LIQUEFACTION OF SOIL- A BIG CHALLENGE & CONCERN FOR STRUCTURAL ENGINEER

“Even a sound and structurally stable structure is susceptible to failure if soil supporting structure undergoes liquefaction during earthquake. This is one of the biggest challenge for structural engineer. Reading carefully and attentively the geo-technical report and providing robust foundation or soil improvement is the only solution for this challenge.For solution, it is essential to know what is liquefaction and how does it happens. Without knowing the complete anatomy behind liquefaction,a suitable solution can never be found.

Feel the structure-MSA

As a structural engineer, we design foundation on the basis of data provided by geo-technical consultant. Whatever is the number of bore hole and SPT test done at the site, water table is mentioned in the report for each borehole. Also,soil type is clearly  mentioned in the report. If the soil type is fully sandy or sandy and silty type(SM Type) and water table is high, then in this case, soil has a tendency to liquefy when earthquake occurs. 

Even a sound and structurally stable structure is susceptible to failure if soil supporting structure undergoes liquefaction during earthquake. This is one of the biggest challenge for structural engineer. Reading carefully and attentively the geo-technical report and providing suitable foundation or soil improvement is the only solution for this challenge.For solution, it is essential to know what is liquefaction and how does it happens. Without knowing the complete anatomy behind liquefaction,a suitable solution can never be found.

Generally shallow foundation is provided at a depth of 1.5 m to 2.5 m below natural ground level(NGL).If water table is very highy, say  water table level is 1.5 to 2 m below NGL, then soil in this region is fully submerged condition. And if soil in this region is cohesion less i.e fully Sandy or Sandy -Silty type(SM Type) then whole soil in this region will undergo in liquefaction i.e soil will behave like a fluid and will have shearing strength zero. Liquefaction state of soil is analogue to fluid in terms of shearing strength. As fluid has zero shearing strength,hence soil in the state of liquefaction may have some shearing strength or has zero shearing strength depending upon the liquefaction potential of the soil.You can relate this with an example,when you try to put your hand into the bucket  full of  water, you will feel negligible resistance as a shear by water.In the same manner, when soil is liquefied, then it does not respond any shearing resistance  to the force exerted by the footings supported on it.Hence, in this case structure starts settling/sinking during liquefaction.As liquefaction is not uniform below each footing, hence differential settlement occurs and  due to this building may partially or as a whole may  collapse depending on the liquefaction potential of the soil.Although structural elements of building may or may not have damaged during earthquake but excessive sinking may lead to building non functional.Not only building, even a light weight car can sink when it is standing over liquefied soil because soil is not any potion to  support any loads in liquefaction state.

How Liquefaction Occurs:

To take precautionary action before construction on a site having liquefied soil or doing retrofitting of a damaged building over liquefied soil after earthquake, we need to understand the complete anatomy behind the occurrence of liquefaction of soils during earthquake. 

                 Saturated  cohesion less soil(Sandy or Sandy+Silty) is susceptible to liquefaction during earthquake.Soil under foundation and it’s vicinity is under extremely stressed condition. If soil is saturated,there will be pore water pressure which keep soil particles together. But when earthquake occurs, it produces extreme vibration/turbulence/shaking to the soil particles.This extreme vibrations increases the pore water pressure and also soil gets loosely packed  giving a path to water to flow upwards.As we know, there is always a tendency to flow fluid from high pressure to low pressure.As there is low pressure at the ground, hence water will start flowing from below to ground floor.In this case, voids will be created at the displaced water particle position.In the vicinity of these created voids,loosened/loosely packed soil particles  start moving to fill these voids.Due to this, sinking of soil starts taking place.As the soil supporting structure starts sinking, hence structure also starts sinking. This phenomenon happens in such way, it seems structure is supported over fluid which does not have any shearing strength. This sinking can be from cm to meter. As the turbulence/vibration occurs differently in different foundation system, hence it leads differential settlement.Building may tilt excessively or may collapsed depending upon the liquefaction potential of the soil.

