Subscribe to My You tube channel

Foundation of structures

By -

 Foundations are an essential part of any structure. Structures will not be able to withstand imposed loads, and it will fail in case of using the wrong foundation type or foundation with a smaller size. Determining the type of foundations will be based on a soil investigation study. Soil investigation will determine the soil bearing capacity and the other characteristics of the soil. Loads transferred from the structure is playing an important role in determining the type and size of foundations. For small structures, shallow foundations will be sufficient to transfer the load to the soil. On the other hand, huge structures required deep foundations to transfer the loads to the soil without causing large settlement or structure failure. 


Figure 1


The method of construction and the mechanism of distributing the loads are different in shallow and deep foundations. Shallow foundations are composed mainly of footing. The shape of the footing can vary. It can be the square, rectangular, or trapezoidal. The constructing of footing is simple. The process of constructing a footing will begin by preparing the existing soil to the required level, then, blinding concrete is casted, and the reinforcement and shutters are installed. Finally, the concrete will be casted. The constructing of a deep foundation is more complicated. Cast-in-situ piles, driven piles are examples of deep foundations. The constructing of in-situ cast piles required special equipment such as drilling rig, cranes, and Vibro hammer. The constructing of cast-in-situ piles will consist of the following stages: punching of the casing, drilling of the pile, lowering of steel cage, then pouring of concrete and removal of the temporary casing. 
Figure 2



Driven piles can be steel piles such as H-beam. Also, it can be precast piles. The constructing of driven piles is significantly different from cast-in-situ piles. Driving piles will require a driving hammer. The driving hammer will drive the pile to the required depth and the correct location. The size of the hammer can vary according to pile size and the required depth of driving. 

Figure 3

Shallow foundations will directly transfer the loads from the structure to soil. The load will be distributed by the direct contact between the bottom of the footing and soil. The increase of footing dimensions will reduce the pressure and increase the bearing capacity of footing. The pressure distribution under the footing will vary according to soil type, as shown in figure no:4. 

Figure 4

Deep foundations will carry loads of structures by two mechanisms. Friction and end bearing are the mechanisms of transferring the loads from piles to the soil. The friction between the pile's outer surface and the soil will resist the settlements of piles foundation and resist the loads transferred from the structures. Another mechanism is end bearing. If the rock layer is not deep, the pile can be extended to the rock layer. In this mechanism, the loads will be transferred to the rock layer from the pile. 

Figure 5







Comments

Post a Comment

Popular posts from this blog

Bar Bending schedule (BBS)

By -
Image
 The bar  bending schedule is a table that contains the details of reinforcement for a specific structural member such as footing, column, slab, and others. The bar bending schedule will contain the bars' dimensions to be used, the shape of the bars, the size of bars, bar mark, number of bars, and the weight of bars. BBS will be used to determine the weight of reinforcement required for a specific structural member.  there are various advantages of bar bending schedule such as: estimating the quantity of reinforcement for each structural member. So we can estimate the amount of reinforcement required for a construction project.  BBS will help in reducing the losses of steel by procuring the precise quantity of different rebar diameter.  BBS will reduce the wastage of reinforcement by providing the engineers with the exact dimension and shape of rebars. Knowing the exact dimension and shape will reduce the time of cutting and bending rebars.  BBS will reduce the effort at the time o
Read more

Binding wire for steel reinforcement

By -
Image
  Binding wires are used to tie steel bars together. These wires are playing a significant role in maintaining the reinforcement stability and rigidity. Wires are used to tie the steel bars at intersections points. By tying the steel bars together, we ensure that the steel bars will not move from their locations during construction or during the time of concreting. In slabs, binding wires are used to tie longitudinal and transverse bars together. In columns, it is used to tie vertical bars with stirrups.   Figure 1 There are various types of binding wires such as  Black annealed baling wire, Stainless Steel Binding Wire, and PVC coated binding wires.  Black annealed baling wire used to tie black steel. The popular size for black wire ranges from 16 to 22 gauges. Stainless steel binding wires are used to bind stainless steel reinforcement. Stainless steel reinforcement is used in a harsh environment where the black steel gets rusted quickly. Therefore, stainless steel reinforcement is u
Read more

Pile cap

By -
Image
Pile cap used to transfer the loads from superstructure to the piling. The pile cap is thick concrete mat rests on piles. It is part of the foundation and used to distribute the loads over the piles. Piles used when the soil bearing is not enough to carry loads of the structure. Figure 1  construction management: concrete construction bridge construction:How to become a bridge engineer Pile cap construction procedure Excavation around piles: After 7 days of the casting of the pile the concrete will gain approximately, 70% of it is compressive strength. The soil around piles will be removed to the required levels and dimension that allows construction of the pile cap. A step shall be made if the excavation is more than 1.5 m to prevent soil collapse. Figure 2 Pile head cutting: Concrete will be removed up to cut off level. If concrete under the cut off level is unsound. It shall be removed, and the pile will be repaired. Pi
Read more

