## Alternative design procedure for calculation of compressive resistance Pc for columns

As an alternative procedure to that described in subclause 5.4.1 (g) the compressive resistance Pc of a column may be obtained from where Ag is the gross sectional area of the trial section, and pc is the compressive strength. (a) choose a trial section avoiding slender UB sections and obtain the design strength py from Table 2 according to the thickness of the flanges and grade of steel of the chosen section (b) calculate the slenderness A by dividing the effective length LE obtained as in...

## Case I Columns braced in both directions simple construction

For simple multistorey construction braced in both directions the columns should be designed by applying nominal moments only at the beam-to-column connections. The following conditions should be met (a) columns should be effectively continuous at their splices (b) pattern loading may be ignored (c) all beams framing into the columns are assumed to be fully loaded (d) nominal moments are applied to the columns about the two axis (e) nominal moments may be proportioned between the length above...

## 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 (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 LE 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...

## Flooring

It is essential at the start of the design of structural steelwork, to consider the details of the flooring system to be used, since these have a significant effect on the design of the structure. Table 5 summarizes the salient features of the various types of flooring commonly used in the UK. Table 5 Details of typical flooring systems and their relative merits Table 5 Details of typical flooring systems and their relative merits degree of lateral restraint to beams all categories but not...

## Movement joints

Joints should be provided to minimize the effects of movements arising from temperature variations and settlement. The effectiveness of movement joints depends on their location, which should divide the structure into a number of individual sections. The joints should pass through the whole structure above ground level in one plane. The structure should be framed on both sides of the joint, and each section should be structurally independent and designed to be stable and robust without relying...

## 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)

## Column splices ends prepared for contact in bearing

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

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

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...

## Portal frame connections Portal frame haunch

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...

## Bracing

Choose the location and form of bracing in accordance with the recommendations in clauses 2.2.3 and 3.4 a . Typical locations are shown on Figs. 1 and 2 for different shaped buildings. The wind load or the notional horizontal forces on the structure, whichever are greater, should be assessed and divided into the number of bracing bays resisting the horizontal forces in each direction. Braced frame rectangular or square on plan Note that roof and floors will act as horizontal girders provided...