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Structural design of road pavement

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The secret to building efficient, durable roads isn’t just in the materials—it starts with understanding traffic . Traffic analysis equips engineers with the critical data needed to make smart decisions on road width, pavement thickness, and structural design . In flexible pavement design, the process begins with comprehensive traffic analysis —starting from traffic volume surveys to detailed axle load studies. Each step ensures that the pavement is built to handle today’s demands and tomorrow’s growth, maximizing safety, durability, and cost efficiency . Ready to dive deeper into the science behind long-lasting roads? 📌 Watch the full course here  
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prestressing equipment

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Jacks are essential tools in prestressing operations and are used to apply tension to strands within tendons. There are two main types of jacks: A. Mono-Strand Jack A mono-strand jack is primarily used in building construction, where tendons typically consist of a small number of strands (usually 3 to 4). This type of jack is designed to stress each strand individually, ensuring precise control over the tensioning process. Since buildings generally have shorter tendons compared to bridges, stressing strands one by one is a practical and efficient approach in this context. construction management: concrete construction bridge construction:How to become a bridge engineer B. Multi strands jack:  In bridge construction, where tendons contain a significantly larger number of strands, using a mono-strand jack would be impractical. Stressing strands one by one in such cases would not only be time-consuming but also increase the risk of strand entrapment. Ther...
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Impact of Hot Weather on Concrete and Necessary Precautions

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Concrete placement should not be permitted if the ambient temperature exceeds 38°C to 40°C . hence, it is recommended to place concrete when temperature is less than 35°C . If the temperature reaches 35°C or more, special precautions must be taken, as hot weather accelerates water evaporation from the concrete. This rapid evaporation negatively affects the hydration process, leading to reduced concrete strength and durability. Adverse Effects of Hot Weather on Concrete Increased Shrinkage – high temperatures cause excessive moisture loss, leading to greater shrinkage in concrete. Higher Risk of Cracking – Rapid drying can induce thermal and plastic shrinkage cracks. Reduced Durability – Increased evaporation increase concrete porosity, compromising its long-term strength and resistance to environmental factors. construction management: concrete construction bridge construction:How to become a bridge engineer Special Measures to Mitigate Hot Weather Effects To minimize ...
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Hardware for post-tensioning

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1. Anchorage Anchorage is a device used to secure prestressing steel and is installed at the edge of a concrete member or the prestressing end. There are two main types of anchorage: Dead-end anchorage : Embedded within the concrete, providing a fixed termination point for the prestressing tendons. Live-end anchorage : Positioned at the edge of the concrete member, where prestressing occurs. The jacking operation is done at the live end anchorage and the applied load is transferred to concrete members after the completion of tendon jacking. construction management: concrete construction bridge construction:How to become a bridge engineer Anchorage device consists of: anchorage device A. Bearing plate :  Typically round or rectangular, its primary function is to transfer the prestressing force from the tendons to the concrete. bearing plate and wedging plate B. Wedging plate:  This component holds the stra...
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Pre-tensioning and Post-tensioning in Prestressed Concrete

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Pre-tensioning In pre-tensioning, the prestressing reinforcement (strands or bars) are tensioned before the casting of concrete. Once the concrete gains sufficient strength, the prestressing force is transferred from the tendons to the concrete. Stages of Pre-tensioning: Tendon Placement & Tensioning High-strength steel strands are stretched between two end abutments (bulkheads) within a prestressing bed. Concrete Casting Concrete is cast around the tensioned tendons and left to cure. Transfer of Prestress After the concrete attains the required strength, the tendons are cut loose from the abutments. The prestress is transferred to the concrete due to the bond between the tendons and the hardened concrete. Effects of Prestressing The concrete undergoes elastic shortening due to the prestressing force. If tendons are placed eccentrically, the member develops a camber (upward deflection). Post-tensioning In post-tensioning, concrete is cast first , and after it gain...
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Pile cap

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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...
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Binding wire for steel reinforcement

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  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 ...
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stress-strain diagram for aluminium alloy and rubber

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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...
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Repairing of concrete bulging

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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...
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Bridge Diaphragm

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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 ...
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Chamfers for concrete structures

