Civil Engineering Blog

State Bank of Pakistan Recruitment of Professional Engineers. SBP Banking Services Corporation (SBP BSC) was established in 2001 as a wholly owned subsidiary of State Bank of Pakistan. As an operational arm of State Bank, SBP BSC operates through a network of 16 Field Offices across the country having its Head Office at Karachi. For further details, please visit our website www.sbp.org.pk/sbp_bsc. In order to further strengthen its Engineering Department, SBP BSC invites applications from talented Pakistani/AJK nationals possessing requisite qualification and experience for the following positions. 

Qualification : Bachelors degree (BE/BS/B.Sc) in the relevant discipline from HEC recognized university with a valid Pakistan Engineering Council (PEC) registration. Additional Qualification i.e. Masters degree in the relevant field will be an added advantage. In case the degree is obtained from a foreign university, the short-listed candidates shall be required to submit the equivalence certificate from Higher Education Comission (HEC) at the time of interview. 

Age : Maximum 45 years as on last date of submission of application to SBP BSC. Age limit shall be relaxed by 03 years of candidates from FATA. Northern Areas / Gilgit Baltistan. Balochistan and Azad Kashmir, Employees of SBP and its subsidiaries, possessing requisite qualification and experience are eligible to apply without upper age limit. 

The candidate must have a minimum of 18 years of relevant post-qualification experience with supervisory capabilities and demonstrated / verifiable track record of smoothly running respective engineering related function in dynamic and comparable public/private sector organizations. The candidate must also have experience of managing construction of at least one building project worth more than Rs. 100 million. Preparation and reviewing of tender / bidding documents with respect to PPRA guidelines will be an added advantage. Candidate having building work experience will be preferred. 

Bachelors Degree (BE/BS/B.Sc.) in the relevant discipline from HEC recognized university / institute having minimum 60 % marks and a valid Pakistan engineering council (PEC) registration. Additional qualification i.e. Master degree in the relevant field will be an added advantage. In case the degree is obtained from a foreign university short listed candidates shall be required to submit the equivalence certificate from Higher Education Comission (HEC) at the time of interview. 

Maximum 30 years as on the last date of submission of applications to SBP BSC. Age limit shall be relaxed by 03 years for candidates from FATA, and other areas. Employees of SBP and its subsidiaries, possessing requisite qualification and experience are eligible to apply without upper age limit. 

The candidate must have a minimum one year of relevant post-qualification experience in building projects in renowned public / private sector organizations. Preparation and analyzing of tender / bidding documents with respect to PPRA guidelines will be an added advantage. 

If you are a fresh or experienced civil engineer living in Pakistan and seeking Civil Engineering Job in Building Sector than don’t post or share your CV here as we are not a part of the department and we are just sharing it so that you can get the opportunity to apply for this job.

If you are a fresh or experienced civil engineer living in Pakistan and seeking Civil Engineering Job in Power Sector than don’t post or share your CV here as we are not a part of the department and we are just sharing it so that you can get the opportunity to apply for this job.

If you are a fresh or experienced civil engineer living in Pakistan and seeking Civil Engineering Job in Building Sector than don’t post or share your CV here as we are not a part of the department and we are just sharing it so that you can get the opportunity to apply for this job.

If you are a fresh or experienced civil engineer living in Pakistan and seeking Civil Engineering Job in Building Sector than don’t post or share your CV here as we are not a part of the department and we are just sharing it so that you can get the opportunity to apply for this job.

What would you do if you enter in a building and saw some cracks in a beautiful pattern like that of an ECG of human heart? Obviously you will start running out of that building. But what if the designer of that building gives you a surety that he has checked all the structural requirements and the design as well as the building is safe even after those beautiful cracks? Obviously again you will not stop your run hell out of that scary building.



So from above we can conclude that the building was designed and meant to accommodate humans, but as human brain has built-in functions to save the life and avoid death / injury as much as possible, therefore this building does not serve its purpose as it is scary and have a chilling effect in it. After said that we can now understand the actual meaning of serviceability of a building, in general and of a concrete structure, in particular.

Similarly bending in beams or buckling in columns is also a serviceability criterion that must be kept minimum or within the required ranges as per the code generally used within the locality.
As a student of Structural engineering you might already know about two different methodologies for designing a structure generally. Let me remind you in short, these two methods are named as :-

1) Allowable Stress Design Method
2) Ultimate Strength Design Method

In Allowable Stress Design procedure, for any particular type of material used for structure; like timber, concrete, steel an allowable stress range is decided and provided by the code. The designer is bound to keep the internal as well as external stresses within those limits. Concrete Structures in Allowable Stress Design procedure is never allowed to have even small cracking on its surface.

