Name: Thiago Tononi Turini
Type: MSc dissertation
Publication date: 12/03/2021

Namesort descending Role
Adenilcia Fernanda Grobério Calenzani Advisor *

Examining board:

Namesort descending Role
Adenilcia Fernanda Grobério Calenzani Advisor *
Elcio Cassimiro Alves Internal Examiner *
Marcela Novischi Kataoka External Examiner *

Summary: Composite steel and concrete beams with external prestressing is an underused
structural system in Brazil due in part to the lack of standardization for its calculation.
This work aims to propose a methodology for the analysis and design of composite
steel and concrete beams supported with external prestressing, considering the effects
of prestressing force and using the requirements of ABNT NBR 8800:2008 and ABNT
NBR 6118:2014. A computational program was elaborated to automate the calculation
of prestressed steel and concrete composite beams according to the proposed
methodology, for the cases of pre-tensioning or post-tensioning, in beams constituted
by steel profiles of section I doubly symmetrical, solid slabs or mixed steel and concrete
and straight or polygonal cables. The proposed calculation methodology was
evaluated by comparing the results of the computer program with the experimental
results in the last load literature, in prestressed beams submitted to positive and
negative moments. In addition, a parametric study with 120 models of prestressed
composite beams was performed to analyze the influence, strength and stiffness of
these beams, of parameters such as: (i) eccentricity of the prestressing cable, (ii) ratio
between span and height of the beam, (iii) height of the concrete slab, (iv) percentage
of the maximum prestressing force, (v) type of slab, mixed or massive, (vi) cable layout,
straight or polygonal and (vii) prestressing technique, pre-traction or post-traction. The
results showed that there is no specific configuration that is the best in all cases and
should always analyze what is the critical situation of each project to select the best
solution. It was observed that the use of the polygonal tracing presents greater losses
of prestressing, in comparison with the straight cable, however it has the advantage of
canceling or reducing the negative bending moment in the supports of the structure.
For post-tensioned beams, the ratio between the span length and the height of the
beam can reach a maximum value between 35 and 40, while for pre-tensioned beams
the maximum ratio is between 30 and 35. The height of the slab linearly influences the
strength, regardless of the type of slab used. Pre-tensioned beams show better
deformation behavior than post-tensioned beams, while in the simplified floor vibration
analysis, post-tensioned structures have an advantage.
Keywords: Prestressed Composite Beams. External Prestressing. Pres-tress and
Post-stress. Analysis and Design Methodology.

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