• Structural Engineering and Mechanics
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• v.89 no.4
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• pp.399-409
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• 2024

Assessment of existing concrete bridges is a challenge for owners. It has greater economic impact when compared to designing new bridges. When using conventional linear analyses, judgment of the engineer is required to understand the behavior of redundant structures after the first element in the structural system reaches its ultimate capacity. The alternative is to use a predictive tool such as advanced nonlinear finite element analyses (ANFEA) to assess the overall structural behavior. This paper proposes a new reliability framework for the assessment of existing bridge structures using ANFEA. A general framework defined in previous works, accounting for material uncertainties and concrete model performance, is adapted to the context of the assessment of existing bridges. A "shifted" reliability problem is defined under the assumption of quasi-deterministic dead load effects. The overall exercise is viewed as a progressive pushover analysis up to structural failure, where the actual safety index is compared at each event to a target reliability index.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.85-95
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• 2015

PURPOSES : Recently, bonded concrete overlay has been used as an alternative solution in concrete pavement rehabilitation since its material properties are similar to those of the existing concrete pavements. Deteriorated concrete pavements need rapid rehabilitation in order to prevent traffic jams on Korean expressways. Moreover, speedy and effective repair methods are required. Therefore, the use of bonded concrete overlay with ultra-rapid hardening cement has increased in an effort to reopen promptly the expressways in Korea. However, mobile mixer is required for ultra-rapid hardening cement concrete mixing in the construction site. The use of mobile mixer causes various disadvantages aforementioned such as limitation of the construction supply, open-air storage of mixing materials, increase in construction cost, and etc. In this study, therefore, hydration accelerator in-situ mixing on polymer modified concrete produced in concrete plant is attempted in order to avoid the disadvantages of existing bonded concrete overlay method using ultra-rapid hardening cement. METHODS : Bonded concrete overlay materials using ultra-rapid hardening cement should be meet all the requirements including structural characteristics, compatibility, durability for field application. Therefore, This study aimed to evaluate the application of hydration accelerator in-situ mixing on polymer modified concrete by evaluating structural characteristics, compatibility, durability and economic efficiency for bonded concrete overlay. RESULTS : Test results of structural characteristics showed that the compressive, flexural strength and bond strength were exceed 21MPa, 3.15MPa and 1.4MPa, respectively, which are the target strengths of four hours age for the purpose of prompt traffic reopening. In addition, tests of compatibility, such as drying shrinkage, coefficient of thermal expansion and modulus of elasticity, and durability (chloride ions penetration resistance, freezing-thawing resistance, scaling resistance, abrasion resistance and crack resistance), showed that the hydration accelerator in-situ mixing on polymer modified concrete were satisfied the required criteria. CONCLUSIONS : It was known that the hydration accelerator in-situ mixing on polymer modified concrete overlay method was applicable for bonded concrete overlay and was a good alternative method to substitute the existing bonded concrete overlay method since structural characteristics, compatibility, durability were satisfied the criteria and its economic efficiency was excellent compare to the existing bonded concrete overlay methods.

• Computers and Concrete
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• v.8 no.3
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• pp.293-309
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• 2011

A long-term structural health monitoring (SHM) system comprising over 700 sensors of sixteen types has been implemented on the Guangzhou Television and Sightseeing Tower (GTST) of 610 m high for real-time monitoring of the structure at both construction and service stages. As part of this sophisticated SHM system, 48 temperature sensors have been deployed at 12 cross-sections of the reinforced concrete inner structure of the GTST to provide on-line monitoring via a wireless data transmission system. In this paper, the differential temperature profiles in the reinforced concrete inner structure of the GTST, which are mainly caused by solar radiation, are recognized from the monitoring data with the purpose of understanding the temperature-induced structural internal forces and deformations. After a careful examination of the pre-classified temperature measurement data obtained under sunny days and non-sunny days, common characteristic of the daily temperature variation is observed from the data acquired in sunny days. Making use of 60-day temperature measurement data obtained in sunny days, statistical patterns of the daily rising temperature and daily descending temperature are synthesized, and temperature distribution models of the reinforced concrete inner structure of the GTST are formulated using linear regression analysis. The developed monitoring-based temperature distribution models will serve as a reliable input for numerical prediction of the temperature-induced deformations and provide a robust basis to facilitate the design and construction of similar structures in consideration of thermal effects.