Serious notes to keep in mind for Soil prone to liquefaction: 

This blog will motivate structural engineer to study thoroughly key areas of the Geo-technical report such as the soils types, N-values & water table before designing any foundation.Geo-technical consultant may or may not provide you a statement about whether soil is susceptible to  liquefy or not. Knowing the soil types and water table, you have to understand whether soil will liquefy or not.I have noticed one thing, most of the people are only concerned about the safe bearing capacity(SBC).Sometimes, even structural engineer focuses on SBC only without knowing the soil characteristics like type of soil,N-values, soil compactness like loose,medium dense or highly dense. It is surprising to note, a soil having high potential to liquefy  may have satisfactory safe bearing capacity such as 100 KN/m2 or 120 KN/m2. If somebody design isolated foundation with this data then foundation system may collapse during earthquake.

In recent past, i have gone through the foundation design of an industrial shed proposed at Nepal for Steel Melting Shop(SMS) & Rolling Mill. In Geo-technical report, there was SBC mentioned as 120KN/m2 having average N-values as 10 at a depth of 2.0m. But there was a warning in this report highlighted as soil upto a depth of 4.0 m is prone to liquefy. I talked to Geo-technical consultant regarding the same and drew his attention that isolated foundation will not be safe. He re-analysed the soil characteristics and recommended pile foundation for the same. Raft foundation is also an alternate solution for soil prone to liquefy as it some how stops water to come out above the foundation as it blocks all possible path of water to come from below during excessive shaking in earthquake.

 

Thanks

Mohammad Sohel Akhtar(MSA)

(Structural Engineer)



MYTH AMONG LAYMAN,CONTRACTOR & ARCHITECT PREFERRING USING OF HIGHER REINFORCEMENT & LOWER SIZES OF COLUMN & BEAMS IN RCC BUILDINGS.

” This blog is dedicated to all clients, contractors ,architects and layman who think a RCC building can be make structurally sound using more reinforcement and lesser cross section of structural elements”.

Usually i come across various person like clients, contractors, architects and layman who say, can we reduce the size of column and beam by using higher reinforcement. Actually architects always want very light section which do not affect the beauty of the buildings. As per the structural requirement,when a structural engineer provide a big column or beam then architect says, why not we are using column and beams of lesser cross section by providing higher reinforcement. Occasionally, i have also heard an architect requesting for reducing the beam depth by increasing the depth of the slab or reducing the beam depth by increasing the reinforcement or reducing the depth of beam by increasing the width of beam.

This is an absolutely a wrong perception developed by an architect, contractor and layman.As they are not aware of the role of stiffness for deflection,durability and crack control,they are right for what their perception allow in this subject.Actually, a myth has developed in their mind that if higher reinforcement is used, then structural members will have higher strength.

Also, it was very strange when i came across a person who was suggesting me to put more reinforcement in slab. Actually, one of slab was having reinforcement of 8 mm diameter but our client was insisting me to provide 10 mm diameter reinforcement. Although i tried to convince him that using 8 mm diameter reinforcement is sufficient for that slab but he was not convinced. Then i tried to understand, what does he thinks about structure. After a quality discussion with him on the subject of structural analysis, i realized that he has developed a misconception that slab is one of the most important element in a building as everything is kept on slab. This is not the only case. I have also heard the same by few other people. Therefore, i realized that i have to educate more and more people and will have to bring all people out from this disastrous myth.

