Life Cycle Cost Of Structure Research Articles

Optimization of unmanned aerial vehicle inspection strategy for infrastructure based on model-enabled diagnostics and prognostics

The use of unmanned aerial vehicles (UAVs) for structural health inspection has become a promising technique to perform labor-intensive, accessibility-challenged, and sometimes dangerous inspection tasks. This paper presents a novel physics-informed UAV inspection planning framework for infrastructure structural health assessment based on model-based diagnostics and prognostics enabled by physics-based probabilistic analysis. It bridges the gap between UAV mission planning and inspection with model-based probabilistic analysis, by allowing bidirectional information exchange, namely (1) structural damage state diagnostics using UAV inspection data and (2) UAV inspection optimization through model-based failure prognostics. Based on the bidirectional communication, the impacts of the three key UAV inspection parameters (i.e., inspection distance, inspection interval, and critical maintenance threshold) on structural life-cycle cost are analyzed. The optimization of key UAV inspection parameters is achieved by minimizing the cost per unit time (CPUT) through model-based pre-posterior analysis. In this analysis, synthetic observations are generated using predictive models according to the prior distributions of various uncertainty sources (e.g., detection rate, damage state evolution, etc.). The generated synthetic observations are then used to obtain the posterior distributions of uncertain parameters, enabling the integration of prior information and Bayesian model updating into inspection optimization through a cost function. The proposed model offers a robust method to accommodate the inherent uncertainties in failure prognostics, leading to a more effective optimization of the UAV inspection parameters. The practical application of the framework is demonstrated through a miter gate example. The results show that the proposed method is able to efficiently determine the optimal UAV inspection parameters and continuously update the information model.

Damage localization using electromechanical impedance technique based on inverse implementation

Structural Health Monitoring (SHM) systems allow maintenance planning which reduces maintenance costs. These systems may also allow lifetime extension of structures which allows reduction in lifecycle costs of structures. As a result, SHM systems have been of interest to researchers in civil and mechanical engineering sectors. The SHM system should be ideally low cost, suitable for continuous monitoring, and able to detect small levels of damage. The sensitivity to small levels of damage is even more important for composite structures as composites have low damage tolerance. Electromechanical Impedance (EMI)-based techniques have been proposed due to their sensitivity to low levels of damage. Furthermore, due to their high frequency of operation they are immune to ambient noise. Most of the studies using the EMI technique were limited to damage detection only. Recently some studies have used a network of sensors for EMI measurements and used them for damage localization. This paper follows on this trend of using a network of sensors for damage localization using EMI technique. A novel inverse algorithm is proposed for the damage localization. For the inverse technique, an analytical model for the correlation of distance and angle with the damage index (DI) is developed. This model is then used to generate a database of the DIs for a large number of damage scenarios. The measured DIs from the structure are then compared with this database and the scenario with the least mean error in the DIs is the predicted damage scenario. The algorithm takes into consideration the modeling errors and the measurement errors through regularization and in turn allows more accurate damage localization. The method is applied on different damage scenarios on an unidirectional composite sample. Some sensitivity studies such as the performance of the method using different fits have been carried out. In addition, the accuracy of damage localization of the proposed technique has been compared to a localization technique found in literature. The results show that indeed the proposed algorithm works and improves the damage localization using the EMI technique.

An innovative and efficient multi-generation recycling system for waste concrete subjected to freeze-thaw environment: A theory model and case study

The existing researches on the recycled aggregate concrete (RAC) mainly focus on the recycling of waste concrete used in atmospheric environment, while the ones on the recycling of waste concrete subjected to complex environments are seldom reported. Reusing waste concrete in freeze-thaw (F-T) environment relates to the multi-generation recycling system of “high performance parent concrete-waste concrete-recycled aggregates (RAs)-next generation of recycled high-performance concrete (RHPC)-next generation of RAs”. The efficient operation and sustainability of such recycling system depends on not only the performances of concrete, but also environmental load and economic benefits. The optimal balance between performance, environmental load and economic benefits for recycling waste concrete in F-T environment is generally affected by the performance of parent concrete and quality of RAs in the recycling system. Based on the theories of the emergy analysis and life cycle cost of structure, a sustainable design theory model of this innovative recycling system is proposed. In this model, high performance concrete (HPC) or RHPC is chosen as parent concrete and the performances of middle and low-quality RAs are improved by carbonation treatment method to gain high-quality RAs. The feasibility of the theoretical model is verified by the emergy analysis of the data of three-generation RAC, which provides a theoretical basis for the frost resistance quantitative design of multi-generation recycled concrete.

