No abstract

Reinforced concrete L-shaped beams are frequently used in the precast concrete industry specially in bridges construction to support a series of deck beams. The spandrel acts as a hanger for the ledge part, hence hanging reinforcement is used in the spandrel for this action. It was supposed that the outer vertical stirrups' branches are the main hanging elements for the ledge part; however, adding internal vertical branches contribute in hanging the ledge part. The perception that the outer vertical stirrups' branches solely are the main hanging elements and the neglection of the effect of inner stirrups' branches in hanging action can become questionable as it leads to using a great amount of outer reinforcement which leads to nesting of this part and increasing the fabrication cost of the beam. Therefore, a need exists to evaluate the contribution of the inner stirrups with the hanging steel reinforcement. This study aims to numerically model the performance of ledge beams taking into consideration distribution and amount of inner stirrups reinforcement, eccentricity of acting load on the capacity and performance of ledge beam.

The post-tensioned (PT) reinforced beams can provide a fast construction advantage through precast and cast-in-situ structural elements. However, due to the excessive increase in load capacity, especially when it comes to girder of bridges, the strengthening using Fiber-reinforced polymer (FRP) might be a solution. Near-surface mounted (NSM) is one of the methods used in strengthening cases, especially in the case of non-degraded concrete cover. Furthermore, very few researchers visited this area experimentally, which consider cost-effective. In this paper, two finite element models using the Abaqus program validated experimental results for both Post-tension beam and strengthening of the beam using NSM separately as preliminary models for combining both systems. PT reinforced concrete beam subjected to four-point bending loading as well as reinforced concrete beam strengthened with NSM using FRP bars subjected to two-point bending loading examined and validated through a 3D non-linear finite element (FE) model to be compared by the experimental results. This FE model considered the non-linear constitutive properties of concrete, yielding of steel, and the bond between strand, concrete, and FRP bars at NSM. The models were targeting the strengthening of existing Post tension girder beams of existing bridges structures. These modeling results showed a reasonable agreement with the tested beam results in terms of failure modes, the load capacity, load-deflection curve, and cracking behavior.

The applications of post tensioned concrete have increased and have now been used in different regions of the world. There are only few studies which have studied the behavior of retrofitted prestressed concrete experimentally, with the major part of the studies focusing on retrofitted reinforced concrete. This research study is initiated by a desire to more fully investigate the response of it. This paper presents a parametric study established on a beam with T-sec with web width 700 mm and a height of 1800mm, the thickness of the flange is 150 mm, the width of beam flange is 1500mm with span 29.6m. The beam was simply supported and loaded uniformly. A total no. of 20 finite element 3D models was generated taking the all possible failure modes such as FRP rupture, concrete cover separation and concrete crushing in order to study percentage of prestressing steel (Wp) parameter. Finally, a comparison is done between ACI 440.2R-08 code and the finite element results for the ultimate failure load and the predicted failure mode 0

This paper presents the experimental results of the investigation of behavior of simply supported deep beams having layers of concrete of different grades (25 MPa and 50 MPa). The tested beams were loaded with one vertical load at mid span up to failure. All specimens were fabricated and tested at the laboratory of reinforced concrete of Faculty of Engineering, Ain Shams University. The experimental program is carried out using five simply supported deep beams having the same dimensions; specimens with an effective span of 1100 mm, width of 200 mm and a height of 1000 mm, specimens also have the same top, bottom, vertical, and horizontal reinforcement. The experimental studies showed that the failure of tested deep beams was mainly due to diagonal cracks. Casting concrete on different layers causes the first cracks appeared at earlier load than in beam with one grade of concrete. It was also found that the best flexural behavior of deep beams is obtained when the bottom layer is casted using high concrete compressive strength and gives results (deflection, and failure load) close to results of deep beam casted with high compressive strength.