The construction industry faces persistent challenges in the aspect of worker safety and health, particularly with the frequently occurring injuries, illnesses, and fatalities caused by falls, struck-by, and ergonomic hazards, among others. The use of steel as a construction material has increased the scale and complexity of projects by introducing more intricate design, production, fabrication, and especially the erection processes which impact the safety and health performance of steelworkers. Studies have shown that steel connection systems, specifically innovative systems such as the intermeshed steel connection (ISC) can play critical roles in moderating the types of hazards steelworkers are exposed to. Using a 2-storey steel frame structure, the study assessed the integration of a safety checklist into Building Information Modeling (BIM) for improved safety planning for an innovative intermeshed steel connection system. The study developed a robust safety library compliant with the Occupational Safety and Health Administration (OSHA) regulation incorporated into the BIM environment. The case study research developed a four-step framework which includes BIM model creation, safety checklist development, checklist integration in the BIM model, as well as safety simulation and analysis. The study also adopted a methodology that utilized the BIM virtual environment to classify and simulate hazard scenarios linking specific corrective actions with OSHA references to prevent accidents and injuries in steel erection works. The findings of the study indicated that the BIM-enabled checklist could provide workers, safety managers, and other stakeholders with information on effective safety measures to be taken in steel erection operations with intermeshed steel connections prior to construction to avoid injuries, illnesses, or fatalities.

Intermeshed steel connections (ISCs) are a novel type of structural joint used in steel frame construction that has recently developed. They are formed by interlocking two steel members, creating a strong mechanical bond without the need for welding or bolting. Fabricated using specialized tools for precise interlocking, they offer advantages in speed, worker safety, and cost-effectiveness over traditional welded or bolted joints. However, while progress has been made in understanding the structural behavior of such connections, comprehensive testing of these connections has yet to be conducted. This study examines the structural performance of beam-to-beam flange ISC using Finite Element Analysis (FEA), with a focus on commonly used industry sections. Critical failure modes are identified. The analysis confirms that ISCs exhibit adequate strength and stiffness in shear and bending, demonstrating their viability as a structural solution. The findings contribute to a deeper understanding of ISC behavior for optimizing their design and application in steel structures. Based on the study's findings, recommendations for future research are provided.

This paper presents the second generation of Minnesota Accelerated Loading Facility (Minne-ALF-2), a laboratory-based loading pavement test stand that simulates the passage of heavy wheel loads moving over a small full-scale pavement test strip. It is shown that Minne-ALF-2 can provide important information related to long-term performance of dowel joints of concrete pavements, as well as useful information which may lead to a better understanding of the mechanics of joints in concrete pavements. The first results of the ongoing test program are also presented in the paper. This initial study of joint behavior during loading and unloading of a joint with hollow dowels reveals an interesting pattern: deflections in the unloading path are different from the deflections at the loading path. It was also found that the residual differential deflections remain after the first loading and unloading cycle. Available finite element models for rigid pavements do not explain these effects. Hence, advanced models of PCC joints explaining the observed above phenomenon are needed for a better understanding of the joint behavior and joint design optimization.

In this article, the benefits for the seismic behavior of a single-story steel structure fitted with a novel Horizontal Self-Centering Structural System (H-SCSS) between the Vertical Lateral Force Resisting Systems (VLFRS) and the floor diaphragm are investigated. A description is provided of the proposed self-centering system which connects the diaphragm to the vertical lateral force system. Nonlinear static, nonlinear cyclic quasi-static, and time history analysis were compared to explore the benefits, understand the limitations, and identify the controlling parameters in the behavior of a prototype special concentrically braced steel frame (SCBF-X, according to ASCE 7–16) with and without H-SCSS. In general, the following results were observed: reduction of residual drift, concentration of energy dissipation in the fuses, increase in the structure ductility, reduction of stresses and inelastic deformations in the vertical lateral resistance systems. These benefits have the potential to lead to reduce the weight of the structure.

The use of prestressed precast hollow core slabs has intensified as technological advances. However, the knowledge of the structural behavior when openings are inserted into this element is still limited, mainly due to the shear force. Therefore, the present study aims to analyze the structural behavior of the shear test of prestressed hollow core slabs with openings. In this paper, three types of hollow core slabs were tested: no openings, a central opening and side openings; using experimental and numerical methodology. The experimental test was carried out in the Federal University of São Carlos, and the numerical analysis used the software ABAQUS. All results were compared with three standard formulations (i.e., NBR, ACI and Eurocode), in order to verify its accuracy. In the end, the numerical results demonstrated that the developed model (CDP) presented results close to the experimental results. For the hollow core slab with a central opening, a rupture occurred in the web adjacent to the opening. On the other hand, for the hollow core slab with side openings, the rupture occurred at the edge of the web. Therefore, it was possible to conclude that the openings influence the main web tensions, being responsible for the diagonal model stress rupture. Finally, the Brazilian and Eurocode standard formulations proved to be good estimators of the resistant shear force.

