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Abstract Previous studies have revealed that the contribution of slab reinforcement to the T-beam flexural strength in negative moment regions are not negligible for the seismic capacity design. An effective slab width (i.e., effective width of flanged section) has been proposed, within which the slab reinforcement needs to be included in the calculation of the beam nominal flexural strength in negative moment regions. These studies mainly focused on the cases using normal-strength steel in moment resisting frames. However, recently high-strength steel has been widely used in reinforced concrete moment resisting frames in high seismic regions to avoid congestion near beam-column joints. The use of high-strength steel may affect the beam stiffness due to the fact that it will require less amount of reinforcement, and result in a different normal stress distribution compared to the case with normal-strength steel. Therefore, this paper investigates the slab reinforcement contribution to the flexural strength of the reinforced concrete T-beam designed with high-strength steel in negative moment regions at exterior beam-column joints, for which nonlinear pushover analyses were conducted. Beam reinforcement grade was considered as a primary parameter with several other design variables including slab thickness, height, and span length of the beam. Analytical results show that the use of high-strength steel can result in a wider effective slab width than the case of normal-strength steel for calculating the beam nominal flexural strength under the negative moment. Based on these results, new design equations were proposed.

Abstract A renewable energy storage system is being proposed through a multi-disciplinary research project. This system utilizes reinforced concrete pile foundations to store renewable energy generated from solar panels attached to building structures. The renewable energy can be stored in the form of compressed air inside the pile foundation with a hollowed section. The pile foundation should resist complex combined actions including structural loads, soil effects, and pressures induced from the compressed air, and thus it requires a careful analysis and design considerations to secure a sufficient structural safety. This paper presents analytical investigation results on the structural responses of the energy piles under these combined loadings. The pile foundations were designed based on the current design practices for various building geometries including the number of stories and column spacing. The magnitude of air pressure was determined from the thermodynamic cycles for the available renewable energy for storage considering building and pile foundation geometries. Finite element analyses were conducted using an elastic 3D model to determine critical tensile stresses of the pile foundation. These critical tensile stresses were used to identify required reinforcement in the pile section. On this basis, several nonlinear finite element analyses were then conducted using inelastic constitutive models of materials to investigate the crack patterns of the hollowed concrete section. Recommendations were finally presented for proper practical designs of the pile foundation serving as the renewable energy storage medium.

The fundamental notion of ‘smart’ in building materials discourse is responsiveness—the ability of materials to react to environmental stimuli by manifesting a noticeable physical change when there is a difference in the conditions of their immediate surroundings. This notion, however, is also interchanged with ‘intelligence’, which involves an array of control protocols. Notwithstanding, both notions are used synonymously and as occupant comfort and energy efficiency strategies in buildings. The current study aimed to underscore the fundamental issues in the conceptualization of both notions in building materials colloquy by systematic review of published literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 checklist. The review revealed that while smart responses are direct, predictable and reversible, requiring no external control system, computer systems and networks which require a constant supply of energy are essential for intelligence. In fact, the relationship between intelligent systems, energy efficiency and occupant comfort depends on external computer control and machine components of learning, resulting in complex systems with longer payback times, whereas smart materials and systems respond directly and immediately without additional energy or occupant control. The discussions present an attempt towards promoting zero additional energy demand for buildings using smart materials.

The concept of safe design in architectural and civil engineering is of importance to protect humanity considering our economic, environment and sociality to maintain and improve its quality of life without degrading the quantity and quality [...]

