Task A Timber design
Figure 1 below indicates the plan layout for a two storey dwelling to be constructed in load bearing masonry and timber. The building is to be constructed in Snowdonia where exposure conditions are severe.
The project is at concept stage and therefore any sketches you produce should be simple (preferably by hand) and show adequate information for initial costing purposes. Structural sketch details will also be used by the architect to prepare working drawings showing correct floor thicknesses and layout.
External walls are to be of cavity masonry construction. The outer leaf (which will be the exposed external architectural finish) is to be of clay bricks. The outer leaf will be continuous from ground to roof.
The cavity is to be 125mm wide and includes 25mm of Celotex propriety insulation.
The internal leaf will be Durox Suparblock® and will support the first floor and roof. The first floor span direction is to be decided by the designer. The roof is of duo-pitch timber truss construction with trusses spanning between the walls on each of the long elevations. Internal walls are fully bonded with the inner leaf of the external cavity wall.
Each storey height is 2.7m
Assume a wind pressure of 1.5 kN/m2
Dead load for the timber floors, including finishes, ceilings and services can be taken as 0.9 kN/m2
Dead load for the roof, including slates, rafters, insulation and ceiling can be taken as 1.0 kN/m2 on plan.
Imposed load for residential use is 1 .5 kN/m2
Imposed load for the roof is 0.6 kN/m2 on plan.
Task A Timber design
Use the above data to carry out the following tasks
a) Prepare two distinctly different schemes for the floor joist layout. One scheme must use solid timber softwood members only. The second scheme should make use of engineered timber components where appropriate. Show both schemes on a sketch plan layout and comment on the pros and cons of each. Compose an email to the client giving recommendations for the layout to be adopted. [40 marks]
b) Select a suitable floor joist section and check for bending shear bearing and deflection for the chosen layout above the living area only. The check for bearing should be applicable to the support condition chosen and appropriate for any lateral stability function that may be required. Show the plan layout of your preferred joist layout. [30 marks]
c) Select a suitable size for the timber columns and beams trimming the staircase opening through the first floor. You must choose appropriate dimensions for the stair treads and risers, which will dictate the dimensions of the opening required. Draw a sketch elevation of one column to include details of the connection of the first floor beams and a detail of the connection of the column to the foundation. [20 marks]
Task A Masonry design
Use the above data to carry out the following calculations for the walls marked A and B on Fig 1.
a) Check the minimum thickness required for the inner leaf based on limiting the slenderness ration to 27. [10 marks]
b) Determine the strength and thickness required for the inner leaf concrete block to resist vertical load (include the self-weight of the masonry in addition to load from any supported floor and roof). [20 marks]
c) Calculate the limiting dimensions for a laterally loaded wall panel. State whether wind posts are required. Use this panel size and edge conditions in part (d) below [20 marks]
d) Determine the strength and thickness of the cavity wall panel required to resist wind load. Specify a suitable facing brick for the loading and exposure conditions anticipated. [20 marks]
e) State whether vertical load or wind load governs the size and strength of the wall. Annotate your sketch plan with the size and strength of the concrete blocks based on your calculations. Include a sketch of a section through the cavity wall. [10 marks]
f) Indicate locations for movement joints and wind post on the plan (do this for the whole of the floor plan, not just the west elevation) [10 marks]