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Shear and moment diagram part 1

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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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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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Rebar Splicing and Overlapping — ACI 318-19 Requirements Explained

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Reinforcement splicing or overlapping is a fundamental requirement in reinforced concrete structures. Because reinforcement bars (rebars) are manufactured in limited standard lengths—typically 12 m —it becomes necessary to splice or overlap them to achieve the required continuity in structural members. The main purpose of a splice is to ensure smooth stress transfer between adjacent bars through the surrounding concrete. The overlap length, commonly known as the splice length , must be long enough to safely transfer the tensile stresses from steel to concrete without causing bond failure. It is recommended to avoid splicing in high-stress zones such as areas of maximum moment, and to stagger the splices to prevent congestion and reduce stress concentration. The ACI 318-19 providing the following recommendatin and requirement for the lap splicing: 1. Splice Limitation by Bar Size Lap splicing is not permitted for reinforcement bars larger than 36 mm in diameter. 2. Non-Contact L...
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Prestressing strand manufacturing

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  Prestressing strands is high tensile strength steel. The tensile strength of prestressing strands can reach up to 1860 Mpa. the process of manufacturing prestressing steel differs significantly from the conventional reinforcement.  Figure 1 The process of manufacturing strands will begin by de-scaling the raw material (wire rod). The purpose of de-scaling is to remove the iron oxides (mill scale) from the surface of the wire rod. after removing the mill scale, the wire rod's surface is coated with a textured coating to enhance the adherence of lubricants to the raw material surface. The most commonly used coating is zinc phosphate.  Figure 2 The wire rod then passed through a series of dies. The process of reducing the wire rod diameter is known as cold-drawing. In this process, the wire rod is drawn through a die with the required diameter. To prevent the wearing of dies, the wire rod will be drawn through a lubricant box. the lubricant will coat the wire with a thin l...
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The reasons behind the trimming of pile head

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  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 process, the se...
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Tremie pipe for piles

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Tremie pipe can be defined as segments of steel pipe. These segments will be connected together and used to cast a drilled pile foundation. Using of tremie pipe will prevent the segregation of concrete. Tremie pipe will ensure that the concrete is not thrown from a huge height. As we know, placing the concrete from any distance higher than 1.5 m can cause concrete segregation. Therefore, tremie pipes are used. The tremie pipe segment will be connected to a length equal to pile length. Then it will be lowered to the bottom of the pile hole. Figure no:1 shows a tremie pipe inserted inside the casing and steel cage of a pile before beginning with the concerting of the pile.  Figure 1 We should always ensure that the tremie pipe external diameter is suitable. We should ensure that the tremie pipe doesn't clash with the steel cage or any spacer blocks. Also, we should make sure that the internal diameter of the tremie pipe is sufficiently bigger than the maximum size of concrete aggrega...
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Crosshole Sonic logging test

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Cross-Hole Sonic Logging (CSL) Test The Cross-Hole Sonic Logging (CSL) test is a more advanced method compared to conventional integrity testing. It is primarily used to assess the quality of concrete in deep foundations, particularly in cast-in-place piles. Principle of CSL Testing Prior to pile casting, access tubes are securely fixed inside the steel reinforcement cages. The CSL test evaluates potential defects in the pile concrete shaft by measuring: First Arrival Time (FAT): The time taken for the ultrasonic pulse to travel between the transmitter and receiver. Wave Energy: The strength of the received ultrasonic wave. The wave velocity is calculated using the formula: This calculated velocity is then compared to the expected velocity of sound waves in concrete. Lower wave speeds and weak energy signals indicate potential defects, such as voids, honeycombing, or inclusions within the concrete pile. construction management: concrete constructi...
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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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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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Tunnel lining systems-Ribbed system

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Ribbed supporting system has been used for many years to support tunnels. The ribbed supporting system is based on steel ribs supporting tunnels. The implementation of this system involves the installation of rolled steel sections around the circumference at specified spaces. The formation of gaps between the steel ribs and the ground is very common. These gaps should be suitably wedged to avoid excessive deformation of the ground. It is essential to ensure that the loads are distributed evenly by the steel support around the tunnel profile. Subjecting of steel support to point load will significantly reduce their ultimate capacity.  Figure 1 The steel ribs can be combined with shotcrete concrete. The shotcrete concrete will be applied before the erecting of ribs. The applying of a layer of shotcrete concrete will reduce the problems of gaps between ribs and surrounding ground, which minimize the wedging problems. Then another layer of shotcrete can be applied afte...
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