Trusses can be bolstered with double-sided pitch or aisled with one-sided pitch of upper chord. The number of truss panels is determined by the placement of the purlins.
Strips of trusses, the verticals and the diagonals are made of hollow sections. The height of truss footing for fitting on columns is 300 mm for every span.
The joints of bars are mutually welded without any gusset plates. Trusses are delivered to a building site in parts of 15 m maximum length. The parts of bolster trusses are usually connected by bolts, whilst tension chords are connected by 8.8 class bolts. The parts of the aisle trusses are welded during the mounting.
Roof girders
By roof girders we understand straight roof trusses of span L = 12 m, fitted on inner columns of multiaisle halls. In the middle of the roof girder there is a bearing on the upper chord for placing the roof trusses.
Purlins
Purlins are trusses that bear the roof jacket. They are countersunk in between trusses, so the upper surfaces of the trusses and purlin chords are the same.
With halls of a bigger span, maximum 2 500 mm, the distance in between purlins is approximately 2 000 mm. They are made of iron-plate zinc-coated Z-sections made by the company METSEC. They are dimensioned by the producer´s calculating programme which also determines the requirements for the interconnection of purlins. The C-shaped eaves purlin is used for the connection to wall curtains.
Purlins are universally perforated, i.e. some openings do not have to be used. Assembly bracing of the roof´s flat surface is carried out in accordance with the project of the steel framework. The roof trees of saddle trusses are interconnected in the middle. The purlins can be made of thin-walled U-sections, sections made but rolling or rectangular pipes.
The permanent bracing of the roof´s flat surface must be secured by the roof cladding consisting of corrugated iron plates or iron-plate sheets, and this must conform to the connection of the roof cladding to the purlins.
Constructing without purlins: in a sectional roof jacket it is possible to place a bottom supporting plate made of trapeziodal profiles with high corrugation. The profiles are attached right to the trusses and at the same time they replace the function of the purlins.
Columns
Columns are made of thin-walled profiles 320 x 160 x 4 mm, 400 x 160 x 5 mm and 480 x 160 x 5 mm.
The outside faces of the side and gable columns is usually 160 mm behind the axis determining the span or length of the hall. On the column head there is a bearing for attaching a truss. The column foot consists of two U profiles which are provided with a vertical stiffener at the ends. Underneath the stiffener there is a slab that transfers the pressure from column stress into the footing. Support plates must always be placed under this slab.
Clamps for the attachment of spandrel beams are welded on to the columns.
The upper edge of the footing is min. 500 mm under the floor, bottom edge of the column is 20 mm above the footing.
Architectonically exposed constructions can be composed of columns of circular section from pipes.
Column dimensioning is carried out according to stress analysis of the steel construction project.
For preliminary column dimensioning it is true:
- one-aisle hall up to 6 m high - columns TP 320 x 160 mm
- from 6 to 7,5 m high - columns TP 400 x 160 mm
- from 7,5 to 9 m high - columns TP 480 x 160 mm
- middle columns of multi-aisled halls are made of profiles one degree higher than the side columns
- gable columns fixed in the footing and leaning against the roof steel construction are of TP 320 x 160 mm up to 10 m high
- one-aisled halls with cranes of lifting capacity 5,0 t (8 t) and up to 7,5 m high are composed of TP 400 x 160 mm (minimally), usually of TP 480 x 160 mm
The column of halls with heavier cranes or the columns for high halls are made of two rectangular profiles welded together. Inner profile ends under the crane bracket or in a statically required height.
For high constructions and for cranes with a great lifting capacity it is advantageous to use bay columns with shafts of U profiles, connected with two L profiles diagonals. The basis for such a design are worked out for a concrete project.
If the hall is to be extended in the future, a truss in the gable wall will be placed and the intermediate gable columns will be finished under the bottom strip of the truss.
Anchorage of fixed-end columns
Anchorage is performed according to a formerly accepted ON 73 2615 Instruction for anchorage of steel constructions. For column anchorage we use two or four in advance embedded anchor bolts M 30 that are 800 mm long. The nut of anchor bolt fits on cross beam from two TU 120, which lies on the upper surface of the column foot´s U profiles.
The upper surface of the footing is usually at least -0,500 m under the floor. Bolts are 400 mm above the upper edge of the footing (the bolt ends cca 100 mm under the floor ±0,00).
After mounting the shaft of the column and the footing under the floor level have to be concreted by a covering cca 100 mm, i.e. block min. l = 1 200 mm, w = 600 mm, h = 400 mm. The upper surface of this block is cca 100 mm under ±0,00. Concreting must ensure a perfect footing reinforcement and a permanent protection of steel parts against corrosion.
