Partial Retrofit Research Articles

Performance simulation and energy efficiency analysis of multi-energy complementary HVAC system based on TRNSYS

The failure rate and operating cost of the C-B (chiller-gas boiler) system, which has been in use for a long time, are increasing year by year, but there is a lack of reasonable programs and effective measures on how to retrofit the C-B system. In order to explore the prospect of ground-source heat pumps applied to the retrofit of C-B systems in HSCW (hot summer and cold winter) zone, this study designed a G-C-B (GSHP-Chiller-Boiler) system in a partial retrofit context and constructed a TRNSYS numerical simulation model of the retrofit system. Secondly, the performance and energy efficiency of the system is analyzed as well as different control strategies for the ground source heat pump cooling tower are discussed. Finally, the energy conversion efficiency of the chiller is compared based on the energy flow of the system. Studies have shown that the G-C-B system can achieve a seasonal performance factor of 5.3 during the cooling season and 4.1 during the heating season. Compared to the existing C-B system, year-round electricity consumption was reduced by 21 %, gas consumption by 92 %, and combined energy demand by 49.6 %. With the addition of GSHP, the energy conversion efficiency of the chiller has also increased by 21 %. The soil temperature of the G-C-B system increased by less than 0.5 °C after ten years of continuous operation. This paper can provide a valuable theoretical basis for the energy form modification of the C-B system in the HSCW zone.

The use of hydrogen as alternative fuel for ship propulsion: A case study of full and partial retrofitting of roll-on/roll-off vessels for short distance routes

Roll-on/Roll-Off (Ro-Ro) vessels, including those without and with passenger accommodation Roll-on/roll-off passenger (Ro-Pax), can be totally or partially retrofitted to reduce the greenhouse gas (GHG) emissions in maritime transport not only during hoteling operation at the dock but also during service. This study is based on data of the vessel routes connecting the Port of Piombino to the Elba Island in Italy. Three retrofitting scenarios have been considered: replacement of the main and auxiliary engines with fuel cells (FC) (full retrofitting), replacement of the auxiliary engines with FCs (partial retrofitting) and replacement of the auxiliary engines with FCs and hoteling only with auxiliary engines for one specific vessel. The amount of hydrogen, the filling time and the energy needed for production, compression and pre-cooling of hydrogen have been calculated for the different scenarios.

Evaluation of energy-saving retrofit projects of existing rural residential envelope structures from the perspective of rural residents: the Chinese case.

The existing residential envelope in rural areas has low energy efficiency, with low energy utilization and serious energy waste for winter heating. However, in recent years, farmers have not undertaken energy efficiency retrofit projects for existing buildings in rural areas. This study proposed an evaluation model based on the logistic-AHP-TOPSIS method from the perspective of farmers. First, this study conducted a questionnaire survey of 208 rural households and used logistic models to determine which existing evaluation indicators significantly impact farmers' willingness to participate in energy efficiency retrofit projects. Second, the weights of the eight indicators were determined using AHP. Finally, this study evaluated the retrofit program of a case in Gansu Province using the TOPSIS method. In the analysis, total investment, annual winter heating costs and energy efficiency improvements were found to be the most important factors for farmers. The highest score for existing buildings was 0.3747 because there is no additional investment required; the option of partial retrofitting according to the actual needs of households scored 0.3350 because it balances economic performance with energy efficiency performance; The entire retrofit program has the highest investment and a long payback period, and its score is the lowest with 0.2904. Furthermore, the study recommended that a self-build and self-repair organization led by village collectives be developed to unify the retrofit design and construction and lower renovation costs. Bulk purchases could enable farmers to increase their power in negotiations.

Temporal spillover of private housing energy retrofitting: Distribution of home energy retrofits and implications for subsidy policies

Energy retrofitting of private housing is fundamental to reducing the environmental footprint of the building stock, and energy efficiency policies are based on assumptions of the effects of retrofitting, including those on further retrofitting, also called temporal spillover. No study has directly investigated the impact of energy retrofitting on future energy retrofits.Our results (N = 6402) show that respondents who completed energy retrofits in the past three years are significantly more likely to undertake new energy retrofits (IRR = 3.449). This is also true when controlling for demographic variables (IRR = 2.752), attitude and self-efficacy. Younger age, lower income, higher investment capacity, a more positive attitude, and higher self-efficacy toward retrofitting are associated with more energy retrofits.Since a strong temporal spillover effect is present in energy retrofitting, we suggest that locking in the energy building standard to a suboptimal level after partial retrofitting is not as great a challenge as previously thought. Moreover, due to the distribution of retrofits, the average number of retrofits undertaken is a misleading indicator of the trends in a nation's building stock, and subsidizing small scale-retrofits may provide major benefits for households' overall environmental footprint.

