Some useful tips to strengthen RC beams
Because of deterioration of material characteristics in due course, curtailment in cross section, corrosion, improper preliminary design or the boost in the load demand on the building when it is used for a new purpose except for it was supposed to. For the above mentioned issues, the subsisting steel bars in the beam turn out to be insecure or inadequate. To get rid of these issue, the following measures should be taken :-
Inclusion of steel bars to the main reinforcement devoid of raising the cross section of the beam:
This method is undertaken when the reinforcement in the beam can’t bear the stresses enforced to it. Under this method, initially, the concrete cover is detached from both upper and lower steel bars. Then the steel bars are cleansed properly and they are coated with a certain material to resist corrosion. Holes of 13mm diameter are provided along the entire span of the beam under the slab maintaining a distance of 150-250m.
These holes are expanded to the total width of the beam and are stuffed with an epoxy material having low viscosity. The steel connectors are set up for binding the new stirrups. In order to tie up the steel bars affixed to the beam, steel connectors are provided into the columns. The affixed stirrups are concealed with steel wires and the new steel is placed into these stirrups. Then, a bonding epoxy material is used to coat the surface. The concrete cover is poured over the new steel and the new stirrups.
Inclusion of steel bars and expanding the cross section area of the concrete
This method is suitable when both the steel and the concrete don’t have the capacity to tolerate the stresses on the beam because of the extra loads. The method is given below:
Once the concrete cover is detached and the reinforcement steel is cleansed, coating it with the material to get rid of the corrosion. Create holes to the entire span of beam and to the full width under the slab maintaining a distance of about 150-250mm. These holes are stuffed with cement mortar having low viscosity. Steel connectors are provided to tie up the new stirrups. The steel connectors are provided in the columns to tie up the steel bars included with the beam.
The added stirrups are concealed with steel wires and new steel is provided in these stirrups. Then the concrete surface is coated with a particular material to keep the perfect bond among the old concrete and new concrete just prior to pouring of concrete that is a low shrinkage concrete.
Inclusion of steel plates to the beam:
In order to fortify the resistance of beam against the applied moment or the shear stress, steel plates are affixed to the beams once they are designed with the proper size and thickness. The method is given below:
Initially, the surface of concrete where the plates should be affixed is cleansed. Then, a bonding epoxy material is used to coat the surface. Holes are created in the concrete surface and in the plates, then, a layer of epoxy mortar with thickness of 5mm is provided on top of plates. These steel plates are then affixed to the concrete with bolts.
In some situations, it is essential to lessen the load on the beam that requires strengthening prior to implement the techniques. This lessening of loading can either be partial or complete unloading. It is done by providing steel beams on top or under the concrete beam.