Unbonded post-tensioned (UPT) tendons have been used in structural masonry walls to enhance the self-centering capability of the walls. However, the lateral displacement capacity of masonry walls with UPT tendons can be compromised by early crushing of the compression toes. To prevent toe crushing, this research study employed rubber pads underneath the bottom corners of a full-scale one-story wall. This concept was investigated by subjecting the wall sequentially to free vibration and quasistatic tests, which minimized damage to the masonry and reduced the strength degradation of the wall with increasing lateral drift. Two major damping components were identified: one is due to the instantaneous impact of the wall on the foundation base, and the other is due to the inelastic action occurring within the rubber pads during the continuous phase of rocking motion. Using the test results, a procedure is presented for designing masonry walls with rubber pads and UPT tendons.

Pairing of robotic arms with precision cutting in the form of laser, plasma, and water jet cutting has opened the door to entirely new forms of structural steel connections that can be assembled with no field welding and minimal (if any) bolting. Such connections can offer increased erection speed, decreased safety issues, and in some cases the opportunity for rapid disassembly, thereby creating a pathway for direct reuse. This paper provides an overview on the testing, numerical modeling, and field assembly of one such connection – the Intermeshed Steel Connection (ISC). This paper highlights features and behaviors of this connection when simulated, tested, and erected in a beam- to-beam connection and focuses on compliance, ability to be designed reliably, load transfer between the side plates and the main member, and the relatively rapid speed of erection compared to a traditional fully bolted connection. Because of its limited number of pieces, the connection may enable in-situ robotic assembly.

This paper presents the work carried out on a collaborative tripartite project between the USA, Republic of Ireland and Northern Ireland to create and investigate the design, development and testing of a new class of intermeshed steel connections (ISCs) that do not rely on field welding and minimise bolting, thus targeting the facilitation of fast disassembly of steel structures and material reuse. This research took advantage of fully automated, precise, advanced manufacturing cutting technologies (e.g. laser, waterjet and high-definition plasma cutting) to achieve a connection method in steel that previously was only possible in materials such as timber, with the potential to revolutionise the steel construction industry. The paper outlines the ongoing research work by the collaborative team, focusing on the design, fabrication, finite-element analysis (FEA) and scaled experimental testing of side ISCs for the flanges of open sections, which included the use of state-of-the-art digital image correlation technology for non-contact measurements. A simplified connection design procedure is presented based on yielding of the side plates. This design procedure is refined based on the results of experimental testing and FEA of the local axial behaviour of the flange connection, addressing stress concentrations in the flange, fabrication tolerances and material overstrength.

Ultra-high-performance fiber-reinforced concrete (UHP-FRC) has a high compressive strength of 22 to 30 ksi (152 to 210 MPa) and a substantial shear strength as well as exceptional compressive ductility and confinement characteristics due to the addition of high-strength steel microfibers, which alleviate the need for excessive transverse reinforcement in high-strength concrete. The application of UHP-FRC in seismic-resistant reinforced concrete (RC) columns was investigated in this study. Two full-scale columns, one with normal strength concrete and the other with UHP-FRC in the plastic hinge region, were tested under simulated earthquake loads to evaluate their damage-resistance ability, deformation capacity, and failure mechanism. Experimental results show that the use of UHP-FRC changes the failure mode of RC columns as it improves confinement and shear capacity, as well as prevents concrete from crushing. The UHP-FRC column exhibits a higher peak strength and a greater deformation capacity before succumbing to significant strength degradation compared to the normal-strength RC column. The lateral displacements of the ACI 318-19-compliant RC column mainly result from distributed reinforcing bar yielding. Conversely, displacements of the UHP-FRC column are dominated by the slip deformation at the column-footing interface due to the strain penetration of the longitudinal reinforcing bars into the footing. Unlike the RC column, the failure of the UHP-FRC column is controlled by the low-cycle fatigue life of its longitudinal reinforcing bars. Concrete crushing in the RC column started at 1% drift ratio and became nearly unrepairable beyond 2.75% drift ratio. On the other hand, the UHP-FRC column experienced limited damage even at large drift ratios. This will result in great post-earthquake functionality and considerable cost savings in repairs for structures with UHP-FRC columns. In addition, incremental dynamic analyses of a four-story prototype RC moment frame indicate that buildings with UHP-FRC columns can sustain earthquakes with 20% higher peak ground acceleration before collapsing due to the greater deformation capacity.

