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**SECTION 8 - RACKING (BRACING) AND SHEAR FORCES WEEK 13**

AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

8.1 GENERAL Permanent bracing shall be provided to enable the roof, wall and floor framework to resist horizontal forces applied to the building (racking forces). Appropriate connection shall also be provided to transfer these forces through the framework and subfloor structure to the building’s foundation. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

8.1 GENERAL Where required, bracing within the building, which normally occurs in vertical planes, shall be constructed into walls or subfloor supports and distributed evenly throughout. Where buildings are more than one storey in height, wall bracing shall be designed for each storey. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

FIGURE 8.1 VARIOUS BRACING SYSTEMS CONNECTING HORIZONTAL DIAPHRAGMS AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

NOTES to Figure 8.1 1. The wind force on unclad frames may be equal to or greater than those on a completed clad or veneered house. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

NOTES to Figure 8.1 2.Horizontal wind (racking) forces are applied to external surfaces that are supported by horizontal or near horizontal diaphragms. Diaphragms include roofs, ceilings and floor surfaces including their associated framing. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

NOTES to Figure 8.1 3.Each horizontal diaphragm transfers racking forces to lower level diaphragms by connections and bracing. This continues down to the subfloor supports or concrete slab on the ground, where the forces are then resisted by the foundations. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Wind produces horizontal loads on buildings that must be transmitted through the structure to the foundation. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

In a conventionally constructed house these loads are transmitted to the ground by a complex interaction between the walls, ceiling/roof structure and floor structure. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The ceiling and floor form large horizontal diaphragms and normally play an important part in this action as most walls rely on support from this ceiling or floor diaphragm to prevent them blowing over. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The wind forces are transmitted to the ceiling diaphragm from the walls and also the roof. They are then transferred through the ceiling diaphragm to the bracing walls that transmit them to the floor structure, foundations and then into the ground. Without ceiling diaphragm With ceiling diaphragm AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

8.2 TEMPORARY BRACING Temporary bracing shall be equivalent to at least 60% of permanent bracing required. Temporary bracing may form part of the installed permanent bracing. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

General Bracing shall be designed and provided for each storey of the house and for the subfloor, where required, in accordance with the following procedure: AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Determine the wind classification Determine the wind pressure Determine area of elevation Calculate racking force AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

NOTE: To calculate the number of braces required for wall bracing, the required racking force (kN) is divided by the capacity of each brace. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The total capacity of each brace is equal to the length of the brace multiplied by its unit capacity (kN/m) as given in Table 8.18 (pg 141). AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

For example: a diagonal brace Type (c) (as per Table 8.18) has a total capacity of 1.5 kN/m Multiplied x length of bracing wall = 1.5kN/m x 2.4m = 3.6 kN for a 2.4 m long section of braced wall. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

General (f) Check even distribution and spacing (g) Check connection of bracing to roof/ceilings and floors AS SECTION 8 - RACKING AND SHEAR FORCES

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**8.3.2 Wind pressure on the building**

Wind pressures on the surfaces of the building depend on the wind classification, width of building and roof pitch. Tables 8.1 to 8.5 give pressures depending on these variables. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

When wind flows over a building it applies different pressures (forces) on a flat vertical wall to that on the sloping roof surface. Pressure on roof kPa* Pressure on wall kPa* * These values are indicative only and will vary with roof pitch, building height to depth ratio etc. The tables need to know the ratio between how much roof area the wind ‘sees’ as opposed to how much wall area the wind ‘sees’. The building width and roof pitch will establish this ratio. AS SECTION 8 - RACKING AND SHEAR FORCES

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**8.3.2 Wind pressure on the building**