But the above method of design has some limitations; a Major one of those is larger cross-sections and excessive reinforcement. But this was adopted in the past as the knowledge about different materials of construction was limited as well as not that exact and trustful. However, with advancement in material engineering, the material engineer started believing in their knowledge and in the strength of the construction materials.

Ultimate strength design procedure utilizes the fullest of the available strength of materials i.e. allowing the steel to get yielded up to certain extent and even consider a minimum cracks of certain width not a safety hazard for the occupants.

So after the above discussion we can conclude :

1) A concrete structure is expected and is somehow healthy to be of a cracked section, but only within certain limits and ranges.
2) The crack within the concrete member needed to be within a limit so as to fulfill the serviceability criterion of the code.

One other reason to keep the crack within limit, beside serviceability, is sustainability is now explained. A Reinforced Cement Concrete Beam having a mesh of steel reinforcement cannot sustain its complete compressive as well as tensile strength if the moisture can get penetrated to the embedded steel rebars through the allowed cracks.

Due to that reason, the ductility, capacity, energy absoption, stiffness  and structural performance of the concrete demands the designer to keep the width of the crack minimum and within a control.
The width of the crack can be assumed to depend on following :

1) Nature of the reinforcing steel
2) Spacing of the flexural steel reinforcement
3) Nature of bond between steel bar and that of tension zone of concrete.

Now let me explain to you that why actually we want the concrete to get crack a bit? 

A general answer is actually already provided above, however, we can discuss that in detail here from strength of materials point of view. We know from strength of materials that concrete is strong in compression and weak in tension with tensile strength only a fraction of compressive strength of concrete.

If we consider a beam with modulus of rupture in such a range that at modulus of rupture the stress in concrete is around 500 psi, then the stress within steel according of modular ratio relation would be 500 x 8 (assuming a general value of modular ratio of 8) = 4500 psi or 4.5 ksi whereas the yield strength of the steel reinforcement is around 40 to 75 ksi ( It is important here to know that Grade of steel recorded in the drawings or in the specifications of a project is actually the yield strength of the steel reinforcement bars in thousands of Psi like Grade 60 steel would mean fy = 60,000 psi).

For those who don’t know Modular ratio for reinforcement and concrete is the ratio of modulus of elasticity of steel rebar with that of modulus of elasticity of Concrete i.e. n=Es / Ec.

As for beam considered above the stress in steel reinforcement is way below the yield strength of the steel rebar therefore providing reinforcement in the steel is of no use in such a case.


Now in the next coming paragraphs we will try to talk about the equations that is usually used to calculate the width of crack in a concrete member. Two common equations that have found applications in the ACI code are :-

1) Gergely and Lutz equation (z-factor method)
2) Frosh Equation

The above mentioned equations utilizes the conclusions and findings from series of tests and experiments.

Gergely and Lutz Equation

Gergely and Lutz used test results from Hognestad, Kaar and Mattock, Kaar and Hognestad, Clark and Rush and Rehm to conclude their equation for the calculation of crack widths at the tension surface.

The Original equation developed by Gergely and Lutz is as follows :-




Where Ws is the maximum crack width at level of steel reinforcement in mm
fs = the stress in the steel reinforcement in N/mm^2

Ao = Area of concrete surrounding each bar. This is measures by dividing total effective concrete tension area surrounding reinforcement having identical centroid by total number of bars (mm^2)



To obtain the maximum crack width(Wm) at extreme tensioned fiber the above equation is multiplied by a factor β.

 Frosh Equation

According to Frosh , the maximum concrete cover, c used in the test analyzed by Gergely and Lutz was 84 mm and only three specimens of their test group among 612 observations had clear covers greater than 64 mm.




According to Frosh their equation is valid for a relatively narrow range of concrete covers (i.e. upto 63 mm). The use of thicker concrete covers is increasing because research and experience have indicated that the use of thicker covers can increase durability. Therefore, Frosh developed the following simple, theoretically-derived equation to predict crack widths that could be used regardless the actual concrete cover.