It pains me a lot and very unfortunate to state that how people misinterpret things on structural stability and strength on their own way.I am not exaggerating if many buildings have collapsed or severely damaged in recent past by taking very slender column considering only gravity loading. It is amazing to see builder proposes random column sizes as 230 x 230 mm,300 x 300 mm or 230 x 350 mm for three to four storey building without knowing the consequences of heavy gravity loading and earthquake loading. If somewhere , any building with these kind of proposed sizes are safe for gravity loading then it is taken granted same in other places too.I don’t know what will happen to these building for earthquake loading when it will exposed to.It is essential to keep in mind,during earthquake,severity of shaking in two building will be felt differently at the same site due to geometrical differences although both buildings have same number of floors. In the same site,a highly irregular building will feel higher intensity of shaking whereas a regular building will feel less intensity of shaking. Hence, column sizes can not be same in the two buildings however column spacing and floors are same.Actually, reason is that,a highly irregular building will have twisting/torsion in earthquake requiring bigger column sizes to counter twisting whereas highly regular and symmetrical building will have column of lesser cross section as it will not have torsion/twisting.Here, i am not going to elaborate the cause of torsion like difference in Center of rigidity(CR) & Centre of mass(CM).Please read other article related to the same for knowledge.

Actually architects,layman or builders in order to find large spaces for parking or hiding /concealing column in the masonry walls for aesthetics purposes or to get more free spaces for bed room /living room , slender columns are proposed ignoring large span.They can go for beam with more cross sectional area for large span than column.They do not know the concept of strong column and weak beam.Also, they do not know the failure mechanism.And of course, how they will know these very general and basic concept if we do not educate them.

And when they construct a building on their one way without consulting a structural engineer then something very unfortunate happens to human lives and economy.Therefore, our responsibility plays a important role to spread awareness and to stop building collapsing even under gravity loading.

I have noticed that layman, architects & builders think in unidirectional way. The way their perception allows. They think gravity loading is the only loading that is most likely to occur on a building ignoring a large part of seismic loading.They think if building seems safe in gravity loading then it looks fine to them.They seem relaxed and fully unaware of earthquake loading.They do not know column is weak for lateral loads(Seismic/Wind) and strong in compression.

As a structural engineer, it is our responsibility to guide and educate them.Although we will not be able to teach whole civil engineering to them but we should deliver a general concepts to stop tragedy in future. We should make them aware that however we should make building safe for gravity loading but at the same time we should not forget the bigger and serious concern of earthquake loading.Instead of creating havoc, fears and confusion to understand the complex mathematical modeling like numerical methods(differential equations) of physical phenomena of earthquake, we should come up with very simple examples to clear basic concepts of earthquake. We should relate the drifting or lateral deflection of the building when subjected to earthquake forces with the best and easiest example with newton first law of motion.As we know, when a car starts moving then passenger sitting in back seat feel backward push due to concept of newton’s first law of motion or law of inertia.In the same manner, when earthquake forces exerts in the building, then due to inertia,building will try to drift in opposite direction to earthquake force. We should tell them, column should be able to take huge lateral loads and it should be much stiffer than beam to follow the rules of strong column and weak beams.Also, in case of double and triple height column,column should have larger cross section or will have to be tied at different level to stop column failing in buckling.We should demonstrate them the simple concept of bucking failure with simple example by pushing two measuring scale. Say,one scale of length 10 cm and another one of 30 cm.If both of them is pushed by hand,undoubtedly scale of longer length will buckled more as compared with smaller one.These demonstration will help them the concept behind using stiffer column.After reading this article they will come out of the box like thinking that slab is most important part of building as everything supports on slab.They will really come out of this disastrous myth. This blog will help them a lot to understand basic concept of structural analysis.This will help them to understand , however building shall be safe for gravity loading but it is mono-maniacally designed for seismic loading.

Thanks

Mohammad Sohel Akhtar(MSA)

(Structural Engineer)



CO-ORDINATION FAILURE AMONG DIFFERENT TEAMS MAY RESULT SEVERE IMPACT ON FUNCTIONALITY ,STRENGTH & COST OF A BUILDING

“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.



