Abstract
The load resisting capacity of structural members will decrease when they are subjected to long-term sustained load. Such phenomenon is widely known as the duration of load effect, which is mainly caused by the damage accumulation in the material. The deterioration mechanism of the material is a typical stochastic process which is influenced by a large variety of parameters involving complex physical and chemical process. Although classical models have been proposed to evaluate the duration of load effect, it is nearly impossible to quantify the influence of various parameters and to achieve an accurate estimation. To optimize the combination of complexity and goodness-of-fit, a neural network model is proposed in this paper to evaluate the duration of load effect in wood structural members. Taking individual uncertainties into consideration, the proposed model treats the damage in wood as a Markov process and can estimate the residual strength distribution of the investigated wood structural members under long-term sustained load. The coefficient of determination reaches above 95% under sustained loading scenario, and it shows good adaptability across different wood properties. Moreover, the model can be adapted to continuously varied loading scenarios with a 98% coefficient of determination. This research aims to provide a useful and straightforward tool for accurately predicting the duration of load effect in wood structural members, and the proposed algorithm can be easily modified to deal with similar engineering problems for other construction materials.
Highlights
Duration of load effect is a widespread phenomenon that structural members will experience a decrease of load resisting capacity under long-term sustained load
This phenomenon is mainly accounted for the damage accumulation in the material
Many long-term experiments for beams or columns made of different construction materials have been performed to reveal such phenomenon
Summary
Duration of load effect is a widespread phenomenon that structural members will experience a decrease of load resisting capacity under long-term sustained load. This phenomenon is mainly accounted for the damage accumulation in the material. Many long-term experiments for beams or columns made of different construction materials have been performed to reveal such phenomenon. The long-term load lowers the ultimate strength of the concrete-filled hollow structural steel tube columns [2]. The Madison curve, which is plotted according to the United States forest products laboratory’s long-term experiment for timber beams, shows that the strength of timber beams after 10 year’s sustained loading is only 62% of the short-term strength [3]. Some classical models are proposed to simulate the time-dependent behavior of structural members [4]–[6]
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