Civil Engineering: January 2018

Wednesday, 31 January 2018

Total Station Preparation before Measurement

Preparation before Measurement

Setting up the instrument:

(1) Set up the tripod first: extend the extension legs to suitable lengths and tighten the screws on the legs.Make sure the legs are spaced at equal intervals and the head is approximately level. Set the tripod so that the head is positioned over the surveying point. Make sure the tripod shoes are firmly fixed in the ground.

(2) Attaching the instrument on the tripod head: mount the instrument carefully on the tripod head. Supporting it with one hand, tighten the centering screw on the bottom of the unit to make sure it is secured to the tripod.

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Levelling-Up:

(1) Basic Levelling-Up with the circular level

1). Move the foot screws A and B in opposite direction till

the circular bubble is perpendicular to a line shaped with

screw A and B. The direction of

rotation in left thumb indicates the

movement of the circular bubble.

2). Move the bubble to the center of the circle by turning

(2) Accurate Levelling-Up with plate level

1). Loosen the horizontal motion clamp, and turn the instrument till the plate level is parallel to a line shaped with screws A and B. Adjust the screws A and B to make the bubble in the center of the level.

2). Loosen the horizontal motion clamp, and turn the
instrument approximately 90°.Adjust the screw C until the bubble in the center of the level.

3). Repeat above steps until the bubble remains in the

center of the plate level while the instrument is

rotated to any position.

(3) Accurate Levelling-Up with Electronic Level on the screen

It is convenient for W-1500 N series to level-up with electronic level, especially when it is difficult to observe the circular level and plate level.
Firstly, press the key 【★】 to turn on the electronic bubble as shown in left figure.On the electronic bubble screen, five function keys are displayed in the left column, which are listed as follows:

【TiltXY】dynamic display of electronic bubble

【T.P】observation and setting of temperature and atmospheric pressure

【Target】target condition of surveying

【Battery】dynamic display of battery level

【Exit】exit the electronic bubble screen

Secondly,level it by turning three foot screws and ensure the bubble is in the plate level.Make sure the red spot is in the center.

Note:

As shown in the right figure, you can realize transformation of compensation options by pressing the lower right button.

【XYON】compensate horizontal angle and vertical angle at the same time

【XONYOFF】just compensate X axis

【XYOFF】don’t compensate X axis and Y axis

【A.OFF】don’t compensate X axis and Y axis,and turn off the popup function of electronic bubble.

In PENTAX Field Genius software, the Level display is always shown as left figure.

(4) Centering

Centering with Laser Plummet:

Press the key 【★】 to enter into the display as shown in the left figure.

Operation Steps:

① Click the “target” button and you can turn on laser plummet and set it as three levels of brightness. Thus, that laser emits downwards can be seen.

② Loosen the center screw of tripod, and move the base plate on tripod head until the laser spot coincides with ground mark point. Then tighten the center screw.

③ Repeat leveling and two steps until the instrument keeps leveling and the laser spot coincides with ground mark point when rotating "alidade" of instrument in any direction.

④ After centering is finished, turn off laser plummet for power saving.

For "Instrument settings" read next Post.

Thanks for Reading

Wednesday, 24 January 2018

Safety Precautions for pentax w1502n

PRECAUTIONS REGARDING SAFETY

Safety Precautions (Must be followed)

The following items are intended to prevent possible injury to the user or other people and /or damage to the instrument before it occurs. These safety precautions are important to the safe operation of this product and should be observed at all times.

Distinctive Displays

The following displays are used to distinguish precautions by the degree of injury or damage that may result if the precaution is ignored.

WARNING

Items indicated by this display are precautions which if ignored would result in serious injury.

CAUTION

Items indicated by this display are precautions which if ignored may result in injury or material.

●　Here “injury” refers to injuries such as cuts, burns or electric shock the treatment of which will not likely require hospitalization or long-term attention.

●　“Material damage” refers to damage to facilities, buildings, acquired data, etc.

Before using this product, be sure that you have thoroughly read and understood this instruction manual to ensure proper operation. After reading this manual, be sure to keep it in a convenient place for easy reference.

This instrument complies with the protection requirement for residential and commercial areas. If this instrument is used close to Industrial areas or transmitters, the equipment can be influenced by electromagnetic fields.

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WARNING

Do not stare into the laser beam directly as this may result in damage to your eyes.

W-1500 N series is a Class IIIa (3R) laser product.

Do not look into the laser radiation aperture directly as this may result in damage to your eyes.

Never use the telescope to view intense light such as direct sunlight or sunlight reflected through a prism as this may result in loss of sight.

Do not disassemble, modify or repair this product as there a risk of laser radiation.

Do not aim the laser beam at a person as it is harmful to the eyes and body. Receive the examination treatment by the doctor when the eyesight or body trouble is doubted by any chance.

●　Electro-Magnetic Compatibility (EMC):

This instrument complies with the protection requirement for residential and commercial areas. If this instrument is used close to industrial areas or transmitters, the equipment can be influenced by electromagnetic fields.

●　Do not use this product in a coal mine, in a location where there is coal dust, or near flammable material as there is a risk of explosion.

●　Do not disassemble, modify or repair this product as there is a risk of fire, electric shock and burn injury. If you think the product requires repair, contact the retail outlet where you purchased it or an authorized repair site.

●　Only use the BC05 battery charger intended for this product as the battery charger. Use of another battery charger entails a risk of fire or burn injury from the battery bursting into flames due to possible differences in voltage or polarity.

●　Do not use a damaged electric cord plug or loose electric outlet when charging as there is a risk of fire or electric shock.

●　Do not charge the battery while covered by clothes or similar item as there is a risk of fire if the clothes ignite.

●　Do not use the battery or charger when wet as there is a risk of fire and burn injury due to short-circuit.

