Retrofitting and Strengthening of Structures

Analytical seismic responses of structures retrofitted using base isolation devices are investigated and the retrofit schemes are illustrated. The retrofitting of various important structures using seismic isolation technique by incorporation of the layers of isolators at suitable locations is studied. Three specific structures such as historical buildings, bridges, and liquid storage tanks are selected to investigate the effectiveness of the base isolation in seismic retrofitting. Different types of isolation devices, such as elastomeric bearings and sliding systems are evaluated for their performance in the retrofitting works. The response of the retrofitted structural system is obtained numerically by solving the governing equations of motion under different earthquakes and compared with the corresponding conventional structure without any retrofit measures, in order to investigate the effectiveness of base isolation in retrofitting of structures. It is observed that the seismic response of the retrofitted structures reduces significantly in comparison with the conventional structures depicting effectiveness of the retrofitting done through the base isolation technique. This paper also distinctively elaborates on the methods of construction in retrofitting works involving base isolation.

Wind loads are a major threat for old corroded steel structures constructed near the sea where wind speeds can be very high. This paper presents a case study of a wind-induced failure analysis of an existing steel structure and the proposed retrofitting methods. The examined steel structure was constructed in the 1970s in Syros, Greece and is currently operating as an athletic centre. The first part of this study presents the wind-induced failure analysis, from which a domino effect is documented. A corroded bracing that was buckled due to wind load governs the reduction of vertical load carrying of the steel structure and creates an asymmetry under horizontal loading before a number of other steel members failed due to buckling. To understand the structure’s performance, failure analysis, as well as time history and incremental dynamic analysis, were performed. The second part of this paper presents the proposed retrofitting methods for improving the vertical load carrying capacity under wind loads. The goal was to improve the load-carrying capacity of the structure so as to comply with current design European codes. In addition, enhancement of the dynamic properties of the strengthened structure was demonstrated using modal analyses. The structural behaviour was determined in a more precise manner via non-linear wind time-history and incremental static analyses. The analytical results explain the development of failures in the existing structure.

A state-of-art of traditional and modern retrofitting techniques emphasizing the advantage of the use of metallic materials. General issues of structural intervention starting from the mechanical causes of damage, the logical phases of intervention, the technical and administrative steps and different levels of consolidation are shortly over viewed. The main characteristics of the new strategies for anti-seismic protection of buildings are presented.

Many existing reinforced concrete structures were constructed with substandard
characteristics. Low quality concrete, poor transverse reinforcement details and insufficient flexural
strength are among the most common deficiencies. While substandard structures are in need of
retrofitting, particularly in seismic areas, problems such as high costs and disturbance to occupants
are major obstacles for retrofit interventions. Fiber reinforced polymers can provide feasible retrofit
solutions with minimum disturbance to occupants. In this study, the basic aim is to investigate the
flexural seismic performance of substandard reinforced concrete columns retrofitted with embedded
longitudinal fiber reinforced polymer reinforcement without increasing the original dimensions
of the columns. In the experimental study, the reference and retrofitted columns were tested
under constant vertical and reversed cyclic lateral loads. Three different connection methods of
aramid fiber reinforced polymer reinforcement to the footing were investigated experimentally. A
significant enhancement was obtained in lateral flexural strength through the proposed retrofitting
method. Furthermore, it was observed that the cyclic lateral drift capacities of the retrofitted
columns were as high as 3%, which can be deemed as quite satisfactory against seismic actions. The
comparison of the experimental data with analytical calculations revealed that a conventional design
approach assuming composite action between concrete and fiber reinforced polymer reinforcement
can be used for flexural retrofit design. Experimental results also demonstrated that strain limit for
longitudinal fiber reinforced polymer (FRP) reinforcement should be remarkably lower in case of
reversed cyclic loading conditions.

Engineers are often overwhelmed with laborious work while analyzing bearing capacity and settlement behaviour of shallow foundations. This is largely due to the number of iterations required under various empirical design considerations. To mollify this challenge, an effort is made in this research to develop a spreadsheet-based solution that can effectively, accurately and timely resolve bearing capacity and settlement problems of shallow foundations. The Microsoft excel (2010) package was used to develop a user-friendly, accessible, economical and analytical program to evaluate settlement and ultimate bearing capacity problems. It offers user-controlled parameter panels while the analysis and calculations are done automatically. A sample question was adopted, manual calculations were made, and a comprehensive Microsoft excel spreadsheet was developed. The spreadsheet analysis template was based on Terzaghi’s method for the ultimate bearing capacity and Gazeta’s method for the settlement analysis for different shape of footings under varying water levels for the same sample question.  Comparisons were made to see the variation between the manual calculation and the Microsoft Excel spreadsheet that was developed. The difference between the manual calculation and the Microsoft Excel spreadsheet in the bearing capacity analysis is less than 0.50kN/m2 which is within an acceptable range and in the settlement analysis, there is no significant difference between the Microsoft excel spreadsheet and the manual calculation for all the footing types.

Strengtheningandrepairingofreinforcedconcretebeamsbyusingthinfibersconcretejacket have many advantages such as increasing of ultimate load, enhancement of serviceability limit state, resistance to fire and avoiding of corrosion problems that appear in steel plate jacket. The present work conducted to study the strengthening and repairing of reinforced concrete beams subjected to short time repeated load by using mixed steel fibers concrete jacket (MSFCJ). For this purpose fourteen reinforced concrete beams have a cross section 120×300 mm, totallength 2300 mm were fabricated and tested under three point load. The used concrete mix contains two mixed shape steel fibers, corrugated and end-hooked steel fibers.Twoofthesebeamswerefabricatedwithoutstrengthening,thefirstwastestedunder static load up to failure and the second was tested under short time repeated loads up to failure. The rest twelve beams, six of them were strengthened by U-shape MSFCJ with variousthicknessandsteelfiberscontentwhiletheothersixbeamswereloadedupto0.5the ultimate static load and then repaired using MSFCJ. The twelve beams were tested under shorttimerepeatedload.Thetestsresultsshowedtheeffectivenessoftheproposedtechnique inbothultimateandserviceabilitylimitstate.

