Search Results (282)

The seismic performance of a proposed bolted angle connector beam-to-column joint with a stiffener (hereinafter referred to as a BACS joint) was investigated utilizing quasi-static tests on six specimens with H-shaped steel members. The failure modes, hysteretic curves, skeleton curves, stiffness degradation, and energy dissipation capacity were analyzed. The test results indicated that the BACS joint exhibited a 28.1% higher moment resistance and a 12.6% greater equivalent viscous damping coefficient compared to a welded connection with the same specifications. Furthermore, when compared to a short-beam spliced connection with comparable steel consumption, the BACS joint demonstrated advantages in both the load-bearing capacity and the energy dissipation. The numerical analysis results based on ABAQUS software demonstrated that increasing the stiffener height could not only enhance the bending capacity and stiffness of the connection, but also promote the relocation of the plastic hinge towards the beam end, thereby improving the failure mode. The increase in the stiffener thickness led to a minor improvement in the bending capacity of the connection, yet the influence of the stiffener thickness on the connection stiffness was limited. Furthermore, the use of steel with a higher strength grade could substantially increase the bending capacity of the BACS joint, while the enhancement in stiffness was relatively modest. Therefore, economic considerations should be integrated into the engineering design process. Full article

The supporting system of super-large cooling towers is crucial for the structural safety of nuclear power plants. The X-shaped reinforced concrete column has emerged as a promising solution due to its superior stability. However, the performance of the cast-in-place base joint, which is a key force-transfer component, requires thorough investigation. This study experimentally investigates the mechanical performance of the joints under ultimate vertical compressive and tensile loads. The loads represent gravity-dominated and extreme wind uplift scenarios, respectively. A comprehensive testing program monitored load–displacement responses, strain distributions, crack propagation, and failure modes. The compression specimen failed in a ductile flexural compression manner with plastic hinge formation above the column base. In contrast, the tension specimen exhibited a tension-controlled failure pattern. Crucially, the joint remained stable after column yielding in both loading scenarios. The result validates the “strong connection–weak member” design principle. The findings confirm that the proposed cast-in-place joint possesses excellent load-bearing capacity and ductility. Therefore, the study provides a reliable design basis for the supporting structures of super-large cooling towers. Full article

Trails in heritage sites are useful ways to engage visitors with the place. Sensory trails proposed in this paper, engaged with the sensory walking method, are designed purposefully to engage the multi-sensory features onsite with prompts to link to the historic sensory elements that have historic and cultural meanings to the heritage sites. Two questions are asked: (1) What process can we follow to design sensory heritage trails? (2) What criteria can be used to evaluate and guide the sensory features on site and from historic documentations? Taking design research as the overarching methodology, this paper reflects on the creation of two sensory trails, Sensing Beyond the Roundhouse and Sensing Around the Anglesey Column, following the Double Diamond framework developed by UK Design Council. An iterative design framework was developed, beginning with the identification of constraints and sensory opportunities through site observations, document analysis, and stakeholder interviews, which leads to interpretations of sensory features to shape storylines and route planning informed by user analysis. It is followed by representing the trails through sensory maps and other low-cost creative formats and then validating proposed trails with communities and stakeholders via pilot walks and feedback sessions. Four criteria are generated to assess sensory features based on engagement and authenticity: their contribution to the authentic historic atmosphere of the site; their ability to trigger imagination and evoke nostalgia; their distinctiveness and relevance to the site’s heritage narratives; and their capacity to encourage physical interaction and embodied engagement. The discussion part argues that sensory trails can be used as place-based strategies to inform urban planning and development around the heritage site through three pathways: catalyst for improvements and developments, connect isolated heritage sites, generate place-based knowledge. Full article

