Essential Civil Engineering Interview Questions For Freshers Part – 3

What is civil engineering?

Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings.

Civil engineering is arguably the oldest engineering discipline. It deals with the built environment and can be dated to the first time someone placed a roof over his/her head or laid a tree trunk across a river to make it easier to get across.

What does civil engineering do?

They do many interesting things. Their job has to do a lot with design and construction. They can tell you what works and what will not for all sorts of situations.

There is a lot of mathematics involved along with many other disciplines. They have to have a good solid understanding of how the environment works and how nature interacts with manmade. They are probably best known for designing bridges, interstates, skyscrapers, canals, and so forth.

What is the difference between shear and tensile strength?

Tensile Strength for a Bolt is determined by applying a Force along it long axis. Shear Strength for a Bolt is determined by applying a Force across its diameter, as it would be loaded in a lug joint.

What are the materials used in building a gravity dam?

There are many gravity dams constructed of compacted earth. High dams are generally concrete. All dams require a spillway to be safe. The spillway must be armoured.

What does civil status mean?

Civil means like, when you do not get on with someone, but only talk when you have to. Alternatively, when you do talk you do not argue. Alternatively, if you are with someone who is of your both friends and family, you do not ruin it for them.

What are the functions of a column in a building?

A column is used to support the weight of the roof and/or the upper floors. Now days, many columns are used for decorative purposes. A column along with load bearing beams can support a lot of weight.

What is the function of packing materials in the joint of concrete pipes in pipe jacking?

Packing materials are about 10 mm to 20 mm thick and are normally made of plywood, fibreboard or other materials. In case packing materials are absent in pipe joints for pipe jacking, then any deflection in the joints reduces the contact area of the concrete and it leads to spalling of joints due to high stresses induced. With the insertion of packing material inside the pipe joints, the allowable deflection without damaging the joint during the pipe jacking process can be increased.

For drained reclamation, what is the significance of smear zone induced by installation of band drains?

During installation of band drains, smear zones are created in which zones of soil surrounding the band drains are disturbed. The compressibility of surrounding soils is increased and it results in the reduction of their permeability. In fact, the surrounding soils are remoulded during the installation process and the effectiveness of band drains is reduced. In essence, for the reduced permeability of soils around band drains, it takes longer time to complete the consolidation process.

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.

In selecting screw pumps in polder scheme projects, what are the factors that affect the design capacity of screw pumps?

The commonly used angles of inclination for screw pumps are 30°, 35° and 38°. For screw pumps of relatively high lifting head, like over 6.5 m, angle of inclination of 38° is normally used. However, for relatively lower head and high discharge requirement, angle of inclination of 30° shall be selected. In general, for a given capacity and lifting head, the screw pump diameter is smaller and its length is longer for a screw pump of 30° inclination when compared with a screw pump of 38° inclination.

To increase the discharge capacity of screw pumps, a larger number of flights should be selected. In fact, screw pumps with 2 flights are more economical that that with 3 flights in terms of efficiency and manufacturing cost. Moreover, the discharge capacity is also determined by the screw pump diameter and sizes of 300 mm to 5000 mm are available in current market.

What is the load transfer mechanism for paving blocks in pedestrian footway?

In Hong Kong, footway is normally designed with paving slabs/interlocking blocks instead of concrete because the extensive use of concrete in pavement is boring. Moreover, poor appearance will result in concrete pavement due to frequently trench openings for utility work.

In addition, owing to the prolonged setting and curing time of concrete, the use of concrete pavement inevitably generates disturbance to the general public.

The pedestrian loads are taken up through the following ways:

Load carrying capacity of paving slabs/interlocking blocks are derived from their individual strength;
Pedestrian loads are also supported by interlocking forces provided by friction transfer through the sand in vertical joints (K. K. Tang & Robert P. Cooper (1986).

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:

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)

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)

If the construction of concrete carriageway is carried out in summer, can expansion joints be omitted?

If the construction of concrete carriageway is carried out in summer, expansion joints may not be necessary as suggested by Arthur Wignall, Peter S. Kendrick and Roy Ancil. Expansion of concrete carriageway is mainly due to seasonal changes with an increase in temperature from that during construction to the ambient temperature (i.e. the temperature in summer).

However, if the construction of concrete carriageway takes place in summer, the concrete carriageway will undergo contraction in the following winter, thus the space available in contraction joints can accommodate the future expansion in the next summer.

Why are steel tubular marine piles often driven open-ended?

In marine structures where piles are constantly subject to significant lateral and uplift forces induced by berthing operation and wave action, it is necessary to drive the piles to much greater depth. To avoid premature refusal so that insufficient soil cover may develop which is incapable of providing the required lateral and uplift resistance, tubular piles are normally driven open-ended so that they are driving to greater depths than piles with closed ends.