The introduction of Eurocode in Kazakhstan allows for the application of modern technological innovations and the elimination of technical barriers for the realization of international projects. It is significant to study the international standards and design requirements provided in Eurocode. This study presents a comparative analysis of Kazakhstani and European approaches for the geotechnical design of foundations and provides the design methods in the considered codes of practice. Three different types of foundations (i.e., raft, pile, and piled raft foundations) were designed following SP RK 5.01-102-2013—Foundations of buildings and structures, SP RK 5.01-103-2013—Pile foundations, and Eurocode 7: Geotechnical design for the Nur-Sultan soil profile. For all three types of foundations, the calculated results of bearing resistance and elastic settlement showed the conservativeness of Eurocode over SNiP-based Kazakhstani building regulations, as the values of bearing resistance and elastic settlement adhering to Kazakhstani code exceeded the Eurocode values. The difference between the obtained results can be explained by the application of higher values of partial safety factors by Eurocode 7. Sensitivity analysis of the bearing resistance on foundation parameters (i.e., raft foundation width and pile length) for the Kazakhstani and European approaches was performed to support the conclusions of the study.

Energy storage pile foundations are being developed for storing renewable energy by utilizing compressed air energy storage technology. Previous studies on isolated piles indicate that compressed air can result in pressure and temperature fluctuations in the pile, which can further affect safety of the pile foundation. Meanwhile, the temperature changes and distributions for the pile and surrounding soil also are influenced by adjacent piles in typical group pile constructions. Therefore, dynamic thermal transfer simulations were conducted in this paper to investigate the temperature changes and distributions in the concrete pile and surrounding soil for group pile construction. The main parameter in this study is the spacing of the piles. The analysis results show that the group pile effect significantly increases the temperature up to more than 100 °C depending on the location and changes its distribution in both concrete and soil due to the heat transferred from the adjacent piles. The final stabilized temperature can be as high as 120 °C in the concrete pile and 110 °C in the soil after numerous loading cycles, which is about 4 times higher than typical thermo-active energy pile applications. Thus, it is important to include the group pile effect for design and analysis of the energy storage pile foundation.

The design of shallow foundations is performed in accordance with different building regulations depending on geotechnical and geological conditions. This paper involves the design calculations applying Kazakhstani and European approaches. The design of shallow foundations in Nur-Sultan city in Kazakhstan was implemented by the calculation of bearing capacity and elastic settlement in accordance with the design procedures provided in SP RK 5.01-102-2013: Foundations of buildings and structures, and Eurocode 7: Geotechnical design. The calculated results of bearing capacity and elastic settlement for two types of shallow foundations, such as pad foundation and strip foundation, adhering to Kazakhstani and European approaches are relatively comparable. However, the European approach provided higher values of bearing capacity and elastic settlement for the designed shallow foundation compared to the Kazakhstani approach. The difference in the results is explained by the application of different values of partial factors of safety for the determination of bearing capacity and different methods for the calculation of the elastic settlement of shallow foundations (i.e., elasticity theory and layer summation method).

To accommodate growing demands on either heavy steel structures or unique buildings with irregular configurations, built-up wide-flange steel (BWS) beams are being popularly used in modern steel construction. In current fabrication practices of BWS members, high-performance steels produced in steelmaking factories under the thermo-mechanical control process (TMCP) are typically utilized to achieve proper welding performances. However, since its basic unit price is quite higher than typical hot-rolled steel materials, this study introduced a hybrid BWS section for cost saving with no performance degradation, where high-performance TMCP steel was used in flanges, and conventional hot-rolled steel was adopted in web plate. To verify the tensile performances of a hybrid BWS section with non-uniform properties, split T tension and Charpy impact tests were conducted, and flexural tests were also carried out on hybrid and homogeneous BWS beam members. On this basis, it was confirmed that the structural performance of the hybrid BWS member is comparable with that of the conventional one with a uniform section property.

