Creaco E.,University of Ferrara |
Franchini M.,University of Ferrara |
Walski T.M.,Bentley Systems Inc.
Journal of Water Resources Planning and Management | Year: 2014
The traditional optimization approach for water distribution mains is that of considering a single design scenario with prefixed nodal demands representing the peak values at the end of the life cycle of the construction. Instead, this paper presents a different approach for the design of water distribution mains aimed at considering the phasing of construction. It makes it possible to identify, on prefixed time steps or intervals (for instance 25 years), the upgrade of the construction rendering the network able to satisfy, during the expected life of the system, growing nodal demands related to the increment in the population served. To show the benefits of this approach in comparison to using a single design flow, an optimization methodology, aimed at introducing new pipes in the network as needed at each time step, was set up and applied to a simple case study, where two different scenarios were considered concerning the growth of the network. Results showed that this approach is able to yield better results when compared with the single flow design, because it enables short-term construction upgrades to be performed while keeping a vision of the expected long term network growth. © 2014 American Society of Civil Engineers.
Agarwal A.,Bentley Systems Inc. |
Choe L.,U.S. National Institute of Standards and Technology |
Varma A.H.,Purdue University
Journal of Constructional Steel Research | Year: 2014
The behavior and design of steel columns subjected to thermal gradients due to fire loading were evaluated numerically and experimentally. The numerical (FEM) modeling approach was verified using experimental data from large-scale tests. The FEM modeling approach was used to conduct parametric studies to evaluate the effects of different heating configurations on steel column strength, and failure behavior at elevated temperatures. The analyses were conducted by coupling transient heat transfer analysis with implicit dynamic stress analysis. Columns subjected to four sided heating configuration had uniform temperature distributions through the cross-section. The columns were subjected to non-uniform (partial) heating to produce thermal gradients through the cross-section. The analysis results indicated that the column strength and failure behavior depended on the column slenderness, axial loading, and heating configuration. Failure modes included flexural buckling about the weak axis, flexural buckling about the strong axis, and flexural-torsional buckling. The analysis results also indicated that columns subjected to uniform heating had significantly higher heat influx. In most cases, columns subjected to non-uniform heating failed at lower average temperatures than columns subjected to uniform heating. However, the columns subjected to uniform heating reached their failure temperatures faster than the columns subjected to non-uniform heating due to the higher heat influx. The exceptions were very slender columns subjected to axial loads greater than 50% of their ambient load capacity. The results from the parametric studies were used to develop design equations for wide flange steel columns subjected to non-uniform heating resulting in thermal gradients through the cross-section. © 2013 Elsevier Ltd.
Agarwal A.,Bentley Systems Inc. |
Varma A.H.,Purdue University
Engineering Structures | Year: 2014
This paper presents a qualitative assessment of the importance of gravity columns on the stability behavior of a typical mid-rise (10 story) steel building subjected to corner compartment fires. Two ten-story steel buildings with composite floor systems were designed following the design practices in the US. One of these buildings had perimeter moment resisting frames (MRFs) to resist lateral loads while the other building had an interior core of RC shear walls. Effects of gravity loads and fire conditions were simulated using the finite element method and numerical analysis techniques.The results from the numerical investigations indicated that gravity columns govern the overall stability of building structures under fire conditions. Gravity columns have the highest utilization ratio, and they are most likely to reach their critical temperatures first. If gravity column failure occurs, the load shed or dropped by the failed column has to be redistributed to the neighboring columns to maintain overall structural stability. This axial load redistribution can occur through the development of alternate load paths including catenary action. Simulation results indicate that the presence of steel reinforcement in the concrete slabs (in addition to the minimum shrinkage reinforcement) facilitates uniform redistribution of the axial load dropped by the failed gravity column to the neighboring columns. The additional steel reinforcement improves the flexural and tensile strengths of the composite floor system, which enhances its ability to develop alternate load paths including catenary action in the slab, and thus maintain structural stability after gravity column failure. © 2013.
Mozaffari N.,Bentley Systems Inc. |
Voyiadjis G.Z.,Louisiana State University
International Journal of Plasticity | Year: 2016
The framework of coupled nonlocal damage model through phase field method and viscoplasticity in continuum scale is developed in this work. It is shown that the recently proposed non local gradient type damage model through the phase field method can be coupled to a viscoplastic model to capture the inelastic behavior of the rate dependent material. Free energy functional of the system containing two main parts including damage propagation as a phase transformation and viscoplastic deformation is proposed. Analogous to conventional viscoplastic models, two terms are incorporated in the viscoplastic free energy functional to appropriately address dissipation and the von Mises type viscoplastic surface. In this framework it is assumed that the damage variable covers summation of evolution of microcracks density in elastic and plastic region and the total strain represents the summation of the elastic and viscoplastic counterparts. It is shown that a material constant plays an important role to capture the ductile failure through the proposed model by means of numerical examples. © 2016 Elsevier Ltd.
Cleveland Jr. A.B.,Bentley Systems Inc.
Journal of Construction Engineering and Management | Year: 2011
Those working within the domain of construction engineering-the planning and management of the construction of infrastructure assets-today employ a wide range of information technology tools. The vast majority of these tools are used on desktop computers processing tabular information associated with scheduling, tracking, updating statuses, reporting, and similar tasks. In spite of the significant penetration of information technology into construction engineering, there is little direct reuse of the engineering information created during the design phase. Likewise, access to rich engineering information and applications to exploit this information have yet to be extended to mobile workers on the construction jobsite in any significant way. This paper explores a sampling of some of the emerging information technology tools that may be effectively applied to support construction engineering in the field. © 2011 American Society of Civil Engineers.