A review of nature-based solutions for urban water management in European circular cities: a critical assessment based on case studies and literature

Abstract Nature-based solutions (NBS) can protect, manage and restore natural or modified ecosystems. They are a multidisciplinary, integrated approach to address societal challenges and some natural hazards effectively and adaptively, simultaneously providing human well-being and biodiversity benefits. NBS applications can be easily noticed in circular cities, establishing an urban system that is regenerative and accessible. This paper aims to offer a review on NBS for urban water management from the literature and some relevant projects running within the COST Action 'Implementing nature-based solutions for creating a resourceful circular city'. The method used in the study is based on a detailed tracking of specific keywords in the literature using Google Scholar, ResearchGate, Academia.edu, ScienceDirect and Scopus. Based on this review, three main applications were identified: (i) flood and drought protection; (ii) the water-food-energy nexus; and (iii) water purification. The paper shows that NBS provide additional benefits, such as improving water quality, increasing biodiversity, obtaining social co-benefits, improving urban microclimate, and the reduction of energy consumption by improving indoor climate. The paper concludes that a systemic change to NBS should be given a higher priority and be preferred over conventional water infrastructure

Analytical Method for Preliminary Seismic Design of Tunnels

Buried structures are categorized based on their shape, size and location. These main categories are near surface structures (e.g., pipes and other facilities), large section structures (e.g., tunnels, subways, etc.), and vertical underground structures (e.g., shafts and ducts). Seismic assessments of these structures are important in areas close to severe seismic sources. Seismic design of tunnels requires calculation of the deformation in surrounding geological formations. The seismic hazard on a site is usually expressed as a function of amplitude parameters of free-field motion. Therefore, simplified relations between depth and parameters of ground motion are necessary for preliminary designs. The objective of this chapter is to study and review the main analytical seismic methods which are used to develop a simple relationship between maximum shear strain, maximum shear stress and other seismic parameters

Düşey yönde ilerleyen kayma dalgalarıyla harekete geçen zeminlerde maksimum sismik gerilme tahmini için bir yarı ampirik yöntem.

Seismic design of underground structures requires calculation of the deformation in surrounding geological formations. The seismic hazard on a site is usually expressed as a function of amplitude parameters of free-field motion. Therefore, simplified relations between depth and parameters of ground motion are necessary for preliminary designs. The objective of this study is to employ random vibration theory to develop a simple relationship between maximum shear strain (γmax), depth, and ground-motion intensity parameters related to seismic hazard. The ground motion on surface, which is assumed as a stationary random process in the wide sense, is represented by a power spectral density function. Considering one-dimensional shear-wave propagation, transfer functions between ground motion and γmax amplitude at any arbitrary depth is formulated. The theoretical results are compared with the dynamic response of horizontally layered formations to seismic motions defined by accelerograms recorded on ground surface. The effect of material nonlinearity on peak strains is simply modeled by the method of equivalent linearization. It was concluded that the transition from PGA-sensitiveness of max to its PGV sensitiveness in uniformly elastic half-space occurs around the depth of (PGV·Vs)/(2·PGA). max is proportional to d and PGA in very shallow ranges of d, whereas it reaches to figures around (PGV/Vs)/2 by increasing d. max is also related to the amplitudes of a pseudo-spectral acceleration. Both relationships can be used as a reasonable first-order estimator for max in horizontally layered geological formations if the travel time of vertically incident shear waves to reach from free boundary to the depth of interest is substituted for the parameter d/Vs. The concept of equivalent travel time may yield overestimation of max if Vs is increasing by depth. However it leads severe underestimation of max in relatively soft layers embedded in stiffer geological formations. The method of equivalent linearization can be used for estimation of max if the response of geological layers to shearing is nonlinear. Ph.D. - Doctoral Progra

Investigating the effects of wind loading on three dimensional tree models using numerical simulation with implications for urban design

Abstract In this study, the effects of wind on an Eastern Red Cedar were investigated using numerical simulations. Two different tree models were proposed, each with varying bole lengths and canopy diameters. A total of 18 cases were examined, including different canopy diameters, bole lengths, and wind velocities. Using computational fluid dynamics (CFD) methods, the drag force, deformation, and stress of the tree models were calculated under different wind velocities and geometric parameters. A one-way fluid–structure interaction (FSI) method was used to solve the deformation of the tree. Additionally, velocity and pressure distribution around the tree were obtained. The results indicate that wind velocity and geometric parameters of the tree have a significant impact on deformation, drag force, and stress. As wind velocity increases from 15 to 25 m/s, the force on the tree increases substantially. The results also show that the diameter of the canopy has a bigger effect on stress and strain than the bole length. This study provides insights into tree behavior under wind loading for urban planning and design, informing optimal tree selection and placement for windbreak effectiveness and comfortable environments