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...

Angles channels and Tsections

In simple tension members composed of angles, channels, and T-sections any eccentricity may be ignored, and the members may be treated as axially loaded provided that the effective areas, At are taken as follows (a) Single angles connected through one leg only, channels connected through web only, or T-sections connected through flange only where ax net area of connected leg, web or flange a2 gross area of unconnected legs or flanges as illustrated in Fig. 6. T- section connected through flange...

Braced multistorey buildings robustness

Multistorey construction that has been framed in accordance with the recommendations given in clause 3.2.4 and designed in accordance with the rest of the Manual, should produce a robust construction subject to the connections also being designed in accordance with the Manual. However in order to demonstrate that the requirements for robustness are met, the following checks should be carried out 1. Beams, ties and their connections at each column and beam in two orthogonal directions at each...

Bracing

Steelwork Structural Member

Choose the location and form of bracing in accordance with the recommendations in subsection 9.4 and clause 2.2.3. Typical locations are shown on Figs. 10 and 11 for single-storey buildings. Wind loads on the structure should be assessed for the appropriate load combinations and divided into the number of bracing bays resisting the horizontal forces in each direction. * Wall adequatley tied and permanently positioned * Wall adequatley tied and permanently positioned Valley bracing members wall...

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...

Check on position of plastic hinge in rafter and calculation of load capacity

In order to check that the correct mode of failure has been assumed a reactant diagram should be drawn. This is obtained by plotting the moments due to the applied forces and known moments at hinge locations, including feet. If the moments at all points in the frame are less than the values of Mp and only equal to Mp at the hinge locations then the assumptions may be considered as satisfactory. If Mp of the frame is exceeded at any point in the frame then the diagram must be adjusted to take...

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...

Fin plates

Shop welded to column Site welded to beam (a) Choose fin plate size, number and grade 8.8 bolts (b) Calculate force in outermost bolts from reaction and eccentricity moment (c) Check bolt strength yi single shear (reduce permissible shear values by 20 ) (d) Check bearing stress in web and the fin plate (e) Check the shear stress in the plate across the net area after deducting hole areas (g) Check size of weld in shear and bending and choose a fillet weld size to suit double length of weld...

Local capacity check

This should be carried out at the locations of the greatest bending moment and axial load (usually at the ends) by checking that AtPy Mcx Mcy The procedure to be followed is (a) determine the design strength py from Table 2 according to the grade of steel and the flange thickness. (c) calculate the b t ratio for the flange outstand and the d t ratio for the web where b is the width of the flange outstand d is the depth of the web t is the thickness of the element concerned. If the b t ratio...

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...

Stability of baunch

Provided that the tension flange of the haunch is restrained, then the maximum length between restraint to the compression flange of the haunch should be limited to the Lt obtained as shown below, provided that (b) the haunch flange is not smaller than the rafter flange (c) the depth of the haunch is not greater than 3 times the depth of the rafter (d) the buckling resistance is satisfactory if it is checked as though it were a compression flange in accordance with subsections 4.4 or 4.5 using...

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...

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

Cleats Structures

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...