Open Journal of Civil Engineering, 2013, 3, 26-32
http://dx.doi.org/10.4236/ojce.2013.33B005 Published Online September 2013 (http://www.scirp.org/journal/ojce)
Copyright © 2013 SciRes. OJCE
Experiment al Behavior of Partially Prestressed High
Strength Concrete Beams
Shady H. Salem, Khalid M. Hilal, Tarek K. Hassan, Ahmed S. Essawy
Department of Structural Engineering, Faculty of Engineering, Ain Shams University, Cai ro, Egypt
Email: shady.salem@bue.edu.eg
Received July 2013
ABSTRACT
In the last few decades, prestressed concrete has been rapidly used in bridge engineering due to the enormous develop-
ment in the construction techniques and the increasing need for long span bridges. High strength concrete has been also
more widely spread than the past. It currently becomes more desirable as it has better mechanical properties and dura-
bility performance. Major defect of fully prestressed concrete is its low ductility; it may produce less alarming signs
than ordinary reinforced concrete via smaller deflection and limited cr acking. Therefore, partially prestressing is consi-
dered an intermediate design between the two extremes. So, combining high strength concrete with partial prestressing
will result in a considerable development in the use of prestressed concrete structures regarding the economical and
durability view points. This study presents the results of seven partially prestressed high strength concrete beams in
flexure. The tested beams are used to investigate the influence of concrete compressive strength, prestressing steel ratio
and flange width on the behavior of partially prestressed beams. The experimentally observed behaviors of all beams
were presented in terms of the cracking load, ultimate load, deflection, cracking behavior and failure modes.
Keywords: Partially Prestressed; High Strength Concrete Beams; Serviceability Behavio r; Failure Modes
1. Introduction
In the last few decades, prestressed concrete has been ra-
pidly used in many fields of structural engineering, espe-
cially in the field of bridge engineering due to the enor-
mous development in the construction techniques and the
increasing n eed for long span bridg es. Now more than 50
percent of bridges all over the world are constructed us-
ing prestressing techniques [1]. High strength concrete
has been also more widely spread than the past due to the
enormous development in the material technology and
the greater demand for high strength concrete which
leads to a better quality control for concrete [2]. There-
fore, it currently becomes more desirable due to its better
mechanical properties and durability performance.
Fully prestressed concrete may result in a less signifi-
cant camber at service load than the specified design one.
The camber can also increase due to creep of the con-
crete with respect to time [3]. Another major defect of
fully prestressed concrete is its low ductility, where it is
stiffer than the ordinary reinforced concrete so it may
produce less alarming signs than ordinary reinforced
concrete via smaller deflection and limited cracking [4].
Therefore, partially prestressing is considered an inter-
mediate design between the two extremes [3]. For these
reasons, partially prestressed became a desirable struc-
tural solution worldwide. High strength concrete was
also believed to have lower flexural ductility than ordi-
nary concrete. However, some researches had proved that
the ductility of the high strength concrete was still in-
creasing when flexural stresses were applied [5]. So,
combining high strength concrete with partial prestress-
ing will result in a considerable development in the use
of prestressed concrete structures regarding the econom-
ical and durability view points.
This paper presents an experimental investigation to
assess the behavior of partially prestressed high strength
concrete beams. The effects of various parameters have
been investigat ed. These parameters ar e the concrete com -
pressive strength, prestressing steel ratio and the concrete
flange width. In the remaining sections of this paper, the
experimental program will be thoroughly discussed. The
results will be enumerated and comparisons to highlight
behavior characteristics will be presented.
2. Experimental Program
2.1. Specimens’ Details
The experimental program was conducted on seven par-
tially prestressed concrete beams with total length of
4800 mm. The beams were simply supported with 4500
mm clear span and 150 mm projection at each end. All