What is the difference between engineering stress and true stress?

In biology, Stress is something that disrupts homeostasis of an organism. In engineering, Stress is an external force that pushes, pulls, twists, or otherwise puts force on something.

Engineering stress assumes that the area a force is acting upon remains constant, true stress takes into account the reduction in area caused by the force.

Why are high and narrow beams not desirable in concrete piers?

Based on past experience in other countries (Carl A. Thoresen (1988)), high and narrow beams after several years of construction showed signs of serious deterioration at the bottom of the beams. However, the deterioration of pier slabs was not significant when compared with that of the deep beams. The main reason to account for this is due to the close proximity of the deep beams to the sea level. To avoid these problems, either beamless slab or wide with shallow beams are normally designed.

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.

Geotechnical Instrumentation is frequently employed for monitoring the condition of reclamation. Sometimes two piezometers are installed inside the same borehole. What is the reason behind this?

For standpipes, they normally contain one plastic tube between its intention is to measure water level only. However, for piezometers, they are used for measuring pore water pressure in a certain depth below ground. For instance, if there are two clayey layers below ground at different depths, a multiple piezometer including two separate piezometers may be sunk at the same borehole to determine the pore water pressure at these layers respectively.

This arrangement has the advantage that it saves the cost of installation of separate boreholes for several piezometers. However, the installation of multiple piezometers within the same borehole is affected by occurrence of leakage along the pipes as suggested by Marius Tremblay (1989).

What do you mean by honeycomb in concrete?

Some people call it an air pocket in the concrete or a void.

In the construction of pump troughs for accommodation of screw pumps, what is the construction method to ensure close contact between the screw pumps and the pump trough?

In the construction of screw pump troughs, trapezoidal-shaped troughs are usually formed by using normal formwork. In order to enhance close contact between screw pumps and troughs, upon lifting the screw pumps into the troughs screeding works is carried out.

Screw pumps are set to rotate and screeds are placed between the gap of screw pumps’ blade and trapezoidal-shaped troughs during the rotating action of screw pumps. After the screed sets, it serves to prevent leakage of water during the pumping operation of screw pumps.

How did street originate in the plumbing term street ell?

A “street ell” may have gotten its name because it describes a 90 fitting particularly useful in tight, street ditches. When installing water pipes under a street, or from a water service, again under the street, into a home or business, this street ell allows one to change pipe direction with one less fitting, and in less space, than with a standard ell.

In General Specification for Civil Engineering Works (1992 Edition), it specifies the temperature requirements for bituminous material during and after mixing. What is the reason behind this?

Temperature is one of the factors that govern the compaction of bituminous material and the air void content is found to decrease with an increase in compaction temperature. This phenomenon is explained by the viscosity-temperature relations: the higher is the viscosity of binders, the greater is the resistance to compaction. Therefore, in normal contract for bituminous laying, the temperature requirements for bituminous material during and after mixing are specified.

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.

What is the function of a separation membrane between concrete pavement slab and sub-base?

The separation membrane between concrete pavement slab and sub-base has the following functions:
It aids in reducing the frictional forces between concrete slab and sub-base and helps to movement of concrete slab with respect to sub-base owing to changes in temperature and moisture.
It prevents the loss of cement and water in immature concrete which significantly affects the strength and durability of hardened concrete.
It avoids the mixing up of sub-base materials and freshly placed concrete.
Polythene sheeting, which is a waterproof material, is commonly used as separation membrane.

Why was the Empire State Building made of steel?

Strength – Steel is very strong

Flexibility – Ability to flex in the wind

Cost – Inexpensive and fast to build; Prefab construction

Concrete, a possible alternative, has less compressive strength than steel. The bottom support structure of the empire state building would consist of a large percentage of solid concrete simply to support the weight of the building.

Why is sulphate-resisting cement not used in marine concrete?

The main components of Portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. In sulphate-resisting cement, it contains a low amount of tricalcium aluminate in order to avoid sulphate attack.

Otherwise, tricalcium aluminate would react with sulphates to form calcium sulphoaluminate and gypsum that cause expansion and crack the concrete structure.

However, for marine concrete sulphate-resisting cement should not be used because tricalcium aluminate has high affinity for chloride ions. This is based on the possible reaction of chloride ions and tricalcium aluminate to form calcium chloroaluminate hydrate as suggested by P. Kumar Mehta (1991) and the reduction of which may increase the rate of chloride attack to the concrete marine structure and result in faster corrosion of steel reinforcement in marine structures.

What black man invented the clothes dryer?

George T. Sampson

Would you cause a 55 gallon drum of water to weigh more by climbing in?