• Structural Engineering and Mechanics
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• v.39 no.4
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• pp.599-620
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• 2011

The investigation on possible causes of failures related to documented collapses is a complicated issue, primarily due to the scarcity and inadequacy of information available. Although several studies have tried to understand which are the inherent structural deficiencies or circumstances associated to failure of the main structural elements in a reinforced concrete frame, to the authors knowledge a uniform approach for the evaluation building static vulnerability, does not exist yet. This paper investigates, by means of a detailed case study, the potential failure mechanisms of an existing reinforced concrete building. The linear elastic analysis for the three-dimensional building model gives an insight on the working conditions of the structural elements, demonstrating the relevance of a number of structural faults that could sensibly lower the structure's safety margin. Next, the building's bearing capacity is studied by means of parametric nonlinear analysis performed at the element's level. It is seen that, depending on material properties, concrete strength and steel yield stress, the failure hierarchy could be dominated by either brittle or ductile mechanisms.

• Magazine of the Korea Concrete Institute
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• v.7 no.4
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• pp.119-128
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• 1995

This paper summarizes experimental results for studying feasibility and structural behavior of' a half slab which is getting popularity in recent building construction in favour of the savings in manpower, coats, and construction period. 17 specimens were tested to investigate and analyze the flexural strength of precast concrete slab, half slab, and half slab-wall joint. The primary variables of the testing program were: thickness of precast concrete slab, truss mesh shape, and type of loadings. Test results show that the flexural strength of precast concrete slab in reverse loading is lower than the design strength, but the flexural strength of precast concrete slab, half slab and half slab-wall joint in direct loading is higher than the design srength. No horizontal cracks were found in the connection between insitu concrete and precast concrete slab. The flexural strength of half slab and half slab-wall joint was the same as that of reinforced concrete members. This study concludes that there will not be any structural problem in using a half slab reinforced by truss mesh if props spacing of 2.0m-2.5m, cleanness, and rough finishing between precast concrete and insitu concrete slab are kept.

• International Journal of Highway Engineering
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• v.19 no.1
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• pp.37-44
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• 2017

PURPOSES : This study is primarily focused on evaluating the effects of the non-linear stress-strain behavior of RAP concrete on structural response characteristics as is applicable to concrete pavement. METHODS : A 3D FE model was developed by incorporating the actual stress-strain behavior of RAP concrete obtained via flexural strength testing as a material property model to evaluate the effects of the non-linear stress-strain behavior to failure on the maximum stresses in the concrete slab and potential performance prediction results. In addition, a typical linear elastic model was employed to analyze the structural responses for comparison purposes. The analytical results from the FE model incorporating the actual stress-strain behavior of RAP concrete were compared to the corresponding results from the linear elastic FE model. RESULTS : The results indicate that the linear elastic model tends to yield higher predicted maximum stresses in the concrete as compared to those obtained via the actual stress-strain model. Consequently, these higher predicted stresses lead to a difference in potential performance of the concrete pavement containing RAP. CONCLUSIONS : Analysis of the concrete pavement containing RAP demonstrated that an appropriate analytical model using the actual stress-strain characteristics should be employed to calculate the structural responses of RAP concrete pavement instead of simply assuming the concrete to be a linear elastic material.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.3-17
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• 2007

