Condition I Full lateral restraint provided Design procedure

(a) Calculate the factored load 1.6 x imposed + 1.4 x dead, and then calculate the maximum factored bending moment (M), and the factored shear forces (b) Calculate the second moment of area (7) required to satisfy the deflection limitations described in clause 2.6.2. For simply supported beams where is the second moment of area required in cm4. W is the total unfactored imposed distributed or point load in kN L is the span in metres and C is the deflection coefficient obtained for each loading...

Design procedure

(a) Calculate the factored load 1.6 x imposed + 1.4 x dead and then calculate the maximum factored bending moments (Mx) and the factored shear forces (Fv). (b) Calculate the second moment of area (I) required to satisfy the deflection limitations described in clause 2.6.2. For simply supported beams, use the method described in clause 4.2 (b). (c) Determine the effective length LB as described in clause 4.3 (c). (d) Choose a trial section and grade of steel and check that the equivalent uniform...

Determination of effective length of columns

For braced multistorey buildings the columns are held in position, so that the effective length Le to be used in design depends on the degree of restraint in direction (i.e. rotational restraint) afforded by the beams attached to the columns at each floor level or the foundations. Fig. 4 illustrates typical joint and foundation restraint conditions. Substantial base provides restraint about both axes Restrained or partially restrained about both axis Substantial base provides restraint about...

Portal frame ridge

Bolts at levels 1 and 2 resist moment Bolts at level 3 resist shear 28 Portal frame ridge (a) Assume the number and type of bolts required at 1 and 2 (see Fig. 28) to resist the bending moment and locate them to obtain maximum lever arm. (b) Using the distribution of force shown in Fig. 19, calculate the resisting moment. If it is less than the applied moment increase the number or size of bolts. (c) Check the thickness of end plates to resist bending moments caused by the bolt tension provide...

Roof and wall cladding

Although this Manual is concerned with the design of structural steelwork, it is essential at the start of the design to consider the details of the roof and cladding systems to be used, since these have a significant effect on the design of steelwork. The choice of cladding material largely depends on whether the roof is flat or pitched. For the purposes of this Manual, a roof will be considered flat if the roof pitch is less than 6 . It should be noted, however, that roofs with pitches...

Serviceability limit states Deflection

The structure and its members should be checked for deflections under unfactored imposed loads and unfactored wind loads. The deflections should also be checked where necessary for unfactored dead load + 80 of the unfactored imposed and wind loads. The deflections for beams arising from unfactored imposed loads should normally be limited to the following values beams carrying plaster or other brittle finish span 360 The deflection of columns arising from unfactored imposed and wind loads should...

Singlestorey portals sizing of rafters and stanchions

The plastic design of a portal with pinned bases is carried out in this Manual by the selection of members from graphs. This method is based on the following assumptions (a) plastic hinges are formed at the bottom of the haunch in the stanchion and near the apex in the rafter, the exact position being determined by the frame geometry (b) the depth of the haunch below the rafter is approximately the same as the depth of the rafter (c) the haunch length is not more than 10 of the span of the...

Spacing and edge distances

A summary of the requirements is given in Table 19. maximum spacing in unstiffened plate in direction of stress in any environment exposed to corrosion in any direction rolled, machine flame cut or planed edge any end in the direction that the fastener bears In Table 19 t is the thickness of the thinner part d is the nominal bolt diameter D is the hole diameter e is f (215 py)

Strength and stability limit states

The load combinations and load factors to be used in design for the limit states of strength and stability are shown in Table 1 (repeated here for convenience). The factored loads to be used for each load combination should be obtained by multiplying the unfactored loads by the appropriate load factor yf from Table 1. Table 1 Load combinations and load factors y( Table 1 Load combinations and load factors y( The 'adverse' and 'beneficial' factors should be used so as to produce the most onerous...

Strength checks

The strength of ordinary bolts to carry the forces should be checked using the formulae in Table 20 In Table 20 ps is the shear strength obtained from Table 21 pbb is the bearing strength of the bolt obtained from Table 21 pbs is the bearing strength of the ply obtained from Table 22 e is the end distance but not greater than 2d p, is the tension strength of the bolt Tg is the thickness of the grip (mm) Yf is the specified minimum yield strength of the fastener. U is the specified minimum...

Sway stability check

This should be carried out for all frames by checking that the ratio of Lb D is equal to or less than that obtained from the following equation in which Lb is the effective span of the bay. When the depth of the haunches from top of rafter to underside of haunch is not less than 2D then Lb L - Lh, otherwise Lb should be taken as equal to L, where q (2Ic Ir).(L h) for single-bay frames or q (Ic Ir).(L h) for multibay frames L span of frame Lh haunch length if the haunches at each side of the bay...

Welds Fillet welds

Fillet welds are designed using an effective throat thickness a as shown in Fig. 20. Special measures should be taken when the fusion faces form angles greater than 135 or less than 45 . The effective length of a run of weld should be taken as the overall length less one leg length for each end that does not continue round a corner. The strength of the weld should be based on Table 25. Table 25 Design strength, pw, of fillet welds Table 25 Design strength, pw, of fillet welds * Applies only to...

Column splices ends prepared for contact in bearing

Column Flange

25 Column splice ends prepared for contact in bearing Splices should be designed for full contact bearing to resist the vertical loads. In addition, the following recommendations should be followed a the projection of the flange cover plates beyond the ends of the column members should be equal to the width of the flange of the upper column or 225 mm, whichever is greater b the thickness of the flange cover plates should be half the thickness of the flange of the upper column or 10 mm,...

Top and bottom cleats

Steel Work Cleats

a Choose size of seating cleat angles b Calculate the number of bolts required in shear and bearing on the lower cleat, which is assumed to support the whole of the vertical loading c Alternatively, calculate the weld size to suit maximum length available d Check buckling strength of beam web e Check bearing strength at the root of the beam web f Check bearing strength of angle cleat area of bearing x design strength g Check bearing strength of column due to bolt loads where appropriate....

Web buckling and bearing

Web Buckling Resistance

This check should be carried out when heavy loads or reactions are applied to unstiffened webs, e.g. it applies to beams supported on the bottom flange with the load applied to the top flange to a column supported by a beam to a beam continuous over a column and to web resisting compression forces from haunches in portals. Web buckling and bearing may be checked as described below, the dimensions being shown in Fig. 29. where Z gt , is the length of stiff bearing is as shown on Fig. 29 t is the...

Uncased columns

This Section describes the design of uncased columns for braced multistorey construction which are subject to compression and bending. Two cases are considered Case I columns braced in both directions and subject only to nominal moments Case II columns braced in both directions and subject to applied moments other than nominal moments. For both of these cases an iterative process is used requiring selection and subsequent checking of a trial section. The first step is to determine the effective...

Portal frame connections Portal frame haunch

Portal Frame

a Assume the number and type of bolts required at 1 and 2 see Fig. 27 to resist the factored bending moment, and locate them to obtain the maximum lever arm. b Using the force distribution shown in Fig. 19, calculate the resistance moment. If this is less than the applied moment increase the number and or size of bolts. c Check the thickness of the end plate required to resist the bending moments caused by the bolt tension. Double-curvature bending of the plates may be assumed since bolts...