Algorithm to modify the geometric characteristics of a composite steel trussed-concrete beams (CSTCB)

Building use

Office building

Country/Region

All Regions

Overview

The research represented in this report deals with a very common structural element in Italy and in many European countries, developed on the basis of a patent issued in 1962: Composite Steel Trussed-Concrete Beams (CSTCB). These are quite common composite construction elements formed by a metal plate that represents the bottom chord of the beam, a series of coupled rebars that form the upper chord and a truss made of rebar, that also work as shear transferring element to the concrete pour.

Issue and/or innovation

Lots of research is available on CSTCB beams but all of them focus on prismatic beams where the upper and bottom chords are parallel and where the diagonals of the truss have a constant spacing. The research presented in the report makes use of an algorithm to modify the geometric characteristics of a CSTCB by changing the height of the section and the distance between the diagonal elements. To do so, the program differentiates two different structural phases: before and after the hardening of the concrete. Before the hardening of the concrete the steel elements are the sole responsible for the entire loadbearing of the elements, and of the slabs the beam is supporting. After the concrete has cured, the beam develops a composite behavior and reaches its full load bearing characteristics. The algorithm presented optimizes the steel elements of the beam tackling both structural phases.

Technical details

The present work deals with the structural optimization of self-supported Composite Steel Trussed-Concrete Beams (CSTCB). CSTCB belongs to the category of prefabricated steel truss embedded in a concrete core casted in situ. The truss is typically composed of a steel plate, which represents the bottom chord, a system of diagonal bars and some coupled rebars working as upper chord. Optimized geometries lead to the minimization of material use. This results in the minimization of the costs, the achievement of sustainability targets, the reduction on the self-weight as well as many architectural advantages. At this purpose, a MATLAB code is herein presented. The code aims to optimize the geometry of the beam by means of a genetic algorithm (ga). Two different operative phases, before and after the concrete hardening, which characterize the mechanical response of the beam, are considered within the code. In addition, a case study is developed showing the application of the Matlab code to a homogenized prismatic beam. Advances beyond the state of the art are therefore shown.

References / Technical Papers Content

M. Deligia, E. Congiu, G.C. Marano, B. Briseghella, L. Fenu, “Structural optimization of composite steel trussed-concrete beams”, Procedia Structural Integrity 33 (2021) 613–622
https://doi.org/10.1016/j.prostr.2021.10.068

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Algorithm to modify the geometric characteristics of a composite steel trussed-concrete beams (CSTCB)