Chapter 4: Testing procedures
4.1 Structural tests of CIBs
4.1.2 Testing the long beams
The aim of this testing procedure was to obtain the required data for calculating the modulus of elasticity in bending Em, the apparent modulus of elasticity Em,app, the shear modulus G and the maximum bending capacity of beams over 4.50 and 4.35 meter spans. The flowchart in Figure 4.7 shows the testing program which was developed to assess the structural properties of long, manufactured-beams.
Three-point-bending and four-point-bending tests were performed for the entire range of manufactured-beams. The results of these tests were then used to determine the apparent modulus of elasticity using both bending arrangements and to find the maximum bending capacity of the beams.
Two methods were used for measuring the shear modulus. In the first method, the shear modulus could be determined by calculating Em,app and Em for each long beam, whereas in the second method, shear modulus could be determined by
Chapter 4: Testing procedures
calculating the apparent modulus of elasticity Em,app for each beam over four different spans.
Figure 4.7 Shows the testing program which was developed to assess the long IIII
I
Collecting data to determine G –Method 2 Collecting data to
determine G –Method 1
M.L.D to determine E -3-point load, 1.45 m span
M.L.D to determine E -4-point load, 4.5 span
M.L.D to determine E -3-point load, 1.45 m span
M.L.D to determine E -3-point load, 2.1 span
M.L.D to determine E -3-point load, 3 m span
M.L.D to determine E -3-point load, 4.5 m span
Filled with polyurethane foam
Without
polyurethane foam
M. Max Bending capacity of the beams with/without
Testing the long beams
M.L.D* 3 points-bending
M.L.D 4-points-bending
4.35 m span
Chapter 4: Testing procedures
4.1.2.1 Long span bending tests-three-point-bending
A simply supported beam was loaded at the centre point, causing bending over a span 4.50 m long. Load and deflection were continuously recorded, so that the apparent modulus of elasticity could be calculated: see Figures 4.8(a) and 4.8(b).
• Measuring apparent modulus of elasticity of each beam before and after it was filled with injected polyurethane using the three-point-bending method.
Figure 4.8 (a) Test arrangement to measure the load-deflection of the beam subjected to three-point-bending
Figure 4.8 (b) Three points load test rig to measure load-deflection of filled boxed I-Beam over a 4.5m span
Transducer
Chapter 4: Testing procedures
4.1.2.2 Determination of shear modulus - method one Determination of modulus of elasticity in bending
Manufactured-beams 290mm deep were tested, simply supported at the ends giving a 4.35m span loaded by two loading heads. Each loading head was placed 1.30 m from the nearest support and 1.75 m from each other as shown in Figures 4.9(a) and 4.9(b). The aim was to measure the load deflection and from that to calculate the MoE under pure bending moment.
(a) Test arrangement to determine MoE in pure bending
(b) Measuring MoE in bending for double I-beam
Figure 4.9 Test arrangement and measurement of MoE in bending
Chapter 4: Testing procedures
Describing the apparatus and testing method
In order to measure relative deflection within pure bending area , a stand 1.45m long was made. That stand sat between two loading heads. A transducer was planted in the middle of the stand to measure the mid-span deflection relative to the legs of the stand. Figures 4.10(a) and 4.10(b) show the stand and the testing arrangement. Load-deflection results were recorded in order to determine the Em.
• Measuring the load and deflection relative to supports and the stand legs for beams subjected to four-point-bending before injecting the polyurethane. This procedure was repeated after injecting the foam.
After completion of the preceding tests, the same beam was tested over a span of 1.45 meters with two end supports as shown in Figures 4.10(a) and 4.10(b). The beam was loaded at the centre point. Load and deflection relative to the supports was monitored continuously and the data was recorded to determine the Em,app.
Summary:
• Measuring load-deflection relative to the supports for the beams subjected to three-point-bending before injecting the polyurethane. The procedure was repeated for the beams after foam was injected.
Shear modulus G, then can be calculated from the modulus of elasticity in bending Em and the apparent modulus of elasticity Em,app.
Figure 4.10(A) Test method to determine the apparent MoE over 1450mm span
Chapter 4: Testing procedures
Figure 4.10(B) LVL section subjected to three-point-bending over a 1450mm span
4.1.2.3 Determination of shear modulus - method two
In this method each beam was loaded at the middle point and was simply supported over spans measuring 4.50, 3.00, 2.10 and 1.45 meters, as shown in Figure 4.11. The load-deflection data was continuously recorded. Shear modulus G, could be determined by calculating the apparent modulus of elasticity of each beam for four different spans.
Summary:
• Measuring load-deflection relative to the support for beams subjected to three-point-bending over four different spans, before and after injecting the polyurethane.
Chapter 4: Testing procedures
Figure 4.11 Test methods to measure Eapp over 1.45, 2.10, 3.00 and 4.00 m spans
4.1.2.4 Long span bending tests, four-point-bending
Manufactured beams 290mm deep were tested to destruction each was simply supported at the ends of a 4.35m span and loaded with two loading heads, which were placed at 1.30 meters from the nearest support and 1.75 meters from each other.
Loads and deflections were recorded continuously so that maximum bending moment and overall stiffness, bending plus shear, could be determined over the maximum span. The test arrangement is illustrated in figure 4.12.
• Measuring load-deflection relative to the supports for the beams subjected to four-point-bending without filling material. This procedure was later repeated for filled beams.
• Measuring maximum bending capacity of both empty and filled beams subjected to four point bending.
Chapter 4: Testing procedures
Figure 4.12 Test method to measure load-deflection relative to supports