Despite the great use of concrete, tensile strength and low flexibility and brittleness are its weaknesses. Many solutions have been provided to eliminate the mentioned defects. In order to increase the flexibility of concrete in previous studies, crushed rubber tire particles have been added to concrete. Recycling car tires helps the environment and makes concrete much more flexible than regular concrete. In this research, silicone rubber has been replaced by 0%, 2%, 4%, 8%, 12.5%, 25%, and 50% of mineral aggregates. This rubber was initially in liquid form, which, after mixing with ordinary concrete, dispersed into the concrete texture and formed a uniform mixture, and this liquid rubber became a flexible solid after 24 hours. Concrete containing silicone rubber is a new composite with new properties, and in this research, it is called Hybrid Silicone Rubber Concrete (HSRC). Also, to evaluate the effect of aggregate size in making experimental specimens, two coarse to fine aggregate ratios of G/S = 0.7, 1.1 were considered. Flexural strength tests were performed on hardened concrete beam specimens. The results showed that, with increasing the amount of silicone rubber in concrete, flexural strength decreased and this percentage of strength reduction was compared with the percentage of reduction in compression and splitting tensile strength. It was found that the reduction of flexural strength was less than compression and splitting tensile strength. Larger deformation was observed during all tests when the concentration of silicone rubber increased. It was observed that the higher the amount of silicone rubber in the specimens, the less noise and the less separation of aggregates with which the failure of the specimens was associated.
As the experts who have taken for granted the merits of utilizing the concrete as the most common material in the structural industry, there is a need to take affirmative steps to enhance the concrete’s weaknesses such as the low ductility and energy absorption capacity. One possible way to improve the mechanical properties of concrete is to add liquid silicone rubber to the concrete. Silicone rubber is an elastomer (rubber-like material) composed of liquid rubber polymer and its hardener which is widely used in voltage line insulators, automotive applications, and medical devices. In order to increase the ductility and energy absorption of concrete, the liquid silicone rubber replaced a portion of mineral aggregates in concrete. HSRC (hybrid silicone rubber concrete) is a mixture of liquid silicone rubber with fresh concrete that liquid silicone rubber after 24 hours becomes a flexible solid rubber with low strength. In this paper, liquid silicone rubber was used to replace 0%, 2%, 4%, 8%, 12.5%, 25%, and 50% of the total mineral aggregate’s volume in concrete. Standard specimens were fabricated and tested. The fresh HSRC exhibited acceptable workability and lower unit weight compared to ordinary plain concrete. The uniaxial compressive strain-control test was conducted on the hardened HSRC specimens to obtain the complete stress-strain curve. The results showed that, with the increase of liquid silicone rubber in concrete, the amount of compressive strength, splitting tensile stress, and elastic modulus decreased. It was also observed that the percentage of reduction in compressive strength was greater than the percentage of reduction in tensile strength. Increasing silicone rubber concentration in HSRC changes the brittle mode of failure to ductile that demonstrated using nonlinearity indices. Unlike plain concrete, the failure state in HSRC occurs gently and uniformly and does not cause so much separation in the specimens. Larger deformation and higher toughness indices were obtained, when the silicone rubber concentration was increased.
Damage to structures with the concept of inelastic behavior and consequently hysteresis energy is very close. Therefore, it can be said that hysteresis energy at these levels can be a significant criterion for designing or controlling the structure. In this research, the first three steel frames of 4, 8, and 12 floors with the medium bending frame system have been designed with the statically equivalent method according to valid international regulations; then, all frames have been subjected to nonlinear dynamic analysis by seven accelerometers. The purpose of this study is to investigate the distribution of damage, energy, relative displacement, roof displacement, and base shear in the studied frames. In the following, the necessity of using the retrofitting method to reduce the relative displacement is described based on the regulations. Then, viscoelastic dampers are used to strengthen and reduce damage in the studied frames in the face of distant field records. The obtained results indicate that despite the uniform distribution of resistance in the height of the floors, the hysteresis energy distribution and damage diagrams do not follow this distribution and other parameters such as hysteresis energy, which play a major role in structural members’ damage, should be included in the design process. In this research, viscoelastic dampers have been used for retrofitting. The results show that this type of damper shows good performance in reducing damage under earthquakes in the remote area.
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