Concrete Connections Research Articles

Educational Perspective: AI, Deep Learning, and Creativity

Can artificial intelligence (AI) teach and learn more creatively than humans? The article analyses deep learning theory, which follows a deterministic model of learning, since every intellectual procedure of an artificial agent is supported by concrete neural connections in an artificial neural network. Meanwhile, human creative reasoning follows a non-deterministic model. The article analyses Bayes’ theorem, in which a reasoning system makes judgments about the probability of future events based on events that have happened to it. Meillassoux’s open probability and M. A. Boden’s three types of creativity are discussed. A comparison is made between the a priori algorithm of the Turing machine and a playing child, who invents new a posteriori algorithms while playing. The Heideggerian perspective on the co-creativity of humans and thinking machines is analyzed. The authors conclude that humans have an open horizon for teaching and learning, and that makes them superior with respect to creativity in an educational perspective.

Behaviour and design of monotonically loaded reinforced concrete external beam-column joints

This paper describes an experimental investigation into the influence of beam reinforcement detailing, column axial load and shear reinforcement on the joint shear strength of reinforced concrete external beam-column connections. A series of twelve external beam-column joint specimens were tested in three groups of four specimens. Series 1 investigated the influence of beam reinforcement anchorage type and bend radius. Series 2 studied the influence of column axial load on joint shear strength while series 3 studied the influence of intermediate column bars and joint shear reinforcement. The paper presents the experimental results and describes the influence of the considered variables on joint shear strength. Three existing empirical design equations for external beam-column are evaluated using data from this program and previously tested beam-column joint specimens. Finally, design recommendations are made.

Development of predicting equations for slip modulus and shear capacity of CLT–concrete composite with screw connections

This study investigated the effects of density, screw inclination angle, and screw arrangement on the slip modulus and shear capacity of a screw connection for a cross-laminated timber (CLT) concrete composite (CCC). A total of 35 push-out tests were conducted to investigate slip modulus and shear resistance of the CCC using a self-tapping screw. The test results identified double and single plastic hinges in the screw as the main failure mechanisms in the CLT–concrete screw connection. Compared to pine CLT, the CCC screwed connections with larch CLT showed a greater slip modulus of 18.5–55.1%, higher shear resistance of 44.1–79.2%, but a ductility ratio 17.6–25.4% lower. The CCC screwed connections with a screw angle of 60° showed the lowest slip modulus and shear resistance compared to those with screw angles of 90° and 45°. When two screws with an angle of 45° and 135° in the X-layout were installed, the shear properties of the CCC screwed connections with larch and pine CLT differed by only up to 11%. A newly developed model for the shear modulus and shear resistance of the CCC using a self-tapping screw differed by 17.48% for the slip-modulus and 29.52% for the shear capacity between the predicted and experimental values.

Punching Shear Strength of Reinforced Concrete Flat Plates with Openings

Test results of six half-scale reinforced concrete flat plates connections with an opening in the vicinity of the column are reported. The test specimens represent a portion of a slab bounded by the lines of contraflexure around the column. The tests were designed to study the effect of openings on the punching shear behavior of the slab-column connections. The test parameters were the location and the size of the openings. One specimen had no opening and the remaining five had various arrangements of openings around the column. All specimens were cast with normal density concrete of approximately 30 MPa compressive strength. The openings in the specimens were square, with the sides parallel to the sides of the column. Three sizes of openings were used: the same size as the column (150 x 150 mm), 67 percent of the column size (100 x 100mm), and 150 percent of the column size (225×225mm). Due to the presence of the openings, the specimens showed a decrease in punching shear capacity ranged between 11.43% and 29.25% with respect to the control solid slab. Also, the stiffness decreased between 0.31% and 83.00%, depending on the size and location of these openings with respect to the column.