Pressures are given for single storey and upper storey of two storeys for both long wind at 90O to the ridge and short wind parallel to the ridge sides of the building, and lower storey of two storeys or subfloor for both long wind at 90O to the ridge and short wind parallel to the ridge sides of the building. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Area of elevation The wind direction used shall be that resulting in the greatest load for the length and width of the building, respectively. As wind can blow from any direction, the elevation used shall be that for the worst direction. For example AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Area of elevation In the case of a single-storey house having a gable at one end and a hip at the other, the gable end facing the wind will result in a greater amount of load at right angles to the width of the house than the hip end facing the wind. Sloping roof surface All vertical surface \ this is the worst wind direction + vertical wall AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

For example, the relatively simple building shape shown in Figure 8.2(A) must be broken into two parts (shapes) in Wind Direction 2 because gable ends are calculated using a different table. After calculating the separate bracing requirements for each part the bracing elements used must also be distributed accordingly. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

As indicated by Figures 8.2 (A) and Note 1, the area of an elevation includes only the top half of the wall. Note: 1 - h = half the height of the wall (half of the floor to ceiling height). This is the area used to calculate single or upper storey bracing Ceiling diaphragm Floor Slab AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

As indicated by Figures 8.2 (B) and Note 1, the area of an elevation For lower storey of two storey section h = half the height of the lower storey (i.e. lower storey floor to lower storey ceiling) Ceiling diaphragm Floor diaphragm This is the area used to calculate lower storey bracing AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Note 3 of Figures 8.2 (A, B & C) pg 113 states The area of elevation of the triangular portion of eaves overhang up to 1000 mm wide may be ignored in the determination of area of elevation. Area of Elevation AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Include the area of enclosed verandah in the total area. Also include any roof area over an open verandah Calculate area of enclosed verandah separately using its width and pitch and distribute bracing accordingly. Do not include areas of open verandahs Open Verandah Open Verandah Enclosed Verandah Enclosed Verandah Width Width Building with open and enclosed verandahs, with main roof pitched from verandah beams. Building with open and enclosed verandahs, with main roof pitched separately from verandahs. AS SECTION 8 - RACKING AND SHEAR FORCES

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Racking force (pg 116) The total racking force, in kN, shall be calculated as follows: Projected area of elevation (m2) Lateral wind pressure (kPa) Total racking force x = AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.1 (pg 116) Gable ends and flat, vertical surfaces only AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Table 8.2 is used for determining the pressure on single or upper storey elevations where the wind direction is at 90O to the ridge and for wind speeds N1, N2, N3 & N4. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

continued WIND 90O TO RIDGE A3 N2 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Table 8.3 is used for determining the pressure on lower storey elevations where the wind direction is at 90O to a ridge and for wind speeds N1, N2, N3 & N4. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

continued TABLE 8.3 PRESSURE (kPa) ON PROJECTED AREA—LOWER STOREY OR SUBFLOOR OF SINGLE OR TWO STOREY—LONG LENGTH OF BUILDING—HIP OR GABLE ENDS WIND 90O TO RIDGE A3 N2 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Table 8.4 is used for determining the pressure on single or upper storey elevations where the wind direction is parallel to a ridge and for wind speeds N1, N2, N3 & N4. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

WIND PARALLEL TO RIDGE A3 N2 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Table 8.5 is used for determining the pressure on lower storey elevations where the wind direction is parallel to a ridge and for wind speeds N1, N2, N3 & N4. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

