Comparison and Contrast
Portal Method vs Cantilever Method

 

a. Which is more accurate?

b. Which method is the fastest way to solve?
c. Which is easiest?

A)Which is more accurate ?

Since this method relies on the frame behaving like a bending cantilevered beam, it should generally be more accurate for more slender or taller structures, whereas the portal method may be more accurate for shear critical frames, such as squat or short structures.

Both are approximate methods. The accuracy of the results depends on the length:height ratio of the structure being analysed.

B)The cantilever action is a good idealization for high rise structures(slender structure) where flexure is predominant.

The portal method will be good to get approximate results for short height structure where shear deformation governs.

C) Which is easiest ?ans portal method reason below

cantilever method

A point to keep in mind while analysing by any of these methods is that none of these account for torsional irregularities and hence results will be better for regular plan shapes as compared to irregular ones.

C) portal method

Step-by-step explanation

The portal and cantilever methods are two approximate methods for analyzing tall buildings for lateral (wind or seismic) loads - nowadays used for preliminary design purposes. The portal method is suitable for buildings likely to deform in shear mode. It is based on the distribution of base shears proportional to influence areas. Assumptions made in Portal Method:- 0 Point of inflexion occurs at the mid-height of vertical member (Le. column) 0 Point of inflexion occurs at the mid-length of horizontal member (i.e. girder, beam) 0 The Interior column carries twice the horizontal shear than that of the exterior column at each story. The cantilever method is suitable for slender buildings likely to deform in flexure mode. It is based on the distribution of base moment as axial forces on columns proportional to their distance from the centroidal axis of the building. An assumption made in Cantilever Method:-

Point of inflexion occurs at the mid-height of vertical member (i.e. column) . Point of inflexion occurs at the mid-length of horizontal member (i.e. girder, beam) . The axial stress in a column is proportional to its distance from the centroid of the cross-sectional areas of the columns at a given floor level.

The Methods portal and Cantilever method are used for analysing approximate Value of lateral " Loads be it due to kind (oo) Seismic Variations . > The difference in both the methods is where there used for example the portal method is used for buildings where the shearmode is responsible for any kind of deformation in the building .