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Thursday, February 25, 2016

Viewing node and beam numbers in staadpro

To view node and beam number, right click anywhere in drawing area.
Dialog box will appear.
In it choose Labels.



Turn the node points, node numbers and beam numbers on.

Than click OK.
The structure will display node points, node number and beam number.

Sunday, February 14, 2016

Quality Control

In India, with a view to ensure construction quality various bodies formulate guidelines & specifications. Some of the main institutions/ bodies are as under:-
  • Bureau of Indian Standards  - BIS
  • The Indian Roads Congress - IRC

BIS is a statutory institution established under the Bureau of Indian Standard Act, to promote harmonious development of the activities of standardization, marking and quality certification of goods. The standards are revised periodically, keeping in view the rapid development in field and to bring in further modifications/ improvements in light of experience gained while using the earlier version of the standard. Earlier this was known as "Indian Standards Institution".

The BIS codes give detailed guidelines for:-
  • Material specifications and testing.
  • Construction methods and practices.
  • Soil Investigation
  • Design of RCC including reinforcement detailing from seismic considerations
  • Design Steel structures including welding.

Friday, February 12, 2016

Electrical installations specifications

EARTHING

  • The masonry chamber for earthing should have brick masonry foundation.
  • The chamber should be constructed in such a manner that 40 mm diameter G.I. pipe earth electrode is at the center of the chamber.
  • The pipe electrode should be buried to the correct level such that its top is not less than 20 cm below ground level.

 WIRING





  • Before fixing switch boxes in the wall, the space behind switch boxes should be filled with mortar properly.
  • The height of power plug/ light plug should be kept at least 125 cm above the floor and 30 cms above kitchen platform level.
  • The accessories like bell push, light, control switch, socket, etc. if provided in an area exposed to rain, they should be suitably protected by providing covers.
  • Wires should be drawn in the conduit before plastering.
  • Shock protector unit is to be provided to prevent any untoward happening in the building.
  • The in coming supply of power from the street should be through a cable of adequate size and laid in a pucca cable trench covered with RCC slab.  
  • Installation of MCB-DB is preferable, since it will protect the wire from damage, due to over-loading.
  • All wires between which a difference of potential of 240 volts exists shall be made inaccessible to unauthorized persons or enclosed in a conduit.

Water Supply and Sanitary Installation specification

  • Lead totally inadequate in joints of C.I. pipes.
  • Poor and weak concrete with inadequate reinforcement in water storage tanks.
  • Pipes used are of less thickness/ diameter and not of proper grade / make.
  • Joints in sewer lines not tested.
  • In some cases, C.I. pipes and specialised corner reinforcement are embedded in lime mortar or cement lime mortar or cement lime mortar or lime concrete. This will result in accelerated corrosion of steel. In these cases, only cement concrete 1:2:4 only should be used.





Rehabilitation of Town Hall Shimla

Shimla district it is bounded by two major thrusts :

  • Main Central Thrust (MCT)
  • Main Boundary Fault (MBF)
There are other thrusts presents in region, such as the Jwalamukhi thrusts and the Drang thrust.

Shimla can expect maximum peak ground acceleration (PGA) of 4 meters per second square. Hence Shimla can expect an earthquake of seismic intensity VIII on Modified Mercalli (MM) Intensity Scale.   



Townhall Project was constructed during 1st decade of 20th century and it was a steel frame structure. At that time, steel frame technology was latest technology of that time. This building has withstand all the earthquakes till date, so it should be retrofit for next millenniums.

Detailed investigation was done for settlements, cracks, fissures, seepage and distress.

Dynamic cone penetration test (Dcpt) were conducted at 6 locations in January, 2014. Out of which 3 location were adjacent to Town hall on Ridge road.
Allowable bearing capacity arrived from test was (qa) Net=13 t/ m2 and (qa) Gross = 15.6/m2.





by Mr. Nigam

Wednesday, February 10, 2016

Roofing specifications

C.G.S Sheet Roofing:

  • Slope of roof not flatter than 1 vertical to 5 horizontal.
  • In case of roofs having slopes less than 1 vertical to 2.5 horizontal sheets, not joined together at the side laps by galvanized iron bolts and nuts of 25 * 6 mm size, with bitumen and a GI limpet washes.
  • Holes for bolts punched and not drilled from the underside.