ACI Code Provision 

According to ACI 318-95, the flexural crack control requirements must be in accordance with z-factor method developed by Gergely and Lutz. Following the extensive statistical analysis techniques on experimental data from several researchers. The equation used is as follows :-



The factors involved in the above equation to use the crack width is already explained above.

Ultra-high performance Fiber Reinforced Concrete is a relatively new construction material having minimum coarse aggregate (usually size greater than 6-7 mm is not used) having discrete random steel fibers uniformly distributed across the concrete matrix with the basic strength of above 14,000 psi (100 MPa) in 3 or 4 days that can go upto as high as 25,000 psi at 28 days ultimate cure. 

Concrete is among the widely used construction material due to some of its high-five benefits including easily availability of raw materials, easy casting and so on. But along with those mouthwatering delicious advantages there are some drawbacks and shortcomings rendering a reason for most skyscrapers to be of steel structure.

Being said that, still the material engineers, civil engineers and scientists are trying to uplift and enhance the properties lied within the matrix of concrete mass. Among those efforts one listed attempt is introduction of randomly oriented uniformly distributed discrete sort of fibers of any material including glass, geo-synthetics and steel. 

The idea for steel fibers in fiber reinforced concrete is not a new one; after finding the health-risks associated with asbestos fiber reinforced concrete, the steel fiber finds its way around 1960s. 

The properties of concrete like freez-thaw, ductility, toughness, shrinkage, impact, abrasion, permeability, bleeding, pumpability, spalling and so on, each of such properties can be improved and enhanced in an appreciable manner with the introduction to fibers and specially steel fibers in the concrete. 

Conventional concrete is liable to cracking from the day first of its service due to its plasticity and due to drying after hydration causing shrinkage and producing hair like thin cracks. Conventional unreinforced concrete is well known to be strong in compression with only 10 to 15% tensile strength as compared to that of compressive strength. 

Due to its small flexural resistance a newly casted beam of concrete is liable to crack from the center due to maximum moment and this is the reason for considering reduced cross-sectional area of the beam in design practices as per design codes. 

One more bad behaving of the concrete is recorded as “brittle in nature”, which is the most hazardous and precarious behavior of a structure from serviceability and safety point of view. 

All of aforesaid drawbacks can be minimized and up to some extent eliminated by the use of Steel Fiber reinforced concrete. 

A significant commercial application of Steel Fiber reinforced concrete can be witnessed in Al McGuire Center a 3700 seat arena in Milwaukee, Wisconsin at Marquette University, America where a Opus North, a design / build construction firm have used 46 pounds of Steel fibers in the concrete to make it no-joint, no-crack floor. 

Steel fibers can:

• Improve structural strength

• Reduce steel reinforcement requirements

• Reduce crack widths and control the crack widths tightly, thus improving durability

• Improve impact– and abrasion–resistance

• Improve freeze-thaw resistance

You cannot degrade the enhancements and augmentations this steel fiber can put-in to the conventional concrete properties. In specific circumstances, steel fiber can completely eliminate the need of steel reinforcement bar (rebar) in reinforced concrete.  There are many projects having industrial flooring made of only steel fiber reinforced concrete without any steel deformed rebars similarly there are many tunneling projects using precast lining segments reinforced only with steel fibers. 

Beside all other benefits and paybacks the steel fibers made in the conventional concrete; the crack-minimizing behavior of steel fiber reinforced concrete (SFRC) is the winner of all from the eyes of the industrialists and construction experts.

Through the numerous experimental studies, it turns out that the addition of steel fibers can improve the structural capability of concrete. Even though SFRC has many advantages as structural material, some limitations still exist in the construction of the large-scale structures that requires very high compressive and tensile strength.

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is self-leveling concrete that can flows for hours, It is a very expansive construction concrete that is usually batched in very small quantities.  From physical seeing UHPFRC is similar to the conventional concrete with only difference that it does not have coarse aggregate. 

UHPFRC has gained enough popularity in recent times in Europe, North American, Australia, Far East and especially Japan. 

The Museum of European and Mediterranean Civilizations (MUCEM) constitutes an outstanding realization due to the systematic structural and decorative use of UHPFRC. The MUCEM, in hosting the venue of UHPFRC 2013 symposium, has appeared as a symbol of worldwide engineering community, technical breakthrough and creativity.

Although a lot of research and modifications to the already available methods of design for structures need to be revised or studied in depth regarding the ultra-high performance fiber reinforced concrete. 

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