Prestress Level in Stress‐Laminated Timber Bridges

Sarisley, Edward F.; Accorsi, Michael L.

doi:10.1061/(asce)0733-9445(1990)116:11(3003)

Cited by 24 publications

(4 citation statements)

References 2 publications

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“…Through a monotonic test, Quenneville and Dalen 3 demonstrated that pretension in bolts enlarged the initial stiffness of split-ring timber joints besides increasing their lateral load-carrying capacities. Because loss of prestress (stress on wood member due to fastener pretensioning) may occur due to various factors, 4,5 a minimum prestress level of 690 kPa at the time of construction has been recommended. 6 Higher prestress levels (1500 kPa and 3000 kPa) were also applied to the bolts of split-ring joints to improve their structural performances.…”

Section: Introductionmentioning

confidence: 99%

Effects of pretension in bolts on hysteretic responses of moment-carrying timber joints

et al. 2008

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The adoption of a concept similar to the prestressing technique used in laminated wood decks of bridge structures might increase the initial stiffness or ultimate resistance of dowel-type timber joints by applying pretension to their bolts. This study investigated the effect of pretension in bolts on hysteretic responses and ultimate properties of momentcarrying timber joints with steel side plates. A pretension of 20 kN that yielded a prestress level of 1600 kPa or about 90% of the allowable long-term end-bearing strength of spruce species was applied to the bolts of prestressed joints. The superiority of the prestressed joint over the non-pre-stressed joint was proved by very high hysteretic damping, equivalent viscous damping ratio, and cyclic stiffness. At any given rotation level, hysteretic damping reduction and moment resistance decrement due to continuously reversed loads were found to be small because bolt pretensioning minimized the pinching effect. This study showed that the hysteresis loop of the prestressed joint can be obtained by adding the frictional hysteresis loop due to pretension force into the hysteresis loop of the non-pre-stressed joint. Despite a great increase of initial stiffness, only slight increments in ductility coefficient and ultimate moment resistance were found in the prestressed joint.

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Section: Introductionmentioning

confidence: 99%

Effects of pretension in bolts on hysteretic responses of moment-carrying timber joints

et al. 2008

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“…The rate of primary prestressing is not permanent, so follow-up tightening to stabilize these forces is recommended. Experiments to define the development of change of prestressing force in wood mass was conducted by Sarisley and Accorsi (1990)…”

Section: Fig 1: First Transversely Prestressed Bridge In the Czech Rmentioning

confidence: 99%

Prestress losses in spruce timber

Fojtík¹,

Dubovský²,

Kozlová³

et al. 2020

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Prestressing force and its change is one of the key factors that affect wooden constructions, especially those using methods of transverse prestressing. To achieve a description of a prestress force (P) in transversally prestressed wooden constructions a simulated experiment was done. Prestressing force, external temperature, and moisture were measured during 669 days. The main goal of this article was to model the primary losses of the prestress force at the spruce element of the 138 x 138 mm cross-section with the sensor installed. For this purpose, all measurements were statistically analyzed and the period of primary loss was found. During this period the prestress force was decreasing with time mainly and the influence of temperature and moisture could be omitted. Based on this analysis a mathematical model of losses of the prestress force was found as P = 8.538-0.014.day.

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“…While the rheological behavior of wood, such as stress relaxation and creep, has been studied extensively [11,12], in a report on stress relaxation of clamp force associated with bolts or bars in the elastic region, for example, the study related to a stress-laminated timber bridge is described. Extrapolating the results of wood that was tensioned three times in the first 50 days, it was predicted that the stress ratio after 50 years would be 84% [13], though as the authors also noted, the results used for extrapolation were obtained after only 100 days of observation, and did not take long-term losses due to temperature change or decreases in moisture content into account. Hislop [14] reported that bar tension force decreased by 67% during a 3-year monitoring period due to the large decrease in moisture content as well as wood stress relaxation.…”

Section: Introductionmentioning

confidence: 99%

Stress relaxation behavior of wood in the plastic region under indoor conditions

et al. 2019

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The stress relaxation behavior of wood in the plastic region was measured by clamping wood specimens with bolts for up to 5 years under indoor environmental conditions. An initial stress was applied by displacement control, whereby a steel plate or a washer was embedded in the radial direction of the wood. The difference in the stress ratio was small in the plastic region due to the difference in the initial stress level, and the higher the initial stress, the higher the stress that was maintained. By contrast, the clamp force virtually disappeared in the elastic region. The estimated stress ratio after 50 years was 15% in the elastic region and approximately 20-40% in the plastic region. Due to the influence of humidity fluctuation, it was difficult to maintain stress in the elastic region, but it seems to be possible to maintain the stress for a long time using partial plastic embedment with sufficient extra end distance.

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Prestress Level in Stress‐Laminated Timber Bridges

Cited by 24 publications

References 2 publications

Effects of pretension in bolts on hysteretic responses of moment-carrying timber joints

Effects of pretension in bolts on hysteretic responses of moment-carrying timber joints

Prestress losses in spruce timber

Stress relaxation behavior of wood in the plastic region under indoor conditions

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