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Analysis of communications tower collapse

Chemical Analysis Failure Angle Tab. 1Chemicalcompos ~ tlons0fthefailureaIlgksteel3 of the accident more sand in the region in spring and autumn. According to the survey, some time before the accident, a wind is strong, you can hear the metal sound coming from the direction of Tower. Check the number of connected parts of the bolts, that bolt (without locking device) is obviously most loose, and some may be under the hand screw it; some even exists between the nut and the connecting plate axial 3ram loose clearance. Tower base (not collapsed) actinide column connection at the corner nuts are mostly loose, gently with a wrench to remove. Some even hand to unscrew. There is obviously a lot of bolt holes caused by relative sliding wear marks, the thread is almost bald (see Figure 6, where the long bolts for the tower between the base angle of the fastening bolts.) Screw on the appropriate angle Columbium was grinding Houxu Ming: Analysis of communication tower collapses the table in Table 2 the performance failure angle compared with the standard value of Tab. 2Comparisonw [ththemhanica1propertyofthestandardva] ueandthefailureanglesteelwaiue Note: 1) the impact value is a small sample cross-section 1OmmX5mm measured. Figure 6 worn bolts Fig, 6Theabrasionbolts Figure 7B wear angle connection Fig. 7Thex ~ eal-ofBangleironintheconnection light, and some even grind the thread of bolt (see Figure 7a Office). Observed in Figure 7, connecting the inside of the short length of angle iron angle (no connection outside of the short angle) along the screw from the end of only 15mm. Thus, when the bolts loose, in the bending or torsional force, the connection of the lug holes at the material can not serve effectively to strengthen and protect the use. Some angle with the inclined angle connections have been polished (see Figure 7), the surface covered with a black metal oxide powder that angle and the inclined angle is between the loose, and fretting wear one place. \,[link widoczny dla zalogowanych], the tower shaking and bending occurs; many of bolts loosening, significantly weakened the constraints of its angle, so that rate of increase tower sway and bend. excessive sway and bend to angle under a lot of bending and torsion forces. bolts loose also makes the short length of angle and angle tighten the connection between the no longer maintained, so that can not lug an effective resistance to bending and torsion forces acting. B angle mounting holes (17mm) where the cross section, the holes caused by the stress concentration and effective bearing area decreases, so that it become a weak link; and more loose bolts in the cross section increases the risk of bending normal stress when the department suffered more than the material yield strength occurs when the bending angles tB plastic deformation (see Figure 7) and make the tower bending, tilt intensified. This section suffered a greater bending of the normal stress t is the stress when bending over bending strength,[link widoczny dla zalogowanych], the angle B to cause cracking, leading to instability and collapse of tower. B angle fracture source is located in Figure 7 or Figure 2, at the upper left corner. In turn the blood is under stress, the crack along the direction of arrow 2 in Figure 7, when the crack extended to the arrow in Figure 7, within the meaning of section 1, the bolt on the angle because of the continued tilt, bending impediment,[link widoczny dla zalogowanych], cracks in bending, torsion and extension under the action of stress,[link widoczny dla zalogowanych], and eventually leading to complete fracture angle B. 4 Conclusion (1) tower collapse was not caused by the use of substandard material properties. (2) Tower collapse where the cross section is due to the weak link screw suffered bending stress exceeds the bending strength is due. but in a windy environment, the lack of long-term use in the necessary maintenance, resulting in various parts of the fastening bolts loose; and in strong wind under the action of the tower and the plastic bending over shaking due to tilt is increased is caused by bending causes too much stress. Recommendations: Tower should always check for loose bolts and tighten a timely manner to avoid the occurrence of tower collapsed. reference Document: E1] Hou Xuming. Metal Mechanical Properties [M]. Beijing: China Machine Press Du ,1999.47-5L [2] Heat Treatment of Metals Research Group,[link widoczny dla zalogowanych], Shanghai Jiaotong University. metal fracture analysis [M]. Shanghai: Shanghai Jiaotong University, 1976 .118 - lZ0. [33 Wu Liansheng. failure analysis technology and its application [J]. Physical Testing of a physical volumes, 1996,32 (1) :57-62. [43 bundle of virtues. Mechanical Properties of Engineering Materials [M] . Beijing: China Machine Press, 2003.170. [5] Zhou Hui years. Behavior of Materials Science [M]. Beijing: Science Press, 1989.513. ・ 26l ・

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