LOAD TRANSFER MECHANISM IN A STRUCATURAL SYSTEM

LOAD TRANSFER MECHANISM IN A STRUCATURAL SYSTEM

The process of transfer of exposed load from one structural element to the other structural element is called as load transfer mechanism. Load transfer mechanism basically depends on the elements on which load transfers, this is referred to as load path. Based on the load path the pattern of load transfer mechanism varies which in turn depend on the type of load which the structure has to transfer.

Generally there are two types of load paths they are

1.     Gravity load path

2.     Lateral load path

Gravity load path: In this type of load path the vertical gravity load; which includes the dead load of the structure and live load on the structure acts on the slab are efficiently transferred to beams, from beams it is then transferred to columns and from columns to the supports, finally from the supports to the underlying earth.

The load transfer mechanism of gravity load path is generally shown by the figure below

                             

        Pattern of load transfer in gravity load path

1.     In case of transfer of the load from slab to the adjacent beams the triangular or trapezoidal pattern is followed, which in turn causes additional torsional moment on the beam at its ends.

2.     The loads received by the slabs on the beams at the joints will causes in bending of the beam and the results to form 3 reactions at its end position  

·        One in vertical direction - Acts as an axial load on the neighboring column.

·        One in horizontal direction – Acts as a shear force on the neighboring column.

·      Moment at the end of the beam - Acts as a bending moment on the neighboring column.

3.     The loads on the columns transfer to the supports efficiently and further to the foundation soil. The structure can be said to be stable if the upward pressure by the foundation soil is equally resisted by the load on the structure.

Lateral load pattern: In this type of load path the lateral loads; which are the earthquake loads and wind loads are transferred efficiently through the building. The components of the lateral load paths are

a.     Horizontal components such as roof, floor and foundation.

b.     Vertical components such as shear wall and frames.

Pattern of load transfer in Lateral load path

1.     Roofs and floors which are also called as diaphragms; transfers load to the shear walls(also termed as the primary load resisting elements).

2.     Shear walls can also resist the gravity loads efficiently and further transfers the collective load to the foundation; inturn foundation collects loads from all the stories and then transfers it into the underlying soil.