Retrofit Alternatives Research Articles

Evaluating the Need and Potential of Equipping North American Houses with Multi-Zone VAV Systems

To identify potential energy savings and improvements to thermal comfort in the Canadian residential sector, a survey on occupant behaviour and control of thermal environment was conducted from April-June 2009 in low-rise dwellings in Ontario, Canada. A total of 396 completed responses were received. Survey results show that approximately 20% of the respondents were not satisfied with their room temperature in the winter. Inadequate level of controllability to room temperature is perceived as the most serious problem. Problems associated with overheating during the winter and overcooling during the summer was also identified. Observations from the survey results helped identify the deficiencies of the heating equipments built today and suggest improvements should be made to increase the controllability of current systems. Thermal simulation was then conducted to identify the problems with single-zone systems commonly built today, and to investigate the potential retrofit alternative. Simulation results show that a multi-zone system can effectively mitigate the deficiencies suffered by existing systems and can drastically improve the energy performances of houses.

Risk‐based optimal retrofit of a tall steel building by using friction dampers

SUMMARYFriction dampers, whose configuration is optimized on the basis of the probabilistic seismic loss associated with a building's damage due to ground motion, were utilized in this study to optimally retrofit a 15‐story steel structure. In line with the concept of performance‐based earthquake engineering (PBEE), a decision‐making procedure based on the monetary seismic loss was incorporated for optimizing the dampers' configuration. A nonlinear numerical model was initially established for representing the structure. In this regard, a brace–damper system was modeled with the buckling of brace elements being addressed accurately and by representing the friction damper's load–displacement relationship on the basis of laboratory evidences. By monitoring the structural deformations in two different response levels, two patterns were established for the distribution of the dampers' strengths throughout the structure, and a number of retrofit alternatives were proposed subsequently. By using incremental dynamic analysis and following the PBEE methodology, the annualized loss (AL), which accounts for all potential damage states in the building and a broad range of seismic intensities, was calculated for each alternative frame. The AL is regarded as a decision variable upon which the best damper configuration is selected. Revealing conclusions were finally made regarding optimal configuration of the damper–brace system. Copyright © 2011 John Wiley & Sons, Ltd.

Investigating the use of path flow indicators as optimization drivers in batch process retrofitting

Improvement of batch processes has gained much attention in industry due to the competitive market and stricter environmental legislation. This paper focuses on a process flowsheet decomposition based methodology resulting in path flow indicators which are able to highlight process alternatives with an improved performance. The novel aspects introduced in this methodology are the implementation of a new path flow indicator category that focuses on unit occupancy time and the multi-objective process assessment in order to reveal sustainable retrofitting actions. Furthermore, the retrofit alternatives are not only classified according to the diverse objective functions but also to the differences observed in the path flow indicator matrix of the generated retrofit alternatives compared to the base case. This classification enables a more detailed analysis of the retrofit alternative impact and illustrates the potential of path flow indicators as optimization drivers. The methodology is exemplified in an industrial batch process case study.

Exterior wide beam–column connections in existing RC frames subjected to lateral earthquake loads

In this paper, the seismic performance of reinforced concrete exterior wide beam–column connections with shallow spandrel beams lightly reinforced for torsion and moderate levels of gravity loads was investigated experimentally. The study focuses on existing frames designed and detailed according to construction practices used over ten years ago in the moderate-seismicity Mediterranean area. The results can be useful for assessing the seismic vulnerability of older structures and orienting seismic retrofit alternatives. Two 3/5 scale test models representative of exterior sub-assemblages in a prototype six-story building were subjected to gravity-load levels typical of those acting during an earthquake, and quasi-static cyclic lateral loads until failure. The performance was studied in terms of strength, displacement, ductility and energy dissipation capacity. The data are analyzed in conjunction with the results of previous tests. The specimens exhibited a “strong column–weak beam” type of flexural yielding mechanism. The average drift ratios at first yielding of the wide beam longitudinal reinforcement, δ y o , and at failure, δ u , were 2.2% and 4.5% respectively; the displacement ductility ratio μ was approximately 2.2. Comparison to similar connections without added gravity loads showed that moderate levels of gravity loading increased δ y o by about 40%, and decreased by a similar percentage the value of μ and the energy dissipated in each half cycle of displacement expressed in terms of an equivalent viscous damping ratio. Finally, two approaches for estimating the wide-beam flexural capacity are examined.

Retrofit of an existing Italian bridge rail for H4a containment level using simulation

This paper describes the methodology for the development of a crashworthy heavy containment bridge rail for the Italian Highway System. The current design was determined to be inadequate for heavy vehicle containment and could not be demolished due to damage risk to bridge superstructure. Italian Highway Agency has decided to retrofit the current design. Two different bridge rail models are developed and analysed using 30 ton heavy vehicle according to European EN1317 Test TB71 requirements. Detailed finite element analyses are performed to evaluate the acceptability of retrofit alternatives. A versatile, highly non-linear and widely accepted finite element program LS-DYNA is used to simulate the crash events. Analysis results show that the final bridge rail model successfully contains and redirects the 30 ton vehicle and it is found to be an acceptable retrofit to existing bridge rail design. A full-scale crash test is recommended to substantiate simulation findings.

