m6l36

m6l36 - Module 6 Approximate Methods for Indeterminate...

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Module 6 Approximate Methods for Indeterminate Structural Analysis Version 2 CE IIT, Kharagpur

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Lesson 36 Building Frames Version 2 CE IIT, Kharagpur
Instructional Objectives: After reading this chapter the student will be able to 1. Analyse building frames by approximate methods for vertical loads. 2. Analyse building frames by the cantilever method for horizontal loads. 3. Analyse building frame by the portal method for horizontal loads. 36.1 Introduction The building frames are the most common structural form, an analyst/engineer encounters in practice. Usually the building frames are designed such that the beam column joints are rigid. A typical example of building frame is the reinforced concrete multistory frames. A two-bay, three-storey building plan and sectional elevation are shown in Fig. 36.1. In principle this is a three dimensional frame. However, analysis may be carried out by considering planar frame in two perpendicular directions separately for both vertical and horizontal loads as shown in Fig. 36.2 and finally superimposing moments appropriately. In the case of building frames, the beam column joints are monolithic and can resist bending moment, shear force and axial force. The frame has 12 joints , 15 beam members ( , and 9 reaction components () j ) b ( ) r . Thus this frame is statically indeterminate to degree ( 18 3 12 9 15 3 ) = × + × = (Please see lesson 1, module 1 for more details). Any exact method, such as slope-deflection method, moment distribution method or direct stiffness method may be used to analyse this rigid frame. However, in order to estimate the preliminary size of different members, approximate methods are used to obtain approximate design values of moments, shear and axial forces in various members. Before applying approximate methods, it is necessary to reduce the given indeterminate structure to a determinate structure by suitable assumptions. These will be discussed in this lesson. In lesson 36.2, analysis of building frames to vertical loads is discussed and in section 36.3, analysis of building frame to horizontal loads will be discussed. Version 2 CE IIT, Kharagpur

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Version 2 CE IIT, Kharagpur
Version 2 CE IIT, Kharagpur

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36. 2 Analysis of Building Frames to Vertical Loads Consider a building frame subjected to vertical loads as shown in Fig.36.3. Any typical beam, in this building frame is subjected to axial force, bending moment and shear force. Hence each beam is statically indeterminate to third degree and hence 3 assumptions are required to reduce this beam to determinate beam.
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This note was uploaded on 06/30/2009 for the course CE 358 taught by Professor Trifunac during the Fall '07 term at USC.

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m6l36 - Module 6 Approximate Methods for Indeterminate...

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