In the present work, a framework is proposed for the static and dynamic analysis of spatial frame-like structures with geometric and material nonlinearities. The formulation is based on a velocity-based finite-element approach that takes into account nonlinear material properties with the localization of deformations. The distinguishing characteristic of our approach is the interpolation of velocities and angular velocities, which are taken as primary unknowns for the quasi-static and dynamic formulations. Special attention is dedicated to the evaluation of strains using the kinematic compatibility equation. The nonlinear fiber-based stress-strain constitutive law is considered at the level of cross-sections taking into account also plasticity and softening. The proposed methodology is consistent, computationally efficient and robust, and shows excellent performance even in the neighborhood of critical points and in the presence of strong nonlinearities. The performance of the proposed methodology is demonstrated using several numerical examples.

The paper presents an experimental study on the out-of-plane (OOP) behavior of masonry infills in reinforced concrete (RC) frames. Three different types of masonry infills were investigated: burnt clay bricks, fly ash bricks, and autoclaved aerated concrete (AAC) blocks. Five full-scale specimens, each with an aspect ratio of one but different slenderness ratios (half-brick thick and full-brick thick), were subjected to reversed cyclic loading applied through airbags positioned on both sides of the infill. Results showed that the burnt clay brick masonry infill exhibited the highest strength, stiffness, and energy dissipation, followed by fly ash brick and AAC block masonry infills. Full-brick thick specimens demonstrated 4 to 4.7 times the strength, 2.1 to 3.5 times the stiffness, and 2.7 to 4.6 times the energy dissipation capacity compared to their half-brick thick counterparts. At smaller OOP displacements, the energy dissipation was small (about 5%–6% in terms of equivalent viscous damping) but increased rapidly once the masonry units started spalling. The experimental results, in terms of peak strength, were close to the values predicted by recent analytical models, which are based on large data sets of experimental and numerical results. Drift values for various damage states were consistent with those reported in the literature, except for the collapse damage state.

This paper discusses quasi-static cyclic tests conducted on 1:30-scale physical models of RC exterior and knee beam-column joints, with additively manufactured [three-dimensional (3D)-printed] reinforcement cages. These models can be used for centrifuge modeling of RC structures both to study soil–structure interaction problems and to validate system-level assumptions of numerical models used in earthquake engineering. A gypsum-based model concrete is used because at such small scales, it better replicates the tensile strength of prototype concrete and the bond between prototype concrete and reinforcement. Exterior and knee beam-column joint specimens were tested under different levels of axial loads. Comparisons are made between the results of these small-scale tests and full-scale tests that experienced the same failure mode (beam flexural failure). Additionally, numerical models are developed using the OpenSees platform, and their predictions are compared with experimental data. The findings indicate that the tested specimens behave very similarly to their full-scale counterparts. Moreover, the comparison between numerical models and experimental outcomes suggests that commonly employed numerical modeling methods for RC structures effectively predict the component-level behavior of the tested beam-column joints.

To ensure acceptable ductility and post-yield stiffness for bridge piers in seismic regions, double-confined steel (DCS) reinforced concrete (RC) bridge piers could be effective design options. However, steel corrosion is a major problem for the long-term durability and resiliency of such important infrastructures. To protect such bridge columns, this study proposes that the exterior reinforcement layer be constructed with glass fiber reinforced polymer (GFRP) to protect it from deleterious substances and protect the inner steel reinforcement layer. The use of double-confined hybrid (DCH) offers improved distribution and ease of construction. The double-confined section consists of three levels of confinement: unconfined concrete (cover), singly confined concrete (between the two layers of spirals), and doubly-confined concrete (inside the inner layer of spirals or the core). However, one of the main challenges for DCH under lateral loads is finding a balance between durability and ductility requirements. This study delves into the behavior of reinforced concrete (RC) bridge piers, particularly DCS and DCH, under quasi-static cyclic loading. Through comprehensive experimental testing, the research showcased the distinct behavior of DCS and DCH in terms of their lateral load-carrying capacity, damage progression, and ductility. The observed hysteresis loops for both types denoted unique energy dissipation characteristics. Emphasis was given to the performance-based seismic design (PBD) approach, a method now prevalent in design codes. In line with CSA S6-19 guidelines, four performance levels were established, reflecting different damage states. The research further discussed the effective flexural stiffness of these configurations, noting variations based on axial load ratios. Furthermore, a practical design example based on PBD was presented, shedding light on the seismic behavior of RC bridge piers, with a focus on reinforcement configurations.