This paper provides an introduction to life-span simulation and numerical approach to support the performance design processes of reinforced concrete structures. An integrated computational system is proposed for life-span simulation of reinforced concrete. Conservation of moisture, carbon dioxide, oxygen, chloride, calcium and momentum is solved with hydration, carbonation, corrosion, ion dissolution. damage evolution and their thermodynamic/mechanical equilibrium. Coupled analysis of mass transport and damage mechanics associated with steel corrosion is presented for structural performance assessment of reinforced concrete. Multi-scale modeling of micro-pore formation and transport phenomena of moisture and ions are mutually linked for predicting the corrosion of reinforcement and volumetric changes. The interaction of crack propagation with corroded gel migration can also be simulated. Two finite element codes. multi-chemo physical simulation code (DuCOM) and nonlinear dynamic code of structural reinforced concrete (COM3) were combined together to form the integrated simulation system. This computational system was verified by the laboratory scale and large scale experiments of damaged reinforced concrete members under static loads, and has been applied to safety and serviceability assessment of existing structures. Based on the damage details predicted by the nonlinear finite element analytical system, the life-span-cost of RC structures including the original construction costs and the repairing costs for possible damage during the service life can be evaluated for design purpose.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.1051-1065
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• 2020

Safety analysis of nuclear power plant (NPP) especially in accident conditions is a basic and necessary issue for applications and commercialization of reactors. Many previous researches and development works have been conducted. However, most achievements focused on the safety reliability of primary pressure system vessels. Few literatures studied the structural safety of huge concrete structures surrounding primary pressure system, especially for the fourth generation NPP which allows existing of through cracks. In this paper, structural safety reliability of concrete structures of HTR-PM in accidental double-ended break of hot gas ducts was studied by Exceedance Probability Method. It was calculated by Monte Carlo approaches applying numerical simulations by Abaqus. Damage parameters were proposed and used to define the property of concrete, which can perfectly describe the crack state of concrete structures. Calculation results indicated that functional failure determined by deterministic safety analysis was decided by the crack resistance capability of containment buildings, whereas the bearing capacity of concrete structures possess a high safety margin. The failure probability of concrete structures during an accident of double-ended break of hot gas ducts will be 31.18%. Adding the consideration the contingency occurrence probability of the accident, probability of functional failure is sufficiently low.

• Structural Engineering and Mechanics
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• v.87 no.6
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• pp.615-624
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• 2023

The focus of this study is on the structural behaviour of reinforced concrete beams in which basalt fiber and SBR latex were added and the cement was partially replaced with 10% of hypo sludge. Eight different mixes of reinforced beam specimens were tested under static loading behaviour. The experiments showed, the structural behaviour with features such as load-deflection relationships, crack pattern, crack propagation, number of crack, crack spacing and moment curvature. A stress-strain relationship to represent the overall behavior of reinforced concrete in tension, which includes the combined effects of cracking and mode of failure along the reinforcement, is proposed. The structural behaviour results of reinforced concrete beams with various types of mix were tested at the age of 28 days. The investigation revealed that the flexural behaviors of hypo sludge reinforced concrete beams with addition of basalt fiber and SBR latex was higher than that of control concrete reinforced beam. The specimen (LHSBFC) with 10% hypo sludge, 0.25% Basalt fiber and 10% SBR latex showed an increase of 5.08% load carrying capacity, 7.6% stiffness, 3.97% ductility, 31.29% energy dissipation when compared to the control concrete beam. The analytical investigation using FEM shows that it was in good agreement with the experimental investigation.

• Structural Monitoring and Maintenance
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• v.10 no.4
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• pp.283-297
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• 2023

This research aims to simulate and investigate the efficiency of strengthening damaged concrete columns using concrete jacketing.The numerical program included unjacketed reference column made of ordinary RC concrete had a cross-sectional dimension of (100×100) mm and 560 mm long reinforced concrete. These cores were damaged by loading them with approximately 60% of their actual ultimate load capacities as a service load. Then, column specimens were strengthened by applying two types of self-compacting concrete SCC jacketing, which were 25 and 30 mm thick, on all four sides. Exposed to external loads at different directions vertically and horizontally simulate to the seismic load. The 3D Finite Element (FE) simulation is used to predict of three structural criteria that were selected and evaluated (deflection, stress, cracks). The results show that the failure of the strengthening columns is interesting and corresponds to the characteristics of the cracks formed in the concrete section,which was documented numerically using 3D Finite Element (FE). A significant improvement of deflection has been noted at the values at the top SECTION of columns compared to the reference sample reaching an average of up to 36.6% when using a 25 mm thick SCC-3500 jacket.