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4 Investigation, testing and monitoring taking x-ray pictures. The result of these tests showed that up to 60% of all welding work did not meet the requested quality. On top of this, the tests were not sufficient to determine in which degree the welding itself was able to fulfil its duty. The outcome of the test was simply: approved of not-approved. Besides the fact that the welding was not approved, it showed, during a visit at the building site, that the demand for tolerance on positioning and alignment was exceeded. The image on Figure 8 shows both rotation and translation of the profile beyond acceptable and allowable tolerances. The profiles were displaced with maximum 45 degrees rotation in relation to the theoretical axis and in addition against the inner side of the pipe leaving no concrete cover.
Combining these tolerances creates an image as shown in Figure 11 were the bored pile deviates from the theoretical straight line. The different sections, A D, are sketched in the cross sections below in Figure 9. This Figure shows inconsistency in relation to the theoretical axis. Figure 9 Rotated, eccentric and a- profile. When the HE-B profile is installed, the pile will make contact at one side of the pipe, see Figure 10. Figure 8 Rotated, eccentric and a-symmetric HE-160B profile.
From the evaluation of these data, it was concluded that the quality of the structural cross-section did not meet the design requirements and measures had to be taken. 1.5 Forensic engineering By contract the tolerance of placement for the HE beams was limited to one-degree rotation. After having spoken with the craftsmen on the job the comment on why the beam had been rotated was: it will always turn.
There was no further explanation. The principle is as follows. The straightness of the bored pile depends on the tolerances from both practical side as well as theoretical and contractual side as mentioned before. Figure 10 Collison of the profile with the inner side of the pipe. With this contact the HE-B profile will follow the direction or alignment of the pipe locally which has different directions in cross section A, B, C and D. As a consequence, the HE-B profile will turn and finally rotate. This process is a direct result of the profiles own weight and therefore the rotational movement goes with great forces which cannot be adjusted during installing neither changed after the profile has reached its final depth.
Figure11: Deviation of practice and theoretical placement. NGM Proceedings 406 IGS 5 Forensic engineering of a bored pile wall After having established the very cause of the rotation and displacement of the combined profile, the next step was to check the influence of this changed combined profile. See Figure 12 for the calculation of the displaced and rotated profile, with corresponding deviation in relation to the obtained capacity. Table 2 shows an overview. It is not allowed to simply add the moment capacity of the tubular pipe and that of the beam, M pipe +M HEB160 = (78, ) * centre distance (1/0,6) = 306,4 (knm). This will give considerable more capacity in relation to the calculated. This is due to the fact that both profiles do not have the same neutral line to be followed with calculating the maximum moment capacity, see Figure 13. Ga-vm900m drivers windows 7 64.
Figure12 Calculation of the rotated, eccentric and a-symmetric composite profile. Figure 13 Capacity overview of the rotated, eccentric and a-symmetric composite pile profile. The capacity of the piles was reduced with 19% in elastic state and approximately 15% for the plastic state. The proper way to calculate the moment of inertia for hybrid profiles with translational and rotational motion is buy using Steiner s theorem. The challenge with the welding was charted by checking welding protocols on welding positions along the tubular pipe.
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