Papers by Keyword: Beam

Abstract: The paper presents research focused on modeling of lightweight concrete beams combining reinforced and fiber concrete. The paper solves the selected case of the RC beam, which was experimentally tested. The advanced numerical model and calculation used for an experiment into account the non-linear behavior and collapse of the beam. For the experiment, a specific cross-section with an opening that relieves the beam is selected. Non-linear analysis in combination with the finite element method is used for numerical modeling. Specifically, 3D calculation model and fracture-plastic material for concrete are used.

Abstract: The main goal of bridge health monitoring is to show the condition of structure in real time mode with using special sensors, which can measure different characteristics, which can indicate about the changes in structure. One of the easier measured indicators what can be used is frequency of structure vibration. The diagnostic of the health condition of structure is dependent of correct evaluation of changes range of measured indicators. This paper presents the theoretical calculations to study the effect of cracking on the frequency response of typical reinforced concrete T type beams which has widespread in road bridges construction.

Abstract: The article is dedicated to the effect of different modulus of the material on the stress state of a beam of the variable rectangular cross section. The height of the beam varies linearly along its length. Formulas for calculating the maximum compressive and tensile stresses and determining the neutral line are obtained. The maximum tensile and compressive stresses are determined for the clamped and simply supported beams. The dependence of the maximum normal stress on the number of reinforcing bars located in the stretched zones is numerically investigated. The stress state of the beam is compared with and without consideration of the bimodularity of the material for simply supported and cantilever beams. It is shown that taking into account the bimodularity of the material significantly affects the maximum tensile and compressive stresses. The magnitude of the tensile stresses is increased by 30%; the magnitude of the compressive stresses is reduced by 21%. As a bimodular material, fibro foam concrete is considered in work.

Abstract: The article presents the derivation of the resolving equation for the calculation of lateral buckling of rectangular beams. When deriving the basic equation, the initial imperfections of the beam are taken into account, which are specified in the form of the eccentricity of the applied load, the initial deflection in the plane of least stiffness and the initial twist angle. The influence of initial imperfections on the process of beam stability loss is investigated.

Abstract: It is presented the study of the beam samples reinforced with metal armature, BFRP armature and beams with hybrid reinforcement using metal and BFRP armature. Half of the tested samples of beams were manufactured on concrete with river sand, as a fine aggregate. The others were made on concrete with fractionated fine wastes of Mining and Beneficiary complex (MBC) instead of the river sand. The tests were carried out by static loading of the scheme of a single-run free beam loaded in the thirds of gear. It was established that the beams reinforced with BFRP armature and the beams with hybrid reinforcement showed an increase of strength, about 40%, compared with the beams reinforced with metal reinforcement. The deflections of the beams reinforced with BFRP armature were 315% -331% higher than the deflections of the beams reinforced with metal reinforcement and 165% -205% higher than it is allowed by standards. The use of hybrid reinforcement allowed reducing their deflections in two times compared to the beams reinforced with BFRP armature. At a load level of 60% of the destructive, the deflections of beams with hybrid reinforcement BFRP and metal armature did not exceed the maximum permissible norm. When concrete samples manufactured, the substitution of the river sand with fine fractionated wastes from the Mining and Beneficiary complex (MBC) did not affect their durability and deformability (the difference between the values according to these indicators is within the statistical error).

Abstract: Experimental studies of the stress-strain state of reinforced concrete and fiber-reinforced concrete beams under short-term and long-term loads were carried out. The tests were carried out on three series of beams of different types - from ordinary concrete, steel fiber concrete and combined section, when the lower zone of the beam with a height of 0.5h is made of steel fiber concrete, and the upper one is made of ordinary concrete. During short-term loading, the load was applied in steps with a 10-minute exposure at each step to failure or to a predetermined level of a continuously acting load. In the interval between the steps, the process of cracking was tracked. After reaching a given level of loading, the load was fixed and maintained unchanged with a spring cassette for 300 days. Deformations were measured using strain gauges and dial gauges. Deflections and relative deformations of the extreme upper and extreme lower fibers for three types of beams are determined. It has been established that stabilization of deflections in beams from steel fiber concrete occurs much earlier (100 days) than in beams made of ordinary concrete (175 days). Studies have shown that the beams of ordinary concrete in the process of long-acting load lowered the carrying capacity by 5.5%. The bearing capacity of steel concrete beams, in contrast, increased by 7.6%.

Abstract: The previous Measurement of fracture toughness test by using bright indentation for precracked beam method (ASTM C1421) was found difficult to be carried out due to difficulty in precrack generation and measurement of the crack size. In this research single edge precrack V-notch beam (SEPVNB) is introduced as an alternative to solve the problem from previous standardized method. A real crack that can created with referred size is recognized as the best condition for fracture toughness test. The material prepared for this purpose was silicon nitride (Si₃N₄) produced by CeramTec (Plochingen, Germany) under the name SL200 B. It is a gas pressure sintered ceramic containing 3 wt.% Al₂O₃ and 3 wt.% Y₂O₃. The V Notch was prepared by using razor blade with diamond paste following ISO/FDIS 23146 standard preparation with more addition on precrack introduction. The precrack was introduced by so called opposite roller loading. The fracture toughness test was carried out by following procedure in ISO/FDIS 23146 . The result then was compared for validation with both single edge V-notch beam standard (ISO/FDIS 23146 ) and Surface crack in Flexure SCF (ASTM C 1421). The result of fracture toughness by using method that is introduce in this research is found 5.8270.275 MPa^1/2 which is close to the result of SCF (5.335 0.222 MPa^1/2). Meanwhile the value of fracture toughness by using V-notch beam is 4.9130.098 MPa^1/2

Abstract: The paper deals with the experimental study of the behaviour of large concrete beams reinforced with glass fibre reinforced polymer (GFRP) rebars exposed to high temperatures equivalent to fire load. The four-point bending test was carried out on the beams after cooling. This study provided values for the load bearing capacity of the beams.

Abstract: This paper applies the stochastic finite element method (SFEM) to perform the natural frequency analysis of functionally graded material (FGM). It is assumed that the elastic modulus and width of the FGM beam vary along the thickness and width directions following exponential functions. The stochastic eigenvalue problem is solved independently by first-order perturbation and Monte Carlo simulation (MCS) method through changing elastic modulus as spatial randomness. The results show that the first-order perturbation method based SFEM produces a very close value to MCS method.

Abstract: Ensuring effective operation of structures in zones of aggressive media is associated with the task of studying, obtaining and developing composites of increased chemical resistance, strength and crack resistance. Structures based on corrosion-resistant materials (particularly polymer concretes) play a large role in solving these problems. One of these polymer concretes is rubber concrete or abbreviated as rubcon. This article is devoted to the study of the resistance of the external load to rubber concrete beams of a T-section. As a result of the experiments carried out on three series of rubber concrete T-beams with a different amount of longitudinal reinforcement, quantitative characteristics of the strength and crack resistance of their normal sections were obtained.