Repair Mantenance & Material Testing

Repair Mantenance & Material Testing

Repair and maintenance of structure

Building like all other structures is design to support loads without undergoing excessive deformation. Structural failure refers the lots of load carrying capacity component or member within a structure or structure itself.

Structure failure is initiated when a material is stress or loaded to its excessive deformation.

Self-load

            Type of dead load due to self-weight of member of design.

Dead load

            Load that retains its magnitude and point of application throughout the life of structure is dead load.

Live load

            Load due to person s occupying and there belonging like furniture sand books. Its change it magnitude and point of application of load.

Imposed load

            All external loads leaving the self-load acting on the member of structures.

Service load

            Maximum intensity of loads expecting during the life of structure depending upon certain probability of occurrence is called service load.

                                    Service load increase but some factor of safety is called factor load.

Wind load/E.Q load

            These are types of lateral loads that will be considered depending upon the probability of occurrence of those loads.

                        Causes of building failure

Bad design

            It’s due to failure accounts the loads that structure will carry.

·         Erroneous theories

·         Reliance upon inaccurate data

·         Ignorance of repeated loads

·         Improper choices of materials

Faulty construction

            Faulty construction is the most important causes of structrual failier due to following reasons.

1.      Bad inspection during construction phase.

2.      Use to salty sand to make concrete.

3.      Substitution of infernal steel on place.

4.      Bad riveting or welding.

Structural failure

Structure failure refers to lots of load carrying capacity of a component or member within structure or structure itself.

            Structural failure initiated when material is stressed beyond its strength limit.

     1.      Design deficiencies

     2.      Material deficiencies

     3.      Substandard work mentioned

     4.      Poor sight investigation

     5.      Poor detailing of reinforcement

     6.      Deferential settlement

     7.      Defect in RCC work

Design deficiencies

      The design of building should be such that it can fulfill the function for which it is intended to be.

Material deficiencies

      Material deficiencies are accruing by using inferior building material that causing a verity of defect.

Substandard work mentioned

      This category of construction defect usually becomes evident with water seepage through some part of building.

Poor sight investigation

      Sight investigation should be done properly.

Poor detailing of reinforcement

      Detailing incorporate are design process by which designer inshore that each part of structure

Can performed be safely under service load condition and when specially selected critical condition is to accommodate large plastic deformation. Thus detailing based on understand of a response of structure behavior.

Efflorescence

            Salts enter the wall from various sources. New brick sendom contains soluble salt but mortar and concrete have relatively high soluble salt content. Ground water that is naturally salt beating can be drawn into base brick wall. A faulty damp proof coarse bridged by water will allow the salts to migrate up the wall. The amount of water in brick and their drying time the more water in the bricks and the longer

It is there the more chance salts will have to design in it and be brought to the as the bricks dry out.

                                    i.            Brick work contains soluble salt.

                                  ii.            Brick work gets saturated and soluble salt dissolve.

                                iii.            Brick work dries out and rises to the surface.

                                 iv.            Water evaporates and leaves soluble salts on brick.

Preventions

         i.            Efflorescence can be minimized by avoiding the use of pours brick in contact with lime stone.

       ii.            Correct design of DPC and by providing coping.

Cracks in solid masonry wall

            Minor cracks are common but major cracks may be more serious as solid masonry walls are load bearing. Vertical cracks may require under pining. Cracks above window and door indicate weakness or failure of the lintel in which cause a new lintel should be installed.

Dampness

            Dampness in building is one of the most common causes of building failure. It can originate in many ways and can cause a verity of side effects on materials including plaster brake down, peeling of paint and timber decay. Building needs protection from.

            I.            Condensation

Which occurs is there is insufficient ventilation in the building.

          II.            Rising damp

Where water is sucked up throw the brick work at ground level through capillary action.

       III.            Penetration damp.

          Where water enters the brick wall through a leak or simply rain penetration into poor jointed wall.

Types of cracks in brick masonry

Vertical crack on external wall

            Vertical cracking may be due to different reason and occur at different location.

a)      Away from corner and top of building

b)      Near corner of brick building above D.P.C

     A.    Away from corner and top of building

            Cracks are usually widest at the top of the building diminishing to a hair line crack at or near foundation level they may run through the foundation or they may run only start above first floor opening often there will be a single crack in each of a opposite elevation of building and they may be connected by a crack in concrete floor or in a flat roof.

Causes

            This defect is a result of swelling of clay that was dried then normal when building was constructed.

Prevention

            The defect will only occur if the foundation is not deep enough to reach the subsoil beneath the dry clay when clay expand center of building there will be vertical crack in the center of façade. If expansion is at the corner it may affect only corner some time producing diagonal effects.

     B.     Near corner of brick building above DPC

A straight vertical crack occurring near the corner of the building starting at DPC and extending upward by varying dimension up to a high several meters this type of crack usually occur early in the life of the building but could occur at any time during 20 years of soil the DPC and DPC may be slightly squeezed out.

Causes

            This defect is caused expansion of brick some time in conjunction with thermal movement.

