Construction and Civil Engineering News and Knowledge

Structural Engineering

Assumptions, simplifications in engineering theory and design -

Engineers make assumptions all the time. All these assumptions are backed up by logic and theory, so instead of pursuing exact values, in civil engineering often times we are okay with close enough values, as long as the results are within acceptable limits and we can justify it with relevant proven theory. Doing so, saves a great deal of time and effort, which makes developing theory or designing and solving problems possible in reasonable amount of time and with reasonable effort. Let’s randomly list some examples below. These are structural examples but the same kind of approach applies to any branch in civil engineering and other engineering disciplines as well. […] Read More

General Steps of Structural Analysis for Nonengineers – A Roadmap -

Simple structural frame with external loads

For non engineers, structural analysis may seem like an overly complex subject. A person who is not a civil engineer will never be required or even allowed to solve a real structure, but it is still good to give some general idea for learning. This came to my mind when I heard a question once, from a nonengineer, who drew sketch of a really simple structure and asked if we solve this member by member such as column by column, slab by slab and beam by beam. This is of course not correct and civil engineers know that it doesn’t work that way… So for people who are not civil […] Read More

Equivalent Static Method and Response Spectrum Method in Seismic Analysis -

In seismic analysis of structures, Equivalent Static Analysis and Response Spectrum Analysis are two methods that analyze the elastic behavior of a structure, in other words, the behavior of the structure without considering any yields (plastic hinges). But how do they differ? Equivalent Static Analysis is the simplest most straightforward analysis, which will either suffice for simpler structures or you need to do anyway to get a feel for how would it be if the loading was static and the structure remained elastic. This method is good for short period, stiffer structures such as short buildings. Here the building is not tall enough for instance, to meaningfully produce higher vibration […] Read More

Strut and Tie Method -

This is a very useful method, which is also allowed by AASHTO or bridges and ACI 318 when designing concrete bridge and building structures respectively. By making use of this method, the stresses especially in members such as deep beams can be more realistically represented. The struts here represent the imaginary compression members of a truss and ties are the imaginary tension members. We place reinforcing steel in place of tension members. To be able to correctly construct a strut and tie model requires good understanding of how the structure works. Read More

Why earthquake loads are considered when analyzing beams? -

We must consider earthquake loads when analyzing all members of a structural system. A structure is a whole unit, inseparable from each other. One effect on one member has effect on other members. Therefore we can not just isolate beams and say “earthquake loads are lateral so why do we analyze beams for earthquake” At the most basic level, the beams hold the columns together laterally and determine the sway amount of the structure, not to mention the torsion effects that the columns and shear walls resists and working together with the beams while doing so. In short, the structural frame of a building is a whole system that takes […] Read More