Precast prestressed concrete frames for seismically retrofitting existing RC frames

A precast prestressed concrete frame system with mild press joints is introduced for the seismic retrofit of existing reinforced concrete frames. Cyclic loading tests are conducted on precast prestressed concrete and cast-in-situ reinforced concrete frame subassemblies to investigate the hysteretic behavior and damage characteristics of the frames. The test results demonstrate the damage-tolerance of precast frames in terms of well-controlled cracking and minimized residual drift compared to monolithic RC frames. A simplified numerical model is introduced to simulate the hysteretic behavior of mild press joints. The dynamic seismic response of a prototype building retrofitted by the proposed method is evaluated by numerical analysis. Two retrofit plans with different attached precast frames are compared. The results suggest that a partial retrofit of certain lower stories, which has been a common practice in Japan, may create drift concentration in the upper stories of a building.

Seismic evaluation and partial retrofitting of concrete bridge bents with defect details

Abstract The need for seismic retrofitting of bridges after severe earthquakes has become important in recent years. This study examines the seismic evaluation of concrete bents of highway bridges designed and implemented according to the 1990s regulations. Compared with the older codes, 1990s codes have more complex details for connections which are evaluated by experimental and numerical methods in this research. Significant improvement was observed in the behavior of the specimens designed with 1990s codes; however, this improvement is not enough as strength degradation was also reported in the inner cycles of the hysteresis curves. Therefore, seismic improvement was performed using performance levels. Results showed that in the connection zone, the longitudinal bar slippage occurs and the performance of connection is weak. In experimental phase, a specimen was constructed with external pre-stressing in a transverse direction for retrofitting. The level of improvement in behavior was also evaluated using parameters such as energy dissipation, performance levels and force-displacement curves.

Determinants of energy-efficient home retrofits in Slovenia: The role of information sources

The paper examines what determines household energy-efficient retrofit decisions in Slovenia based on analysis of more than 1000 single family-house owners, survey respondents. While previous studies typically stress the importance of professional energy audits, this paper shows that other formal and informal sources of information and advice also play a significant role in informing homeowners and fostering energy-efficient retrofit decisions. Compared to partial retrofit measures, an integral approach to retrofits is more strongly associated with estimated energy saving potential, household income and professional advice seeking. On the other hand, free public energy consultation appears to have failed to deliver the expected outcome. Results of econometric analysis on barriers and drivers for building energy retrofits call for strengthening the financial incentives, informing and educating the public through various information sources, combined with the redesign of public Energy Advisory Network to increase the reach of residential building energy-efficiency policies.

Seismic Risk Mitigation for a Portfolio of Reinforced Concrete Frame Buildings through Optimal Allocation of a Limited Budget

The mitigation of seismic risk for a population of vulnerable civil critical structures (e.g., hospitals, schools, and bridges) is a crucial issue for many governments of earthquake-prone regions. Furthermore, owing to the global economic crisis, limited financial resources make full seismic rehabilitation of entire building stocks challenging. Therefore, a critical decision has to be made on the following key question: what is the most advantageous way of spending the available budget while treating each building in a portfolio differently, by giving it a different level of structural improvement to reduce the overall risk of the portfolio of buildings as much as possible? Herein, a decision-making tool is proposed to address this high-social-impact issue. Starting with a limited amount of information, which is gathered through expeditious surveys on existing buildings, and by involving uncertainties, the overall risk is evaluated from the fragility analysis of each structure. This is conducted via simplified pushover analyses by considering the local seismic hazard. Then, an optimization is performed for each building of the portfolio to select a relevant structural intervention from four alternatives (no intervention, partial retrofit, full retrofit, and demolition and reconstruction), based on both the overall risk reduction and the amount of financial resources. Procedures for quick estimation of fragility curves and installation costs are also discussed as part of the proposed approach. Finally, a practical application is presented with reference to a simulated case study consisting of 46 reinforced concrete school buildings located in Campania, Italy.

