• Journal of the Korea institute for structural maintenance and inspection
• /
• v.5 no.2
• /
• pp.103-109
• /
• 2001

In this paper, the prestressing order of tendons is studied to minimize a bursting force of an anchorage. The bursting forces is a primary factor of anchorage failures. The forces of the anchorage depend on the prestressing order and size of the tendons, if a lot of tendons are introduced to the anchorage. Many studies have been made to analyze the bursting force of the anchorage. However, the studies have been limited to the bursting forces of the anchorage having one or two tendons. PSC box girder bridges usually have a lot of tendons. And the difference of the bursting forces lies in the prestressing order of the tendons. As a result of the lack of studies on the prestressing order for the bridges, the order depends on the designer's intuition and experiences. It may be stated that this study should be useful for determining the reasonable prestressing order of tendons for the PSC box girder bridges.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.5
• /
• pp.97-105
• /
• 2006

PSC box girder bridges usually have a lot of tendons, and the difference of the bursting forces lies in the prestressing order of the tendons. As a result of the lack of studies on the prestressing order for the bridges, the order depends on the designer's intuition and experiences. In this paper, with investigation into various methods determining the bursting force of the anchorage, reasonable prestressing order is determined by analysis of PSC beam bridge and PSC box girder bridge with most suitable method. It may be stated that this study would be useful for determining the reasonable prestressing order of tendons for the PSC box girder bridges.

• Advances in concrete construction
• /
• v.4 no.3
• /
• pp.173-194
• /
• 2016

This paper consists in a study of a new contructive sequence of road viaducts with Movable Scaffolding System (MSS) using numerical tools based on finite element method (FEM). Traditional and new sequences are being used in Spain to build viaducts with MSS. The new sequence permits an easier construction of one span per week but implies some other issues related to the need of two prestressing stages per span. In order to improve the efficiency of the new sequence by reducing the number of prestressing stages per span, two solutions are suggested in this study. Results show that the best solution is to introduce the 100% of the prestressing force at the self-supporting core in order to improve the road viaduct construction with movable scaffolding system by reducing execution time without increasing economic costs.

• Steel and Composite Structures
• /
• v.26 no.2
• /
• pp.213-226
• /
• 2018

This paper focuses on the seismic protection of slender old masonry structures by the implementation of prestressing devices at key locations. The devices are vertically and externally located inside the towers in order to be reversible and calibrated. An extensive parametric study on a selected slender tower is carried out based on more than 100 nonlinear static simulations aimed at investigating the impact of different parameters on the seismic performance: (i) different prestressing levels; (ii) shape memory alloy superelasticity and (iii) changes in prestressing-forces in all the stages of the analysis until failure and masonry toe crushing. The tendon materials under analysis are conventional prestressing steel, fiber-reinforced polymers of different fibers and shape memory alloys. The parametric study serves to select the most suitable prestressing device and optimal prestressing level able to dissipate more earthquake energy. The seismic energy dissipation is evaluated by comparing the structural capacity curves in original state and retrofitted.

• Steel and Composite Structures
• /
• v.23 no.5
• /
• pp.517-527
• /
• 2017

In this paper, the effect of active confinement on the compressive behaviour of circular steel tube-confined concrete (STCC) and concrete-filled steel tube (CFST) columns is investigated. In STCC columns the axial load is only applied to the concrete core, while in CFST columns the load is carried by the whole composite section. A new method is introduced to apply confining pressure on fresh concrete by laterally prestressing steel tubes. In order to achieve different prestressing levels, short-term and long-term pressures are applied to the fresh concrete. Three groups of STCC and CFST specimens (passive, S-active and L-active groups) are tested under axial loads. The results including stress-strain relationships of composite column components, secant modulus of elasticity, and volumetric strain are presented and discussed. Based on the elastic-plastic theory, the behaviour of the steel tube is also analyzed during elastic, yielding, and strain hardening stages. The results show that using the proposed prestressing method can considerably improve the compressive behaviour of both STCC and CFST specimens, while increasing the prestressing level has insignificant effects. By applying prestressing, the linear range in the stress-strain curve of STCC specimens increases by almost twice as much, while the improvement is negligible in CFST specimens.

