Civil Engineering Online Review

The activities and other conditions for a certain project are as follows:

1) Which of the following gives the critical path for the project.

2) Which of the following activity is the most cost effective to accelerate.

3) If the maximum budget is P22,600, how many days can you reduce the duration of the project?

Solution:

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Loads at Angle to Grain – allowable bolt loads acting in a direction inclined to grain shall be determined from the Hankinson formula which for total bolt loads, may be stated as follows:

Where:

N = allowable load per bolt in a direction at inclination A with the grain

P = allowable load per bolt in compression parallel to grain

Q = allowable load per bolt in compression perpendicular to grain

A = angle between the direction of the load and the direction of the grain

1) Which of the following gives the force carried by each bolt?

2) Which of the following gives the diameter if failure occurs at the secondary member?

3) Which of the following gives the diameter of bolts if failure occurs at the main member?

Solution:

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A 590mm x 590mm reinforced concrete column with section shown is subjected to a service axial dead load of 450kN. Live load of 500kN, dead load moment of 135 kN/m and live load moment of 150 kN/m. fc’ = 21Mpa and fy = 415Mpa

1) Which of the following gives the equivalent eccentricity of the load on the column.

2) Which of the following gives the minimum area of steel reinforcement.

3) Which of the following gives the minimum size of steel bars.

Solution:

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Two pieces of 75mm x 400mm Yacal members under tension are connected together by means of a lap splice with 9pcs of 25mm dia. Bolts as shown. The working stresses for 80% visually stress-graded unseasoned Yacal are as follows:

From table TM-6

Bending and tension parallel to grain      -24.5 MPa

Compression parallel to grain                     -15.8 MPa

Compression perpendicular to grain        -6.27 MPa

Shear parallel to grian                                     -2.49 MPa

1) Which of the following gives the net area of a timber member? Consider hole diameter to be 2mm larger than the bolt diameter

2) Which of the following gives the safe value of P considering the net area of the timber member?

3) Which of the following gives the safe value of P considering the bearing of the bolts on the timber.

Solution:

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A cantilever beam has a span of 3m. long is subjected to a concentrated load of 3 kN acting at 2m. from the support and a clockwise moment of 15kN.m at the free end. E = 200 GPa and I = 100,000,000 mm⁴.

1) Which of the following gives the deflection at the free end due to the concentrated load only.

2) Which of the following gives the deflection at the free end due to moment only.

3) Which of the following gives the max. deflection at the free end.

Solution:

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A. Classify the structure whether it is:

a) Statically determinate or stable

b) Unstable

c) Statically indeterminate to the 2^nd degree

d) Statically indeterminate to the first degree.

Solution:

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A bill of quantities is to be prepared for square isolated reinforced concrete column and footing as shown. The foundation is strong enough that form works is not required for footing. The swell factor for back fill is 120%.

1) Which of the following most nearly gives the quantity of excavation in m³.

2) Which of the following most nearly gives the quantity of concrete in m³.

3) Which of the following most nearly gives the quantity of form works in sq.m.

Solution:

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A block is shown is at rest on the rough horizontal plane before the force P is applied at t = 0. The magnitude of P is 80t, in Newton, where t is the time in seconds and its direction is constant. The coefficients of static and kinetic friction are 0.40 and 0.20 respectively.

1) Find the time when impending motion is reached.

2) What is the velocity after 5 seconds.

3) What is the distance traveled by the block after 5sec.

Solution:

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The continuous T-beam shown supports a dead load including its own weight of 16 kN/m and a live load of 32 kN/m of which 20% is assumed to be sustained. Fc’ = 17.2 MPa. The moment diagram for full dead load and live load is as shown.

Unless stiffness values are obtained by a more comprehensive analysis, immediate deflection shall be computed with the modulus of elasticity E_c for concrete as specified and with the effective moment of inertia as follows but not greater than I_g.

And for normal weight concrete: f_r = 0.70 √fc’ , E_c = 4700 √fc’. For continuous members, effective moment of inertia shall be permitted to be taken as the average of values obtained from equation (409-9) for the critical positive and negative moment sections For prismatic members, effective moment of inertia shall be permitted to be taken as the value obtained from equation (409-9) at midspan for simple and continuous spans and at support for cantilevers.

Unless values are obtained by a more comprehensive analysis, additional longtime deflections resulting from creep, and shrinkage of flexural members (normal-weight or light weight concrete) shall be determined by multiplying the immediate deflection caused by the sustain load considered by the factor:

Where ρ’ shall be the value at the midspan for simple and continuous beam and at support for cantilevers. It is permitted to assume the time dependent factor T for sustained loads to be equal to.

5 yrs. or more               2.0

12 months                     1.4

6 months                       1.2

3 months                        1.0

1) Compute the effective moment of inertia at the supports.

2) Compute the effective moment of inertia for continuous member.

3) If the instantaneous deflection is 5mm, what is the additional deflection on the sustained loadings.

Solution:

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The racing car shown is traveling at 140kph when it enters the semi-circular curve at A. The driver increases the speed at a uniform rate, emerging from the curve at C at 190kph.

1) Which of the following gives the tangential acceleration of the car at B.

2) Which of the following gives the speed acceleration of the car at B.

3) Which of the following gives the magnitude of the acceleration vector when the car is at B.

