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Figure 4.27

Eqn 4.4 Table 2.3

The analysis and design would need to follow the requirements of EC2 Clause A.3.5 to take into account the sway effects.

EC2 Clause 2.5.3.4.2(4) does not generally allow redistribution in sway frames.

The method above is included to demonstrate its complexity. However, note the omission of guidance in EC2 Clause A.3.2(3) on which nomogram to use in EC2 Figure 4.27.

As an alternative means of determining the frame classification, it is suggested that an analysis as detailed in BS 5950(14) is used to demonstrate that the EC2 requirements are met for non-sway frames.

Assuming in the above example that the column sizes are increased such that a non-sway frame results, the following load cases need to be considered for design.

These same load cases would also be applicable to sway frames where amplified horizontal loads are introduced to take account of the sway induced forces, complying with EC2 Clause A.3.1(7) (b).

4.2.2.1.3 Load cases and combinations 2.5.1.2

With the rigorous approach the design values are given by 2.3.2.2 P(2)

where

Qk1 = primary variable load, Ok2 = secondary variable load

= 07 generally

The 7f values are given in EC2 Table 2.2. Load cases with two variable actions (imposed and wind) are

(a) Imposed load as primary load 1.35Gk + 1.5Qk + 1.05Wk

(b) Wind load as primary load 1.35Gk + 1.05Qk + 1.5 Wk

In addition, load cases with only one variable action are:

(c) Dead load plus wind 1.0Gk (favourable) + 1.5Wk 1.35Gk (unfavourable) + 1.5Wk

(d) Dead load plus imposed 1.35Gk + 1.5Qk

For non-sensitive structures it is sufficient to consider the load cases (a) and (b) above without patterning the imposed loads.

The NAD allows the use of EC2 Equation 2.8(b) to give a single imposed and wind load case:

NAD Table 1

Final load combinations for the example given here

4.2.2.1.4 Imperfections

Consider the structure to be inclined at angle v = —-— > 0.005 radians

Eqn 2.10 NAD Table 3

where n = number of columns = 5

Eqn 2.11

0.0039 radians

Take account of imperfections using equivalent horizontal force at each floor. 2.5.1.3(6) AH. = LV.v .

j j red

EU = total load on frame on floor j Using !35Gk + !5Qk on each span gives

Assuming the frame by virtue of its relative stiffness picks up 4.725 m width of wind load:

Therefore the effects of imperfections are smaller than the effects of design horizontal loads and their influence may be ignored in load combinations (ii) to (iv).

The design of the slab will be as described in Section 4.2.1.1.

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