Papers by Keyword: Moment-Curvature Relationship

Abstract: The design of concrete structures with embedded non-metallic composite reinforcement (FRP) is becoming more widespread. The behavior of statically determinate concrete structures reinforced by this durable material is already widely understood and known. Usage of glass and carbon fiber reinforcement is also included in the new generation of Eurocodes for concrete structures. However, in common practice, we also encounter statically indeterminate structures such as continuous beams or slabs. In the case of traditional steel reinforcement of continuous beams, it is possible to assume a certain redistribution of bending moments and to use the principle of linear elastic analysis with limited redistribution in design. According to ACI 440.1R-15 and the new generation of Eurocode a moment redistribution of internal forces on continuous beams or other statically indeterminate structures reinforced with FRP reinforcement should not be considered, given the lower material stiffness and linear elastic behavior up to failure. However, in reality, a redistribution of internal forces can occur. Based on a limited number of studies and experiments that have been carried out in this area globally, there is a premise that some degree of redistribution of bending moment may occur in FRP reinforced indeterminate structures. The objective of this work is to support this assumption through an analytical study of the behavior of a concrete cross-section reinforced with FRP bars, demonstrating its potential for internal force redistribution. The aim of this paper is to present the results of an analytical study capturing the behavior of a concrete cross-section reinforced with FRP, the determination of the deformation characteristics of such a section, and the possible application of the results to a two-span concrete beam. The main emphasis is placed on the stress-strain diagram of concrete and its influence on deformation characteristics, mainly moment-curvature relationship.

Abstract: In this investigation, it was planned to study the flexural and plastic hinge behaviour of reinforced concrete beams confined with GFRP wraps and polyolefin fiber addition in critical regions (plastic hinge zone) along with stirrup confinement. The variables are the number of layers and chopped/woven type of wrapping, which controls the behaviour of the GFRP, and the percentage of polyolefin addition. The programme consisted of casting and testing 20 rectangular reinforced concrete beams of the size of 150 mm × 230 mm × 2000 mm, under a symmetrical two point loading. During the casting of the beams, the middle one third 600mm of the beams were cast with polyolefin fibers concrete, of volume fractions 0.3%, 0.5%,0.7%,0.9% and 1.2%. After the curing of the beams, glass fiber mats along with polyester resin were wrapped over the beams in the plastic hinge zone (critical zone) for 600 mm length; i.e., 300 mm from the centre on each side. Polyolefin fiber addition to the lateral tie and GFRP confined beams has the advantage over the confinement by the lateral ties and FRP wrap in improving the performance under large deformations.

Abstract: In order to improve the lateral deformation capacity of the high strength concrete shear wall, partially confined end-zones are usually set in the both ends of the shear wall cross-section. According to the experimental results of 15 high strength concrete shear walls with flexural (flexural-shear) failure, the moment - curvature skeleton curve of this shear wall cross-section is simplified as four linear through cracking point, yield point, peak point and ultimate point. Based on the plane-section assumption, the bending moment and curvature expressions at cracking, yield, peak and ultimate state are derived. At the same time, the effect of partially confined end-zones on peak and ultimate moment-curvature are taken into account. The analysis results show that, the calculated values are in good consistent with the experimental data.

Abstract: Based on appropriate numerical constitutive model of lightweight aggregate concrete filled steel tubes (LCFST), layered method was adopted to predict the complete moment-curvature curves of LCFST composite section subjected to pure bending. A FORTRAN program for the moment-curvature curves was developed. Applying the layered method, the influences of the significant parameters, such as steel ratio, yield strength of steel and strength of lightweight aggregate concrete on the moment-curvature curves of the composite section subjected to pure bending were discussed. The practical composite flexural stiffness, ultimate moment and practical moment- curvature relationship of LCFST composite section were presented. The predicted results of both layered method and practical moment-curvature relationships of LCFST composite section are in good agreement with the test results from reference. Compared with the layered method, practical calculate method could remove the step of composite section layered and improve the calculation speed while achieving similar results.

Abstract: The responses of high-speed railway bridge subjected to seismic load were investigated by numerical simulation, the whole finite element model of the multi-span bridge simply supported bridge was set up, and natural vibration properties of structure were analyzed. According to theory of elasticity and elastic-plasticity, parametric study was conducted to assess the influences of different speeds, strong motion record, pier height and earthquake acceleration on the seismic capability of high-speed bridge subjected to different strength of the earthquake, the finite element soft ware and moment-curvature program were employed to calculate the earthquake responses of bridge. The calculation results show that, with the increase of train speed, pier height and earthquake intensity, the earthquake responses of bridge are increase in general, and the bottom of piers step into states of elastic-plasticity under high-level earthquake, elastic-plastic deformation is larger, the stirrup encryption measures should be carried out.

Abstract: Several parameters and corresponding performance of reinforced concrete column cross-sections of different shapes (square, rectangular, circular, T-shape, I-shape, cross-shape, L-shape and C-shape) under various loading conditions have been studied in order to determine the suitable and optimum cross-sections for strength and ductility. In each cross-section shape, parameters include compressive strength of concrete (f’c), tensile strength of steel (fy), steel ratio (As/Ag), and angle of bending. In order to demonstrate the behavior and performance of the sections in terms of strength and ductility, CSISectionBuilder software was used to define the stress-strain curve for concrete and steel and then compute the moment-curvature relationship for each section. Considering different sections, the number of parameters in every section and various loading conditions, a total of around 1,800 sections were analyzed. The comparison procedures started within each section shape, and then across different sections in order to determine the most suitable cross-section for strength and ductility. Results of the study are deemed very useful in the system selection and preliminary design of important structures such as buildings with complicated geometry and high architectural demand including bridge piers and hydraulic structures.