Fig. 1 shows a vertically loaded bracket attached to a fixed member by three identical bolts. The dimensions are in mm. Although the 24-kN load is normally applied in the center, the bolts are to be selected on the basis that the load eccentricity shown could occur. Because of safety considerations, SAE class 9.8 steel bolts and a minimum safety factor of 6 (based on proof strength) are to be used. Assume that bolt D has the most critical stress and there is no friction involved. To save your time, a diagram that shows the CG (Centroid of the bolts) and the shear forces is given in Fig. 1. (a) Determine an appropriate bolt size (in mm). (20 marks, C3) (b) What is the effect to the bolt size if load is not applied eccentrically, i.e., the load passes through the CG (centroid of the 3 bolts)? Explain the effect without showing any calculation. (5 marks, C4)
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Step 1: Compute total external force and moment: F = 24 kN; eccentricity e = 60 mm (horizontal offset from CG) so moment M = F * e = 24,000 N * 60 mm = 1,440,000 N·mm. Show more…
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Figure 1 shows a pinned base plate connection for the steel column of 310UC96.8 (Grade 300), which is subjected to axial tensile force (Nt* = 100 kN) and shear forces (Vx* = 25 kN) and (Vy* = 20 kN). The end of the steel column is cold sawn. 6 mm SP fillet weld was used along column section profile. The steel column is supported by a concrete foundation. Design information of the base plate is given below: Design Information: - The compressive strength of concrete, fc' = 25MPa - The cross-sectional area of base plate, A1 = 400 mm x 400 mm - The cross-sectional area of concrete foundation, A2 = 800 mm x 800 mm - Four M16 bolts (Grade 8.8/s) are used for the connection - Tensile strength of bolt (fuf) = 830MPa - M16 bolt axial tension capacity (ΦNtf) =104 kN - M16 bolt (Thread excluded from shear plane) shear capacity (ΦVvf) =82.7 kN - Gauge of anchor bolts, Sg= 100 mm - Pitch of anchor bolts, Sp= 200 mm - Yield strength of base plate, fyi= 250 MPa - Thickness of base plate, ti= 16 mm - Friction co-efficient, μ= 0.55 - Weld capacity (ΦVw)= 0.835 kN/mm Figure 1: Pinned base plate connection Check whether the bolt satisfies the requirement for combined tension and shear.
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A beam is welded to a plate that is bolted to a wall using 2 identical bolts. A 10 kN force F is applied on the end of the beam, and the bolts are SAE class 8.8 steel bolts, with a FOS of 3. Determine the required bolt size if: a) Shear is carried completely by friction between the plate and wall (i.e. there is only axial load on the bolts). b) Shear is carried completely by the bolts (i.e. there is both axial and direct shear load on the bolts). All pertinent dimensions are shown in Figure 2. Note, there is no torsion on the bolt group in this circumstance, only axial from the bending and direct shear down. Figure 1: Schematic of the beam arrangement. Figure 2: Side view of the arrangement with dimensions (not drawn to scale).
In Fig. $12-63,$ a rectangular slab of slate rests on a bedrock surface inclined at angle $\theta=26^{\circ} .$ The slab has length $L=43 \mathrm{m},$ thickness $T=2.5 \mathrm{m},$ and width $W=12 \mathrm{m},$ and 1.0 $\mathrm{cm}^{3}$ of it has a mass of 3.2 $\mathrm{g} .$ The coefficient of static friction between slab and bedrock is $0.39 .$ (a) Calculate the component of the gravitational force on the slab parallel to the bedrock surface. (b) Calculate the magnitude of the static frictional force on the slab. By comparing (a) and (b), you can see that the slab is in danger of sliding. This is prevented only by chance protrusions of bedrock. (c) To stabilize the slab, bolts are to be driven perpendicular to the bedrock surface (two bolts are shown). If each bolt has a cross-sectional area of 6.4 $\mathrm{cm}^{2}$ and will snap under a shearing stress of $3.6 \times 10^{8} \mathrm{N} / \mathrm{m}^{2},$ what is the minimum number of bolts needed? Assume that the bolts do not affect the normal force.
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