Influence of the Structure of Lattice Beams on Their Strength Properties.

Radosław Mirski,Maciej Marecki,Dorota Dziurka,Tomasz Rogoziński,Łukasz Matwiej,Bartosz Pałubicki,Monika Chuda-Kowalska

doi:10.3390/ma14195765

Radosław Mirski, Maciej Marecki + Show 5 more

Open Access

https://doi.org/10.3390/ma14195765

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Abstract

This paper presents the strength properties of wooden trusses. The proposed solutions may constitute an alternative to currently produced trusses, in cases when posts and cross braces are joined with flanges using punched metal plate fasteners. Glued carpentry joints, although requiring a more complicated manufacturing process, on the one hand promote a more rational utilisation of available structural timber resources, while on the other hand they restrict the use of metal fasteners. The results of the conducted analyses show that the proposed solutions at the current stage of research are characterised by an approx. 30% lower static bending strength compared to trusses manufactured using punched metal plate fasteners. However, these solutions make it possible to produce trusses with load-bearing capacities comparable to that of structural timber of grade C24 and stiffness slightly higher than that of lattice beams manufactured using punched metal plate fasteners. The strength of wooden trusses manufactured in the laboratory ranged from nearly 20 N/mm2 to over 32 N/mm2. Thus, satisfactory primary values for further work were obtained.

Highlights

Wooden trusses are an example of structural elements used in the construction industry—both in wooden and brick structures [1,2,3,4,5]
The presented lattice beams are denoted as UPPx: UPP1—mortise and tenon joint, UPP2—finger joint and UPP3—classified mortise and tenon design
It results from these analyses that it is feasible to manufacture lattice beams with parallel chords to serve as truss beams, when punched metal plate fasteners joining chords with diagonals are replaced by carpentry joints

Summary

Introduction

Wooden trusses are an example of structural elements used in the construction industry—both in wooden and brick structures [1,2,3,4,5]. A significant advantage of timber is connected with its strength, dependent only on the size of the destroyed cross-section and the load level, rather than the reduction in load-bearing capacity related to the increase in temperature [34,35,36] In this approach, all steel elements in the wooden structure are typically considered to be more sensitive than timber itself. The results from extensive studies by Sultan [37] show that flat wooden lattice beams constituting the ceiling structure are characterised by comparable fire resistance, irrespective of the method, with which diagonals and chords are joined This researcher investigated two types of trusses, one with punched metal plate fasteners and the other being finger-jointed trusses (Figure 1). FfFriaigggumureern5e.tF5or.foFmthretohlmeowletfehtr:efbinelelgtfeUtr:jPofiPinn1t—g(bec)rh; otjeorndionontf—tjoruicnshts—,oUrddPiaPgo2of(nata)r;lutemsnseo,mnUbjoePirn,Ptt—2enc(ohano);rjdotieonnfttofrrunasgsjmo, tieennntto—nofjcothihnoet rd of truss, tenon cjrooisnstbofrnaegUmPPe1n(tco),ftetnhoenljoowinte—r dbiealgtoUnaPl Pm1em(bb)e;r,tetennoon jjooiinnt tf—ragdmiaengtoonfathl emcreomssbeonr,etUenPPo3n(djo).int fragment of the crossbone UPP1 (c), tenon joint—diagonal member, tenon joint fragment of the crossbone UPP3 (d)

Calculation of internal axial forces in truss members

Calculation of Internal Axial Forces in Truss Members

Lattice Beam as a Solid Beam

Analysis of Laboratory Testing Results

Conclusions