Intro

In the article "strut-and-tie modeling for pier caps", we have discussed the definition of strut-and-tie analysis and how to construct a strut-and-tie model using the example of pier cap. After creating the geometry of a strut-and-tie model, the next step usually is calculating dead and live loads from the superstructure. This article discusses how to determine the boundary loads for a pier cap with a superstructure that has irregular geometries. 

With more users asking us questions regarding pushover analysis and its applications in midas Civil, we want to share the answers to some of these common questions to our user community. Hopefully, this would help you understand pushover analysis in midas Civil environment a little more, and we want you to be more confident when using midas Civil to perform seismic design and analysis. We invited one of our Midas experts Yong Yang, principal structural engineer from Jacobs, to share some of his experience regarding those questions.

There are times when engineers would have to design and evaluate bridge structures that fall outside of the AASHTO design guideline. Therefore, when do we define a structure as irregular? How is evaluating an irregular bridge different from evaluating a regular bridge? How to minimize errors during the construction of irregular bridges? We invited midas expert Percy Penafiel, Professional Engineer Specialist from Nevada Department of Transportation, to answer some of the frequently asked questions from our users regarding evaluating irregular bridge structures. 

In typical engineering practices, engineers are used to having six degrees of freedom (DOFs) for modeling and analysis, three for rotations and three for translation. However, additional advanced beam elements can include other DOFs to represent the warping of an open thin-walled cross section. Such elements are not commonly available in professional software. (Article 1.2.6, G13.1 Guidelines for Steel Girder Bridge Analysis, AASHTO/NSBA, 2014). This has required engineers to model flanges as plates in order to obtain warping stresses. Midas Civil on the other hand has the 7th DOF warping feature which should save engineers a lot of time and effort and can grant warping related results directly from frame elements. 

This tip talks about different types of links that you can find in midas Civil and their applications. You may be wondering what are the implications of using one type of link compared to another, this tip will answer that for you and help you gain more confidence when choosing the link types. 

When we talk about prestressed concrete, the things that we are mostly concerned about are the compressive strength gain with respect to time, and the prestressing tendon relaxation with respect to time. Figure 1 shows various time-dependent effects for concrete including creep and shrinkage.

The factors that affect the creep rate include water/cement ratio, age and strength of the concrete when it is subjected to stress, and ambient temperature and humidity. Creep rate also depends on many other factors related to the quality of the concrete and conditions of exposure such as the type, amount, and maximum size of aggregate; type of cement; amount of cement paste; size and shape of the concrete mass; amount of steel reinforcement; and curing conditions (Robert Salca, tech support, midas UK).

For shrinkage, its rate decreases much faster with time compared with creep as shown in figure 1. Finer aggregates and finer gels result in increased shrinkage, the moisture content of the concrete and the relative humidity of the ambient medium have a big influence on carbonation shrinkage, and harder aggregates with higher modulus of elasticity decrease shrinkage. 

So you have learned about column buckling under a point load applied at the end of the column, do you know if columns can buckle under their self-weight? Let’s explore it and run some analyses using midas Civil.

Concrete Shear Equation