Seismic performance of a new precast concrete frame joint with a built-in disc spring

A new, precast concrete frame beam-column connection is designed in this research. The connection adopts the assembly mode of the precast column and seam area jointly to maintain the integrity of the joint area and increase the assembly efficiency. Based on the conventional grouting sleeve connection, a disc spring device is constructed on the beam end to improve the ductility of the joint. Ten connecting specimens were tested under low cyclic loads, including two monolithic connections, four ordinary precast connections, and four new precast connections. The test parameters included the joint type and axial pressure ratio, and the difference in the seismic performance was determined by evaluating the failure mode, hysteresis characteristics, stiffness degradation, energy dissipation, and shear deformation of the joint area. Compared to monolithic connections, conventional precast connections display similar hysteresis characteristics. Although their ductility is slightly lower, their bearing capacity is higher. Compared with the previous two connections, the new connection with the built-in disc spring device has superior seismic performance. The axial pressure ratio is a significant aspect in determining the failure mode of the precast connection, and the specimen exhibits less shear damage at a larger axial pressure ratio.

Seismic Performance of Concrete Column Connection with Square-Upper-Circular-Lower Steel Tube for Antique Buildings

The antique building combines traditional design with contemporary technology, making it an important structural style. Columns, as a crucial structural component, directly affect how well the building functions as a whole. This paper proposes a new connection form with the upper square concrete-filled steel tube-lower circular concrete-filled steel tube (USCFST-LCCFST). This study investigates the seismic performance of the proposed connection form of the columns. First, the finite element software ABAQUS-2021 is used to simulate and analyze the connection forms of the upper square concrete-filled steel tube and lower circular reinforced concrete (USCFST-LCRC) and the upper square steel reinforced concrete and lower circular reinforced concrete (USSRC-LCRC) above the antique building, respectively, which confirms the rationality of the modeling method explored in this paper. Then, geometric modeling of the USCFST-LCCFST connection is performed using ABAQUS. Simulation results demonstrate the superior seismic performance of the proposed connection form. In addition, the influence law of steel tube yield strength and the ratio of upper and lower column linear stiffness on its seismic performance are analyzed and determined through the variational parameter analysis of the USCFST-LCCFST connection form. The steel tube yield strength of USCFST-LCCFST column connection components is recommended to be 355–420 MPa and the ratio of upper and lower column linear stiffness should be no less than 0.063. In order to ensure the good seismic performance of the connection, the steel tube yield strength and the ratio of upper and lower column stiffness should be efficiently controlled in the design of antique buildings’ USCFST-LCCFST column connection components.

Nonlinear parametric assessment of modular prefabricated steel-reinforced concrete composite column subjected to earthquake loading

This study is intended to propose a novel bolted off-site connection for prefabricated steel-reinforced concrete composite (PSRC) column to overcome significant problems involved in the traditional precast concrete connections, such as its complicity under compacted sleeve grouting and insufficient post-cast concrete vibration. Within the context of the study, the seismic characteristics such as failure model, stiffness, and energy dissipation of five PSRC columns subjected to different axial compression and shear-to-span ratios were investigated by conducting low reversed cyclic tests. Thereafter, the accuracy of multiple finite element models (FEM) of the test specimens was verified against the experimental results. In general, the research outcomes showed that the PSRC column has a simple connection structure, efficient assembly, good bearing capacity, and hysteresis characteristics. Under the influence of different parameters, the failure position was located at the middle connection, which was the key to the overall seismic performance. Moreover, it was found that the axial compression and shear-span ratios significantly affect the seismic performance of the joints. The stiffening plate thickness, the cover plate thickness, the square steel tube width-thickness ratio and the middle connection position height greatly impacted the bearing capacity but had an ignorable influence on the ductility, energy consumption, and performance degradation.

Experimental study of CFST embedded precast concrete bridge column-foundation connection with studs

Accelerated bridge construction (ABC) is increasingly gained attention worldwide based on its advantage of high-quality precast elements, less environmental effect, quick construction speed, and minimum traffic block. The seismic performance of prefabricated bridge structures is mainly dependent on the feasibility of connections. To efficiently bear the load from the gravity of other elements and deformation ability in high seismic areas, in this study, an innovative contrete-filled steel tube (CFST) embedded precast concrete bridge column-foundation connection with studs was put forwards. Two 1:2 scale specimens were designed to verify the seismic performance of the proposed connection type. One is a precast specimen with the bridge column-foundation connection, the other is the conventional cast-in-place (CIP) specimen as a reference. The experimental observations and seismic properties were analyzed and compared with those of the CIP specimen, such as failure mode, load-displacement curves, energy dissipation, etc. The finite element model of the precast specimen with bridge column-foundation connection was established and the validated model was used to conduct the parametric study. The precast specimen with bridge column-foundation connection has a larger capacity, ductility, energy dissipation, and equivalent viscous damping ratio than the CIP specimen. Axial compression ratio, embedded depth, and concrete strength affect the seismic performance of the precast specimen with the bridge column-foundation connection. The proposed CFST embedded precast concrete bridge column-foundation connection can be applied to ABC technology in high seismic areas.

