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TIME TO HEAL OUR STRUCTURES

  • Use of standard and innovative repair materials, appropriate technology, proper workmanship and quality control during implementation are the major factors for successful repair strengthening
- Anjan Kuinkel, Kathmandu

Oct 12, 2015-Retrofitting is the process of changing technology or adding entities to a building that ultimately results in the addition of strength of the existing structure without its demolition. With better understanding of seismic design on structures and on the crucial experiences from the recent earthquakes, the need of retrofitting is on high demand. Steps of retrofitting comprises: assessment of structure, evaluation of seismic forces acting on the structure and selection of retrofitting strategies including their proper implementation. Its application ranges from typical Nepali residential houses to high raise multiplexes, bridges and transportation structures.

During my survey visit of Rapid Visual Assessment, under Nepal Engineers’ Association, I found out an amalgam of existing buildings in our society: from old to newly constructed, illegally-made to well -designed, humble brick to gleaming new multistory structures. As the two recent massive earthquakes hit Nepal, a large number of houses without seismic design were leftdamaged. The main causes of the damage are predating modern construction practices by old decaying and less durable materials and construction of newer buildings without the application of proper seismic codes.  Current earthquake codes are applicable to newer houses only and aren’t applicable to the buildings without earthquake resistant features.

There are multiple aspects of retrofitting. Engineers can prepare and design retrofitting approaches by compiling with the building codes. Recently developed materials and techniques can play a vital role in structural repairs, seismic strengthening, and in retrofitting processes.

Injecting grout, a construction  material used to embed rebar in masonry  walls, connect sections of pre-cast concrete , fill voids, and seal joints, into walls in order to fill the voids or cracks formed due to deterioration of a building is one of the finest and most common methods applicable to all the houses comprising of minor cracks. Existing large number of cracks can be stitched together with steel bars and mortars. This will help in restoration of stiffness in the structures. Addition of shear wall and bracing is another relevant strengthening method to overcome deficiencies in strength. Addition of multiple proper ad mixtures in the concrete can help generate proper strength; it also improvises the bonding between older and newer structures. Engineers must keep in mind that the new loads to be carried by these elements should be efficiently delivered without deficiency in load path.

The general problem our houses have is that they have small pillars designed without the application of building codes. The answer to this problem is concrete jacketing; it will widen the area of structural member which finally enhances strength of the whole structure. Another common problem that almost all our houses is facing is the presence of cracks near openings i.e. door and windows. Installation of new lintels in these areas will help repair and strengthen.

The phase we Nepalis are going through is the sensitive one. In this context, we need to retrofit our structures to restrain upcoming massive earthquakes in our future. Proper analysis of an expert is essential to make the phenomenon of retrofitting economical and reliable. Use of standard and innovative repair

materials, appropriate technology, proper workmanship and quality control during

implementation are the major factors for successful repair strengthening and restoration of damaged structure.

Kuinkel is a final year student of Civil and Rural Engineering from Nepal Engineering College

Published: 12-10-2015 09:15

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