Different Types of Loads and Forces Which Act on Structures Throughout Its Life Cycle - Report Example

Name Tutor Course Date Different types of loads and forces which act on structures throughout its life cycle A load is a force that tends to cause effects on structure and as a result of its action, it causes deformations, displacements and stresses in the structure. The types of loads that act on structures include dead loads, live loads, dynamic loads, wind loads, earthquake loads, and snow loads. Dead loads: Dead loads are forces that act on the structure as a result of the structure’s weight. These are loads that are permanent on the structure throughout its life. Dead loads are caused by the weight of the member, permanently fixed equipment such as reinforcement in beams and partition walls that are permanent. They are also called static loads Live loads: These are loads that are imposed on the structure. These loads are usually moving even without any impact. Live loads are produced from the intended use of the structure including the weights of any movable partitions on the structure. In this case therefore, the floor slabs should be designed so as to carry concentrated loads or uniformly distributed loads, depending on the load that causes greater stress in the considered part. Minimum design loadings have to be specified within building codes so as to allow for some reduction in load bearing walls, designing columns, piers supports as well as foundations. Dynamic loads These are moving loads on the structure. An example is the result of vehicles moving on the bridge during traffic. They are also caused by impact loads and gusts of wind. In addition, loads from cycling machinery are also dynamic loads. A dam can experience dynamic loads from the water constrained by it. Earthquake loads Earthquake loads occur when the base of a structure is loaded. These are horizontal loads that can be caused by the shaking of the base through earthquakes. The structure’s response to these forces depends on the motion’s frequency. Wind loads Wind loads are horizontal loads that are caused by relative movement between air and the earth. Consideration of wind has to be made during the design of the structure and most especially when the building’s heath is more than twice the transverse of the dimensions to the wind surface that is exposed. Low rise buildings of up to five storeys are not exposed to critical wind loads since there is sufficient moment of resistance provided by the floor system’s continuity to the connection of the column and the walls that are provided between the columns. The amount of wind load is also dependent on geographic location, type of physical environment that surrounds the structure, the structure’s shape and the size of the structure. Snow loads: The amount of snow on a structure also creates some forces on it. This amount s dependent on factors such as: the geometry of the structure’s roof, the structure’s size, the insulation imposed on the structure, the frequency of wind, the duration of the snow and the structure’s geographic location. Forces that act on structures include tension and compression. Tension forces tend to cause some stretching of the structure. On the other hand, compression forces tend to cause some squashing of the structure. Other forces include shear which is a result of a part of the structure sliding over the other and torsional forces which are turning forces on the structure. In addition, bending forces act on structures when a force is imposed on it at an angle and tends to bend the structure (The Constructor, Civil Engineering, 4). Reflection on the bridge building exercise conducted in class and ways to improve the building of a bridge to enhance its performance still within the constraints of the design brief The bridge building exercise requires a proper design based on the standards and specifications made. This requires specifications to be carried out based on the specification of the load and resistance factor design. Loads are the core of the design and analysis has to be done on the loads. Besides, field testing is carried out so as to determine the appropriate vehicle for design. Field testing and instrumentation are important for steel structures. Analysis has to be done on the large amount of data that is found from the field research. Although bridges are designed within conservative limits based on the codes, the assumptions made like the composite behavior and the support conditions usually have some underestimation of the capacity of the bridge to bear loads. This calls for improvement in the existing ways of design so as to try and increase the life of bridges. Design tools can be used to better incorporate standardized details and drafting details. Standardization brings about reduction in costs and increased speed and accuracy of the design. The integration of computer aided engineering and drafting will make designs and plan more iterative and interactive and lead to a cost effective as well as an effective design. Use of expert systems in checking for the design accuracy and reliability reduces errors and improves the design of the bridge (Bradshaw et al. 45). Compression and tension Compression Compression force tends to crush a structure by pressing it together. Such an action on the structure tends to make it to buckle if it cannot resist the force. The structure therefore requires compressive strength enough to withstand the force. On structures, columns are the most