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In this research, the effect of using steel fiber and polypropylene on the behavior of the lightweight self-compacting concrete (LWSCC) beams have been studied. Seven beams have been cast with different parameters and compared. Two ratios of coarse aggregate replacement with light-weight aggregate expanded clay (LECA) have been considered partially and full replacement (50% and 100%) in this study based on previous study. Also, a 1% volumetric ratio fiber reinforcement has been added to investigate its effect on the flexural performance of LWSCC. A reduction in the ultimate load capacity and stiffness have been observed for LWSCC beams compared with the control beam by about 19% and 24.8% for partial and full LECA replacement, respectively. The steel fiber enhanced the performance of LWSCC beams in terms of cracking formation, crack width, ultimate capacity and allow the beams to have more ductile behavior. The ultimate load for fibrous LWSCC has been increased by about 11% and 12% for partial and full LECA replacement compared to beams without fibers. Beams with polypropylene and steel fibers exhibit similar behavior to the beams with steel fiber only in term of load-vertical displacement curves. However, the difference in the ultimate load capacity were 4% and 5% for the partial and full LECA replacement, respectively.

This paper presented a strengthening technique for enhancement reinforced concrete (RC) slab-column connection behavior using steel plates and steel stiffeners. A bi-axial load was applied with an eccentricity of 150 mm in both x and z directions. Four specimens with dimensions of 1,600 × 1,600 × 100 mm were tested in this research. The steel plate dimensions were chosen to be 600 × 600 and 800 × 800 mm with 6 mm thickness. The steel stiffeners are used to support and enhance the steel plate that it is extended from column to the slab-column connection with different dimension. The results showed an improvement in the stiffness of slab and increasing in the ultimate capacity. Also, when the steel plates dimensions increased, the ultimate capacity and stiffness increased.

Different techniques were employed for the passage of different utilities through structural elements. The reduction of the overall building weight was the main concern that needs to be achieved, especially for a multistory building. It can be done with the eliminating of a suspended ceiling with a portion of the beam’s weight by taking the advantages of the hollow sections. In this study, an equivalent reinforcement to the traditional ribbed reinforcement was employed to fabricate a reinforced concrete (RC) beam with a hollow section along the length of the beam. A steel pipe was used based on the equivalent moment from section analysis. Two diameters were selected of steel pipes as an equivalent to the commercial reinforcement. A total of four RC beams were cast and tested, two of them with traditional reinforcement and the other with steel pipe reinforcement. The comparison showed a promising result in terms of ductility, cracking pattern, ultimate strength, and mode of failure compared to the reference beam. The peak loads for the specimens with steel pipe were 160.6 kN and 184 kN, while they were 192 kN and 203.5 kN for the beams with traditional reinforcement.

The impact of steel and polypropylene fibers on the performance of lightweight self-compacting concrete (LWSCC) beams was investigated in this study. Seven beams with various parameters were cast and tested. Partial (50%) and full (100%) replacement of coarse aggregate with lightweight aggregate expanded clay (LECA) were considered. In addition, a 1% volumetric ratio of steel or hybrid (steel and polypropylene) fiber was added to LWSCC beams to study their effect on the shear performance. The LWSCC beams had a decrease in ultimate load and stiffness of 23 and 30% for partial and full replacement, respectively when compared to normal weight beam. The addition of steel fiber improved the efficiency of LWSCC beams in terms of crack formation, failure mode, crack width, and ultimate load, as well as changed the failure mode from shear to flexure. The ultimate load for hybrid LWSCC was increased by around 6% for a partial replacement and 13% for full replacement as compared to beams without fibers. However, hybrid beams had a larger bearing capacity, little more cracks with smaller size, and ductile failure.