Published online on January 2015.
Rajamoori Arun Kumar, B. Vamsi Krishna
Abstract: The concept of pre-stressed concrete appeared in the year 1888. In this present engineering technology, durable and sustainable bridges play an important role for the socio-economic development of the nation. Owners and designers have long recognized the low initial cost, low maintenance needs and long life expectancy of pre-stressed concrete bridges. This is reflected in the increasing market share of pre-stressed concrete, which has grown from zero in 1950 to more than 55 percent today. This growth continues very rapidly, not only for bridges in the short span range, but also for long spans with excessive length which, here therefore, has been nearly the exclusive domain of structural steel. Many bridge designers are surprised to learn that precast, pre-stressed concrete bridges are usually lower in first cost than all other types of bridges coupled with savings in maintenance, precast bridges offer maximum economy. The precast pre-stressed bridge system has offered two principal advantages: it is economical and it provides minimum downtime for construction.
Pre-stressing is the application of an initial load on the structure so as to enable the structure to counteract the stresses arising during its service period. In the present project, the behavior of pre-stressed concrete beams, how they will be stressed, the percentage of elongation, and the pressure applied to make beams pre-stressed will be thoroughly examined. This work presents a practical approach on a major bridge having 299 m span, 36 PSC Beams and 8 RCC Beams. The study focuses on PSC Beams, where the beam post-tensioning values, rate of elongation and behavior can be defined after stressing.
The main code followed in this course is IS: 1343 – 2012 entitled Code of Practice for Pre-stressed Concrete. It is published by the Bureau of Indian Standards. Some provisions of Code IS: 456 - 2000 entitled Code of Practice for Structural Concrete are also applicable to Pre-stressed Concrete.
International Journal of Bridge Engineering, Vol. 2, No. 3, 2014: pp. 1-14
Abstract: Kinematic interaction is well recognized as being the cause of the development of significant internal forces in the piles under seismic loading. Another aspect of kinematic interaction which is often overlooked is the modification of the effective foundation input motion. Both aspects are illustrated on a real project.
International Journal of Bridge Engineering, Vol. 2, No. 3, 2014: pp. 15-28
S. Varela, M. ‘Saiid’ Saiidi
Abstract: This paper presents results of experimental and analytical studies conducted on innovative bridge columns using superelastic Copper-Aluminum-Manganese (CuAlMn) SMA and ECC in the plastic hinge region. A quarter-scale column model using these advanced materials was designed and tested dynamically under near-fault ground motions on a shake table. Damage to the column model was limited to the plastic hinge region and did not compromise the column's lateral and vertical load-carrying capacity. The superelastic effect of SMA and self-confining properties of ECC allowed the column to exhibit high self-centering capabilities. A relatively simple analytical model that was implemented in OpenSees was able to match some of the key experimental results with good precision. Experimental and analytical results suggested that CuAlMn SMA and ECC used in the plastic hinge region of bridge columns in areas of high seismicity could be an alternative to keep bridges functional after strong earthquakes.
International Journal of Bridge Engineering, Vol. 2, No. 3, 2014: pp. 29-58
V. Papavasileiou, I. G. Raftoyiannis
Abstract: In this paper, a survey based on experimental data accompanied by a detailed study on the assessment of the carrying capacity of an old Bailey-type steel truss road-bridge that is still in service is presented. This task is achieved through field measurements under static and dynamic loads as well as experimental results based on the properties of the steel material. An analytical model has been employed to assess the carrying capacity of the bridge under seismic loads and wind loads according to the provisions of current regulations. Based on the experimental and analytical results presented herein, strengthening and maintenance measures have been proposed in order to ensure strength and carrying capacity of the bridge under the current requirements. Also, an estimation of the remaining life of the bridge against fatigue is presented taking into account the proposed strengthening measures.
International Journal of Bridge Engineering, Vol. 2, No. 3, 2014: pp. 59-66
N. Makris, M. Vassiliou
Abstract: This paper investigates the rocking response and stability analysis of an array of slender columns caped with a rigid beam which are vertically restrained. This simplified system describes models a rocking bridge. The nonlinear equation of motion is formulated in which the stiffness and the prestressing force of the tendons are treated separately. In this way, the post-uplift stiffness of the vertically restrained rocking bridge can be anywhere from negative to positive depending on the axial stiffness of the vertical tendons. The paper shows that the tendons are effective in suppressing the response of rocking bridges with small columns subjected to long period excitations. As the size of the columns, the frequency of the excitation or the weight of the cap-beam increases, the vertical tendons become immaterial.
International Journal of Bridge Engineering, Vol. 2, No. 3, 2014: pp. 67-75