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High Rise Building Surveying

METHOD OF STATEMENT FOR SURVEY AND CONSTRUCTION CONTROL
 
The Method Statement is intended to be used by Survey Team as the basis for
the Survey and Construction Control.
 
The statements are quite detailed in how certain procedures are to be undertaken,
some refinements may be required to account for changed in circumstances and to upgrade in building techniques.
 
 
LOCAL CITY DATUM, TOWER DATUM AND PODIUM DATUM
 
The level shown on your drawing datum are not relative to the City datum.The level
shown on the podium drawing are also not relative to the Local City Datum, nor
they are relative to the levels shown on the Tower Architectural Drawings.
 
On site it will be necessary to use two bench march systems that one relates
only to the tower this will be called the Tower Datum. There will be Bench Mark
system relates only to the Podium.
 
A color code system can be applied so as to easily identified the two Bench
Mark system.
 
LEVEL DATUM TRANSFERS
 
Level Datum Control of Core
 
During the course of construction, and after the construction has been completed,
the vertical elements are subject to shortening to varying degrees. To reduce the effect of the differential shortening will have on the modular floor to floor heights, an allowance is to be made to increase the modular floor height to compensate for the expected shortening.
 
In practice, this is implemented by the inclusion of an increment for each modular
distance or portion of modular distance measure up the building. The Structural Engineer can predict the expected shortening of the core and the perimeter columns and from these predictions the increment can be calculated.
 
A Rule of Thumb figure for a reinforce concrete core is in the order of 2 millimeter per floor and for the Perimeter columns a 3 millimeter.
 
After first lift of the core system, a Bench Mark shall be established on the face of the concrete wall.
 
Immediately after subsequent jumping of the Formwork System, the Bench Mark onthe core shall be transferred up the face of the core. The modular distance for the portion of the building (i.e. 3600 mm for typical section) plus an increment apropriate for the portion of the building (i.e. 2mm) shall be measured up ne Bench Mark established.
 
The transfer shall be undertaken at three points. After each transfer the three new
Bench Marks will be levelled to check for any errors.
 
At the time of transferring to the shutter above, a floor Benchmarks established under this procedure will be the adopted core datum for the floor.
 
Level Datum Transfer for Perimeter Column
 
The steel perimeter columns will be shorten over time int he same manner that the core will shorten. The amount that the column shorten may differ from tha amount over the height of the building.
 
If  not addressed the end result maybe that at the top of the floors of the building the slab slope down from the core towards the perimeter of the building. As the column generally shorten by a greater amount than a reinforced concrete core.
 
the structural engineers can make predictions as to be expected shortening. From these predictions an increment can ba calculated.
 
The increment can be added to the modular floor height of 3600 mm as the Bench Marks are being trnasferred vertically up the columns.
 
It is critical that the transfer of the Bench Mark up the columns is undertaken after the column base is welded to the top of the column below. If the transfer takes place before welding then the possibility of sleeping of temporary fixing bolts will affect the Bench Mark.
 
Standard survey procedures shall be applied to ensure that each level transfer is independently checked prior to final mark up for builders.
 
Column Datum and Core Datum
 
The Bench Mark measured up the face of the perimeter column will be referred to as the Column Datum.
 
The Bench Marks measured up the face of the core will be referred to as the Core Datum.
 
Because of the different increments and the difference in the time of casting and loading the Core Datum and the Column Datum may not always be in the same horizontal plane.
 
For the first floor of the building the difference should be negligible. Howevere, it is advisable to maintain the two datum's and to monitor the difference in level between them so that if the differential shortening becomes significant action can be taken.

High Rise Building Surveying Method of Statement
under construction

IF THE PRICE IS RIGHT

SOME OF THE REGION’S LEADING SUPPLIERS OF LAND SURVEYING EQUIPMENT TALK ABOUT THE SWING TOWARDS LOWER END PRODUCTS AND THE EMERGING CHEAPER BRANDS OF TOTAL STATIONS ENTERING THE MARKET.

By Benjamin Millington

 

     Total stations have almost become an essential piece of equipment on any modern day construction site, but with so many to choose from, and so many different add-on functions available, are you choosing the right one?

     Regional sales manager for Hexagon’s Leica Geosystems Shiva Kumar says the approach to this question in previous year was to go  for the best technology money could buy.

     Total stations which measure precise angle one to two arc-seconds were the most popular machines in the Middle East’s construction market, but there were also the most expensive, which dictate a significant market shift with the onset on the economic downturn.

     “In the last six months there have been a huge change in the trend and customers are looking at the low- and middle-range technologies” says Kumar.

     “The market has now become price sensitive. The cheaper five second or six second total stations are moving fast. Nowadays it’s a five second market.”

