"In this blog, i am going to share my experience gained in site visit as well as coordinating with different teams like architect, MEP engineers and contractor and few flaws during construction stage and post construction will help you to be cautious as far as co-ordination is concerned"
------- if chaos is created at site due to ambiguity in drawings then be cool, calm & audacious & behave like a spartan & don't loose faith in yourself if you are correct "
CO-ORDINATION AT OFFICE:
PPR(Preliminary Project Report) Level:
When any project is assigned, an architect make tentative planning & costing i.e(PPR). In this stage , architect submit preliminary cost of the building with some percentage of deviation with few schematic drawings. Structural engineers hardly have any role in PPR stage except for the foundation type that is most likely to occur in the proposed building.
Architect determine preliminary cost by plinth area rate provided by CPWD or state PWD. In this plinth area rate for structure,foundation type shall be mentioned which is most likely to occur in the structure & structural engineer helps architect from soil type or foundation type in the vicinity of the existing building or kind of structure which is to be made. At PPR stage, there is no chances of co-ordination failure as far as cost and stability of structure is concerned.
DPR(Detailed Project Report) Level:
This is the most important stage in which drawings like architectural, structural, MEP and other services are prepared taking all specifications so that there may be little or no deviation at the construction level if tender is done on the basis of cost made on these drawings.
Proposed project become fragile and every flaws come in scanner of everybody's eyes when things are exposed as a co-ordination failure among different bodies like architects,structural engineers ,PMC and site execution teams.
This can be understood from a simple example . let's say, architect decides floor height of a building without consulting any HVAC engineer. Later on ,during preparation of HVAC drawings, if HVAC teams demand to raise the height of the building in order to carry the AC duct. If floor is raised in the DPR stage, then it will increase the cost of the building as height of the columns will increase. If architect does not increase the floor height, it may affect elegance and aesthetic of the building. To maintain the same proposed height,architect may consult structural engineers to make sleeves in the beams to carry the AC ducts. In this condition, structural engineer may deny the proposal of sleeves in the beam as the provision of duct might not have taken in the design of beams. From this, a hue and cry may occur between coordinating department & this is not healthy for any organisation. Also, it may tarnish the image of any company.
Furthermore, turbulence between client and design consultant & it's impact on financial,functional and stability of any structure can better be understood from a another example. In this example, i will walk you through the failure at the master planning level in which architect may have not taken the set back and existing building properly in the master plan. Also, when the proper layout of existing structure is missed in the survey plan and level showing as a contour is not shown properly in the survey plan then these ambiguity creates turbulence at the site when foundation drawings made on the available data is not matching with the actual site. Due to ignorance of the proper layout of existing structure ,there may be a clash of foundation of proposed building with the foundation of existing structure. In that case, foundation shall be revised and most probably that shall be eccentric. In doing so, different provisions like foundation beam or tie beam shall be applied in the foundation system to ensure stability. Ultimately it will affect the cost of the project and will delay the project due to delay in approval from client.
Actually level in foundation drawing is shown as per the contour provided in the survey plan /master plan/site layout. Therefore, at actual site during construction,if the contour provided on the survey plan does not match with the level in the structure drawings then foundation system will be changed if the difference in proposed level and existing level is too high. To ensure stability and strength in the structure,additional tie beams shall be provided and additional filling load shall be applied in the design of the foundation. It will increase the size of the footing. Hence,incorporating these changes, there will be a huge cost implication of the project . Ultimately, it will delay the project.Client may hold the project and can impose penalty to the consultant if the deviation in the cost is too high. Also, contractor will not able to survive at site due to lack of work front due delay in delivery of approved drawings. Contractors can also pack up his team consisting labor and engineers/manager due to huge mobilization cost.
CO-ORDINATION AT SITE:
Before casting slab, electrical and plumbing pipe layout and certain cut out /sleeves for for fire fighting work shall be done . If any of the above is missed, then altering these will lead to vibration in the structural system and some cracks will induce in the brick walls,beams,columns etc.
I am going to share you one of the most frivolous act at site. You can say it a crime if i am not exaggerating it.Actually, in one of my project,ground floor roof slab was sagged . Because of that there was a hue and cry at site as well as at design office. Contractor started blaming design consultant stating that slab was sagged due to inadequacy or design flaws. On reviewing drawing and calculation at office,it was found slab design safe and stable as far as strength and serviceability was concerned. Later on investigating at site, it was found that slab was sagged due to placing prop for slab over sand at the plinth level. During pouring concrete over slab,there was slurry leakage through the shuttering. When these leaked slurry came in contact with the sand, sand started sinking & because of this, prop over this sand also started sinking. Hence, slab got sagged although design was safe. Hence, i will request all structural engineer not loose hope if this kind of things happen at site. Please be calm and cool and review all design calculation to defend faulty construction at site.
You can never say every failure of building is only due to design flaws. Failure can also occur due to poor workmanship and using low standard materials.
Also, i have seen many beams and columns over bulged at site. This bulging is due to use of poor shuttering and poor workmanship. If face of shuttering in beams and columns are not tied with tie bars or other arrangements, then it can lead to bulging of beams and columns.
Apart from this, excessive honey combing in structural elements may occur due to bleeding and segregation of concrete when excessively vibrated or poorly design of concrete in green state.
Note: It's my humble request to all structural engineers.Please don't feel low or discouraged if somebody blames you for any kind of ambiguity at site. Instead of wasting time to convince layman, you need to go back to your calculation and behave like a spartan & show audacity if you are correct and produce bravely your design documents and drawings of other coordinating bodies on the basis of that structural drawings were made.
Mohammad Sohel Akhtar(MSA)