Following the previous analytical studies performed with ATENA software for a series of RC moment resisting frame models, it were used in the pre-processing stage the stress-strain relation laws for concrete and steel reinforcement. These mathematical and graphical relations represent a necessity in the current conditions of numerical analysis and imply a correct knowledge of the deformation mode of the „reinforced concrete” which is a composite material. Thus, it is desired through this research paper the theoretical exposition of: equivalent uniaxial law for concrete, biaxial compressive failure and tensile failure consideration laws for concrete, bilinear with hardening law for steel reinforcement, cycling steel reinforcement model and steel reinforcement bond model. Finally, it will be possible to validate the correctness of the analytical RC frame systems through the experimental results of the optimal RC frame model after seismic platform testing.
Zeolites can either occur naturally, in volcanic rock formations, or can be synthesized in the laboratory. When ground to a fine powder, they can be successfully used as supplementary cementitious material because of their chemical composition consisting in large amounts of SiO2 and Al2O3 that react with Ca(OH)2 to produce C-S-H gels. The composition of synthetic zeolites can be tailored to suit the purpose of their use in cementbased mortar and concrete and they can be produced from a variety of sources and at much lower energy costs than Portland cement. The use of zeolites in cement-based construction materials has led to improved mechanical and durability properties. The paper presents the preliminary results on using zeolites as supplementary cementitious material in mortar and the influence of elevated temperatures on the early age mechanical properties. The main parameters of the research were the replacement percentage of Portland cement by zeolite powder (10% and 20%, by volume of cement) as well as different temperature values (100�C, 150�C and 200�C). Standard 40?40?160 mm mortar prisms were cast and cured in water for 14 days before being subjected to elevated temperatures in an oven for 4 hours then left to gradually cool until they reached the room temperature. A control mix consisting of rapid hardening Portland cement was also cast and served as reference in the experimental program. The obtained results are presented in terms of density of the mortar mix, flexural and compressive strength.
Computer simulations are challenging in terms of modeling the appropriate behavior of brick masonry structures. These numerical simulations are becoming increasingly difficult due to several design code requirements considered for the technical assessment of brick masonry structures for rehabilitation. In Romania, many brick masonry structures have withstood powerful earthquakes during their lifetime and require rehabilitation works. This paper aims to further assess various simulation challenges regarding the boundary conditions of spandrels and masonry structural behavior. This paper presents a comparative numerical study of two different spandrel-piers scenarios: one considers the link between them as unaffected, and the other attempts to simulate the occurrence of damage by replacing the spandrel’s presence in the initial structure. The proposed model follows the “strong pier–weak spandrel model” and is aimed at practicing engineers. Models are computed with ordinary design software such as Robot Structural Analysis with 2D shells finite elements for masonry walls and, in a more complex manner, software such as Ansys with 3D solid finite elements. Time history analyses are carried out for three distinct accelerograms recorded in Romania. A comparison of the results acquired from these two models is presented and discussed. The purpose of this research is to highlight the importance of proper modeling of unreinforced brick masonry structures to optimize operational and maintenance practices.
Cold-formed steel structures represent a suitable alternative to classical, by now, structural solutions considering the recycling/reuse tendency worldwide as part of the circular economy paradigm. The paper presents a new design approach for CFS profile joints to accurately predict their realistic behavior, based on experimental and numerical investigation of two types of connectors frequently used in the construction industry for manufacturing joints made of CFS profiles: steel-steel pop-rivets (SSPR) and self-tapping screws (STS). The experiments carried out in the case of T-joints subjected to tensile forces tested both solutions. Another significant parameter of the research was the thickness of the steel sheet used to make the CFS profiles. A number of 20 specimens of T-joints made of Cold-Formed Steel (CFS) profiles in total were tested. These consist of five specimens for each of two types of steel sheet thicknesses. The results are relevant for designers because they provide relevant data concerning the limited axial rigidity of T-joints, which are an important instrument in numerical models for achieving the optimum design of the structural system in terms of strength and overall rigidity. Experimental tests calibrate the numerical model that accounts for the axial stiffness of the hinged joints between the CFS profiles. The main parameters of the research are the thickness of the steel sheet and the connector type. The calibrated numerical model used in a case study highlights the advantages of the new approach compared to the classical design procedure based on a conventional hinged connection. Based on the results, the conclusion is that, besides the geometry of the joint and the connector type, the joint stiffness plays a crucial role in the overall behavior of the structural system and should be accounted for in the design process.
One of the most destructive natural phenomena is the earthquake. These events destroy lives, goods and disrupt human activities. For this reason the anti-seismic protection of buildings is a very important and of interest subject in Civil Engineering. In the case of structures with a low seismic energy dissipation capacity (for example steel frame structures with Slimdek composite floors), this problem becomes more complicated due to the requirement of dampers. In this paper an experimental study is presented regarding an innovative yielding metallic energy dissipation device, proposed by the author. An experiment is carried out on a shake table. By studying the results from the experiments and from the previous carried out numerical analysis we can conclude that this device provides a high anti-seismic protection for this type of structures.
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