The self-centering capability of structural masonry walls can be enhanced with the use of vertical unbonded post-tensioning combined with a rocking mechanism at the wall-foundation interface. However, the lateral displacement capacity of these wall systems is often compromised by early crushing of the compression toes. An experimental research study successfully investigated a new concept to prevent toe crushing by introducing thin rubber pads underneath the bottom corners of a full-scale one-story masonry wall. The wall was subjected to free vibration and quasi-static tests, showing excellent lateral displacement capacity and no observable damage to the masonry. To enable the application of rocking masonry walls with rubber pads and unbonded post-tensioning, this paper presents a design procedure by incorporating different damping components in the response of this wall system, which includes inherent viscous damping, hysteretic action, and energy dissipation due to the wall impacting on the foundation base.

Post-tensioning techniques improve the tensile strength of masonry substantially, endowing posttensioned masonry with performance comparable or superior to that of reinforced masonry cantilever walls. A useful structural application is for retaining walls, and although investigations have been made in posttensioned masonry cantilever walls, most of them focused on grouted elements and in-plane loads. This study investigated the influence of initial prestress and masonry strength in the behavior of ungrouted cantilever prestressed masonry walls with laterally unrestrained post-tensioned bars and which are intended as earth-retaining structures. The study also addresses the accuracy of different prestressed masonry code expressions to calculate the ultimate flexural capacity. The results show the ability of this structural system to withstand large lateral displacements with a limited and concentrated damage zone. The impact of masonry strength when the walls are loaded to ultimate conditions is less evident than that of initial prestress, and the USA and Canadian design code procedures show better correlation between numerical predictions and experimental data than do other worldwide codes.

Despite wide use of terms such as “digital manufacturing” and “digital fabrication” in the constructional steel industry, actual use to date is mostly limited to research and development activities. In contrast, other heavy industries, such as automotive and aerospace have moved much faster and implemented many aspects of digital manufacturing and fabrication in product creation and traditional workflows. As a foil to the current state of the industry, this paper presents the erection, and disassembly of a simple, two‐storey frame that employs an alternative steel connection that can be manufactured using current plasma, laser, and water jet technologies, referred to as the intermeshed steel connection (ISC). The field demonstration described in this paper shows the connection's ability to reduce on site erection time, substantially reduce the number of site bolts, eliminate site welding, and allow for easy deconstruction. The connection has been under testing and development through a consortium of the University College Dublin, Queens University Belfast and, the University of Minnesota.

The presence of effective wall-to-diaphragm connections has been shown to significantly improve the global seismic behavior of unreinforced masonry (URM) buildings. However, despite the importance of such connections, there remains a paucity of experimental research to provide physical validation of current recommendations in design standards and guidelines. The experimental study reported herein included a total of 18 tests which were undertaken in two phases, with Phase 1 testing being undertaken on existing vintage plate anchor connections in an existing URM building and Phase 2 testing involving newly installed plate anchor connections in two additional existing URM buildings. The tested buildings offered variation in material properties, levels of axial load, and wall thickness as test parameters. Attained failure modes and corresponding force-displacement curves are presented herein, as well as comparisons regarding the influence of varying test parameters on the ultimate pull-out capacity. Prediction of plate anchor capacity was undertaken using a basic mechanics approach, and comparisons to current strength recommendations in standards and guidelines are provided.

This paper describes a collaborative project between the US, Ireland, and Northern Ireland (UK) to investigate advanced manufacturing cutting techniques for the creation of a new class of intermeshed steel connections that rely on neither welding nor bolting. To date, advanced manufacturing equipment has only been used to accelerate traditional processes for cutting sheet metal or other conventional fabrication activities. Such approaches have not capitalized on the equipment's full potential. This project lays the groundwork to transform the steel building construction industry by investigating the underlying science and engineering precepts for intermeshed connections created from precise, volumetric cutting. The proposed system enhances the integration between design, fabrication, installation and maintenance through building information modeling platforms to implement advanced connections. Fully automated, precise, volumetric cutting of open steel sections introduces intellectual challenges regarding the load-transfer mechanisms and failure modes for intermeshed connections. The research activity addresses knowledge gaps concerning the load resistance and design of steel systems with intermeshed connections. Physical tests, finite element simulation and multi-scale modeling are being used to investigate the mechanics of intermeshed connections including stress and strain concentrations, fracture potential and failure modes, and to optimize connection geometry.

