Ultra High Strength Concrete Beams Research Articles

Numerical Analysis on Flexural Capacity of Prestressed Steel Reinforced Ultra-High Strength Concrete Beams

As a new type of composite structural system, the prestressed steel reinforced ultra-high strength concrete (PSRUHC) beam was applicable to large-span structures and those structures which must bearing heavy loading. But by now there is no mature calculation method for the beam with a good accuracy. So the experiment on eight post-tensioned bonded prestressed steel reinforced ultra-high strength concrete beams had been carried out to investigate the flexural performance of PSRUHC beams. Based on the test results, the flexural capacity of PSRUHC beams were analysed by the large general-purpose finite element program ANSYS. Compared the simulation results of cracking load, ultimate load, yielding load and load-displacement curve with the test results, it is proved that the numerical method is effective for analyzing flexural capacity of prestressed steel reinforced ultra-high strength concrete beams, which provides theoretical foundation for practical application of PSRUHC beam.

Evaluation of Fracture Parameters by Double-G, Double-K Models and Crack Extension Resistance for High Strength and Ultra High Strength Concrete Beams

This paper presents the advanced analytical methodologies such as Double- G and Double - K models for fracture analysis of concrete specimens made up of high strength concrete (HSC, HSC1) and ultra high strength concrete. Brief details about characterization and experimentation of HSC, HSC1 and UHSC have been provided. Double-G model is based on energy concept and couples the Griffith's brittle fracture theory with the bridging softening property of concrete. The double-K fracture model is based on stress intensity factor approach. Various fracture parameters such as cohesive fracture toughness (4), unstable fracture toughness (K-Ic(c)), unstable fracture toughness (K-Ic(un)) and initiation fracture toughness (K-Ic(ini)) have been evaluated based on linear elastic fracture mechanics and nonlinear fracture mechanics principles. Double-G and double-K method uses the secant compliance at the peak point of measured P-CMOD curves for determining the effective crack length. Bi-linear tension softening model has been employed to account for cohesive stresses ahead of the crack tip. From the studies, it is observed that the fracture parameters obtained by using double - G and double - K models are in good agreement with each other. Crack extension resistance has been estimated by using the fracture parameters obtained through double - K model. It is observed that the values of the crack extension resistance at the critical unstable point are almost equal to the values of the unstable fracture toughness K-Ic(un) of the materials. The computed fracture parameters will be useful for crack growth study, remaining life and residual strength evaluation of concrete structural components.

Fracture Analysis of High strength and Ultra high strength Concrete beams by using Finite Element Method

This paper presents the details of nonlinear finite element analysis (FEA) of three point bending specimens made up of high strength concrete (HSC, HSC1) and ultra high strength concrete (UHSC). Brief details about characterization and experimentation of HSC, HSC1 and UHSC have been provided. Cracking strength criterion has been used for simulation of crack propagation by conducting nonlinear FEA. The description about FEA using crack strength criterion has been outlined. Bi-linear tension softening relation has been used for modeling the cohesive stresses ahead of the crack tip. Numerical studies have been carried out on fracture analysis of three point bending specimens. It is observed from the studies that the computed values from FEA are in very good agreement with the corresponding experimental values. The computed values of stress vs crack width will be useful for evaluation of fracture energy, crack tip opening displacement and fracture toughness. Further, these values can also be used for crack growth study, remaining life assessment and residual strength evaluation of concrete structural components.

Flexural Strength of Ultra High Strength Concrete Beams Reinforced with Steel Fibers

The purpose of this paper is to examine the basic behavior of ultra high strength concrete beams reinforced with steel fibers. The experimental parameters included steel rebar ratio less than 0.02 and the method of placing ultra high performance concrete. The ultra high strength concrete did not use coarse aggregate and had a volumetric ratio of 2%. The experimental test results from static loading of the beams revealed the characteristics of flexural behavior of the steel fiber-reinforced ultra high strength concrete. Flexural behavior included cracking, failure pattern, deflection, ductility, and flexural strength measurements. The test results from this study provide more information to help establish a prediction model for the flexural strength and deflection of ultra high strength concrete beams under bending conditions.