In order to achieve larger spans of timber arch bridges, glulam massive timber sections must be spliced on-site by moment resisting and rotationally stiff joints. In this paper, a novel timber splice connection utilizing long threaded rods and grout-filled couplers is presented. Flexural characteristics of the splice joint were investigated by full-scale experimental tests and 3D finite element models. An analytical model is proposed for determining the moment capacity and the rotational stiffness of the splice connection. The experimentally measured efficiency of the splice connection with regard to moment capacity and rotational stiffness was 69 % and 66 %, respectively.

Long threaded rods have recently been widely used as a reinforcement of glued laminated timber in perpendicular to the grain direction. The recent research has thus focused mainly on the withdrawal properties of the threaded rods in the axial direction. Utilizing their large withdrawal stiffness and strength, the threaded rods can also effectively be used as connectors in moment resisting timber joints. Yet, in joints, the threaded rods are often imposed to a non-axial loading, due to inclination of the rod axis to the grain as well as loading direction different from the rod axis. No design models are currently available for the combined axial and lateral loading of the threaded rods. In the present work, the effects of the rod-to-grain and load-to-rod angles on capacity and stiffness of the threaded rods are investigated by use of experiments and finite element models. Based on those, analytical expressions for determining stiffness and capacity of axially and laterally loaded threaded rods are proposed, intended as a basis for practical joint design. Furthermore, effect of various boundary conditions applied at the rod-ends is studied.

Large spans of modern timber bridges can be achieved by use of glulam arches with network hanger configuration. Since transportation and production limit the length of timber elements, the glulam arches must be spliced on bridge site.However, it is difficult to obtain practical moment resisting on-site splicing of massive glulam elements featuring flexural rigidity by the available timber splicing techniques. Consequently, the arches are often designed as trusses containing a large number of connections, which are costly and present a risk of decay development. In the present paper, a novel splicing technique suitable for large massive timber sections is presented. The flexural rigidity of the joint is obtained by the utilisation of long threaded rods having large withdrawal stiffness. Fast and easy on-site assembly is facilitated by mechanical coupling of the rods. The rods are oriented with a small inclination to grain, which prevents potential development of shrinkage cracks along the rods. Experimental and numerical methods were used to investigate the flexural joint characteristics. The joint prototypes featured large rotational stiffness without initial slip. As a basis for practical joint design, analytical relations are proposed for estimating the rotational stiffness, the moment capacity and the capacity under combined bending and normal force.

Timber has historically played an important role as a building material for bridge construction both in Norway and Sweden. Although a decline was seen due to rise of other competing materials such as steel and concrete over the past century, it has regained popularity in recent decades due to pioneer developments in timber engineering including glued laminated timber and stress-laminated timber decks. There has been a specific focus on development of timber bridges in the Nordic countries after a Nordic Timber Bridge Project was started in 1994. Hundreds of bridges have been constructed throughout these countries including both pedestrian and heavy traffic bridges thereafter. Although the information about the number and type of these bridges can be found on several public administration sources, the information is very scattered and difficult to interpret. In the current study, several sources and databases were used to collect data on timber bridges in Norway and Sweden. Based on the collected data, a comparative view of the development of timber bridges in the two countries is presented with main focus on modern timber bridges built after year 2000. Detailed statistics are included in the study regarding year of construction, type of traffic, bridge types and bridge lengths. Discussions are presented in the end with focus on current trends and possible outlooks for use of timber bridges.