Optimization-Based Evolutionary Data Mining Techniques for Structural Health Monitoring

In recent years, data mining technology has been employed to solve various Structural Health Monitoring (SHM) problems as a comprehensive strategy because of its computational capability. Optimization is one the most important functions in Data mining. In an engineering optimization problem, it is not easy to find an exact solution. In this regard, evolutionary techniques have been applied as a part of procedure of achieving the exact solution. Therefore, various metaheuristic algorithms have been developed to solve a variety of engineering optimization problems in SHM. This study presents the most applicable as well as effective evolutionary techniques used in structural damage identification. To this end, a brief overview of metaheuristic techniques is discussed in this paper. Then the most applicable optimization-based algorithms in structural damage identification are presented, i.e. Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Imperialist Competitive Algorithm (ICA) and Ant Colony Optimization (ACO). Some related examples are also detailed in order to indicate the efficiency of these algorithms

Performance of dowel beam-to-column connections for precast concrete systems under seismic loads: A review

Structural connection systems are a major challenge for precast construction systems. A dowel system requires designers to have sound knowledge of the fundamental requirements for seismic loads. In addition, it is important to consider unforeseen impact loads to prevent buildings from collapsing in the event of an earthquake. At present, the available building codes does not offer a complete design and analysis requirements for beam-to-column connection systems. Thus, this article provides researchers with a comprehensive review of the literature of the dowel precast beam-column connections. The key areas covered in this review are as follows: (1) studies on the behaviour of precast dowel beam-column connection systems in earthquake-prone areas; (2) studies on the design and development of precast dowel connection elements; (3) an evaluation of the effect parameters in precast connection systems and (4) a determination of the appropriate precast beam-to-column connections for seismic loads. The strength, ductility, energy dissipation, rotation and plastic hinges of joints in critical regions were considered in order to evaluate the performance of the dowel connection system.</p

Development and testing of hybrid precast concrete beam-to-column connections under cyclic loading

In general, precast concrete structure has insufficient ductility to resist seismic load. Detailed understanding on the behaviour of precast concrete connections are limited and current researches are focused addressing this. In this study, two precast and two monolithic concrete joints for exterior beam-to-column connection were tested under cyclic loading. The installation of precast specimens was prepared using dry type method while the monolithic joints were casted in-situ. The evaluation of seismic performance of the joints was conducted by applying hysteretic reverse cyclic loading until failure. Information regarding the strength, ductility and stiffness properties of the connection were recorded and analysed. Based on the test results and damage condition, the initial design of the joint was improved. Consequently, a new joint was constructed and tested, which exhibited a better performance. Precast concrete connections showed stable load–displacement cycles and dissipated a higher energy. The structural drift obtained was up to 9.0%. Pinching and deterioration were attained at a drift ratio of 4.5%. Also, there was improvement in the tested precast joints based on deflection, plastic hinges, crack pattern and shear deformation. Thus, the precast joints had a satisfactory resistance to seismic loads

Seismic performance of innovative hybrid precast reinforced concrete beam-to-column connections

Precast construction of structural buildings requires connection techniques that can shorten the process using only simple on-site activities while still guaranteeing adequate strength, energy dissipation, stiffness, and ductility. The construction methods should decrease the use of formwork and temporary bracing to save time and costs. In this study, innovative hybrid connections using steel tubes, steel plates, and steel couplers to join beams and columns were proposed and tested under reversed cyclic loading. Five half-scale samples of the hybrid precast joints, including the monolithic and precast joints, were examined to evaluate the seismic performance of the connections. The hybrid connections showed better performance in terms of load, displacement, drift ratio, ductility, strength, stiffness, and energy dissipation compared to a monolithic connection. The drift ratio, moment capacity, strength, and total cumulative energy dissipation of the hybrid connections were higher by 12.5–50.0%, 34.68–59.57%, 35.0–60.0%, and 50.99–331.32%, respectively, when compared with a monolithic connection. The failure modes of the hybrid connections were governed by yielding steel reinforcement, yielding steel plate, and flexural failure, with less extensive damage compared to the monolithic joint. The hybrid connections were effective in shifting the plastic hinges to outside the connection zone. Therefore, the hybrid connections can be used in high seismic zones because the superior performance results meet the requirements of the seismic codes.</p

Evaluation of the CO2 emissions of an innovative composite precast concrete structure building frame

The type of frame system, materials, and power consumption used for the construction of new buildings cause environmental issues because of the production of carbon dioxide (CO2) emissions. Therefore, a new type of sustainable precast concrete structural system called SMART frame has been introduced to reduce the CO2 emissions during the construction of buildings. To determine the effectiveness of the CO2 emission reduction based on the new SMART frame, a similar frame configuration based on reinforced concrete (RC) was used. The SMART and RC building frames consisted of 12 storeys with similar floor areas and were designed under similar conditions. The CO2 emissions based on the material resources and construction methods used for the two building models were analysed. Additionally, the power consumption associated with the use of electricity and fuels for the devices and equipment was considered in the analysis of the total CO2 emissions. The total CO2 emissions of the SMART and RC frame buildings in kilograms (kg) per square meter (m2) are 455.94 and 516.12 kg CO2/m2, respectively. Thus, the total amount of CO2 emission reduction achieved in this study is 60.18 kg CO2/m2. In terms of the individual effects of materials and power consumption, the SMART building has a larger contribution, accounting for a 12.42% and 8.12% decrease in the CO2 emissions, respectively, compared with the RC building. Overall, based on the materials and power consumption used during the construction stage of the SMART frame building, the total CO2 emissions decreased by 11.66% compared with the RC building. Therefore, the SMART frame can be adopted as a sustainable frame alternative to the RC frame system.</p

