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Erection Bracing of Low-Rise Structural Steel Buildings phần 4

thể thu được bằng cách cài đặt các ốc vít hơn đến sức mạnh thiết kế đầy đủ. Cường độ thiết kế bổ sung này có thể được kết hợp trong chương trình giằng tạm thời. Vì tính phức tạp của việc tích hợp kết nối cuối cùng trong tạm thời hỗ trợ chủ đề này là không phát triển trong hướng dẫn này, tuy nhiên các nguyên tắc được phát triển đầy đủ trong văn học hiện nay như tay LRFD . | Calculating qz 0.00256 0.46X1.0 0.75 75 2 3.73 psf 3 1 03 F - 3.73 1.54 1 1.5 Af R.61 Af The area of the frame Aj. is computed as follows First frame - 40 0.5 18 12 25 0.5 8 12 30 8.33 38.33 ft.2 Thus the total frame area is 3 38.33 4 38.33 1.0 - 0.15 245.3 ft.2 The net area of joists is computed as 22 12 20 6 7 0.3 0.7 323.4 ft.2 Thus Af 245.3 323.4 568.7 ft.2 F at the level of the roof strut is F 8.61 568.7 4 896.6 lbs. F 4.9 kips Force in diagonal 4.9 kips 47.2 40 5.8 kips This force is less than the bracing force of 38 kips for which the permanent bracing is designed. One bolt in each angle is adequate to resist the temporary bracing force in the diagonal. The permanent bracing connections are adequate by inspection. The roof strut itself is a W24X55 spanning 40 feet. The strut force is 4.8 kips. Per Tables 4.1 and 4.2 it can be seen that this member is adequate to carry the strut force. A check of PA effects is not necessary for permanent diagonal bracing used as part of the temporary bracing scheme. Lastly the column on the compression side of the diagonally braced bay must be checked. The column itself is adequate by inspection for the vertical component of the temporary bracing force. This vertical component is 5.8 25 47.2 3.1 kips which is far less than the column axial capacity. 4.5 Beam to Column Connections In the typical erection process the beam to column connections are erected using only the minimum number of bolts required by OSHA regulations. This is done to expedite the process of raising the steel in order to minimize the use of cranes. Final bolting is not done until the structure is plumbed. In addition to the connection design strength using the minimum fasteners additional design strength can be obtained by installing more fasteners up to the full design strength. This additional design strength can be incorporated in the temporary bracing scheme. Because of the complexity of integrating final connections in the temporary supports this topic