     Kumar says this isn’t necessarily a bad thing, as many in the construction industry were previously purchasing high-end technology when a construction-grade total station was required.

     “It all depends on the application of what they do, you should use a one second total station to build a big road or bridge but if you’re constructing a villa or low-rise building a five second or three second maybe enough,” he says.

     “The customer needs to understand their requirement so we can help find a product, which will best suit their needs.

     “This is already happening and now most customers are keen to know what each system delivers rather than having a on second or two second system, which is over-specified for the job.”

     Geomax, a new player in the surveying equipment market, has taken this philosophy one step further by offering customers budget total stations, which have been stripped back to the bare essential functions.

     The company was formed by Swiss measurement equipment giant Hexagon as a separate entity to its aforementioned Leica Geosystems, which tend to specialize in the higher grade equipment.

     The Geomax entered the Gulf market in the month of February through UAE supplier Hillsborough Geomatics and reception of the products couldn’t have been better according to a division manager Intakham Alam.

     “If you talk about high end instrument, nothing is selling. In our scenario, we are aiming at the upper-middle and middle segments of the industry where there is a lot of activity,” he says.

     “We have not been affected by the global economic situation at all. If you look into the pricing of Geomax, I can say confidence that are the most cost effective brand as of now and that’s the reason why we are not having any problems during the recession.”

     Alam says the Geomax products, which are available in two to seven second accuracy, are between 15% to 30% cheaper than any competitors because the machines are streamlined for basic use.

     “The other companies produce machines which are very high-tech and very expensive. There are so many functions which the customer either don’t know how to use or have no need to use,” he says.

     “People are shifting to the three second and five second machines to save money, but second accuracy is not the only price parameter. Compared to us, the big companies are still selling at very high price.”

     “Our strategy is to identify the customers need and provide corresponding technology. We are a new company but we really caught up with the current market requirement.”

     Alam says the Geomax range is offering similar prices to Chinese manufactured product which have aggressively entered the market in recent years.

     “In 2000 there were only one or two Chinese companies, but today there are around 10 to 15,” he says.

     “They manufacture instrument in thousands and are really threatening the top companies because their total stations can be around US$5,000 (AED18,366) cheaper.

     “The problem is that their quality is not up to scratch and they have no support, they dump the instrument and run.

     “In this way we feel they are no competition to us because we have the backing from Hexagon, which is a strong brand with good R&D as well as ongoing and comprehensive product support.”

     However, Geomax is not the only well known company with a “basics” range of total stations in the Gulf market. Leading US manufacturer Trimble is well known for its high-end equipment, but also offers simpler technology through its Nikon and Spectra Precision brands.

     The regional manager for Middle East, India and Africa Debasish Mitra says sales have been down since the start of the year but the brands are performing better than the high-end Trimble products.

     The Nikon and Spectra brands are specially designed to suit areas where the standard of surveying professional is not as high as Europe or the US.

     Most people in the Middle East need a basic machine that is straightforward and easy to learn. Despite being cheaper than the high-end products, Mitra acknowledges that Geomax still has aprice advantage.

     “We see that Geomax is aggressively entering the market and have heard they are really on the lower (price) side than Nikon and Spectra,” he says.

     “I’m not sure what the quality is like and how much that stands in the marketplace, time will tell.

     “We can stand by our quality. We manufacture Nikon products in the same location as the Trimble brand, the only difference is we change the name, the colour and a little bit of programming.”

     Meanwhile Rohit Anand, Gulf sales manager for Japanese brand Sokkia, says he is skeptical that Geomax is taking a significant market share during the economic downturn.

     “I think everyone has suffered, the industry a whole has suffered and all of our competition sales are down,” he says.

     Anand also says the current influence of Chinese imports is havinf no major impact on the market. The Chinese brands have been around since 2008, people were tempted by the price, tried them and now reverted back to the established brands,” he says.

     “They found the products were used and thrown away because there is no means of supporting or servicing those products in the market.”

     Anand says the main demand in the region is still for high-quality total stations from a reputable supplier with an increased degree of automation and functionality.

     “If you’ve talking of only a simple building construction site then you can do the same job using levels or a bare minimum total station, which is just measuring angles and distances,” he says.

     “But not when it comes to a complex structure like Jumeirah Beach Hotel, the Metro or Burj Dubai. When you’re trying to supply equipment to a trained professional surveyor they like to have that added functionality.”

     Philippe Akl, regional sales and marketing manager for Japanese company Topcon, agrees.  “Nowadays, users pay more attention to speed and productivity, not only the traditional and basic functionalities like accuracy and range,” says Akl.

     Increased technology will allow customers to cut costs by reducing the personnel and minimizing time.

     “People will never go backwards to save few hundred dollars on the projects and quality we see in the Middle East.” H

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