Improving the concrete sections after removing intermediate support of RC continuous non-prismatic beam

An experimental study was conducted to investigate the performance of the 2-span continuous reinforced concrete beams of different section depth after removing the middle support by adding steel fibers or steel plates. The beams were loaded monotonically with two-point loads. One continuous beam and six simply supported beams of non-prismatic section were tested using two different content of steel fibers and three different locations of steel plates welded to the reinforcement. The test results reveal that using inclined steel plates at the region of changing of cross section thickness at the middle support increase the load capacity of the beam significantly up to 75% of the continuous beam capacity, and a significant warning before failure is shown. Adding steel fibers to the concrete has less influence on the capacity of the beam. The failure mode of the beams with no middle support is the same, but with different values of deflection. The inclined steel plate again is the most effective way to decrease the deflection because of the increased stiffness of the cross section. To achieve the same capacity of the continuous beam after removing the middle support, it is recommended to use horizontal steel plates welded to the reinforcement at the region of the middle support extended within one fourth the length of each span of different thickness to avoid the stress concentration resulted from the large deflection at that region

FLEXURAL BEHAVIOR OF REINFORCED LIGHTWEIGHT CONCRETE BEAMS MADE WITH ATTAPULGITE AND ALUMINUM WASTE

Lightweight concrete reduces the total dead load of structural elements and seismic loads significantly. This paper presents the production Attapulgite Lightweight aggregate concrete (ALWAC) and its effect on the flexural behavior of reinforced concrete beams. Attapulgite was treated with sodium hypochlorite of 6% concentration for 24 hours. The variable considered was the aluminum waste (AW), used as a fiber, of fraction (0, 0.5 and 1%) by concrete volume. Behavior was investigated in terms of cracking and ultimate load, load-deflection relationship, failure mode, crack patterns and flexural ductility. The mechanical properties of the ALWAC were studied. It was observed that, Attapulgite improves the mechanical properties of concrete when comparing the experimental value with theoretical ones for the reference mixture. AW has a disparate effect on the mechanical properties of ALWAC. The increase in the proportions of AW showed an increase in the cracking load and decrease in the ultimate load by 37.14% and 22.45 %, respectively, at AW of 1%. Experimental value of ultimate load in all beams was higher than the theoretical value (ACI simplified method). AW increases the deflection at the same magnitude of applied load, and reduces the number and propagation of the flexural cracks in beams. All beams exhibited a typical tension failure mode and failed in ductile manner

A Review on Numerical Analysis of RC Flat Slabs Exposed to Fire

This paper aims at presenting and discussing the numerical studies performed to estimate the mechanical and thermal behavior of RC flat slabs at elevated temperature and fire. The numerical analysis is carried out using finite element programs by developing models to simulate the performance of the buildings subjected to fire. The mechanical and thermal properties of the materials obtained from the experimental work are involved in the modeling that the outcomes will be more realistic. Many parameters related to fire resistance of the flat slabs have been studied and the finite element analysis results reveal that the width and thickness of the slab, the temperature gradient, the fire direction, the exposure duration and the thermal restraint are important factors that influence the vertical deflection, bending moment and force membrane of the flat slabs exposed to fire. However, the validation of the models is verified by comparing their results to the available experimental date. The finite element modeling contributes in saving cost and time consumed by experiments