A person will sink in water if he is not holding enough air in his lungs to keep him floating. Therefore, the person weighs more than the amount of water that he will displace.

Is it worthwhile to carry out tests on particle density of soil particles for geotechnical design?

Particle density of soils is defined by the ratio of soil particle mass and soil particle volume. Depending on soil types, the range of variation of soil particle density varies not significantly, i.e. by 4%. Therefore, it may not be worthwhile to order laboratory tests and incur additional expenditure just to determine the particles density by recognizing that the variation of particles density is not significant.

What is the withdrawal force of steel nails?

In engineering, the code allowable withdrawal force is zero, because the wood expands and contracts over time and the nail pullout force can reduce to zero.

Are there any differences in the methods of compaction between clayey soil material and sandy material?

As suggested by Lars Forssblad (1981), the three main actions of compaction are static pressure, impact force and vibration. Different compactors contain one or more modes of these actions. For example, vibratory tampers perform mainly by the principle of impact while vibratory rollers work with principle of static pressure and vibration.

For sandy soils, vibration is adequate for normal compaction because the action of vibration sets the soil particles in motion and friction forces between soil particles are virtually demolished. During this vibration motion, the soil particles rearrange themselves to develop a dense state.

For normal soils, it is necessary to combine the action of vibration together with static pressure to breakdown the cohesion forces between soil particles in order to allow for better compaction. The static pressure of vibratory machines is adopted to exert a shearing force to eliminate the cohesion in clayey soils.

Are kerbs necessary in road pavements?

In general, kerbs are essential in road pavements due to the following reasons (based on Arthur Wignall, Peter S. Kendrick and Roy Ancil):

They provide strength to the sides of road pavements and avoid lateral displacement of carriageway due to traffic loads.
In terms of road safety, they serve as a separation line between footway and carriageway and aid car drivers in driving safely.
They act as a vertical barrier to guide the surface runoff collected in road pavements to the gullies.

Can a wave happen in the middle of the ocean like in the movie Poseidon 2006?

Yes. Rogue waves have been known to capsize ships.

In connecting fenders to pier structures, should single lock nuts or double lock nuts be used?

In many pier structures the connection offenders to piers is achieved by using single lock nuts. However, they do not perform well because some timber fenders loosen more easily when subject to vibrating loads due to berthing, wave and tidal actions. To solve this problem, double lock nuts should be adopted as they prove to function satisfactory in other structural elements which are subject to frequent vibration loads.

Note: Double lock nuts mean two nuts are adopted in a single bolt connection between fenders and marine structures.

What are the different applications of draglines, backhoes and shovels?

An excavator is defined as a power-operated digging machine and it includes different types like shovels, draglines, clamshells, backhoes, etc.

A dragline possesses a long jib for digging and dumping and it is used for digging from grade line to great depths below ground. Its characteristic is that it does not possess positive digging action and lateral control of normal excavators. A dragline is normally deployed for bulk excavation.

A backhoe is designed primarily for excavation below ground and it is especially employed for trench excavation works. It digs by forcing the bucket into soils and pulling it towards the machine and it possesses the positive digging action and accurate lateral control.

A shovel is a machine that acts like a man’s digging action with a hand shovel and hence it is called a shovel. It digs by putting the bucket at the toe of excavation and pulling it up. Though a shovel has limited ability to dig below ground level, it is very efficient in digging above ground like digging an embankment.

What are the advantages and disadvantages of lead products in construction?

Disadvantages: Lead is very toxic; Its use can result in pollution of the ground and more importantly of water supplies. This leads to the contamination of drinking water and can cause hazards to human health as well as disrupting entire ecosystems.

Advantages: Because of its toxicity, lead is being bought less and less around the world, which of course results in the lowering of its cost. In addition, lead melts at a relatively low temperature, making it great for solder. However, recently the Chinese have shown an interest in buying mass quantities to manufacture batteries made from a base of lead so the price of this metal may soon rise.

In case a road passes through a reclaimed land and an existing land, what is the main concern regarding the design of pavements?

For an existing land, it is anticipated that there will be no major settlement within the design life of pavement structures. However, for a recently reclaimed land, even with surcharging and installation of vertical drains, some settlement will still occur after the construction.

If a road pavement has to be constructed connecting these two areas, special design has to be made in this transition region. In order to avoid the occurrence of differential settlement which may damage the pavement structure, a transition slab may be designed to accommodate such movement (J. S. M. Kwong (1996)).

What is the application of inverted siphons? What are the disadvantages of using inverted siphons?