• Structural Engineering and Mechanics
• /
• v.48 no.5
• /
• pp.615-642
• /
• 2013

In this paper a study on prestressed concrete slab bridges is presented. A design philosophy based on the concept of load balancing through prestressing is proposed in order to minimize the effects of delayed deformations due to creep. Aspects related to the stress redistribution inside these bridges for time-dependent phenomena are analyzed and discussed, by applying the principles of aging linear visco-elasticity. Prestressing is seen as an equivalent external load which counterbalances the permanent loads applied to the bridge, nullifying the elastic deflections due to sustained loads, and thus avoiding the related delayed deformations. An optimization of the structural behavior through the use of one-way prestressing is achieved. The determination of a convenient variable depth of slab bridges and the correspondent layout of tendons is considered as a useful means for applying the load balancing concept in actual cases of structures like long cantilevers or bridge decks. A case-study related to the slab bridges built 30 years ago at Jeddah in Saudi Arabia is presented and discussed, in order to show the effectiveness of the proposed approach to the conceptual design of prestressed concrete bridges.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.1
• /
• pp.419-424
• /
• 2012

This study is a research on the buckling analysis of a portable prestressing device using finite element analysis program, ABAQUS. In order to produce 50m-span PSC girders using pretensioning method, a portable prestressing device has to endure a large jacking force about 10MN. Therefore it shall be safe and stable about the jacking force. In this study, the buckling analysis technique is developed and the buckling analysis of a portable prestressing device is performed using previous studies about the analytical model that the validity of the analytical model was demonstrated by comparing analytical results with experimental results. The stability of the device to produce 10m span PSC girders is investigated.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.5
• /
• pp.101-108
• /
• 2008

The primary objective of this research is a study on the pullout bond characteristics of untensioned prestressing strand in concrete. The bond characteristics of untensioned prestressing strand in concrete differs from that of deformed reinforcing bar. In order to use and design untensioned prestressing strand as deformed reinforcing bar, a study for bond characteristics of the untensioned prestressing strand was progressed. Major test variables are embedment length ($10d_b{\sim}60d_b$), concrete cover (45mm, 70mm, 100m) and diameter of strands. (12.7mm : SWPC7, 9.3mm : SWPC7A) As a results, these showed that average bond stress was decreased as a growing the embedment length, and then showed that the bond performance of untensioned prestressing strand was improved if embedment length was above 60$60d_b$.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.15 no.2
• /
• pp.281-291
• /
• 2002

This paper describes the minimum cost design of prestressed reinforced concrete (PRC) hem with rectangular section. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non prestressing steel, and formwork is minimized. The design constraints include limits on the minimum deflection, flexural and shear strengths, in addition to ductility requirements, and upper-Lower bounds on design variables as stipulated by the specification. The optimization is carried out using the methods based on discretized continuum-type optimality criteria(DCOC). Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables - effective depth, eccentricity of prestressing steel and non prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. In this paper the effective depth is considered to be freely-varying and one uniform for the entire multispan beam respectively. Also the maximum eccentricity of prestressing force is considered in every span. In order to show the applicability and efficiency of the derived algorithm, several numerical examples of PRC continuous beams are solved.

• Structural Engineering and Mechanics
• /
• v.4 no.2
• /
• pp.177-190
• /
• 1996

A method to numerically evaluate the behaviour of single span beams, prestressed with external tendons and symmetrically loaded is presented. This algorithm, based on the Finite Difference Method, includes second order effects and large displacements in an attempt to more fully understand the behaviour of the beam up to collapse. The numerical technique discussed is particularly appropriate for the analysis of R.C. and P.C. beams rehabilitated or strengthened by means of external prestressing but it is reliable for the analysis of new beams as well.