Civil and Environmental Engineering Answers

The water-cement ratio is important because it influences all of the desirable qualities of concrete. What is the minimum water-cement ratio for hydration only?

The water-cement ratio is important because it influences all of the desirable qualities of concrete. What is the typical water-cement ratio for normal strength concrete?

A roof truss and the detail of the riveted connection at joint B, see Fig. 2. Using allowable stresses

of ߬ = 70 MPa and ߪ ௕ൌ 140 ܯ ,ܽܲhow many 22-mm diameter rivets are required to fasten

members BC and member BE to the gusset plate. What is the largest average tensile or compressive

stress in BC and BE?

Continuous cable ADB runs over a small frictionless pulley at D to support beam OABC which is

part of an entrance canopy for a building (see figure 3). A downward distributed load with peak

intensity q0 = 5 kN/m at O acts on the beam. Assume that canopy weight W = 8 kN and that cable

cross-sectional area is 100 mm2

.

a) Find cable force T and pin support reactions at O and D

b) Find the normal stress in the cable in the cable ADB

c) Determine the required diameter of pins A, B, D and O if the pins are in double shear and

the allowable shear stress is 80 MPa? Note that OA = AB = BC = 1.5m.

A continuous cable (diameter 6 mm) with tension force T is attached to a horizontal frame member

at B and C to support a sign structure, Fig. 1. The cable passes over a small pulley at D. The wire

is made of a copper alloy, and the stress-strain relationship for the wire is

(a) Find the axial normal strain in the cable and its elongation due to the load W = 6.8 kN

(b) If the forces are removed, what is the permanent set of the cable.

Hint: Start with constructing the stress-strain diagram and determine the modulus of elasticity, E

and the 0.2% offset yield stress.

What are the typical deleterious substances in aggregates that affect Portland cement concrete?

Discuss this effects briefly.

What is alkali-silica reactivity? What kinds of problems are caused by ASR? Mention two ways to minimize ASR

Define the fineness modulus of aggregate. What is it used for?

The following laboratory tests are performed on aggregate samples:

a) Specific gravity and absorption

b) Soundness

c) Sieve analysis test

What is the significance and use of each of these tests?

Define the following terms:

a) Saturated Surface-Dry (SSD) conditions of aggregates

b) Absorption of aggregates

c) Free water on aggregates