Thanks

Mohammad Sohel Akhtar(MSA)

(Structural Engineer)



SEVERE CONSEQUENCE OF PROPOSAL OF POINT LOAD ON SLAB OF EXISTING BUILDING

“Feel the structure” MSA

“This blog will acts as a precautionary tool for any structural engineer to allow customer/client to put any heavy point load on existing slab of structure or not “

Precaution is better than cure.

This blog will guide you whether you will permit additional point load on any building on which that much load was not considered during design. There are two vital points that will be discussed here.

One is failure due to punching due to gravity loading and second one is failure occurred due to change in mode of vibration of building during earthquake

1. PUNCHING FAILURE:         

  AS per  clause -24.3.2.1 of  Indian standard, IS:456-2000 (Indian Standard code for plain and reinforced concrete – code of practice, edition-2000), existing slab is not able to respond huge  punching stress subjected by a point load of 1 ton or more which was earlier not considered in design.This happens due to inadequate thickness of slab. Actually during design of slab, that much unexpected point load was not supposed to occur throughout it’s design life & when unexpected heavy point load is put on slab, failure takes place. This kind  of punching failure is brittle in nature and slab will fail without any alarm. Generally,dead load and imposed live load is applied as KN/m2 or Ton/m2 unless & until any provision of equipment or pointed object is there on slab.

      Another reason for not permitting any point/concentrated load on existing slab at slab level   is that concrete lose its strength  when it becomes old due to its exposure to environment having deleterious chemicals which corrodes reinforcement.

                 Secondly, any building adjust on its own  by prolonged creep and shrinkage action  when structural members are subjected with load  after few days or month of construction . But suddenly when building is subjected to huge load, it undergoes huge deformation exceeding limit limiting values of deformation.

2.   CHANGE IN BEHAVIOR/FAILURE MECHANISM DURING EARTHQUAKE:       

  As per clause 7.3.1 of Indian standard  IS:1893-2016(Part-1 for Criteria for earthquake resistant design of structure) , lump mass at floor level shall be dead load + some percentage of live load. Here in this case proposal of heavy point load at any floor will increase dead load. Consequently, lump mass will increase significantly. This will result in attracting  more earthquake forces as earthquake forces   are inertial forces. Also, greater super dead load at  floor result in deviation in center of mass (C.M) & center  of rigidity(C.R) .This will create torsion in building during earthquake. As it is well- known fact, column are very weak in torsion/twisting. Hence, columns are most likely to fail during earthquake as provision of torsion/twisting resistance system may have not considered in design.

                   Also, as  per clause 7.1, table-6  of Indian standard  IS:1893-2016(Part-1) , putting heavier load to upper floor will create soft storey  at lower and upper floor and will distort failure mechanism in building. This kind of soft storey will change the mode shapes of vibration of  building resulting in failure of column at soft storey level.


Thanks

Mohammad Sohel Akhtar(MSA)

(Structural Engineer)



                 

HOW TO MAKE CAREER IN STRUCTURAL ENGINEERING

“Feel the structure” MSA

Note: This Blog is for those civil engineers who want to make career in Structural Designing of buildings

This is a high time to share with you a very vital information for a beautiful career in structural engineering. Essentially you need to be civil engineer. If you are M.Tech in structural engineering, then it is more preferable.However, it’s not a strict criteria to enter in the field of structural engineering and designing. You can Enter in this field with bachelor degree as well.

If you are very keen to work in this challenging field, then you need to know the inside story of structural engineer working in this field. Here i am going to tell you the entire procedure involved in the analysis, designing , co-ordination and issuing drawing to sites. If you know all these steps in advance, the it will be very easy for you to establish in this field.

Before writing steps involved from conceptual level to construction stage, you need to understand the team involved for the finalization good for construction drawings.