Inverted siphons are designed at locations in which a sewer system is blocked by underground utilities or storm-water drains. They are sometimes called depressed sewers because it is claimed that there is no actual siphon action. They connect the upstream and downstream sewers with U-shaped vertical alignment such that they are always running full.
The drawbacks of inverted siphons are:
They induce additional head loss to the sewer system which is undesirable in hydraulic performance;
U-shaped siphons create sediment accumulation problem and previous experience showed that inverted siphons were easily blocked due to siltation;
Maintenance of invert siphons is difficult due to its inaccessibility.

What are the uses of Groynes?

They prevent, or slow down erosion, and stop long shore drift. This, however, can have bad knock-on effects somewhere near.

In selection of dams in drainage channels, what are the advantages of using rubber dams instead of steel-gate dams?

The advantages of rubber dams are as follows:
Since rubber is flexible in nature it is capable of performing deflation even in the presence of dirt and sedimentation on the downstream side. However, for rigid steel-gate dams, it may not be possible to open when there is excessive sediment.
Since the foundation of rubber dams is comparatively lighter than that of steel-gate dams, it saves both construction cost and time.
Rubber dams can be designed with longer spans without piers while steel-gate dams require intermediate piers for long spans.

What Tor stands for in Tor steel?

The owner’s last name

What is the purpose of carrying out water absorption test for pre-cast concrete pipes?

Cement will mix with more water than is required to eventually combine during hydration of cement paste. As such, some voids will be left behind after the hydration process which affects the strength and durability of concrete. With the presence of air voids in concrete, it is vulnerable to penetration and attack by aggressive chemicals.

Good quality concrete is characterized by having minimal voids left by excess water and therefore, water absorption test for pre-cast concrete pipes is adopted for checking the quality of concrete in terms of density and imperviousness.

What are the advantages of building a dam on the river Nile?

It is the same as building a dam on any river. Dams are built to control flooding downstream during the wet season, generate power year round, and provide irrigation in the dry season.

What are the functions of slip joints in block-work seawalls?

Slip joints are joints which are formed through a complete vertical plane from the cope level to the toe level of seawalls. These joints are designed in block-work seawalls to cater for possible differential settlements between adjacent panels of seawalls. The aggregates inside the half-round channels in slip joints allow for the vertical movements induced by differential settlement and at the same time providing aggregate interlocking forces among adjacent panels of seawalls to link the panels in one unit against the lateral earth pressure exerted on seawall.

Besides, slip joints provide a path for the relief of water pressure developed and allow the lateral movement (e.g. contraction) due to seasonal variations.

Will going from a 3-tap to 6-tap increase water pressure?

No, the pressure will be the same; you will get more volume only if your pumps can handle the GPM, to increase pressure you may need a booster pump or a single pump that is rated for your needs.

Should joints of concrete kerbs be in line with the joints in concrete carriageway?

In normal practice, joints are provided in road kerbs to cater for concrete expansion and contraction. However, the location of joints in kerbs is not arbitrary and they should match with joints in concrete carriageway. Otherwise, it is very likely that cracks may form in concrete kerbs at location of pavement joints (Ministry of Transport (1955)).

In case mud waves occur during reclamation, what are the possible solutions to rectify the situation?

Option 1 – Complete Removal of All Disturbed Mud: To remove all disturbed mud once mud waves occur is the fastest way to treat the problem. After that, filling material is used for replacing the disturbed mud. However, this option is a rather expensive option because it involves dredging of all disturbed mud and replacement of large amount of fill.

Option 2 – Accelerated consolidation of Disturbed Mud: This option involves placement of surcharging loads on top of mud waves, together with installation of band drains to accelerate the consolidation of disturbed mud. This method suffers from the drawback that sufficient long time is required for the consolidation process of mud.

Option 3 – Partial Removal of Disturbed Mud: This option is a combination of the first two options in which the top weak layer of mud is removed while the lower mud is treated with surcharging with band drain installation.

Note: Mud waves refer to excessive displacement of mud due to successive slip failure during reclamation.

For compaction of free-draining sands or gravels, what is the optimum moisture content to achieve maximum density?

The compaction curve of sandy materials is totally different from that of clayey materials. For sands or gravels, there are two situations of maximum density, namely the completely dry condition and the complete water saturation. For moisture content of sands and gravels between these two states, the dry density obtained is lower than that obtained in the above-mentioned states.

The presence of capillary forces account for the difficulty of compaction sand at water contents between virtually dry and saturated state. They are formed in partially filled water void between soil particles and perform as elastic ties cementing soil particles together. Reference is made to Lars Forssblad (1981).

The compaction curve for clay is suitable for the majority of soil types except sands and gravels because a small amount of clay in soils is sufficient to make the soils impermeable.

What is the world’s 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 for conducting pull-out tests for soil nails?

There are mainly four reasons for this test:
To check and verify the bond strength between soil and grout adopted during the design of soil nails. This is the main objective of conducting soil nail pull-out test.

