### Civil Engineering Interview Questions & Answers

What are the causes of building collapse?

The Passage of time is one reason. Buildings also collapse due to weak foundations. Earthquakes, hurricanes and other natural disasters can also damage the structure of the buildings and cause it to collapse. Bombings or demolition of buildings is also other reasons.

What are the applications of modulus of elasticity?

As the term implies, “Modulus of Elasticity relates to the elasticity or “flexibility” of a material. The value of modulus of elasticity is very much significant relating to deflection of certain materials used in the construction industry. Take for example the general E value of mild carbon steel is about 200 GPA compared to about 70 GPA for aluminum. This simply translate that aluminum is 3 times flexible than steel.

How do you measure concrete?

Cubic feet, Cubic yards, Cubic Meter

Which is stronger solid steel rod or hollow steel pipe?

On a per pound basis, steel pipe is stronger in bending and is less likely to buckle in axial compression.

What is aggregate?

Aggregate is the component of a composite material used to resist compressive stress.

How do you calculate the power of a centrifugal pump?

The input power, that is, the power required to operate the pump should be stated in Hp (horsepower) on the pump’s nameplate. It can also be calculated by the 3-phase power equation:

P(in Hp) = VI(1.7c) = Rated Voltage x Rated Current x 1.73/ %Efficiency

If this is a consumer grade pump that operates on 120Vac, then the equation becomes P = VI, simply multiply the operating voltage, 120 x current (which is the number followed by the letter “A”.The output power, which really is not technically power, but rated in Gpm (gallons per minute), or caPAcity should also be on the nameplate. If you have the make, model, and (not necessarily needed) the serial number (also on the nameplate) you could call the manufacturer’s customer service dept. As an application engineer, I have contacted countless manufacturers, and service dept’s for assistance. It is now big deal to them, they will be happy to answer your questions.

What is rigging?

In sailing, the ropes used to move the sails around so the boat will move in the right direction when the wind blows.

What is absolute pressure?

Absolute pressure is simply the addition of the observed gage pressure plus the value of the local atmospheric pressure.

How do we calculate absolute pressure?

Absolute is equal to gauge pressure plus atmospheric.

What is Gravity flow?

Gravity flow is fluid flowing due to the forces of gravity alone and not to an applied pressure head. In the Bernoulli equation, the pressure term is omitted, and the height and velocity terms are the only ones included.

What do you mean by honeycomb in concrete?

Some people call it an air pocket in the concrete or a void. It is the exposed course aggregates on surface of concrete without covered by mortar or surrounding the aggregate particles.

What is the purpose of the gap in the road on this bridge?

Purpose of the gap in the road is to allow the road to exPAnd and contract with temperature changes without causing damage or deformation to the road.

What is a projection line?

Projection line is the way, in which the earth is shown on a flat piece of Paper.

What are moment of inertia and its importance in civil engineering?

The moment of inertia measures the opposition any kind of body will have against a certain momentum (along that same axis) trying to rotate that body.

What is the absolute pressure scale?

Absolute pressure is calculated from a vacuum (0 PSI) and atmospheric pressure is14.7PSIa or 14.7 PSI above a vacuum 1PSI on a tire pressure gauge is called 1PSIg = 15.7PSIa 10PSIg=24.7PSIa 100PSIg=114.7PSIa etc.

What is diversion tunnel in a dam?

When a dam is to be built, a diversion tunnel is usually bored through solid rock next to the dam site to byPAss the dam construction site. The dam is built while the river flows through the diversion tunnel.

How do you maintain water pressure?

If you have water pressure and wish to maintain it, do not cause flow in the line, which will reduce pressure due to friction. To keep pressure up, reduce friction by increasing the line size or eliminating some other restriction.

What are some structures that may be subjected to fatigue?

Bridges, hydraulic presses, burners trains

Why does the pressure increase under soil?

Soil pressure increases with depth due to the overburden or self-weight of the soil and due to loads imposed upon the soil.

For example, the pressure variation below the depth of soil is linear and the relation is given by pressure = unit wt * depth. As depth increases, there will be a linear increase in the soil pressure.

What is the distance between railway tracks?

4 feet, 8 1/2 inches.

How do you measure concrete?
Cubic feet, Cubic yards, Cubic Meter

Which is stronger solid steel rod or hollow steel pipe?

On a per pound basis, steel pipe is stronger in bending and is less likely to buckle in axial compression.

What is the tallest man made structure in the world?

The tallest man made structure is the KVLY-TV mast which is 2063 feet tall. The worlds tallest man made structure is Burj Dubai which is 800 meter tall.

What is braced excavation all about?

Excavations are braced to prevent the cave-in of surrounding unstable soil.

What is the meaning of soil reinforcement?

Soil reinforcement is the act of improving soil strength to enable it support or carry more load.