A new pile foundation system is being developed for renewable energy storage through a multi-disciplinary research project. This system utilizes the compressed air technology to store renewable energy inside the reinforced concrete pile foundation configured with hollowed sections. The compressed air can result in high air pressure to which the structural response of the pile foundation subjected has been studied. However, the temperature in the pile foundation can be affected by the compressed air if sufficient cooling is not provided. The temperature change can generate thermal stresses and affect the structural safety of the pile foundation. As a first step to investigate this thermal effect, this paper studies temperature distributions inside the concrete section for the pile foundation through non-steady state heat transfer analyses. Several parameters were considered in the study, including thermal conductivities of the concrete, specific heat capacities of the concrete, and dimensions of the pile foundation. It has been found that the temperature distribution along the concrete section varies significantly during a daily energy storage cycle as well as subsequent cycles due to the cumulative effect of residual temperatures at the end of each cycle. The temperature distribution is largely affected by the thermal conductivity of the concrete and the geometry of the pile foundation. The obtained temperature distribution can be used for investigation of the thermal stress inside the foundation and surrounding soil.

Fiber-reinforced polymer (FRP) reinforcements have been used in versatile forms in recent construction practices to enhance durability performance and, consequently, to attain longevity of concrete structures. The shear strength of FRP-reinforced concrete (FRP-RC) beams holds significant importance in structural design. However, inherent analytical uncertainty exists concerning shear in concrete members due to the distinctive material characteristics of FRP bars compared to conventional steel reinforcements, such as their low axial stiffness and bond properties. This study aims to identify the shear-resistance mechanisms developed under combined actions between concrete and FRP reinforcements. To this end, the dual-potential capacity model (DPCM) was extended to FRP-RC beam members subjected to shear and flexure, and an attempt was also made to derive a simplified method. To validate the proposed approaches, a total of 437 shear test results from RC members incorporating FRP bars were used. Findings indicate that the proposed methods can provide an acceptable level of analytical accuracy. In addition, a significant shift in the shear failure mode of FRP-RC members with no stirrups was observed from the compression zone to the cracked tension zone as the FRP reinforcement ratios increased. Conversely, when FRP stirrups were added, the shear failure mode was mostly dominated by the compression zone. [ABSTRACT FROM AUTHOR]

In this study, full-scale loading tests were conducted to investigate web-shear strengths of hollow-core slab (HCS) members strengthened in shear by using practically viable methods. All the HCS units used in the current test program were fabricated by using the individual mold method, not by the extrusion method, and the key experimental variables of the shear test were set as the presence of shear reinforcement, core-filling concrete, topping concrete, and also the magnitude of effective prestress. The shear force-displacement behaviors, crack patterns, and strain response of shear reinforcements were reported in detail. In addition, to identify the shear strength enhancement provided under various strengthening conditions in a quantitative manner, existing shear test results of series specimens, including a naked HCS member and corresponding composite HCS members with cast-in-place (CIP) concrete and/ or shear reinforcements, were collected from literature. On this basis, a practical design expression capable of estimating shear strengths of HCSs strengthened with CIP concrete and stirrups was suggested based on the ACI 318 code equation. The proposed method evaluated the shear strengths of the collected specimens with a good level of accuracy, regardless of the presence of core-filling concrete, topping concrete, and shear reinforcements. [ABSTRACT FROM AUTHOR]

For the past several decades, there has been an ongoing academic challenge to understand the shear-transfer mechanism in reinforced concrete (RC) members, particularly in those with small shear span-depth ratios, also known as deep beams. Analytical uncertainty regarding shear strength inevitably increases when those deep members are strengthened in shear using externally bonded fiber-reinforced polymer (FRP) composites. This study aims to investigate the complex, interrelated effects of short shear span-depth ratios and FRP composites on RC deep beam members. To this end, the fundamental formulations of the dual potential capacity model (DPCM) are extended to RC deep members reinforced with externally bonded FRP composites. The proposed model can consider the various types of FRP composites, fiber bonding configurations, and fiber layouts, and various failure modes of concrete and FRP reinforcements are also reflected. A total of 131 shear test results of RC deep and short members with externally bonded FRP composites are carefully collected, and those are added to the existing database of RC slender members strengthened with FRP composites. On this basis, the proposed approach is verified by comparing test results with analysis results, and a reasonable level of analytical accuracy is achieved. The statistical data distribution of strength ratios between the test and analytical results is consistent across a range of shear span-depth ratios from approximately 0.7 to 4.0. Overall, the proposed DPCM approach provides a useful tool for analyzing the shear strength of RC deep beam members strengthened with externally bonded FRP composites. [ABSTRACT FROM AUTHOR]