ACC Sheet Roofing:

  • The distance between the edge and the holes is less than 40 mm.
  • Roof ladder and planks not used while laying the sheets.
  • Side lap not lay on the side.

 Rain Water Pipes:

  • The pipes used are not of specified size, diameter or weight.
  • M.S. hold clamps not of required shape and size.
  • Clamp hooks not embedded in concrete blocking.
  • Joint not kept for 7 days.


Flooring Specifications

  • Cement concrete flooring not laid within 48 hours of laying of cement concrete sub-base. In case of lime concrete sub- base, cement concrete flooring is to be laid after 7 days and not later than 10 days.
  • Surface of sub - grade is not roughened with steel wire brushes.
  • Cement slurry not applied at 2 kg per sq.m either to sub- grade or to RCC slab before laying the flooring.
  • Concrete of floors not beaten up to get the cream of mortar.
  • Thickness of flooring laid is less than what is specified.
  • Sprinkling the dry cement or mixture of sand and cement to absorb excessive moisture.
  • Curing not done for a minimum of 10 days.
  • Overlapping of edges of panels.
  • Sometimes, tiles/ stones are laid on a bed of dry mortar, this will result in flooring sounding hollow when tapped with a wooden mallet. Some tiles working loose and there may be no bond between the stone/ tiles and the sub- grade or RCC slab.
  •  Finishing slope not properly done especially in kitchen, bathroom and balconies. Sometimes, slope provided in the reverse direction.
  • In case of marble chips flooring, it is not laid between 18 to 24 hours after the laying of under layer.
  • Flooring should confirm to IS: 777 and terrazzo tile flooring confirm to IS: 1237.  


Terrazo Tile Flooring:

  • Thickness of tiles not as specified.
  • Tiles do not have required transverse strength.
  • Thickness of bedding mortar less than 10 mm.
  • Cement slurry not applied @ 4.4 kg/sq.m before laying tiles.
  •  First grinding of tiles not done in factory before delivering at site.


Marble/ Kota Flooring:

  •  Average thickness of bedding should be 20 mm and not less than 12 mm at any place.
  • Cement slurry not applied @ 4.4 kg. Per sq. m. over the bedding mortar before laying stone slabs.
  • Thickness not as specified.





Daddooing/ Skirting:

  • Dadoo not flushed with well wall plaster or not projecting uniformly by 6mm from the wall plaster.
  • Dadoo not laid along with border or adjacent floor panels.
  • The joints in the dadoo/ skirting not kept true and straight in continuation of the line of joints in borders or adjacent panels. 

    Monday, February 08, 2016

    Wood Work Specifications

    • Wood used has cracks.
    • Application of putti is not uniform.
    • Screws are nailed instead of being screwed.
    • Moisture content in wood is more than permissible limits.
    • Hold fasts are directly fixed in wood instead of concreting.




      Brief Specifications for Wood Work: 

      • Frames of joineries may be made of timber. Usually, teak, deodar or rose woods have high demand.
      • They should be treated with preservative and termite resistant chemicals. The finish product should be free from knots, cracks, twists, or, warps.
      • Maximum moisture content in seasoned timber should not exceed 8 % to 14 % depending upon the use and thickness. Details can be referred from IS: 267.
      • The plywood used for panelling of door shutters should be BWR (Boiling water proofing) grade.

      Sunday, February 07, 2016

      Steel work specifications

      • Steel sections with excessive rust.
      • Primary coat is not applied.
      • Welded fillets not well formed and filed.
      • Large gaps between masonry and joinery frames.
      • Finish of steel grills for windows unsatisfactory.

