【Haichuan Construction Technology】How to distinguish between the stress-bearing bars, distribution bars, stirrups, erection bars, continuous bars, negative bars, tie bars, and web bars in building structures
Thread Content
Reinforcing bars refer to those steel bars that are placed at the bottom of beams or slabs, serving to bear tensile forces, as well as bars designed to resist shear forces, bending bars, and suspension bars. How can one distinguish between the load-bearing bars and the distribution bars in a slab? (1) Classification by the span and depth of the slab: In the case of a single slab, the rebar parallel to the short span direction is the load-bearing rebar, while the rebar parallel to the long span direction is the tie rebar. If it is a double-web slab, then all the rebars in the long-span and short-span directions are load-bearing rebars. (2) Classification by rebar diameter: Rebars with a larger diameter are used as load-bearing bars, while those with a smaller diameter serve as distribution bars ； (3) Classification by arrangement: For positive moment members, the rebar placed at the bottom is the load-bearing rebar, while the rebar arranged vertically above it is the distribution rebar. For negative moment members (such as cantilever slabs), the situation is reversed – the rebar at the bottom is the distribution rebar, and the rebar above it is the load-bearing rebar. Distribution bars appear in the slab, are arranged above the load-bearing rebars, and are perpendicular to them. Its function is to fix the position of the load-bearing rebar and distribute the loads on the slab to those rebars; it also prevents cracks from forming in the direction perpendicular to the load-bearing rebar due to factors such as concrete shrinkage and temperature changes. It belongs to the category of structural rebar. (Meeting the construction requirements, the reinforcement provided is structural reinforcement to account for various factors that are difficult to calculate or have not been taken into consideration.) ）
Stirrups are used to ensure the shear strength of inclined sections, to connect the tensile main reinforcement with the compressive concrete so that they work together, and also to fix the position of the main reinforcement, thereby forming a reinforcement framework within the beam. It is the ring-shaped steel reinforcement (which can be circular or rectangular) arranged to enable beams and columns to resist shear forces; it has a cross-shaped configuration that fixes the steel reinforcement at the top and bottom, thereby helping to resist shear forces. The stirrups are the rebar located in the upper part of the beam; they serve only a structural purpose and have no practical significance. However, at both ends of the beam, the stirrups in the upper part are necessary to resist negative bending moments. (The erection rebar is placed on both sides of the outer edge of the compressive zone of the beam, to secure the stirrups and form the rebar framework. If longitudinal compression reinforcement is provided in the compressed zone, it may not be necessary to provide stirrups. The diameter of the rebar used depends on the span of the beam. ) A through-reinforcement refers to a steel bar that runs across the entire length of a component such as a beam, without bending or breaking at any point. When the bar is too long, it can be lapped or welded together, but its diameter remains unchanged.
What is the difference between stirrups and continuous bars? In terms of reinforcement layout, the vertical rebar constitutes 1/3 of the reinforcement for that span. In other words, the beam in question has rebar at both the left and right supports. The continuous rebar is arranged throughout the entire length; the vertical rebar serves to provide support and also bears some compressive load, which can help increase the beam’s load-bearing capacity to a certain extent. A through bar is a steel bar that runs across the entire length of a component such as a beam, without bending or breaking in the middle. When the bar is too long, it can be lapped or welded together, but its diameter remains unchanged. The tie bar can be either a load-bearing rebar or a framing rebar. The stirrups can also be continuous; as specified in the codes, the stirrups on both sides of the upper part of the beam must be continuous, and in such cases they can also bear a portion of the negative bending moment at the supports. If there are continuous rebar on both the top and bottom of the beam, generally the rebar located on the top side of the beam (in the compressive zone) and with a smaller diameter is the tie bar, while those on the bottom side are the load-bearing rebar.
Negative stress steel bars refer to those that bear negative bending moments. Bending moment is defined as positive when tension acts on the lower part; whereas the upper steel bars in beams and slabs are generally under tension at the support areas, meaning they bear negative bending moments, which is why they are called negative bending moment steel bars. (The support has negative reinforcement; this is a relative term. It generally refers to the rebar at the beam’s supports used to counteract negative bending moments, commonly known as load-bearing rebar.) In general structural members, the bending moments are divided into positive and negative moments. The rebar used to resist negative moments is referred to as negative reinforcement; this usually refers to the rebar located in the upper part of slabs and beams. Some of the structural rebar placed in the upper area is also conventionally called negative reinforcement. When the upper reinforcement in beams and slabs runs the full length, it is also commonly referred to as upper reinforcement; the reinforcement on the surface of beams or slabs is known as negative reinforcement. Bonding reinforcement refers to the reinforcement that is provided between two or more components that cannot be constructed simultaneously, serving to create a bonding effect. It strengthens the steel reinforcement that connects the frame infill walls to the columns, thereby improving the stability and seismic resistance of the infill walls. The abdominal reinforcement is generally located in the middle section on both sides of the beam; it represents the structural rebar in the middle part of the beam. This is because some beams are too tall, and it is necessary to add connecting bars in the middle of the stirrups (the longitudinal structural rebar on the sides of the beam is actually referred to as waist rebar). When the beam’s height is 450 mm, waist rebar should be installed along both sides of the beam’s height, so the number of such bars will not be less than 2. The minimum diameter of the vertical reinforcement bars is 10 mm; the spacing between them should not exceed 200 mm. Additionally, the area reinforcement ratio should be no less than 0.3%. Tie bars should also be installed between the longitudinal structural reinforcement bars (vertical reinforcement bars) on both sides of the beam. For ordinary civil buildings, a diameter of 16 or 18 is sufficient for the reinforcing bars, while a diameter of 8 is appropriate for the tensioning bars.
【HaiChuan Overseas Engineering】CNPC Engineering wins contract for $1.6 billion Iraq Atawi gas processing plant project https://bbs.hcbbs.com/thread-5703613-1-1.html (Source: HaiChuan Chemical Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】From 2756 to 2025: The petroleum university team made significant breakthroughs in oil and gas pipeline technology using sound-magnetic hybrid ultra-high-definition detection technology. https://bbs.hcbbs.com/thread-5703161-1-1.html (Source: Haichuan Chemical Engineering Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】From 2017 to 2024, CNPC Pipeline Bureau made breakthroughs in key technologies for flexible welding robots in mountainous areas! https://bbs.hcbbs.com/thread-5703164-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】From 2017 to 2024, CNPC Pipeline Bureau made breakthroughs in key technologies for flexible welding robots in mountainous areas! https://bbs.hcbbs.com/thread-5703164-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Equipment】Major breakthroughs achieved in the development of metallocene catalysts at the Jilin Petrochemical Research Institute of Sinopec from 2025 to 2759 https://bbs.hcbbs.com/thread-5703175-1-1.html (Source: Haichuan Chemical Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】2760-2025: Shaanxi Electronics successfully developed the world’s first intelligent unmanned fire truck https://bbs.hcbbs.com/thread-5703200-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】2761-2025: The First Intelligent Unmanned Fire Truck with a New Energy Chassis for Rapid Deployment https://bbs.hcbbs.com/thread-5703201-1-1.html (Source: Haichuan Chemical Engineering Forum)