●　To prevent making short-circuit when removing the battery and charger from the case and storing them, apply electrically resistant tape to the poles of the battery. Storing the battery and charger as-is may result in fire or burn injury due to short-circuit.

●　Do not throw the battery into fire or expose it to heat as there is a risk of injury if it explodes

CAUTION

For safety, please do the opening inspection and inspection every a fixed period and adjustment.

When the laser beam enters eyes, an unexpected accident might be caused by the blink of eyes. Establish the laser product to avoid the height of eyes of a driving person and walker.

Establish an instrument so that laser beam does not hit a reflection thing as a mirror and a glass window. The refection beam of the laser is also harmful to the human body.

Besides the time when you measure the distance, cut off the power supply or shade the beam of aperture with caps.

Keep the laser product in the place where the person who does not have the product knowledge such as children does not touch by mistake.

Destroy the power supply mechanism of the instrument so as not to emit the laser beam at the time of disposal.

● Do not remove the handgrip without good reason. If it does come off, be sure to attach it securely to the instrument with screws. If it is not fastened securely, the instrument may fall when you grasp the handgrip, leading to possible injury.

● Do not short the poles of the battery or charger as there is a risk of injury or fire.

● Do not touch any fluid which may leak from the battery as there is a risk of chemical burn injury or reaction.

● Do not insert or remove the electric plug with wet hands as there is a risk of electric shock.

● Do not use the case to stand on as it is slippery and unstable and may cause you to fall, resulting in possible injury.

● Be sure the tripod itself and the instrument on the tripod are both installed securely as insecure installation may cause the tripod to fall over or the instrument to drop, resulting in possible injury.

● Do not carry the tripod with the metal shoe pointing toward another person as the person may be injured if they strike him or her.

● The instrument contains a rechargeable battery and it is rechargeable.

● At the end of its useful life, it may be illegal to dispose of the battery.

● Check with your local solid waste officials for details for recycling.

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Tuesday, 9 January 2018

Air bubbles voids and Effects in Concrete

اس کو اردو یا (اپنے زبان ) میں پڑھنے کیلئے ٹرانسلٹ پر کلک کریں اور آپنا زبان متخاب کریں۔

To read this in Urdu or ( in your won language) just select from Translator in side bar.

Why is there air in concrete?

Small, well-dispersed air voids in concrete can improve workability, reduce bleeding and segregation, and improve resistance to freezing and thawing.

Air is always present in concrete mixes. It is intentionally or unintentionally trapped in fresh concrete as a result of mixing and placing. About the only way to avoid trapping some air would be to mix, transport, and place concrete in a vacuum side, just like the addition of sand makes the total aggregate gradation finer. These chemical admixtures stabilize and retain more of the smaller bubbles trapped during mixing and agitating. These finer bubbles become the more desirable part of the air void system. The coarser bubbles randomly trapped during mixing and placing is generally present with or without an air-entraining admixture.

Air bubbles and air voids:

Because air and water do not mix, air trapped in fresh concrete normally is in the form of gas bubbles surrounded by a thin liquid film and suspended in the mix w a t e r. These bubbles vary in size and shape from microscopic, hollow spheres the size of cement grains to large, irregularly shaped gas pockets the size of coarse aggregate particles or larger. All these bubbles can move in fresh concrete. They can change size and shape, expand or contract, merge or rupture, or be removed from fresh concrete through vibration. Once concrete hardens, however, the air bubbles are fixed in place. The hollow space formed by the last position and shape of a bubble is an air void. T h e whole collection of these hollow spaces in a sample of hardened concrete is the air void system.

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Effects of air voids:

When the air voids in hardened concrete are mostly in the form of large voids and pockets, the effects are generally detrimental. Failure to remove larger voids results in porous, poorly consolidated concrete in the forms and around re-bars and other inserts, with honeycombing and reduced in-place strength. Fresh concrete should be consolidated during placement to remove as many of the larger voids as possible. Consolidation will be discussed in Part 2 of this series. When an air- entraining admixture is used, concrete needs to be handled so as to preserve as many of the smaller voids as possible. Workability improves when an air- entraining admixture is used to increase the number of small voids. Small, well-dispersed bubbles act as air cushions between aggregate particles, reducing friction and interlocking. This benefit often allows a reduced water content for concretes with an air-entraining admixture. As a large number of microscopic bubbles work themselves in between cement grains and fine aggregate particles, bleeding and segregation are reduced. Increased cohesion caused by the air-entraining admixture helps the mix resist segregation, but can sometimes make its ticky. Further, when the void size gradation shifts toward finer sizes, there is less reduction in compressive strength for a given total air content, and it is possible to offset strength reduction with a lower required water content.

Volume of air required:

An air void system having a total volume of about 18% to 20% of the cement paste volume can generally accommodate expanding ice and water. More air volume is required to accommodate ice expansion for porous and saturated concrete. Paste volume is difficult to measure, so it is more convenient to describe air content as a fraction of total concrete volume. Air contents of 18% to 20% of paste volume usually are 4% to 7% of concrete volume. However, since air protects only the paste, richer mixes with greater paste volumes need higher air contents to protect the paste. For the same reason, leaner mixes may need less air. Aggregate size, shape, and gradation also can affect required air volume because paste contents are different. For example, a topping mix with pea gravel usually will require more air to achieve frost resistance than a pavement mix with 11⁄2inch stone.

Void size and spacing:

Expansion pressure caused by freezing is reduced only if ice or water do not have to travel too far to the closest air void. Greater pressure is required to push ice or water long distances to a void space. If this pressure is too great, the cement paste will crack. This means that the cement paste will have a critical distance beyond which ice and water cannot flow without causing damage.

Thanks for Reading