      Brief Specifications for steel work:

      • The ordinary quality of steel designated as SI: 320 conforming to IS: 1977 shall be used for windows frames, door, window bars, grills, steel gates, hand railings etc.
      • The finished material shall reasonably be free from cracks, surface floors lamination's, rough and imperfect edges, excessive rust scaling and pitting.
      • The primer to be applied for steel work is zinc chromate conforming to IS: 104.
      • Welding should be made in the flat position, wherever practicable. The member, which offer the greatest resistance to compression to be welded first.
      • Weld should be free from cracks, discontinuity in welding and should not be undersize, oversize, undercutting or over cutting. The surface of weld should be free from porosity, cavities, burnt or scale.
      • Following inspection and testing should be done.:
      • Visual inspection.
      • Bent testing.
      •  Tensile testing.
      • Magnetic particle radio graphic testing. It should be done as described in IS: 1182.

      Saturday, February 06, 2016

      Staadpro- Generating the model geometry

      • First select add beam option given under geometry icon in menu bar. This will initiate a grid in the main drawing area as shown below.

       The directions of the global axes (X,Y,Z) are represented in the icon in lower left hand corner of the drawing area.

      • Snap Node/ Beam Dialog box appear in the data area on the right side of the screen.

      Linear tab :    is for placing the construction lines perpendicular to one another.
      Radial tab:     it enables construction lines to appear in a spider- web style.
      Irregular tab:  used to create grid lines with unequal spacing that lie on the global planes or on an inclined planes.

      Stone work Specifications

      • Bushing is more than specified (should not project more than 4 cm on exposed face and 1 cm on the face to be plastered).
      • Stones not wetted before use.
      • Mortar not mixed with mechical mixer.
      • Proper bond between two connected walls not provided.
      • Stones with round surface not to be used.
      • Stones not tested for water absorption.
      • Sand used has more silt content or contains harmful sulphates/ chemicals, fineness modulus not checked.



      Friday, February 05, 2016

      Brickwork Specifications

      • Inadequate soaking of bricks.
      • Strength of brick less than specified.
      • Thickness of joint exceeds 1 cm.
      • Expansion joint not provided.
      • Parapet walls of balconies, landing and staircases are constructed with 7 cms thick brick masonry, in cement mortar. This is an unsafe method as the walls are likely to collapse, due to horizontal force. In these cases, it is necessary to reinforce them. 

       Following steps needs to taken out to avoid defects in brick work:

       

      • Bricks required for brickwork shall be adequately soaked in stacks before use by spraying with clean water at regular intervals for a period of not less than 6 hrs before use so as to keep them wet.
      • Vertical joints in alternate courses shall come directly one above the other.
      • Work done per day should not be more than 1 m.
      • Horizontal runs of water supply pipes should be avoided in masonry walls.
      • Sometimes, holes are punctured in the staircase walls to support the landing slabs to accommodate the beam over which staircase beam rests. Before doing this, the resisting capacity of brickwork should be checked.
      • Sometimes, openings are made temporarily in load bearing walls to use as entrance from one room to another. This reduces the strength of the wall due to the reduction of the wall area designed for. In case, openings are to be made, the strength of brickwork to resist the load at the bearing is to be checked.
      • Top course of plinth, parapet, steps and top wall not provided with brick on edge.
      • While plastering, joints in masonry works should be racked to provide a good key between plaster and masonry.
      • Whenever masonry partitions have length to height ratio higher than two, horizontal reinforcement is to be provided in the masonry.
      • If sulphate content in soil exceed 0.2% or in ground water exceeds 300ppm, it will attack various components of the building. To prevent this, sulphate resisting cement is used.

      Specifications for Bricks:

      • Size of brick should be 9" * 4.5" * 2.75" or (20* 10 *10 cm).
      • Brick should be free from cracks and nodules of free lime.
      • It should be tested for:
      • Compressive  strength.
      • Water adsorption.
      • Efflorescence.
      • Dimension.







