Resilience-based retrofitting of existing urban RC-frame buildings using seismic isolation

The improvement of the seismic resilience of existing reinforced-concrete(RC) frame buildings, which is essential for the seismic resilience of a city, has become a critical issue. Although seismic isolation is an effective method for improving the resilient performance of such buildings, target-oriented quantitative improvements of the resilient performance of these buildings have been reported rarely. To address this gap, the seismic resilience of two existing RC frame buildings located in a high seismic intensity region of China were assessed based on the Chinese Standard for Seismic Resilience Assessment of Buildings. The critical engineering demand parameters(EDPs) affecting the seismic resilience of such buildings were identified. Subsequently, the seismic resilience of buildings retrofitted with different isolation schemes(i.e., yield ratios) were evaluated and compared, with emphasis on the relationships among yield ratios, EDPs, and levels of seismic resilience. Accordingly, to achieve the highest level of seismic resilience with respect to the Chinese standard, a yield ratio of 3% was recommended and successfully applied to the target-oriented design for the seismic-resilience improvement of an existing RC frame building. The research outcome can provide an important reference for the resilience-based retrofitting of existing RC frame buildings using seismic isolation in urban cities.

Experience on offshore cathodic protection retrofitting in the northern South China Sea

Platforms I and II are steel structures located in offshore areas southeast of the Zhujiang (Pearl) River Delta, the northern South China Sea,. in about 110 in water depth. The jackets, with aluminum sacrificial anodes for cathodic protection (CP) of the immersed zone, were launched in March 1995. In May 096 a CP survey showed that, after almost one year of service, a low polarization level had been achieved and some extended unprotected zones existed; mainly in the deepest part of the Platform II. Further to this, a joint activity was decided in order to assess the need of a possible retrofitting of the CP systems. The results of the activity carried out are dealt with, including technical and economical comparisons amongst several retrofitting options, both with sacrificial anodes and with impressed current systems. The adopted solution is illustrated and data are reported on the level of protection presently achieved.

Analysis of the impact of large scale seismic retrofitting strategies through the application of a vulnerability-based approach on traditional masonry buildings

The buildings＇ capacity to maintain minimum structural safety levels during natural disasters, such as earthquakes, is recognisably one of the aspects that most influence urban resilience. Moreover, the public investment in risk mitigation strategies is fimdamental, not only to promote social and urban and resilience, but also to limit consequent material, human and environmental losses. Despite the growing awareness of this issue, there is still a vast number of traditional masonry buildings spread throughout many European old city centres that lacks of adequate seismic resistance, requiring therefore urgent retrofitting interventions in order to both reduce their seismic vulnerability and to cope with the increased seismic requirements of recent code standards. Thus, this paper aims at contributing to mitigate the social and economic impacts of earthquake damage scenarios through the development of vulnerability-based comparative analysis of some of the most popularretrofitting techniques applied after the 1998 Azores earthquake. The influence of each technique individually and globally studied resorting to a seismic vulnerability index methodology integrated into a GIS tool and damage and loss scenarios are constructed and critically discussed. Finally, the economic balance resulting from the implementation of that techniques are also examined.

Intervention Retrofitting and Rehabilitation of Al-Gawhara Palace at the Saladin Citadel, Cairo, Egypt

Al-Gawhara Palace also known as Bijou Palace is located in the south of the Mosque of Muhammad Ali in Saladin Citadel in Cairo (Figure 1 and Figure 2). It was commissioned and constructed by Muhammad Ali Pasha in 1814. Al-Gawhara Palace is one of the most famous historical royal palaces in Egypt and the most important modern architectural heritage that reflects an important historical period of the Egyptian modern history—the period of the rule of the family of “Muhammad Ali Pasha”. The causes of structural deficiency of the palace could be attributed to many reasons and actions, mainly due to the earthquakes and seismic events (in particular the Dahshuor earthquake, in October 1992), degradation of drainage and feeding systems leading to water leakage, lack of awareness of the palace values, deterioration resulting from the use of old government agencies and the conflicts among authorities supervising historical buildings. The present study includes many phases: 1) the significance of the original building from the circumstances and date of construction;2) detailed studies of the architectural features and design of the building as well as construction type, methods and techniques of construction;3) characterization of the construction and building materials;4) stability analysis of the structure under static and the impact of seismic loadings;5) engineering measures for intervention retrofitting of the palace (this pilot study presents the main design studies for intervention retrofitting and the rehabilitation and re-employment of Al-Gawhara Palace, started from the static monitoring, old and modern documenting of the current state of preservation thorough the strengthening project implementation;6) the study also presents the reuse designs to convert the palace to be a national museum, for the purpose of preserving it by proposing the best means to apply the correct principles and criteria for reuse and employment in a manner that preserves its value through the functions that fit these deficiencies, and the appropriateness of the present function of the value of minors.

