Self-supporting tests in lattice joists subject to negative bending

Abstract

During the construction of bridges, cantilever roofs and eaves, assembling formworks and scaffold that will support the slabs is a point of difficulty in the construction phase. Therefore, it is relevant the study of the lattice joists which serve as self-supporting formwork, supporting its weight, the weight of the fresh concrete, the weight of workers and the weight of concreting equipment. The analysis of the bearing capacity of lattice joists subject to negative bending with base concrete opening enables checking the maximum span that each lattice truss model bears, either cantilevered or between continuous spans with reduced or no scaffold. The concrete opening enables the monolithism between the slab and its support. This paper presents the results of tests on lattice joist with concrete opening. By the results analysis, formulations for designing the spacing between prop lines were found. The results are promising and indicate great possibilities of using lattice joists with concrete opening over the supports (beams), in order to optimize the slab shuttering.

Theoretical and experimental analysis of precast slabs composed of pre-stressed joists

“…The results of Figure 3 could be attributed to the stress distribution in the transversal section of the joist. Under the 3-point flexural bending test, one side came under tension and the other under compression [33]. Reinforcement increased tensile strength considerably and, as the load increases, overloaded the compression side of the structure.…”