An Experimental Study on Rehabilitation of RC Beam by Stitching Method

The current work presents an experimental study on rehabilitation of RC beam by stitching method. For the study, a total of Twenty-Four RC beams were casted and cured for 28 days. Among the beams casted, three is control beam. Under two point loading, the control beam was tested for ultimate failure load and remaining twenty one beams were loaded for 75% of the ultimate failure load. The damaged beams were then rehabilitated by Stitching method using two different patterns. The rehabilitated beams were tested for ultimate failure load and the results are compared with control beam and the effectiveness of the rehabilitation is determined. From the result it is observed that as the diameter is gone increasing the flexural strength of the beam is gone increasing. As the depth of insertion of the bar inside the beam is gone increasing the flexural strength of the beam is gone increasing. It is concluded from this study that stitching methods is effective to restore the flexure capacity of damaged beams. Keywords: Rehabilitation, Reinforced Concrete Beam, Stitching Method

Ductility and Durability Enhancement of Concrete EPS by New Reinforcement Arrangements and PP FRC Utilization

A majority of precast concrete electric pole structures (EPSs) consist of prestressed concrete (PSC) and reinforced concrete (RC) hybrid members with high slenderness ratios. Currently, large prestressing (PS) forces are being applied to EPSs to carry heavier weights of electric transformer machineries and to reduce deflection by increasing structural stiffness. Moreover, when EPSs are exposed to an outdoor environment year-round, their durability decreases. Therefore, this study’s objectives are to transform the failure behavior of EPSs from brittle to ductile by varying the number of PS tendons and steel rebars, and to improve the EPSs’ ductility and durability by using short polypropylene (PP) fiber-reinforced concrete to control crack formation and propagation. Six different types of EPS specimens were manufactured and tested to evaluate their maximum flexure capacity and to verify their ductility behavior. The results showed that the modified EPSs displayed ductile failure behavior while either maintaining their original flexural strength capacity or improving it compared with the current EPSs sold on the market.

Application of Large Prestress Strands in Precast/Prestressed Concrete Bridges

The objective of this research is to investigate the advantage of using large-diameter 0.7-inch (18 mm) strands in pretention applications. Large-diameter strands are advantageous in bridge construction due to the increased girders capacity required to sustain exponential increase in vehicle numbers, sizes, and weights. In this research, flexure capacity of girders fabricated using 0.7-inch (18 mm) diameter strands will be calculated and compared to bridge capacities constructed using smaller strands. Finally, two similar bridge sections will be designed using 0.6-inch (15 mm) and 0.7-inch (18 mm) diameter strands to quantify the structural advantages of increased strand diameter. The research findings showed that a smaller number of girders is required for bridge construction when larger strands are used. Four girders are required to design the bridge panel using high performance concrete and large diameter strands, as compared to 6 girders required when regular concrete mix designs and normal size strands are used. The advantages of large strands and high-performance concrete mixes include expedited construction, reduced project dead loads, and reduced demand for labor and equipment. Thus, large strands can partially contribute to the improvement of bridge conditions, minimize construction cost, and increase construction site safety.

EVALUATIONS OF FLEXURAL CAPACITY IMPROVEMENT METHOD FOR RC PIERS AND CISS FOUNDATION CONNECTIONS IN BRIDGES

Recently, cast-in-steel shell (CISS) pile has been used as the foundation of bridges and a pier is directly connected to the pile. In this case, plastic hinge is generally formed at the connection between the CISS pile and reinforced concrete pier. To increase the flexural capacity of such structure, a proper improvement method is necessary for the connection. In this study, a steel tube, a steel pipe that has 270mm diameter with 4.5mm thickness, has been used to enhance flexural capacity of the connection and the effect by the such method was evaluated through cyclic compression-bending test. From the test results, it can be found that the flexure capacity is considerably increased by applying the steel tube at the connection when it was compared to a general reinforced concrete (RC) pier with 10% larger diameter cross-section.

Assessment of the Flexural Behavior of Concrete Block Masonry Beams

This paper focus on the experimental flexural behavior of masonry beams. In the sequence of the development of a novel structural solution for reinforced masonry walls at University of Minho, different possibilities for the construction of lintels with concrete block masonry have been tested. Reinforced concrete beams with three and two hollow cell concrete blocks and with different reinforcement ratios have been built and tested in a four point loading test configuration. It was clear that horizontal bed joint reinforcement increased the ultimate flexure capacity as well as the ultimate deflection, leading to much more ductile responses. Moreover, it was also clear that a more deep analysis should be made regarding the role of the compressive strength of masonry in the parallel direction to the bed joints on the global behavior of the masonry beams.