FEA of Concrete Structures

It is well-known that reinforced concrete (RC) is one of the important building materials due to its constructibility, economy, and efficiency of the material. Structures properly designed and constructed using RC are acceptable for its stiffness and strength. In general, the designers design all RC structures to satisfy the following things:i) the structure must be strong and safe, ii)the structure must be stiff and appear unblemished, and iii)The structure must be economic.

To satisfy the above goal, advanced analytical tools are indispensable for assessing the performance of the structures(e.g. cracking and deflection under service loads, ultimate load, failure mode and pattern, and load-deformation of structures) constructed using reinforced concrete which is naturally non-linear subjected to external excitations. The nonlinearities are due to a composite materials made up of concrete and reinforcement, nonlinear behavior of concrete itself, and the interaction between reinforcing steel and concrete though bond-slip, aggregate interlocking, and dowel action at the interface of both materials. In addition, the real world structures are usually in the forms of complex in shape and functions; for examples, high rise building, nuclear power plants, bridges, off-shore platforms, and underground structures. These structures thus requires advanced and sophisticated analytical tools. The current tools that implement analytical and numerical methods in assessing the performance of concrete structures are practically adopted the so called Finite Element Analysis "FEA". The development of FEA for concrete structures is very interesting with a long history since 1967 and the next post I will introduce some here.

Introduction to Finite Element Analysis (FEA)

Since this blog is for promoting civil engineers to built the infrastructures using technologies, I am posting various of the current technologies for sharing with everyone. One of the current technologies that is very important for designing and analyzing the infrastructures in civil engineering application is the numerical method so called "Finite Element Analysis (FEA)". I here give the introduction to the method in this post and the subsequent posting topics will be related to the theory and the application on analyzing and designing the infrastructures and civil engineering application using finite elements.

For the history of the method, Finite Element Analysis (FEA) was first developed in 1943 by R. Courant, who utilized the Ritz method of numerical analysis and minimization of variational calculus to obtain approximate solutions to vibration systems. Shortly thereafter, a paper published in 1956 by M. J. Turner, R. W. Clough, H. C. Martin, and L. J. Topp established a broader definition of numerical analysis. The paper centered on the "stiffness and deflection of complex structures". 

 

By the early 70's, FEA was limited to expensive mainframe computers generally owned by the aeronautics, automotive, defense, and nuclear industries. Since the rapid decline in the cost of computers and the phenomenal increase in computing power, FEA has been developed to an incredible precision. Present day supercomputers are now able to produce accurate results for all kinds of parameters.

The simple explanation, on what FEA is, is that FEA consists of a computer model of a material or design that is stressed and analyzed for specific results. It is used in new product design, and existing product refinement. A company is able to verify a proposed design will be able to perform to the client's specifications prior to manufacturing or construction. Modifying an existing product or structure is utilized to qualify the product or structure for a new service condition. In case of structural failure, FEA may be used to help determine the design modifications to meet the new condition.

There are generally two types of analysis that are used in industry: 2-D modeling, and 3-D modeling. While 2-D modeling conserves simplicity and allows the analysis to be run on a relatively normal computer, it tends to yield less accurate results. 3-D modeling, however, produces more accurate results while sacrificing the ability to run on all but the fastest computers effectively. Within each of these modeling schemes, the programmer can insert numerous algorithms (functions) which may make the system behave linearly or non-linearly. Linear systems are far less complex and generally do not take into account plastic deformation. Non-linear systems do account for plastic deformation, and many also are capable of testing a material all the way to fracture.

All above is just a very short introduction to the method and the subsequent posts on the FEA, I will gradually give you more information regarding to the theory and application steps by steps so that by the ends we here could apply the method in our daily civil engineering applications.

Credits: http://www.sv.vt.edu/classes/MSE2094_NoteBook/97ClassProj/num/widas/history.html