Earthquake-resistant structures

Earthquake-resistant or aseismic structures are designed to protect buildings to some or greater extent from earthquakes. While no structure can be entirely impervious to earthquake damage, the goal of earthquake engineering is to erect structures that fare better during seismic activity than their conventional counterparts. According to building codes, earthquake-resistant structures are intended to withstand the largest earthquake of a certain probability that is likely to occur at their location. This means the loss of life should be minimized by preventing collapse of the buildings for rare earthquakes while the loss of the functionality should be limited for more frequent ones. To combat earthquake destruction, the only method available to ancient architects was to build their landmark structures to last, often by making them excessively stiff and strong. Currently, there are several design philosophies in earthquake engineering, making use of experimental results, computer si

Modelling reinforced concrete coupling beams designed for low-to-moderate seismic regions Author: Lisa

Lisa Imperatori

Reinforced concrete (RC) coupling beams are often used to transfer and resist the earthquake loads. Coupling beams can improve significantly the stiffness and the strength of the all lateral resistant structure. By performing inelastically they decrease the energy dissipation required by the walls piers granted a better seismic performance. Because of their importance, some experimental and modelling research has been conducted focusing on these important elements. While their behaviour is known to be different from that of conventional beams, in low-to–moderate seismic regions, such as Australia, coupling beams are often designed as an “ordinary beam” with standard longitudinal reinforcements and stirrups. This incorrect procedure may be potentially dangerous and lead to a premature and brittle failure in the event of an earthquake. A finite element modelling approach, which also considers the non-linear behaviour of the beam, is investigated, with the aim of obtaining a realistic and useful model for future research projects and new design procedures. This research presents the preliminary investigations for using finite element modelling to predict the response of coupling beams with ordinary detailing designed for low-to-moderate seismic regions. Some guidelines regarding the use and setting of different parameters of the model are given. A modelling for coupling beams designed for low-to-moderate seismic regions is proposed and compared with experimental model for validation.

2020

Seismic performance of structures incorporating seismic isolation with lead-rubber bearings

Elias Merhi

The emergence of new high-performance materials and equipment, as well as advancements in numerical calculation techniques, have allowed base isolation to take its place among the strategies used by engineers in earthquake resistant design. Despite the enormous advantages of implementing seismic isolation, its applications have so far been limited to critical infrastructures (hospitals, re stations, etc.) located in earthquake-prone areas. The relatively high costs associated with the installation of an isolation system constitute a major constraint when choosing the structural system of a building. In this Master's project, a 4 storey composite-steel administrative building located in Sion (Switzerland) is designed, according to several importance classes, in order to study the relevance of the installation of a base isolation system. Two dierent design methodologies are adopted to determine the dimensions of the foundations and the main load-bearing elements of two buildings, one with a xed-base and the second with a seismic isolation system. The results of the various design procedures clearly indicate that the choice of installing isolating supports is not obvious. Indeed, when the building under study is considered as a critical infrastructure, signicant savings, up to more than 20% in terms of building materials, can be achieved for an isolated structure. On the other hand, for an ordinary structure, the additional costs associated with the installation of isolated supports cannot be oset by savings in construction materials. These results reinforce the perspective that, in the presence of an ordinary building, the traditional xed-base solution remains the most ecient. However, despite its relatively high cost, a base isolated building performs better during a seismic event, with structural demands and damages signicantly mitigated compared to a xed-base building. To compare the responses of the two structural systems, two non-linear models are created on OpenSEES. Two dynamic analyses are then conducted for two groups of 40 seismic records, calibrated according to two characteristic intensities. Based on the results obtained, it is clear that the xed building undergoes higher demands (in deformations and accelerations in particular) than its isolated counterpart. These demands are then used and transformed into a decision variable (in this case, repair costs) through loss analyses conducted on the EarL software. These analyses show that after the occurrence of an earthquake, the repair costs of a conventional building can reach 25 % of the initial construction costs, almost 10 times the value obtained in the case of a base isolated building. This Master's project demonstrates that despite the high initial cost of base isolation technologies, their implementation can not only be amortized through possible material savings, but also, through the reduction of repair costs due to a better performance of the building over its lifecycle.

2022

Seismic performance of structures incorporating seismic isolation with lead-rubber bearings

Elias Merhi

2022