Energy-Efficiency Retrofitting Strategies for Existing Residential Building Envelope System—A Case Study in China

With the rapid development of urbanization, the Chinese government has put equal emphasis on construction and retrofitting. But those projects did not achieve optimal effect because of the lack of targeted and systematic design guidance system. In this study, it first analyzes existing retrofitting methods and sorts into five retrofitting types as a basis, and then, captures the combi-nations and permutations of retrofitting methods and materials by parts and layers to build a database. After that, it combines different kinds of ap-proaches by hierarchical matrix method to conclude the most efficient strat-egy. This study also selects typical residential buildings built between 1980 and 2000 in cold climate area of Northeast China as the research objects to test the integrity and effectiveness. As the results of this paper, it provides systematic guidance and multiple performance-based retrofitting strategies of the existing residential envelope system, which can improve indoor ther-mal comfort with low energy consumption.

Review of Conventional and Innovative Technologies for Fire Retrofitting of Existing Buildings

Fire effects can be one of the most harmful conditions that any building may experience throughout its service life. Developing practical protection methods and concepts against potential fire disasters in buildings has been an important consideration in design of buildings in recent decades. Rapid developments in technology have heightened the demand for new and innovative fire protection systems in comparison with conventional and traditional methods. Such a need for new technologies is in particular of greater importance when it comes to existing buildings. Retrofitting an existing building for fire safety is a greater challenge compared with designing a new building using materials and components that have more desirable and superior fire rating to begin with. Furthermore, strategies to design a new building that includes state-of-the-art fire safety features are also different from solutions that may be more suitable for retrofitting an existing building. This paper presents a review of the literature concerning conventional and new or innovative retrofitting methods for fire safety of buildings. Advantages and disadvantages of different fire protection devices and methods as available and understood from the literature are mentioned. Study of fire safety systems shows that each has its drawbacks. Comparison of the results shows that disadvantages of a solitary system for retrofitting against fire can be improved by using a combination of several fire safety concepts or methods simultaneously.

Seismic Evaluation and Retrofitting of Existing Hospital Building in the Sudan

Sudan is not free from earthquakes. It has experienced many earthquakes during the recent history, and the previous studies on this field demonstrated this argument. This paper focuses on the study of seismic performance of existing hospital buildings in Sudan. The paper focused on studying design of reinforced concrete columns of a hospital building considering two load cases;case one is the design load including combinations of dead, live and wind loads and case two includes dead, live and seismic loads. The building was designed according to the Regulation of Egyptian Society for Earthquake Engineering (ESEE), using the linear static method (equivalent static method). The analysis and design were performed using the SAP2000 version 14 software package. The design results obtained from the two cases of loading were compared observing that the design based on case one was unsafe to withstand the additional load came from earthquake, because the cross sections and area of steel for the most of building columns are under the required values that needed to resist the loads of case two. If the building is constructed according to the design using the loadings of case one, this situation needs remedy. This paper suggested two solutions for this problem based on strengthening the weak columns by inserting reinforced concrete shear walls in the direction of y axis affected by seismic load. Solution one suggests shear walls of length 2.5 m with different wall thicknesses (15 cm, 20 cm, 25 cm and 30 cm), whereas solution two suggests shear walls of length 4.5 m and 15 cm width. It was found that solution one solved the problem partially because some columns were still unsafe, but solution two solved the problem completely and all columns were safe.

Amelioration and retrofitting of educational buildings

Following a seismic event that occurred years ago in Central Italy, the public opinion was growing and growing a concern on the adequacy of educational buildings all across Italy. This activated several political decisions and a consequent technical effort is in progress. Technically speaking one has to manage the classical problem of retrofitting existing buildings. However, the legal environment goes across national codes, targeted guidelines and the professional need of achieving pragmatic solutions based on ethical and social acceptation schemes.This paper introduces the topic in its worldwide exception and focuses then on some operative aspects in the Italian situation. It outlines the consolidated steps along this technical process and emphasizes the weak aspects one meets when going across the designers＇ reports.

