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Erection Bracing of Low-Rise Structural Steel Buildings phần 5

Cần lưu ý rằng các thanh neo phải được phát triển đầy đủ để chống lại một cú đấm thông qua thất bại mỗi mục 4.2.5. Thiết kế sức mạnh chịu cắt bằng cách sử dụng các thủ tục và ký hiệu trong UBC-94 | Column 1 40 25 1 000 lbs. Beams 2 35 40 0.5 1 400 lbs. Girders 2 68 40 0.5 2 720 lbs. Roof framing 40 40 5 8.000 lbs. Total 13 120 lbs. 13.1 kips Gravity load 13.1 kips lbs. Wind vertical component 5.9 kips Net compression on anchor rods 7.2 kips Using load factors per the AISC LRFD Specification Pu 0.9D 1.3W 0.9 13.1 -1.3 5.9 4.1 kips compression Pu 1.2D-1.3W 1.2 13.1 -1.3 5.9 8.1 kips compression Vu 1.3 W 1.3 9.4 12.2 kips Check resistance of 4 1 in. diameter anchor rods. Grout thickness is 3 in. Anchor rods have heavy hex leveling nuts and 3 8 in. plate washers. Anchors are spaced at 10 in. centers and are embedded 12 in. Anchor rods ASTM A36 Concrete fc 3500 psi Force to each anchor rod Axial 8.1 4 2.0 kips compression Shear 12.2 4 3.1 kips Using procedure from Section 4.2.4 for axial load k 1.0 Ab 0.7854in.2 3- 0.375 1 1.625 in. r 0.25 d 0.25 1 0.25 in. kL r 1 1.625 70.25 6.5 J cFcr 30.53 ksi per LRFD Table 3-36 t pn ộcFcr Ab 30.53 0.7854 24.0 kips Bending Moment arm 0.5 3 - 0.375 1 0.81 in. Mu 3.1 0.81 2478 in.-lb. 2.5 in.-kip ộMn - ộFyZx 0.9 36 0.167 5.4 in.-kip where Zx d3 6 1 3 6 0.167 in.3 Fy 36 ksi Ộ 0.9 Using LRFD Eq. H1 -16 Pu ộPn 0.2 2 240 M 0.50 L0 It should be noted that the anchor rods must be adequately developed to resist a punch through failure per Section 4.2.5. Design strength in shear using the procedure and notation in UBC-94 Vss 0.75 Abf s ỘVC ộ 800 AbZ f c l 2 Vss 0.75 0.785 58 34.1 kips J VC 0.85 800 0.785 1 3500 1 2 1 1000 31.5 kips Vu 3.1 kips 3.1 31.5 o.k. In this example the loads load factors and load combinations resulted in a net compressive force on the anchor rods. To illustrate the calculation procedure using a net tension force the example continues using a Pu 8.1 kips tension. All other design parameters remain unchanged. Force to each anchor rod Axial 8.1 4 2.0 kips tension Shear 12.2 4 3.1 kips Using the procedure and notation in UBC-94 Design strength in tension ỘPSS 0.9 Ab f s ộPc ộk 2.8As 4At where Ab n .5 2 0.785 in.2 f