Architectural design and practice Phần 9 ppsx

Table 12.1 Loading on wall A per metre run ©2004 Taylor & Francis Table 12.1 (Contd) ©2004 Taylor & Francis ©2004 Taylor & Francis Table 12.2 Loading on wall B per metre run; inner leaf ©2004 Taylor & Francis ©2004 Taylor & Francis walls will provide the resistance to wind loading. In an actual design, the designer must of course check that the structure is safe for wind blowing east-west and vice versa. In the calculation below it has further been assumed that the walls act as independent cantilevers; and hence moments or forces are apportioned according to their stiffness. 12.5.2 Wind loads These are calculated according to CP 3, Chapter V: Part 2. We have Using ground roughness category 3, Class B, with height of the building=21.0m, from Table 3, CP3, Chapter V: Part 2 Therefore design wind speed is and dynamic wind pressure is From Clause 7.3, CP3, Chapter V: Part 2, total wind force The total maximum bending moment is total max. BM=F×h/2 where h is the height under consideration. Total BM just above floor level is given for each floor by: • 6th floor C f qA e ×h/2=1.1×(1269/10 3 )×21×3×3/2=131.9kNm • 5th floor 1.1×(1269/10 3 )×21×6×3=527.6kNm • 4th floor (1.1×1269×21/10 3 )×9×9/2=1187.20kNm • 3rd floor 29.313×(12×12/2)=2110.54kNm • 2nd floor 29.313×(15×15/2)=3297.70kNm ©2004 Taylor & Francis Fig. 12.3 The variation of the factor S 2 and the wind velocity along the height of the building. (Assumptions made in the design shown in full lines.) ©2004 Taylor & Francis • 1st floor 29.313×(18×18/2)=4748.71kNm • ground floor 1.1×(1269/10 3 )×21×21×21/2=6463.2kNm In the calculation the factor S 2 has been kept constant (Fig. 12.3), which means the design will be a bit conservative. However, the reader can vary the S 2 factor as given in Fig. 12.3 taken from Table 3 (CP 3) which means the wind speed will be variable depending on the height of the building. 12.5.3 Assumed section of wall resisting the wind moment The flange which acts together with the web of I-section is the lesser of • 12 times thickness of flange+thickness of web • centre line to centre line of walls • one-third of span (a) Wall A For wall A (Fig. 12.4), neglecting the outer skin of the cavity wall flange, the second moment of area is (b) Wall B The flange width which acts with channel section has been assumed as half of the I-section. For wall B (Fig. 12.5), neglecting the outer skin of the cavity wall flange, ©2004 Taylor & Francis Table 12.3 Distribution of bending moment stresses and shear force in walls ©2004 Taylor & Francis ©2004 Taylor & Francis [...]... conventional design calculations described in this chapter a more sophisticated analysis of the structure is possible by idealizing it as a frame with vertical loading as shown in Fig 12.7 Similarly, the structure can be idealized and replaced by a two-dimensional frame (Fig 12.8) and analysed as discussed in Chapter 6 for wind loading 12.7 DESIGN CALCULATION ACCORDING TO EC6 PART 1–1 (ENV 199 6–1: 199 5) To... 1.35Gkj+1.35Qki+1.35 Wki and the design load=3.17×102.5×103/103=324.9kN/m 12.7.1 Selection of brick and mortar combination for wall A: according to EC6 Design vertical load resistance of wall on eccentricity and slenderness ratio 12.7.2 , where depends Calculation of eccentricity Figure 12 .9 shows the worst combination of loading for obtaining the value of eccentricity Axial load ©2004 Taylor & Francis Fig 12 .9 Calculation... (ENV 199 6–1: 199 5) To demonstrate the principle of design according to EC6, the wall A in the ground floor will be redesigned The dead and live loading is taken as calculated before and as in Table 12.1 The bending moments and shear forces due to wind loading are given in Table 12.3 The category of manufacturing and execution controls are assumed to be II and C respectively; thus ␥m=3 as given in Table... value of e at top of the wall is shown in Fig 12.6 Axial load P=(0 .9 78.54+1.6×7. 29) (Gk and Qk from Table 12.2) =(70. 69+ 11.66)=82.35kN/m First floor load P1=(1.4×6.48+1.6×2.025) (see Table 12.2) =12.31kN/m ©2004 Taylor & Francis BM at centre of the panel=627.8×(Cpe+CPi)h2×0.104×1.4 =627.8×(1.1+0.2)×(2.85)2×0.104×1.4 =96 4.6Nm/m (Cpe and Cpi from CP3, Chapter V: Part 2) (BM coefficient for four-sided... this wall just above ground level also is dead+wind, and the design load is (1 .96 ×102.5×103)/103=201kN/m 12.6.4 Selection of brick and mortar for inner leaf of wall B The design vertical load resistance of the wall is (ßtfk)/␥m (clause 32.2.1) The value of ß depends on the eccentricity of loading; hence the value of e needs to be evaluated before design can be completed 12.6.5 Calculation of eccentricity... be with no imposed load just after and during the construction 12.6.3 Load combination, wall B The design principle has been covered in great detail for wall A; hence for wall B this will be limited to the ground floor level to explain further salient points Inner leaf wall B –ground floor level (i) Dead and imposed loads ©2004 Taylor & Francis Table 12.4 Design load and characteristic brickwork strength... brick and mortar combinations for wall A:BS 5628 Design vertical load resistance of wall is (ßtf k)/g m (clause 32.2.1), eccentricity Hence ß=0.67 ©2004 Taylor & Francis (Table 7 of BS 5628), ␥m=3.5 (see section 12.3) The design loads from the previous subsection and the characteristic strengths are shown in Table 12.4 along with the suitable brick/mortar combinations Check for shear stress: design. .. in section 12.5.2: the staircase and lift well will also provide the stability against the wind which has been neglected However, any facing brick having water absorption between 7 and 12% in 1:¼:3 mortar may be used, provided that it satisfies the lateral load design The grade of mortar is kept the same as for the inner leaf Characteristic flexural strength: (Table 3) Design characteristic shear as... characteristic compressive stress fk for wall B (inner leaf) 12.6.7 Design of the outer leaf of the cavity wall B in GF Load combination: • Windward side ©2004 Taylor & Francis • Leeward side The design is similar to the inner leaf and will not be considered any further The slight tension which is developing is of no consequence, since 6 to 10% of the dead and imposed load will be transferred to the outer leaf... would be better and economical to do tests on prisms to obtain the characteristic strength For the ground floor ␥G has been taken as 1 for favourable effect The allowable shear due to precompression in BS 5628 is higher than in the Eurocode, but it does not make much difference to the design 12.8 DESIGN OF PANEL FOR LATERAL LOADING: BS 5628 (LIMIT STATE) To explain the principle of the design only panel . floor C f qA e ×h/2=1.1×(12 69/ 10 3 )×21×3×3/2=131.9kNm • 5th floor 1.1×(12 69/ 10 3 )×21×6×3=527.6kNm • 4th floor (1.1×12 69 21/10 3 ) 9 9/ 2=1187.20kNm • 3rd floor 29. 313×(12×12/2)=2110.54kNm • 2nd floor 29. 313×(15×15/2)=3 297 .70kNm ©2004. above ground level also is dead+wind, and the design load is (1 .96 ×102.5×10 3 )/10 3 =201kN/m. 12.6.4 Selection of brick and mortar for inner leaf of wall B The design vertical load resistance of. floor 29. 313×(15×15/2)=3 297 .70kNm ©2004 Taylor & Francis Fig. 12.3 The variation of the factor S 2 and the wind velocity along the height of the building. (Assumptions made in the design shown in