Design of RC Frame Structures - Research Paper Example

Topic: Design, in RC, a typical main beam (element 34), column (element 63) and base, and provide sketch RC details of all three elements. Ensure that the beam and column. Order#: 150901 Deadline: 2007-01-29 02:06 Style: APA Language Style: English UK Grade: 2:1 Pages: 4 INTRODUCTION Beam-column connections in RC 1 frame structures under data are induced lateral displacements are generally subjected to large shear stresses that may lead to significant joint damage and loss of stiffness in the structure. There are so many researchers 2 have constant significant effort studying the performance of joints under shear reversals as well as on the development of design recommendations for ensuring adequate connection behavior in frame structures expected to experience large inelastic deformations. Current design recommendations for RC beam-column joints in earthquake-resistant construction given by Joint carried out with reference to BSs 648, 5950, 6399 and 8110 focus on three main aspects are confinement requirements, evaluation of shear strength; and anchorage of beam and to design, in RC, a typical main beam (element 34), column (element 63) and base, and provide sketch RC details of all three elements ensuring that the beam and column sizes are the minimum possible, working in multiples of 5mm. Consideration should attract a strong column-weak beam behavior must be ensured, and frame members or regions expected to experience large reversed inelastic deformations 1 Reinforced Concrete 2 Hanson and Connor 1967; Megget and Park 1971; Meinheit and Jirsa 1981; Ehsani and Wight 1982 must be properly detailed to make certain sufficient disarticulation capacity at some stage in earthquakes. The design recommendations for RC beam-column and base tag on a strength-based advance that the connection shave strength is tartan against the expected force demands imposed by neighboring members. These recommendations, the joint is tacit to behave adequately during earthquakes if its shear strength exceeds the shear demand. The strong column and weak beam method is ensured and enough crossways reinforcement and anchorage extent for reinforcing bars transitory through the connections. The least amount and greatest spacing of joint transverse reinforcement are based on the requirements for critical regions of RC columns that is combined with the longitudinal reinforcement from beams and columns and often lead to severe reinforcement congestion and construction limitations. Auxiliary needs to satisfy the anchorage length requirements for beam and column longitudinal bars may require either the use of large column and/or beam sections or a large number of small diameter bars, which might in turn increase reinforcement congestion in the connection. It is worth mentioning that satisfying the minimum BS Code provisions does not prevent the formation of wide diagonal cracks in connections during large displacement reversals and thus, these provisions are primarily intended to provide protection against loss of lives and structural collapse 3 3 BSs 648, 5950, 6399 and 8110 focus The design of structures moves towards performance-based design. There is need for new structural members and systems that possess enhanced deformation capacity and damage tolerance, while requiring simple reinforcement particulars. The development of a highly damage-tolerant beam-column connection would allow structural engineers to design joints for moderate shear distortions while exhibiting little damage reducing rotation demands in beam and eliminating the need for post-earthquake repairs. Assumptions Made Here the only centre line dimensions are taken in to account. Base joints are assumed to be hinged and assumed to be at a depth of below ground level. Half of the structure is considered because of symmetry and on the symmetric axis suitable boundary conditions are applied. Even though the beam behaviour is like a T beam over a certain length of span, moment of inertia is calculated based on the rectangular beam. This is on the 4 the feasibility of achieving large displacement capacity and damage tolerance in frame structures designed with simple reinforcement detailing in beams and connections conservative side. Three loading conditions are considered as dead load & live load provided data Analysis By StaadIII STAAD III is an excellent element to analysis and design software system developed by Research Engineers Inc. In addition to the analysis and design complete graphical interface is included in this package. This package can perform static analysis, second order stability analysis and dynamic analysis. It uses 2 or 3 dimensional frame elements, grid elements, and continuum elements and spring elements. Extensive design capabilities are available in STAAD-III/ ISDS for steel, concrete, timber and pre-stressed sections. Interactive design consists of design for footing, slab and retaining walls. One can also get deformed shape, bending and shear and axial forces diagrams. Six Steps In The Analysis First of all idealized the structure into a number of elements and developed the element stiffness matrix using constitutive law. By assembling the element stiffness to form global stiffness matrix using compatibility and equilibrium 5. Applying necessary boundary conditions solved the equations [K]{r}={R} where [K] is the structural stiffness matrix, {r} - generalized displacements and {R} - generalized forces. 5 scale beam-column subassemblies Displacements Solve For Elemental Stresses The building contains a symmetry line, which permitted the analysis of half of the structure, therefore reducing the mesh arrangement to 1106 nodes and the number of equations was reduced to a total of 6636 equations which were solved using STAAD-III. The renumbering of nodes is automatically done so as to reduce the bandwidth. Reducing the number of equations and reducing the bandwidth of the matrix system to be solved, which alternatively required less time from CPU point of view. This factor is extremely important especially in the industry since most companies operate on a network basis, which could ultimately affect the daily productivity 6. RC Design Suite The RC -Design suite is a reinforced concrete design program that has numerous applications for the design of concrete structures. It contains modules for the design of beams, columns, footings and slabs. For this project the students utilized this program only for the design of floor slab and combined footings. This program will also be used in the partial design of the raft footing. Design of beams and columns are carried out in STAAD- III package itself. 6 It also reduces the chance of human error in the input file. For each column load the individual footing is designed. However, many of these individual footings overlapped each other and had to be redesigned as combined footings. RC Design - suite provided an effective way of designing these combined footings through its footing design module. The footing design module of the program provides the footing length, effective depth and reinforcement requirements. The raft footing was designed in the area under the lift duct of the building. Some criteria dictated that the support to the elevator shaft should be watertight. RC-Design Suite was used to engineer the design of the raft. Importance Of Hand Calculations The students have been asked to perform hand calculations. Computer analysis and design programs offer great benefits to the design engineer. However, the computer programs can be easily misused without proper precautions in analysis and design procedures. If the design of any structure is based on the results obtained from erroneous computer analysis, it can lead to structural failures, costly disputes and poor performing structures. Performing the following procedures can eliminate many of the errors. Model the structure as closely to the real structure as possible. selected set of three beams and columns, one critical footing supporting the highest column load in the structure, and a typical combined footing. The purpose of the hand design calculation was to verify manually, the analysis from the finite element software package, STAAD-III driven RC Design Suite programs 7. 7 Design Studio Reference: 1) Nelson A. H. & George W. (1999) Design of Concrete Structure, page 23-56 2) Uzumeri, S. M., and Seckin, M., 1974, "Behavior of Reinforced Concrete Beam-Column Joints Subjected to Slow Load Reversals," P 74-05, 3) 4) < http://www-personal.umich.edu/'shchao> Read More