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When performing the Rail-Structure Interaction (RSI), It is often found that the stress limits are exceeding the permissible values. So there are some countermeasures to ensure safety. Let’s look at how we can implement these control measures which affect the stresses in rails when performing rail structure interaction.
With the recent development of high-speed trains globally, structural interaction plays an important role in estimating the impact of rail on the bridge and the optimum design of the bridge system for the safe passage of trains without disturbing the passengers' riding comfort. The UIC 774-3, Eurocode in 1991-2, RDSO, Korean code, ACI, and various codes and standards provide methodologies for considering rail-bridge interaction problems in the design and analysis of railway bridges. These guidelines take into account the dynamic interactions between trains and bridges, which can affect the stress, displacement, and stability of the rail during train passage. Based on experimental and numerical studies, these guidelines provide limiting values for stress, displacement, and stability of the rail to ensure railway bridges' safe and reliable performance. These limiting values are derived to prevent excessive deformations and stress in the rail that could lead to failure of the rail or other bridge components.
The newly to be released MIDAS CIVIL NX has an API feature installed. API stands for Application Programming Interface, which is a language used for communication between the operating system and applications. In other words, a communication environment has been set up where you can send or receive data from MIDAS CIVIL NX through the API. However, to utilize the API, you need to know how to code using a development language. It feels like there's more to do because you need to know how to code.
In Prestressed concrete structures, the prestressing force is a crucial variable type. The behaviors of pre-stressed concrete structures depend on the effective prestress because it provides compressive stresses to counteract the tensile stresses that develop in the concrete due to loads. However, the prestressing force does not remain constant over time due to various factors that cause prestress losses. These losses can occur during the transfer of prestress from the tendons to the concrete member or over the service life of the structure.
Recent surveys indicate that 78% of civil engineering graduates in the United States felt that what they learned in school didn't translate well into practical application. Why is there such a disparity between academia and real-world practice? The primary reason is that while universities predominantly focus on 2D-based mechanics, practical design involves considering various load combinations and complex structures.
Differential shrinkage is a phenomenon that occurs in composite sections, which are made up of different materials or different grades of concrete, as the different materials will experience a different rate of shrinkage (i.e., PSC composite I Girder). In this article, we will focus on differential shrinkage due to the different time-dependent effects for the composite section consisting of the same material with different grades of concrete for the deck slab and the girder. Differential shrinkage is an important concept to consider when designing composite sections even when the same material is used for both the girder and deck, the age difference will cause the differential shrinkage effects. This will induce different time-dependent effects on both since both the parts are integrally connected internal stress will be generated to reduce the differential effect.
Temperature loads threaten bridge safety, especially for long-span bridges. If the bridge is located with a big temperature difference, A structural engineer analyzes and designs a bridge based on the beam theory. The temperature gradient should be considered with the beam theory. The beam theory assumes the beam deforms primarily in one direction, the material behaves linearly elastic, and the beam has a uniform cross-section. It means even if the beam cross-section gets a different thermal expansion depending on the depth, the cross-section does not change, and it is also possible to substitute thermal stress as a self-equilibrating stress in restraint conditions.
I'd like to share my old experience with the Tendon Profile.
To design structures, we must necessarily create load combinations. These combinations change depending on the state of the loads affecting the structure, and the coefficients considered for these loads vary according to standards. Therefore, while automatically generated load combinations are used for convenience in creating various load combinations, it is difficult to generate combinations that satisfy all conditions.
Designing a curved bridge was a challenge for me in every aspect. The tendon profile in MIDAS Civil, which we covered before, it’s a very well-known issue,
In India, the IS codes, or Indian Standards codes, play a crucial role in ensuring the quality, safety, and reliability of structures in India. It serves as an essential benchmarks to guide the design, construction, modification, and upkeep of structures. These codes are formulated by the Bureau of Indian Standards (BIS), a national body that develops and publishes standards to promote quality and consistency across various industries. These codes are reviewed from time to time and updated to reflect the latest developments in industries.
I would like to introduce the basic and advanced information about MIDAS API. I was surprised that many users wanted to use MIDAS API and asked when we could start to use it. Users have contacted us worldwide regardless of specific regions, company size, and areas.
In this section, we will discuss the damping method applied to Nonlinear Boundary Time History Analysis.
There are four types of damping methods.
Time History Load Cases - Damping Method
The four damping methods are categorized for analysis purposes as follows.
The method of applying damping varies depending on whether you want to apply the same damping to all elements of the structure or not.
The options you choose also depend on whether you use the Modal or Direct Integration methods. The two methods differ in how they account for damping, which can lead to much longer analysis times depending on the selected damping method.
Depending on the analysis method, the recommended damping method is as follows
The Mass & Stiffness Proportional method is Rayleigh Damping, which assumes that the damping matrix can be constructed as a linear sum of the mass and stiffness matrices, expressed by the equation below.
Here, a and b are the damping coefficients, which can be represented by the natural frequency (w) and damping ratio (h) of the two modes.
I n MIDAS CIVIL, enter the natural frequency (or period) and damping ratio (typically 0.05) for the two modes.
A common question we get is what values should be entered for Mode 1 and Mode 2. (Is it enough to enter the period values for Mode 1 and Mode 2, or what period values should be entered?)
Let's take a look at a quick overview of Rayleigh Damping to get a better understanding.
The graph above is for Rayleigh Damping (Mass - Stiffness Proportional Damping).
With two natural frequencies (or periods) and a damping ratio, the coefficients a and b can be calculated, and thus the damping ratio at any frequency can be calculated.
We typically apply a damping ratio of 0.05. However, the determination of two natural frequencies (W1 and W2) with a damping ratio of 0.05 requires engineering judgment.