• Earthquakes and Structures
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• v.8 no.3
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• pp.801-820
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• 2015

The seismic sequence which hit the Northern Italian territory in 2012 produced extensive damage to reinforced concrete (RC) precast buildings typically adopted as industrial facilities. The considered damaged buildings are constituted by one-storey precast structures with RC columns connected to the ground by means of isolated socket foundations. The roof structural layout is composed of pre-stressed RC beams supporting pre-stressed RC floor elements, both designed as simply supported beams. The observed damage pattern, already highlighted in previous earthquakes, is mainly related to insufficient connection strength and ductility or to the absence of mechanical devices, being the connections designed neglecting seismic loads or neglecting displacement and rotation compatibility between adjacent elements. Following the vulnerabilities emerged in past seismic events, the paper investigates the seismic performance of industrial facilities typical of the Italian territory. The European building code seismic assessment methodologies are presented and discussed, as well as the retrofit interventions required to achieve an appropriate level of seismic capacity. The assessment procedure and retrofit solutions are applied to a selected case study.

• Computers and Concrete
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• v.22 no.4
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• pp.383-393
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• 2018

Infill wall strengthening method has been widely used for seismic strengthening of deteriorated reinforced concrete (RC) frame structures with non-seismic details. Although such infill wall method can ensure sufficient lateral strengths of RC frame structures deteriorated in seismic performances with a low constructional cost, it generally requires quite cumbersome construction works due to its complex connection details between an infill wall and existing RC frame. In this study, an advanced seismic strengthening method using externally-anchored precast wall panels (EPCW) was developed to overcome the disadvantage inherent in the existing infill wall strengthening method. A total of four RC frame specimens were carefully designed and fabricated. Cyclic loading tests were then conducted to examine seismic performances of RC frame specimens strengthened using the EPCW method. Two specimens were fully strengthened using stocky precast wall panels with different connection details while one specimen was strengthened only in column perimeter with slender precast wall panels. Test results showed that the strength, stiffness, and energy dissipation capacity of RC frame specimens strengthened by EPCWs were improved compared to control frame specimens without strengthening.

• Earthquakes and Structures
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• v.12 no.3
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• pp.359-374
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• 2017

The seismic events in Northern Italy, May 2012, have revealed the seismic vulnerability of typical Italian precast industrial buildings. The aim of this paper is to present a seismic fragility model for Italian RC precast buildings, to be used in earthquake loss estimation and seismic risk assessment by comparing two building typologies and three different codes: D.M. 3-03-1975, D.M. 16-01-1996 and current Italian building code that has been released in 2008. Based on geometric characteristics and design procedure applied, ten different building classes were identified. A Monte Carlo simulation was performed for each building class in order to generate the building stock used for the development of fragility curves trough analytical method. The probabilistic distributions of geometry were mainly obtained from data collected from 650 field surveys, while the material properties were deduced from the code in place at the time of construction or from expert opinion. The structures were modelled in 2D frameworks; since the past seismic events have identified the beam-column connection as the weakest element of precast buildings, two different modelling solutions were adopted to develop fragility curves: a simple model with post processing required to detect connection collapse and an innovative modelling solution able to reproduce the real behaviour of the connection during the analysis. Fragility curves were derived using both nonlinear static and dynamic analysis.

• Steel and Composite Structures
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• v.21 no.4
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• pp.805-827
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• 2016

A new type of precast CFST column to RC beam braced frame is proposed in this paper. A series of shake table tests were conducted to excite a one-third scale six-story model for investigating the global seismic performance of this type of structure against earthquake actions. Particular emphasis was given to its dynamic property, global seismic responses and failure path. Correspondingly, a numerical model built on the basis of fiber-beam-element model, multi-layer shell model and element-deactivation method was developed to simulate the seismic performance of the prototype structure. Numerical results were compared with the measured values from shake table tests to verify the validity and reliability of the numerical model. The results demonstrated that the proposed novel precast CFST column to RC beam braced frame performs excellently under strong earthquake excitations; the "strong CFST column-weak RC beam" and "strong connection-weak member" anti-seismic design principles can be easily achieved; the maximum deflections of precast CFSTC-RCB braced frame satisfied the deflection limitations proposed in national code; the numerical model can properly simulate the dynamic property and responses of the precast CFSTC-RCB braced frame that are highly concerned in engineering practice.

• Journal of Korean Association for Spatial Structures
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• v.21 no.4
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• pp.65-72
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• 2021

The Precast concrete(PC) modular structures are a method of assembling pre-fabricated unit modules in the construction site. The essential aim of modular structures is to introduce a connection method that can ensure splicing performance and effectively resist shear strength. This study proposed PC module using a connecting plate that can replace splice sleeves and shear keys used in the conventional PC modular structures. To evaluate the splicing performance and shear capacity of the proposed method, the shear test was conducted by fabricating one monolithic reinforced concrete(RC) beam and two PC modular beams with a shear span-to-depth ratio as variables. The experimental results showed that the shear capacity of the PC modular beam was about 89% compared to that of the RC beam, and showed a failure of the RC beam according to the shear span-to-depth ratio. Therefore, it was considered that the connecting plate effectively transferred the stress between each PC module through the joint and ensure integrity. In addition, the applicability of shear strength equation of ACI 318-19 and Zsutty's equation to PC modular beams were evaluated. Results demonstrated that the improved shear strength equations are needed to consider reduction of shear strength in PC modules.

