Investigation of the Stress-Strain State of a Steel Column Base Connection for Seismic Regions

Currently, the main type of connection between a steel column and a reinforced concrete foundation is a steel base, which is often economically unprofitable due to its size, number or diameter of anchor bolts. Not only in Armenia, but also in most countries, a steel base is the main type of connection between a steel column and a reinforced concrete foundation. The usage of other types of connections is associated with both new calculation methods and technological problems. The possibility of computation and design of the connection of a steel column with a reinforced concrete foundation in seismically active regions using shear studs is considered in this work, a reinforced concrete section with longitudinal reinforcement is used for this type of connection which ensures a smooth transfer of forces from the column to the foundation. Based on the example of the connection of a single-story industrial building column shows the change in the stress-strain state of the connection under axial force and bending moments for seismic regions. Not only the feature and construction technology of the connection considered in the work, but also proposes a calculation method with future possibility of its subsequent inclusion in the building codes of the Republic of Armenia.

EVALUATION OF FIRE RESISTANCE OF FIRE PROTECTED STEEL STRUCTURES BY CALCULATION AND EXPERIMENTAL METHOD

Based on the developed geometric, physical, computer and finite element model, the fire resistance of fire-resistant steel structures was evaluated by calculation and experimental method. The adequacy of the developed computational-experimental method for assessing the fire resistance of fire-resistant steel structures in assessing the fire resistance of a fire-resistant I-beam steel column was verified. The results of tests for fire resistance of steel columns with fire-retardant coating at standard temperature of the fire without the load applied to them (temperature in the furnace, temperature in certain places on the surface of fire-retardant steel columns, the behavior of the investigated fire-retardant coating). The analysis of tests on fire resistance of fire-resistant steel columns exposed to fire at standard temperature (temperature in the furnace, temperature in places of measurement of temperature on a surface of columns, behavior of a fire-retardant covering) is carried out. A computer model of the «steel column – reactive flame retardant coating» system has been built for numerical simulation of non-stationary heating of such a system. Simulation of non-stationary heating of the system «steel column – fire-retardant coating» in the software package FRIEND with the specified parameters (geometric model, thermal effects, initial and boundary conditions, properties of system materials). The reliability of the results of numerical modeling with real experimental data on the duration of fire exposure at the standard temperature of the fire to reach the critical temperature of steel. Based on the comparison of experimental results and numerical simulations, a conclusion is made about the adequacy of the developed model to the real processes that occur when heating fire-retardant steel columns without applying a load under fire conditions at standard fire temperature. The efficiency of the proposed calculation and experimental method for assessing the fire resistance of fire-resistant steel structures has been confirmed.

PIPE-CONCRETE CENTRALLY-LOADED SUB-COLUMN OF A STEEL COLUMN FOUNDATION

A new progressive solution is considered, which consists in improving the design and static calculation of the strength of the elements of the sub-column part of a pipe-concrete foundation, in simplifying the design of a sub-column made of structural concrete of increased and high strength and a thin-walled metal pipe, using it in the form of a permanent formwork as a working element of a composite structure, in reduction of labor intensity and terms of performance of works of the zero cycle. An algorithm is proposed for designing elements of a precast-monolithic reinforced concrete foundation for a column, including a pipe-concrete sub-column, its fl ange connection with a steel column from above and with a foundation slab from below. Thin-walled pipe metal is an economical casing for in-situ concrete.

Simple Hplc Method Development for the Estimation of Galantamine Hydrobromide in Extended-Release Formulation

For the determination of Galantamine Hydrobromide in bulk and produced extended formulation, a new sensitive and quick HPLC technique was developed and validated according to ICH guidelines. The HPLC analysis was carried out using a waters system with a Thermo Scientific C18 (steel column (5 µm, 250mm × 4.6 mm)) column and a mobile phase of 0.1M phosphate buffer: Acetonitrile (40:60V/V) pH adjusted to 4.5 with orthophosphoric acid, at a flow rate of 1.0 mL/min. The detection was done at a wavelength of 203 nm, and galantamine hydrobromide had a retention time of 8.0 minutes. Over the concentration range of 1-10 g/ml, the calibration plot revealed a linear relationship. The accuracy of the proposed method was determined by recovery studies and was found to be near to 100 and % RSD value was found less than 2. The repeatability testing for both standard and sample solutions showed that the method is precise within the acceptable limits. RSD % of the determination of precision was <2%. The proposed method showed excellent linearity, accuracy, precision, specificity, robustness and system suitability results within the acceptance criteria. In addition, Saturation solubility of Galantamine Hydrobromide was determined in different pH mediums and it was found that Galantamine Hydrobromide has pH-dependent solubility, freely soluble in alkaline pH, and insoluble in acidic pH.