To determine the bond strength between soil and grout for future design purpose. However, if this target is to be achieved, the test nails should be loaded to determine the ultimate soil/grout bond with a upper limit of 80% of ultimate tensile strength of steel bars.

To check if there is any slippage or creep occurrence.

To check the elastic and plastic deformations of test nails. This is observed during the repeated loading and unloading cycles of soil nails.

Note: Pull-out tests are carried out by applying specified forces in an attempt to pull out the constructed soil nails.

In Hiley’s formula for driven piles i.e. R = E/(s + 0.5c), why is a coefficient of 0.5 applied for the term elastic deformation of piles and soil?

Hiley’s formula is based on the principle of energy conservation in which the energy brought about by hammers during the action of hitting are transferred to piles in ground. When the hammer force and displacement is plotted, the energy absorbed by piles is the area under the curve. Since the curve of elastic component is linear with a positive slope, the area i.e. energy should be the area of triangle (0.5 × R × c) where ‘R’ is reaction force and ‘c’ is elastic compression due to helmet, piles and soil system. For settlement, it is of horizontal line in force-displacement diagram and hence the energy transferred to pile-soil system is (R × s).

In designing sewer pipes, why are vitrified clay pipes commonly used for pipe size less than 600 mm while precast concrete pipes with PVC lining is used for pipe size exceeding 600 mm?

The market price of vitrified clay pipes is generally less than that of precast concrete pipes with PVC lining. Therefore, for small size of pipes (pipe diameter less than 600 mm) it is more economical to use vitrified clay pipes. However, vitrified clay pipes do suffer from the problem of brittleness and its effect is even severe for larger size of pipes.

Moreover, it is rather time consuming to deliver clay pipes products because the majority of them are manufactured in Europe. Hence, for larger size of sewer pipes (diameter more than 600 mm) it is customary to use precast concrete pipes with PVC lining.

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 are the considerations in selecting marine plants and land plants for installation of band drains?

For installation of band drains by marine plants, it must have sufficient water depth to accommodate the marine plants in the first place. However, due to the effect of tides and waves, the establishment of the position for installation of band drains and the subsequent installation works may be affected. In addition, the establishment cost of marine plants is higher than that of land plants.

For installation of band drains by land plants, difficulty may be encountered during the installation of band drains through the reclaimed layer e.g. C&D material. Land plants may take longer construction time due to the above-mentioned difficulty. Sometimes when the supply of public fill is increased suddenly, it may be preferable to place these fill immediately into position and in this situation the installation of band drains (originally installed by marine plants) is delayed so that the construction of band drains is changed to using land plants.

What is the distance between railway tracks?

In U.S, its 4 feet and 8.5 inches
In India, its 5 feet 6 inches

Why are most marine piles circular in cross section?

For marine piles, there are several options available for selection, namely H-piles, circular pipes and box piles. However, only circular piles and box piles are suitable for marine application because of the following two reasons suggested by G. M. Cornfield (1968):

Circular piles and box piles possess high column buckling strength. For marine structures like jetties, piles are well above seabed level and therefore the column buckling effect is significant when compared with other structures. Therefore, it is essential to use pile sections which have relatively high buckling strength in piers.

Circular piles and box piles display high energy absorbing capability. For marine structures like dolphins and fenders, which require substantial amount of berthing energy to be absorbed, these piles sections are inevitably good choices. In marine structures, it appears that circular sections prevail over the box sections. The main reason is that the range of section available for selection of circular piles is more than that of box piles.

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 the mechanism of cavitation in pipes and drains?

Cavitation refers to the formation of air bubbles in fluid in low-pressure condition which is lower than the saturation pressure. It is a potentially damaging condition in which the fluid in pipes or sewers is at high velocities. By Bernoulli’s Equation, at high flow velocities, the pressure head of fluid is reduced accordingly.

As the fluid pressure is less than saturation pressure, dissolved gases are released from the fluid and these air bubbles will suddenly collapse when the flow enters into a region of higher pressure. This produces a high dynamic pressure which causes damage to the pipelines due to its high frequency.

What is the importance of geo-textiles and sand in reclamation works?

For geo-textiles used in reclamation, they serve mainly the following two purposes:

They separate reclamation fill from marine mud;
They may act as reinforcement to enhance the stability of reclamation. However, the reinforcement function is still under heated debate because its performance as reinforcement depends on several factors like the directional strength of woven geo-textiles and damage effect by installation of vertical band drains.

For sand:

It spreads the load of future public dump on top of it;
It acts as drainage path for dissipation of excess pore water pressure for band drain installation.

Why is the statue of liberty made of copper?