Following teams involved in the finalization of drawings at office & issuing it to site:

  1. Architects
  2. Structural Engineers
  3. Structural draughtsman
  4. MEP (Mechanical, Electrical & Plumbing Engineers)

STEPS INVOLVED:

STEP: 1Surveying

After receiving work order from a client, architect co-ordinate with a surveying agency to make contour plan for deciding buildings plinth level and site development and this contour plan is very essential to know the site condition whether it is above the existing road level or below the road level. Structural engineers substantially use reduced level mentioned in the contour plan to filling load if filling is required to achieve desired plinth level. Also, ramp and road are made based on this contour plan.

STEP: 2Geo technical Investigation

Architect after receiving contour plan,they start planning building on it. They show road development and fit all building on this survey with orientation & based on this, master plan is made.

After putting all building desired by client, architect pass on this site plan having all blocks to the structural team to locate bore hole for soil investigation for foundation design. Structural engineer mar bore hole as BH-1, BH-2, Bh-3 & so on the site plan and issue it the Geo- technical investigation agency with certain specification to find out safe bearing capacity(for open foundation),pile load capacity if there is recommendation of pile & modulous of sub grade reaction if there is a recommendation of raft.

Note: No Geo technical report is assumed to be final until & unless it is approved by a structural engineer. A structural engineer thoroughly review the soil report. Structural engineer guides Geo technical engineer to provided additional data if needed giving a concrete reason. For example, if there is recommendation for pile foundation of 600 mm diameter, then it is our responsibility to ask Geo technical engineer to provide recommendation for 450 mm & 300 mm diameter pile as well for the small buildings. Also, in report, Geo technical engineer shall be reminded to provide recommendation sheet for isolated footing because for extremely small structures like guard room, porta cabins & boundary walls,this data will be useful. Also,in some Geo technical report,there may be only one recommendation of isolated footing but we should ask for the recommendation for sub grade reaction as in the same site , there may a provision of under ground tank or in some places most of individual footings for separate column may over lap each others, hence recommendation for sub grade modulus is essential for designing raft.

STEP: 3Preliminary Framing & Column Placement

Once site plan is finalized, column is placed with different orientation in each building blocks and based on column placement, tentative framing is made. This framing with column is shared to the architectural team to get their approval as per the functionality of building. Also, tentative beam depth is shown in the drawing. Based on this, architect may change floor to floor height of the building if excessive depth of beam is required for the desired span. Apart from this,Architect coordinate with MEP team for the cut outs for plumbing & fire fighting work. Also, there may AC duct running inside the false ceiling. Based on these criteria, Architect finalize the floor to floor height.Once tentative framing is approved, architect again issue separate drawings to structural engineer of each building blocks with column matching with structural framing and all sections and elevation & after that preparation of tender or DPR(Detail Project Report) starts.

STEP: 4- PREPARATION OF TENDER DRAWINGS & SPECIFICATIONS

After approval of preliminary /conceptual drawings, tender drawings are made. For that,a structural engineer needs to start modeling & analyzing building in softwares like STAAD Pro, Etabs etc. Once analysis & designing is over,structural engineer gives final column sizes & beams to the structural draughtsman.Also,whatever type of foundation is mentioned in the approved soil report, structural engineer provide foundation and that is drafted by draughtsman.

Complete set of drawings having column marking plan, column schedule, foundation plans & sections,floor wise all framing plans having beams sizes and slab thickness, desired section in sunken,cantilever in framing along with staircase sections having waist slab thickness, landing beam sizes and if there is over & under ground tank , its detail shall be provided with section sizes.

Ins short, section sizes of all structural elements are required for quantity take off in making BOQ.

Also, specification for grade of concrete(Like M20,M25,M30…etc), grade of reinforcement(Like Fe500, Fe550 …etc.),grade of cement,type of cement(Like OPC, PPC or sulphate resisting cement) , type of sand, type water proofing materials & type of bricks /blocks shall be provided by structural engineer to the estimator to consider these specs in bill of quantity(BOQ).