Ujjayanta Palace, standing in the heart of Agartala city, in Tripura, a famous royal house, covering an area of 1 sq. km. and styled in Greek sculpture, was built by Maharaja Radhakishore Manikaya in 1901. The two-storeyed palace has a mixed architecture with three high domes (the center one being 26 m high). Ujjayanta Palace, a declared heritage building, has been in existence for the past 110 years and the environmental effects have taken their toll. A detailed survey of the existing structure and the surrounding soil strata was made. The properties of the building materials were assessed using modern techniques. The soil was found to be prone to liquefaction in the event of an earthquake. It was decided to carry out extensive retrofitting of the palace without in any way altering its architectural features. The criteria adopted for undertaking the retrofitting was to permit the structure to undergo deformation without brittle failure or loss of life during design basis earthquake and to limit the damage to minor repairable cracks when the structure was subjected to maximum considered earthquake. In this paper, details of the assessment of the palace structure and the environment are presented. Further, a comprehensive description of the retrofitting techniques adopted and their efficacy are explained.

—The current paper presents a structural assessment and proposals for retrofit of the National Youth Foundation Building, an existing reinforced concrete (RC) building in the city of Igoumenitsa, Greece. The building is scheduled to be renovated in order to create a Municipal Cultural Center. The bearing capacity and structural integrity have been investigated in relation to the provisions and requirements of the Greek Retrofitting Code (KAN.EPE.) and European Standards (Eurocodes). The capacity of the existing concrete structure that makes up the two central buildings in the complex (buildings II and IV) has been evaluated both in its present form and after including several proposed architectural interventions. The structural system consists of spatial frames of columns and beams that have been simulated using beam elements. Some RC elements of the buildings have been strengthened in the past by means of concrete jacketing and have had cracks sealed with epoxy injections. Static-nonlinear analysis (Pushover) has been used to assess the seismic performance of the two structures with regard to performance level B1 from KAN.EPE. Retrofitting scenarios are proposed for the two buildings, including type Λ steel bracings and placement of concrete shear walls in the transverse direction in order to achieve the design-specification deformation in each applicable situation, improve the seismic performance, and reduce the number of interventions required.

ABSTRACT: The general topic investigated in this thesis is “structural health monitoring”, with special care being devoted to damage detection and localization. The study is focused on methods which work in the space of the observed variables, where the global information measures can be used to detect the damage. In this context damage detection is demanded to global measures such as entropy or Lyapunov exponents. The comparison of these measures computed in subspaces of the observed variables or in their expansions, allows one to perform a sort of sensitivity analysis on the role of the variables involved in the problem.
Such global measures are able to detect but not to directly  localize damage. For this purpose, a new approach to detect and localize the damage is formulated and implemented. It exploits response surface techniques to approximate the relationship among the observed variables. Comparing the resulting models in different damaged and undamaged situations identifies the response differences and their causes.
The response surface procedure is described from its basic theoretical aspects up to the features of its numerical implementation. Additionally, the global measures introduced above drive the analyst in establishing whether or not the problem is well posed, i.e., whether or not the set of measured quantities are able to detect the specific damage to be localized.
The validation of the proposed methodology is first numerically pursued by applying it to the benchmark case set up by the Structural Health Monitoring Panel of the American Society of Civil Engineering (ASCE). The procedure is then tested on two different experimental situations. While the first study of a three-dimensional steel frame reproduces the features of the benchmark problem, the second investigation covers a monumental structure situation, where damage is represented by more or less extended cracks in the masonry. The potential expressed by the procedure also in this second application seems to promise interesting exploitation possibilities.

Timber load bearing floor structures of Italian historical constructions are complex systems made of girders, joists, subfloor, and completing components (lath to cover planking joints, small boards to cover the link between joists and girders, etc.). These floors are placed in and connected with the load bearing walls, thus constituting a more complex structural system.
The need of strengthening of timber load bearing floors could issue from: timber decay (due to insects, fungi, fire, or creep), increase in loads, changes in safety and serviceability standards.
Actual cases show countless states with regard to: building techniques; material state of preservation; size of the gap between required and provided performances; aesthetical, historical and material interest of ceiling and flooring.
In the light of contemporary architectural preservation theories, several values must be considered while choosing from among the conceivable systems for the strengthening of timber floors: aesthetical quality; signs of usage; technological features; material characteristics. Other needs must also be evaluated along with those values: the requirement to assure physical and aesthetical fruition of the building; the need to respect the original technological conception of the structure; the compatibility of the strengthening solutions with the existing structure, the possibility to remove it, and maintain it in efficiency; moreover the added elements should be clearly recognisable as contemporary.
This paper aims to single out the primary values to be considered, and to assess the most common strengthening solutions with regard to these aspects and to the actual state of the floor structure.

The major earthquake on April 25, 2015 (7.8 Mw) and the aftershock on May 12, 2015 (7.3 Mw) caused severe damages on Kathmandu University (KU) Library. Disaster prevention of the library building is necessary to restore its strength and
reduce seismic risk. Retrofitting approach can be employed to strengthen the building and increase its seismic capacity. Seismic retrofit is an effective technique by which the building can be strengthened to improve its seismic performance without affecting its aesthetics value and architectural identity. To achieve public safety by considering use of various materials and structural stability, retrofitting is economically applied to meet functional and structural requirements of the building. This pro-active disaster mitigation technique has been effective in modifying the existing structure for strengthening to improve its structural performance.