Identification of cyber-risks for the control and safety instrumented systems: a synergic framework for the process industry

Malicious interferences to Industrial Automation and Control Systems (IACS) such as the Basic Process Control System (BPCS) and the Safety Instrumented System (SIS) of chemical and process facilities may initiate events with severe consequences such as major accident scenarios (e.g., loss of containment of hazardous substances) and production outages. Existing security vulnerability and risk assessment (SVA/SRA) methodologies, as well as the cybersecurity risk assessment approach proposed by ISA/IEC 62443 series of standards, do not provide any practical method or guideline supporting cyber-risk identification. Moreover, an evident lack of procedures addressing the concrete connection between malicious manipulations of the BPCS and SIS and the impacts on the physical process system that can be initiated, is present in the scientific literature. Given the outlined gap, in the present study, a synergic framework of tools is described and applied to a case study (offshore Oil&Gas platform for gas compression), supporting the systematic identification of the risks that can originate as a result of a malicious interference to the BPCS and SIS. The framework consists of a past incident analysis (PIA) and of two rigorous methodologies, PHAROS, focused on major accident hazards, and POROS, addressing also operability issues. The concept of cyber-attack credibility is here introduced to identify the most credible sets of manipulations based on the score of the plant knowledge level required by the attacker and that of the cyber complexity of the attack pattern, allowing to provide valuable information on how to effectively allocate resources for a more secure network architecture.

Experimental and numerical assessments of new concrete dry connections concerning potentials of robotic CNC manufacturing technique

Coinciding with new manufacturing methods such as robotic additive manufacturing techniques and the gradual transition in construction approaches, new structural elements should be developed that, against the classic approaches, can easily be manufactured by new additive manufacturing techniques. Concrete Dry connections are one of these discussed elements. Appropriate geometries of dry concrete joints, manufactured by robotic CNC technique, accelerate the construction process by eliminating the necessity of formwork, scaffolding and concrete injection. Furthermore, desirable connections with higher interlocking and resistance in different degrees of freedom can be developed by facing the difficulties of traditional construction methods. Through some examples, this paper initially discussed the possibility of constructing dry concrete joints by robotic 3D-printing and robotic milling/sawing methods, and their geometrical accuracy was measured. In addition, 9 geometries of dry concrete joints were proposed and produced by formwork. Then, the performances of the proposed post-tensioned dry joints were discussed and compared to similar monolithic elements. On this basis, certain dry joints, entirely and easily manufactured by additive manufacturing technology (robotic concrete printing and CNC), could achieve up to 64% of the flexural capacity of a dimensional similar monolithic beam.

Bensaïd’s Jeanne: Strategic Mythopoesis for Difficult Times

In this essay, I consider the significance of Daniel Bensaïd’s work on Jeanne d’Arc with regard to dealing with the “difficult times” in which we live. (1) I first consider some of the background in early critical theory in order to show that Bensaïd’s aim to recover Benjamin’s notion of a “weak messianic power” requires following through with Horkheimer and Adorno’s critique of enlightenment, and that this implies a critical rehabilitation of myth and mythopoesis. (2) Approaching Bensaïd’s account of Jeanne in the light of Blumenberg’s notion of “work on myth”, I show how he portrays her in a way that establishes a concrete connection between the discordant temporalities of contingency and necessity, but that this is best understood in the radically immanent terms of prereflective embodied action as based on the corporeal sedimentation of an intercorporeal ethical habitus. Bensaïd’s account of Jeanne thus offers a new lens of historical perception that can help reveal otherwise hidden possibilities for transformative historical agency in embodied coexistence today. (3) By way of conclusion, I briefly consider the deeper meaning and significance of this in terms of offering a non-Promethean mythico-political framework.

