Literature Review IntroductionHigh rise or multistory buildings or towers those are made from RCC frame structure or steel frames are subjected to lateral loads such as wind loads, and earthquake loads and caused by blasting phenomenon . Due to these loads oscillatory or vibratory motion is induced in these structures . As a result, horizontal deflections or distortions are increased, bringing the instability in the structure and the discomfort to the inhabitants. So, to overcome this problem it is needed that the lateral stiffness and natural frequency of the structure should be increased.
So, bracing system is the best option to increase the lateral stiffness and enhance the natural frequency of structure. And providing it stability against wind loads and seismic loads. Bracing systems are also very useful in overcoming the buckling of structural members . Bracing systems also increase the stiffness of structures So, in this research project a multistory building is to be designed, especially seismic design by using different bracing systems such as Diagonal bracing system, K shape bracing system, X shape bracing system.
In this research work, the performance and efficiency of different bracing systems is to be compared.StructureStructure is defined as the set of members, connected in such a way to fulfill specific purposes of carrying loads and to provide comfort to the inhabitantsTypes of Structures Rigid FrameIn rigid frame structures, the members are connected by rigid joints or welded joints.Truss (Pin connected joints)In truss structure member are joined to form a triangular shape. Here pin joints are kept, and joints take the loads. As a result, only axial tension and compression forces are found.Structural MembersBeamBeam is the horizontal flexural structural member that takes vertical and gravity loads. These loads are responsible for shear and bending.Columns Columns are to be defined as vertical compression members. Because of compression they are subjected to buckling.StrutsStrut is the compressive member of structure.GridIt is the arrangements of beams in such a way to form the right angles with each other and grid structure takes the vertical loads.PlatesPlates are of such shape that they have length, width as well as thickness. And plates are made of steel. Mostly plates are used in roofs and floors.Slabs They are like plates but made of concrete.Definition of tall buildingAccording to Au and Armstrong (1995): The tall edifice can be described as a multi-Storey building generally constructed using a structural frame, provided with high-speed lift, and combining extraordinary elevation with ordinary room such as could be found in low-buildings.Beadle (1971) defines the tall building by statingThe multistory building can be generally described by the need of extra operation and technical measures because of its actual height, instead of by its overall-height or the number of stories.Storey DriftDrift is generally defined as the lateral displacement of one floor relative to another floor. Drift control is necessary to limit damage to interior portions, elevator and stair enclosures, and glass and cladding systems. Stress or strength limitations in ductile materials do not always provide adequate drift control especially for tall buildings with relatively flexible moment resisting frames or narrow shear walls. Total building drift is the absolute displacement of any point relative to the base. Adjoining buildings or adjoining sections of same buildings may not have identical modes of response and therefor may have a tendency to pound against one another.BracingsMultistory or Highrise buildings when subject to lateral loads such as wind loads or earthquake loads, as a result building is affected by vibratory motion and its inhabitants are vulnerable to discomfort. To overcome this problem lateral stiffness is to be induced in the building and bracing is the best option to increase lateral stiffness. Bracing system provides good stability against the wind and gravity loads. These are efficient and economically good.Types of bracing systemsBracing systems are mostly of two types.Concentric Bracing System Concentric bracing system is defined as when the bracing members meet at common point or the meeting point of centroidal axis of braces is same . Concentric bracing enhances the lateral stiffness and the natural frequency of the structure and reduces the lateral storey drift.There are mainly three types of concentric bracings 1- Diagonal Bracing2- K shape bracing 3- X shape bracingEccentric BracingEccentric bracing system reduces the lateral stiffness and increases the energy dissipation capacity of the structure and decreases the lateral storey drift . In this type of bracing, bracing are connected to beam or column to separate working point. V shape bracing is the example of eccentric bracing.Other than these bracing systems there are also following bracing systems1-Chevron bracing system 2- Knee bracing system Diagonal bracingIt is used in steel structures. It overcomes the compression and tension. Diagonal bracing is efficient because it works very well in axial stress. In this way, minimum member sizes could be used, making it more economically good. K Shape bracingThis type of bracing is used when the passage is needed . In this way we can find place for doors and windows. This type of bracing system is avoided in the seismic regions due the column failure because of buckling of compression brace. X Shape Bracing systemX shape bracing is also called Cross bracing. X shape bracing is made by placing two diagonals intersecting each other. This type of bracing is very useful in overcoming the tension and compression. This type of bracing is very efficient in supporting a frame. Bracings in RCC StructuresIn RCC structures, shear walls and partition walls work as bracing systems Literature reviewAccording to theDhanaraj M. Patil and Keshav K. Sangle, Seismic Behavior of Different Bracing Systems in High Rise 2D Steel Buildings, Science Direct, Structures vol 3, 2015, pp 282 “305Different bracing systems for the G+19, type of structure Steel moment resisting frame Number height of each storey 3.00 m, Type of building Industrial Seismic zone II Basic wind speed 33 m/s, were analyzed.Following bracing systems were used X bracing system Diagonal bracing system Inverted V bracing system Chevron bracing system Knee bracing system He found that diagonal bracing and knee bracing respectively are the effective bracing systems among 5 types of bracing arrangements considered for the present study.According to theComparison of Different Bracing Systems for Tall BuildingsZ.A. Siddiqi, Rashid Hameed, Usman AkmalThey investigated the different bracing systems which are single diagonal bracing, double diagonal bracing, k/chevron bracing, v bracing and story-height knee bracing.They concluded that When columns are braced along their minor axis of bending, provision of K bracing results in minimum value of lateral displacement compared to other four types of bracing systems.When columns are braced along major axis, although lateral displacement values go beyond the permissible limits but among five types of bracing systems, which like the case when columns are braced along their minor axis of bending, K type bracing results in smaller lateral displacement compared to other types.According to theA Study On Bracing Systems On High Rise Steel Structures Jagadish J. S , Tejas D. Doshi A G+15 storey building was analyzed in this research. Different bracing systems were used like Single-Diagonal, X bracing, Double X bracing, K bracing, V bracingDisplacement was more in case of K and V shape bracing with comparison of unbraced system because of the irregular shape of the structure.Storey drift may be reduced or increased, with different bracing systems.