Optimal design of buildings under wind and earthquake, considering cumulative damage

Modern trends of structural design have implied getting an optimal design, considering performance measurements that take into account both structural and non-structural behavior, as well as the expected annual losses and expected life cycle costs of structures. To make an adequate decision, all relevant variables need to be examined; however, some are often neglected. In this work, a quantitative evaluation of the following variables in the decision-making process is presented: a) the occurrence of two hazards (wind and earthquake) to which the structure is subjected; b) the cumulative structural damage; and c) the downtime during the time the structure is repaired. For such measurement, the optimization analysis of a building is performed. Such building has 28 levels and non-linear viscous energy dissipaters. It is shown the importance of considering the variables mentioned above in the decision-making process.

An efficient approach for LCC-based optimum design of lead-rubber base isolation system via FFD and analysis of variance (ANOVA)

A framework for optimal design of lead rubber bearing (LRB) system is introduced based on the initial and life cycle cost of structures. The purpose of this framework is to minimize the initial and life cycle cost of building and simultaneously improve the seismic performance of the base isolated structure. Endurance time (ET) method is used to predict the seismic response of the building at continuous levels of hazard intensity. Before implementing the optimization process, a full factorial design is utilized, and the seismic performance of a total of 128 lead rubber base isolated structures with varying LRB design parameters is assessed using the ET analysis method. Accordingly, the parameters with the most significant impact on the responses are determined by the analysis of variance. These parameters are used as design variables in a multi-objective genetic algorithm to minimize the initial and life cycle cost of the building with LRB system. The cost analysis of the system requires evaluation of initial costs including the costs associated with the implementation of LRBs. To date, no appropriate cost model has been proposed for LRB systems in the literature; therefore, a simplified cost model for LRBs is developed. Also, a life cycle cost model is used to evaluate the structural performance in the form of economic measures based on the results obtained from the ET analysis. In order to illustrate the method, a prototype six-story building is studied here. According to the results, the proposed approach is found to be effective in reducing the initial and life cycle cost of the building with an acceptable amount of computational effort.

Thermal analysis on self-healing concrete using polyvinyl alcohol

ABSTRACT Self-healing concrete (SHC) is a term that is used for cement-based materials that repair themselves after the material or structure damaged due to some sort of deterioration mechanism. Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair is required. However, these repair works raise the life cycle cost of structure, as they are labour intensive. It can increase the durability and lifetime of the structure. An SHC mix of grade M40 is prepared with super absorbent polymer as a self-healing admixture. The compressive strength of SHC is compared with that of the control concrete. The hydration process in both samples is studied using thermal analysis. Thermo-gravimetric analysis and differential scanning calorimetry test are conducted on hardened paste of both the samples. The effect of polyvinyl alcohol on the degree of hydration is studied.

Study on Regular Inspection Frequency of Bridge Based on Seismic Vulnerability Analysis

This study introduces a method to obtain accurate results regarding bridge seismic cost and reduce structural seismic losses. A three‐span reinforced concrete (RC) continuous bridges model consistent with the reality was established, and seismic vulnerability of the RC bridge was calculated via incremental dynamic analysis combined with local earthquake disaster data. Direct losses from earthquakes are calculated based on local earthquake damage condition, specific maintenance reinforcement methods, and analysis of seismic vulnerability. The indirect economic losses caused by inspection and maintenance are calculated based on local traffic volume. To reduce the effects of bridge aging and deterioration, this paper examines periodic inspection of bridges after earthquakes. By calculating the life cycle cost of structure under different inspection frequencies, the optimal time interval was determined. The results presented for this study can serve as references for the calculation of structural seismic loss and thereby provide the basis for strategies of reducing seismic loss.