Seismic behavior of interior connections in existing waffle-flat-plate structures

This paper investigates the seismic behavior of interior connections in reinforced concrete waffle-flat-plate structures subjected to moderate gravity-load levels like those acting during an earthquake. The scope is the existing buildings designed and detailed according to construction practices used over 10 years ago in the moderate-seismicity Mediterranean area. The results are useful for both assessing the seismic vulnerability of older structures and orienting seismic retrofit alternatives. To this end, a 3/5 scale test model representative of an interior waffle flat plate–column connection in a prototype six-story building was subjected to gravity and cyclic loading until failure. The experimental data are discussed in conjunction with the results of previous tests and ACI 318-05 code idealizations. The specimen exhibited a “strong column–weak plate” type of flexural-yielding mechanism. The test results indicate that: (a) the effective slab width and the fraction of unbalanced moment transferred by flexure, γ f , that ACI 318-05 code prescribes in Section 13.5.3.2. are adequate for predicting the strength of this type of connection, while the variation of γ f permitted by ACI 318-05 code in Section 13.5.3.3 is not recommended; (b) the lateral drift at the first yielding of the longitudinal bars is 3 times higher than the 0.5% admitted by Eurocode 8 to satisfy the “damage limitation requirement”; (c) the ultimate drift ratio (4.4%), associated with a strength reduction of more than 20%, is approximately at the average of the values reported for flat slabs with shear reinforcement in previous studies; (d) the ultimate energy dissipation capacity of the connection is about one-fourth of the minimum value reported for well-behaving reinforced-concrete elements with flexural behavior.

Use of advanced composite curves for assessing cost-effective HEN retrofit I: Theory and concepts

This paper presents the theory and concepts of a graphical method for heat exchanger network (HEN) retrofit that gives new insights about the complexity and possible solutions of different retrofit alternatives. The method uses knowledge about the placement of heaters/coolers in the existing HEN to evaluate the potential for cost-effective retrofit. One general result this method predicts is that the closer to the pinch the existing heaters/coolers are located, the higher the potential for cost-effective retrofit. Networks that are badly engineered from a grass-root perspective, prove to be a good basis for cost-effective retrofits.

Process Intensification for the Retrofit of a Multicomponent Distillation PlantAn Industrial Case Study

Process intensification is currently considered as the main trend to improve process performance, and one of the major approaches to this regard is to reduce the number of pieces of equipment in the plant. For distillation systems, thermal coupling technique provides such an approach to retrofit the traditional simple column configurations through the elimination of the condenser and/or the reboiler. In this work, starting from the existing plant with the simple columns, two types of retrofit alternatives are proposed. The first includes the possible alternatives by eliminating all the condensers and reboilers involving the submixtures. The second includes all the possible alternatives when only some of the condensers and/or reboilers are eliminated at one time. The latter solution represents less modification to the existing plant. In addition, in order to investigate the capital investment for the modified plant, all the obtained alternatives through the recombination of the column sections have been compared. All the configurations were compared with respect to energy saving and the possibilities to reuse the plant equipment. The optimal solution was found to be the alternative that has the minimum modification to the existing plant. At the same time, it achieves a 23% savings on energy consumption and allows a maximum reuse of the pieces of the existing equipment.

ECONOMIC ASSESSMENT OF THE SEISMIC RETROFITTING OF LOW-COST APARTMENT BUILDINGS

When structural retrofitting of buildings is required due to seismic safety considerations, building owners or government officials are faced with a crucial decision whether to demolish and rebuild their buildings, or retrofit them. Simple decisions based on fixed proportions, such as demolish and rebuild if retrofit costs exceed 40% of the replacement cost, may be misleading. A financial analysis should be carried out considering all the revenues and costs of the building during its life time. A low-cost residential apartment building that has a construction cost of $140/m2 is selected in this study to represent the vulnerable buildings in developing countries under seismic risk. Life-cycle cost analysis approach is employed to value the rebuild or retrofit alternatives to compare economically. Economic assessment has been carried out for various parameters. It has been found that the age of the building and the retrofit ratio are dominant parameters among the others. The critical retrofit ratio (percent of retrofit cost to initial construction cost) varied from 25% for 40 year old buildings to 67% for 10 year old buildings. It is suggested that economical decisons should not be made simply by comparing the retrofit costs to initial construction costs.

