Experimental study of externally prestressed segmental beam under torsion

Externally prestressed segmental (EPS) concrete beams are widely used in the construction of bridge structures today. The EPS concept has become an attractive tool for rehabilitation and strengthening of existing bridges which have insufficient strength and/or excessive deflection and cracking. EPS bridges are affected by combined stresses (bending, shear, normal, and torsion) at the joint interface between the segments. This paper presents an experimental investigation of the structural behaviour of EPS bridge beams under combined stresses, i.e. bending, shear and torsional stresses. An experimental study of two different external tendon layouts, two types of joint between segments and different levels of torsional force applied at different load eccentricities was conducted. It was concluded that torsion reduced the vertical load and vertical deflection at the onset point of nonlinearity as well as at a failure load. Furthermore, the opening between segments was the reason behind the nonlinear behaviour of EPS beams. Torsion did not only alter the value of the failure load, tendon strain and deflection of the beams but it also altered the failure mechanism. Furthermore, due to the shear key, there was a difference between the onset points of nonlinearity load for the different tendon layouts and joint types

Effect of torsion on externally prestressed segmented box bridge girder

Externally Prestressed Segmented (EPS) concrete box bridges are widely used in the construction of bridge structures today. EPS has also become an attractive tool for rehabilitation and strengthening of existing structures with insufficient strength and/or excessive deflection and cracking. The behaviour of externally prestressed segmented bridge has been studied under either shear force or combined bending moment and shear forces only. No extensive research work has been carried out so far to study the effect of combined bending, shear force,normal force and torsion on the structural behaviour of these bridges. Therefore, there is a need to focus on this area; and hence, both analytical and experimental investigation need to be carried out to study the behaviour of EPS box bridge under combined bending, shear, normal force and torsion. The key objective of the research was to obtain a better understanding of the behaviour of externally prestressed segmented box bridge girders under combined loading, and to study the significance of torsion in the overall response. The research was also intended to study the effect of joint opening on the overall response of the bridge. In addition, this research aims at proposing a formula to estimate the failure load of EPS bridge girders under combined loading, since no design code provides a formula to estimate the load capacity of EPS bridges under such loading condition. The scope of this study was limited to determining deformation characteristics, strain variation, onset point of nonlinearity load, failure load and failure mechanism. The effect of different parameters studied include joint type (flat and with shear key) and tendon layout (harp and straight). There were three different load cases: without torsion, and with torsion imposed by different load eccentricities. To achieve these objectives, 12 specimens of externally prestressed segmented box bridge girders were tested. In addition, Finite Element (FE) analysis was conducted on a some of these girders using ANSYS finite element package. Three different types of elements (cube element, interface element and link element) were used in the FE analyses. Both geometric and contact nonlinearities were incorporated. The result of adopted Finite Element analysis was verified twice, once with the result of real bridge (in Bangkok), and another with the results of adopted experiments. So, the result of FE shown that the FE modelling can be used to simulated. This research was conducted for a better understanding of the behaviour of externally prestressed segmented bridges under combined loading. The results indicated that torsion has a significant effect on EPS bridges. Torsion not only reduces the value of failure load but also affects the failure mechanism. It was concluded that the contact nonlinearity due to joint opening affected the behaviour of EPS bridges. Finally, aformula was proposed to estimate the failure load of EPS beams

Effect of torsion on externally prestressed segmental concrete bridge with shear key

Externally Prestressed Segmental (EPS) concrete box sections are widely used in the construction of bridge structures today. EPS concept has become an attractive tool for rehabilitation and strengthening of existing bridges which have insufficient strength and/or excessive deflection and cracking. Problem statement: EPS bridges are affected by combined stresses (bending, shear, normal, and torsional) at the joint interface between the segments. However, very limited researchers studied this type of bridges under combined stresses. Approach: This paper presented an experimental investigation of the structural behaviour of EPS bridge with shear key under torsion. Four beams were tested, each containing three segments that were presetressed using two external tendons. A parametric study of two different external tendon layouts as well as different levels of torsional force applied by different load eccentricities was conducted. Results: The effect of torsion was evaluated in terms of vertical deflections, concrete and tendon strains, failure loads and failure mechanisms. It was concluded that torsion has a significant effect in the structural behaviour of external prestressed segmental box girder beams. Torsion not only alters failure load of the beam but also changes the type of failure mechanism. It was also investigated that harp tendon layout results in better structural behaviour in term of deflection and tendon strain as compared with the straight tendon. Recommendations: It recommended including the effect of joint (flat and shear key) type as well as the effect of tendon layout under torsion to obtain comprehensive behavior of EPS bridge