To improve the behavior of the connection between the roof and the masonry walls, reinforced concrete ring-beams were commonly used in these last years. This technique have proved to be effective, but, at the same time, the different properties of concrete and masonry require an adequate connection to the underlying masonry and the additional mass added on the top of the building may have negative effects when the building is subjected to seismic loading. To avoid such shortcomings a possible solution could be the use of masonry ring-beams reinforced with composites. After an analysis of the behavior of this new structural solution, the results of a first set of experimental tests will be presented and discussed. Finally, a first application of a FRP masonry ring-beam will be illustrated.

— in the present study, the steel jacketing technique with variable vertical angles size connected with horizontal steel straps is used to upgrade the load carrying capacity of rectangular reinforced concrete columns under eccentric loads. Seventeen reinforced concrete rectangular columns were loaded and tested under different eccentricities until failure. Each column has 120x160 mm cross section and 1000 mm length with four normal mild steel bars 8 mm diameter as a vertical reinforcement and 6 mm diameter horizontal normal mild steel (stirrups) with 120 mm spacing. Five columns non-strengthened were tested under different eccentricities (e/t = 0, 6.25 %, 12.50 %, 18.75 % and 25.00 %) as control columns. However, twelve columns were divided into three groups strengthened with two external angles 20x20x2 mm, 40x40x2 mm and 60x60x2 mm in compression side respectively and two external angles 20x20x2 mm in tension side for all strengthened columns. The strengthened columns were tested under different eccentricities (e/t = 6.25 %, 12.50 %, 18.75 % and 25.00 %). Numerical analysis using the finite element technique has been conducted to simulate the response of control and strengthened columns. A finite element commercial package "ANSYS version 15" is used in the present analysis. The results of the finite element model have fair agreement with the experimental results. The validated finite element model was used to conduct parametric analysis for practical design applications. Columns with cross sectional areas ranging from (25x30) cm to (25x120) cm; strengthened with different angles size subjected to eccentricity (e/t) 10% , 20% and 30% were investigated. The columns were 300 cm in height and have vertical reinforcement 1 % of the concrete cross sectional area; 8 mm stirrups spaced at 20 cm were provided for all columns. The columns were strengthened using 2 vertical angles of different size in tension side and 2 vertical angles of different size in compression side welded by horizontal straps 50 cm apart. The dimensions and thicknesses of the angles were identified for each column according the needed level of strengthening. Each column is strengthened to reach the original column carrying capacity. The results showed that increasing the covered area of the steel jacket as well as increasing cross sectional area of the steel angles increases the load carrying capacity of the strengthened columns. The relationships between the strengthened columns and the corresponding dimensions of the angles are presented in tables for practical applications.

This article presents a concise overview on condition monitoring and retrofitting/ strengthening of structures including a practical case study of strengthening for an existing historical building. Condition assessment of an existing structure is required mainly to check serviceability and safety requirements of the structure after short term events like earthquake or long term degradation of the structure with time. It is carried out to assess the ability of a structure to perform its intended operations under changed loading conditions with time or modification in its structural system as per newly imposed requirements. The condition assessment and strengthening may also be required for integrated extension of an existing structure. After assessing the condition of the structure, either it is retrofitted (or  strengthened) or it is demolished according to the severity of the damage. In this article, such a critical condition assessment for an existing historical masonry building is presented and appropriate strengthening schemes are suggested by following two separate measures (concrete jacketing and fiber reinforced polymer strengthening). Subsequently, the relative advantages and disadvantages of the strengthening measures are discussed from a practical engineering perspective. Aim of this article is not to propose any new method for condition assessment and strengthening of structures, rather we take a systematic approach to demonstrate our experience. Critical case studies on condition assessment and strengthening of historical buildings with adequate technical insights are very scarce to find in scientific literature. This article would serve as a valuable reference for the practicing engineers and the concerned scientific community.

Sustainability has become a fundamental requirement for the future of our cities.
This requirement is mostly associated with environmental issues, and a great effort has been made in the past years to build a low-carbon society. However, sustainability must also be associated with safety.
As a consequence, in seismic countries, sustainable cities must be not only low-carbon-emitting bust also earthquake-safe.
This concept represents the basic premise of this book.
According to this premise, in earthquake-prone nations like Italy—where most of the building stock is both highly earthquake-vulnerable and energy-consuming—energy renovation actions should be combined with seismic upgrades. Nevertheless, many barriers significantly limit the real possibility of undertaking combined retrofit measures, especially in the case of multi-owner housing and high-rise buildings. These barriers are of different kinds: economic/financial (high renovation costs, insufficient incentives and subsidies, landlord-tenant dilemmas, etc.), technical (ineffectiveness of conventional upgrade solutions, need of regulatory simplification, etc.), organizational (occupants’ dislocation and disruption, consensus to the retrofit expenditure by condominium ownerships, excessive time for getting construction permits, etc.), and cultural/social (insufficient information and skills, lack of adequate policy measures for promoting renovation actions).
This book aims to overcome these barriers and to bridge the gap between sustainability and safety, so to conserve both human and environmental resources. It brings together 11 contributions on different seismic and energy renovation measures, proposing technical solutions at district, building, and component level, for both historic and modern case studies.
Finally, I would like to thank the editorial team of Sustainability for inviting me to guest-edit the Special Issue on “Energy and Seismic Renovation Strategies for Sustainable Cities” which has been transformed into this book. I also thank all the authors and reviewers for their fundamental contributions.