Identifying plastic hinge property is one of key the factors in successful modeling and subsequent seismic performance evaluation of precast concrete (PC) moment frame systems. Tight mechanical splices are also essentially required in precast connections, and its residual slip can greatly affect the plastic hinge length and finally the emulative performance level of PC seismic forceresisting system (SFRS). However, most of the existing models are not directly applicable in current forms to estimate the plastic hinge length of precast connections with mechanical splices. To address the effects of the residual slip induced in the mechanically spliced reinforcement system and its nonuniform stiffness due to splicing device (or coupler), a detailed nonlinear finite element (FE) analysis model was developed in this study, where plasticity-based constitutive models and a unique connector element were adopted for concrete and mechanically spliced reinforcements, respectively. Existing test results of column-foundation connections were used to verify the analytical approach. On this basis, a robust macro modeling method was also proposed for nonlinear cyclic analysis of PC moment frame systems with mechanical splices in this study. It appears that the magnitude of the residual slip in mechanical splices can greatly undermine the lateral stiffness, energy dissipation capacity, and equivalent viscous damping ratio of PC moment connections, and the proposed macro modeling approach can reasonably capture their behavioral characteristics. [ABSTRACT FROM AUTHOR]

Coupling action developed by interfacial shear along vertical connections between precast concrete (PC) wall segments has significant impacts on the seismic performance of a precast shear wall building system. This study investigated the effect of various seismic details on lateral performances of coupled intermediate precast shear wall systems through reversed cyclic tests, and direct shear tests were also conducted to characterize local interfacial shear behaviors between individual PC wall segments. On this basis, a series of numerical investigations were then carried out to further identify how the interfacial shear behavior affects the seismic responses of PC shear wall systems through an advanced finite element (FE) analysis approach. To this end, several interfacial shear curves were generated considering various combinations of the maximum shear capacities, stiffness, and post peak responses, and subsequent nonlinear cyclic analyses were conducted. It was numerically confirmed that the maximum interfacial shear strength is a key influential factor to the lateral flexural strength of PC shear wall systems, while stiffness and post-peak strength degradation of interfacial shear curves affect their energy dissipation and lateral drift capabilities, respectively. [ABSTRACT FROM AUTHOR]

There is a drastic change in design and construction trends of underground structures, where a precast concrete (PC) shear wall system is quickly replacing a cast-in-place (CIP) diaphragm wall (that is, the so-called slurry wall) system in urban areas for better constructability and reliable performances. However, it is challenging to achieve the proper coupling action or composite performance through vertical connections between adjacent PC walls and that in horizontal connection between PC walls and foundations to satisfy the seismic design criteria specified in codes. To this end, this study introduces cast-in-place (CIP) cap beam and waling beam at the top and midheight of PC walls to connect individual precast wall panels by means of a coupling action. Precast specimens were carefully designed to be code-compliant as intermediate precast shear wall systems, and were then fabricated and tested under the reversed cyclic loads to evaluate seismic performances. Detailed numerical models were also developed to identify how CIP beams can effectively improve the seismic performance of a precast shear wall system by restraining the free rotation and axial deformation of individual precast wall panels. [ABSTRACT FROM AUTHOR]

In this study, three multi-span moment frames are fabricated and tested under reversed cyclic loadings. The test program includes a reinforced concrete (RC) specimen with typical monolithic connections, which fully satisfies the seismic specification of the special moment frame prescribed in ACI 318, and two hybrid posttensioned precast concrete (HPPC) frame specimens, which are integrated using unbonded prestressing tendons throughout two-bay continuous spans. On this basis, excellent structural integrity and connection continuities in beam-column joints between discrete precast members can be achieved. The HPPC frame systems demonstrate seismic performances that are comparable to those of monolithic RC special moment frames designed based on the seismic design provision specified in ACI 318. In addition, key observations from the test program are presented comprehensively, where quantitative indexes are used to evaluate the seismic performance of the test specimens in terms of capacity, ductility, and damage characteristics, and the cyclic responses of the HPPC specimens were verified by using numerical analyses. [ABSTRACT FROM AUTHOR]