Copper is a very durable material when exposed to weather and is soft enough that it can be easily molded to curved shapes such as those in the Statue of Liberty. It is also traditionally used in buildings for complex roofs, so there would have been trades people available trained to use it.

Other metals that can be molded are lead but it does not have the attractive verdigris color, and gold much is more expensive

Why is shallow bedrock condition unfavourable for open berth piers?

The most severe load on piers generally is the horizontal load due to berthing of large vessels. Since the widths of open berth piers are relatively small so that they provides a short lever arm to counteract the moment induced by berthing loads. Moreover, the dead load of open berth piers are normally quite light and therefore the resisting moment provided by the dead load of pier structures may not be sufficient to counteract the moment generated by berthing loads.

To aid in providing adequate resistance to the overturning moment by the berthing load, the soil resistance above bedrock contributes to stabilizing moment. For commonly adopted marine piling type, i.e. driven steel tubular piles with reinforced concrete infill, driven piles can at most be founded on top of rock-head surface. In case the rock-head level is shallow, then the little soil cover may result in insufficient lateral resistance to the berthing load.

Where is the world’s longest elevator and how long is it?

Gold mines in South Africa go a few kilometers below the surface. The world’s deepest mine now is the Mponeng, is a gold mine in South Africa’s North West Province. It extends over 4 kilometres below the surface, and is considered to be one of the most substantial gold mines in the world. The lift itself descends 3037 m to a point 1200 m below sea level.

Should dolphins be designed in a rigid manner, i.e. resting on several raking piles?

In designing dolphins, they are normally supported on a system of three to four raking piles. This in essence is a rigid structure and exhibits little flexibility e.g. movement against impact and berthing loads by vessels. In fact, this kind of design may not be desirable in terms of maintenance because the dolphins are readily susceptible to damage by high berthing vessels.

To rectify this situation, some energy absorption devices like rubber/plastic fenders have to be installed to reduce the impact load deriving from its own deflection. On the other hand, by designing dolphins as flexible structures capable for allowing slight deflection, it helps to reduce the large forces generated during berthing of vessels.

In this connection, one way of designing dolphins as flexible structures is by provision of a single pile only.

For a rigid structure, it takes up external loads without undergoing excessive deformations.

Who built the sears tower?

While he did not build the structure (he died in l959), there is some evidence the idea was suggested under a different name (Illinois Building) by Frank Lloyd Wright, one of the few true skyscrapers in which he had a role. The original design for the Illinois Building would have topped off at 5,280 Feet! The Swears tower is a quarter of this at most, but there are similarities.

What is the strongest bridge for a school contest?

If you are making a spaghetti bridge, bunch it all together in a triangular prism or a big brick and just fill the gaps with Paste.

Why are intermediate jacks designed in some pipe jacking projects?

When the process of pipe jacking stops, building up of resistance is very fast in some soil. For instance, increase in jacking force of 20%-40% is required for a stoppage of pipe jacking for just several hours. Hence, it is recommended that pipe jacking should be carried out in a continuous operation.

For a long pipeline, the frictional forces established between the jacking pipes and soil is high. Sometimes, such resisting forces may be so high that they can hardly be overcome by the jacks in jacking pits. Moreover, even if the jacks can overcome the high frictional forces induced during jacking, high loads are experienced in jacking pipes during driving. Jacking pipe’s material e.g. concrete may not have sufficient strength to resist these stresses and hence pipe strength is another factor that governs the need for consideration of using intermediate jacks.

What is the best type of wood glue?

Noob

What is the purpose of adding cooling pipes or even using cold water for concrete in concreting operation?

All these measures aim at reducing the placing temperature and reducing thermal cracks induced during concreting of massive pours. Since the final concreting temperature should be the ambient temperature, reducing the initial placing temperature will also lower the peak hydration temperature. Therefore, the temperature difference between the hydration peak and the ambient temperature is reduced accordingly and subsequently the thermal effect to concrete structure can be reduced by controlling the placing temperature.

What are the advantages of using top-down approach in basement construction?

The advantages of top-down approach are listed below:
The structures above ground can be carried out simultaneously with the structures below ground. This greatly reduces the time for construction.

By using this approach, settlement can be reduced.
Since the permanent columns and slabs can be utilized to support loadings during construction, it saves the cost of form-work.

Note: Top-down approach means construction of basement is carried out from ground level downwards.

In selection of waterstop, shall engineers use plain dumb-bell type or center-bulb type?

The plain dumb-bell type is used for joint location where small movements are anticipated.
Therefore, construction joints are desirable locations of this type of waterstop. On the other hand, center-bulb type water-stop is suitable for expansion joints or locations where lateral and shear movements occur due to settlement or deflection. Reference is made to W. L. Monks (1972).