This article presents a concise overview on condition monitoring and retrofitting/ strengthening of structures including a practical case study of strengthening for an existing historical building. Condition assessment of an existing structure is required mainly to check serviceability and safety requirements of the structure after short term events like earthquake or long term degradation of the structure with time. It is carried out to assess the ability of a structure to perform its intended operations under changed loading conditions with time or modification in its structural system as per newly imposed requirements. The condition assessment and strengthening may also be required for integrated extension of an existing structure. After assessing the condition of the structure, either it is retrofitted (or strengthened) or it is demolished according to the severity of the damage. In this article, such a critical condition assessment for an existing historical masonry building is presented and appropriate strengthening schemes are suggested by following two separate measures (concrete jacketing and fiber reinforced polymer strengthening). Subsequently, the relative advantages and disadvantages of the strengthening measures are discussed from a practical engineering perspective. Aim of this article is not to propose any new method for condition assessment and strengthening of structures, rather we take a systematic approach to demonstrate our experience. Critical case studies on condition assessment and strengthening of historical buildings with adequate technical insights are very scarce to find in scientific literature. This article would serve as a valuable reference for the practicing engineers and the concerned scientific community.

The objective of the study is to evaluate the effect of
using silica fume on the properties of fresh and hardened
concrete made with crushed bricks through experimental
investigation. The effect of using silica fume on the workability of concrete due to addition of silica fume was measured by taking the slump of the concrete produced with and without silica fume. The strengths and stiffness were experimentally determined for the hardened concrete. For the hardened concrete, cylinders and prisms of standard dimensions were cast for a particular mix ratio at constant water cement (W/C) ratio with and without adding silica fume. The casted specimens were tested for determining the tensile, compressive and flexural strength of concrete made with crushed bricks as coarse aggregate. From the investigation, it has been found that the workability, strength and modulus of elasticity of concrete increases with the addition of silica fume. It has also been found from the investigation that the enhancement effect using silica fume increases with the age of concrete.

Six reinforced concrete rectangular columns with a cross section 120x160 mm and 800 mm length were casted and tested until failure. Two control columns were tested under axial load and four columns were tested under different eccentricities e/t= (6.30%, 12.5%, 18.75% and 25%). All specimens were retrofitted by replacing the loose concrete part by grout mortar. Strengthening was carried out using four vertical steel angles, two angles 30x30x3mm in eccentricity direction and two angles 15x15x3 mm in the reverse direction all wrapped with expanded three plies steel wire mesh. However, the steel wire mesh jacket was injected by cement mortar. The test results showed that columns strengthened with four vertical steel angles wrapped with three plies steel wire mesh tested under different eccentricity recorded a higher failure load than that wrapped with three plies steel wire mesh only. The increase in column carrying capacity ranged from 102.5% to 112%.
Keywords: Column; Eccentricity; Retrofitting; Strengthened; Jacket; Wire mesh;

A B S T R A C T Wildfires impact upon populations where development has occurred within or adjacent to natural vegetation. Even with extensive management interventions in the landscape, wildfires will continue to impact upon some properties. Residents in wildfire prone areas need to prepare themselves and their properties. Studies have found cost is one of the main reasons there is a generally low level of preparation by residents. In this study, we quantify the cost for residents to prepare themselves and retrofit their property for wildfire in an intermix and interface community. We combine this with semi-structured interviews to identify limitations to preparedness and willingness to contribute to a shared cost scheme with local government. Wide variation in the level of preparedness was found for the five case study homes in the intermix area and the five in the interface area with intermix houses being better prepared than those at the interface. All buildings were found not to comply with any building standards for wildfire resilience, despite most being considered to have the highest level of wildfire exposure. The total up-fronts cost to prepare residents and their homes ranged from approximately $8500 to $47,000 with an average of $24,600. Based on these figures, the financial investment required was significantly higher than residents felt they were able to cover. Ultimately, the choice to live in a wildfire-prone area will always involve the acceptance of some risk, regardless of the construction of the property and preparedness of the household.

The research project deals with the historical development of timber structures and with the study of techniques for their preservation and strengthening. The interest will be mainly devoted to the architectural heritage built in Italy between the early nineteenth  and mid-twentieth century.
The historical study of timber structures will focus on the influence of developments in: technology for the processing of timber and metals, theories of strength of materials and methods for structural analysis.
The intervention techniques’ study will be carried out through the critical analysis of the currently used techniques and the development of new proposals concordant with the principles of conservation and restoration.

The fundamental period of vibration plays a primary role for the assessment of the seismic demand on structures. It can be evaluated by numerical analyses, or even according to basic formulations provided by building codes for common structural typologies.

Kigali, the capital city of Rwanda is a highly sloped region and the construction of roads to reach all remote areas within the city is economically and socially unfeasible. While the population in this city was increasing on daily basis, the problem with people mobility from remote areas has become a burden to the government. As the construction of new roads all around, especially in areas with that hilly topography is realistically quite expensive, both traffic congestion and long queues of people waiting buses remain daily challenges. This study on aerial cable car as alternative transport mode consisted in identification of areas with more mobility problems, analysis of respective topography and proposal of adequate lines. The review of available literature, sites exploration and interview with local people were performed. As results, five metro-cable lines were proposed and respective coordinates (elevation, location, USR, NISR) were collected using GPS. Research established that the system would be cost effective and technically feasible, as the more loaded Line C would cost 14,503,242,000 Rwf (around 14.2M Euro). Also, this transport mode was found to be sustainable as the construction cost of the line C would be covered just after 10 months of its operation.

The premature failure problem of  beams strengthened with external plates reduces  its  efficiency.  Although  this  problem  is considered  in  different experimental and analytical studies, more effort is required to increase the efficiency  of  such  expensive  strengthening  technique.  As  part  of  a comprehensive  program,  this  experimental  study  i s  applied  on  eleven continuous  reinforced  concrete  (R .C )  beams  and  nine  full -scale  simply supported R.C beams. The effect of using different materials and schemes for  external  reinforcing  was  investigated  on  the  overall  behavior  of  the strengthened  beams.  Behavior  of  beams  strengthened  with  the  proposed  schemes was  explored  considering  its practicality and cost of strengthening. The  ultimate load  of the tested beams were compared with the design load
calculated using the ACI 440-02 guidelines for external flexure and shear
strengthening of beams. Generally,  controlling the shear cracks propagation by using web plates and  reducing stress concentration and crack propagation along  the  strengthening  plate  delays  the premature  mode  of  failure and correspondingly  enhances  significantly the strengthened  beam’s  capacity and ductility.  Due to their significant  effect, different common  strengthening schemes need to be considered in any proposed design guidelines for more economic and reliable applications.

