This paper presents an experimental and numerical study on the lateral impact behavior of rubberized-fibrous concrete-filled steel tubular (CFST) columns. Four types of concrete were utilized in the experimental program in the infilled columns: normal concrete (NC), rubberized concrete (RuC), steel fiber concrete (SFC), and hybrid RuC-SFC. Twelve specimens were tested using drop-weight impact with fixed-sliding boundary conditions. Three different transverse impact energies were produced by applying two masses of the hammers dropped from two different heights. A high-speed camera was implemented to measure the mid-span deflection against time. A 3-D finite element model was presented and verified against the tested specimens and some other experimental work from the literature. Load-displacement curves, the impact force time history, impact energy absorption, and failure modes of the CFST columns under the lateral impact were fully analyzed. The present results showed that at, certain impact energies, the steel tubular suffered only from the plastic deformation, beyond which it started cracking depending on the type of filled concrete. The steel tubular filled with hybrid RuC-SFC showed the highest resistance to crack formation, followed by that filled with SFC, while those filled with NC showed the lowest resistance to crack formation. There is an agreement between the numerical and the experimental results.

This paper presents a review on rubberized concrete mixes and their properties such as strength, ductility, sound and water absorption, in addition to acid and sulphate resistance. Moreover, it discusses a review about using rubberized concrete in structural elements and its effect on ultimate compressive strength and ductility. Rubberized concrete mixes exhibit lower strength than ordinary concrete mixes. On the other hand, rubberized concrete has higher ductility and energy dissipation behaviour. Rubberized concrete with its lightweight showed a high resistance to freeze-thaw and sulphate and acid attacks in comparison with ordinary concrete. The most common structural member is Rubberized Concrete Filled Steel Tubes (RuCFST). In addition to the aforementioned merits of rubberized concrete, the confining effect of the steel tube recoups the reduction in concrete compressive strength caused by rubber inclusion. Limited researches concerned in strengthening and repairing of deficient Concrete Filled Steel Tubes (CFST) with different types of Fibre Reinforced Polymers (FRP). There is noticeable effect of using these FRP materials on RuCFST sections, ultimate strength and ductility

Externally post-tensioned tendons can cause an initial compressive stress in steel–concrete composite sections at the hogging moment region, and then a part of the tensile stress in the concrete flange can be relieved. This study presents a detailed finite element analysis of the nonlinear flexural response of continuous steel–concrete composite beams strengthened with externally post-tensioned tendons. The initial post-tensioning force is introduced as an initial strain in the truss element that used to simulate the external tendons. The accuracy of the finite element model is validated using existing experimental works. The effects of tendon eccentricity, longitudinal steel rebar ratio, and initial post-tensioning force on the beam behavior are explored. Furthermore, deterministic and stochastic shrinkage effects are carried out to obtain the long-term random responses of the strengthened beams as well as unstrengthened beams. However, the ultimate capacity of the strengthened beam increases only by 8%, the cracked moment redoubles, and an affirmative behavior over the unstrengthened beams is obtained. Also, a rapid decay in the long-term deformation of continuous steel–concrete composite beams is obtained at the early age while a linear decrease in the remaining part of the age occurs.