Motives for better Engineering
Explore horizontal earth pressure,
Coulomb's theory, and its applications.
Compare geotechnical results and
understand the trial wedge method's nuances.
Explore the technical content on vessel collision
to calculate the annual frequency of bridge component collapse.
Introducing the concept of seismic isolation design.
See more
The blog article of Creep Analysis 3 showed how Dr. Ghali et al. explained the creep analysis by flexibility methods.
To better understand the creep behavior, solve the previous example in a less efficient way. Here, different sign conventions will be applied.
We have gone through two different approaches by Dr. El-Badry so far. You can find the previous articles via these two links: Creep Analysis 1, Creep Analysis 2.
For creep analysis, the most common problem in the real-world design is continuous girders built as span by span. This example is very well explained by Dr. Ghali et al. (Concrete structures, Stresses, and deformations, 4th ed., CRC press, Example 4-2). Dr. Ghali et al. explained this problem by flexibility methods. The author will solve this same problem by stiffness methods. The programs do the matrix formulation and equation solve, and only the load matrix formulation and post-processing are our concern in the stiffness methods. Two MIDAS files are attached.
First, the author wants to define the sign convention for member forces clearly.
The midas model is for a multi-channel prestressed girders bridge 30 ft span and 24.75 ft width. The bridge is composed of 9-channel prestressed girders placed side by side. The bridge was modeled with frame elements for the girder's webs and plate elements for the girder's flange. Bridge dimensions and midas models are shown below.
The scary part of FEM is sometimes FEM gives wrong results without any error message. The analysis may be meaningless if an engineer cannot check or interpret the results. Let’s consider a simple example similar to the case from Dr. Gallagher (Finite Element Analysis: Fundamentals, 1975).
For the previous example, we can use high-order triangular elements. This element has six nodes per element and assumes the displacement is quadratic within an element. Also, each side edge can be curved, as shown.
Continuing on to the third part of this multi-part blog, another option is a quadrilateral element. As always, let’s start with an example.
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.