Review of Methods for Buildings Energy Performance Modelling

Research presented in this paper gives a brief review of methods used for buildings energy performance modelling. This paper gives also a comprehensive review of the advantages and disadvantages of available methods as well as the input parameters used for modelling buildings energy performance. European Directive EPBD obliges the implementation of energy certification procedure which gives an insight on buildings energy performance via exiting energy certificate databases. Some of the methods for buildings energy performance modelling mentioned in this paper are developed by employing data sets of buildings which have already undergone an energy certification procedure. Such database is used in this paper where the majority of buildings in the database have already gone under some form of partial retrofitting – replacement of windows or installation of thermal insulation but still have poor energy performance. The case study presented in this paper utilizes energy certificates database obtained from residential units in Croatia (over 400 buildings) in order to determine the dependence between buildings energy performance and variables from database by using statistical dependencies tests. Building energy performance in database is presented with building energy efficiency rate (from A+ to G) which is based on specific annual energy needs for heating for referential climatic data [kWh/(m2a)]. Independent variables in database are surfaces and volume of the conditioned part of the building, building shape factor, energy used for heating, CO2 emission, building age and year of reconstruction. Research results presented in this paper give an insight in possibilities of methods used for buildings energy performance modelling. Further on it gives an analysis of dependencies between buildings energy performance as a dependent variable and independent variables from the database. Presented results could be used for development of new building energy performance predictive model.

Seismic performance of reinforced concrete columns retrofitted by various methods

In this study, various retrofit methods for concrete columns with non-seismic reinforcement details were developed and investigated: steel jacketing, carbon fiber reinforced polymer (CFRP) wrapping, concrete jacketing with non-shrinkage mortar, and new concrete jacketing with amorphous metallic fiber (AMF) reinforced concrete. Eleven half-scale reinforced concrete columns including two different control specimens, which were designed to fail in shear or flexure-shear, and nine retrofitted specimens were fabricated and tested under cyclic loading, simulating earthquake loading combined with axial loading. Two different retrofit strategies were applied to the control specimens: partial retrofit in the plastic hinge zone, mainly aiming at increasing deformability, and full retrofit in the entire range of columns, aiming at increasing both shear strength and deformability. The seismic capacity of the test specimens was analyzed in terms of various factors: load–drift relationship, dissipated energy, damping ratio, effective stiffness, and ductility. The test results showed that the retrofitted specimens presented ductile failure mode and enhancement in the dissipated energy and the damping ratio, but the effect differed for each retrofit method. Furthermore, based on the test results, the variables (or conditions) used to define the modeling parameters of the nonlinear analysis specified in ASCE 41-13 were modified in order to use the parameters of nonlinear analysis after retrofitting the columns. In addition, the nonlinear load-deformation curves established based on the modified conditions were compared with the test results.

Modal parametric changes in a steel bridge with retrofitting

This paper presents the status improvement of an old damaged deck type rural road steel truss bridge through the modal parametric study after partial retrofitting. The dynamic and static tests on bridge were carried out as in damaged state and after partial retrofitting. The dynamic testing on the steel bridge was carried out using accelerometers under similar environmental conditions with same speed of the moving vehicle. The comparison of the modal parameters i.e., frequency, mode shape mode shape curvature, modal strain energy, along with the deflection parameter are studied with respect to structural analytical model parameters. The status up gradation for the upper and downstream truss obtained was different due to differential level of damage in the bridge. Also after retrofitting the structural elemental behavior obtained was not same as desired. The damage level obtained through static tests carried out using total station indicated further retrofitting requirement.

