Examination of stiffness of stack of steel elements forming part of supports used for removal of building deflections

2020

Materials

Self Cite

There are many vertically deflected building structures in the world that require rectification. Temporary supports installed in the building bearing walls can be used to perform such a rectification. The supports consist of a hydraulic piston jack, a stack of parallelepiped steel elements, and a concrete grout. The structure is unevenly raised and reaches the desired vertical position using such supports. The support in which the piston extension is forced at the given time is an active support. The aim was to determine the stiffness of an active support. The investigations were performed in in situ conditions during experimental building rectification. No such investigations have been performed to date. It has been demonstrated that the stiffness of the investigated support results from the stiffness of the serially connected elements forming the support. In general, the support stiffness depends on the value of the force occurring in the support and is rising linearly along with the load for the investigated range. It was also shown that the force existing in the active support also depends on the stiffness of the building being rectified. The investigations carried out show that it is advantageous to use supports with smaller stiffness for rectification, as forces with smaller values must be induced in them. The application of forces with lower values also allows the avoidance of unfavorable penetration of the unlifted part of the building into the ground.

Section: Introductionmentioning

confidence: 99%

In Situ Experimental Study on the Active Support Used for Building Rectification

2020

Materials

Self Cite

“…There are few tests on supports composed of the jack and a stack of cuboidal elements. However, they only referred to axially compressed supports of stacks made of cuboidal wooden [ 24 ] and steel [ 25 ] elements. Moreover, such supports examined in situ [ 26 ] showed their stiffness has a decisive impact on parameters of a rectified building.…”

Section: Introductionmentioning

confidence: 99%

Effect of Eccentricity of Applied Force and Geometrical Imperfections on Stiffness of Stack of Cuboidal Steel Elements

Smolana

2020

Materials

Self Cite

Experimental tests were performed on a stack of cuboidal steel elements and its mathematical model was developed. Each cuboidal element was made of rolled profiles. Such stacks are the part of temporary supports that can be used to eliminate deflections of buildings. Stacks were loaded eccentrically through the inaccurate position of a jack. Moreover, two types of geometrical imperfections could be noticed. They included inaccurate contact between the stack elements and initial relative displacements of profiles that formed cuboidal elements. A mathematical model was developed to describe deformations of the stack and its parameters were determined by analysing test results. The eccentricity of the applied force had a slight impact on the stack stiffness, which was considerably reduced by geometrical imperfections. The imperfection covering initial relative displacements of rolled profiles inside cuboidal elements had the greatest impact on the stiffness. It could cause even a 10-fold drop in the stack stiffness when compared with the theoretical stiffness resulting from the stiffness of the stack section, and the stiffness dropped by ca. 3.5 times when the imperfection included the inaccurate contact between the cuboidal elements. Finally, the occurrence of both types of geometrical imperfections generated the real stiffness more than ten times lower than the theoretical stiffness that did not take into account imperfections.

Examples of Even Lifting of Structural Elements of Existing Buildings

IOP Conf. Ser.: Mater. Sci. Eng.

2020

Two examples of even, vertical lifting of building elements are presented. In the first example, after the raw state of the building was completed, the concept of land development around the building has changed. It involved in particular elevating the ground level by 0.8 m. As a consequence, the entrance to the building would be below the surrounding land. It was decided to lift the above-ground part of the building evenly by 0.80 m in order to avoid this. The lifting of the above-ground part of the building was designed and executed by detaching the building apart at the level of the floor and then lifting it evenly by 0.8 m. For this purpose, eighteen hydraulic jacks were used, installed in the bearing walls in the previously made openings. New technical cellars were additionally constructed as a result of the works. In the second case, the roof truss was raised in the residential building in use. The usable area of the attic was enlarged as a result of the works and the number of posts limiting the freedom of interior design was reduced. In both cases, a system of hydraulic jacks was used to move the structure vertically. With the presented procedure, no damage was caused to both, the building elements that were lifted and those unmoved. In addition, the even lifting of parts of the building allowed to avoid the troublesome dismantling and then restoration in a new location.