Why are two gate valves required in normal practice to form a washout valve?

In fact, the situation is analogous to that of fire hydrants in which two gates valves are installed with a single fire hydrant. Washout valves are used for normal maintenance work of watermain like allowing flowing out of water during cleaning of watermain. At the junction where a tee-branch out to a washout point, a gate valve is installed to separate the two pipelines.

However, this gate valve is open during normal operation while another gate valve further downstream is installed (closed during normal operation). If the downstream gate valve is not installed in position, then the pipe section of branched-out watermain will be left dry during normal operation and there is a high probability that damage to watermain and frequent leakage would occur.

With the downstream gate valve installed, the segment of branched-out watermain contains water in normal operation. In case there is any leakage, it can be readily detected by using the two gate valves.

What is an ice dam sock?

If you have never used a ice dam melting sock on your roof before, you will find that they provide an inexpensive method for removing roof ice dams and improving your home’s heating efficiency. Roof ice dams are an annoying source of roof damage, leaks, and heat loss in the winter. The main causes are drip melt from improperly capped warm air vent pipes and poor roof insulation.

Laying a ice melt sock onto the roof so it crosses the ice dam and overhangs the gutter, will melt through the snow and ice and create a channel for water to flow down into the gutters or off the roof. If done properly those ice sickles that form as the snow melts from the edges of the gutters will never appear, they too are a cause of much damage and are dangerous to life and limb.

In concrete compression test, normally 150 mm × 150 mm × 150 mm concrete cube samples is used for testing. Why isn’t 100 mm × 100 mm × 100 mm concrete cube samples used in the test instead of 150 mm × 150 mm × 150 mm concrete cube samples?

Basically, the force supplied by a concrete compression machine is a definite value. For normal concrete strength application, say below 50MPa, the stress produced by a 150 mm × 150 mm × 150 mm cube is sufficient for the machine to crush the concrete sample.

However, if the designed concrete strength is 100MPa, under the same force (about 2,000 kN) supplied by the machine, the stress under a 150mmx150mmx150mm cube is not sufficient to crush the concrete cube. Therefore, 150 mm × 150 mm × 150 mm concrete cubes are used instead to increase the applied stress to crush the concrete cubes.

For normal concrete strength, the cube size of 150 mm × 150 mm × 150 mm is already sufficient for the crushing strength of the machine.

In pipe jacking/microtunneling, it is commonly accepted that cover depths of jacking pipes cannot be too shallow (i.e. less than 2D where D is the diameter of jacking pipes). Why?

For pipe jacking/microtunneling, the causes of large settlement are loss of face stability, failure to stabilize ground around shafts, presence of annular space around pipes and shield, drag along pipe joints, etc. The settlement mechanism of shallow depths of pipe jacking/microtunneling is the formation of a settlement trough on top of the jacking pipes.

The width of the trough depends on soil properties; the larger is the cover depth of jacking pipes, the larger is the width of settlement trough. For the same soil volume loss due to pipe jacking/microtunneling, the width of settlement trough for shallow cover depth is smaller and therefore it results in a larger vertical maximum settlement.

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 is the mechanism of protection by hot dip galvanizing?

Hot dip galvanizing protects steel/iron from corrosion by:

It forms a metallic zinc and zinc-iron alloy coating on top of steel surface. This zinc coating reacts with moisture in atmosphere to from zinc salts which act as an insulating layer for steel/iron.
Zinc is higher than steel/iron in the galvanic series and when these dissimilar metals with different electrical potential are in contact, the zinc anode corrodes and offers sacrificial protection to steel/iron and hence steel/iron is protected from corrosion.

Comparing the rate of “Formwork exceeding 300 mm wide, horizontal or at any inclination up to and including 5° to the horizontal” with the rate of “Formwork exceeding 300 mm wide, at any inclination more than 85° up to and including 90° to the horizontal”, which one is higher?

The item “Formwork exceeding 300 mm wide, at any inclination more than 85° up to and including 90° to the horizontal” refers to formwork formed vertically and when compared with formwork erected in horizontal plane, the amount of false-work required is smaller.

The item “Formwork exceeding 300 mm wide, horizontal or at any inclination up to and including 5° to the horizontal” refers to formwork to be erected in horizontal position and in general it requires much false-work to support this type of formwork. Therefore, the rate for this item is higher than the one mentioned in the above paragraph.

In pre-stressing work, if more than one wire or strand is included in the same duct, why should all wires/strands be stressed at the same time?

If wires/strands are stressed individually inside the same duct, then those stressed strand/wires will bear against those unstressed ones and trap them. Therefore, the friction of the trapped wires is high and is undesirable.

What is a kip?

