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Though often overlooked, the impact of seismic transient ground deformation on natural gas (NG) pipes can be highly adverse. Particularly, pipe elbows may undergo excessive in-plane bending demand and buckling. In this paper, a critical scenario of a pipe coupling two industrial structures typically found in an NG processing plant is studied. High strain and cross-sectional ovalization on the elbows are probable during an earthquake due to the out-of-phase oscillation of the two structures imposing asynchronous displacement demands at the two pipe-ends. A parametric study was first performed to investigate various structure-pipe-structure configurations which increase seismic demands to pipe elbows. Simultaneous mobilisation of divergent oscillation between two supporting structures at the low-frequency range, a lower pipe-structure stiffness ratio, a shorter length of straight pipe segments in the linking pipe element and a higher pipe internal pressure have led to the onset of critical strain demands in pipe elbows. To validate this observation, an experimental campaign was developed where a full-scale linking pipe element was physically tested by means of hybrid simulation (HS). The study shows that the seismic interaction of the structures coupled with the pipe is non-negligible and can be even critical for the integrity of the coupling pipe. The finding depends on the structural system’s dynamic and geometrical properties as well the frequency content of the earthquake excitation.

The dynamic increase factor (DIF) has been widely used to consider the rate effect in the analysis and design of concrete structures that are subject to impact loads. A variety of DIFs have been proposed by many researchers based on the results of dynamic material tests such as the split Hopkinson pressure bar (SHPB) test. These DIFs have been adopted in authoritative design guidelines and model codes such as the ACI 349–13, ACI 370R-14, fib MC2010, and UFC 3-340-02. However, previous studies did not properly consider the strain acceleration and the geometrical characteristics of the test specimens that cause the axial and radial inertia forces which influence the test results. For this reason, predictions can become non conservative when these DIFs are used in the analysis and design of concrete structures that are subject to impact or impulsive loads. In this study, to overcome the limitations of existing DIFs, a new concrete DIF that excludes inertia effects by considering the strain acceleration and geometry of the specimens has been proposed based on SHPB test results. The proposed DIF was numerically validated using finite element analyses. Compared with other existing DIFs, the results show improved predictions of the enhancement of the concrete compressive strength due to rate effect.

Most of existing steel multi-storey frames in Europe have been designed before the introduction of modern seismic design provisions, hence they often exhibit low performance under earthquake loads due to their low lateral resistance and energy dissipation capacity. In addition, such structures often include rigid and brittle masonry infill walls that highly influence their lateral response and distribution of damage pattern. However, current procedures for the assessment of existing steel buildings in Europe, included in the Eurocode 8 – Part 3 (EC8–3), do not provide adequate guidance for the assessment of ‘weak’ steel frame with masonry infill walls. Moreover, most of available modelling approaches of masonry infills formerly developed for reinforced concrete (RC) structures do not properly represent the behaviour of infill walls in steel frames. An improved numerical has to be provided to satisfactorily mimic infill walls' behaviour in steel moment frames. To this end, an experimental and theoretical study was carried out within the framework of HITFRAMES (i.e., HybrId Testing of an Existing Steel Frame with Infills under Multiple EarthquakeS) SERA project. This paper firstly presents the limitations of current EC8–3 by conducting a code-based assessment on a case study steel moment frame using pushover analysis. Three different single strut models, widely used for simulating the presence of masonry infills in RC structures, are considered for the numerical analyses. The paper also presents the results of pseudo-dynamic (PsD) tests performed on a large-scale 3D steel frame with masonry infills. The capability of the different masonry infill models is successively evaluated by comparisons between numerical and experimental results. On the basis of the obtained results, recommendations on how to potentially improve the single strut model for masonry infills surrounded by steel frames are also provided.

Using anchors made of fibre reinforced polymers (FRP) is an increasingly accepted method to delay the delamination of FRP sheets from the concrete surface and to enhance the capacity of FRP strengthened concrete structures. For many applications, FRP anchors are primarily loaded in shear. When used for seismic retrofitting schemes, the anchors are subjected to cyclic loads which may lead to premature fatigue failure. To date, however, shear strength of FRP anchors has experienced much less attention than their tension resistance. This paper documents tests on isolated FRP anchors which were conducted to determine the seismic shear capacity of FRP anchors and to propose design rules. To this end, a test setup was developed which allows direct and reverse loading of FRP anchors.

A critical performance aspect of FRP retrofitted concrete elements is the bonding of the FRP sheet to the concrete surface. In general, the performance is limited by the debonding of the loaded FRP sheets from the concrete surface. One method to delay debonding and enhance the capacity is the use of FRP anchors which interlock the FRP sheet to the concrete body. FRP anchors are made of rolled FRP fibres epoxied into in predrilled boreholes. There are a considerable number of studies on FRP strengthening methods available, and also FRP anchors attract more attention of the research community recently. However, to date FRP anchors were tested in a system together with the FRP sheet attached to the concrete, inhibiting the development of general design models. Moreover, the anchor behaviour was never tested for cyclic loads, though most applications are for seismic retrofitting schemes and cyclic shear loading generally results in reduced load capacity due to fatigue failure. To overcome the deficit in knowledge, shear tests on various FRP anchors were carried out. For these tests, FRP anchors were installed in concrete specimens on a separating steel section. The FRP anchor was then directly loaded to determine the capacity of the isolated component. This paper describes the testing approach and procedure. Details on the experimental results for static tests are presented and an outlook on seismic tests is given.