With the increasing expansion of urban scale and the concentration of urban population in China, more and more fires occur in China, causing great casualties and direct economic losses, while structural damage or functional failure caused by building fires may also lead to greater economic losses and casualties.

Whether and how to repair the buildings after the fire is an important issue that people pay attention to after the disaster. For a long time, it has relied mainly on experience and subjective judgment, or repair, or overthrow reconstruction.

For example, the first floor of a factory building is a frame structure, and the second floor is a steel roof structure with frame columns. Fire broke out in the adjacent buildings of the building. The fire spread to the first and second floors of the building. After the fire broke out, the fire was extinguished by spraying water on the spot for about 7 hours, and the combustion temperature was about 300 ~800 C.

On the basis of testing and appraising the damaged building structure after fire and calculating the residual bearing capacity, according to the principle of reinforcement, the damaged structure can be repaired and strengthened. The reinforcement technology of concrete structure can be divided into direct reinforcement method and indirect reinforcement method.

The damage degree of damaged components after fire can be divided into mildly damaged components, moderately damaged components, severely damaged components and dangerous components. For the lightly damaged components after fire, the batch modified epoxy mortar surface can be used to reinforce the structures.

Reinforcement Scheme Taking Fire of Factory Building as an Example

Structural aspects: removing burnt concrete, repairing and restoring concrete cracks, anchorage measures for reinforcing steel bars, replacement of excessive deformed steel bars and so on.

Reinforcement of frame columns and frame columns: For beam-column members, batch modified epoxy mortar is used to reinforce them when the damage rating is IIa, and high strength composite mortar steel wire mesh is used to reinforce them when the damage rating is IIb.

When the damage rating is III, the column members are strengthened by wrapping angle steel, the beam members are strengthened by sticking steel plate, and when the damage rating is IV, the reinforced members are strengthened by enlarging section or replacing concrete.

Particular attention should be paid to the safety measures such as lightly chipping loose sparse burnt layer, not vibrating burned columns, strictly preventing secondary collapse, and strengthening brackets when necessary. Before strengthening the beams, the live loads on beams and slabs must be removed before loading can be completed after the reinforcement construction.

Floor reinforcement: When the damage rating of slab members is II A and II b, the surface layer of epoxy mortar modified at the bottom of slab is used to reinforce the slab members; when the damage rating of slab members is III, the chiseled concrete is used to re-pour.

The structural condition of buildings after fire is complex. Designers should adjust and improve the structural details of reinforcement design at any time according to the actual burns of damaged components of buildings after fire. At the same time, the durability of structures within service life should be considered.