TECHNICAL SPECIFICATION FOR MANUFACTURE OF PREFABRIC SPACE FRAME SYSTEM
Space truss system elements are composed of bars and spheres are so designed that they are manufactured at the workshop and afterwards erected at site. 
 

1- TRUSS JOINTS (NODES):

Joint elements are manufactured in the form of spheres or half-spheres by hot-gorging technique. 
Spheres have maximum 18 and half-spheres 14 bolt holes all threaded. (No holes are to be drilled in case they are not required). Later the bar elements can be screwed into these holes at site. The joint elements, spheres or half-spheres are manufactured in accordance with the German Standard DIN 17200. The joint elements at the supports however are produced from St 52 or St 60 quality steel in accordancw with DIN 17100.

2- BARS AND CONICAL TIPS (CONES)

Bars consist of circular pipes with conical tips welded and compressive forces. The bars and cones are manufactured of St 37 and St 62 quality steel in accordancw with DIN 17 100. The welding of the cones to the bars are carried out in accordance with DIN 4100 and DIN 4115. Appropriate symbols exist on the design drawings to specify the type and quality of the material, e.g. (St 37-2: 60.3.3x 3.65x2484).

3- BOLTS, NUTS AND PINS:

Bolts with their heads inside the conical tipes are free to rotate. A hexagonal member very similar to a nut is placed between the conical tip and the sphere node. These nut-like members which contain pin holes are doweled to the bolts and help to fix the bolts to the spheres.
Bolts conform to DIN 267 and DIN 13 and, are ISO type geared. The requirements for the types of materials, and the mechanical properties of the bolts, nuts, and pins are summarized in the table below. 
 

Bolts are labelled with the necessary information to define their characteristic properties.

4- ERECTION:

Horizontal and low-inclined pipes shall be so erected that the holes will look down. 
While the pipes are being mounted on the sphere nodes (joints) the bolts shall not be overstressed. 
Bolts shall be screwed to the sphere nodes tightly with the help of the nuts. 
Erection can be carried out either on or above the grade.

5- FINISHES 

5.1 Protection Against Corrosion 
All SPACE bars and spanner-sleeves are hot dip galvanized in accordance with DIN 50976.
Before the galvanization process, the members are dipped in special baths to free them from rust and oil. Thus cleaned members are dipped into molten zinc baths at 400.500 degree celsius temperatures. The zinc diffuses into the steel surfaces and zinc-iron crystals layers are formed at the members surfaces. After raising from the molten zinc bath the steel members are additionally coated with a layer of pure zinc.
Thickness of the zinc layer and tolerance are in accordance with DIN 50976, Table. The minimum zinc thickness on SPACE bars is 50 .

Spanner-sleeves and other small accessory pieces are treated in centrifuges after the galvanization process to ensure the minimum zinc layer thickness stated in DIN 50976. Since the hot dipped galvanization ensures the diffusion of zinc into every part of the steel members. Corrosion protection is guaranteed for long years. These protection periods can be expressed as 10-20 years. The protection period is further-more increased by the additional protective coating which is applied on hot dip galvanized surface. In some cases it may not be practically possible to hot dip galvanize some bulky pieces such as purlins, columns, etc. In those cases hot zinc spraying may be used instead of hot dipping, and wet coatings may be applied to those pieces instead of powder coating. 
Bolts are 20 electro-galvanized. 
Nodes are 20 electro-galvanized.

5.2 Powder Coating 
SPACE bars, spanner-sleeves and nodes are coated with high-quality plastic powder paint.
In powder coating process, carboxyl-containing polyester powders directly dusted onto the hot dip galvanized parts in an electrostatic field. Then the dusted parts are heated in run-through furnaces at 200 degree celsius. The powder coating layer melts and hardens. At the end of the process an 80 thick , smooth and shiny layer of coating is formed on the members. All the colors of international BAL color scale are applicable. Matt, low-lustre or high lustre surfaces can be provided as required.
Spanner sleeves are powder coated as the either members. But these sleeves are dipped into a high resistant primer between hot dip galvanization and powder coating processes. Since the powder coating is highly resistive to impacts, it has a much longer life span compared to conventional factory or insite paintings. Powder coating is resistive to UV rays and temperatures between -350 degree celsius and +280 degree celsius. It does not form blisters or scales and it is resistant to weathering. 
Wet paint can also be applied to some special pieces as described in 5.1. In this case the paint is applied at several layers to ensure a minimum of 30-40 dry film thickness.

6- STANDARDS 

Columns purlins are made of ST. 37 steel in accordance with DIN 17100.
Additional German DIN and Turkish TS standards are listed below for reterence. 
DIN 2440.2441.2458