WIND PARALLEL TO RIDGE A3 N2 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Nominal wall bracing (pg 140) Nominal wall bracing is wall framing lined with sheet materials such as plywood, plasterboard, fibre cement or hardboard, or the like, with the wall frames nominally fixed to the floor and the roof or ceiling frame. (table 9.4 pg 167) AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The most common nominal bracing material used in houses is plasterboard wall linings. Plasterboard, fixed to the wall frame appropriately (to manufacturers specification) is given ‘structural bracing’ status with a reasonable strength rating. Fixed to the wall frame with nominal fixings, however, its bracing strength is much lower. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Nominal wall bracing The maximum amount that can be resisted by nominal wall bracing is 50% of the total racking forces determined from Clause 8.3.4 . Nominal wall bracing shall be evenly distributed throughout the building. If this is not the case, the contribution of nominal bracing shall be ignored. The minimum length of nominal bracing walls shall be 450 mm. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Nominal wall bracing The minimum length of nominal bracing walls shall be 450 mm. The bracing capacity of nominal bracing is scheduled in Table 8.17. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Where sheet wall lining is placed over the top of a structural brace, the value of the sheet wall lining can not be given its nominal value for the section that overlaps the structural brace. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Structural wall bracing See TABLE 8.18 pg 141 For sheet-braced walls, the sheeting shall be continuous from the top plate to the bottom plate Unless otherwise specified, sheet-bracing walls shall be a minimum of 900 mm wide to satisfy the requirements of their nominated ratings. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A3 A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A3 A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A3 A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A3 A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A3 A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A2 A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

TABLE 8.18 (continued) A2 A4 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

EXAMPLE: Required Racking force = 22kN less provision for 50% nominal bracing = 11kN. The proposed method of bracing is 2100mm long cut-in timber or metal angle braces. Type c Each brace is rated at 3.15kN (2.1 m long x 1.5kN/m). 11kN / 3.15 = 3.5 therefore 4 x 2.1m (12.6kN total) long braces are required plus 9.4kN of nominal bracing. (Check that 9.4kN of nominal bracing is achievable and also that the cut-in braces are not spaced more than required by ) AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

EXAMPLE: cont’d Of course there are other combinations for the above situation – 4 x 0.9 long ply braces rated at 3.4kN/m = 12.24kN plus 9.76kN of nominal bracing (type g) or 2 x 0.9 long hardboard braces rated at 3.4kN/m = 6.12kN plus 2 x 2.1 long metal angle = 6.3kN plus 9.58kN of nominal bracing. (type l) AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Wall capacity and height modification pg 147 The capacity of bracing walls given in Table 8.18 is appropriate to wall heights up to and including 2700 mm. For wall heights greater than 2700 mm the capacity shall be multiplied by the values given in Table 8.19. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Length and capacity for plywood bracing walls Where the same structural plywood bracing system is fixed to both sides of the wall, the capacity of the wall will equal the combined capacity of the bracing system on each side. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Location and distribution of bracing Bracing shall be approximately evenly distributed and shall be provided in both directions (see Figure 8.5). Bracing shall initially be placed in external walls and where possible at the corners of the building. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

FIGURE 8.5 LOCATION OF BRACING AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Spacing of bracing walls in single storey or upper storey of two storey construction A3 For single or upper-storey construction, the maximum distance between braced walls at right angles to the building length or width shall not exceed 9000 mm for wind classifications up to N2 (see Figure 8.6). AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Spacing of bracing walls in single storey or upper storey of two storey construction A3 For wind classifications greater than N2, spacing shall be in accordance with Table 8.20 (pg 150) (N3) and Table 8.21 (N4) for the relevant wind classification, ceiling depth and roof pitch. NOTE: Ceiling depth is measured parallel to the wind direction being considered. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

NOTE: A ceiling depth of 16 m is to be used for all ceiling depths greater than 16 m. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Spacing of bracing walls in single storey or upper storey of two A3 Where bracing cannot be placed in external walls because of openings or the like, a structural diaphragm ceiling can be used to transfer racking forces to bracing walls that can support the loads. Alternatively, wall frames may be designed for portal action. (This requires engineering advice) AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

FIGURE 8.6 SPACING OF BRACING AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The ceiling and floor diaphragms play important roles in the transfer of wind loads from the walls and roof to the braces. The ability of a ceiling or floor diaphragm to effectively transfer the wind load depends on the depth of the diaphragm. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Narrow or long diaphragms will not transfer the wind loads as effectively as a deeper diaphragm. The smaller the length to depth ratio the more effective the diaphragm. For this reason the spacing of bracing walls in limited as per Clause AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The above diaphragm, has a large length to depth ratio, (the length being the distance between braces) will not transfer the wind loads effectively. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