An experimental study is presented in this paper on the behaviour of square R. C. columns of size 750 × 150 × 150 mm retrofitted with Glass fibre reinforced polymer (GFRP) sheets along with a brief review of literature. One column without GFRP and four columns complete wrapped with one, two, three and four layers of GFRP sheets have been tested for axial loading. The failure axial loads and failure modes of the columns have also been observed. A critical discussion is made with respect to increase in the strength of retrofitted columns with respect to the column without GFRP in order to explore the optimal use of GFRP for strengthening the R. C. columns. Further, an analytical model of RC column retrofitted with externally bonded FRP has also been proposed in compatibility with IS: 456-2000 [1] as the design guidelines on strengthening/retrofitting of concrete structures using externally bonded FRP laminates/sheets are yet to be recommended in India. The experimental ultimate load carrying capacity of columns is also compared with that of the respective columns predicted from the present analytical model and literature.

The main objective of the present study is the assessment and retrofit of an existing road bridge that is located in Cyprus over the river Kouris. In particular the study concerns in a road bridge with seven spans of 10.5 m + 5 * 12.6 m + 10.5 m, a cross section width of 7.10 m and a 5 m piers height that was constructed in the early 50's. The structural system of the bridge comprises of cast in situ reinforced concrete T-beams and slab deck that is simply supported on masonry piers. According to the new urban plan to design the bridge should now accommodate two lanes per direction, a pedestrian walkway and a cycling lane with total cross section width of new deck 15.60 m. The deck of the bridge widened using for aesthetic reasons the same cross section type and the new T-Beams and slab deck connected monolithically to the existing one. The existing part of the deck was strengthened with reinforced concrete jacketing due to inadequacy in shear resistance. Major challenge of the project posed the existing masonry pier layout that was insufficient to carry the new design seismic forces. New piers, founded on piles, were designed adjacent to the existing piers in order to support the new widened part of the bridge, and also to bear all the horizontal loads arising from the masses of the total deck. Sliding bearings (free movement) placed in the part of the bridge over the existing piers and elastomeric bearings with movement only in the longitudinal direction placed in the new piers.

The climate changes that have been occurring for a long time have not only left an impact on the earth's environment but also on the built heritage of mankind. Just as man is adapting to the climate changes therefore it is important that his heritage too should be sustainable. Heritage in the form of buildings is what connects with humans the most and hence requires saving. But a question then arises is, will not the adaptations, work against the historic character of the built heritage? To answer this question the essay will delve into the justifications for retrofitting a historic traditional building.

This study presents an experimental–analytical investigation on the structural behavior of precast prestressed hollow core RC slabs strengthened in flexure by CFRP laminates. Externally bonded and near surface mounted (NSM) laminates were used. The CFRP area and using transverse anchorage were also
investigated. Results demonstrated that NSM technique resulted in optimum strengthening efficiency. The increased bond strength also resulted in full activation of the NSM laminates at failure. However, the NSM flexural strengthening level should be carefully designed to avoid unfavorable shear-tension failure mode. Moderate efficiency was associated with the externally bonded technique due to the premature de-bonding. However, this efficiency was optimized by using transverse CFRP laminates as anchorage, which re-directed de-bonding further away from the laminates’ ends and delayed failure, but at much lower deformations than those of the control slab. A rational analytical study was conducted. Comparisons between the experimental and analytical results demonstrated satisfactory agreements.

This article has been written by C. Nuti, S. Santini, D. Lavorato, B. Briseghella, Z. Zhou, J. Xue, using the tests and the analysis that I made during the research period spent at the SIBERC (Sustainable and Innovative Bridges Engineering Research Center) at the University of Fuzhou, Fujian Province, China.

A rapid repair and seismic upgrade solution for reinforced concrete (rc) bridges designed according to Chinese code (JTG D60-2004 [1], JTG D62-2004 [2] and JTG/T B02-01-2008) but with insufficient transversal steel reinforcement, damaged by a strong earthquake, is proposed and tested. This solution is an upgrade of the one tested with very good results during a previous research (Lavorato et al.) on bridge designed according to old Italian
code (‘86)  without proper seismic details. In particular some improvements are given for damaged rebar substitution. Cyclic tests are carried out on pier specimens (in scale 1:6) of the
most stressed pier of the Chinese rc bridge at Fuzhou University lab (China) to evaluate the effectiveness of the proposed repair technique. These specimens have been built simulating
the substitution of the damaged portions of the rebars using rebar turned at the pier base to have a smaller diameter. The turned rebar ensures the concentration of the plasticity at the
base of the pier. A C-FRP wrapping is applied to increase the insufficient shear strength and guarantee the necessary ductility in the plastic hinge sections. Different turned rebar
configurations are considered to optimize the intervention.

