STRESS-DEFORMED STATE OF INTERMEDIATE SUPPORTS OF INSEPARABLE PERFORATED BEAMS UNDER SYMMETRICAL LOADING

Abstract

Despite the large number of theoretical and experimental studies of solid and inseparable beams, as well as structures using perforated elements, the calculation and design of inseparable perforated beams, especially near intermediate supports, has significant differences compared to solid beams, which are currently little studied and this is a deterrent to the wider use of such beams. For them, another factor that affects the bearing capacity, in addition to the value, nature of the action, type, scheme of action of the load; material strength; the value of the span; geometrical parameters of section, there is a constructin of intermediate support parts.

The current design standards of steel structures present the general principles of design of perforated beams, formulas for calculating stresses at characteristic points of cross section with a hole are given  and emphasize the need to strengthen the cross section on the support by transverse stiffeners. In other matters, the perforated beams are subject to the same requirements as conventional rolling beams. These requirements apply only to single-span beams, and the design features of multi-span continuous perforated beams are not considered at all.

The aim of these studies is to study the stress-strain state of different types of intermediate supports of inseparable perforated beams of I-beam profile of different heights under the action of symmetrically in two spans evenly distributed load in the software complex "Lira". The objectives of the study are to establish the actual values of stresses in the characteristic sections on the supports of inseparable perforated beams of the I-beam profile and perform a comparative analysis of the results of numerical studies. Modeling of beams is made in the software complex "Lira" on the basis of a method of finite elements with observance of the real sizes with all design features of support parts. Support parts with welded and unwelded holes, as well as without a stiffening rib or with a stiffening rib placed along the axis of the intermediate support are accepted for consideration.

The analysis of the stresses obtained as a result of the calculation of the diagram shows a significant change in the stress-strain state of the calculated cross sections as they approach from the middle of the span of the beam to the axis of the intermediate support. In the middle part of the beam, the stress distribution in the section with the hole is traditional - stresses at the points of cross section of the upper part of the I-beam have a sign "minus", and at the points of cross section of the lower part - sign "plus" in full accordance with the diagram of bending moment. The nature of the stress distribution at the calculated points of the support cross sections has significant differences due to the change in the sign of the bending moment and the transverse force.

As a result of the calculation by the finite element method in the software complex "Lira" under the action of symmetrically distributed in the spans load were received the data on the stress-strain state of different types of intermediate supports of two-span inseparable perforated beams.