On November 26, 2019, a magnitude M w = 6.4 earthquake struck Northwestern Albania. It was the strongest to hit Albania in more than 40 years. Cities such as Thumanë, Tirana, and Durrës suffered damage, but Durrës was the hardest hit with several building collapsed [1,2]. A reconnaissance team under the auspices of American Concrete Institute (ACI) visited Dur-rës, Albania to assess the extent of damage to modern reinforced concrete (RC) buildings (i.e. built after 1990). The team *1 surveyed buildings during the week of January 12, 2020, with a focus on RC buildings that were infilled with clay block masonry. Over the course of seven days the team documented 55 buildings that had RC frames as their main lateral resisting sys-tem. All of the surveyed buildings had unreinforced masonry infills (hollow clay blocks). Most of the buildings had ribbed or waffle slabs. Typical damage observed in these buildings was in-*

The aim of the present study is to develop insights into the structural performance of a recently developed ?intermeshed? steel connection, which transfers loads mainly through direct contact rather than by welds or bolts. This investigation was conducted through a step-by-step state assessment of the intermeshed connection subjected to multiple scenarios of gravity loading and by use of a nonlinear finite element platform. Implementation of the intermeshed connection would cause a discontinuity in the beam, so this paper addresses concerns regarding the load-transfer mechanisms and failure modes for these connections. The finite element simulations were performed in Abaqus, which is capable of handling material and geometrical nonlinearity, as well as the contact between individual surfaces. In order to verify the accuracy of these simulations, the numerical results were compared with experimental data from four physical tests. Finally, some important factors of influence such as connection segments sizes, lateral constraint, support conditions, and failure modes were also investigated through numerical analysis. The results of finite element analysis on different prototypes of steel intermeshed connection showed that the specimens with this connection provided sufficient ductility and resistance to meet design requirements.

Advanced manufacturing techniques, such as plasma, waterjet, and laser can facilitate field assembly and disassembly of steel structural components, and therefore potentially transform how steel structures are designed and constructed. These techniques have opened up an opportunity to create a new class of steel connections that rely on intermeshed (i.e. interlocked) components in lieu of traditional connectors such as weld and bolt. This paper presents an experimental investigation on the mechanics of such intermeshed steel connections manufactured by high-definition plasma and waterjet cutting. Four full-scale specimens with an intermeshed connection were designed to resist gravity loading in steel frames. The experimental testing program focused on the behavior of intermeshed connections under vertical loads including pure flexural and combined flexural-shear loading. Both global load-deflection response and local deformation were measured to provide insights into the complex load transfer mechanisms. The experiments demonstrated ample load carrying capacity, approaching the beam plastic moment, and ample ductility, approaching a deflection over span length ratio of 1/60 to 1/40, through the interaction of individual components. Analysis of the test data also raises important questions that must be addressed for the practical design of these connections.

Digital manufacturing has transformed many industries but has had only a limited impact in the construction sector. To capitalize on advanced manufacturing techniques, this paper introduces a radically new connection approach for gravity structural steel frames. The proposed intermeshed steel connection (ISC) exploits robotic abilities to cut structural steel member ends precisely to accelerate deployment and offer better disassembly options over existing approaches. Forces are transferred through common bearing surfaces at multiple contact points, and connections can be secured by small locking pieces. This paper introduces the geometry, manufacturing, and initial analysis and test results of the connection. The paper demonstrates the ability of the connection to (1) be manufactured within current industrial tolerances, (2) be erected and disassembled, and (3) perform at expected design levels.

The investigation of structural single rocking walls (SRWs) continues to gain interest as they produce self-centering lateral load responses with reduced structural damage. The simple rocking model with modifications has been shown to capture these responses accurately if the SRW and its underlying base are infinitely rigid. This paper advances previous rocking models by accounting for (1) the inelastic actions at or near the base of the SRW and (2) the flexural responses within the wall. Included in the proposed advancements are hysteretic and inherent viscous damping associated with these two deformation components so that the total dynamic responses of SRWs can be captured with good accuracy. A system of nonlinear equations of motion is developed, in which the rocking base is discretized into fibers using a zero-length element to locate the associated compressive deformations and damage. The flexural deformations of the rocking body are captured using an elastic term, while the impact events are modeled using impulse-momentum equations. Comparisons with experiments of structural precast concrete and masonry SRWs show that the proposed approach accurately estimates the dynamic responses of different SRWs with and without unbonded posttensioning, for various dynamic excitations and degrees of hysteretic action. Using the proposed approach, a numerical investigation employs different configurations of structural SRWs to quantify the various sources of energy loss, including hysteretic action and impact damping, during various horizontal ground motions.