The main objective of the present study is the assessment and retrofit of an existing reinforced concrete building. In particular, the study concerns the municipal theater of the city of Volos, Greece and it was carried out following the provisions and requirements of the Greek Retrofitting Code (KAN.EPE.), which adopts the Performance Based Design (PBD) concept. The theater was built during the 70s and was designed according to the Greek Royal Decrees of 1954 and 1959. The theater consists of the stage and the auditorium, which were analyzed independently, because they constitute two disjoint reinforced concrete (RC) structures. Their structural system consists of spatial frames and shear walls. The columns and the beams are simulated with beam elements with concentrated plasticity and the shear walls with equivalent diagonal truss elements which simulate the shear behavior of the wall structural element. Nonlinear static (Pushover) analysis is applied in order to estimate the seismic performance of the two structures for two performance objectives (A2 and B1 according to the provisions of KAN.EPE.). These correspond to the “Operational” and “Life Safety” performance levels for seismic hazard levels with a 50% and 10% probability of exceedance in 50 years, respectively. A retrofitting scenario is proposed for both the stage and the auditorium in order for the performance objectives to be met. It includes concrete jacketing of certain beams, columns and shear walls as well as strengthening of specific beams with fiber-reinforced polymers (FRPs).

This paper aims at presenting an in situ experimental test campaign carried out on one existing traditional masonry building abandoned after the 1998 Azores (Portugal) earthquake. For testing purposes, an experimental test setup was developed and used to characterize the out-of-plane behaviour of sacco stone façade walls. The test setup was composed of a self-equilibrated airbags’ system, which is used to apply out-of-plane quasi-static surface loads in three specimens under distinct conditions: original (non-retrofitted), retrofitted and strengthened. The obtained results are presented and briefly discussed and compared, namely regarding hysteretic behaviour, maximum strength and energy dissipation capacity. Finally, a brief discussion about the effectiveness of the retrofitting and/or strengthening solutions is also included.

The present case study investigates the capacity assessment and subsequent strengthening of pre-stressed concrete girders and provides additional information on the strengthening measures taken for the whole of the structure involved. It is based on an existing concrete building constructed in 1971. Structural modifications had to be made to ensure a proposed load-bearing capacity upgrade due to change of use.
    The building contains concrete girders pre-stressed with the post-tensioning method, the mechanical and geometric properties of which were not available, although it was known that the two-span girders were intended to meet high-capacity demands. Nonetheless, an accurate simulation of the structure was essential. For this purpose, non-destructive methods had to be employed, while safety factors were introduced in accordance with the corresponding code provisions, in order to minimize structural uncertainties. Subsequently, finite element models were created to evaluate the response of the structure under the new loading conditions, and the necessary modifications were proposed.

Abstrak Salah satu persyaratan penting untuk konstruksi tahan gempa yang terkait dengan pengekangan adalah pemasangan tulangan pengekang dengan kait gempa 135 0 pada sengkang. Dalam pelaksanaannya banyak pelaksana konstruksi menggunakan tulangan pengekang dengan kait 90 0 atau dengan konfigurasi dobel C (tidak sesuai standar). Berdasarkan beberapa hasil penelitian dan beberapa catatan dari kejadian gempa di Indonesia akhir-akhir ini, pemasangan tulangan pengekang yang tidak sesuai standar untuk kolom beton bertulang menghasilkan kinerja yang buruk sebagai struktur tahan gempa. Makalah ini memaparkan hasil eksperimen yang bertujuan mengembangkan elemen tambahan (pen-binder) untuk meningkatkan efektivitas pengekangan kolom beton dengan tulangan pengekang yang tidak sesuai standar. Efektivitas dari tambahan elemen untuk meningkatkan kinerja pengekangan pada beberapa konfigurasi tulangan pengekang yang tidak standar ini diuji dengan beban aksial dan lateral siklis. Benda uji berjumlah 5 buah kolom, dimensi penampang 260 mm x 260 mm dan tinggi 1500 mm. Variabel pengujian adalah jenis material pen-binder,level beban aksial dan sudut kait yang digunakan dalam tulangan pengekang. Hasil pengujian menunjukkan bahwa modifikasi terhadap tulangan pengekang tidak standar efektif mengekang inti beton, meningkatkan daktilitas dan kemampuan disipasi energi kolom benda uji. Kata-kata Kunci: Kolom, tulangan pengekang, pen-binder. Abstract One of the important requirements for earthquake resistant buildings associated with confinement is the use of seismic hook (135-degree hook) in hoop. Therefore, in practice many construction workers use confining reinforcement 90-degree hook or with double C configuration (code non-compliance). Based on some research and some records of recent earthquakes in Indonesia, the use of the code non-compliance confining reinforcement for reinforced concrete columns can result in structures with poor seismic performance. This paper presents the results of experimental study with an objective to develop an additional element (pen-binder) expected to improve the effectiveness of concrete columns confined with non-compliance confining reinforcement. The effectiveness of this additional element in improving the performance of some configuration of non-compliance confining reinforcement in columns under axial and lateral cyclic loading was investigated in this study.The specimens tested in the study were 5 column specimens, with 260 mm x 260 mm in cross section and 1500 mm in height. The test variables were types of pen-binder material, level of axial load, angle of hook applied. The test results indicate that confining reinforcement modification can be effective in confining the core concrete, improving ductility and dissipation energy of column specimens.

Haussmann buildings architecture spread throughout the city of Paris. Nevertheless, those buildings are nowadays submitted to heavy operations of use change, conservation and rehabilitation, justified by several reasons, among others are building aging and the increasing demand for hotel rooms in Paris. In this paper, concrete pouring, an underpinning construction technique applied to a Haussmann building complex to create an additional basement floor is described. This description is the result of a construction survey realized during a heavy rehabilitation operation which takes place between 2015 and 2017 in a Haussmann complex located at La Madeleine. This work aims at providing contributions for a better understanding of concrete pouring technique, complementary an evaluation of the risks associated with this technique is done. The knowledge from this work could be very useful for the study of underpinning numerical modeling techniques or issues related to sustainable rehabilitation and strengthening, aiming to preserve this important building heritage or similar ones existing in other countries.

