الملخص الإنجليزي
Lightweight aggregate concrete (LWAC) has received a lot of attention in the construction
sector due to its distinct qualities and benefits. Moreover, the addition of fiber to the
LWAC mix can enhance its mechanical properties, and the use of fiber-reinforced LWAC
is increasing in the construction sector. This type of concrete is used in bridges, floor slabs
in high-rise buildings, off-shore structures, highways, pavements and airport runways. In
these types of structures, flexural stress is critical, so it is important to investigate the
fatigue effect on this type of concrete structures that use this LWAC at various stress
levels. When compared to normal concrete, lightweight aggregate concrete can
significantly reduce self-weight in engineering structures. As per limited information in
the literature, the fatigue performance of LWAC is not the same as normal-weight
concrete. Therefore, it is important to conduct more studies on the fatigue performance of
LWAC. This thesis investigates the flexural fatigue strength and fatigue life distribution
of plain and fiber-reinforced lightweight aggregate concrete (LWAC) under various stress
levels. The flexural fatigue test data for plain and fiber reinforced LWC is collected from
literature. The fatigue performance of different types of LWAC was evaluated using
conventional Wöhler fatigue equation and power relations (double logarithmic fatigue
equations). The effect of different types of fibers (hook-ended fiber, twisted fiber,
polypropylene fiber and mix fibers) on the fatigue performance was also evaluated.
Probabilistic fatigue analysis was conducted on the collected fatigue test data to evaluate
the fatigue performance for different failure probabilities. The analysis used two parameter Weibull distribution (2PWD) and three-parameter Weibull distribution
(3PWD) models. There are limited experimental studies conducted in this field for the
LWAC. Therefore, the analyzed data were collected from two different studies. The
results show that fiber reinforcing can significantly increase the fatigue resistance of
LWAC. Both plain and fiber-reinforced LWAC's fatigue life follows the Weibull
distribution, with shape and scale parameters that depend on the applied stress amplitude.
By taking into account failure probability, the double and single logarithmic fatigue
equations were developed to establish the fatigue life equation. It was found that the
3PWD represents the fatigue failure more accurately than the 2PWD because of its
nonlinear curve, which is the real case of fatigue failure. Moreover, the results of stress
level for two million cycles (N=2106
) obtained using 3PWD were better than those
obtained by 2PWD.