By adding an intermediate brace, the diaphragm is broken into two. Individually they have a smaller length to depth ratio and will transfer the wind loads effectively AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The same diaphragm, with the wind from the other direction, will transfer loads very effectively because its length to depth ratio is small. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Fixing of top of bracing walls All internal bracing walls shall be fixed to the floor for lower storey bracing walls, the ceiling or roof frame, and/or the external wall frame, with structural connections of equivalent shear capacity to the bracing capacity of that particular bracing wall. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Fixing of top of bracing walls Nominal and other bracing walls with bracing capacity up to 1.5 kN/m require nominal fixing only, i.e. no additional fixing requirements. For typical details and shear capacities, see Table 8.22. pg 152 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Fixing of top of bracing walls Wind loads, transferred from the roof and walls to ceiling and floor diaphragms are then transferred through braces to the ground. These braces, however, can only transfer these loads if the brace is connected to the ceiling or floor above and the floor below. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

The strength of these connections must be at least equal to the load the brace can transfer e.g. a cut-in timber or metal brace 2.4 m long can transfer a total of 3.6kN (2.4 x 1.5kN/m) – a 3.6kN connection to the diaphragm is required. or alternatively the strength of the brace can be reduced to equal the strength of the connection(s) . e.g. if a 2.8kN connection is used for the above brace, its bracing capacity will be reduced to 2.8kN. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Connection used equals the total brace capacity. Refer to table 8.22 pg 155 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Connections used equals the total brace capacity. Refer to table 8.22 pg153 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

(b) AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Fixing of bottom of bracing walls pg 155 The bottom plate of timber- framed bracing walls shall be fixed at the ends of the bracing panel and, if required, intermediately to the floor frame or concrete slab with connections determined from Table 8.18. pg 141 AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Fixing of bottom of bracing walls Where bottom plate fixing information is not given in Table 8.18, the bottom plates shall be fixed at the ends of each bracing panel using tie-down fixings determined from Table and Table 8.24. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Fixing of bottom of bracing walls For bracing wall systems of capacity 6 kN/m or greater given in Table 8.18, which do not specify intermediate bottom plate fixings, additional intermediate bottom plate fixings of a minimum of 1/M10 bolt, or 2/No. 14 Type 17 screws, at max.1200 mm centres shall be used. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

NOTES: 1 Some bracing wall systems require fixings to be full-length anchor rods, that is from the top plate to the floor frame or concrete slab. 2 The maximum tension load of 8.5 kN given in the Notes to Span Tables for studs in the Supplements is not applicable when considering the uplift force at the ends of bracing walls. 3 Where provided, the bottom plate tie-down details given in Table 8.18 may be used in lieu of the details determined from Table 8.23 and 8.24. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Roof Bracing pg 158 Pitched roofs (coupled and non-coupled roofs) The following shall apply to the bracing of pitched roofs: (a) Hip roofs Hip roofs shall not require any specific bracing as they are restrained against longitudinal movement by hips, valleys and the like. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

Pitched roofs (coupled and non-coupled roofs) (b) Gable roofs (including cathedral roofs) For wind classifications up to N2 gable roof buildings with a roof pitch greater than 10° but less than 25°, shall be provided with roof bracing in accordance with Clause . Alternatively, for wind classifications up to N4 and roof pitches to 35° bracing shall be in accordance with Table 8.25, Table 8.26, and the following: (i) Ridge to internal wall — minimum of two timber braces in opposing directions at approximately 45° (see Table 8.25 and 8.26). (ii) Diagonal metal bracing — single or double diagonal bracing shall be designed and installed in accordance with engineering principles. AS SECTION 8 - RACKING AND SHEAR FORCES

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**AS 1684 SECTION 8 - RACKING AND SHEAR FORCES**

FIGURE 8.9 GABLE ROOF BRACING AS SECTION 8 - RACKING AND SHEAR FORCES

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