The objective of this study is to investigate the effectiveness of an innovative technique for strengthening masonry arches at their intrados, based on the use of carbon plates. Although FRP sheets or strips are successfully used as strengthening elements for this kind of application, they present several critical issues that can compromise these upgrading works, leading to the local collapse mechanism, which corresponds to the debonding of reinforcement from the masonry substrate. As an alternative to FRP sheets, the use of FRP plates presents instead several interesting aspects which make them very attractive for intrados strengthening. More precisely, FRP plates have an inherent bending and axial stiffness that may overcome problems concerning premature peeling. Fifteen prototypes of brickwork arches strengthened at their intrados with GFRP sheets or CFRP plates were tested under a monotonic vertical load applied at the keystone. The influence of the types of reinforcement (glass fibers and carbon plates), properties of the bonding system and masonry substrate and the presence of anchor spikes has been investigated.

Steel greenhouse structures are generally constructed by individual sole contractors using quick empirical structural calculations (pre-engineered solutions). It is also common to import standard greenhouses from other countries, mainly from the Netherlands, Italy, and France, and sometimes from Great Britain and Israel. Evidently, these countries differ concerning the local wind and snow conditions. Therefore, there is a need for a better design of structures accepted as satisfactory, while installation can be done in a different location. Many greenhouse structures incorporating poor designs or inappropriate pre-engineered solutions are currently in use. At the same time, demolition and reconstruction represent a very expensive solution considering the loss of crop production and the demolition and construction costs; thus, strengthening is a reasonable alternative. This paper presents strengthening techniques for steel greenhouses that are code-deficient according to EN 13031 and Eurocodes. Consequently, two case studies are presented as typical applications of greenhouse structure strengthening.

Pressure vessels are one of the most important equipment in the refining of the crude oil. For this reason, these equipment must resist against the loads resulting from the earthquake.
Pressure vessels are found in different units of refineries and in different vertical and horizontal shapes. These equipment are located on different foundations and their seismic behavior are quite different. For seismic study of pressure vessels, at first this equipment must be screened and categorized in order to find their real behavior. The selected sample should be one that in comparison to others must have critical condition in terms of seismic vulnerabilities. According to the qualitative studies, mechanical specifications such as dimensions, temperature, weight, and the dimensions of the foundation will be determined. After analytical modeling and calculations the amount of vessel vulnerabilities will be found. All the modeling is done with the SAP2000 and SAFE2000 software. For modal and spectrum dynamic analysis shell elements and frame elements is used. After the analysis is done, the stresses and the displacement in the body of vessel and also stresses in pedestal and bolts will be determined and then it will be compared to the allowable values. At the end those elements which do not have adequate strength, will be retrofitted and all drawing and details will be presented.

The use of composites in the field of architectural restoration is becoming more and more widespread, because of the great technical advantages they convey in many cases. But applying these materials to the Cultural Heritage poses not only technical issues, common to all the applications on the same materials, but also artistic, historical and, more generally, cultural ones. The present paper faces these issues, starting with some considerations on how they were dealt with in history, when the “new” materials were iron, steel and reinforced concrete. Then, the specific problems posed by the composite materials are discussed and some examples are shown in order to identify the correct approach to the many different cases that can arouse in the field of architectural restoration. There isn’t a single right solution for each problem, but there is a right approach that starts from the comprehension of the building’s behavior, passes through a comparison of all the possible solutions and aims at finding the best equilibrium among the technical and theoretical issues for the single case study.

One of the important requirements for earthquake resistant buildings associated with confinement is the use of seismic hook in hoop or confining reinforcement for r/c column elements. However, installation of confining reinforcement with 135 0 hook is not easy. Therefore, in practice many construction workers apply confining reinforcement with 90 0 hook (non-code compliance). Based on some research and some records of recent earthquakes in Indonesia, the use of the code non-compliance confining reinforcement for reinforced concrete columns produced structures with poor seismic performance. This paper presents a study to develop an additional element expected to improve the effectiveness of concrete columns confined with non-compliance confining reinforcement. The additional element, named pen-binder, is used to hold the non-compliance confining reinforcement at its place. The effectiveness of this element under pure axial concentric loading was comprehensively investigated. The specimens tested in the study were 18 column specimens, with 170 mm x 170 mm in cross section and 480 mm in height. The main test variables were the material type of pen-binder, angle of hook applied and configurations of confining reinforcement. The test results indicated that adding the pen-binders can improve the strength and ductility of column specimens confined with non-compliance confining reinforcement.

The lack of knowledge of structural behaviour often led to their substitution with modern structures, or to invasive strengthening operations. If ignorance was the first cause of this loss, knowledge is the first goal to be reached. In unfavourable environmental conditions wood can undergo rapid decay, thus it is necessary a monitoring plan. The theories of preventive conservation underline the need to reaffirm the maintenance practices, and modern technologies could help to lower the cost and increase effectiveness of this operations. In absence of decay processes, historic structures are still suitable to carry out their bearing function. However the need to prevent damage due to exceptional loads, the increase of loads, or the progress of decay could lead to the necessity of strengthening. Strengthening must be viewed as a part of the discipline of restoration, thus it must aim to the conservation of the structure in its material and immaterial features.

Masonry structures have been preferred for centuries in most of the countries across the world because they are easy to build and economical due to the use of local materials in their construction. As a result of high usage volume, masonry structures that created the architectural section of history and culture constitute an important part of the current building stock despite the developing and diversified construction techniques nowadays. The protection of these structures, which are important both in terms of their cultural values and their transfer to future generations, is of great importance in the architectural point of view. For this purpose, a masonry structure from Foca is selected. The material properties and architectural plan of the structure are determined in accordance with the original one. The structure is modelled by using a software program under seismic effects. Displacement and stress values for each acceleration record are obtained. Besides, an evaluation is made in the direction of the analysis results and it is determined according to the seismic performance of the structure. After that, the structure is retrofitted according to the current design codes and without distorting the architectural perspective. This study aims to increase the structural strength of the case building by using conventional and modern techniques for the recovery of the structure.

