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DESIGN OF MASONRY STRUCTURES Part 5

Khái niệm Tĩnh học, Cơ học hoặc Cơ kết cấu thường được dùng lẫn lộn và gắn với mặt toán học, vật lý học lý thuyết, trong khi Kết cấu xây dựng hoặc Cơ kết cấu xây dựng có mục đích ứng dụng Cơ học hoặc cơ kết cấu vào trong ngành xây dựng. | Note that some designers include the above modification factors in the basic equation 5.11 where they appear as a multiplication factor on the right-hand side e.g. for narrow walls equation 5.11 could be rewritten zw f 1.15 k 5.9 EXAMPLES 5.9.1 Example 1 Internal masonry wall Fig. 5.15 a Using BS 5628 Loading per metre run of wall Dead load kN m Imposed load kN m Load from above 105.0 19.0 Self-weight of wall 17.0 - Load from left slab 4.1 2.2 Load from right slab 4.1 2.2 Safety factors For material strength ym 3.5 For loading yf DL 1.4 yf LL 1.6 Plan Section Fig. 5.15 Plan and section details for example 1. 2004 Taylor Francis Design vertical loading Fig. 5.16 Loading from above W1 1.4x105 1.6x19 177.4 kN m Load from left W2 dead load only 1.4x4.1 5.7kN m imposed load 5.7 1.6x2.2 9.2 kN m Load from right W3 dead load only 1.4x4.1 5.7kN m imposed load 5.7 1.6x2.2 9.2kN m Wall self-weight 1.4x17 23.8kN m Slenderness ratio Effective height 0.75x2650 1988 mm Effective thickness actual thickness 102.5 mm Slenderness ratio 1988 102.5 19.4 Eccentricity See section 5.5.1 With full DL IL on each slab there will be no eccentricity since W2 W3. Fig. 5.16 Loading arrangement for eccentricity calculation. 2004 Taylor Francis With only one slab loaded with superimposed load W2 9.2 and W3 5.7. Taking moments about centre line ZWex w2 f 3 - w f 3 ex 9.2 5.7 X f 3 9.2 5.7 177.4 1.4 X 17 0.5534 mm From equation 5.2 et 0.6 X 0.5534 102.5 1 2400 X 19.4 2 - 0.015 0.332 14.536 14.868 mm So that since et is greater than ex em et 0.145t which is greater than 0.05t with the result that 5 1.1 1 - 2 X 0.145 0.78 Design vertical load resistance Assume t in mm and fk in N mm2 design vertical load resistance ptfk ym 0.78 X 102.5 x k 3.5 22.84 fk N mm or kN m Determination of fk We have design vertical load design vertical load resistance 177.4 9.2 9.2 4- 23.8 kN m 22.84 k kN m k 9.61 N mm2 Modification factors for fk Horizontal cross-sectional area of wall 0.1025x4.25 0.44 m2. Since 0.2 m2 no