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MASONRY DESIGN ASSIGNMENT
Question 1 - Derivation of seismic actions on building
a) Determine the storey seismic weights (Wi) for each suspended level of the building, hence the seismic weight (Wt) of the entire building. When determining the storey seismic weights, include the slab selfweight, superimposed dead load, and the weight of walls, as well as the live load multiplied by the combination factor ψc (see §6.2.2 of AS1170.4: 2007 for guidance on determining Wt).
b) Calculate the base shear V for the structure.
c) Determine the storey seismic force distribution for the building. Present your results in a diagram like the example shown in Figure 4.
d) Determine the storey shear force distribution for the building. Present your results in a diagram like the example shown in Figure 4.
e) Determined the storey bending moment distribution for the building. Present your results in a diagram like the example shown in Figure 4.
Question 2 - Compressive capacity of unreinforced masonry
a) Determine the ultimate (1.2G+1.5Q) axial force on wall W07 at all levels of the building. Draw an axial force diagram for this wall (use a similar format to the SFD drawn in Question 1 part d)).
b) Check the capacity of wall W07 using "Design by simple rules" in §7.3.3 of AS3700. Note that you only need to check the capacity of the wall at the critical location i.e. ground level.
c) Suppose that an alternate floor framing arrangement was used for the building with a 300mm wide reinforced concrete beam (so the bearing area is 300mm×230mm) transmitting an ultimate (already factored) load N* = 250 kN to W07 as shown in Figure 5. Check the capacity of wall W07 under this loading arrangement. It may be assumed that the restraint provided to the top of the wall is the same as that provided by the slab in part (b) above.
Question 3 - In-plane analysis of unreinforced masonry
a) For wall W34, determine the dead load, live load for all levels of the building, hence determine 0.9Wt for W34 at the ground floor of the building (this is the load to be used for all shear and flexural checks of the wall in accordance with §184.108.40.206 and §220.127.116.11 of AS3700).
b) Calculate the relative proportion of seismic forces, hence shears and moments to each of the walls in the North-South direction (y-direction). You may assume the following:
- The centre of mass and centre of stiffness coincide
- No accidental eccentricity needs is to be considered
- Seismic loading is only applied in the y-direction (North-South direction)
- The floor slabs act as a rigid diaphragm in-plane, with no flexural coupling out- of-plane, that is, the walls act as 12m tall cantilevers.
c) Using the results from parts a) and b), draw the axial force diagram (for load case 0.9Wt), shear force diagram, and bending moment diagram for wall W34. Note that although 0.9Wt is taken as the vertical load on the wall, the seismic loads are to be calculated using Wt (i.e. as previously determined in Question 1).
d) Check wall W34 for the following:
i. In-plane shear.
ii. Heel tension and toe compression.
e) FOR CIVL6120 STUDENTS ONLY: Repeat part d) ii. but instead of simply checking tension and compression stresses in the wall, determine the flexural capacity of the wall using rectangular stress-block theory (based on the assumptions outlined in Section 8.3 of AS3700). Compare this to the results obtained from d) ii) and comment on which method you think is the more appropriate method of checking the in-plane flexural capacity of an existing wall under earthquake loading? Justify your answer.
Question 4 - Out-of-plane analysis of unreinforced masonry
a) Check the out-of-plane capacity of W26 under seismic loading (see §8.3 of AS1170.4:2007) at the uppermost floor of the building. Assume that the inner (230 mm) skin of bricks is simply supported at the roof and second floor levels and one vertical edge is supported laterally by wall W36 (the other vertical edge is not supported). You may assume that the outer skin of bricks is connected to the inner skin using heavy duty ties but it is not necessary to check the wall ties. In performing the check assume that the inertia forces are shared between the two leaves of the wall (see §7.7 of AS3700:2018)
Question 5 - Reinforced masonry retaining wall
The retaining wall shown in Figure 6 is fixed to the footing at its base and laterally supported along its top edge by the attached pavement (that is, it is a propped cantilever). Assume there is no surcharge loading from the pavement.
a) Draw the bending moment diagram and shear force diagram for the retaining wall.
b) Using a block size of 290×190×390 units, design flexural reinforcement (and shear reinforcement if required) for the retaining wall. You may assume that M4 mortar is to be used and the units are face shell bedded, the grout compressive strength f'cg = 20MPa and block compressive strength: f'uc = 15MPa. Include the design of starter bars into the footing but do not design any other reinforcement in the footing.
c) Provide a neat sketch of your design.