Prestressed concrete has long been accepted in statically loaded structures. Thus, for many years now we have seen the construction of prestresed concrete bridges, dams, pipelines, reservoirs and various structures including more recently atomic reactor pressure vessels. These stand as irrefutable proof of engineers' confidence as to the integrity of this new material. In recent years prestressed concrete has been used in seismic resistant structures. Just like any other new material, it will attract criticism and comment, sometimes by people who may not have had the opportunity of full investigation of the material in question. Furthermore, today engineers are more critical of any new material or technique and will seldom accept them unless conclusive evidence of their performance can be produced. This is as it should be. The purpose of this paper is to observe the application of prestressed concrete to seismic resistant multi-storey structures. However, this paper should be read bearing in mind the fact that the widest application of prestressed concrete (to bridge and kindred structures) has been in the countries subject to earthquake and with operative seismic codes. In the paper, the latest seismic design procedure for prestressed concrete buildings in Indonesia is introduced. The current design method is based on the latest Indonesian Building Code for Structural Concrete and Seismic Code, namely SNI 2847:2013 and SNI 1726:2012, respectively. The design method itself is not a novelty to those who are familiar with the capacity design developed for years. This paper is also intended to bring the attention of structural designers and other engineers to the option of using partially-prestressed concrete in buildings. The results of an investigation into the seismic resistance of partially-prestressed concrete frames are described. The experimental part of the project involved the testing of six near full scale beam-interior column assemblies under static cyclic loading to obtain information for seismic design.
In this paper, further analysis from the result of spun pile test under reverse flexural load and combined with two levels constant axial load, 40 tons (0.08fc'Ag) and 80 tons (0.16fc'Ag) is presented. The analysis is related to the confinement behavior of the concrete section of pile using the low amount of spiral reinforcement. It was shown that the strain readings from the spiral reinforcement indicate a subtle contribution regarding the confinement mechanism of the hollow section of a pile. In addition, it was evident that spiral reinforcement seems to be compressed when the concrete section resists compression strain due to flexural load. The crushing of concrete at ultimate condition could also not be resisted by spiral reinforcement by any means.
This research investigates the effect of the presence of infilling concrete inside of the middle void of the spun pile on its flexural behavior. The flexural monotonic load without axial load testing was conducted on the full-scale of two spun piles with infilling concrete. The dimensions of the pile were 400 mm in diameter, 75 mm in wall thickness, and 6,000 mm in length. The compressive strength of the concrete of the spun pile and infilling concrete was 58.4 MPa and 26.9 MPa, respectively. The observed flexural behaviors were the moment capacity, displacement ductility factor, and failure modes. Comparing with the previous research result about the testing of the spun pile without infilling concrete, the present testing results show that the presence of infilling concrete as the core of the spun pile’s section did not have a significant effect on the flexural performances of tested spun pile. Low compressive stress on compression fiber, due to no axial load, caused no concrete crushing occurred and the confinement mechanism of spiral reinforcement did not work. The fracture of the PC bar on extreme tensile fiber become the trigger of the failure of the pile. All piles had a ductility factor around µ∆ = 4 in all cases. According to the seismic design code requirement, the spun piles were appropriate to be applied to a moderate seismic risk area. In application, due to seismic load, the piles should be designed remaining in the elastic state.
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