Repairing of concrete bulging

By -
Image
Improper designing and installation of formwork for a concrete member can result in concrete Bulging. During the placing and compacting of concrete, forms may deflect largely in the weak areas. The deflection of forms will cause concrete to expand at this location, and this known as concrete Bulging. Concrete Bulging will spoil the appearance of a concrete member. Therefore we should always ensure that the forms are appropriately installed, and it is sufficiently supported to resist the concrete during placing and compacting. Bulging should be repaired in case we couldn't avoid it. The solution of concrete Bulging, offset, or surface irregularities are surface grinding. However, excessive surface grinding can weaken the concrete.  Figure 1 If the bulging or surface irregularities are small, grinding of concrete surface will be sufficient to remove surface irregularities. If the Bulging of concrete is significant, then the concrete should be chipped, and the surface
Read more

stress-strain diagram for aluminium alloy and rubber

By -
Image
figure no:1 showing the stress-strain diagram for aluminum alloy. we can notice from the stress-stress diagram that aluminum has a considerable ductility. despite the absence of explicit yield point as in structural steel . the initial portion of the stress-strain curve is linear with a recognizable proportional limit. the proportional limit for aluminum alloy ranges from 70 to 410 Mpa (10 to 60 Ksi). aluminum alloy undergoes large strain before failure. ultimate stress ranges from 140 to 550 Mpa (20 to 80 Ksi). construction management: concrete construction bridge construction:How to become a bridge engineer Figure-1 Yield stress for aluminum alloy can be determined by drawing offset line parrel to the linear portion of the stress-strain curve. the straight line offset by a standard strain such as 0.002. the intersection point with the stress-strain curve is the point of yield stress. figure no:2 illustrates the concept of offset method. yield stress acquire
Read more

Non-working piles

By -
Image
Non-working piles are executed at the beginning of the project to study the soil reaction and the maximum settlement for the non-working piles. The pile will be loaded to twice of working loads. According to the test result, the pile length will be changed. If the settlement exceeds the maximum settlement then the pile length will be increased. construction management: concrete construction bridge construction:How to become a bridge engineer Test of non-working piles Static compression load test gives an indication about the pile's reaction to the load. The settlement of non-working piles will be measured for different load increment. From this information, the design length of the pile will be decided. Maximum load for pile will be working load multiplied by 2 (working load*2) or as per local standards. The following steps explain the procedure of the test.  A. The steel cage will be prepared as per the approved shop drawing before, but the spira
Read more

Bridge Diaphragm

By -
Image
The main function of diaphragms is to provide a stiffening effect to deck slab in case bridge webs are not situated directly on top of bearings. Therefore, diaphragms may not be necessary in case bridge bearings are placed directly under the webs because loads in bridge decks can be directly transferred to the bearings.On the other hand, diaphragms also help to improve the load-sharing characteristics of bridges. Diaphragms also contribute to the provision of torsional restraint to the bridge deck. Diaphragm will be used also to resist stresses that occurs during the post-tensioning process. Post-tensioning hardware are casted inside the diaphragm. Figure 1 construction management: concrete construction bridge construction:How to become a bridge engineer Types of diaphragm: Diaphragm at the span end: this type of diaphragms will be located between two bridge spans or at the bridge abutments. Expansion joints will be used to connect bridge spans. This
Read more

Nominal maximum size of coarse aggregate

By -
Image
Concrete is a widely used material. Reinforced concrete structures can be found everywhere. The main reason behind the popularity of reinforced concrete structure is the high strength and the long life span of these structures. Concrete and steel are combined to produce reinforced concrete. Concrete is good at compression while steel good at tension. Concrete and steel form a perfect combination to resist loads imposed on the structure. Concrete is a composite material composed of cement, coarse aggregate, fine aggregate, and water. Admixtures can be used to enhance concrete properties. A concrete mix consists of almost 65% aggregates. Aggregates are classified into fine and coarse aggregates. Since the aggregates form the majority of a concrete mix. The quality of aggregates can greatly affect the strength and durability of concrete. Aggregates can be natural or crushed aggregates. Used aggregates should be strong, hard, and should not contain a large amount of organic matter or harmf
Read more

shear key

By -
Image
The purpose of the shear key is to improve the bonding between concrete surfaces. The shear key is usually made at the construction joint location to enhance the adhesion between the old and new casted concrete. Construction joint is considered a weak point because the concrete is not casted at one time, in large structures where the concrete can not be casted for some members at one time, such as a slab. We usually divide the slab and cast it at many stages. The large quantities of concrete will make it impossible to cast the slab at one time. Therefore, the casting will be done in several stages. The location of the construction joint should be selected carefully. Construction joint shall be made at the location of minimum shear and moment.  The bonding between old and new concrete can be improved by roughening the old concrete and forming a shear key on the concrete surface while the concrete is still plastic. The shear key can be formed by pressing timber into the concrete surface
Read more

The reasons behind the trimming of pile head

By -
Image
In general, the bored piles are casted to a level higher than the required pile cut-off level. Pile cut-off level is usually similar or a little bit higher than the blinding level of a pile cap. the process of constructing a cast-in-situ pile involves the following steps: installation of the temporary casing to prevent the soil collapse during the drilling process and to guide the drilling rig. Drilling the pile to the required level and diameter. Installation of a reinforcement cage. Reinforcement cage vertical bars will be extended above the pile cut-off level to improve the bonding with the pile cap. The casting of concrete usually done with a tremie pipe. Tremie pipe will be lowered to the bottom of the pile, and then the concrete will be poured. Once the casting is completed, the temporary casing will be removed. It is a common practice to cast the concrete above the cut-off level. the concrete casted then removed for the following reasons: during the casting pro
Read more
My photo
Mohammad
My name is Mohammad Hamdan, and I am a Civil/bridge Engineer with extensive professional background and experience in the field of construction. I have 10+ years of experience in the construction field. During my professional career, my emphasis has been placed on structural projects, mainly bridges, infrastructure and roads. Reading and practicing the design of structures is my passion.i was lucky to be a part of a big team that executed major highway interchanges. I believe in spreading the knowledge, thus, i compose these courses to share my experience and knowledge. My course focuses on the practical side of construction field. On other word, i am sharing some of what new engineers need to know about construction field. Beside working on construction field, i love writing some articles on my website ( curious civil engineer) Moreover, i wrote some engineering papers, you can check them  by searching my name on Google (Mohammad mamon Hamdan)