out using the large static-dynamic triaxial test system in the State K - PDF document

out using the large static-dynamic triax
out using the large static-dynamic triaxial test system in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The stress ratios are 0, 0.1, 0.25, 0.50, and 0.75. The temperatures are 20°C, 200°C, 300°C, 500°C, 600°C. The mechanical behavior of concrete is detrimental to the concrete structure because the concrete’s capability to resist cracking decreases [1]. When concrete more than at normal temperatures [2–3]. Currently, there ture [4–6]. However, most of these studies are concentrated on, are under biaxial tension-compression state. Therefore, In this study, biaxial tensile-compressive experiments criterion is derived from the experimental results. This study 2 Experimental investigationThere were 117 pieces of concrete samples used in the test, of 100 mm100 mm100 mm in size. The cement was sourced from a Dalian cement factory. The coarse aggregate is crushed limestone with maximum size of 20 mm, and the fine aggregate is medium sand. The measured prism compres-sive strength is 32.5 MPa, and the tensile strength is 3.14 MPa. The mixture’s proportion of weights is cement : sand : stone : 383 : 663 :1154 : 193.2.1 Raising temperature testelectric furnace which is made in Harbin northern electric fur-nace fac

tory, the electric furnace can achieve h
tory, the electric furnace can achieve high tempera-tures up to 950°C, with the rated power of 75 kW and rated frequency of 50 Hz. The designated test temperatures are 200°C, 300°C 500°C and 600°C respectively, and samples are heated with the rate of 100–200°C/h. After being heated Front. Archit. Civ. Eng. China 2007, 1(1): 94–98DOI 10.1007/s11709-007-0009-zRESEARCH ARTICLESONG Yupu, ZHANG Zhong, QING Likun, YU Changjiang© Higher Education Press and Springer-Verlag 2007Translated from Journal Dalian University of Technologyechnology译自: 大连理工大学学报]SONG Yupu (), ZHANG Zhong, QING Likun, YU ChangjiangState Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China95the furnace for 6 h at this temperature and then are taken out. After cooled down in air for 24 h, the sample is used for the 2.2 Sample disposalTo decrease the friction between the concrete sample glycerine in-between are used. This not only decreases the 2.3 Loading equipment and test methodLoading tests are carried out on a large-scale dynamic-static of Coastal and Offshore Engineering in Dalian University of Technology. The system is composed of a loading system, collecting system [7]. The compressive load is exerted by the

axis in the horizontal direction, and th
axis in the horizontal direction, and the axis in axis of the machine through global hinge is closed of the concrete sample. The compressive loads of 1 kN in the and axis directions are exerted and, at the same time, the then the compressive load is decreased to 0 kN. variable displacement transducers (LVDTs), which are placed on loading plates. To avoid the deviation which might occur in the loading process, the LVDTs are placed at each side of and represent the principal stress respectively. The 3 Experimental results and analysis3.1 Stress-strain curvesabrupt fracture due to the tensile stress. The stress-strain Figs. 1–3, respectively. Stress-strain curves of the stress radio 0.1: Stress-strain curves of the stress ratio 0.2: Stress-strain curves of the stress ratio 0.25:temperature increase. With increasing temperature, the strains and corresponding to the peak stress decreased, the stress stress peak are shown in Tables 1 and 2.From Table 1, it is found that the tensile strength increases 0.1 is 0.57 MPa, which is 47.5 of uniaxial tensile 0.25, the corresponding values are 0.81 MPa , respectively. In contrast, the absolute value of stress state. This indicates that under biaxial tension-stress is large. is 0.74 MPa, namely, only 36Tabl

e 2 indicates that under biaxial tensio
e 2 indicates that under biaxial tension-compression, method is used. However, it is obvious that the change of the decreases with the drop of stress ratio, and reaches the minimum value under uniaxial tensile stress state. When 0.25, the change extent of the strain is larger than 0.25, the value of is nearly equal ture. The absolute value of the principal compressive strain Secondly, for the same stress ratio, the absolute values of decrease with temperature increase. For exam- are only 36.8 of the corresponding values of normal temperature at 600°C, respectively, but at 300°C, the values of and are and 78.9 of that of normal temperature, respectively. 3.2 Relationship between tensile strength and stress ratio Figure 4 shows the change in the tensile strength with the Table 1 Experimental results of tensile and compressive stress at the stress peak under biaxial tension-compression state (MPa) 20°C 200°C 300°C 500°C 600°C 20°C 200°C 300°C 500°C 600°C0 0 0 0 0 0 1 1.55 1.24 1.13 0.81 0.57 11.3 1 2.04 1.52 1.48 0.98 0.74 1 2.31 1.62 1.61 1.16 0.81 3.14 2.70 2.01 1.42 1.20 0 0 0 0 0Table 2 Experimental results of tensile and compressive strains at stress peak under biaxial tension-compression state ( 20°C 200°C 300°C 600 200 6000 0 0 0 0 0 1 0.

262 0.241 0.232 0.226 0.150 1 0.220 0.18
262 0.241 0.232 0.226 0.150 1 0.220 0.180 0.141 0.112 0.081 1 0.201 0.143 0.085 0.072 0.064 0.151 0.123 0.073 0.068 0.058 0 0 0 0 0 Relationship between tensile strength and temperatureBased on the test data list in Table 1, the regression equation represents the temperature. The curves calculated by Eq. (1) are shown in Fig. 4.and temperature is shown in Fig. 5.3.3 Failure criterionexperimental data are shown in Fig. 7. From the figure, it is axis, especially for samples respectively, =xxxx+121011010016625The correlation coefficients between the values calculated by Eq. (4) and experimental results are 0.997, 0.991, 0.997, 0.994, 0.991 respectively, corresponding to 20°C, 200°C, 0, Eq. (4) can be Fig. 5 Relationship between tensile strength and stress ratiosial tensile strength of concrete at 200°C decreases little. This experimental phenomenon may be due to the emerging of gel saa()=(+),..(,)tfttft151803659(),(), 041770104177..;stress ratios. The correlation coefficients between test results and values calculated by Eq. (3) for various stress ratios of and 0.988, respectively. The predicted curves are shown in Fig. 6. Based on the value of Fig. 6 Relationship of tensile strength and temperatures predicte