Precast/Prestressed Concrete Truss-Girder for Roof Applications

摘要

Steel trusses are the most popular system for supporting long span roofs in commercial buildings, such as warehouses and aircraft hangars. There are several advantages of steel trusses, such as lightweight, ease of handling and erection, and geometric flexibility. However, they have some drawbacks, such as high material and maintenance cost, and low fire resistance. In this paper, a precast concrete truss is proposed as an alternative to steel trusses for spans up to 160 ft. without intermediate supports. The proposed design is easy to produce and has lower construction and maintenance costs than steel trusses. The proposed design is an evolution of the system that was developed by e.Construct USA, LLC and was used in the construction of a cement storage facility at United Arab of Emirates. The proposed truss design consists of two segments that are formed using standard bridge girder forms (PCI and AASHTO girders) with block-outs in the web that result in having diagonals and vertical sections. The two segments are then connected using a wet joint and post-tensioned longitudinally. The proposed design optimizes the truss-girder member locations, cross-sections, and material use. A Finite Element Analysis for the truss-girder system is conducted to investigate stresses at truss connections and the wet joint. A 30-foot long truss specimen is constructed at the structural laboratory of UNL to investigate the constructability of the truss and the structural capacity of the diagonals, verticals, and connections. Testing results indicate the production and structural efficiency of the developed system.Adviser: George Morcous and Maher K. Tadros