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Ground-motion selection is essential as an input for dynamic structural analyses. Although recent studies have highlighted the importance of target variance as auxiliary criteria and introduced selection methods, they typically require a trade-off between computational expense and accuracy. This paper presents an efficient and accurate method for ground-motion selection and scaling that matches both the target mean and standard deviation, while using either a single-objective- or multi-objective-based pattern-search optimization technique. The selection algorithm was tested using the code-based and conditional-spectrum-based target spectrum for various design scenarios. The results indicated that the pattern-search-based selection algorithm is an optimal method as it provides the best-matching records suite with a more precise and quicker selection than other notable optimization techniques.

A novel hybrid floor, which was a prefabricated composite system infilled using polymers with hollow cores between its top and bottom steel plates, was previously developed for application in steel structures. In addition, the structural performance of the steel floor, including its bending capacity, floor vibration, and dynamic characteristics, were investigated. However, as the fire resistance performance of the hybrid floor had not been investigated, it was installed in actual buildings using insulating materials, which caused problems, such as a dirty workplace and additional work that prolonged the construction period. In this study, small-scale furnace tests, whose specimens have fewer variables in comparison with those of full-scale tests, were conducted instead of full-scale furnace tests to analyze the effects of various variables on the fire resistance performance of the hybrid floor. In fact, the heating curves obtained via the small-scale furnace tests were not similar those suggested by Korean Standards (KS). The energy-based time equivalent approach was applied to calibrate the results. Thus, the fire resistance ratings were estimated based on small-scale furnace tests via the energy-based time equivalent approach with respect to polymer thickness and aspect ratio, which were expressed using the lengths and widths of the specimens.

In recent years, studies that can maximize irregularity have increased as technological constraints weaken owing to the development of construction technology and the increase in demand for free-form structures. Considering this, free-form structures have been constructed using various materials. Concrete is considered most suitable for realizing an atypical shape because it is highly economical and can be assembled in a free form. However, not many studies have evaluated the structural performance of free-form concrete structures using free-form formwork 3D printer (F3D) technology, a 3D printing technology. Free-form structures must be designed to secure structural stability under both dead and live loads, as well as natural hazards such as wind, snow, and earthquakes. Therefore, in this study, we tested a free-form structure constructed by F3D printing using small-scale models that satisfy the similitude law with shaking tables. Furthermore, a finite element analysis was conducted to validate the small-scale tests. Lastly, the seismic performance of free-form concrete structures was evaluated based on the test and analysis results.

Multiple hazards, which threaten people’s lives and property, are the main concern for engineers in preventing dangers to buildings. In particular, densely populated areas, such as capital cities and tall buildings, are exposed to higher risks owing to multiple hazards. To rapidly evaluate the disaster assessment of tall buildings, the Federal Emergency Management Agency (FEMA) in the U.S. proposed the integrated rapid visual screening system (IRVS). However, the IRVS system only considers U.S. conditions. Therefore, a Korean-oriented rapid visual screening system should be developed because the number of buildings over 200 m in Korea ranked fourth in the world with the highest density (500 people per square kilometer) among the top five countries based on the Council on Tall Buildings and Urban Habitat’s (CTBUH) database. This study describes a Korea-rapid visual screening (K-RVS) system that focuses on the structural safety of tall buildings in Korea. The K-RVS system was modified based on the IRVS, considering the Korean design standard (KDS) and Korean conditions. With the weight value for each characteristic, the scores for each hazard and final scores combined from the scores by multi-hazard can be obtained to conduct a disaster assessment of tall buildings subjected to multiple hazards.

Concrete-filled steel tubes (CFSTs) are widely used in construction. To achieve composite action and take full advantage of the two materials, strain continuity at the steel–concrete interface is essential. When the concrete core and steel tube are not loaded simultaneously in regions such as beam or brace connections to the steel tubes of a CFST column, the steel–concrete bond plays a crucial role in load transfer. This study uses a validated finite-element model to investigate the bond-slip behavior between the steel tube and concrete in square CFST mega columns through a push-out analysis of eleven 1.2- × 1.2-m mega columns. The bond-slip behavior of CFST mega columns with and without mechanical connectors, including shear studs, rib plates, and connecting plates, is studied. The finite-element results indicate that the mechanical connectors substantially increased the maximum bond stress. Among the analyzed CFST mega columns, those with closely spaced shear studs and rib plate connectors with circular holes exhibited the highest bond stress, followed by plate connectors and widely spaced shear stud connectors. In the case of shear stud connectors, the stud diameter and spacing influenced the bond behavior more than the stud length. As the stud spacing decreased, the failure mode shifted from studs shearing off to outward buckling of the steel tube.

