ICE - Institution of Civil Engineers - Virtual Library

This paper describes post-tensioned timber alternative designs for a six-storey office building in New Zealand. The building has long-span timber–concrete composite floors supported on laminated veneer lumber beams, columns and walls. Lateral loads are resisted with moment-resisting post-tensioned timber frames in one direction and post-tensioned cantilever timber walls in the other direction. This paper compares the time and cost of timber construction with the concrete building actually being constructed. Construction times of the timber and concrete buildings are found to be almost identical. The cost of the timber alternative is approximately 6% more than concrete or steel designs. This paper demonstrates the opportunity for post-tensioned timber to compete with concrete and steel for multi-storey long-span office buildings, providing a more sustainable alternative.

Structural fire design of timber structures can be performed using Eurocode 5 parts 1 and 2 that provides two types of design methodologies: simplified and advanced. As the base parameters for the methods are not the same it is important to assess their behaviour under different conditions. The aim of this paper is to compare the different design approaches and verify their coherence for the design of columns. Several parametric studies comparing the different design methods were performed. Factors such as timber class, member cross-section size or slenderness of column were investigated and a comparison of the simplified and advanced methods was carried out. Some inconsistencies were found between the simplified and the advanced calculation methods. Eurocode 5 design methods should be improved and become more coherent. A proposal for improved parameters is made in order to improve the coherence of the different design methods.

Dense tropical hardwoods are commonly used in maritime and river structures because they have the necessary strength and display some required durability including good resistance to abrasion and to attack by marine borers. Owing to environmental concerns about the sustainability of forest products, responsible procurement regimes now require that tropical hardwoods are certified from a sustainable and legal origin. However, timber is generally selected from a restricted number of species with proven track records of in-service performance, for example greenheart and ekki. There are concerns that over-reliance on a small number of timber species is exerting disproportionate environmental pressure on these species in their forests of origin and could encourage removal of timber that is not produced legally or sustainably. The present research sought to find alternative lesser-used timber species that are commercially available, can be legally and sustainably sourced and would display appropriate performance for maritime and riverine applications. A desk study first established a long list of potential lesser-used timber species. These were screened for resistance to attack by maritime gribble and to abrasion. The resulting shortlist of candidate species has been screened for resistance to shipworm through in situ exposure at a site known for its aggressive shipworm population. In addition to these results, the proposed approach to assess the actual full-scale performance of lesser-used timber species is introduced

This paper describes the structural project for a timber cantilevered walkway truss recently built in Vitoria-Gasteiz, Spain, as a part of a nature education centre. This study analyses the structural aspects of this walkway, designed as a cantilevered truss with a span of 19·2 m and a backspan of around 10 m between the two lines of columns of the structure. The structure has been built mainly using laminated veneered lumber (LVL) for the struts and chords and steel bars for the diagonals. The critical sections, at the two lines of columns, have been built using frames made of steel and reinforced concrete. Due to the critical tension force that appears at the foundation, permanent anchors were used for transferring this force to the ground. Wind loading has also led to anchoring the two pairs of concrete columns. The joints in the timber trusses were designed using dowels with steel gusset plates and toothed plates. The singular structure of this construction makes it similar in size to the German Pavilion recently built in Hannover, which is considered to be the biggest timber cantilevered roof in Europe. Although the structural problem solved in this construction is not exactly the same (the snow load is not critical whereas in this example the live load is the key factor), some important general remarks can be learnt from this case study.

Historic buildings are part of our built environment. Many of these buildings are important icons of our past and form part of our heritage and culture. They also provide excellent opportunities for reuse and development and can serve as the focal point for the regeneration of many run down, post-industrial areas. We should all be recycling our newspapers, plastic and glass bottles and should be composting our organic waste as part of the Green Revolution to reduce the amount we, as a society, waste. What better act of environmental awareness is there than reusing our historic buildings and the materials within? A holistic approach to the investigation of historic timber using non-destructive techniques to inspect and examine timber in situ for strength-reducing defects combined with repairs undertaken with the minimum of interventions, where practicable, can facilitate the reuse of original structural timber and can contribute to the ‘recycling’ of historic buildings. Moreover, the ‘recycling’ of such buildings and the materials therein can result in the construction industry exerting less pressure on our natural resources and reducing its carbon footprint.

This paper reports on research to optimise the design and construction of various forms of stress-laminated timber bridges. Forty bridges, up to 24 m span, and over 60 deck panels have been built and monitored over the last 5 years. A research programme at Napier University has complemented the construction and, through a series of dynamic and static load tests, has helped develop better construction methods and stronger structures. The overall aim of this research programme has been to develop structural uses for low-grade, UK-grown timber and it has been shown that using timber in compression is an extremely effective technique for arch bridges. These bridges, on public roads, can help increase public confidence in timber as a viable primary structural material. This paper reports the development of factory-produced, timber-laminated modules for lorry bridges and footbridges. It explains the different fixings, spans, widths and load tests and summarises the conclusions. It finishes by showing the lowest cost, stress-laminated flat lorry bridge and reports the details of cyclic load tests for the development of timber arch bridges for heavy lorry traffic.