February 21, 2020

PROBLEM 8.11

A couple M of magnitude 1500 N ⋅ m is applied to the crank of an engine. For the

position shown, determine (a) the force P required to hold the engine system in

equilibrium, (b) the average normal stress in the connecting rod BC, which has a

450-mm2 uniform cross section.

PROBLEM 8.12

Two hydraulic cylinders are used to control the position

of the robotic arm ABC. Knowing that the control rods

attached at A and D each have a 20-mm diameter and

happen to be parallel in the position shown, determine the

average normal stress in (a) member AE, (b) member DG.

PROBLEM 8.13

The wooden members A and B are to be joined by plywood splice

plates which will be fully glued on the surfaces in contact. As part of

the design of the joint, and knowing that the clearance between the

ends of the members is to be 8 mm, determine the smallest allowable

length L if the average shearing stress in the glue is not to exceed 800

kPa.

PROBLEM 8.14

Determine the diameter of the largest circular hole that can be punched into a sheet of polystyrene 6 mm

thick, knowing that the force exerted by the punch is 45 kN and that a 55-MPa average shearing stress is

required to cause the material to fail.

PROBLEM 1.15

Two wooden planks, each

1

2

in.

thick and

9 in.

wide, are joined by the dry mortise joint shown.

Knowing that the wood used shears off along its

grain when the average shearing stress reaches

1.20 ksi, determine the magnitude P of the axial

load that will cause the joint to fail.

PROBLEM 8.16

A load P is applied to a steel rod supported as shown by an

aluminum plate into which a 0.6-in.-diameter hole has been

drilled. Knowing that the shearing stress must not exceed

18 ksi in the steel rod and 10 ksi in the aluminum plate,

determine the largest load P that can be applied to the rod.

PROBLEM 8.17

An axial load P is supported by a short

W8 40×

column of cross-

sectional area

2

11.7 in=A

and is distributed to a concrete foundation

by a square plate as shown. Knowing that the average normal stress in

the column must not exceed 30 ksi and that the bearing stress on the

concrete foundation must not exceed 3.0 ksi, determine the side a of

the plate that will provide the most economical and safe design.

PROBLEM 8.18

The axial force in the column supporting the timber beam shown is

P

20=

kips. Determine the smallest allowable length L of the bearing

plate if the bearing stress in the timber is not to exceed 400 psi.

PROBLEM 8.19

Three wooden planks are fastened together by a series of bolts to form

a column. The diameter of each bolt is 12 mm and the inner diameter

of each washer is 16 mm, which is slightly larger than the diameter of

the holes in the planks. Determine the smallest allowable outer

diameter d of the washers, knowing that the average normal stress in

the bolts is 36 MPa and that the bearing stress between the washers

and the planks must not exceed 8.5 MPa.

PROBLEM 8.20

Link AB, of width b = 50 mm and thickness t = 6 mm, is used to support

the end of a horizontal beam. Knowing that the average normal stress in

the link is − 140 MPa, and that the average shearing stress in each of the

two pins is 80 MPa, determine (a) the diameter d of the pins, (b) the

average bearing stress in the link.