In this era of the fourth industrial revolution, the integration of big data and 3D printing technology with the construction industry has maximized productivity. Currently, there is an active effort to research the optimal cladding structure through 3D printing technology to reduce production costs. This paper proposes a new type of 3D print curtain wall, using a high-strength ABS-M30 polymer panel, which is stronger than the standard acrylonitrile butadiene styrene (ABS) polymer, as an internally reinforced structure. This structure is fabricated via fused deposition modeling, a 3D printing method, to reduce the weight of the general cement panel. In addition, the shape of the polymer board was designed; three shapes were considered—O, W, and X types—which aided in further reducing the weight of the cladding. After comparing the center deformation of the structure through a lateral load test and finite element method analysis, the optimal model was selected. The measured data of the two methods at a design wind speed of 100% showed a difference of approximately 10%; however, at 150% of the design wind speed, the difference between the two sets of data increased to 27%.

In this study, the fire resistance performance of steel–polymer prefabricated composite floors, which have a sandwich-type structure, was assessed via standard fire tests and analyzed using finite element analysis. This form of analysis should consider two aspects, namely the thermal and structural fields, so as to simulate complicated material properties and large deformations. As previous studies have already conducted analysis in the thermal field, this study entailed only the structural analysis based on the temperature distributions obtained from the thermal analysis. The variables of the specimens were the thicknesses of the top and bottom steel plates and polymers. According to the analysis results, the top steel plate thickness had no impact on the stability ratings, a criterion for fire resistance performance, whereas the bottom steel plate showed a linear correlation with the stability rating. An equation for the stability rating of composite floors was proposed, and an equation for fire resistance performance was devised based on the insulation ratings, which were obtained from the thermal analysis results.

Recently, much research with high-tech technology is being conducted in building inspection. In previous studies, thermography technology quickly and accurately inspected the concrete crack defects, and several machine learning models can reliably predict the crack depths. In this study, the most proper model would be proposed according to the concrete crack by evaluating the adaptability of the seven machine learning models. The models also predicted the crack depths, and the data were applied to each machine learning considering concrete temperature and external parameters. In machine learning, less critical features were ignored by filtering existing data to find useful features related to crack depths. Machine learning models are evaluated, and the structures of the models were investigated to determine the feature importance and part dependence. Those enabled us to decide the most proper machine learning according to the cracks.

This study presents a tube-in-tube buckling-restrained brace (BRB) infilled with lightweight and rapid hardening polymer. The proposed BRB consists of a circular or square tube core encased with a tube of similar shape and polymer infill. The tube-in-tube arrangement minimizes the filler material volume and enables the use of rolled steel section as opposed to welded profiles commonly utilized when large BRB axial strength is required, although welded profiles suffer from low assembly accuracy resulting from welding deformation. The infilled polymer has a density of approximately half that of mortar and requires a curing time of 24 h, enabling weight and fabrication time reduction. The stability and inelastic deformation capability of the BRB were investigated through brace and subassembly tests of six circular and four-square full-scale specimens, followed by finite element analysis. The test results show that circular BRB designed with a Pcr/Py ratio of 1.46 exhibited a stable hysteresis up to 1.42% and 1.06% core strain in tension and compression, respectively. Circular and square specimens designed with Pcr/Py ratios ranging from 0.82 to 1.06 exhibited stable hysteresis before failing by global buckling at compressive core stains ranging from 0.86% to 1.09%. The slot weld detail adopted for welding core projection stiffener displayed a stable performance in circular BRB specimens, while it resulted in large plastic strain demand in square BRB specimens, leading to core fracture at tensile core strains ranging from 0.64% to 0.71%.