Seismic behavior of innovative precast hybrid steel reinforced concrete beam-column connections

This study proposed an innovative partially precast steel reinforced concrete (PPSRC) beam-column connection and experimentally investigated its seismic performance. Four full-scale specimens were designed and tested under cyclic loads. Test parameters are axial compression ratio, concrete type (ordinary concrete or steel-fiber reinforced concrete), and connection type (monolithically cast or precast). Test results were discussed and evaluated, including failure modes, strength, stiffness, degradation, energy dissipation, and ductility. The results showed that the proposed connection effectively shifted the plastic hinge location away from the joint interface by longitudinal bar cut-offs. This type of connection exhibited higher strength, better ductility, and greater energy dissipation capacity compared with the moronically-cast connection. The addition of steel fibers effectively controlled crack propagation and enhanced connection performance, while increase in axial load increased the brittleness of the joint.

Structural behavior of shear deficient high performance reinforced concrete exterior joints under bending

Structural performance of shear deficient reinforced concrete exterior beam-column connections made with Engineered Cementitious Composite (ECC) and Ultra-high Performance Concrete (UHPC) is investigated experimentally and compared with those made of Self-Consolidating Concrete (SCC). Beam-column connections of 1/3rd scale made entirely of ECC, SCC and UHPC as well as ECC-SCC and UHPC-SCC combinations (joint core zone made of ECC and UHPC while the rest made with SCC) are tested under monotonic flexural loading to failure. The performance is compared in terms of failure mode, ductility, energy absorption capacity, stiffness, load/moment-displacement/rotation response, stress–strain characteristics, crack patterns/widths, member flexural/shear strength and joint shear strength. SCC and SCC-UHPC joint specimens have non-ductile beam shear failure and shear failure of the SCC part of the connection respectively, while all others have joint flexural failure. Code based equations significantly under predicted the shear strength of ECC and UHPC joint members. All connections made fully or partially with UHPC and ECC have exhibited higher ductility (1.2 to 1.7 times), energy absorption capacity (3.1 to 15.7 times) and reserve joint strength compared to those with SCC. UHPC incorporated connections exhibited higher strength and energy absorbing capacity, those with ECC showed higher ductility and better crack control characteristics and incorporation of ECC/UHPC can induce desired flexure dominated failure in a shear deficient joint.

Discerning Providence: How the Reign of God in Liberation Theology Explicates Divine Struggle as a Feature of Providence

AbstractRecently there has been rising interest in the doctrine of providence with a number of significant texts being published in English. In general, these and past treatments consolidate established discussions (such as those concerning divine action and causality, human and divine agency and the problem of suffering) rather than engaging liberative theologies of any variety. This article aims to demonstrate how liberative theologies can extend the scope of the study of this doctrine in fruitful ways. In particular, it demonstrates the potential of Jon Sobrino's explication of the Reign of God to reframe explorations of providence around opposition to God's will (described as the anti‐Reign) and the corporate nature of discernment, suggesting that providence is revealed in concrete connection to anthropology and sin in the real world. This reorients reflections on providence towards the theo‐political and practical resistance to the anti‐Reign and participation in the Reign of God in the present reality.

Robber Barons and Wretched Refuse: Ethnic and Class Dynamics during the Era of American Industrialization

Robber Barons and Wretched Refuse: Ethnic and Class Dynamics during the Era of American Industrialization

Experimental and Numerical Assessments of New Concrete Dry Connections concerning Potentials of the Robotic Subtractive Manufacturing Technique

The efficient utilization of robotic construction of structures requires a review of structural material, elements and details, while traditional construction methods face difficulties in producing some dry concrete joints, robotic methods can manufacture them efficiently. With the rapid advancement of new construction methods, more effort should be directed towards developing new types of joints manufactureable by Additive Manufacturing (AM) methods. Accordingly, considering the potentials of robotic techniques, this article proposes eight new concrete dry joints. Concrete portal frames with two identical joints at the end of the beam are cast and evaluated under bending and shear. The performance of each joint, evaluated by experimental and numerical studies based on the crack distribution and stresses, was discussed. Furthermore, various aspects of the process of robotic subtractive manufacturing of the connections are discussed through the selected printed/milled geometries; likewise, geometrical accuracy by microscanning was measured, proving this technique’s capability (methodology). Based on findings, some proposed joints that can be manufactured entirely and quickly by robotic additive and subtractive techniques structurally can produce the full strength of the monolithic reference section. The range of the capacities and initial stiffness is, accordingly, [50%, 106%] and [51%, 124%] of the monolithic elements.