STEP: 5-PREPARATION OF GOOD FOR CONSTRUCTION DRAWINGS(GFC)

After getting approval of tender drawings from department/client, department/client call contractor for bidding & this process take considerable time. Meanwhile, as a structural engineer, our main focus is to work on good for construction drawings. If there are some minor correction like missing dimensions, missing sections then these shall be resolved in the GFC drawings. Also, detailed reinforcement in beam as beam elevations and slab as reinforcement layout is made for construction. Also, if there is any instructions from department/client for drawing to be vetted from government institute or individual consultancy firm, then detail calculation report termed as DBR(design basis report) shall be made along with STAAD/ETABS file. These consolidated DBR & STAAD/ETABS file shall be submitted to vetting authority and time to time they shall be chase to get all submitted drawings approved so that there will not be any delay in construction.

Thanks

Mohammad Sohel Akhtar(MSA)

(Structural Engineer)

THINGS TO KEEP IN MIND FOR STRUCTURAL ANALYSIS & DESIGNING OF BUILDING

“Feel the structure” MSA

Hello! Structural Engineering Fraternity

       I am a Structural Engineer. My main work frame is to analyse & design simple to complex structure. I encourage many young civil engineers who have just passed out  from college and want to make a career in Structural Engineering.Also, my blogs will work as a tonic to some civil engineers who are already in this field but feeling very low due to lack of knowledge and skills. My blogs are certainly going to bring not only their professional growth but also they will start loving this challenging field.It will indulge them to be more innovative.

        I believe in 4’S&DE.

        S= Stability, S= Strength, S=Stiffness, S=Sustainability, D= Durability & E= Economy

         4’S&DE is my basic principle of analysing and designing any structure and same shall be followed by any Structural Engineers.I have seen many engineers who sometime think, if a structure is having sufficient strength against shear, moment and torsion instead of lacking in stiffness and durability, it looks fine to them. But i want to clarify one vital point, without having proper knowledge of deflection check(Based on Stiffness),Durability Check(Based on proper grade of material selection, life time exposure of structure to environment) and Economy (Based on client’s budget) no Structural Engineer is going to be very successful in their field.

         My friends, if you want to make a career as a RCC Designer, then it is very important for you to understand deeply about concrete technology. Until & unless ,you are able to understand the chemical reaction tacking place in concrete and adherence it’s hydration product to different deleterious gases and chemicals in the environment,you will not be able to judge which materials like  PPC or OPC or sulphate resisting cement is most suitable as far as durability is concern.You will be astonished by knowing the fact,sulphate reacts with the C-H-S gel(hydration product of cement) and concrete gets expanded by 300% by volume. You can feel now to what extent it can damage concrete by developing cracks and it further give path to ingress other deleterious chemicals like chloride to reach reinforcement. Also we should have knowledge about high performance concrete like high flow concrete & self compacting concrete where there is a congestion of reinforcement to avoid honey combing.

        And last one is economy. It requires rigorous analysis or you can say this is the most tedious part. In order to design building under the specified budget, we require lot of  reiteration process giving optimum member size fulfilling 4’SD.

         My main area of blog writing is to cover  4’SDE. Time to time, i will share excel sheets that will help not only freshers but also practising engineers.Also, i will regularly update you with some hand calculation for the analysis and designing of  simple frame and structural elements to bring you all to the basic. Please keep in mind, in fast pace of working environment, we are forgetting our basics and it is becoming very disastrous for all of us.Above all,i believe in sharing of knowledge and skills.What is the use if somebody is having huge knowledge and skills & carrying all these  to grave. I think,noting at all. I have realised this now and understood the importance of sharing. So, hope somebody will get benefit from my sharing. Also believe, even if a single person is able to uplift his/her career,then my blog writing will be successful.

       Most importantly, even a practising structural engineers will find something very new and innovative in my blog.

        Last but not the least, i will request you all who reads my blog to give their valuable observations/suggestions to improve it’s content.


Thanks

Mohammad Sohel Akhtar(MSA)

(Structural Engineer)