A weak-axis moment connection incorporating a double reduced beam section and a box-reinforced panel zone (WDRBS) is introduced for hot-rolled H-shaped columns. The configuration is intended to shift inelastic demand away from the column face and to constrain weak-axis panel-zone distortion. A series of finite element models is established and calibrated to examine the cyclic response of this connection type. By varying the geometric parameters of the second reduction zone, a closed-form expression for determining its cutting depth (c₂) is formulated, allowing both reduced regions to yield concurrently, i.e., the Optimum State. The numerical investigation demonstrates that connections designed according to this equation exhibit stable hysteresis, limited weld-adjacent plastic ll rightstrain, and sufficient deformation and energy-dissipation capacities. All specimens exhibit plastic rotations greater than 0.03 rad, ductility ratios greater than 3.0, and equivalent viscous damping ratios greater than 0.3. To facilitate engineering implementation using common hot-rolled sections, a simplified method is further proposed to approximate the admissible range of c₂ with practical accuracy. While the length of the second reduction region has only a modest influence on peak strength (approximately 1.5–6%), it markedly affects the failure mechanism and plastic-hinge distribution. A stepwise design procedure for WDRBS connections is accordingly recommended. The study does not consider composite-slab interaction or gravity-load effects, and the findings—based solely on finite element simulations—require future verification through full-scale experimental testing. Full article

To improve the seismic performance of prefabricated structures, this study suggested putting grouted sleeves at the half-height of the column (at the point of contraflexure). A quasi-static test under constant axial load was conducted on the full-scale cast-in-place column and the full-scale prefabricated column connected in half-height. The hysteresis loops, skeleton curves, ductility, stiffness degradation, and energy dissipation capacity were compared. The test results indicate that the prefabricated column connected in half-height exhibited reliable seismic performance. Compared with the cast-in-place specimen, the bearing capacity of the prefabricated column decreased by only 1.45%, the energy dissipation decreased by 5.61%, and the initial secant stiffness and ductility coefficient increased by 8.88% and 9.09%, respectively. ABAQUS finite element software was used to establish finite-element models based on the experimental results. The damage pattern and seismic performance indicators of the two types of columns were verified by resolving issues related to the bonding interface model of sleeve-connected columns and the convergence of the multidimensional constitutive model. The formula for calculating the shear bearing capacity was put forward to evaluate the failure pattern. The study provides a basis for further investigation of the seismic performance of sleeve-connected columns with different connection positions under extreme conditions. Full article

The seismic design of aluminum alloy structures requires specific attention due to the material’s distinct mechanical properties compared to steel, which renders direct application of steel joint design methods inappropriate. This study investigates the seismic behavior of T-shaped aluminum alloy beam–column bolted connections, which consist of 6061-T6 aluminum alloy beams and columns connected by S304 stainless steel connectors via high-strength bolts. A finite element model, incorporating a mixed hardening constitutive model for accurate cyclic response, is established and validated against low-cycle cyclic loading tests. Parametric analyses evaluated the influence of L-shaped connector dimensions on hysteresis response, skeleton curves, stiffness degradation, energy dissipation, and ductility. Results demonstrate that increasing the thickness of the short leg of the L-shaped connector between the beam flange and column flange significantly enhances the ultimate bending moment, with an increase of up to 36.7% per 2 mm increment, alongside improved energy dissipation and ductility. Stiffness degradation follows a natural exponential decay, with residual stiffness between 23.85% and 32.57% at ultimate deformation. An efficiency analysis identifies the most cost-effective measures for seismic design. The primary novelty of this work lies in the successful application and validation of a mixed hardening model for simulating the complex cyclic behavior of T-shaped aluminum alloy connections, coupled with a systematic efficiency-oriented parametric study. The findings offer practical, quantitative guidelines for designing aluminum alloy bolted connections in seismic-prone regions. Full article

Modular steel buildings that employed off-site prefabricated volumetric units offered advantages in construction speed and sustainability. The highly integrated buildings assembled by only column-to-column connections were prone to a global collapse, and beam-to-beam connections could greatly promote the overall mechanical performance. However, cooperative bending performance has not been fully understood from a theoretical perspective, and therefore, a performance-based structural design cannot be conducted in practical engineering. In the present study, the laminated double beams in modular steel buildings were theoretically and experimentally investigated. Theoretical models for interfacial slip strain and slippage were established based on differential equations, accounting for both frictional and bolted connection types. In addition, mathematical expressions for bending curvature incorporating interfacial slip were derived, leading to a theoretical procedure for calculating the equivalent initial bending stiffness. In this way, the mechanical performance of laminated beams was analyzed, and the superimposed bending effect was further evaluated. The results demonstrated that bolted connections improved bending capacity by approximately 8% and increased initial bending stiffness by 17–28% compared to friction-only connections. The proposed stiffness prediction models showed significant agreement with experimental data, providing a theoretical basis for the structural design of laminated beams in modular steel buildings. Full article