Seismic retrofitting of reinforced concrete frame structures using GFRP-tube-confined-concrete composite braces

This paper presents a new type of structural bracing intended for seismic retrofitting use in framed structures. This special composite brace, termed glass-fiber-reinforced-polymer （GFRP）-tube-confined-concrete composite brace, is comprised of concrete confined by a GFRP tube and an inner steel core for energy dissipation. Together with a contribution from the GFRP-tube confined concrete, the composite brace shows a substantially increased stiffness to control story drift, which is often a preferred feature in seismic retrofitting. An analysis model is established and implemented in a general finite element analysis program - OpenSees, for simulating the load-displacement behavior of the composite brace. Using this model, a parametric study of the hysteretic behavior （energy dissipation, stiffness, ductility and strength） of the composite brace was conducted under static cyclic loading and it was found that the area ratio of steel core to concrete has the greatest influence among all the parameters considered. To demonstrate the application of the composite brace in seismic retrofitting, a three-story nonductile reinforced concrete （RC） frame structure was retrofitted with the composite braces. Pushover analysis and nonlinear time-history analyses of the retrofitted RC frame structure was performed by employing a suite of 20 strong ground motion earthquake records. The analysis results show that the composite braces can effectively reduce the peak seismic responses of the RC frame structure without significantly increasing the base shear demand.

Seismic collapse simulation of existing masonry buildings with different retrofitting techniques

Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake.The collapse of masonry walls may cause significant human casualties and economic losses.To maintain their integrity,several methods have been developed to retrofit existing masonry buildings,such as the constructional RC frame which has been extensively used in China.In this study,a new method using precast steel reinforced concrete(PSRC)panels is developed.To demonstrate its effectiveness,numerical studies are conducted to investigate and compare the collapse behavior of a structure without retrofitting,retrofitted with a constructional RC frame,and retrofitted with external PSRC walls(PSRCW).Sophisticated finite element models(FEM)were developed and nonlinear time history analyses were carried out.The results show that the existing masonry building is severely damaged under occasional earthquakes,and totally collapsed under rare earthquakes.Both retrofitting techniques improve the seismic performance of existing masonry buildings.However,it is found that several occasional earthquakes caused collapse or partial collapse of the building retrofitted with the constructional RC frame,while the one retrofitted by the proposed PSRC wall system survives even under rare earthquakes.The effectiveness of the proposed retrofitting method on existing masonry buildings is thus fully demonstrated.

Analytical study of performance evaluation for seismic retrofitting of reinforced concrete building using 3D dynamic nonlinear finite element analysis

This paper presents three-dimensional finite element （FE） analyses of an all-frame model of a three-story reinforced concrete （RC） building damaged in the 1999 Taiwan Chi-Chi Earthquake. Non-structural brick walls of the building acted as a seismic resistant element although their contributions were neglected in the design. Hence, the entire structure of a typical frame was modeled and static and dynamic nonlinear analyses were conducted to evaluate the contributions of the brick walls. However, the results of the analyses were considerably overestimated due to coarse mesh discretizations, which were unavoidable due to limited computer resources. This study corrects the overestimations by modifying （1） the tensile strengths and （2） shear stiffness reduction factors of concrete and brick. The results indicate that brick walls improve frame strength although shear failures are caused in columns shortened by spandrel walls. Then, the effectiveness of three types of seismic retrofits is evaluated. The maximum drift of the first floor is reduced by 89.3%, 94.8%, and 27.5% by Steel-confined, FuI1-RC, and Full-brick models, respectively. Finally, feasibility analyses of models with soils were conducted. The analyses indicated that the soils elongate the natural period of building models although no significant differences were observed.