 Defect in timber structure

            At each stage of building life the choice of material used influences the durability of elements of the building. It is easy to understand that the performance of a building depends on the design and specification of materials, such design is based on the expected environment of the element of building. The full range of attack issues for timber during the life time of building is

    1)      Changing moisture condition

    2)      Resistance to wear and tear

    3)      Resistance to fire

    4)      Structural performs

    5)      Insect attack

    6)      The use of the structure

    7)      Additional protector measures

Timber decay

            Timber decay is caused by the biological attack on the wood by fungi principal environmental factors favoring decay of building material are temperature, humidity and lack of ventilation moisture may be contributed by penetrating or rising damp, condensation building defects such as leaks in water, concrete and plaster.

Effect of moisture

             Wood destroying fungi required a moderate amount of moisture for continued activity and if the wood can be kept sufficiently dry there growth can be prevented wood that is maintained at 20% moisture content is safe from fungus damage.

Effect of temperature

            Temperature between 15 and 90 F are optimum for fungi. As a temperature approaches freezing the fungi become dormant. Under proper circumferences untreated and unpainted timber can durable.

Preservative treatment

            The effect of preservation treatment is to make wood piousness to aggressive or organism. This is true with regard to decade fungi as well as insets. In practical use the properly treated timber often show the service life as much as five times that of untreated wood used for corresponding application. The following treatment can be applied to timber structure.

    1)      Brushes or spray coating

    2)      Dipping

    3)      Hot and cold bath

    4)      In place treatment

Type of preservatives

                                i.            Water borne preservation

The most common standard of wood preservative used in water borne solution include zinc chloride , chromated zinc chloride , copperezed  chromated zinc chloride, zinc meta arsenate. These preservative leaves the surface of wood reasonability clean and in a good condition to receive paint. As a result they are employed in principally in the treatment of wood for uses where architectural appearance or where appearance of creosoted timber would be objectionable zinc chloride and chromated zinc chloride used at high retention find further application as fire retardant treatment

                              ii.            Petroleum oils fortified with pentachlorophenol & copper nepthenate

These preservative like the water borne solution leave the surface of treated wood clean and point able. Pentachlorophenol does not change the color of wood but copper nephthenate gives it a green shade both solution are for inferior to creosote as a protection against marine borers how able they do wood protection against decay.

                            iii.            Creosote

In general proper treatment with creosote may be expected to give excellent result in preventing decay and insect attack. The advantages of creosote as preservative are as follower.

a)      Highly toxic to wood destroying organisms

b)      Relatively in solubility in water

c)      General availability

d)      Relatively low cost

e)      Wood depth of penetration

f)       Wood performs

Disadvantages

a.       Freshly creosote can easily catch fire

b.      It has distinctive smell

c.       It have a black color and appearance with is not aesthetically the placing and make it unsuitable for most architectural application.

d.      Contact with heavily treated timber creates a problem of irritation of sensitive skill.

e.       The treatment is unsuitable for decking because it is slippery.

Foundation failure

            Foundation failure means the failure of structural element of foundation and failure of soil it self. The first type of failure may be the result over the over load on the foundation and the second type results from over confident in the test borings and other subsurface investigation or loss of bearing capacity because of adjacent word. The most common categories of foundation failure are.

                         I.           Under mining of safe support.

                       II.            Load transfer failure

                     III.            Lateral movement

                      IV.            Unequal support

                         V.            Design and construction error

                      VI.            Vibration effect

          VII.            Earth quick effect

         VIII.            Soil softening

Under mining

      Need of thorough soil investigation prior to under taking of a construction project in addition to careful study of soil strata directly blow the proposed structure existing adjacent structure must reviewed with care.

Prevention

Careful preconstruction study to determine the need for protection this study include the review of existing planes taking sufficient soil boring and evaluating the condition and strength of structure. Excavation of sewer should be away from the exist structure. Use of vibratory equipment for pile deriving should be avoided in loss sand and similar soil.

Lateral movement

It is well known that the lateral movement is more dangerous then the vertical settlement. Lateral movement caused by the either the elimination of lateral resistance or the addition of active lateral and load.

Prevention

Foundation wall must be braced prior to any back filling. Only well controlled and drainable porus back fill should be placed against the foundation and other retaining wall to avoid the shrinkage of soil and development of high lateral soil and water pressure.

Unequal support

A basic rule of engineering is that no load can transfer without deformation. In other words all forting settle when they are loaded. The amount of settlement is equal for different forting when the soil resistance is identical and load distribution is equal. When they are not deferential settlement occurs. And portion of the structure founded on the weak soil will tilted away.

Prevention

      The building partially on the soil and on the rock have too often been designed on the incorrect assumption that the mere use of the locale building code s’ allowable bearing capacity value. Where such variable bearing condition exists a separation joint must be provided so that each section of the building behave as an individual separate structure.

Design construction error

Unfortunately many foundations are designed with insufficient subsurface investigation or with this regard of the true soil condition. A common design error is usually made in an afford to save initial construction cast while the main floor is placed on more or less compacted sand overfill peat organic salt and other compressible layer.

Vibrated error

            Earth masses which are not fully consolidated will change volume when exposed to vibrate. The vibration source can be blasting, construction equipment specially pile drivers, mechanically equipment in completed building equipment.

Prevention

            Use of vibratory pile deriving must be avoided where possible under pining of adjacent structure must be carefully done.

Earth quake effects

            Foundation is earth quake affected zone must be design to tolerate the expected shoke provided by nature. The effect of foundation is usually less sewer then on the super structure especially in earth quake of short duration. Where earth quake shake continuous for long period the subsoil structure substantially altered and a great deal of additional damage is caused as a result of failure of the foundation.