This study examines Phase B of the GREENERGY project focusing on the seismic performance and structural health monitoring of a renovated single-story RC frame with brick masonry infills that received significant strategic structural interventions. The columns were confined with basalt fiber ropes (FR, 4 mm thickness, two layers) in critical regions, the vertical interfaces between infill and concrete were filled with polyurethane PM forming PUFJ (PolyUrethane Flexible Joints), and glass fiber mesh embedded in polyurethane PS was applied as FRPU (Fiber Reinforced PolyUrethane) jacket on the infills. Further, greenery renovations included the attachment of five double-stack concrete planters (each weighing 153 kg) with different support-anchoring configurations and of eight steel frame constructions (40 kg/m²) simulating vertical living walls (VLW) with eight different connection methods. The specimen was subjected to progressively increasing earthquake excitation based on the Thessaloniki 1978 earthquake record with peak ground acceleration ranging from EQ0.07 g to EQ1.40 g. Comprehensive instrumentation included twelve accelerometers, eight draw wire sensors, twenty-two strain gauges, and a network of sixty-one PZTs utilizing the EMI (Electromechanical Impedance) technique. Results demonstrated that the structure sustained extremely high displacement drift levels of 2.62% at EQ1.40 g while maintaining structural integrity and avoiding collapse. The PUFJ and FRPU systems maintained their integrity throughout all excitations, with limited FRPU fracture only locally at extreme crushing zones of two opposite bottom bricks. Columns’ longitudinal reinforcement entered yielding and strain hardening at top and bottom critical regions provided the FR confinement. VLW frames exhibited equally remarkably resilient performance, avoiding collapse despite local anchor degradation in some investigated cases. The planter performance varied significantly, yet avoiding overturning in all cases. Steel rod anchored planter demonstrated superior performance while simply supported configurations on polyurethane pads exhibited significant rocking and base sliding displacement of ±4 cm at maximum intensity. PZT structural health monitoring (SHM) sensors successfully tracked damage progression. RMSD indices of PZT recordings provided quantifiable damage assessment. Elevated RMSD values corresponded well to visually observed local damages while lower RMSD values in columns 1 and 2 compared with columns 3 and 4 suggested that basalt rope wrapping together with PUFJ and FRPU jacketed infills in two directions could restrict concrete core disintegration more effectively. The experiments validate the advanced structural interventions and vertical forest renovations, ensuring human life protection during successive extreme EQ excitations of deficient existing building stock. Full article

This study introduces an innovative connection to improve the seismic performance of I-beam–to–concrete-filled circular column joints. The concept employs a steel box with optimized internal and external stiffeners, eliminating continuity and doubler plates to simplify construction. Calibrated finite-element analyses were first conducted to select three configurations for experimental testing under cyclic quasi-static loading, measuring energy dissipation, stiffness, ultimate moment, panel-zone rotation, and strain distribution. The best-performing specimen was then identified, followed by a numerical parametric study varying beam and column dimensions to determine the minimum steel-box thickness beyond which further increases offer negligible benefit and to assess its effect on connection rigidity. Experimentally, stiffeners aligned with beam flanges significantly improved moment capacity, stiffness, and energy dissipation. Based on parametric analyses, connections with appropriate box-to-flange thickness ratios achieved over 95% of the maximum flexural strength and stiffness, confirming the reliability of the proposed non-dimensional design approach. Numerical analyses showed that the proposed non-dimensional thickness ratios accurately predict connection behavior, where appropriate flange-to-box proportions ensure over 95% of maximum flexural strength and stiffness, leading to stable and rigid joint performance. Overall, the proposed detailing offers a constructible alternative to conventional plate-intensive solutions while achieving superior cyclic behavior. Full article