For easier installation and debonding prevention of the glass fiber reinforced polymer (GFRP) plates in the developed composite floor system, the FRP strengthening method using bolted connections on a steel beam is proposed. A new composite plate, the glass fiber steel composite plate (GSP), was used for reinforcement, and experiments with various variables were performed to evaluate the bearing strength of GSP. Based on the test results of 45 specimens, a design equation for predicting the GSP bearing strength was derived from simple linear regression analysis. The proposed equation provided empirical bearing strengths for the GSPs that were, on average, 8% lower than the actual test results, which was appropriate for a conservative prediction of the actual GSP bearing strength. Additionally, a flexural test of the GSP reinforced steel beam, in which the GSP was connected by bolts, was performed to verify the applicability of the bolt-connected GSP to the developed composite floor beam. The results demonstrated that the load transfer between the steel beam and the GSP can be sufficiently accomplished through the bolted connections. Also, it was confirmed that the bolted connections for attaching the GSP to a steel beam can be conservatively designed by using the equations proposed in this study.

Owing to the development of new materials that enhance structural members in the construction field, steel&ndash, polymer composite floors have been developed and applied to steel structures. Similar to a sandwich system, steel&ndash, polymer composite floors consist of polymers between two steel plates. The structural performance of full-scale composite floors at ambient conditions has been investigated. Additionally, experiments were conducted on analytical models to predict both thermal behavior under fire, including fire resistance based on a small-scale furnace. To evaluate the fire resistance of full-scale steel&ndash, polymer composite floors, the thermal behavior and temperature distribution of composite floors should be investigated. Therefore, the temperature distributions of the full-scale composite floors were estimated using the verified analytical model in this study. Furthermore, to determine the fire design equation of steel&ndash, polymer composite floors in the thermal field, the correlations between variables were investigated, such as the thickness of top and bottom steel plates and polymers, as well as the fire resistance in the thermal field.

This paper introduces two kinds of multi-objective optimization algorithms. The optimal values are determined through multi-objective functions and various equality and inequality constraints. The optimal value results of the two algorithms with different parameters are discussed. A simplified optimization case of reinforced concrete beam was discussed that minimizes the total cost of reinforced concrete beams while complying with all strength and serviceability requirements for a given level of the applied load. This paper focuses on the differences between Multi-objective Harmony Search Algorithm (MOHSA) and Multi-objective Genetic Algorithm (MOGA) for reinforced concrete beam design subjected to a specified set of constraints by considering aspects of the Harmony Memory Considering Rate (HMCR) parameters in HSA and Population Mutation (Pm) parameters in GA. Through HSA and GA for RC beam problem, with same reference strength, the result using GA has a lower cost than using HSA.

Hybrid floors infilled with polymeric materials between two steel plates were developed as a prefabricated floor system in the construction industry. However, the floor’s fire resistance performance has not been investigated. To evaluate this, fire tests suggested by the Korean Standards should be performed. As these tests are costly and time consuming, the number of variables were limited. However, many variables can be investigated in other ways such as furnace tests and finite element analysis (FEA) with less cost and time. In this study, furnace tests on heated surface areas smaller than 1 m2 were conducted to investigate the thermal behavior of the hybrid floor at elevated temperatures. To obtain the reliability of the proposed thermal behavior analytical (TBA) model, verifications were conducted by FEAs. Thermal contact conductance including interfacial thermal properties between two materials was adopted in the TBA model, and the values at elevated temperatures were suggested based on thermo-gravimetric analyses results and verified by FEA. Errors between the tests and TBA model indicated that the model was adequate in predicting the temperature distribution in small-scale hybrids. Furthermore, larger furnace tests and analysis results were compared to verify the TBA model’s application to different sized hybrid floors.

Conventional slit dampers are widely used for the purpose of seismic retrofitting, however, the structure of these dampers is susceptible to fractures, due to stress concentration at the ends of the strips in the event of large earthquakes. To address this issue, a novel radius-cut coke-shaped strip damper featuring improved ductility is proposed herein. This damper was developed based on the moment distribution over the strip when both its ends were constrained. The height-to-width ratio of the strip was increased to induce bending rather than shear deformation, and the reduced beam section method was employed. A radius-cut section was used to intentionally focus the stress to induce the plastic hinge. This reduced the fracture fragility of the specimen, resulting in an increased inelastic deformation capacity. Cyclic loading tests were conducted to verify damping performance against earthquakes. Experiments and finite element analyses proved that the coke-shaped damper exhibits improved ductility. The final fracture occurred in the radius-cut section after sufficient energy dissipation during cyclic loading. The results also indicated further improvements in strength due to the membrane effect under cyclic loading, caused by the tensile resistance of the strip due to its constrained ends.

