الفهرس 
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Abstract
The evaluation of torsion investigations is based on the increasing demand for the creative design
of curved structural members; yet, they are limited concerning lightweight concrete beams.
Lightweight concrete has many and diverse utilizations, including multistory building frames and
floors, curtain walls and bridges. This study investigated the effect of fiber on torsional behavior
of lightweight concrete beam. Many variables were studied such as the dimensions of
lightweight concrete beams, compressive strength of lightweight concrete, fiber type, fiber
volume ratio, spacing between stirrups, diameter of stirrups and CFRP reinforcement. ANSYS is
widely used finite element analysis (FEA) software in the computer-aided engineering (CAE)
industry, which used in current investigation. It enables engineers and researchers to create
computer models of structures, machine components, or systems, and to define design criteria.
The addition of fiber was the best-investigated factor in this research. All examined types of
fibers enhance the mechanical qualities, serviceability, and torsional capacity of lightweight
concrete beams. The numerical results showed that the increment in fiber content resulted in
better torsional resistance of lightweight concrete beams. The effect of carbon fiber and steel
fiber is evident from the volume ratio 2%, which produced the highest ultimate torque
enhancement to 77.64% and 76 % respectively. A significant increase in torque was achieved
when the width was further increased by 33.33% resulting in a 65.70% increase in torque. Also a
high increase in torque was achieved when the depth was further increased by 57%, resulting in a
46.26% increase in torsional capacity. In addition, a rational approach is proposed to predict
ultimate torque to develop the torsion design of lightweight concrete beams.
Key words: lightweight concrete, torsion, finite element, concrete beams.