Potential of GSHP coupled with PV systems for retrofitting urban areas in different European climates based on archetypes definition

According to the recent policies regarding energy use in buildings and the need of retrofit strategies,the aim of this work is to support policies concerning the installation of ground source heat exchangers in urban and historical areas,raising the awareness on the potential energy saving achievable with optimal sizing and limited impact on the urban environment.Archetypes have been developed distinguishing among existing and historic buildings,focusing on single-family terrace houses,which are the typical residential buildings in European historic centres.A methodology for the optimal sizing of ground source heat pumps,eventually considering dual-source system or air system has been developed combining simulations of a photovoltaic system to estimate the self-sufficiency and the self-consumption for five orientations of the building.Extreme results have been obtained for warm cli-mates,with negligible heating energy demand and possibly free cooling systems rather than traditional cooling systems needed in wintertime.Penalty temperature was acceptable despite unbalanced energy demands.With proper inclination,photovoltaic systems could provide up to 40%of self-sufficiency share also in northern cli-mates.An energy-economic analysis was carried out obtaining a variety of cases representing a general overview of the European building stock and the potential benefits achievable in terms of renewable energy share,energy savings and economic investments needed to be extended to simulations at urban scale.

Characterization of housing stock for energy retrofitting purposes in Spain

Energy saving in existing buildings is of vital importance.In this work,the characterization of housing stock in Spain for energy retrofitting purposes has been performed.The regulations in force when the existing stock was constructed(1980–2007)were considered to model the envelope and thermal systems of single-family and block housing.Building energy consumption and CO_(2) emissions were estimated for each type of dwelling and location,ranging from 44.2 to 130.6 kWh/(m^(2)·year)(13.6–32 kg CO_(2)/(m^(2)·year))for multi-family homes,and 85.5 to 213.5 kWh/(m^(2)·year)(17.1–45.2 kg CO_(2)/(m^(2)·year))for single-family homes.A global picture of the energy performance and emissions for 13 different climate zones was obtained with a total of 504 simulations.Retrofitting of the envelope allowed the reduction of consumption and emissions from 37.7%to 58%,depending on the climate zone.Energy consumption per square meter in block housing was lower than in single-family housing;nevertheless,single-family houses responded more effectively to energy improvement actions.Finally,non-renewable primary energy savings seem a better indicator of the improvement by retrofitting than the energy label.The building models designed in this work may serve as a reference for subsequent research concerning energy retrofitting and energy savings of housing stock.

Assessment of seismic retrofitting interventions in reinforced concrete structures

Destruction of reinforced concrete(RC)structures,particularly non-ductile RC structures,in recent earthquakes demonstrate their vulnerability under lateral forces generated in an earthquake.Despite the extensive literature on the subject and the wide variety of strengthening techniques available,there is no consensus on the efficiency of these techniques in improving the seismic performance of RC structures.In this study,a five-storeyed RCframed building is considered to evaluate its seismic performance through static non-linear pushover analysis.To examine the effect of various cases encountered in practice,the pushover analysis is carried out on the RC frame for various cases,i.e.a bare RC frame,an RC frame with masonry infills but with an open ground storey,and RC frames with shear walls with a variety of thicknesses and steel reinforcement ratios.Further,to investigate the effect of retrofitting,the RC frame is strengthened using local jacketing and bracings.From the results,it is observed that the initial stiffness and base shear of masonry infilled RC frame with an open ground storey exhibit an increase of 2.6%,and 19%,respectively,as compared to the bare frame.The use of shear walls increases the initial stiffness and base shears,and they increase by 6–14%and 8–20%,respectively,with an increase in the reinforcement ratio in the shear wall.Retrofitting with the use of both diagonal bracings causes the base shear to increase by a factor of 7.7 as compared to that of the open ground storey.Finally,the probability of damage to the RC frame in all cases was compared using seismic fragility curves.

Retrofitting low-performance units to abate sewer overflow pollution based on mathematical model and Sobol algorithm