To improve the seismic performance of semi-rigid steel frame beam–column joints connected by T-stubs, reinforced T-stubs formed via wedge-shaped and thickening modifications are proposed. Taking the middle column joints in steel frames as the research objects, three types of beam–column joints are designed by adopting ordinary, wedge-shaped, and thickened wedge-shaped T-stubs. To conduct a comparative analysis of the seismic performance of the test specimens, this study imposes low-cycle cyclic loads on the column ends of each specimen along their major-axis and minor-axis in-planes. This loading protocol is adopted to simulate the dynamic responses of the specimens under bidirectional seismic action. Comparing the macroscopic failure phenomena of the specimens, the influence of reinforced T-stubs on the plastic development mode of the joints is analyzed. Based on seismic indicators such as hysteresis characteristics, skeleton curves, stiffness degradation, and energy dissipation capacity, the energy dissipation capacity of the specimens along the major-axis is greater than that along the minor-axis, but their deformation capacity is slightly reduced. The bearing capacity, energy dissipation, and rotational stiffness could be improved by reinforced T-stubs, but the deformation capacity is reduced to varying degrees. The stiffness degradation rate of the specimen adopting wedge-shaped T-stubs shows a more obvious accelerating trend. Through the comparative analysis of the three specimens based on the energy damage index, the results indicate that wedge-shaped T-stubs significantly increase the damage degree of the specimens, but thickened wedge-shaped T-stubs have a relatively small impact on the evolution of joint damage. Full article

In this paper, we establish the existence and uniqueness of the minimum intrinsic risk equivariant (MIRE) estimator for univariate linear normal models. The estimator is derived under the action of the subgroup of the affine group that preserves the column space of the design matrix, within the framework of intrinsic statistical analysis based on the squared Rao distance as the loss function. This approach provides a parametrization-free assessment of risk and bias, differing substantially from the classical quadratic loss, particularly in small-sample settings. The MIRE is compared with the maximum likelihood estimator (MLE) in terms of intrinsic risk and bias, and a simple approximate version (a-MIRE) is also proposed. Numerical evaluations show that the a-MIRE performs closely to the MIRE while significantly reducing the intrinsic bias and risk of the MLE for small samples. The proposed intrinsic methods could extend to other invariant frameworks and connect with recent developments in robust estimation procedures. Full article

The Building Information Model (BIM) has been increasingly adopted for building maintenance and management. For existing buildings lacking prior digital models, a BIM is often generated from 3D scanned point clouds. In recent years, the automatic construction of simple BIMs comprising major structural elements, such as floors, walls, ceilings, and columns, has become feasible. However, the automated generation of detailed BIMs that incorporate building equipment, such as electrical installations and safety systems, remains a significant challenge, despite their essential role in facility maintenance. This process not only enriches the information content of the BIM but also provides a foundation for evaluating building safety and hazard levels, as well as for supporting evacuation planning and disaster-preparedness simulations. Such equipment is typically attached to ceilings or walls and is difficult to detect due to its small surface area and thin geometric profile. This paper proposes a method for detecting building equipment based on laser reflection intensity, with the objective of facilitating the automatic construction of detailed BIMs from point clouds acquired by mobile laser scanners (MLSs). The proposed approach first corrects the reflection intensity by eliminating the effects of distance and incidence angle using polynomial approximation, thereby normalizing the intensity values for surfaces composed of identical materials. Given that the corrected intensity approximately follows a normal distribution, outliers are extracted as candidate points for building equipment via thresholding. Subsequently, the point cloud is converted into a 2D image representation, and equipment regions are extracted using morphological operations and connected component labeling. Experiments conducted on point clouds of building ceilings and walls demonstrate that the proposed method achieves a high detection accuracy for various types of building equipment. Full article

