Special Issue: On the Seismic Behavior of Masonry Structures: Recent Advances (Selection of expanded papers presented at the 18th International Brick and Block Masonry Conference IB2MaC held in Birmingham, UK (July 21 -24, 2024))

This Special Issue is aimed at collecting thoroughly revised and expanded versions of a selected blend of papers presented at the last International Brick and Block Masonry Conference 18th IB2MaC held in Birmingham (UK), 21 - 24 July 2024.

IB2MaC was born in 1967 in Austin (Texas, USA), and to date it has been organized 18 times, in several regions around the world. The 18th edition returned to UK after 54 years, co-chaired by Prof. Bahman Ghiassi (University of Birmingham, UK) and Prof. Gabriele Milani (Politecnico di Milano). This Conference is undoubtedly one of the most important international events for the masonry community and takes place every four years.

Masonry, whether of stone or brick, is probably one of the oldest building materials still in use nowadays. In most countries, masonry buildings represent great part of the architectural heritage, with masonry continuing to be much used in modern construction industry today.

Despite it having been used for millennia, still masonry involves several mechanical and structural challenges towards the improvement of the integrity and longevity of buildings. Understanding and facing with such issues is essential for both preservation and innovation in masonry construction.

Mechanically, masonry is characterized by its fairly good strength in compression, its limited tensile resistance and by the typical frictional and quasi cohesion-less shear behavior. The compressive strength basically relies on the quality of materials and workmanship, ensuring uniform load distribution and preventing stress concentrations and subsequent cracking. Shear strength is significantly lower and turns out to be strongly dependent on the level of vertical precompression, the geometric features of the structural elements, the bond between mortar and masonry units and the arrangement of the blocks. Weak or deteriorated joints reduce the strength, making structures susceptible to lateral forces induced by wind, earthquakes, or extreme events in general, which are nowadays becoming more and more frequent because of the climate change. Similarly, masonry's low tensile strength and its fragile nature under positive normal stresses makes it prone to cracking in seismic area, frequently necessitating reinforcement. Masonry structures are notably vulnerable to seismic forces due to their brittle nature and seismic retrofitting, realized using either traditional or innovative techniques, proved to increase the resilience. Understanding such mechanical and structural problems is not an easy task, but is vital for the effective design and maintenance, aiming at a durability improvement. Advances in materials and engineering practices continue to evolve, providing new solutions to these longstanding challenges, and the implementation of new techniques still allow to build structures and infrastructures in masonry, giving the possibility to achieve that structural safety required by modern seismic codes of practice.

The challenges imposed by climate change and the intrinsic vulnerability of the built stock represent a societal priority that provide additional momentum to the most advanced research in the field, stimulating the need for a continuous advancement of the knowledge.

An open challenge is also to propose a consistent seismic design for developing countries, were the difficulties in the access of advanced technologies, resources and knowledge lead to build new masonry structures with poor technologies and without the necessary strengthening to carry seismic accelerations. Conversely, for industrialized countries like USA, EU and Japan open topics are still the mitigation of the seismic vulnerability of the existing/historical built stock and to increase the performance of the new ones.

The Special Issue is aimed at collecting original works dealing with numerical, experimental and analytical approaches of single structural elements and entire masonry structures subjected to horizontal loads/earthquake actions. Paramount is the structural safety assessment against earthquakes, whereas interesting extensions can be related to structural analyses/models/experimentation of reinforced masonry, even with innovative materials like FRP and FRCM. Technical considerations, particularly suitable for practitioners and critical comparisons with design recommendations are also included, basing on case studies.