If this block on the hall´s outer side does not stand out above the finished ground, it is necessary to lower the level of the footing.
Anchor bolts are supplied by the steel construction manufacturer in advance, according to the requests of subsection designer, connecting of bolts into the given pitch will be done on a request.
Support plates are part of the steel construction delivery. These must be placed under the vertical stiffeners at the end of the brackets. The basic height of the mounting backing is 20 mm. The upper surface of the footing has to be kept in a tolerance +10 mm, -30 mm. The tolerance of the anchor bolts fitting (as for the direction and height) is 40 mm max.
The concrete used for the footing must be of the class B 15, at least, and not usually reinforced.
Spandrel beams
Spandrel beams are horizontal beams in between the columns, on to which we attach the wall jacket. They are usually made of C profiles from METSEC.
The lowest spandrel beam creates a border of retaining wall. Before wall jacket mounting, this spandrel beam has to be leveled and underpinned. The retaining wall is usually up to a level +0,35 m to +1,2 m above the floor, the bottom border of panels is min. 50 mm under this level.
The relative distance of spandrel beams is determined by the loading capacity of the jacketing panels (max. cca 3,0 m). Should the windows break more than one panel, the window´s opening has to be bordered by spandrel beams on its bottom and upper edge.
Panels above the windows and gates have to be connected to two spandrel beams or, if necessary, to a spandrel beam at the bottom and to the finished edge purlin at the top.
Gate casings are part of the metal framework of walls. The casings are usually made of rectangular pipes. If the gate is sectional (adjacent to the inner gate face), the outer face of the casing is on the inner face of the panel. If the gate is winged (adjacent to the outer gate face), the outer face of the casing is on the outer face of the panels.
Door openings are bordered by profile TU 210 x 50 x 4 mm with space cca 200 mm from the edge of the opening. The frame of the door creates the panel border. The finish is carried out at the mounting site.
The openings for window panes are bordered by rectangular profile. The details are carried out according to the building project and requests from the manufacturer of the window panes.
Stiffeners
By stiffening we understand the connecting of two columns by a simple truss construction. The finish, the number, the location and the layout of the bracing depend on the design calculation and the project of the steel framework.
Built-in floor - Floor on rolled girders
The supporting element is a trapeziodal galvanized plate 600 x 50 x 0,8 mm, which is placed on rolled girders in pitch cca 1,5 m.
The iron plate is covered with a concrete layer which is 50 mm over the wool and is usually reinforced with a reinforcing grid. On the concrete, there is a floor depending on the purpose of the room. Trusses transmit the loading into the floor girders.
The framework of the floor can be made of pre-stressed ferroconcrete panels called SPIROLL. SPIROLL panels are put on the girders continuously during the assembly of the steel framework.
Roof jacket with thermal insulation
It is required by the norm ČSN 73 0504-2 that the coefficient of heat passage for flat (light) roofs - U equalled 0,24 [W . m-2. K -1]. PUR panels of 80 to 100 mm thickness comply with this requirement.
For roofs with a min. pitch of 7% we use light roof panels with surfaces from varnished galvanized plates, the thermal insulation for which is formed by solid polyurethane foam (PUR). The upper plate is trapeziodal, longitudinal panel joints are covered (overlapped) by the edge corrugation. Only products of renowned firms that can assure long service life are used.
The panel roof jacket is supplied with border plates for a ridge, gable, etc. including joint and sealing material, eaves gutters and drain pipes.
A half-round eaves gutter on tile hooks can be covered by forward placed plates or panel elements (according to agreement).
Outer drain pipes are supplied together with eaves gutters - their placing is determined by the building project.
Gutters are protected against snow slide damage by a snow shelter.
Light roof panels consisting of PVC foil on the top, PUR foam as heat insulation and varnished trapezial iron plate on the bottom are used for roofs whose pitch is smaller than 7%.
A roof with a jointless covering can be designed as sectional (PVC foil + thermal insulation - PS boards or mineral wool felt + trapeziodal galvanized varnished plate).
The advantage of jointless roofs is that there are no gutters. A roof jacket reaches through the roof space (which is min. 150 mm high) over the edge of roof. In the roof there are only inlets into the inner discharge piping. Inlets from PVC are welded on to covering foil. There are no inter-roof gutters in the valleys. Compared with panel roofs, the roofs with foil do not need ridge and gable flashing. The connection of roof jackets to the openings for skylights and transmission through the installation are simplified, which leads to more functional reliability of these roofs.
Should the clogged drains cause overloading of the roof by water accumulated in the valley, overflow holes will be made in the attic panels in max. high 150 mm above the valley bottom.