Two common examples are:

a) Mixing a soil amendment such as lime into weak clayey soil and re-comPActing to improve soil-bearing caPAcity (often done under the road base in highway construction)

b) Installing plastic or composite webbing layers (called geo-grid material) alternating with comPActed soil to produce a stronger sloped soil structure (often done on steep roadway embankments to improve strength and stability)

What is aggregate?

Aggregate is the component of a composite material used to resist compressive stress.

What year was the keystone power plant in Indiana County constructed?

1967 began commercial operation on unit 1.

What is the force exerted by the Tacoma narrows bridge?

The force exerted to the Tacoma narrows bridge was initially the wind resistance. The wind resistance caused the whole bridge to act as a system with forced vibration with damping.

What are the uses of alloys in daily life and how are alloys made?

Alloying is not always done to produce a ‘superior’ material, but to produce materials having a desired requirement in the industry or elsewhere. A classic case is of lead solder (containing lead & tin), in which the melting point of the constituent elements are lowered, not necessarily a desirable property.

Alloying can be carried out using hot press method (a sheet of material is sandwiched with alloying material), rolling the heated base metal in a drum full of alloying metal powder, using hot spraying, galvanizing (dipping the base in a molten solution of alloying material) etc. Sometimes the alloying material is added in small proportions to the molten base metal (e.g., in production of different types of steel).

What is the worlds largest concrete dam?

The Grand Coulee Dam is said to be the largest concrete dam. Currently the world’s largest concrete dam is the Itaipu Dam, an accomplishment of two neighboring countries, Brazil and Paraguay in South America.

Though it is not finished yet, the Three Gorges (or Sandapong) Dam on the Yangtze River in China will take over as the largest upon its completion, which is slated for 2009.

What are the main reasons of building collapse?

There are several reasons for building collapse. Passage of time is the main reason. Also, weak foundations, natural calamities like earthquakes, hurricanes, etc., are the major reasons for building collapse. Bombing and destruction is also another major reason.

State the applications of modulus of elasticity.

Modulus of elasticity is related to the flexibility of the material. The value of modulus of elasticity is pretty important in case of deflection of different materials used in building construction.

How are the freeway bridges built?

The traffic that is likely to go over the bridge at a time is estimated and the cement, rocked with rebar stanchions is placed over the freeway to build a bridge. Off-ramp from freeway to the bridge and on-ramp from the bridge to the freeway are constructed. Cement slabs are used to build a platform.

What is the basic difference in absorption, adsorption, and sorption?

Absorption refers to the phenomenon where an atom, molecule or ions enter any bulk phase like gas, solid or liquid. Absorption refers to the phenomenon where energy of photon is transferred to other entity.

Adsorption is similar to absorption. It refers to the surface rather than a volume. Adsorption takes place when the gas or liquid solute accumulates on the surface of solid. A substance diffuses in liquid or solid to form a solution.

Difference between routine maintenance and major maintenance for school facilities:

Routine maintenance is handling the minor repairs of the school campus. Major maintenance can be total reconstruction or renovation of the school.

What is soil analysis?

Soil analysis is the testing of soil to determine the nutritional and elemental composition of soil. It is generally tested for knowing the contents of nitrogen, potassium and phosphorous.

State the building codes.

These codes are the set of specifications to ensure the safety associated with any building construction. These codes are associated with the height, spacing, and installation of the building. These codes play an important role in vacating the building in case of any emergency situations.

From these interview questions, you will get an idea of the questions interviewer can ask you in the civil engineering position interview. Refer to some more sample questions here and revise all the answers carefully.

What are the steps involved in the concreting process, explain?

The major steps involved in the process of concreting are as follows:

1. Batching
2. Mixing
3. Transporting and placing of concrete
4. Compacting.

Batching: The process of measurement of the different materials for the making of concrete is known as batching. batching is usually done in two ways: volume batching and weight batching. In case of volume batching the measurement is done in the form of volume whereas in the case of weight batching it is done by the weight.

Mixing: In order to create good concrete the mixing of the materials should be first done in dry condition and after it wet condition. The two general methods of mixing are: hand mixing and machine mixing.

Transportation and placing of concrete: Once the concrete mixture is created it must be transported to its final location. The concrete is placed on form works and should always be dropped on its final location as closely as possible.

Compaction of concrete: When concrete is placed it can have air bubbles entrapped in it which can lead to the reduction of the strength by 30%. In order to reduce the air bubbles the process of compaction is performed. Compaction is generally performed in two ways: by hand or by the use of vibrators.

Describe briefly the various methods of concrete curing.

Curing is the process of maintaining the moisture and temperature conditions for freshly deployed concrete. This is done for small duration of time to allow the hardening of concrete. The methods that are involved in saving the shrinkage of the concrete includes:
(a) Spraying of water: on walls, and columns can be cured by sprinkling water.
(b) Wet covering of surface: can be cured by using the surface with wet gunny bags or straw
(c) Ponding: the horizontal surfaces including the slab and floors can be cured by stagnating the water.
(d) Steam curing: of pre-fabricated concrete units steam can be cured by passing it over the units that are under closed chambers. It allows faster curing process and results in faster recovery.
(e) Application of curing compounds: compounds having calcium chloride can be applied on curing surface. This keeps the surface wet for a very long time.

