Exploring the land development process and its impact on urban form in Hamilton, Ontario

The form of many Canadian cities has dramatically evolved over the past six decades due to urban sprawl. Several patterns can characterize this evolution including unlimited horizontal expansion of the city, leapfrog, and low‐density residential development at the outskirts, and widespread strip commercial and power centre retail development. Hamilton, Ontario is an example of a Canadian city that has experienced suburbanization and sprawled development for several decades. However, the nature of this sprawled development is unclear and its impact on urban form is not entirely understood. In this article, several hypotheses pertaining to sprawled land development and urban form are postulated and tested. The tests rely on point source data of the developed land parcels in Hamilton during the period 1950–2003. A number of spatial statistics techniques, including kernel estimation and complete spatial randomness (CSR) K‐function tests, are employed to examine the emerging nature of urban form. We hypothesize that while the city has been sprawling, the ongoing land development process is leading urban form into multinucleation. To support this assumption, we further hypothesize the existence of an interdependent spatial relationship between residential and commercial land uses at the emerging nuclei. Accordingly, we examine the strength of co‐clustering among these land use activities over time. The findings indicate that while the city has been sprawling, several consequent urban nuclei with mixed land use activities have been emerging and become more visible in recent years. This is an indication that the city's form is progressively becoming multinuclear. Furthermore, the estimates for the 1990s indicate interdependence between the locational patterns of residential and commercial land development. Co‐clustering between these two types of land uses is bi‐directional and occurs at a time lag of three to seven years. These findings affirm the existence of interdependence between land use activities at the observed nuclei, which support the emergence of a multinucleation.     

THREE DIMENSIONAL NONLINEAR BUILDING POUNDING WITH FRICTION DURING EARTHQUAKES

The three dimensional pounding phenomenon of two adjacent buildings during earthquakes with aligned rigid horizontal diaphragms is investigated for the linear and nonlinear structural response. The developed formulation takes into account three dimensional dynamic contact conditions for the velocities and accelerations based on the impulse-momentum relationship, using the coefficient of restitution e and the ratio μ, of tangential to normal impulses, which corresponds to the coefficient of friction under certain conditions. The contact points are determined geometrically from the displacements of the diaphragms' centre of mass. The results of the proposed formulation are compared with those obtained with the Lagrange multipliers approach. Test results are performed for two sets of multi-storey adjacent buildings subjected to real earth-quake motions with elastic and inelastic structural response.     

AUTOMATIC MINIMIZATION OF THE RIGIDITY ECCENTRICITY OF 3D REINFORCED CONCRETE BUILDINGS

The objective of this paper is to obtain the optimum design of 3D reinforced concrete buildings in terms of their performance under earthquake loading. This goal is achieved by considering the minimisation of the eccentricity between the mass centre and the rigidity centre of each storey layout as the optimisation objective in order to produce torsionally balanced structures. This problem is considered as a combined topology and sizing optimisation problem. The location and the size of the columns and the shear walls of the structure of each storey layout constitute the design variables. Apart from the constraints imposed by the seismic and reinforced concrete structure design codes, architectural restrictions are also taken into account. The test examples showed that a reduction in the structural cost of the building is achieved by minimising the eccentricity between the mass centre and the rigidity centre of each storey layout. Evolutionary optimisation algorithms and in particular a specially tailored algorithm based on Evolution Strategies is implemented for the solution of this type of structural optimisation problems.