Strengthening and Retrofitting of Motín de Oro II Bridge in Mexico

This chapter presents the studies conducted to retrofit an existing bridge in a seismic prone area of Mexico. The Motín de Oro II Bridge was built in the 1970s with a continuous box girder superstructure and wall-type substructure. From the 1970s to nowadays, the design truck loads in Mexico have been substantially incremented and many bridges built in that period have required to be evaluated and, in some cases, rehabilitated and retrofitted. Firstly, the study presents the results of visual inspections of all parts of the bridge and a description of the preliminary studies conducted to determine the material properties, to evaluate the river flow characteristics and to calculate the scour depth. Secondly, the chapter discusses the initial structural analyses of the bridge subjected to the original gravitational and seismic loads and to the current loads before the intervention. These analyses allow to select the structural elements that require to be retrofitted and the best strategy to follow. Finally, the study presents results of the numerical retrofitted model and the experimental assessment of the dynamic properties based on ambient vibration measurements. Additionally, the scour protection and the general construction procedure are also described.

Strengthening and Modernization of a Characteristic Masonry Building in Vienna, Austria

Historical buildings from the period of Promoterism constructed between 1850 and 1910, called “Gründezeitgebäude,” represent a main part of the building stock in Vienna. A typical building from this period is presented, along with the pathology of such buildings. A step-by-step strengthening and modernization strategy is described, including structural analysis data and design of sections data before and after interventions, along with detailing according to the respective codes.

Seismic Rehabilitation of a School Building in Cephalonia, Greece

<p>The 2014 earthquake sequence in Cephalonia, Greece, resulted in a number of structural failures. In Argostoli, the capital of the island, a school building suffered light damage; however, the structural assessment following the analysis procedures of the recently published Greek Code for Structural Interventions, showed that seismic strengthening is required. The structure was built on the aftermath of the catastrophic 1953 Ionian earthquake sequence based on older code requirements, which are much outdated, as indicated from the results of both modal response spectrum analyses and non-linear static analyses. The retrofit aims to increase the very low structural capacity of the building and as a means for that the use of concrete jackets is selected. Based on the results of the assessment, it was decided that concrete jackets should be applied to all columns, while large structural walls running along the transversal direction were strengthened with single-sided reinforced concrete jacketing. The interventions are limited by architectural demands and cost considerations. However, analyses of the strengthened structure show that the interventions improve its seismic behaviour adequately. The detailing of interventions is thoroughly presented. What makes this case study interesting is the unusual structural system of the building, which is an ingenious combination of frame elements and lightly reinforced concrete walls and its behaviour to one of the strongest recent Greek earthquakes. The rehabilitation study had to model correctly the structure and propose interventions that were in agreement with the architectural demands and the cost consideration.</p>

Modification and Strengthening of a Characteristic Reinforced Concrete Building in Patras, Greece

<p>The design and application of strengthening measures aiming to effectively counter possible weaknesses related to the extensive architectural modification of a characteristic reinforced concrete building is discussed in this chapter. Several balconies were removed as part of the architectural interventions. Externally bonded reinforcement consisting of steel and fibre reinforced polymer laminates was applied as an “answer” to possible changes in flexural stress of selected structural elements in the immediate area of the demolitions. A unique anchorage system was also designed and applied as an answer to the loss of development length of the main reinforcement bars of selected beams due to the removal of their cantilever parts.</p>

Retrofitting of School Building Located in Southern Italy

<p>This paper summarizes the main features of the seismic retrofitting project of a school building located in Montella (AV), Italy. Specifically, it describes the as-built status in terms of structural organization, member detailing, and existing materials properties. Then, it outlines the main assumptions and results obtained from seismic analysis, of both as-built and retrofitted structure. Comments about the construction stage are also reported by describing the main operations put in place with the aim to realize the shear wall system, which is the main retrofitting intervention, and some local strengthening measures consisting in steel plating and jacketing of some underdesigned RC members. Some emphasis is placed on the realization of micro-piles and extra foundations of the aforementioned shear walls. Besides its specific interest, the reported project may be intended as representative of a wide class of seismic assessment and retrofitting projects that have been realized in Italy in the last decade.</p>