Solution:

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A plate is connected to a column by four bolts and carries an eccentric load as shown in figure. For this problem, the load P = 32.5 kN with an eccentricity e = 250mm. The dimension a = 150mm and b = 200mm. The diameter of the bolts is 20mm.

1) For this problem, assume that the load P acts through the centroid of the bolts. Which of the following most nearly gives the stress on the bolts, in MPa.

2) For this problem, assume that the only load acting on the connection is a moment equal to the load P multiplied by its eccentricity e. Which of the following most nearly gives the distance from the centroid of the bolts in mm where if a bolt is placed, the stress will be equal and opposite to the stress stress obtained in the first problem above.

3) Which of the following most nearly gives the eccentricity in mm of the load P, measured from the instantaneous center of the bolts.

Solution:

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From the given shear diagram shown.

1) Which of the following gives the max. concentrated load.

2) Which of the following gives the max. negative moment.

3) Which of the following gives the point of inflection from the right end.

Solution:

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A stag erred riveted connection has rivets arranged as shown. Diameter of rivets is 34mm. Diameter of holes is assumed to be 2mm bigger than that of the rivet. F_y = 248 MPa.

1) Which of the following gives the distance “b” so that the net area in chain 1-2-3-4 is equal to the net area of chain 1-2-4.

2) Using the computed value of “b”, solved for the net area.

3) Which of the following gives the maximum tensile force P that the riveted connection could carry if the allowable tensile stress is 0.6Fy.

Solution:

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The table shown tabulates the activities for making a network diagram for a project together with duration and cost in normal and accelerated conditions.

1) Which of the following route gives us the critical path.

2) Which of the following gives the cost if it is accelerated to the minimum duration.

3) If the max. available cost is P22,100, determine the no. of days deducted from the normal condition so that it will be economical.

Solution:

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The following data shows the different sizes of pipes which a company wishes to use as a replacement for the old pipe system that they are using.

Total no. of operating hours/year = P500

1) Which of the following gives the present worth of the 150mm pipe.

2) Which of the following gives the equivalent annual cost of 100mm pipe.

3) Which of the following gives the most preferable pipe to be used as replacement. Replacement is done every 10 years at an interest of 10% annually.

Solution:

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Section 5.7.7.1 of the NSCP specifies the minimum concrete cover provided for reinforcement for a cast in place concrete (non-pre stressed) as follows:

Minimum Cover

1) Concrete cast against permanently exposed to earth … 75mm

2) Concrete exposed to earth or weather:

20mm through

36mm bars …  50mm

16mm bars, W31 or D31

Wire and smaller …  40mm

3) Concrete not exposed to weather or in contact with the ground:

a. Slabs, walls, joists:

32mm bar and smaller … 20mm

b. Beam, Columns:

Primary reinforcement, ties, stirrups, spirals … 40mm

c. Shells, folded plate members:

20mm bar and larger … 20mm

16mm bar, W31 or D31 sire and smaller … 15mm

From the given details shown on figure C-25,C-26 and C-27.

Solution:

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From the given figure shown, a force P = 100kN is acting at 30° from the horizontal axis,

1) Which of the following gives the y-component of P with respect to x and y axis.

2) Which of the following gives the y-component of P with respect to x’ and y axis.

3) Which of the following gives the y’-component with respect to x’ and y’ axis.

Solution:

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Section 5.11.3.2.1 of the National Structural Code of the Philippines states that the shear strength V_c for members subject to shear and flexure only shall be equal to:

but not greater than shall not be taken greater than 1.0 in computing V_c. where M_u is the factored moment occuring simultaneously with V_u at section considered.

Section 5.11.3.2.2 states that for members subject to axial compression Equation (11-6) maybe used to compute V_c with M_m substituted for M_u and V_ud/μ_u not then limited to 1.0

Where:M_m = modified moment

M_u = factored moment occuring simultaneously with V_u at section considered.

N_u = factored axial load normal to cross-section occuring simultaneously with V_u, to be taken as positive for compression, negative for tension, and to include effects of tensio due to creep and shrinkage

h = overall thickness of member in mm.

d = distance from extreme compression fiber to centroid of longitudinal reinforcement but need not be less than 0.80h for prestressed members.

However V_c shall not be greater than:

Where the quantity N_u/Ag shall be expressed in MPa. When M_m as computed by equation (11-7) is negative, V_c shall be computed using equation (11-8).

A beam having a width of 300 mm and an overall thickness of 700 mm has an effective depth of 610 mm. It is reinforced with 3-32 mmØ  bars. The beam carries a factored concentrated load at the midspan of 450 kN and a horizontal axial factored compression load of 270 kN. Fc’ = 20.5 MPa.

1) Which of the following gives the value of the factored shear force V_u.

2) Which of the following gives the value of the modified moment M_m.

3) Which of the following gives the nominal shear strength of concrete.

Solution:

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From the given beam shown, it is subjected to a uniform load of 12 kN/m along span AB, and a concentrated load of 20 kN at the midspan of BC.

1) Which of the following gives the moment equation at the span AB.

2) Which of the following gives the moment equation at the span AB and BC.

3) Which of the following gives the moment at B.

Solution:

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For the cable loaded as shown in the figure.

1) Which of the following gives the value of the stress of BC.

2) Which of the following gives the value of the stress of β₁.

3) Which of the following gives the total length of the cable.

Solution:

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