Building Maintenance MCQ Questions & Answers | Civil Engineering

The structural concrete slab panels can be repaired by external bonding of steel plates to the soffit by using epoxy adhesives and hollows.

The inspection more intensive involving examination of structural elements is Major inspection. It even require setting up of special access facilities where required depending upon the importance of the structure. This inspection is generally spaced between 2 and 3 years.

In the form of surface cracks prestressed concrete structures shows visible signs of distress. Spalling of concrete should be special inspection using instruments to users the extent of damage to the structure.

Strain gauges is one of the testing equipments used for inspection. Modern testing equipments which could be of use to the specialized inspection team are listed below: Rebound hammer compressive strength (Schmidt hammer), ultrasonic pulse velocity detection of cracks, snooper-crawler and adjustable ladders, magnetic decor for measuring thickness of concrete cover and for locating reinforcement bars, mechanical extensometer, transparent templates and microscope for reading of crack widths on the surface of the concrete hydraulic jacks, pressure transducers or load cells for measurement of forces etc, electronic strain gauges for measurement of strain in concrete and steel, vibration measuring equipment, electrical resistance meter(for rust pockets).

The pachometer is used to locate the Steel reinforcement. A wide variety of electronic equipment is presently available in the market in many countries for monitoring and inspection of distress in different types of structures and ultrasonic meters are used to determine the degree of deterioration and distress and / or material imperfections that are relevant to the structural integrity of the structure to be inspected and pachometer is used to locate the steel reinforcements and measures the sizes of the bars embedded in concrete to an accuracy of 3m.

Barins snooper vehicle is used to inspect in case of bridge greater than 10.7m in height and which cannot be inspected from beneath due to watery situation. The snooper is mounted on a heavy duty truck with a swiveling platform and the underside of the bridge deck can be inspected by using the hydraulically operated platform.

In the case of dormant cracks wider than about 1m, it is more economical to use grouting and sealing technique. This method involves enlarging the crack along its exposed face and then the crack is cleaned and grouted and the surface is then sealed with a suitable joint sealant and various other techniques widely used for repair of dormant or dead cracks include dry packing, polymer impregnation over lays and surface treatments and autogenous handling.

Three types of sealants are used depending upon their suitability in a given situation. They are: Mastics are asphalts with a low melting point with added fillers or fibers and they are recommended where the total movements will not exceed 15 percent of the width of groove, Thermoplastics comprising of asphalts, pitches and coal tar become liquid or semi viscous when heated and the groove depth to width ratio should 1:1 and the total design movement is of order of 25 percent of groove width and Elastomers include a wide range of materials such as poly sulphides, epoxy poly sulphides, poly urethane, silicones and acrylics and these materials advantages since they can be used without heating.

There are three types of damages present. These are minor damage, moderate damage and several damage. Minor damage requires superficial patching by using epoxy grout or guniting using Shortcrete and the damages and delaminated concrete is removed by hand tools and the surface is cleaned before the application of epoxy grout, moderate damage involves extensive spalling and cracking of concrete is generally applicable as in minor repairs and in Several damage Prestressed concrete girders requires a detailed structural analysis of a design check based on the conditions of the damage and the best engineering assumptions and judgments.

Preloading methods should be considered in making concrete repairs if the loss of prestress is excessive resulting in tensile cracks. This is done in order to restore the equivalent full or partial prestress effect, as per original designs.