loadingTest report of normal cross-section failure of reinforced concrete beam
1. Experimental purposes
To understand the failure process of reinforced concrete beams, deformation features and mechanical behavior of the cross section under ultimate load.
2. Experimental devices and specimen (1)．Experimental devices
Jack, Force sensor, Strain indicator, Crack width gage, Reaction frame. (2)．Specimen: reinforced concrete beam, as shown in Figure 1.
Figure 1. Specification of reinforced concrete beam
Strength grade of concrete：C25, Steel bar： 2φ8，Ⅰclass Section size of specimen:
Protective layer thickness of steel bar：20mm
b＝100mm； h＝150mm； L＝1050mm；
3. Experimental program
A tested beam is a rectangular beam, and singly reinforced, using hydraulic
jacks to impose two concentrated loads F, and diagram of bending moment and shear force is shown in Figure 2. The shear is zero (ignoring beam weight) in CD section of the beam, while the bending moment is a constant, known as the \bending\section, which is the main target of experimental research. The concentrated force is measured by force sensor. Deflection is measured with dial indicator, placing at the mid-span of the test beam. Concrete strain is measured using a strain indicator, arranging measured points of 1, 2, 3, 4 and 5 along the height of beam. It is needed to record the applied force, deflection and strain and observe cracking.
Figure 2. Layout of a tested beam (unit: mm)
(1). Loading program
Stage loading, increas 2kN each time, and holding load 15 minutes each time.
(2). Measuring points shown in Figure 2
4. Relevant criterion
Strength failure of normal cross-section:
(1). The strain value of tention reinforcement reachs 0.01. (2). The tention reinforcement breakdown；
(3)．The crack width of concrete perpendicular to tention reinforcement reachs 1.5mm.
(4)．Deflection reachs 1/50 of span. (5). Concrete of compression zone fail.
5. Experiment record sheet
1. Stain record sheet: Load（kN） 1 2 Strain of measuring points（με） 3 4 5 Steel bar 1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 Steel bar 2 Curve of load-deflecton
2. Deflection record sheet: Load （kN） 1 0 2 4 6 8 10 12 14 16 18 Deflection of measuring points（mm） 2 3 20 22 24 26 28 30 32 34 36 load （kN） 1 Deflection of measuring points（mm） 2 3 Curve of Load-strain
6. Experience