Precast Prestressed Concrete Truss-Girder for Roof Applications

Abstract

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 48 m (160 ft) without intermediate supports. The proposed design is easy to produce and has lower construction and maintenance costs than steel trusses. The truss consists of two segments that are formed using standard bridge girder forms with block-outs in the web which result in having diagonals and vertical members and reduces girder weight. The two segments are then connected using a wet joint and post-tensioned longitudinally to form a crowned truss. The proposed design optimizes the truss-girder member locations, cross-sections, and material use. A 9 m (30 ft) long truss specimen is constructed using self-consolidated concrete to investigate the constructability and structural capacity of the proposed design. A finite element analysis of the specimen is conducted to investigate stresses at truss diagonals, verticals, and connections. Testing results indicate the production and structural efficiency of the developed system.

Post-tensioned concreting: its suitability for and acceptability in Sri Lanka

“…Costs involved with facades can be reduced because of reduced thicknesses (Engr-Gana et al , 2015). Waterproof slabs : If designed carefully with the required quality and workmanship, PS and PT concrete slabs would be crack-free and thus waterproof (Rogowsky and Marti, 1991; Samir, 2013). Materials saving : They can resist the same load as conventional concrete with a lower amount of concrete and reinforcements (Corven Engineering Inc, 2002).…”

“…Waterproof slabs : If designed carefully with the required quality and workmanship, PS and PT concrete slabs would be crack-free and thus waterproof (Rogowsky and Marti, 1991; Samir, 2013).…”

Performance of quadrilateral perforated prestressed concrete rafters

“…The construction of a long-span rafter is incredibly difficult to produce, since concrete is inefficient in tensile strength, it is necessary to add prestressing steel to resist the applied load and span reinforcement with ordinary steel only could not be achieved (Samir, 2013).…”

Prestress Losses in Concrete Rafters with Openings

“…The link structural elements (posts) between the upper and the lower chords of the rafter beam have many advantages such as avoiding Vierendeel truss to prevent shear failure and allowing a beam to enhance its bending capacity and ductility [11]. The fact that concrete is not efficient in resisting tensile stress makes very difficult reaching a long span beam in design, so the addition of prestressing reinforcements has become necessary to reach span lengths which cannot be reached by using ordinary reinforcements [12][13]. To estimate losses such as elastic shortening, creep, shrinkage, and relaxation in beams, the empirical methods recommended by the codes are only applicable to prismatic beams.…”