Engineering Answers

A storm sewer is proposed to drain a 24 hectares drainage area shown in the figure below. With given data in the table below, determine x if the design discharge needed to convey 5-year peak discharge is 3.75m3/sec. (i=6270/(t+29))

C <-----------------> D

1Tt=15 min 2

For Site C For site D

Area (ha)=10 Area(ha)=14

C =0.6 C =0.45

Inlet time(min)=9 inlet time= X

Where did you get the t=12 and where did you base it? Why is it 10%? Thank you!

For this assignment, do a take-off for Structural Work. For this assignment, you may only focus on the Reinforcement ONLY. Exclude the concrete and formwork from the take-off list. Include in your take off list:

1. Reinforcement in slab

2. Reinforcement in pad footing

3. Starter bar in column stump

In a certain eight-pole, 50 Hz three-phase induction motor, the rotor resistance per phase is 0.04 Ω and the maximum torque occurs at a speed of 645 revolutions per minute (rpm). Assuming that the air-gap flux is constant at all loads, determine the torque developed as a percentage of maximum torque:

(a) at starting (8.0 marks) and  

(b) when the slip is 3 per cent (5.0 marks).                                           

Hint: Some derivation is necessary and reasonable approximations/assumptions will have to be made in order to solve this problem.

A 2200-V, 50-Hz, delta-connected three-phase induction motor has a star-connected slip-ring rotor with a phase effective transformation ratio of 3.8. The rotor resistance and stand-still leakage reactance are 0.012-ohm and 0.25-ohm per phase, respectively. Neglecting stator impedance and magnetising current,

(a) determine the rotor current and the corresponding stator and line currents at the instant the motor is started with the slip-rings shorted (4.0 marks).

(b) if the maximum allowable current in the motor supply lines is 600 A, determine the external rotor resistance per phase required to achieve this requirement (6.0 marks).

(c) determine the full-load currents if the full-load slip is 3% (4.0 marks).  

(14.0 marks in total)

A spring-mass system, with m = 100 kg and k = 400 N/m, is subjected to a harmonic force

f(t)= F0 cos (wt) with F0 = 10 N. Find the response of the system when v is equal to (a) 2

rad/s, (b) 0.2 rad/s, and (c) 20 rad/s.

As shown below in the figure, a bracket with a solid circular cross-section of radius r = 67 mm is inserted into a frictionless sleeve (slightly larger than the bracket) at A and is also supported by a pin at C. The sleeve at A allows free rotation of the bracket with respect to z_o axis and also freely translate about the same axis. The bracket has two arms, namely arm AB of length b = 0.75 m and arm BC of length a = 0.40 m. Moments M₁ = 1.6 kN.m and M₂=1.91 kN.m are applied at the point C.

1. calculate the maximum tensile stress along with the location and direction.

2. calculate the maximum compressive stress along with the location and direction.

3. calculate at point p(see cross section and the figure) on the cross-section at A the maximum in-plane shear stress.

4. also identify the point where absolute maximum shear stress takes place and calculate the same with the direction.

A single-threaded worm has an axial pitch of 20 mm and a pitch diameter of 50 mm. The worm rotates at 500 rev/min and drives a gear having 40 teeth and a transverse pressure angle. The power transmitted is 0.5 kW. Determine (a) the lead angle of the worm, (b) the center distance between worm and gear, and (c) the tangential, radial, and thrust forces on the worm gear.