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The principle of composite construction is to use different materials in combination to make best use of their particular characteristics.
Different structural materials possess different characteristics. For instance, concrete and brickwork are relatively cheap bulk materials but have limited strength and are rather brittle, whilst steel is very strong and ductile. In order to maximise the respective benefits of different materials, composite structural forms are often used. Perhaps the most common example is reinforced concrete in which the tensile strength and ductility are derived from the steel reinforcing bars while the concrete provides the compressive strength.
Reinforced masonry, although less common, acts in a similar way. Timber fliche beams and steel rods as ties in timber trusses are yet other examples. This combination of materials can be used in all types of structural elements, including slabs and beams. The principle is also used for complete structures where, for instance, steel frames may derive stability from reinforced concrete shear walls. In this section attention will be confined to composite construction of individual structural elements.
In steel construction, a composite beam comprises a conventional steel beam connected securely to the concrete slab which it supports.
One structural form which is very popular for beams has evolved from the conventional arrangement of a steel beam supporting a concrete slab. Under normal conditions these will behave independently. However by ensuring that the two remain in intimate contact the slab can make a significant contribution to the bending strength of the beam. This arrangement is similar in principle to a reinforced concrete T- beam, and when the term 'composite construction' is used without qualification it generally refers to this form of structure.
The concrete contributes to the strength of the beam, resulting in cost savings. As a result of the contribution of the slab to the bending strength of the composite beam, the steel section sizes used will be appreciably smaller than for a non-composite condition. This provides direct economy in the tonnage of steelwork used, and may also give indirect economies due to a decrease in the construction depth of the floor. These advantages are obtained at the relatively small cost of providing the connection between steel beam and concrete slab.
For slabs the choice has traditionally been between precast units and some form of insitu construction. However one form of composite floor has become very popular, offering the advantages of speed, safety and efficiency of construction. This consists of profiled steel sheeting with a concrete topping.
The conventional forms of composite floor slab use relatively shallow profiles decking, but more recently a deep deck system has been developed, enabling significantly longer spans.
Different structural materials possess different characteristics. For instance, concrete and brickwork are relatively cheap bulk materials but have limited strength and are rather brittle, whilst steel is very strong and ductile. In order to maximise the respective benefits of different materials, composite structural forms are often used. Perhaps the most common example is reinforced concrete in which the tensile strength and ductility are derived from the steel reinforcing bars while the concrete provides the compressive strength.
Reinforced masonry, although less common, acts in a similar way. Timber fliche beams and steel rods as ties in timber trusses are yet other examples. This combination of materials can be used in all types of structural elements, including slabs and beams. The principle is also used for complete structures where, for instance, steel frames may derive stability from reinforced concrete shear walls. In this section attention will be confined to composite construction of individual structural elements.
In steel construction, a composite beam comprises a conventional steel beam connected securely to the concrete slab which it supports.
One structural form which is very popular for beams has evolved from the conventional arrangement of a steel beam supporting a concrete slab. Under normal conditions these will behave independently. However by ensuring that the two remain in intimate contact the slab can make a significant contribution to the bending strength of the beam. This arrangement is similar in principle to a reinforced concrete T- beam, and when the term 'composite construction' is used without qualification it generally refers to this form of structure.
The concrete contributes to the strength of the beam, resulting in cost savings. As a result of the contribution of the slab to the bending strength of the composite beam, the steel section sizes used will be appreciably smaller than for a non-composite condition. This provides direct economy in the tonnage of steelwork used, and may also give indirect economies due to a decrease in the construction depth of the floor. These advantages are obtained at the relatively small cost of providing the connection between steel beam and concrete slab.
For slabs the choice has traditionally been between precast units and some form of insitu construction. However one form of composite floor has become very popular, offering the advantages of speed, safety and efficiency of construction. This consists of profiled steel sheeting with a concrete topping.
The conventional forms of composite floor slab use relatively shallow profiles decking, but more recently a deep deck system has been developed, enabling significantly longer spans.