Abstract— An experimental study was performed to investigate the behavior and strength of proposed technique to connect reinforced concrete (RC) beam to steel or composite columns. This approach can practically be used in several types of building construction. In this technique, the main beam of the frame consists of a transfer part (part of beam; Tr.P) and a common reinforcement concrete beam. The transfer part of the beam is connected to the column, whereas the rest of the beam is connected to the transfer part from each side. Four full-scale beam-column connections were tested under static loading. The test parameters were the length of the transfer part and the column properties. The test results show that using of the transfer part technique leads to modify the deformation capabilities for the RC beam and hence it increases its resistance against failure. Increase in length of the transfer part did not necessarily indicate an enhanced behavior. The test results contribute to the characterization of the connection behavior between RC beam - steel column and can be used to calibrate numerical models for the simulation of this type of connection.
Keywords— composite column, reinforced concrete beam, Steel Column, Transfer Part.

An experimental campaign has been described to evaluate the effectiveness of including remedial wall ties as an intervention technique (CemenTie and Dryfix from HELIFIX®) used in the retrofitting of hollowed fired clay brick masonry building facades. Initially an experimental campaign was undertaken to carry out tests on 120 isolated specimens using some post and some pre NP EN 771-1 [1] clay bricks. A second campaign was carried out on wallettes built with dimensions of 1.20 by 1.20 m in order to represent a more realistic situation and evaluate slippage effects of the retrofitting solutions. Thus, this experimental work aimed to: i) assess the retrofitting technique in the laboratory environment; ii) to evaluate the efficiency of the retrofitting solution on specimens represented by post and pre NP EN 771-1 [1] clay bricks; iii) evaluate the influence of different features of the retrofitting technique (sleeve introduction and grout injection) over the pull-out test results; and iv) describe and catalogue the types of failure and behaviour of both techniques. All results for both retrofitting techniques are thoroughly presented and discussed.

Moderate and severe earthquakes have struck different places in the world, causing severe damage to reinforced concrete structures. Retrofitting the existing structures is one of the major challenges to face. One of the retrofit techniques of RC structural members is confinement with a composite enclosure. This external confinement of concrete by high strength Carbon Fibre Reinforced Polymer composites can significantly enhance the strength and ductility and will result in large energy absorption capacity of structural members. Beam-column joints, being the lateral and vertical load resisting members in framed RC structures are more vulnerable to failures during earthquakes and hence strengthening of the joints is often, the key to achieve successful seismic retrofit strategy.This paper depicts experimental investigations carried on RC frames subjected to broad band excitation, which are conducted to study the performance of wrapping on retrofit effects on it & the influence of Carbon Fibre Reinforced Polymer wrapping on aseismic performance of RC Frame. Wrapping is done externally at beam-column joints. For this purpose, a single bay three storied scaled down RC frame is subjected to dynamic loads under broadband excitation using servo-controlled hydraulic actuator, till  model frame fails & this failed frame is strengthened by using Carbon Fibre Reinforced Polymer. The retrofit frame is subjected to the same intensity of dynamic excitation, till it fails. The uni-axial accelerometers is used at various storeys to quantify the absolute accelerations and the extent of its decay. The above investigations conducted on the RC frame revealed the performance of the retrofit measure adopted as diagnostic alternates.

Well-reported  experimental  data  and  field  records  have  indicted  importance  of incorporating  nonlinear  characteristics  into  the  analysis  of  reinforced  concrete  (R.C) coupled shear walls (CSW).  In this research work m aterial nonlinearity of both concrete and reinforcement is taken into account throughout the finite element analysis.  This model verification is undertaken for symmetrical coupled shear wall then the  effect of the degree of unsymmetry  of the CSW on its behaviour  is investigated.  Based on the verified model, the nonlinearity of different coupled R.C. systems having various infill stiffening schemes is explored. 

Structural system stiffening using infill masonry  wall panels between columns has been modelled  and  compared  versus  the  case  of  coupled  shear  wall  (CSW).  Simulation  of column strengthening by jacketing to convert t he frame system into CSW system with hybrid  properties  is  also  investigated.  Finally, the  case  of  coupled  shear  walls  (CSW) supported on columns is studied.  The results have revealed the nonlinear nature of such composite systems  which should be incorporated in rigorous design procedures.

Rapid increasing of population and limited city area as well as better awareness on the green open area of the city, which is ideally about 30 percent, have forced the development of the buildings vertically. The increasing number of high-rise buildings and skyscrapers are the evidence that the development of the buildings in the cities of Indonesia are heading towards the over-ground space. However, the vertical development is known to be highly vulnerable to earthquake hazard. The revised Indonesian seismic map has increased the seismic load in most of the seismic zones in Indonesia. To create a safe and healthy city, a comprehensive urban planning and design is required. A good urban planning and code-based design must also be adopted to assure a safe building structure for the dwellers. This study is intended to observe the possibility of using alternative materials to improve the performance of the existing buildings which have not followed the existing earthquake-resistant building code through the implementation of Fiber Reinforced Polymer (FRP) wrap on structural members. The strength and ductility enhancements of the columns retrofitted with external confinement using FRP are found when compared with the unconfined control column. The results indicated that the maximum loads of each confined columns have increased by 33.52, 54.97, 36.61, and 40.73 percent, respectively, for columns C-1G, C-1C, C-1RC, and C-1RG. The ductility of columns C-1C and C-1G have increased by 122.73 and 53.30 percent, but decreased by 15.24 and 66.31 for columns C-1RG and C-1RC when compared with the unconfined control column C-1, respectively. This is due to the unintended premature failure at the upper end of the column C-1G and an indication that the secondary fiber direction which was placed vertically has contributed to the longitudinal steel of C-1RC in increasing its capacity.