Mechanical Numerical Analysis Research Articles

Effects of core air gaps and steel inserts on thermomechanical response of GFRP-balsa sandwich panels subjected to fire

Composite sandwich panels composed of a balsa core and glass fiber-reinforced polymer (GFRP) face sheets may offer attractive applications for building slabs and bridge decks. Such composite panels may contain air-filled gaps (caused by initial defects or damage) or through-thickness cracks and different types of metallic inserts (used for facilities and piping systems) in the balsa core. The fire performance of sandwich panels can be reduced by the local heating effects inside such air gaps and inserts. The thermomechanical response of GFRP-balsa sandwich panels comprising through-thickness air gaps or steel inserts, subjected to combined mechanical load and one-sided ISO 834 fire, were thus investigated by fire experiments and uncoupled thermal and mechanical numerical analysis. The results demonstrated that the shear resistance reduction of the core is not critical, while the moment resistance reduction can lead to panel failure. The propagation of a transverse tensile crack in the balsa core produced a similar moment resistance reduction to an air gap or steel insert. The air gaps and steel inserts charred the inner core zones and heated the cold face sheet above, leading to face wrinkling. The effects of air gaps and steel inserts remained local. Depending on their location in a panel, they may thus not exhibit significant effects on the whole structure. If they are placed on critical load paths however, e.g. in the vicinity of supports, they may cause collapse of the whole structure. Since the extension of transverse tensile cracks is not limited, they may also lead to an overall collapse.

The impact of the cultural value on the seismic vulnerability of a historical building

Romania is a country located in Eastern Europe. It has two important seismic areas, Vrancea and Banat. Vrancea seismic region is located close to the biggest city of Romania, Bucharest, which is also the capital, while Banat seismic area is located in the western part of the country. The most important city from the Banat area is Timisoara, which was also elected to be the European Capital of Culture 2021. Beside the general seismicity of the area, which is characterised by shallow earthquakes of crustal type, Timisoara city presents also two seismic faults that cross the western part of the city. The peak ground acceleration is considered to be ag=0.20g, while the maximum recorded magnitude was MW=5.6-5.8. The paper is a part of a larger research work which aims to assess the seismic vulnerability of the historical buildings in Timisoara city and their specific failure mechanisms, through both empirical simplified and mechanical numerical analysis. This study presents a new methodology that was previously proposed by the authors in their work and that considers also the influence of the cultural value in the process of assessing the seismic vulnerability. The consideration of the architectural, artistic, urbanistic and social elements can considerably influence the seismic vulnerability of a building. The highest the cultural value, the highest the need for rehabilitation work. The study is focused on one of the most important historical buildings of the city, Elite’s Palace, and compares the results of the empirical seismic vulnerability assessment with and without considering the cultural value. This kind of research could provide valuable information for the local authorities and could represent the base of a prioritization list for the future rehabilitation work.

Mechanical Numerical Analysis for L-Shape Traffic Signs Bar with Variable Cross-Section

L-shape traffic sign bar is composed of a stand column and a cantilever bar using bolted connection. The cross-section of stand column and a cantilever bar is closed thin wall with regular octagon and their cross sectional area is variable along axial line. The finite element simulation analysis for the bar is done under gravities and wind loads. Three-dimensional finite element model of bar is set up and stress field and displacement field is given under different load and their combination. Stress and displacement values of key parts are extracted and compared with theoretical calculation. Indicates that the theoretical calculation and finite element calculation is correct.