József Simon

Discrete Element Analysis of the Minimum Thickness of Oval Masonry Domes

ABSTRACT This study focuses on domes the ground plan of which, instead of the more common circular shape, is an oval, and aims at finding the minimally necessary uniform wall thickness for domes of different geometries loaded by their selfweight. The discrete element code 3DEC was applied because of its capability of simulating the collapse mechanisms of masonry structures. Results on the minimal wall thickness, corresponding masonry volume and failure mechanisms for different dome geometries are presented. Three ranges of the friction coefficient were found. For very low frictional resistance collapse happens with pure frictional sliding, for any arbitrarily large wall thickness. In the range of relatively high (i.e., realistic) friction coefficients the structure collapses without any sliding if the wall is not sufficiently thick, and in the observed range of the friction coefficient the necessary wall thickness is nearly insensitive to its value (collapse initiates with hinging cracks only). Between the two domains an intermediate behavior was found: combined cracking and sliding collapse modes occur for insufficient wall thickness, and the minimal thickness strongly depends on the friction coefficient. The critical and transitional friction coefficients separating the failure modes were determined for different eccentricities of the groundplan.

Seismic Reliability Assessment of Typical Road Bridges in Hungary

ABSTRACT Prior to modern seismic codes, several road bridges were not designed for earthquakes in many moderate seismic regions. The seismic performance of these bridges is questionable. A portfolio of 30 non-seismically designed bridges is compiled for seismic reliability assessment. Fragility analysis is conducted, and the reliability of each structure is determined considering typical moderate seismic areas. The study shows that slab and multi-girder bridges with elastomeric bearings perform worse, whereas girder bridges with conventional bearings and multi-girder bridges with monolithic joints have better behavior. It is also shown that seismic design per Eurocode 8 leads to a reliability index of ~2.

Seismic fragility assessment of integral precast multi-span bridges in areas of moderate seismicity

In lack of seismic provisions in the pre-Eurocode ages, most of the existing Hungarian bridges were not designed for seismic actions, therefore their seismic performance is questionable. The most commonly used structural type in highway construction is the integral precast multi-girder bridge. These bridges are typically constructed as continuous multi-support systems with monolithic joints at each support, thus their behavior may be significantly different from those applying simply supported beams and conventional bearings. A parametric fragility analysis of a wide range of different layouts is carried out using detailed and advanced non-linear numerical models. The results indicate that the abutment joints are highly vulnerable and piers are also critical for longer bridges. The study implies that without seismic design, integral precast multi-girder bridges are highly susceptible to pier shear failure, the probability of collapse is relatively high. The results also provide a solid basis for retrofit planning as well as for development of design concepts of newly built structures in moderate seismic zones.