Seismic Strengthening of the Majestic Centre, Wellington, New Zealand

<p>The Majestic Centre is a 30-storey office tower in the centre of Wellington, New Zealand. The structure has a dual lateral system (reinforced concrete (RC) moment frame + shear cores) and hollow-core floors. The building’s assessed seismic performance was found to be below expected levels, leading to a strengthening exercise. Over a period of 5 years, the structures performance was raised to meet current seismic loading requirements, at a cost of €50M.</p>

Seismic Performance Assessment, Retrofitting and Loss Estimation of an Existing Non-Engineered Building in Nepal

<p>The non-engineered building built before 2004 remained after Gorkha earthquake although such structures demonstrate seismic deficient. Therefore, the present study aims to carry out detail seismic performance of such building to investigate as-built seismic performance and its performance after intervention of retrofit measures. Two in situ tests were performed, which includes Schmidt hammer test and ambient vibration test. The adaptive pushover analysis and dynamic time history analyses were performed for as-built and retrofitted building. The retrofit measures increase the stiffness and maximum base shear capacity of the buildings. In addition, such retrofit measures improved single storey drift concentration in existing building such that uniform drift profile can be attained. Furthermore, the probability of exceeding damage states can be significantly reduced and mainly found to be more effective in minimizing higher damage states, such as partial collapse and collapse states. The maximum expected annual loss occurs between 0.1 g and 0.2 g PGA (Peak Ground Acceleration). It was revealed that the steel braced building was found to be relatively more effective in enhancing the seismic performance, whereas reinforced concrete shear wall found more economic feasible retrofit measure for this particular building.</p>

Christchurch Town Hall Complex: Post-Earthquake Ground Improvement, Structural Repair, and Seismic Retrofit

<p>The Christchurch Town Hall (CTH) complex contains six reinforced concrete buildings constructed circa 1970 in Christchurch, New Zealand (NZ). The complex is used for performing arts and entertainment, with an Auditorium that is internationally recognized for its acoustics. It is listed as a Grade-1 heritage building due to its cultural and historical significance. Unfortunately, the CTH foundation system was not originally designed to accommodate liquefaction-induced differential settlement and lateral spreading effects, as highlighted by the 2010–2011 Canterbury earthquake sequence. Although the most extreme ground motions exceeded the NZS 1170.5 code-defined 1/2500 year earthquake loads, the CTH structures performed remarkably well for a design that pre-dated modern seismic codes. Most of the observed structural damage was a result of the differential ground deformations, rather than in response to inertial forces. The post-earthquake observations and signs of distress are presented herein. The primary focus of this paper is to describe two major features of the seismic retrofit project (initiated in 2013) which were required to upgrade the CTH complex to meet 100% of current NZS 1170.5 seismic loadings. Firstly, the upgrade required extensive ground improvement and a new reinforce concrete mat slab to mitigate the impacts future ground deformations. Soil stabilization was provided by a cellular arrangement of jet-grout columns, a relatively new technique to NZ at the time. The new mat slab (typically 600-900 mm) was constructed over the stabilized soils. Secondly, upgrading the superstructure had many constraints that were overcome via a performance-based design approach, using non-linear time-history analysis. Recognizing the heritage significance, the superstructure “resurrection” as a modern building was hidden within the original skin minimized disruption of heritage fabric. Retrofit solutions were targeted, which also minimized the overall works. The 2015–2019 construction phase is briefly discussed within, including jet-grout procedures and sequencing considerations.</p>

Thorndon Container Wharf: Temporary Works for Recovery of Container Operations (New Zealand)

<p>The Thorndon Container Wharf sustained severe damage in the November 2016 M7.8 Kaikoura earthquake. Substantialworks, of a temporary nature, were required to restore thewharf for container handling operations. The temporary securing works included gravel columns within the reclamation fill and restraining and underpinning of the wharf. All of these works were designed and constructed over a 9-month period to provide a temporary facility for container handling operations for a period of up to 3 years. The temporary securingworks were required to secure the container cranes, maintain support to the wharf structure, and ensure the reclamation behind the wharf had sufficient strength to support lateral loads imposed by the restraining system. This was to enable container operations to recommence and to maintain business continuity, pending action on replacement or reinstatement of the container wharf. This paper outlines the development of the design of the temporary works to secure and return to operations a 125- m working length of wharf and reclamation.</p>