Introduction.Epilepsy is a chronic brain disease, which treatment consists of relieving the seizures with the help of constant long-term use of anti-epileptic drugs. This, in turn, can cause various negative effects on the body. Epilepsy is not a single disease with various attacks, it is a whole spectrum associated with comorbid conditions, including anxiety and depression. Additional medication is suggested to correct this. Therefore, developing the effective drug-free methods with the help of osteopathic treatment to correct anxiety and depression in epilepsy complex therapy received priority.Goal of research— to study the osteopathic treatment potential to reduce anxiety and depression levels in children with various forms of epilepsy.Materials and methods.The study included 72 children with various forms of epilepsy, aged from 7 to 17 years, 35 girls, 37 boys. The selection criteria were as follows: at least 1 year of epilepsy course duration, no status or serial course of epileptic seizures, no motor and cognitive deteriorations, all children studied in public schools. All children received osteopathic treatment for 2 months, along with medical treatment. Before and after treatment, each patient′s anxiety and depression levels were assessed according to the Hospital Anxiety and Depression Scale (HADS), along with an osteopathic examination.Results.All children taken in the study revealed a range of somatic dysfunctions of craniosacral system, skull and reciprocal tension membranes, with biomechanical abnormality. By initial testing, anxiety and depression average values according to HADS scale were above normal in all children. After osteopathic treatment, a statistically signifi cant decrease in anxiety and depression levels was found.Conclusion. Osteopathic treatment is effi cient for epilepsy complex therapy in children. It helps to reduce drug load in correction of anxiety and depression that accompany the underlying disease.

Concrete cracks can threaten the usability of structures and degrade the aesthetics of buildings. Furthermore, minor cracks can develop into large-scale cracks that may lead to structural failure when exposed to excessive external loads. In addition, the concrete crack width and depth should be precisely measured to investigate the effects of concrete cracks on the stability of structures. Thus, a nondestructive and noncontact testing method was introduced for detecting concrete crack depth using thermal images and machine learning. The thermal images of the cracked specimens were obtained using a constant test setup for several months under daylight conditions, which provided sufficient heat for measuring the temperature distributions of the specimens, with recording parameters such as air temperature, humidity, and illuminance. From the thermal images, the crack and surface temperatures were obtained depending on the crack widths and depths using the parameters. Four machine-learning algorithms (decision tree, extremely randomized tree, gradient boosting, and AdaBoost) were selected, and the results of crack depth prediction were compared to identify the best algorithm. In addition, data bias analysis using principal component analysis, singular value decomposition, and independent component analysis were conducted to evaluate the efficiency of machine learning.

A new floor system for steel buildings was developed that can replace conventional concrete deck slab systems. The floor system is designed with a new type of composite panel with a polymeric material filling between the top and bottom steel plates. Its salient features are its light weight and simple installation that reduce structural materials and shorten the construction period. Experiments with various independent variables were performed to evaluate the flexural capacity of the proposed composite panel, and a finite element analysis was also conducted to examine the state of the stresses generated between the steel plate and the polymeric core. The test results showed that the proposed panel exhibited very ductile behavior and maintained its structural integrity even after a maximum load. No other failure mode than the face yielding of the top and bottom steel plates was observed. The bond strength between the polymeric material and the steel plates was confirmed to be sufficient, even without any special surface treatment or any additional shear connectors, to maintain the stability of the proposed panel and to resist the forces generated at the interface between the two materials. Design equations for predicting the flexural strength and stiffness of the proposed panel were proposed, and its suitability was verified. Additionally, the experimentally tested efficient methods for field applications of the proposed panel regarding cutting and joining were presented in this paper.