A study on the seismic behavior of a retrofitted building based on nonlinear static and dynamic analyses

This study describes the seismic performance of an existing five storey reinforced concrete building which represents the typical properties of low-rise non-ductile buildings in Turkey. The effectiveness of shear walls and the steel bracings in retrofitting the building was examined through nonlinear static and dynamic analyses. By using the nonlinear static analysis, retrofitted buildings seismic performances under lateral seismic load were compared with each other. Moreover, the performance points and response levels of the existing and retrofitting cases were determined by way of the capacity-spectrum method described in ATC-40 (1996). For the nonlinear dynamic analysis the records were selected to represent wide ranges of duration and frequency content. Considering the change in the stiffness and the energy dissipation capacities, the performance of the existing and retrofitted buildings were evaluated in terms of story drifts and damage states. It was found that each earthquake record exhibited its own peculiarities, dictated by frequency content, duration, sequence of peaks and their amplitude. The seismic peformance of retrofitted buildings resulted in lower displacements and higher energy dissipation capacity depending mainly on the properties of the ground motions and the retrofitting strategies. Moreover, severe structural damage (irreparable or collapse) was observed for the existing building. However, buildings with retrofit alternatives exhibited lower damage levels changing from no damage to irreparable damage states.

Impact of technological development, market and environmental regulations on the past and future performance of chemical processes

This work presents a systematic approach to introduce the evolution of technology, market and environmental regulations into process design, more specifically into the generation of retrofit alternatives. For this purpose the information on development of technology, economic and environmental performances is obtained. Firstly, the evolution of the technology for the production of a chemical and its precursors is analyzed. Afterwards, the development of the market situation regarding prices and demand together with the progress of the environmental regulations is studied. This allows for the assessment of the economic and environmental performance of the process over time. Finally, the economic and environmental assessment is used for the identification of process alternatives that can further improve the process performance in the future. This methodology is demonstrated using the production of hydrogen cyanide as a case study.

Seismic Retrofit of Reinforced Concrete Buildings Designed for Gravity Loads: Performance of Structural Model

A partially prestressed concrete alternative and two masonry retrofit alternatives are analyzed for improving the local and global response performance of reinforced concrete frame structures designed only for gravity loads and constructed in low-to-moderate seismic zones. The objective of these retrofits is to reconfigure the structural failure mode by averting a catastrophic soft-story collapse and enforcing a more ductile beam sidesway mechanism. A prestressed concrete jacketing alternative to limited columns was selected to retrofit the one-third scale model reinforced concrete frame building that had been previously tested by the authors. The seismic response of the retrofit model structure was investigated experimentally using the shaking table at State University of New York at Buffalo. A comparison is made of the experimental frame response before and after retrofitting. It is concluded that the seismic performance of vulnerable (soft-story prone) gravity load design frames may be effectively enhanced by strengthening limited columns and thus, changing the failure mode to a beam sidesway mechanism with acceptable story deformation levels.

A multiperiod minlp model for improving the flexibility of heat exchanger networks

A mixed integer nonlinear programming (MINLP) model is developed for the retrofit of heat exchanger networks in order to improve their ability to operate feasibly over a specified set of operating conditions (stream flowrates, stream inlet temperatures, overall heat transfer coefficients) at minimum cost. The model is based on a multiperiod match-network hyperstructure representation, which contains all possible retrofit alternatives embedded within, for all periods. Periods correspond to “critical” operating conditions identified through the solution of a flexibility analysis subproblem for the existing network. The resulting MINLP model also involves an explicit heat flow model and an objective function accounting for all structural modifications and operating cost. The solution of this MINLP problem provides a retrofitted network structure that is energy efficient and flexible to operate at the specified critical conditions.

Screening of process retrofit alternatives

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTScreening of process retrofit alternativesWayne R. Fisher, Michael F. Doherty, and James M. DouglasCite this: Ind. Eng. Chem. Res. 1987, 26, 11, 2195–2204Publication Date (Print):November 1, 1987Publication History Published online1 May 2002Published inissue 1 November 1987https://doi.org/10.1021/ie00071a005RIGHTS & PERMISSIONSArticle Views209Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

A Directed Weather Data Filter

It is important to reduce the computational burden of energy-analysis computer programs (such as those that compute expected heating and cooling loads and the energy required to meet these loads) since the input may include, for example, hourly measurements of several weather variables over periods of time of up to ten years. It is possible to generate a small set of weather data to represent a larger, more comprehensive set by using computer programs called weather data filters. However, existing filters that are generally able to preserve statistical properties of the original data offer no a priori method for controlling or even estimating the errors they introduce in the output of the energy analysis programs. This problem exists because these filters deal only with weather data and do not utilize any information regarding the building to be analyzed, its occupancy schedule, its mechanical systems, or the energy analysis function itself. This paper describes a weather filter that preserves the “energy content” of the data; i.e., given a particular building design and usage schedule, this filter generates a small set of weather data which, when properly weighted, produces the same total heating and cooling loads as the original data. Because the error caused by using the filtered weather data falls well within acceptable bounds even when changes are made in the building design, the filter described allows the designer to test a large number of design or retrofit alternatives for energy efficiency at very low computational cost.