What do you understand by preset during the installation process of bridge bearings?

During the installation of bridge bearings the size of the upper plates is reduced to save the material costs. This process is known as preset. Generally the upper bearing plate comprises of the following components:
> Length of bearing
> 2 x irreversible movement.
> 2 x reversible movement.
The bearing initially is placed right in the middle point of the upper bearing plate. No directional effects of irreversible movement is considered. But since the irreversible movement usually takes place in one direction only the displaced direction is placed away from the midpoint. In such cases the length of the upper plate is equal to the length of the length of the bearing + irreversible movement + 2 x reversible movement.

Why are steel plates inserted inside bearings in elastomeric bearings?

In order to make a elastomeric bearing act/ function as a soft spring it should be made to allow it to bulge laterally and also the stiffness compression can be increased by simply increasing the limiting amount of the lateral bulging. In many cases in order to increase the compression stiffness of the bearing the usage of metal plates is made. Once steel plates are included in the bearings the freedom of the bulge is restricted dramatically, also the deflection of the bearing is reduced as compared to a bearing without the presence of steel plates. The tensile stresses of the bearings are induced into the steel plates. But the presence of the metal plates does not affect the shear stiffness of the bearings.

What reinforcements are used in the process of prestressing?

The major types of reinforcements used in prestressing are:

Spalling Reinforcement: The spalling stresses leads to stress behind the loaded area of the anchor blocks. This results in the breaking off of the surface concrete. The most likely causes of such types of stresses are Poisson`s effects strain interoperability or by the stress trajectory shapes.

Equilibrium reinforcements: This type of reinforcements are required where several anchorages exist where the prestressing loads are applied in a sequential manner.

Bursting Reinforcements: These kinds of stresses occur in cases where the stress trajectories are concave towards the line of action of load. In order to reduce such stresses reinforcements in the form of bursting is required.

In the design of bridge arguments what considerations should be made to select the orientation of the wing walls?

Some of the most common arrangements of wing walls in cases of bridge arguments are as follows:

Wing walls parallel to abutments: This method is considered to take least amount of time to build and is simple as well. But on the downside this method is not the most economical. The advantage of this type of design being that they cause the least amount of disturbance to the slope embankment.

Wing walls at an angle to abutments: This design method is considered to be the most economical in terms of material cost.

Wing walls perpendicular to abutments: The characteristic of this design is it provides an alignment continuous with the bridge decks lending a support to the parapets.

In case if concrete box girder bridges how is the number of cells determined?

When the depth of a box girder bridge exceed 1/6th or 1/5th of the bridge width then the design recommended is that of a single cell box girder bridge. But in case the depth of the bridge is lower than 1/6th of the bridge width then a twin-cell or in some cases multiple cell is the preferred choice. One should also note that even in the cases of wider bridges where there depths are comparatively low the number of cells should be minimized. This is so as there is noticeably not much improvement in the transverse load distribution when the number of cells of the box girder is higher than three or more.

Under what circumstances should pot bearings be used instead of elastomeric bearings?

Pot bearings are preferred over elastomeric bearings in situations where there are chances of high vertical loads in combinations of very large angle of rotations. Elastomeric bearings always require a large bearing surface so that a compression is maintained between the contact surfaces in between the piers and the bearings. This is not possible to maintained in high load and rotation environment. Also the usage of elastomeric bearings leads to the uneven distribution of stress on the piers. This results in some highly induced stresses to be targeted at the piers henceforth damaging them. Due to the above reasons pot bearings are preferred over elastomeric bearings in such cases.

Why should pumping be not used in case of concreting works?

During the pumping operation the pump exerted pressure must overcome any friction between the pumping pipes and the concrete, also the weight of the concrete and the pressure head when the concrete is placed above the pumps. Since only water is pump able, all the pressure generated is by the water that is present in the concrete. The major problem due to pumping are segregation effects and bleeding. In order to rectify and reduce these effects, generally the proportion of the cement is increased in order to increase the cohesion , which leads to the reduction of segregation and bleeding. Also if a proper selection of the aggregate grading can vastly improve the concrete pump ability.

Why should curing not be done by ponding and polythene sheets?

The primary purpose of curing is to reduce the heat loss of concrete that is freshly placed to the atmosphere and in order to reduce the temperature gradient across the cross-section of the concrete. Ponding is not preferred for curing as this method of thermal curing is greatly affected by cold winds. In addition to that in ponding large amounts of water is used and has to be disposed off from the construction sites. Polythene sheets are used on the basis that it creates an airtight environment around the concrete surface henceforth reducing the chances of evaporation over fresh concrete surfaces. But the usage of polythene can be a drawback as it can be easily blown away by winds and also the water lost by self-desiccation cannot be replenished.

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