susceptible to compression. The columns get subjected to the axial loads through their centroids. Forces from above the column run through the centroid of the column axially and the column is squeezed between the forces from above and below it. Pcr-compression force They should withstand the compression force through its compressive strength. This strength can be determined from the force on the column divided by the cross-sectional area of the column. Buckling occurs when the compressive strength of the column is less than the compressive strength of the load on the column. Tension forces Tensional forces on a structure act on it by causing a pull on its ends. Rope bridges are examples of structures under tension. The cables/ ropes are under tension as they are pulled from opposite ends. Membrane structures under tension have to withstand the tensile forces. Their tensile strength has to be more than the strength of the tensile force. Tensile strength can be obtained by dividing the tensile force by the cross-sectional area (Ramankutty and Flemming 11-2). Changes in the types of materials used in construction over the past 100 years Materials are an important part of a bridge construction since. Use of traditional materials like timber, concrete and steel is still in progress but the past 100 years has seen important enhancements in their use. Use of composites has been. Fiber reinforced plastics were considered because they can bring innovative and solutions that are long lasting and can solve both simple and complex issues in bridge construction. Fears on FRPs ‘ problems in deflection, ductility, its reactivity with steel and concrete and its performance when exposed to ultraviolet light for long have been reduced by the researches carried out and ways of curbing the fears devised. Other issues were FRPs’ reaction under moisture and attacks by chemicals. Material testing standards have been used to find ways of solving the issues. Other design methodologies have also been used to fit the material properties of FRPs. FRPs have become competitive alternatives to the traditional materials for bridge construction. Use of high strength and high performance steel is considered because of its enhanced mechanical properties. In addition, material performance properties such as weldability, toughness, constructability and fabrication have been considered during the design so as to enhance the bridge’s performance. Use of composite materials such as fiber reinforced plastics (FRPs) has been considered. The properties of FRPs such as durability and low deterioration rate make it an exiting prospect for use in bridge construction. It is also light in weight and has a high resistance to corrosion. FRPs may be combined with the high strength steel so as to further enhance the performance of the bridge. In addition, high performance reinforcing bars shall be considered for reinforcement. Composite bars combined with steel cores and some cladding of stainless steel enhances the mechanical strength of the bridge (Hota, Ganga and Vijay 30-5). High performance concrete (HPC) is another way to improve the performance of the bridge. HPC is seen to be versatile since it has excellent strength characteristics and durability. The combinations of HPC for bridge decks and use of high strength steels and FRPs will almost double the life of a bridge. In addition, high strength and high performance steels have become more readily accepted by bridge engineers. These materials allow for reduction in dead loads because of their high material properties. The toughness and weldability of these high strength steels have been further increased to improve the functionability of the steels. Material performance issues like wielding, constructability and fabrication are always considered when working on the materials for choice. Further development has been seen the combination of high speed steel with FRPs. New processes for reinforcing wood have been developed. These include the combination of FRP properties and timber that is laminated with glue. Wood is an important material because of its resistance to compression loads while FRP has its importance in the resistance to tension. This combination has led to increased bending strength of the material. Besides, reinforcing timber with FRP gives a material that is highly resistant to both tensile and compressive loads. Beams made from such combinations have had the combination of excellent properties; high resistance to both tension and compression. Composite materials are mostly used where the problem is minimum clearance. Other developments have been realized in the use of recycled materials like plastics, waste materials and other by-products. These have been used together with High Performance Concrete construction materials (Goulet et al. 17). Works Cited Bradshaw et al, Special Structures: Past, Present, and Future: American Society of Civil Engineers’ Paper, 2010. Goulet A. James, Kripakaran Prakash and Smith Ian, Structural Identification to Improve Bridge Management. Switzerland 2009. Hota V.S. GangaRao, P.V. Vijay,Feasibility Review of FRP Materials For Structural Applications, West Virginia University, Morgantown,2010. Ramankutty Kannankutty, Donald J. Flemming, Bridge Engineering: Committee on General Structures. 2001. The Constructor, Civil Engineering, Types of loads on structures, retrieved on November 30th 2012 from: http://theconstructor.org/structural-engg/analysis/types-of-loads-on-structure/1698/, 2012. Read More