Prestressed hollow-core slabs (PHCS) are generally fabricated through an automated extrusion method by using an extremely dry concrete mixture to maximize productivity in precast factories. In consequence, it is very challenging not only to provide shear connectors along the interface between the PHCS unit and castin-place (CIP) topping concrete but also to secure code-compliant intentional roughness due to its extremely hard and flat surface condition. Thus, it is difficult to have sufficient horizontal shear strength required to achieve flexural performances of the prestressed composite members. To this end, extensive pushoff tests were conducted in this study considering various interface roughness conditions, from which some viable options were chosen. Then, flexural tests on full-scale composite PHCS specimens were performed with selected surface conditions from the pushoff tests. On this basis, the applicability of various surface roughness conditions that are inevitably faced in practices is examined based on ACI 318 design criteria and nonlinear analysis. It was confirmed that sufficient horizontal shear strength can be achieved not only by properly roughened surface conditions but also by placing wire meshes between PHCS units even with no intentional roughness. [ABSTRACT FROM AUTHOR]

This study presents an analytical model for estimating the effective compressive strength of a reinforced concrete (RC) column intersected by a floor slab made of relatively low-grade concrete. The proposed model is based on a theoretically sound background and considers the force equilibrium and strain compatibility conditions in the vicinity of the interface between the upper and lower columns and an intervening slab. By using the parametric study results obtained from finite element analyses, the effects of the confinement provided by the surrounding slab and the secondary stresses induced by the Poisson effect in the columns and slab panel zone were formulated in detail. A simple design expression was then derived for the better applicability of the proposed method for the estimation of the effective compressive strength of the exterior and interior columns with an intervening slab, in a unified manner. To verify the proposed model, the test results of 81 exterior columns and 24 interior columns were collected from the literature. It was found that the effective compressive strengths obtained by the proposed methods were in good agreement with these test results. [ABSTRACT FROM AUTHOR]

A new modeling approach for estimating the shear behaviors of reinforced concrete (RC) beams with corroded longitudinal reinforcements is presented. The corrosion effects on the constitutive models of materials subjected to multi-axial stresses are clarified, including the bond mechanism between the reinforcement and surrounding concrete, which is a critical factor. The material models were implemented in a nonlinear finite element analysis (FEA) platform, and an experimental program is introduced to verify the analysis results. It appeared that the shear response of RC members can be greatly influenced by the corrosion of longitudinal reinforcements and anchorage conditions, and the failure modes can be changed from the diagonal shear-tension to the bond-critical mechanisms. The proposed approach captured such unique behavioral characteristics of RC members with corroded longitudinal reinforcement. [ABSTRACT FROM AUTHOR]

This study aims to develop a torsional behavior model for reinforced concrete (RC) members subjected to torsional moment combined with flexure. In the suggested method, the cross section of an RC member is idealized by using a thin-walled tube consisting of shear panel elements, where the shear flow is developed along its perimeter zone. Those panels are further divided into the compression and tension zones considering the normal stresses induced by flexural moment. The panel elements subjected to combined shear and normal stresses induced by torsional and flexural moments, respectively, are then analyzed by using the softened truss model. The multiple failure criteria are addressed to identify the failure mode and determine the ultimate strength of an RC member. Based on the detailed verifications by comparisons of test results collected from literature with those estimated by the proposed method, it was concluded that the proposed method can capture the torsional responses of RC specimens with a high level of accuracy. [ABSTRACT FROM AUTHOR]