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In general, the edges of concrete members are chamfered. Usually during the process of installing forms for a structural member such as pile cap, a chamfer a PVC chamfer as shown in figure no:1 installed at the edges of the structural members. These chamfers will form smooth slanted edges, as shown in figure no:2. The size of chamfers can be 20x20mm or more as shown on the contract drawing. The PVC chamfer fixed to forms by nails. We should ensure that the PVC chamfer fixed in their correct locations, and we should ensure that the PVC chamfer is straight and not moving up or down. Checking the alignment and location of PVC chamfer is important, so the chamfered concrete edge will have a good appearance after the form’s removal.  Figure 1 Figure 2 Chamfering the concrete edges done for many reasons such as aesthetics, some suggesting that the chamfering of concrete edges done for safety to reduce the damage of objects due to impact with sharp concrete edges. Actually, ...
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Pre-tensioning and Post-tensioning in Prestressed Concrete

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Pre-tensioning In pre-tensioning, the prestressing reinforcement (strands or bars) are tensioned before the casting of concrete. Once the concrete gains sufficient strength, the prestressing force is transferred from the tendons to the concrete. Stages of Pre-tensioning: Tendon Placement & Tensioning High-strength steel strands are stretched between two end abutments (bulkheads) within a prestressing bed. Concrete Casting Concrete is cast around the tensioned tendons and left to cure. Transfer of Prestress After the concrete attains the required strength, the tendons are cut loose from the abutments. The prestress is transferred to the concrete due to the bond between the tendons and the hardened concrete. Effects of Prestressing The concrete undergoes elastic shortening due to the prestressing force. If tendons are placed eccentrically, the member develops a camber (upward deflection). Post-tensioning In post-tensioning, concrete is cast first , and after it gain...
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wing wall arrangement and orientation for abutments

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wing wall main function is to retain the embankment near abutment. the common slope is 2:1. greater than 2:1 is not allowed. figure no: shows a wing wall for the abutment. Figure 1  there is three arrangement for wing wall: wing wall parallel to abutment: easy to build. construction can be done in a short time. this type of wing wall will not disturb the existing embankment and utilities but it is not the most economical arrangement.   figure 2 construction management: concrete construction bridge construction:How to become a bridge engineer wing wall at an angle with abutments: this type is most economical among the three arrangement. Figure 3 wing wall perpendicular to abutment: in this arrangement. wing wall provides a continuous alignment with bridge deck which can be used to support parapets. this arrangement will disturb existing embankment and utilities adjacent to the structure. for curve bridge, this type o...
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why do we stagger reinforcement overlapping?

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First, we should know that steel rebar comes in standard length such as 12m. using very long reinforcement is impractical because it will result in difficulties in handling reinforcement by steel fabricators. Also, longer rebar is heavier and difficult to lift and move. So for a long structure such as a slab, we require a reinforcement length that is more than the standard reinforcement. We can't use a single piece of rebar for a specific length for such a structure, so we use two or more steel rebars to cover the entire length of the structure. Figure no:1 The zone of overlapping between reinforcement will be considered as a weak zone. Therefore, it is a good practice to stagger the reinforcement overlapping. Staggering is done by overlapping the reinforcement at a different location. Staggering reinforcement overlapping will reduce the number of rebars overlapped at the same point, which will be beneficial in two ways. Firstly, it will reduce the discontinuity of rebar at the s...
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Example 1:Flexural stress calculation using transformed area method for rectangular beam with double layer of reinforcing bars

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assume the section for beam shown in figure 1 cracked calculate the flexural stresses for the given load or moment using transformed area method. construction management: concrete construction bridge construction:How to become a bridge engineer Figure 1 first, we will calculate the transformed area of steel. the concrete below the neutral axis will not contribute to resisting of tension. figure 2 shows the section after transformation  As=6*1=6.0in2 Transformed area for first layer=As*n=2*8=16in2 Transformed area for second layer=As*n=4*8=32in2 figure 2 Neutral axis can be calculated by equalling moment of area from both parts as shown below  16*(18-x)+32*(21-x)=(x/2)*(14*x) 960-48x=7x^2 7x^2+48x-960=0 x=8.77 in moment of inertia for transformed area= =(14*8.77^3)/12+8.77*14*4.385^2+16*9.23^2+32*12.23^2=9297.20in4 =0.44835ft4 flexural stress for compression zone. y at extreme compression equal 8.77in=0.73ft fc...
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