7.1 Several schemes are possible, with certain constraints, using the same set of components. The degree of flexibility varies from system to system. However, in all the systems there is a certain order and discipline.
7.2 The following aspects, among others, are to be considered in devising a system:
a) Effective utilization of spaces;
b) Straight and simple walling scheme;
c) Limited sizes and numbers of components;
d) Limited opening in bearing walls;
e) Regulated locations of partitions;
f) Standardized service and stair units;
g) Limited sizes of doors and windows with regulated positions;
h) Structural clarity and efficiency;
j) Suitability for adoption in low and high rise building;
k) Ease of manufacturing, storing and transporting;
m) Speed and ease of erection;
n) Optimization of available handling equipment; and
p) Simple jointing system.
7.3 Systems for Mixed/Composite Construction
The system of mixed/composite construction depends on the extent of the use of prefabricated components, their materials, sizes and the technique adopted for their manufacture and use in building.
7.3.1 Combinations of System Components for Mixed/Composite Construction
The following combinations may be used in mixed/ composite construction:
a) Structural steel work and timber roofs on precast frames.
b) Precast floors onto steel and concrete beams, and masonry walls.
c) Profiled metal decking on precast beams.
d) Precast frames onto cast in-situ foundations, retaining walls, etc.
e) Precast frames stabilized by masonry walls, steel bracing, etc.
f) Precast cladding in steel or cast in-situ frames and vice-versa.
g) Glass curtain walling (see Part 6 ‘Structural Design, Section 8 Glass and Glazing’ of the Code), stone cladding or metal sheeting onto precast concrete frames, etc.
h) Reinforced concrete and structural steel as composite columns and beams.
7.3.1.1 Precast concrete may be combined with cast in-situ concrete, often termed hybrid construction. Cast in-situ is mostly used to form homogenous connections between precast elements and provide a structural topping for horizontal diaphragm action. In other cases it is used to form the foundations and sub-structure to the building.
7.3.1.2 Structural steel work is largely used in long span prestressed concrete floors supported on rolled and prefabricated steel beams and also as steel roof trusses supported on concrete columns.
7.3.1.3 Timber may be used as long span glue-laminated beams and rafters, with precast concrete. Precast floors may be used in timber frame construction. Similarly, timber frames with precast elements shall be used as a building system.
7.3.1.4 Brick and block masonry may be combined with precast concrete structures and floors. The most common combinations is to use prestressed floors on load bearing walls.
8 DESIGN CONSIDERATIONS
8.1 The mixed/composite structures shall be analyzed appropriately and the joints in them designed to take the forces of an equivalent discrete system. Resistance to horizontal loading shall be provided by placing beams, walls and/or bracings in two directions at right angles or otherwise. The individual components shall be designed, taking into consideration appropriate end conditions and loads at various stages of construction. The components of the structure shall be designed for loads in accordance with Part 6 'Structural Design, Section 1 Loads, Forces and Effects' of the Code. In addition, members shall be designed for handling, erection and impact loads that may be expected during handling and erection.
8.2 For mixed and composite construction the following shall be considered: