Society for Earthquake and Civil Engineering Dynamics
SECED 2015 was a two-day conference on Earthquake and Civil Engineering Dynamics that took place on 9-10th July 2015 at Homerton College, Cambridge.
This was the first major conference to be held in the UK on this topic since SECED hosted the 2002 European Conference on Earthquake Engineering in London.
The conference brought together experts from a broad range of disciplines, including structural engineering, nuclear engineering, seismology, geology, geotechnical engineering, urban development, social sciences, business and insurance; all focused on risk, mitigation and recovery.
SECED 2015 featured the following keynote speakers (affiliations correct at the time of the conference):
Long-duration ground motions were recorded recently during the 2010 Muale earthquake in Chile and the 2011 Tohoku earthquake in Japan. Both earthquakes caused significant structural damage that was reported by different research teams who inspected numerous buildings after each earthquake. One of the most observed failure modes as reported by researchers and professional engineers was the rupture of reinforcing bars in reinforced concrete (R.C.) members due to earthquake-induced low-cycle fatigue. The long duration of both earthquakes induced a large number of loading cycles on the affected buildings, which led to significant damage especially at locations where high strains were expected to occur. This paper presents preliminary results of a study to estimate the low-cycle fatigue damage in R.C. frame buildings when they are subjected to long-duration earthquakes. A 20-story and a 6-story case study buildings representing structural configurations with different dynamic characteristics were selected for investigation through nonlinear time history analysis. Both buildings are existing instrumented buildings that experienced several earthquakes during their service life and have recorded responses that were used to verify the analysis models. The models for both buildings were analysed under long-duration ground motions to assess the low-cycle fatigue damage within the R.C. members.
Based on the results from the nonlinear models, detailed fatigue analysis was conducted using the strain time histories obtained at each critical location within the buildings. Due to the irregularity of the strain histories, the rain-flow counting method was used to convert the histories into equivalent number of cycles of certain strain amplitudes. The fatigue life relationships for reinforcing bars were found in the literature based on experiments conducted by several researchers on different grades and sizes of reinforcing steel. The Palmgren-Miner damage rule was used to estimate the reduction in the fatigue life due to the applied ground motions in both buildings using those fatigue life relationships.
The preliminary findings of this study showed significant reduction in the fatigue life of reinforcing bars due to long-duration earthquakes that could increase the damage potential in R.C. frame buildings. It was also found that the dynamic characteristics of the building affect the number of cycles, which controls the low-cycle fatigue damage.