Methods of Strengthening Reinforced Concrete Beam
Reinforced Concrete Beam: It is a compound material in which concrete’s quite low tensile strength and flexibility are contradicted by the inclusion of reinforcement having higher tensile strength. Whether this reinforcement is not necessarily steel reinforcement bars and is usually embedded in the concrete before the concrete fixes; this reinforcing schemes are designed to bear tensile stresses in particular regions of the concrete that may cause sudden cracking and structural failure.
Need of strengthening the Reinforced Concrete Beams: The need of strengthening of RC beams in a structure is generally happened by problems for degradation of material qualities with time, decrease in cross section, corrosion, wrong beginning design or the increment in the load demand of the building while it is used for a new reason.
All these problems make the existing steel bars in the beam unsafe that’s why a number of solutions are then applied to make them safe enough to bear the load.
Here are some solutions used to strengthen the RC beams:
Additional steel bars are added to the main reinforcement without increasing the cross section to the beam: This process is done when the reinforcement in the beam lost its capability to bear the loads applied on it; at first the concrete cover is removed from both upper and lower steel bars.
Then those bars are cleaned well and being coated with a specific material to stop corrosion. Some holes are made of 13mm diameter along the whole span of the beam under the slab with a spacing of 150-250m and the holes are increased to the total width of the beam and then filled with a pasting material with low viscosity.
Next the steel connectors are installed to fasten the new stirrups and the added stirrups are closed with steel wires and the new steel is installed into them. At last the whole surface is coated with cement and the concrete cover is poured over the new steel and stirrups.
Additional steel bars are added to the main reinforcement the cross section to the concrete is increased: When both the steel and concrete are became incapable to bear the additional loads on the beam then this process has to be done with the following procedure.
After applying the above procedure, at last the whole surface is coated with cement to increase the bond between the old and new concrete before pouring a low shrinkage concrete.
Adding Steel plates to the beam: To strengthen the resistance of beam against the applied moment, steel plates are attached to the beams after designing with the right size and thickness by applying the following process: The surface of concrete is cleaned and is coated with bonding cement, then holes are made in the concrete surface and the plates, next a layer of cement of 5mm thickness is placed on top of plates. Then the steel plates are attached to the concrete by bolts.
Though sometimes it becomes important to decrease the load on the beam and this reduction can be either partial or complete unloading.
Article Source: civildigital.com