by DO THE LIGHT THINGS LIGHT.
Concrete bridges are one of the most common forms of bridges in the world, using reinforced concrete as the main construction material..
It is highly popular due to its strong durability, reliability, flexibility, and economy..
How concrete structure bridges are verified in CDN? In the following serialization, we will provide a detailed introduction to bridge engineers..
The design section will be serialized in three parts: “upper, middle, and lower”. Please continue to follow us.
Important: After the model is successfully imported, the first step is to switch to the appropriate specification, and then the verification items need to be set..
This section contains the items that must be filled in the CDN specification settings.
“3D” (default): Design according to bending, shearing, and twisting components, considering Mz (but not Vy).
“Two dimensional”: designed according to bending and shearing components, without considering torque and Mz.
“Two dimensional+torque”: designed according to bending, shearing, and twisting components, without considering Mz and Vy.
Generally, the default selection for beam verification is “3D”. When conducting shear flexible beam grid or folded beam grid verification, the overall box beam has already been cut open and no longer conforms to the original shear flow. Therefore, according to personal understanding and needs, the impact of torque can be ignored..
Screenshot taken from “Design Specification for Highway Reinforced Concrete and Pre stressed Concrete Bridges and Culverts JTG 3362-2018”.
According to the type of geological exploration environment, the selection will affect the crack width calculation limit of RC components or PSC-B class components..
”Class A components: tensile stress is allowed, but cracks are not allowed for finite values of tensile stress..
Class B components: cracks are allowed, but the crack width is limited..
After selecting the corresponding design component type, the program will retrieve the corresponding formula for crack resistance calculation..
Screenshot taken from “Design Specification for Highway Reinforced Concrete and Pre stressed Concrete Bridges and Culverts JTG 3362-2018”.
The construction methods of “prefabrication” and “cast-in-place” can be selected according to the actual situation..
Screenshot taken from “Design Specification for Highway Reinforced Concrete and Pre stressed Concrete Bridges and Culverts JTG 3362-2018”.
When conducting torsional verification, it is necessary to calculate the torsional reduction coefficient β t. Among them, when calculating Wt, you can check “flange+web” or “web”..
For the box section in the specification JTG 3362-2018, as shown in the following figure, only the torsional resistance moment of the box compartment is considered, which is equivalent to checking the “web plate”;.
Screenshot taken from “Design Specification for Highway Reinforced Concrete and Pre stressed Concrete Bridges and Culverts JTG 3362-2018”.
This section includes calculation methods that can be considered or customizable during verification.
1> Bending resistance calculation – numerical cross-section for design is calculated using any cross-section.
After selecting this option, when checking the bending bearing capacity, the specific values of b and h are no longer obtained from the Z1-3 position of the section and substituted into the standard formula for calculation. Instead, the area of the compression zone is calculated by changing the formula. Unconventional cross-sections (such as fishbelly cross-sections) can be attempted by checking this option, while general cross-sections do not need to be checked..
Note: This method is not a standardized calculation method, so it is recommended to judge or compare the results on your own..
Screenshot taken from “Design Specification for Highway Reinforced Concrete and Pre stressed Concrete Bridges and Culverts JTG 3362-2018”.
According to Article 5.2.9 (3) of the JTG 3362-2018 specification in the above figure, when calculating the effective height h0, the longitudinal tensile steel bars can be disregarded as bent steel bars..
As shown in the figure below, the pink line represents the prestressed steel tendon. Due to the upward bending at the fulcrum position, h0 will gradually decrease, which may cause the section verification to fail first. According to the article description, we may not consider the bending of steel strands. For example, if this option is entered as 0.2h, the steel strands above the yellow dashed line in the figure will no longer be considered..
