In this paper, we introduce a physics-inspired harmonic regression model to capture the nonstationary salinity dynamics at monitoring stations in well-mixed estuarine systems. Building on existing hybrid harmonic regression approaches, which modify the classical harmonic analysis to cope with nonstationary signals to predict tidal water levels, our model captures tidal and subtidal salinity variations using a simplified analytical salt intrusion model. The harmonic regression model was tested in the well-mixed Ems and Scheldt estuaries using data sets spanning 2–4 years, explaining 87.4%–96.4% of the observed salinity variance at upstream stations. A key finding is that storm surge effects typically have longer wavelengths than the estuary's length scale, which justifies using a linear relation between vertical and horizontal excursions. In alluvial estuaries, where the system widens, unsteadiness of the river discharge shows to be increasingly important for more downstream stations. The model quantifies the characteristic response time of salinity to variation in discharge. Based on a critical evaluation of the model equations, we offer a physical interpretation of the optimized parameters. Specifically, we discuss the Van der Burgh constant, which is an empirical coefficient commonly used in salt intrusion models. Our findings reveal that the Van der Burgh coefficient scales with the spatial scales of dispersion and advection, relative to changes in channel geometry. ... Read more

The thixotropic properties of contemporary mortars allow the insertion of mortar in small vertical seams by using a mortar pump without the need for traditional formwork. In such a seam, a vertical mortar connection for the transfer of shear forces can be created by simply adding a profile to the mortar-to-concrete interfaces. In this way a constructible continious vertical shear connection can be constructed between storey-high precast concrete wall elements. In this investigation, narrow vertical mortar connections are developed for the transfer of shear forces in precast concrete shear walls with tying reinforcement in the slabs. The shear behaviour of five versions with differently shaped mortar-to-concrete interfaces is obtained from shear tests. All experimental results are presented and discussed, while the shear behaviour of the Staggered shear key connection is analysed in detail. Also, the shear behaviour of the five mortar connections are mutually compared and assessed on their performance for functioning as a vertical mortar connection. A diagonal bar model is proposed for simulating the shear behaviour of the Staggered shear key connection, which is called the “inclined compression strut model”. Also, an equation for predicting the shear capacity is proposed. The functioning of the model and equation are investigated by applying them in case studies with cantilever shear walls in versions with and without window openings. ... Read more