Yoshiki Ikeda

Protection from static and dynamic actions is an urgent matter for masonry buildings, which constitute the majority of the world’s architectural heritage. For this reason, the search for best strategies to analyse the mechanical responses of such structures under both dead and seismic loads has been at the centre of a vivid debate within the scientific community for decades. Although many different approaches and computational methods have been proposed in the literature over the years, most of them make reference to no-tension materials, starting from the pioneering work by Heyman in the framework of limit analysis. However, implementing the hypothesis of masonry walls made by rigid blocks interacting through no-tension interfaces often leads to inconsistent results due to possible interpenetrating elements. In dynamic simulations, undesired blocks’ interpenetration forces algorithms to continuously check the compatibility and to eventually stop and restart the analysis with somehow arbitrary initial conditions. By introducing well-established hyperelastic and friction laws at bricks’ interfaces, we propose a heretical strategy that overcomes some difficulties of the above-mentioned approaches, recovering physical consistency and avoiding any interpenetrations.

For two adjacent buildings connected by a joint damper, an inverse problem is formulated based on the pole allocation method in control theory. The structural system is simplified as a two‐degrees‐of‐freedom (2‐DOF) lumped‐mass damped shear model. The unified governing equation, which expresses the relationship between an assigned control target and the structural parameters for an earthquake‐resistant building, seismically isolated building, or passively controlled building, is extended to structural control using a joint damper. The introduced equation automatically constrains the variations in the structural parameters under the assigned modal properties. The integration of the pole allocation method and fixed‐point theory directly estimates the additional damping effect on the target buildings from the optimum capacity of the joint damper, which improves the trial‐and‐error steps at the preliminary design stage. The past fixed‐point theories do not provide the additional damping effect but the optimum damping coefficient of the joint damper. The present study directly links the additional damping with the damping of the joint damper. Numerical examples are used to verify the theoretical integration using a 20‐DOF building model wherein two 10‐DOF models are connected by a joint damper between the top lumped masses.

The applicability of the proposed dynamic response model for buildings is investigated using shaking‐table tests with a four‐storey steel specimen. This approach derives the equation of motion for a multi‐degree‐of‐freedom linear building based on microtremor measurements. Under a linear assumption, the equation can estimate the seismic response accelerations, velocities, and displacements at microtremor sensor locations without the need for information about the mass, damping, stiffness matrices or need for structural design documents to estimate peak responses that are linked with seismic damages of structural and non‐structural components. The modelling is unconstrained by structural shape, composition of frames, connections of structural members, or the assumption of a rigid floor. In comparison to the previous methods assuming simple/regular building shape with standard/typical rigid floor, the proposed model is applicable to large‐scale low‐rise buildings with irregular shapes, flat expanses, and open spaces such as large atria and skylights as well. The applicability study considers two practical scenarios: natural frequencies and damping ratios based on microtremors that can be updated by an earthquake and a standard assumption for structural design. The prediction accuracy is best when the participation vector for seismic input is obtained from sensors located on the upper floors; the structure mostly exhibits elastic response; a modal system identification is applied to the seismic measurement; and local damage does not affect the global seismic response of the structure. The reason is that this method assumes that identified mode shapes do not change due to the occurrence of an earthquake.