Optimal retrofit of low-performance units(LPUs)is promising to abate overflow pollutant mass loading of sewer systems during wet-weathers.This study presents a combination of mathematical model and Sobol algorithm to help identify LPUs of sewer systems and design retrofitting strategies.Therefore,the solution to minimize the overflow pollutant mass loading from sewers systems can be efficiently obtained.The developed method was demonstrated at a catchment served by one wastewater treatment plant in the Chaohu City,Anhui Province of China,with five pumping stations and a total sewer length of 58.3 km.Within the catchment,there are three rivers and a small lake to receive overflows from the sewer system.Among them,one river that was mostly polluted was selected as the object of overflow pollution abatement during wet weather period.After identifying the LPUs of the sewer system and developing retrofitting strategies using Sobol sequence,the mitigation of overflow pollution during wet weather period was analyzed.Results show that the mass loading of chemical oxygen demand(COD)discharged into the target river could be reduced by 40.6%,by implementing optimal retrofit strategy of LPUs,i.e.,increasing the conveyance capacities of two pumping stations by 2.5–3.2 times and augmenting the diameters of 12 sewers by 1.25–1.29 times.To further coordinate the abatement of overflow pollution and retrofit investment,Sobol sensitivity analysis was conducted to screen the dominant LPUs to update the optimal retrofit strategy.By applying the updated strategy,the overflow COD mass loading per overflow event was close to that of non-updated strategy,while the retrofitting length of sewers was reduced by 40%.Therefore,on the basis of the presented method,decision-makers can flexibly develop retrofitting strategies of sewer system to abate overflow pollution during wet weathers in a cost-effective way.

A pragmatic retrofitting approach to enhancing the thermal,energy and economic performance of an educational building:a case study in Malaysia

Building retrofit procedures play a crucial role in improving the energy performance and economic indicators of a building.In this context,an energy audit is typically recommended,but it is seldom used as a comprehensive approach due to the complexity and associated costs.This article aims to conduct a holistic energy audit approach for a university building in Malaysia,with the objective of diagnosing energy efficiency deficiencies,identifying areas of energy waste and proposing practical retrofit measures accordingly.The approach involved multiple stages,including measurements,surveys and simulation work.Eight energy-saving measures were proposed,targeting improvements in envelope elements,cooling and lighting systems,and operation and control.The Design-Builder software was utilized for energy simulation,assessing the annual energy savings.Economic evaluation indices,such as net present value and simple payback period,were used to assess the economic feasibility of the measures.The results demonstrated significant potential for energy reduction,with each measure achieving annual energy reductions ranging from 2%to 18%,and a cumulative im-pact of 41%on annual energy consumption when combined.The investment payback period for the energy-saving measures varied from 0.8 to 8.9 years,with a payback period of 3.9 years for the combined energy-saving measures.Furthermore,the net present value was positive,indicating the economic feasibility of investing in the proposed energy-saving measures.These findings provide valu-able energy-saving opportunities that can be applied to improve similar buildings on the university campus.

Seismic retrofitting of severely damaged RC connections made with recycled concrete using CFRP sheets

An experimental and numerical program is carried out in this research to investigate the influence of CFRP sheets on the cyclic behavior of unconfined connections made with recycled concrete.Cement is partially replaced by silica fume,iron flling and pulverised fuel ash using two different percentages:15%and 20%.Each specimen is partially loaded at the first stage and then specimens are repaired using CFRP sheets.The repaired specimens are then laterally loaded until failure.In addition,a finite element model is built in ABAQUS and verfed using the experimental results.The experimental results have shown that the repaired specimens have regained almost double the capacity of the un-repaired specimens and hence the adopted repair configuration is recommended for retroftting seismically vulnerable RC connections.Increasing cement replacement percentage by silica fume,fuel ash or iron flling from 15%to 20%has reduced joint carrying capacity and weakened the joint.It is recommended using 15%pulverised fuel ash or silica fume as cement partial replacement to enhance the strength and ultimate drift of beam-column joints under cyclic loading.Iron filling concrete is also recommended but the enhancement is relatively less than that found with pulverised fuel ash concrete and silica fume concrete.

Retrofitting with vegetation recent building heritage applying a design tool--the case study of a school building

Severaf researches show the environmental and microclfmatic benefits of the （ntegration of vegetation in architecture; however the potentialities of vertical and horizontal greening systems to retrofit buildings are still not much investigated. The retrofitting project of the Barsanti Institute of Camogli （Genoa, Italy） is presented, a building dated back to the sixties with serious architectural and efficiency problems, located in a considerable Landscape area. The development and application of a design tool （process tree）, for horizontal and vertical greened surfaces, allows to evaluate the potentialities of vegetation to retrofit and to relate the encountered efficiency problems and the climate characteristics with the choice of plant species, system, and technology more suitable for the specific situation （of which environ- mental and economic impact are also evaluated） and to define a design approach for the systematic consideration of the many parameters involved. ~ 2013. Higher Education Press Limited Company. Production and hosting by Elsevier B.V. All rights reserved.