This study presents a novel structural framing solution designed to improve seismic energy dissipation and limit displacements, aiming to serve as an effective alternative to traditional precast systems employing pendulum-based isolation. While pendulum mechanisms mitigate seismic forces by decoupling the superstructure from ground motion, they are typically characterized by high implementation costs, mechanical complexity, and post-event maintenance challenges. In contrast, the proposed approach integrates seismic performance enhancements within the structural frame itself, removing the dependency on external isolation components. The system leverages a combination of pinned and semi-rigid beam-to-column joints that are tailored for use within dry precast construction technologies. These connection types not only support rapid and labor-efficient assembly but also, when properly detailed, offer robust hysteretic behavior and deformation control under dynamic loading. The research includes both experimental testing and numerical simulations focused on the cyclic response of these connections, enabling a comprehensive understanding of their role in dissipating energy and delaying damage progression. Recognizing the industry’s frequent emphasis on construction speed and upfront cost-efficiency, often at the cost of long-term reparability, this work introduces an alternative framework that emphasizes resilience without compromising construction practicality. The resulting system demonstrates improved post-earthquake functionality and reduced downtime, making it a promising and economically viable option for seismic applications in precast construction. This advancement supports current trends toward performance-based design and enhances the structural reliability of dry-assembled systems in seismic regions. Full article

The need to strengthen existing load-bearing elements (slabs, girders, columns, etc.) is often encountered in practice mainly because existing reinforced concrete structures were previously designed according to provisions and standards that were valid decades ago and no longer comply with currently valid Eurocodes, which provide new load levels and cross-section resistance calculations and, thus, a new level of reliability. Another reason is that the purpose behind the use of existing structures is changing, with these structures often now needing to withstand greater loads than were considered during the design. Many methods of strengthening elements stressed by axial force (pressure, tension), bending, shear, and their combination exist, with a common one being the addition of a new, more load-bearing layer of concrete, fibreconcrete, or ultra-high-performance concrete (UHPC). This experimental study focuses on the point of contact between two concrete surfaces and their modification to increase the bearing capacity of the bonded concrete-to-concrete cross-section. To strengthen the cross-section of the reinforced concrete (RC), a decisive condition is contact between individual layers, which is dependent on the resistance of the new, strengthened member. Connection occurs at the cross-section when the elements placed on top of each other are prevented by any suitable method from moving at the level of their contact surface. In this study, experimental tests were carried out to determine shear resistance using beams with dimensions of 100 × 100 × 300 mm, which consisted of two parts connected diagonally at an angle of 30°. To compare the increase in bearing capacity, the modifications of the contact surfaces and the characteristics of the material used for individual added layers were taken into account. The contact surfaces were either untreated, such as stamping from formwork, or smooth surfaces soaked in water for 48 h. For the modified surfaces, modifications included notches, indents, the use of an adhesive layer, and modifications of surface roughness using a steel brush. All base layers were concreted with the same class of concrete and processed according to the mentioned modifications. Different recipes were used for the upper (over-concreted) layer (part). The most effective processing methods were determined from the obtained results, and the coefficient of cohesion was determined through reverse calculation for individual surface treatments and subsequently compared with the Eurocode values. Full article

To investigate the initial rotational stiffness and ultimate moment of fully bolted connections in panelized steel modular structures, a finite element analysis was carried out on 20 joint models. High-fidelity models were developed using ABAQUS, and their accuracy was confirmed through comparison with experimental tests. A parametric study was performed to systematically evaluate the effects of the column wall thickness in the core zone, internal diaphragm configurations, angle steel thickness, and stiffener layouts on the joint stiffness and ultimate strength, leading to practical optimization suggestions. Additionally, a mechanical model and a corresponding formula for predicting the initial rotational stiffness of the joints were proposed based on the component method in Eurocode EC3. The model was validated against the finite element results, showing good reliability. Three failure modes were identified as follows: buckling deformation of the beam flange, buckling deformation of the column flange, and deformation of the joint panel zone. In joints with a weak core zone, both the use of internal diaphragms and increased column wall thickness effectively improved the initial rotational stiffness and ultimate bearing capacity. For joints with weak angle steel connections, adding stiffeners or increasing the limb thickness significantly enhanced both the stiffness and capacity. The diameter of bolts in the endplate-to-column flange connection was found to have a considerable effect on the initial rotational stiffness, but minimal impact on the ultimate strength. This study offers a theoretical foundation for the engineering application of panelized steel modular structural joints. Full article