Two Methods for Determining Softening Relationships of Dam Concrete and Wet-Screened Concrete

Abstract

The direct tension tests and three-point bending notched beam tests were performed on dam concrete and wet-screened concrete specimens. Based on these two fracture tests, the softening relationships (σ – w curves) of dam concrete and wet-screened concrete were determined by employing direct tension test method and inverse analysis method respectively. The inverse analysis method based on cracking strength criterion was adopted in the analysis. The results showed that the obtained softening relationships by the DT test method were in good agreement with those by the inverse analysis. It was also found that the tensile strength as well as the fracture energy of dam concrete were smaller than those of wet-screened concrete, but the crack width at zero stress of dam concrete was greater than that of wet-screened concrete. It can be seen there may be a definite relation between the softening relationship of dam concrete and that of wet-screened concrete.

Combining Thermal Loading System with Acoustic Emission Technology to Acquire the Complete Stress-Deformation Response of Plain Concrete in Direct Tension

“…The complete load vs. deformation curve can be obtained through splicing the data recorded by the static acquisition system and the dynamic acquisition system, respectively, which is depicted in Figure 10 a. Assuming that the macro-cracks generated around the peak stress level, the post-peak strain could be revised by Equation (3) to eliminate the effect of elastic shrinkage in uncracked regions [ 2 ]. Consequently, the stress-strain curve can be transformed from the load vs. deformation curve (shown as Figure 10 b) where is the deformation of the measurement area, l is the length of the measurement area, is the nominal stress, is the peak stress and is the elastic modulus obtained by fitting the stress-strain data at the linear elastic stage.…”

“…The extremely short time of the unstable cracking process make it difficult to record the relevant data. At present, the common test methods to study the tensile softening response of concrete can be mainly classified into three categories: direct tension tests (DTTs) [ 1 , 2 , 3 , 4 , 5 ]; three-point bending beam tests (TPBBTs) [ 2 , 6 , 7 ]; and splitting tensile tests (STTs) [ 8 , 9 , 10 , 11 ]. Compared with the TPBBT and the STT, the softening response of specimens in the DTT is more difficult to observe.…”

“…This is because both the TPBBT and the STT are indirect tensile tests, in which stress distribution is more complex and keeps changing with the increasing damage. Moreover, in the TPBBT and the STT, the complete tensile stress-strain curves are obtained through the inverse analysis method [ 2 ] and theoretical analysis model [ 10 ], respectively, which may cause the reliability of the test results to be affected by the relevant parameters.…”

“…Since Evans and Marathe [ 12 ] observed the softening response of plain concrete in a DTT and obtained the corresponding complete tensile stress-strain curve, there has been an outpouring of literature focused on the tensile properties of various concrete materials [ 2 , 13 ], the effects of different test methods [ 3 , 4 , 5 , 14 , 15 , 16 ] and the simulations of the fracture process [ 17 , 18 , 19 ]. Generally, the DTTs are conducted on a tensile test machine (TTM) with high stiffness [ 3 , 14 ], or a special electronic servo-controlled TTM with a fast response time [ 4 , 20 , 21 ].…”

Coupled Hydraulic System for Tensile Testing in Compression-only Machines

“…The resulting stress-crack opening curves for UHPC are approximated by an approach presented in multiple references [21,22]. This method estimates the crack-opening width by subtracting residual deformation at peak stress and the elastic deformation at any point on the stressdisplacement curve outside the fracture zone from the specific deformation reading.…”