IS2 - Forces and Loads.pdf

TOPIC 2 : BASIC STRUCTURAL DESIGN FORCES AND LOADS 1.0 Load Loads are a primary consideration in any building design because they define the nature...

TOPIC 2 : BASIC STRUCTURAL DESIGN FORCES AND LOADS 1.0 Load Loads are a primary consideration in any building design because they define the nature and magnitude of hazards or external forces that a building must resist to provide reasonable performance (i.e., safety and serviceability) throughout the structure’s useful life. The anticipated loads are influenced by: a building’s intended use (occupancy and function) configuration (size and shape) location (climate and site conditions) Ultimately, the type and magnitude of design loads affect critical decisions such as material selection, construction details, and architectural configuration. Thus, to optimize the value (i.e., performance versus economy) of the finished product, it is essential to apply design loads realistically. Loads which act on building’s structure consist of dead load, live loads and environmental loads. DTA30333 | BUILDING STRUCTURE | KOLEJ KEMAHIRAN TINGGI MARA PASIR MAS 2  TOPIC 2 : BASIC STRUCTURAL DESIGN FORCES AND LOADS 1.1 Types of load 1.1.1 Dead Load Dead loads are gravity loads that are constant throughout the structure's life. Weight of all materials of construction incorporated into the building. Anything that is a fixed part of the structure and physically attached to it. (wall, roof trusses, beam, post, fix furniture and etc) Magnitude is predictable. 1.1.2 Live Load Live loads / imposed loads are those loads produced by the user and occupancy of the building. They are temporary, of short duration, or moving. People. Movable furniture. Magnitude is probabilistic as forces are variable. 1.1.3 Environmental loads Environmental loads are loads that act as a result of weather, topography and other natural phenomena. Wind loads (Typhoon, hurricane, tornado) Snow, rain and ice loads Seismic loads (Earthquake, tsunami) Temperature changes leading to thermal expansion cause thermal loads Loads from fluids or floods DTA30333 | BUILDING STRUCTURE | KOLEJ KEMAHIRAN TINGGI MARA PASIR MAS 3  TOPIC 2 : BASIC STRUCTURAL DESIGN FORCES AND LOADS 2.0 Force A force on a structure is the weight or pressure exerted on a structure but can be further defined to the type of force. 2.1 Types of force When load or force act on structure, that structure will change to a certain form. There are many types of forces as listed below: Tension Compression Shear Torsional / Twisting Bending 2.1.1 Tension The force that causes elongation or lengthening of the member (tensile force). When members in material was pulled, it become longer and the section cross area become smaller. 2.1.2 Compression The force that causes the structural member to shorten and can result in failure due to crushing. When the material compressed, it become more compact towards the direction of force act. DTA30333 | BUILDING STRUCTURE | KOLEJ KEMAHIRAN TINGGI MARA PASIR MAS 4  TOPIC 2 : BASIC STRUCTURAL DESIGN FORCES AND LOADS 2.1.3 Shear The combination of two forces acting in opposition to each other resulting in a sliding or tearing tendency. It divided material in one parallel surface. Different forces in one cantilever can produce shear force. 2.1.4 Torsional / Twisting Twisting produced when force twist opposite direction and make the form change. 2.1.5 Bending Bending was produced from forces which bend a part of element in compression, tension and shear which occur on that part of element which cause bending. DTA30333 | BUILDING STRUCTURE | KOLEJ KEMAHIRAN TINGGI MARA PASIR MAS 5  TOPIC 2 : BASIC STRUCTURAL DESIGN FORCES AND LOADS 3.0 STRESS 150N Stress = F A = 150N (3x2)m² 2m = 150N =25Nm⁻² 3m 6m² DTA30333 | BUILDING STRUCTURE | KOLEJ KEMAHIRAN TINGGI MARA PASIR MAS 6  TOPIC 2 : BASIC STRUCTURAL DESIGN FORCES AND LOADS 4.0 Material In building construction, there are many types of material used. The selection of material is depend on function of the structure because each material having different strength and character to support variety of forces. 4.1.1 Wood Strong in compression and tension but not strong as steel. Wood is weak in shear. 4.1.2 Brick/Concrete Strong in compression but weak in tension and shear. 4.1.3 Steel Strong in tension, compression and shear. TENSION COMPRESSION SHEAR WOOD √ √ BRICK √ CONCRETE √ STEEL √ √ √ DTA30333 | BUILDING STRUCTURE | KOLEJ KEMAHIRAN TINGGI MARA PASIR MAS 7