1 kip = 1000 lbs

What is the difference between fasteners, bolts and screws?

Fastener is a general term to describe something which is used as a restraint for holding things together or attaching to other things.

The main physical distinction between screws and bolts is that screws are entirely full of threads while bolts contain shanks without threads. However, a better interpretation of the differences between the two is that bolts are always fitted with nuts. On the contrary, screws are normally used with tapped holes.

How do you measure concrete?

Cubic feet, Cubic yards, Cubic Meter

What are the advantages of piers constructed monolithically with the bridge deck over usage of bearings?

Basically, piers constructed monolithically with the bridge deck are advantageous in the following ways:
Movement of the bridge deck is achieved by the bending deformation of long and slender piers. In this way, it saves the construction cost of bearings by using monolithic construction between bridge deck and piers.

Moreover, it is not necessary to spend extra effort to design for drainage details and access for bearing replacement. On the other hand, in maintenance aspect substantial cost and time savings could be obtained by using monolithic construction instead of using bearings as bridge articulation.

Monolithic construction possesses the shortest effective Euler buckling length for piers because they are fixed supports at the interface between bridge deck and piers.

Note: Monolithic construction means that piers are connected to bridge decks without any joints and bearings.

What is braced excavation all about?

Excavations are braced to prevent the cavein of surrounding unstable soil.

In the design of pipe jacking, what particular areas on pipe joints should engineers take care of?

Since in pipe jacking, the jacked pipes could hardly be jacked in the designed level and alignment and some deviation from the original one is commonly acceptable provided that the deviation are within the tolerance of the Contract. However, in order to avoid damage made to the pipe joints due to over-stressing, it is necessary to estimate the stress concentrations resulting from these angular deflections.

Note: Pipe jacking is a trenchless method in which pipes are jacked underground from jacking pits and receiving pits.

In the design of service reservoirs, how are reservoir floors designed to prevent leakage of water due to seasonal and shrinkage movements?

There are in general two main approaches in designing floors of service reservoirs:
In the first method, movement joints are designed in each panel of reservoir floors so that they can expand and contract freely. Each panel is completely isolated from one another and a sliding layer is placed beneath them to aid in sliding.
The second method, on the contrary, does not make provision to free movement. Due to seasonal and shrinkage movements, cracks are designed to occur in the reservoir floors such that very tiny cracks are spread over the floor and these cracks are too small to initiate corrosion or leakage. However, in this case, the amount of reinforcement used is much larger than the first approach.

In erection of false-work, for a rectangular panel inside a false-work should it be braced along the two diagonals?

When a rectangular panel is subject to an eccentric load or a lateral load, it tends to deform into a parallelogram with one diagonal shortening and the other elongating. Theoretically, it is sufficient to brace along one of the diagonals (the one in tension).

If one diagonal is only allowed to brace inside the rectangular panel, it should be not braced in the diagonal in compression because under severe lateral loading the diagonal may buckle leading to failure of structure.
However, in actual situation lateral loads may come from both sides of the panel and hence it should be braced in both diagonals.

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 aluminium. This simply translate that aluminium is 3 times flexible than steel.

What are the functions of different components of paint?

For normal paint application, there are mainly three main components of paint, namely primer, undercoat and finishing coat.

Primer: This is the first layer of a typical painting system and it is used to inhabit corrosion and provide a good bond for subsequent coats.

Undercoat: This component acts as a barrier to corrosion agents and even out irregularities of bonding surface. It also serves to hide the underlying background and prevent the details and colour of the area of application to affect the designed colour and finishing details of paint.

Finishing coat: This is the final layer of a typical painting system and it protects the underlying layers from the effect of adverse weather conditions (e.g. sunlight) and to provide the designed properties of paint like colour, impermeability, wearing resistance, etc.

Why is the span length ratio of end span/approach span to its neighboring inner spans usually about 0.75?

From aesthetic point of view, an odd number of spans with a decrease in length in the direction of abutment is desirable. Moreover, spans of equal length are found to be boring. However, the arrangement of irregular span lengths is not recommended because it gives a feeling of uneasiness.

From structural point of view, for a multi-span bridge with equal span length, the sagging moment at the mid-span of the end span/approach span is largest. In order to reduce this moment, the span length of end span/approach span is designed to be 0.75 of inner spans. However, this ratio should not be less than 0.40 because of the effect of uplifting at the end span/approach span support.

Note: End span refers to the last span in a continuous bridge while approach span refers to the first span of a bridge.

What is the tallest man made structure in the world?

The tallest artificial structure is Burj Khalifa, a skyscraper in Dubai that reached 829.8 m (2,722 ft) in height on January 17, 2009. By April 7, 2008 it had been built higher than the KVLY-TV mast in North Dakota, USA.