Time–frequency and wavelet-based study of an old steel truss bridge before and after retrofitting

Signal-processing techniques have been widely used in structural health monitoring and nondestructive evaluation. Wavelet analysis, a relatively new mathematical and signal-processing tool, for damage detection in various civil and mechanical structures. It is a time–frequency analysis that provides more detailed information about nonstationary signals which traditional Fourier analysis miss. This paper aims to provide the damage identification in an existing 100-year-old deck-type steel truss bridge using-frequency- and time–frequency-based approaches. The dynamic testing of steel bridge was carried out using accelerometers for the damaged state and after partial retrofitting under similar environmental conditions and instrumental set up. The comparison is carried out using power spectral density, short-time Fourier transform, and wavelet packet transform with respect to both the upstream and the downstream trusses of the bridge. Higher and uniform dissipation of energy at resonating-frequency of the respective node after retrofitting showed intactness of joints. The variations of power spectral density in the first mode of the upstream and the downstream trusses clearly revealed improvements in the bridge signifying the importance of generating a signature of bridge before and after retrofitting. The status upgradations for the upstream and the downstream trusses obtained were different due to differential levels of damage in the bridge. Also, after retrofitting, the structural elemental behavior obtained was not the same as desired.

How much is enough? Minimal responses of water quality and stream biota to partial retrofit stormwater management in a suburban neighborhood.

Decentralized stormwater management approaches (e.g., biofiltration swales, pervious pavement, green roofs, rain gardens) that capture, detain, infiltrate, and filter runoff are now commonly used to minimize the impacts of stormwater runoff from impervious surfaces on aquatic ecosystems. However, there is little research on the effectiveness of retrofit, parcel-scale stormwater management practices for improving downstream aquatic ecosystem health. A reverse auction was used to encourage homeowners to mitigate stormwater on their property within the suburban, 1.8 km2 Shepherd Creek catchment in Cincinnati, Ohio (USA). In 2007–2008, 165 rain barrels and 81 rain gardens were installed on 30% of the properties in four experimental (treatment) subcatchments, and two additional subcatchments were maintained as controls. At the base of the subcatchments, we sampled monthly baseflow water quality, and seasonal (5×/year) physical habitat, periphyton assemblages, and macroinvertebrate assemblages in the streams for the three years before and after treatment implementation. Given the minor reductions in directly connected impervious area from the rain barrel installations (11.6% to 10.4% in the most impaired subcatchment) and high total impervious levels (13.1% to 19.9% in experimental subcatchments), we expected minor or no responses of water quality and biota to stormwater management. There were trends of increased conductivity, iron, and sulfate for control sites, but no such contemporaneous trends for experimental sites. The minor effects of treatment on streamflow volume and water quality did not translate into changes in biotic health, and the few periphyton and macroinvertebrate responses could be explained by factors not associated with the treatment (e.g., vegetation clearing, drought conditions). Improvement of overall stream health is unlikely without additional treatment of major impervious surfaces (including roads, apartment buildings, and parking lots). Further research is needed to define the minimum effect threshold and restoration trajectories for retrofitting catchments to improve the health of stream ecosystems.

Experience gained with development and commissioning of retrofitted process control systems for large power units

Experience gained for many years at ZAO Interavtomatika with work on retrofitting control and monitoring systems of large power units is summarized. Principles based on which these systems should be retrofitted are considered together with the factors influencing the choice of retrofitting option, as well as decisions on constructing a process control system during full and partial retrofitting. Recommendations are given for the optimal scope of functions that should be incorporated in the software and hardware tools of a process control system during its retrofitting.

Analytical Evaluation of Retrofit Strategies for Multicolumn Bridges

The objective of the work of this paper was to investigate analytically the feasibility and advantages of applying various combinations of steel jacket retrofit measures developed for single-column bent bridges to multicolumn bent bridges. To achieve the objective, an existing nonlinear dynamic bridge analysis program with elastic–perfectly plastic column behavior and a conventional hysteresis model was modified in order to include softening behavior from column damage and a more realistic hysteresis rule for cyclic loading. A 2D structural model of an actual bridge was used to evaluate column retrofitting measures by applying a typical seismic record. Both partial and full column retrofit strategies were shown to result in decreased maximum earthquake response and decreased plastic deformation of columns for the bridge bent compared to the case without retrofitting, but to varying degrees. However, for some partial retrofit strategies, the plastic hinge rotation at the unretrofitted columns was deemed to be unacceptable. Therefore, it was concluded that partial column retrofit strategies are viable only if combined with an evaluation of the ductility capacity of the bridge.