This paper describes a seismic strengthening technique using a wall-type damping system (DS), targeted at moment-resisting frame buildings. The DS under consideration is a hybrid damper which works through the combined and multi-phase action of a friction damper (FD) and a metallic damper (MD). To assess the seismic effectiveness of the proposed system, full-scale cyclic tests were conducted on a bare reinforced concrete (RC) frame with non-ductile detailing and four damper-strengthened frames. The RC frame showed highly pinched behavior, whereas the hysteresis curves of strengthened frames were more stable due to the activation of FD and/or MD, forming a larger loop area. The deformation capacities of the RC frame and strengthened frames were not significantly different, but the maximum strength, stiffness, and energy dissipation capacities were significantly improved in the strengthened frames. The calculated strength and stiffness equations accurately represented the actual behavior of the RC frame. Conversely, the stiffness values of the DS were considerably lower than predicted by theoretical equations as a result of the softening of anchorage fixity according to the connection details.

Several studies have examined damping mechanisms to improve damping effects in a tuned liquid column damper (TLCD). The additional damping mechanisms include orifices, valves, and the use of highly viscous liquids. In the present study, in contrast to previous studies, a damping mechanism using embossments on the wall of the TLCD was proposed, and TLCD with embossment (termed as ETLCD) was proposed as a new type of passive damper. The study focuses on an experimental evaluation of the dynamic characteristics of ETLCD and vibration control performance for tall buildings with ETLCD by using a shaking table. Thus, a characteristic experiment was performed with the presence of embossments, total length of the liquid column, and an excitation amplitude ratio as variables. Additionally, a scaled model test of the SDOF building composed of a free vibration test and sine sweep forced vibration test was conducted to verify the vibration control performance of the structure with ETLCD. Consequently, the equivalent damping ratios of conventional TLCD and ETLCD were experimentally compared, and the theoretical natural frequency of TLCD was re-evaluated in the characteristic experiment. Furthermore, the results of the scaled model test indicated that the vibration control performance of the ETLCD was superior to that of the conventional TLCD in terms of response reduction, efficiency, and stability.

Beam to column connection ductility and beam flexural stiffness are crucial parameters for seismic performance and drift control in moment-resisting frames. However, an increase in beam span and depth to obtain column-free flexible internal space affects these parameters negatively. In this paper, a new long-span deep beam-column connection detail is proposed with improved stiffness and adequate ductility for moment frames in low-to-moderate seismic zones. As panel zones can undergo plastic deformation beyond the joint rotation demand in low-to-moderate seismic zones, the beam flange and panel zone in the proposed connection are proportioned such that a stable yielding occurs in the panel zone and two plastic zones on the beam segment away from the beam-column interface. The beam flanges at the beam-column interface are thickened, widened, and tapered to control beam plastic hinge locations and mitigate distress resulting from significant panel zone plastic deformation. The performance of the proposed connection was evaluated through a full-scale cyclic load test and parametric finite element analysis on a beam-column connection with a 1200 mm deep beam. The test and finite element results showed the formation of plastic hinges at the anticipated locations. Furthermore, the connection exhibited stable hysteresis beyond the minimum rotation limits specified for intermediate moment frames (American code) and ductility class medium (Eurocode). Moreover, the connection effectively allowed balancing between beam and panel zone yielding while hindering beam flange distress associated with significant panel zone plastic deformation. Furthermore, a comparison between the proposed and welded unreinforced flange-welded web connection demonstrated improved ductility, stiffness, moment capacity, and energy dissipation capacity. Additionally, equations were proposed to quantify the improvements, and balance beam and panel zone energy dissipation.

Methane production from livestock farming is recognized as an important contributor to global GHGs. Volatile fatty acids (VFAs) found in bovine rumen may be utilized as a substrate for methanogens to form CH4, and thus improvement of quantitative VFA measurements can help facilitate greater understanding and mitigation of CH4 production. This study aims to contribute to the development of more accurate methods for the quantification and specification of VFAs in bovine rumen. The VFAs were analyzed using the conventional method and an alternative catalytic esterification reaction (CER) method. Substantial differences in the detected concentrations of the C3+ VFAs (chain length ≥ 3) were observed between both methods, especially for butyric acid. Evaluation of the sensitivity of both methods to detecting the VFA concentrations in standard solutions confirmed that the values resulting from the CER method were closer to the known concentrations of the standard solution than those from the conventional method. The results of this study provide the first quantitative proof to show the improved accuracy of the measurements of C3+ VFAs when using the CER method compared with the conventional method. Therefore, the CER method can be recommended to analyze the VFAs found in rumen, especially butyric acid and other C3+ VFAs.