This study presents a novel approach to simulating the fatigue stress spectra of short-to medium-span bridges under stochastic and dynamic traffic loads. The stochastic traffic load is simulated based on the weigh-in-motion (WIM) measurements of a heavy-duty highway bridge in China, and the dynamic effects are modeled using a vehicle-bridge coupled vibration system. An interpolation response surface method (RSM) is used to approximate the effective stress ranges of a bridge with respect to road roughness conditions, gross vehicle weights, vehicle configurations, and driving speeds. The RSM provides a platform for an efficient spectrum simulation of bridges under stochastic and dynamic traffic loads. A case study of a simply supported T-girder bridge demonstrates the effectiveness and efficiency of the proposed approach. The proposed computational framework provides an effective approach for simulating the fatigue stress spectra for short-to medium-span bridges with WIM data.
Fatigue damage accumulation is a critical factor resulting in the failure of prestressed concrete (PC) bridges. The fatigue damage is usually caused by the coupled effect of cyclic vehicle loading and environmental corrosion. This study investigated probabilistic fatigue damage on aging PC bridges considering both stochastic traffic loading and corrosion. A stochastic traffic model was derived based on long-term monitoring data aiming to simulate fatigue stress spectra of critical rebar. The effect of cracks on the fatigue stress spectra was investigated in order to model the fatigue stress state more realistically. A three-stage traffic growth model was established based on traffic volume histories of three highways in China. A fatigue limit state function considering traffic growth and corrosion effect was deduced for fatigue reliability assessment of PC bridges. Numerical results show that the stress amplitude of rebar considering cracks is 1.53 times greater than the rebar with no-cracks, resulting in a decrease of fatigue life by 68 years. In addition, the three-stage traffic growth models lead to 25 years shorter fatigue life than the one considering a linear traffic growth model. Finally, the corrosion effect results in a fatigue life of 44 years. The numerical results provide a theoretical basis for fatigue life estimation and maintenance of aging PC bridges.
The data link of construction monitoring of steel structures is usually long, complicated and with huge amount of data. Because of the influences of various factors during construction process, sometimes it is inevitable to cause partial monitoring data missing or interrupt of the data link which may affect the real-time control of construction process, even the structural safety assessment during construction. Based on the generating mechanism and characteristics of the missing data discovered from the statistic of actual construction monitoring of steel structures, this paper classifies the missing data into three types for developing new data processing methods. According to the characteristics of the different types of missing data, several compensating methods of the missing data are proposed respectively in this paper by regression analysis based on the principle of least square. The proposed methods are adopted to process the missing monitoring data of the steel structure construction of Art Gallery of Datong and the Circle of Life of Shenyang for verification. The estimated values are compared with the measured data. The numerical results show that the proposed missing data processing methods are effective and practical.
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