The Cost Analysis of Corrosion Protection Solutions for Steel Components in Terms of the Object Life Cycle Cost

Steel materials, due to their numerous advantages - high availability, easiness of processing and possibility of almost any shaping are commonly applied in construction for carrying out basic carrier systems and auxiliary structures. However, the major disadvantage of this material is its high corrosion susceptibility, which depends strictly on the local conditions of the facility and the applied type of corrosion protection system. The paper presents an analysis of life cycle costs of structures installed on bridges used in the road lane conditions. Three anti-corrosion protection systems were considered, analyzing their essential cost components. The possibility of reducing significantly the costs associated with anti-corrosion protection at the stage of steel barriers maintenance over a period of 30 years has been indicated. The possibility of using a new approach based on the life cycle cost estimation in the anti-corrosion protection of steel elements is presented. The relationship between the method of steel barrier protection, the scope of repair, renewal work and costs is shown. The article proposes an optimal solution which, while reducing the cost of maintenance of road infrastructure components in the area of corrosion protection, allows to maintain certain safety standards for steel barriers that are installed on the bridge.

Seismic loss assessment of a structure retrofitted with slit-friction hybrid dampers

In this study a hybrid energy dissipation device is developed by combining a steel slit plate and friction pads to be used for seismic retrofit of structures, and its effectiveness is investigated by comparing the life cycle costs of the structure before and after the retrofit. A hybrid damper is manufactured and is tested under cyclic loading. It is observed that the damper shows stable hysteretic behavior throughout the loading history, and that the cumulative ductility ratio obtained from the experiment far exceeds the limit value required by the AISC Seismic Provisions. The probabilities of reaching various damage states are obtained by fragility analysis to evaluate the margin for safety against earthquakes, and the life cycle costs of the model structures are computed using the PACT (Performance Assessment Calculation Tool). According to the analysis results the slit-friction hybrid damper shows superior performance to the slit damper with the same yield strength for seismic retrofit of structures. The analysis results also show that the probabilities of reaching the limit states are minimized by the seismic retrofit with hybrid dampers combined with increasing column size. The combined seismic retrofit method also results in the lowest repair cost and shortest repair time.

Research on Factors Affecting Reinforced Concrete Durability

Reinforced concrete is widely used in building structures. However, due to its corrosion, deterioration loss is more and more outstanding. Therefore, besides building material mechanical properties and the cost, the structural designer also need to focus on the durability of reinforced concrete. Effects of reinforced concrete durability factors mainly include corrosion of steel in reinforced concrete, freeze-thaw cycle, soft water, high temperature and chemical erosion. Understanding the influencing factors will help control the concrete deterioration, reduce the structural reparation and maintenance costs, and thereby reduce the life cycle cost of structure.

Effectiveness of using tuned-mass dampers in reducing seismic risk

Strong earthquakes cause tangible and intangible seismic losses and disrupt service and function of buildings and infrastructure. The losses could be mitigated by increasing seismic design levels or by installing additional energy dissipation devices, such as tuned-mass dampers (TMDs). Although TMDs are useful for reducing structural responses, their effectiveness in terms of the expected lifecycle cost of buildings including the cost of TMDs, is rarely discussed. A parametric study on the expected lifecycle cost of a building with TMDs is carried out using a two-degree-of-freedom system whose non-linear hysteretic behaviour of the main structure is represented by the Bouc-Wen model. Probabilistic models of seismic demand to structures with TMDs are developed by using 381 ground motion records. The models are employed to assess the expected lifecycle cost of structures with TMDs and to investigate the effectiveness of TMDs in reducing seismic risk. The results indicate that the effectiveness of TMDs decreases as the seismic excitation level increases and its use on occasion could worsen structural performance against earthquake loading. The reduction in the expected damage cost in terms of the initial construction cost by installing TMDs is limited.