• Journal of Korean Association for Spatial Structures
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• v.22 no.4
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• pp.81-88
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• 2022

The paper introduces an experimental program for the newly developed vertical joints between Precast Concrete (PC) walls to improve their in-plane shear capacity. Compared to the existing vertical joints, two types of vertical joints were developed by increasing the transverse reinforcement ratio and improving frictional force at the joint interface. A total of four specimens including the Reinforced Concrete (RC) wall and PC walls with developed vertical joints were designed and constructed. The constructed specimens were experimentally investigated through monotonic shear tests. The observed damage, load-deformation relationship, strain and strength are investigated and compared with the cases of RC wall specimen. Experimental results indicate that the maximum force and initial stiffness of the PC wall with proposed vertical joints were decreased by comparing with those of RC wall. However, the ultimate displacement increased by up to 217.30% compared to the RC wall specimen. In addition, brittle failure did not occurred and relatively few cracks and damages occurred.

• Journal of Korean Association for Spatial Structures
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• v.6 no.2 s.20
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• pp.85-92
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• 2006

Precast large panel structures have various connection system such as the horizontal slab-to-wall connection, the vertical wall to wall connection, horizontal slab-to-slab connection, etc. Horizontal connection is connected by vertical tie bars, and vertical joint is connected loop bars and shear keys. The basic function is equalized deformations on later forces and the entire wall panel assembly acts as monolithic actions. Under lateral load some slip occurs in almost vertical connections. The shape and detail of precast connections are very important to the monolithic behavior of overall structures. The paper is a study on the design method and new elasto-plastic analysis of the connections by rigid-bodies spring model.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.45-52
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• 2009

This paper experimentally evaluates the strength characteristics of precast column-R.C. foundation anchor joint subjected to the cyclic horizontal load. The study presents differences in accurate stress transfer path and destruction mechanism between the concrete structural body applying the precast column-R.C. foundation anchor joint and the concrete structural body applying the steel joint. the result from width load experiment on reinforcing steel under the cyclic horizontal load provides the necessary minimum insertion length to construct the precast column-R.C. foundation anchor joint. This study also presents the accurate stress transfer path and destruction mechanism on the anchor joint th meet the customer's requirements, comparing stress transfer path and destruction mechanism provided by the experiment and those provided by the product manual. Eventually, this study presents all the necessary fundamental data to provide the construction design with accurate number of reinforcing steel, diameter of the steel, fixation length of the steel, etc. to build the optimum precast concrete column.

• Earthquakes and Structures
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• v.21 no.6
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• pp.627-639
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• 2021

Fragility curves are being more significant as a useful tool for evaluating the relationship between the earthquake intensity measure and the effects of the engineering demand parameter on the buildings. In this paper, the effect of different site conditions on the vulnerability of the structures was examined through the fragility curves taking into account different strength capacities of the precast columns. Thus, typical existing single-story precast RC industrial buildings which were built in Turkey after the year 2000 were examined. The fragility curves for the three typical existing industrial structures were derived from an analytical approach by performing non-linear dynamic analyses considering three different soil conditions. The Park and Ang damage index was used in order to determine the damage level of the members. The spectral acceleration (Sa) was used as the ground motion parameter in the fragility curves. The results indicate that the fragility curves were derived for the structures vary depending on the site conditions. The damage probability of exceedance values increased from stiff site to soft site for any Sa value. This difference increases in long period in examined buildings. In addition, earthquake demand values were calculated by considering the buildings and site conditions, and the effect of the site class on the building damage was evaluated by considering the Mean Damage Ratio parameter (MDR). Achieving fragility curves and MDR curves as a function of spectral acceleration enables a quick and practical risk assessment in existing buildings.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.168-169
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• 2015

SMART Frame is a composite precast concrete structure system to deliver the advantages of both steel frame and reinforced concrete. Many studies have established to date that SMART Frame is more advantageous than conventional frame-type structure in terms of structural stability, constructability, economic viability as well as reduction of construction schedule. However, such studies have focused primarily on wall-type or flat slab-type apartment housing structures, failing to include Rahmen structures in their scope. Accordingly, this study aims to analyze the benefits of potential application of SMART Frame to RC Rahmen structures. As the structural stability and constructability of SMART Frame is already proven, this study reviews its benefits from the perspective of cost reduction. Conclusion of this study will be used subsequently in predicting the benefits of SMART Frame when it is adapted to RC Rahmen structures.