (now Kennedy) Airport, New York (Figure 9.15) paid little regard to structural logic. Although the roof of this building was a reinforced concrete ‘shell’ it did not have a form-active shape. Because it was relatively large, difficulties occurred with the structure. These were overcome by modifying the original design to strengthen the shell in the locations of highest internal force. Very large volumes of reinforced concrete were involved and the envelope is far from being a ‘delicate thin shell’ as is sometimes claimed.
RCC use in dam rehabilitation projects
Published in L. Berga, J.M. Buil, C. Jofré, S. Chonggang, Roller Compacted Concrete Dams, 2018
During 1995, the remnants of tropical storm Alberto hovered over South Georgia causing more than 230 dams to fail. One such dam that ultimately failed was Tobesofkee Creek Dam, which impounded a water supply reservoir for the city of Forsyth. The existing dam was an earthfill embankment covered with a thin lightly reinforced concrete shell. This dam had also failed during its initial filling in the late 1980s due to faulty construction. During Alberto and a subsequent flood the overflow spillway operated causing the dam to breach. The city, having faced two failures of the same dam and in dire need of re-establishing their water supply, decided on the advice of their engineer to replace the existing dam with an RCC gravity dam. The RCC dam would occupy the footprint of the old dam once its remains were removed and be founded on rock. The new RCC dam was 9.5 m high by 154 m long. The 5,800 m of RCC was placed in 16 one shift working days. Figure 13 shows the dam after the second failure and Figure 14 shows the new replacement RCC gravity dam with an exposed stepped RCC downstream face and the new overflow spillway operating.
Shells of cracked reinforced concrete chimneys, silos and cooling towers walls as a problem of durability exploitation
Published in Alphose Zingoni, Insights and Innovations in Structural Engineering, Mechanics and Computation, 2016
In designing silos, cool towers or chimneys wall there are no place for the appearance of the larger cracks (Fig. 1). Horizontal and vertical cracks can caused corrosion of concrete and steel bars. Cracks decreases stiffness of reinforced concrete shell construction. Local and global imperfections of the walls are increasing according to greater number of cracks. Taking into account these facts, cracks reduce the service life of objects. Horizontal and vertical cracks allow condensate water infiltrates into wall. It causes corrosion and moisture of concrete wall and during winter time cracks become bigger because if glaciations water in cracks. Problems with a large number of cracks on concrete shell walls occurred in last years in Poland. It was connected with changing codes and in particularly introduction requirement of double reinforcement of concrete walls, bigger covers, For example until the end of XX centaury reinforcement bars in chimney wall were located in one row, near the external surface. After receiving in Poland European Standards two rows of reinforcement are demanded. The same requirement applies to the silos walls. It caused several difficulties in building chimneys because of little space of reinforcement bars in rather thin wall.
Finite element modelling of shear critical glass fibre-reinforced polymer (GFRP) reinforced concrete beams
Published in International Journal of Modelling and Simulation, 2021
Ferreira et al. [2] proposed a finite element model for GFRP reinforced concrete beams. The proposed model utilized two-dimensional degenerated concrete shell elements. However, this element is not good to show the crack patterns of the beams. Also, the beam was not shear critical since the shear span to depth ratio was 7 and the beam contains stirrups. Nour et al. [3] implemented concrete smeared crack approach [4] into the commercial finite element program ABAQUS [5] to analyze GFRP reinforced slender rectangular beams with steel stirrups. The tension-stiffening model proposed by Bischoff and Paixao [6] was used in the model with some modifications. However, this model performed well to simulate the behaviour for service load level.