Performance-based multi-objective optimization of large steel structures

In recent years, the importance of economical considerations in the field of structures has motivated many researchers to propose new methods for minimizing the initial and life cycle cost of the structures subjected to seismic loading. In this paper, a new framework is presented to solve the performance-based multi-objective optimization problem considering the initial and life cycle cost of large structures. In order to solve this problem, a non-dominated sorting genetic algorithm (NSGA-II) using differential evolution operators is employed to solve the optimization problem, while a specific meta-model is utilized for reducing the number of fitness function evaluations. The required computational time for pushover analysis is decreased by a simple numerical method. The constraints of the optimization problem are based on the FEMA codes. The presented results for application of the proposed framework demonstrate its capability in solving the present complex multi-objective optimization problem.

A Comparative Study on the Flexural Behaviour of One-Way Concrete Slabs Reinforced with GFRP Reinforcements and Conventional Reinforcements when Subjected to Monotonic and Repeated Loading

Over the last couple of decades, the interest in using advanced high performance materials in the construction industry has been shooting up and developing to reduce the overall life-cycle costs of structures. Accordingly, many researches have been carried out to invent new materials which possess the properties comparatively more advantageous than conventional steel reinforcements. Fibre Reinforced Polymer (FRP) reinforcements are considered as new, high tech and ideal materials optimistically used in many countries in the construction field especially in the construction of bridge deck slabs. So many researches have been done to assess the¬ mechanical properties of FRP reinforcements , flexural and shear behaviours of FRP reinforced structural elements under static or monotonic loading. But only limited works have been brought out on the fatigue performance of FRP reinforced structural elements. This paper presents the flexural behaviour of one-way slabs reinforced with Glass Fibre Reinforced Polymer (GFRP) reinforcements (special type of FRP reinforcements) under monotonic loading and two different schemes of repeated loading. A total number of twenty one GFRP reinforced concrete one- way slabs were constructed, out of which seven were tested under monotonic loading, seven were tested under constant amplitude repeated loading and the remaining seven slabs were tested under variable amplitude repeated loading conditions. The behaviour of GFRP reinforced slabs were compared with that of steel reinforced slabs. It has been found that the ultimate load carrying capacities and fatigue performance of GFRP slabs were greater than that of steel slabs. Also there exists a good agreement between the theoretical and experimental results.

Condition, safety and cost profiles for deteriorating structures with emphasis on bridges

After an enormous investment in construction of highway networks undertaken in the second half of the 20th century, the highway networks of most European and North American countries are now completed or close to completion. As a result, the need in funding changed from building new highway structures to repair, rehabilitation, and replacement the existing ones. In this paper, a model for analyzing the evolution in time of probabilistic performance indicators of existing structures, in terms of condition, safety, and cost under no maintenance, preventive maintenance, and essential maintenance, is presented. This model integrates the current practice in bridge management systems based on visual inspections (condition index) with structural assessment (safety index) during the lifetime of existing structures. The proposed model allows the consideration of uncertainties in the performance deterioration process, times of application of maintenance actions, and in the effects of maintenance actions on the condition, safety, and life-cycle cost of structures by defining all parameters involved in the model as random variables. Interaction between condition and safety profiles is defined through probabilistic and deterministic relations. The probabilistic characteristics of the condition, safety, and cost profiles of deteriorating structures are computed by Monte-Carlo simulation. Several realistic examples, based on data on highway bridge components gathered in the United Kingdom, are presented.

Cost-effectiveness in active structural control

The cost-effectiveness of active control of structural systems for protection against seismic hazards is examined. Considerations include uncertainties in the earthquake occurrence and intensity, damage reduction vs control actuator capacity, linear vs nonlinear structural behavior, structural exposure time, discount of cost of future structural failure in present dollar value, and cost of maintenance of control devices. Parametric studies of the expected life cycle cost of structures under seismic loads with and without the control device are carried out and compared for linear systems. The effectiveness of the control is also investigated when the excitation level is high and the structure becomes inelastic. The results show that the effectiveness drops significantly. Expensive, large capacity control devices are generally not cost-justifiable.

On the Economic Estimation of Life Cycle Cost of Structures

Life cycle cost of structure is optimized based on the principles of expected total cost minimum. The optimum second moment safety index is derived from that principle and the expected minimum cost of prospective structure is estimated by proposed method. Structures are going to deteriorate during the service term. The type of deterioration seems generally neither established clearly nor evaluated exactly. In this study, therefore, fractal type deterioration function is applied to obtain the optimum safety index.