Experimental and Numerical Analysis of High-Strength Concrete Beams Including Steel Fibers and Large-Particle Recycled Coarse Aggregates

In order to study the performances of high-strength concrete beams including steel fibers and large-particle recycled aggregates,four different beams have been designed,tested experimentally and simulated numerically.As varying parameters,the replacement rates of recycled coarse aggregates and CFRP(carbon fiber reinforced polymer)sheets have been considered.The failure mode of these beams,related load deflection curves,stirrup strain and shear capacity have been determined through monotonic loading tests.The simulations have been conducted using the ABAQUS finite element software.The results show that the shear failure mode of recycled concrete beams is similar to that of ordinary concrete beams.The shear carrying capacity of high-strength concrete beams including steel fibers and large-particle recycled coarse aggregates grows with an increase in the replacement rate of recycled coarse aggregates.Reinforcement with CFRP sheets can significantly improve the beam’s shear carrying capacity and overall resistance to deformation.

Behavior of steel fiber-reinforced high-strength concrete at medium strain rate

Impact compression experiments for the steel fiber-reinforced high-strength concrete(SFRHSC)at medium strain rate were conducted using the split Hopkinson press bar(SHPB)testing method.The volume fractions of steel fibers of SFRHSC were between 0 and 3%.The experimental results showed that,when the strain rate increased from threshold value to 90 s^(-1),the maximum stress of SFRHSC increased about 30%,the elastic modulus of SFRHSC increased about 50%,and the increase in the peak strain of SFRHSC was 2-3 times of that in the matrix specimen.The strength and toughness of the matrix were improved remarkably because of the superposition effect of the aggregate high-strength matrix and steel fiber high-strength matrix.As a result,under impact loading,cracks developed in the SFRHSC specimen,but the overall shape of the specimen remained virtually unchanged.However,under similar impact loading,the matrix specimens were almost broken into small pieces.

Flexural behavior of high-strength,steel-reinforced,and prestressed concrete beams

To study the flexural behavior of prestressed concrete beams with high-strength steel reinforcement and high-strength concrete and improve the crack width calculation method for flexural components with such reinforcement and concrete,12 specimens were tested under static loading.The failure modes,flexural strength,ductility,and crack width of the specimens were analyzed.The results show that the failure mode of the test beams was similar to that of the beams with normal reinforced concrete.A brittle failure did not occur in the specimens.To further understand the working mechanism,the results of other experimental studies were collected and discussed.The results show that the normalized reinforcement ratio has a greater effect on the ductility than the concrete strength.The cracking-and peak-moment formulas in the code for the design of concrete(GB 50010-2010)applied to the beams were both found to be acceptable.However,the calculation results of the maximum crack width following GB 50010-2010 and EN 1992-1-1:2004 were considerably conservative.In the context of GB 50010-2010,a revised formula for the crack width is proposed with modifications to two major factors:the average crack spacing and an amplification coefficient of the maximum crack width to the average spacing.The mean value of the ratio of the maximum crack width among the 12 test results and the relative calculation results from the revised formula is 1.017,which is better than the calculation result from GB 50010-2010.Therefore,the new formula calculates the crack width more accurately in high-strength concrete and high-strength steel reinforcement members.Finally,finite element models were established using ADINA software and validated based on the test results.This study provides an important reference for the development of high-strength concrete and highstrength steel reinforcement structures.

Calculation methods of the crack width and deformation for concrete beams with high-strength steel bars

Three groups of concrete beams reinforced with high-strength steel bars were tested,and the crack width and deformation of the specimens were observed and studied.To facilitate the predictions,two simplified formulations according to a theory developed by the first author were proposed.The advantages of the formulations were verified by the test data and compared with several formulas in different codes.

MECHANICAL BEHAVIOUR AND INTERFACIAL PERFORMANCE OF STEEL FIBER REINFORCED SILICA FUME HIGHSTRENGTH CONCRETE

In this paper, the flexural, split tensile, impact and fatigue performance of steel fiberreinforced silica fume high-strength concrete (SIFUMHSC) under static and dynamic loadsare studied. The effect of the amount of silica fume on its performance, the strengtheningeffects of silica fume particle artd steel fiber afld their composite effect are discussed. Testresults indicate to a full extent that different amounts of silica fume substituting for cementcan remarkably improve the static and dynamic mechanical behaviour of steel fiberr einforcedSIFUMHSC with other conditions unchanged and that the main reason for the change is thatthe addition of silica fume brings about a double interfacial strengthening effect of fiber-cement matrix and aggregate-cement matrix, thus improving the structure and characteristicsof the interface. When the addition of silica fume is adequate, the H_v-d, I_a-d and CHAS--dcurves tend to be horizontal, with differences disappearing between the interfacial layer andmatrix, so that the size and number of crack sources in the interfacial zone and the wholematrix become smaller and less, and strengthening effects are better deve1oped. This is thekey to the desired performance of steel fiber reinforced SIFUMHSC.