Reinforced concrete ring beams [non-linear finite element analysis (NLFEA)]

Ring beams are encountered in dome, circular reservoir and silo structure. Reinforced concrete ring beams supported by equally spaced columns have been used for the construction of silo structure, where the large free space is needed at the ground level. In this paper, three reinforced concrete ring beams supported on four equally spaced columns have been analyzed by using non-linear finite element analysis (NLEFA) to predict the ultimate strength, mechanism of failure, crack pattern and deformed shape. The geometrical and material properties of the ring beams are similar except of its cross sectional depth and the properties of reinforcements. The NLFEA results indicate that the failure modes of the ring beams are dependent on its (depth/span) ratio (the span/depth ratio has been taken as straight beams). The tension stiffening value from 0.002 to 0.003 is suggested to use in the non- linear finite element analysis (NLFEA) of ring beams

Adopting particle-packing method to develop high strength palm oil clinker concrete

Utilization of locally available waste and by-product to replace conventional concrete materials has gained considerable attention over the past two decades. This study is a part of an extensive research program on the characteristics of palm oil clinker (POC) incorporated concrete. In this study, experimental investigation was carried out on incorporating POC as aggregates and filler material in the production of high strength concrete (HSC). Crushed POC were used as partial and full replacement of natural aggregates i.e. fine and coarse. Palm oil clinker powder (POCP) was then incorporated to fill the voids present on the surface of POC particles, while maintaining the other mix constituents. Fresh and hardened properties of the POC concrete with and without POCP were investigated. Substituting coarse aggregate with POC negatively affected the concrete fresh and hardened properties due to POC porous nature. However, the results of the study revealed that incorporating additional POCP as filler material by adopting Particle-Packing (PP) method improved the engineering properties of POC concrete. Therefore, there is a potential towards utilization of POC for many practical construction applications. POC being an environmentally-friendly and a low-cost aggregate can serve as a normal aggregate alternative for future use

Enhancement of seismic behaviour of precast beam-to-column joints using engineered cementitious composite

Seismic activities can cause considerable damage to the integrity of the reinforced concrete and precast concrete structures, particularly in the beam-to-column joints. This article investigates the impact of using engineered cementitious composite (ECC) with different types of fibres on the performance behaviour of novel precast beam-to-column joints subjected to cyclic loading. Six samples of the novel precast hybrid joints, including one sample with a conventional joint, were tested to evaluate the seismic behaviour of the joints. The investigated precast joints were cast using ECC with 2% volume fraction of polyvinyl alcohol fibre (with two different aspect ratios), polyethylene fibre, hooked-end steel fibre, and hybrid fibre, while normal concrete was used to prepare the conventional monolithic joint. The seismic behaviour of the precast joints exhibited better performance than the conventional monolithic joint. This is as a result of the higher tensile and flexural strengths of the ECC fibres, better mechanical bridging in the crack area, adequate amount and distribution of the fibres, good bonding in the ECC produced, the increasing resistance to slippage for the reinforcing bars, and avoidance of the spalling concrete in the joint area, which may cause shear failure. The deformation capacity of the precast joints was 12.5% higher than that of the conventional monolithic joint. In addition, the ductility values and the hysteretic energy dissipations of the precast joints were 15.69–43.14% and 25.40–49.18%, respectively greater than that of the conventional monolithic joint. Furthermore, beam flexural failure was observed for the precast samples and there was less damage compared with the monolithic sample. Thus, the novel precast joints can be potentially implemented to withstand high earthquake activities due to their superior seismic performance.</p

Plastic hinge relocation on the beams with innovative beam-to-column joints

The present study utilises the new hybrid precast beam-to-column joints cast with Engineered Cementitious Composite (ECC) for relocating the plastic hinge zone on the beams outside the joint zone. Three samples including a monolithic reinforced concrete (RC) sample were tested under a quasi-static-cyclic loading to assess the seismic behaviour of the joints. The test results exhibited that the use of ECC for casting the hybrid joints and the adjacent beams areas can prevent brittle failure due to the superior mechanical properties of ECC. Moreover, the increase of energy dissipation capacity of the proposed hybrid joints was also observed compared to the RC sample. Therefore, casting the joint using ECC is recommended for enhancing the seismic behaviour.</p

Experimental and numerical investigations into the compressive behaviour of circular concrete-filled double-skin steel tubular columns with bolted shear studs

Eight medium-length circular concrete-filled double-skin steel tubular (CFDST) columns were examined under axial compression to evaluate the influence of bolted shear studs on the axial performance of CFDST columns. The specimens comprised six columns with bolted shear studs with longitudinal spacings of 100 mm, 75 mm, and 50 mm, and two control columns without bolted shear studs for comparison. The investigated parameters were the failure mechanisms, load-displacement curves, initial axial stiffness, compressive strength, toughness, ductility, residual strength, as well as load-strain responses. Besides, a finite element (FE) model was developed and validated against experimental results to further investigate the performance of columns. The test results demonstrated that the bolted shear studs avoided shear failure and significantly increased the ductility of the specimens. Reducing the bolted shear stud spacing reduced the intensity of local buckling in the outer tube and improved the confinement effect. Additionally, the confinement effect provided by the outer tube was remarkably improved by introducing the bolted shear studs.</p