Theory of Truncation Resonances in Continuum Rod‐Based Phononic Crystals with Generally Asymmetric Unit Cells

AbstractPhononic crystals exhibit Bragg bandgaps, frequency regions within which wave propagation is forbidden. In solid continua, bandgaps are the outcome of destructive interferences resulting from periodically alternating material layers. Under certain conditions, natural frequencies emerge within these bandgaps in the form of high‐amplitude localized vibrations near a structural boundary, referred to as truncation resonances. In this paper, the vibrational spectrum of finite phononic crystals which take the form of a one‐dimensional rod is investigated and the factors that contribute to the origination of truncation resonances are explained. By identifying a unit cell symmetry parameter, a family of finite phononic rods, which share the same dispersion relation, yet distinct truncated forms, is defined. A transfer matrix method is utilized to derive closed‐form expressions of the characteristic equations governing the natural frequencies of the finite system and decipher the truncation resonances emerging across different boundary conditions. The analysis establishes concrete connections between the localized vibrations associated with a truncation resonance, boundary conditions, and the overall configuration of the truncated chain as dictated by unit cell choice. The study provides tools to predict, tune, and selectively design truncation resonances, to meet the demands of various applications that require and uniquely benefit from such truncation resonances.

Bending Strength of Connection Joints of Prestressed Reinforced Concrete Pipe Piles

The connection joint of prestressed concrete pipe piles is a typical steel–concrete structure, and its bending strength has evolved into a critical factor affecting the safety of supporting structures in underground engineering. Based on full-scale bending tests of five specimens of large-diameter prestressed reinforced concrete (PRC) pipe piles and connection joints, as well as the corresponding finite element numerical simulation, the bending bearing and deformation characteristics of connection joints of PRC pipe piles were analyzed, together with the effects of concrete strength, precompression stress, and connection mode of joints. The results showed that the crack resistance of the welded joint of PRC pipe piles was equivalent to that of the pipe pile shaft, but the ultimate bending moment of the joint was about 58–87% of that of the pile shaft. The bending failure mode of the pipe pile joint was mainly manifested in the end plate yielding into a drum shape, with the tension side of the pile hoop and the end plate clearly separated from the pipe pile, and crushed concrete at the upper edge of the pile hoop. The bending strength of the joint can be improved by increasing the bonding strength between the end plates of the joint or embedding Rachel reinforcement in concrete. In addition, synchronously increasing the strength grade and reinforcement ratio of concrete or strengthening the precompression stress of concrete are favorable measures.

Seismic performance of a ductile rod exterior connection system for precast concrete industrial buildings

The seismic performance of a ductile rod system for exterior precast concrete beam-to-column connections was experimentally evaluated. Five full-scale precast concrete beam-to-column subassemblies connected with ductile rods were fabricated, considering various aspects (ductile rod size, prestressing, and flexural/shear capacities). Lateral cyclic loading tests were conducted for the precast concrete connections along with two monolithic reinforced concrete connections. Despite their relatively lower lateral stiffness, most precast concrete connections showed sufficient moment capacities with peak moments at approximately 3% to 4% interstory drifts. The prestressing tendons were effective at enhancing moment and shear strengths of the precast concrete connections, as well as in reducing slip of the ductile rods. The precast concrete specimens generally showed satisfactory seismic performance, fulfilling acceptance criteria specified by the American Concrete Institute. The test results demonstrated that careful considerations are required in the design of ductile rods and high-strength threaded bars to induce stable flexural responses of the precast concrete connections.

Precast Concrete Structural System and Connections

Precast Concrete Structural System and Connections