        Thursday, February 04, 2016

        RCC Concrete specifications




        • Concrete in one layer should not be more than 15 cm.
        • Hacking of surface should be done immediately after removal of centering and shuttering.
        • When concrete is placed especially in floors and pavements, solid particles of the ingredients of concrete begin to settle down by gravity action and water rises to surface. This process is known as 'bleeding' it should be ensured that the evaporation of water is lower than the rate of bleeding. This can be achieved by covering the top by wet burlab (a coarse canvas), especially during hot seasons.
        • Shrinkage cracks can be controlled by using temperature reinforcement with about 0.12% (if high strength deformed bars are used, refer clause 26.5.2.1 of IS: 456-2000) of cross sectional area of concrete both horizontally and vertically. It is perferable to use bars of smaller diameters at closed intervals.
        • Curing of concrete should be commenced immediately after the setting has taken place and proper curing should be done for 28 days, but concrete members (slabs/ columns) must be completely immersed in water for at-least 10 days and should be kept wet by repeated spraying for the balance period.
        • For vertical fascias, RCC vertical projections are to be provided and not brick masonry. This applies for sun- shades also. This is to avoid horizontal cracks at the joint between slab surface and the masonry.
        • Catwalk should be provided to prevent disturbance to reinforcement as well as already laid concrete. 

        Tuesday, February 02, 2016

        Concrete Specification

        Non compliance of proper specification during construction results in failure of structures.

        •  Sand contains harmful sulphates/ chemicals, which affect durability of concrete.
        • Silt content present is more than permissible limit.
        • Fineness modulus not checked.
        • Inadequate mixing time.
        • Slump test not performed regularly.
        • Coarse aggregate oversize.
        • Test registers are not maintained. In some cases test are not done and in some other cases tests results are fictitious.
        • Less cement used. Accelerator should be avoided.
        • Beams made to span over larger openings in load bearing walls and in some cases where intermediate support is provided, the support is not tested to resist the compressive strength.
        • Providing reinforcement in conjested manner, making it difficult for concreting conditions. This result in weak pockets, which will permit accelerated corrosion.
        • Bearings of lintel and beams are less than 9 cm or 1/10 the span.
        • All load bearing walls should be provided with lintel band with minimum reinforcement of 2 no. 10 mm diameter tor steel bars, one at each face of the wall with 12 mm cover and 6 mm stirrups and 150 mm cement concrete.
        • Sometimes, the size of beams is out of plumb and buldge out. To avoid this, the bottom plate should be made wider than the finished width of the beam.
        • The top of the side shuttering should be prevented from tilting outwards by provision of inclined wooden struts nailed to the shuttering and bottom plate.
        • The concreting should be done in strips of width 1.5 meters to the length of the unit so that the thickness of the concrete is uniform throughout.
        • Concrete is not laid gently but poured or thrown from a height resulting in segregation.
        • "U" shape ties in pairs may be provided to form a close stirrup with the proper development length taken inside the beam. In such case, development length cannot be provided and "U" shaped ties may be be hooked around reinforcement and bent for 180 degrees and taken for 10 degrees beyond the end of the curve.
        • In case of highly corrosive environment with high sulphate/ chlorine contents in the sub- soil water, anti- corrosive reinforcement or galvanized reinforcement can be used or anti- corrosive coatings can be given.

        Earthwork Specification

        It has been observed that non compliance of proper specification during construction results in failure of structures.

        • The type of foundation suitable for the building on the proposed site is to be decided only after conducting the soil test and getting the opinion of the experts. This is not usually done in many cases.
        • Initial levels for filling or cutting not recorded.
        • The foundation base is not levelled by concrete except in the case of rock beds.
        • Shoring and strutting is not done to prevent collapse of sides of foundation in weak soil.
        • When horizontal expansion is done for a building, the new construction should not be bonded with old and the two to be separated by expansion joint right from bottom to top. No excavation below the foundation level of old building should be made. In case of framed structure, twin columns can be provided with a combined footing and the footing will be done along with old building.
        • Black cotton soil/ Shrinkable clay which swell and shrink are extremely crack prone and for such type of soil, special type of foundation like under- reamed piles are to be provided and the bulb of the pile is to be taken to a depth, which is not much affect by moisture variation.

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