Prestressed inverted multi-tee (IMT) slabs have been widely used in recent precast construction as a fast-built composite flooring system. However, there is a critical issue about its vulnerability in shear. To this end, a total of six IMT slabs were tested in this study, where the magnitude of prestress, and presences of shear reinforcement and cast-in-place (CIP) topping concrete were considered as key experimental variables. An analytical method capable of estimating the shear strengths of IMT slabs with topping concrete as a composite prestressed member was suggested by using the transformed section approach combined with the dual potential capacity concept. The proposed model can identify the shear strength and failure mode, and a simplified model was also developed and verified for its better applicability to be easily used in practice. [ABSTRACT FROM AUTHOR]

According to traditional theory, there should be shear stresses in the cracked tension zone due to the presence of bond between longitudinal tension reinforcements and surrounding concrete. To investigate the effect of this bond mechanism on shear behaviors of prestressed concrete (PSC) members with and without shear reinforcement, the dual potential capacity model (DPCM) was adopted in this study. The size effect typically observed in large PSC members was also considered in the proposed method by addressing the shear crack concentration concept. Verifications of the proposed model were conducted using the extensive shear database of PSC members with various material properties and geometrical details. As an extreme case, the perfect-slip behavior (no bond condition) between a prestressing strand and surrounding concrete in unbonded post-tensioned (UPT) concrete members was considered in the proposed model, and their analytical results were used to identify how the bond mechanism affects the shear strengths and failure modes of PSC members. [ABSTRACT FROM AUTHOR]

Given current environmental concerns, attention has been directed toward the use of recycled coarse aggregates (RCAs) as a substitute for natural raw materials commonly consumed in construction. In regard to shear performance, limited studies currently exist. To this end, a total of 56 reinforced concrete beams without stirrups were tested to identify the effect of using RCA on shear strength. Failure governed primarily by shear span-depth ratios and partially by tension reinforcement ratios can significantly affect shear behavior of RCA concrete members. Test results obtained for this study were evaluated using current ACI 318 shear design equations. Overall, crack patterns and failure modes for the RCA concrete test specimens were similar to those of natural coarse aggregates (NCAs). On this basis, it was established that RCA concrete beams can be used in practice with confidence in satisfactory shear performance. [ABSTRACT FROM AUTHOR]

The prestressed hollow-core slab (PHCS) system is one of the most commonly adopted precast concrete flooring systems, which can optimize productivity and structural efficiency. Because PHCS members are typically produced by the extrusion method in longline precast plants, it is extremely difficult to provide shear reinforcements due to the automated fabrication method for forming multiple hollow-cores in a cross section. However, the current ACI 318 building code stipulates that the web-shear capacity of hollowcore members over 315 mm (12.5 in.) thickness without minimum shear reinforcement should be reduced by half, which increases the demands of shear strengthening for a thick PHCS member at its end regions. In this study, the shear tests of thick PHCS members strengthened in shear, using various core-filling methods frequently used in the current precast industry, were conducted and a new analytical method was addressed to estimate the shear strengths of the PHCS members composite with core-filling concretes. [ABSTRACT FROM AUTHOR]

Commercially available reinforcing bars are generally produced in standard lengths to ensure smooth shipment and quality control in steel manufacturing plants. As a result, splicing of reinforcing steel bars is inevitable in construction of reinforced concrete structures. To improve constructability and lessen disadvantages in traditional splicing methods, this study proposes a combo-type mechanical splicing method using the screw-ribbed (that is, threaddeformed) reinforcing bars. The combo-type mechanical splices were evaluated for seismic performance of reinforced concrete (RC) column-foundation connections under cyclic loading tests. In the test program, presence of grout in the mechanical sleeves, location of splices, and compressive strengths of concrete were considered as the key variables. Test results demonstrated that RC column-foundation connections with mechanical splices can provide comparable seismic performance with that of continuous reinforcement. In addition, results confirmed current building code allowance for non-grouted mechanical splices in RC intermediate moment frames. [ABSTRACT FROM AUTHOR]