Lighting through roof jacket
Ridge skylight arc or bolster, wide 3 - 6 m, covering: chamber polycarboxylic boards, 10 or 16 mm thick. Possibility to fit with ventilation or smoke flaps, electric control.
Diagonal roof lights are 1 or 2 m wide, length is max. 6 m, covering: chamber polycarboxyl. Placing: for trapeziodal covering - always away from (out of) the ridge, for jointless covering - away from (out of) the ridge or in an arbitrary place. Without possibility of ventilation.
Local lighting through the lens skylights - only for roofs with a jointless covering and PVC foil. Possibility to fit with ventilation or smoke flaps.
Wall jacket with thermal insulation
It is required by the norm ČSN 73 0504-2 that the coefficient of heat passage for outside (light) walls - U equalled 0,30 [W . m-2 . K-1]. PUR panels of 70 mm thickness comply with this requirement.
For jacketing we use light-weight panels. Their surfaces are made of varnished galvanized plates. Thermal insulation is ensured by PUR foam. The type of panel and colour of surface is confirmed during the delivery preparation.
The true latitude of panels is usually 1 000 mm. They are placed vertically in such a way that the panel axis is congruent with the column axis. The width of the panels at the corners of building is adjusted at the mounting site.
Other types of jacket can be supplied on request: layered panels with mineral wool felt insulation, jacket consisting of two trapeziodal plates, cassette jackets, etc.
Bordering plates for corners, attic, bottom edge, wall openings and also connecting and sealing material are part of the delivery.
Wall jacket mounting will be performed after levelling and underpinning the parapet spandrel beam.
Lighting through the walls
Plastic windows width cca as a panel - either tightly glazed or with an opening wing, fitted into the opening in the wall caused by breaking up the panel.
Plastic windows conjugated - 2 - 5 windows assembled together, combination of tightly glazed windows and windows with an opening wing according to designer request, double glazing.
Roof lights are made from translucent boards of three-layered polycarboxyl or double glazed panes. Recommended height of skylights: 1,0; 1,5; 2,0 or 3,0 m. Ventilation is provided with the help of individual plastic windows with wings, fitted in the place of roof lights.
Control of the ventilation windows which are placed out of reach is done with the aid of a mechanism.
Window panes
For commercial buildings, window panes are delivered according to the customer´s demands in aluminium or plastic frames, including entrance door with a manual or automatic control.
Gates
Electrically or manually extending sectional gates are used or opening gates with wings.
Doors
There is a predominant usage of doors with a wing from PUR panel. These ensure good thermal insulation qualities.
Roof and wall jacket without thermal insulation
Is made of trapeziodal varnished galvanized plates. The elements for lighting through the roof and walls, windows and doors are similar, only adapted in particular detail.
Minimum pitch is 7%. When there are extreme weather conditions, buildings which are not heat-insulated or heated can be affected by condensation and water dripping off the roof cladding. This can be avoided by the use of special iron plates with a layer preventing from condensation or water dripping or by the use of thinner PUR panels.
For completion the same principles are valid as mentioned in paragraph "Jacketing with thermal insulation".
Foundation load
The mentioned values for calculated load are valid only for a preliminary proposal of footing size.
Vertical load - permanent
- weight of roof jacket and steel construction 0,6 kN . m-2
Vertical load - load
- snow - II. snow area: 0,7 x 1,4 x 1,2 = 1,2 kN . m-2
- snow - III. snow area: 1,0 x 1,4 x 1,2 = 1,7 kN . m-2 atd.
Axial force N in a column
- calculated as a product of the column loaded surface and vertical permanent (live) load
Horizontal load - by wind
- M - moment [kNm] on the upper edge of footing in a bond level
- T - horizontal shearing force
- Hw - construction height from the footing to the gutter or attic of the wall
- for IV. wind area (w0 = 0,55 kN . m-2), for column pitch 6,0 m, terrain is of type A
Table No. 1
For intermediate values Hw is to be interpolated.
For III. wind area (w0 = 0,45 kN . m-2) the values from table 1 has to be reduced by ratio 0,45 / 0,55 = 0,818.
For terrain of type B, the effects are reduced by coefficient according to ČSN 73 0035, For other pitch of columns it is by ratio towards the width 6,0 m.
The column effects of multi-aisle halls can be roughly established as a double load factor of M and T values, divided to every columns of cross link in ratio to their toughness.
The determining combination for the size of the footing for light-weight halls is min. N (only from permanent load) and max. M (from wind). Considering this fact, it is possible to determine the size of the footing for one-aisle halls with light-weight cranes.
It is assumed that the horizontal shearing force T will be carried by a floor concrete board.