In this research, the performance of the gusset plate moment connections is experimentally evaluated in a fire condition. To achieve the research goal, 12 specimens are fabricated in a symmetric cross arrangement; accordingly, a single column along with two cantilever beams and gusset plates are considered, and the load is applied at distance from the beginning of the beam. Subsequently, the temperature of the specimens is elevated until the point of connection failure is reached. The effective parameters, including the gusset plate thickness, gusset plate steel grade, vertical load value, gusset plate length, connection type (bolted or welded), gusset plate height, and lateral restraint, are examined. Following the completion of the experiments, time-temperature and temperature-rotation curves as well as failure modes are obtained. Ultimately, the results are compared with the control specimen. The findings indicated that the lateral restraint, the gusset plate steel grade, and the applied load have significant effects on critical and failure temperatures. Lateral restraint and yield strength improvement led to 20% and 10% increase in the failure temperature, respectively. Moreover, elevating vertical load up to three times can cause a substantial 23% reduction in the failure temperature. Last but not least, fire caused a significant change in the connection’s failure modes, where parameters, including length, height, and edge angle of gusset plate, played a crucial role. Finally, by comparing the proposed gusset plate moment connection with previous inquiry prequalified moment connections, it can be concluded that not only the examined connection is cost-effective but also offers satisfactory performance at high temperatures. Noteworthy, it holds the potential for further investigation in future research and application in steel structures.

A novel self-adaptive damper with load bearing, energy dissipation, and self-centering phased adaption performance, known as the “multifunctional phased self-adaptive rotational friction” (MFPSA-RF) damper, is proposed based on the multilevel seismic concept. This innovative damper consists of multiple MFPSA-RF joints and several corresponding connecting plates. Each MFPSA-RF joint comprises three friction plates clamped together by high-strength bolts with prestressed combined disc springs. The friction plates are specifically combined with two types of friction surfaces—planar and wedge-shaped—to enable the damper to exhibit graded self-adaptive behavior. The working mechanism of the damper is elucidated, and a theoretical analysis model is developed to describe its force–displacement relationship. Experimental studies on the damper components and the whole damper were carried out to test its hysteretic behavior and further validated the theoretical analysis model of the MFPSA-RF damper. The results demonstrated that the MFPSA-RF damper exhibits prominent adaptive performance with MFPSA performance, characterized by high stiffness in small deformations, stable energy dissipation in medium deformations, and excellent self-centering capability in large deformations. Furthermore, a mathematical hysteretic model based on the Bouc–Wen model is developed to capture the MFPSA characteristic, and the modified model’s predicted hysteretic behavior aligns well with the experimental results.

To reveal the mechanism by which internal studs enhance the fatigue resistance of concrete-filled steel tubular K-joints (CFST K-joints) and to develop a method for calculating the stress concentration factor (SCF) of CFST K-joints with internal studs (CFST KS-joints), this study conducted full-scale specimen fatigue tests on CFST K-joints with array-arranged and circular-arranged internal studs. The influence of internal studs on the fatigue performance of CFST K-joints was thoroughly analyzed. The equivalent wall thickness theory was introduced, and the wall thickness correction factor was derived. A highly accurate SCF calculation method for CFST KS-joints was established. The research results indicate that the arrangement of internal studs can enhance fatigue life by 100.6% and reduce the SCF by 77.6%. Furthermore, the efficiency of circular-arranged studs is approximately twice that of array-arranged studs. When the undetermined factors mc for CFST K-joints with array-arranged and circular-arranged internal studs are set to 0.002 and 0.019, respectively, the maximum deviations of the wall thickness correction factor a are only 7.98% and 8.20%, respectively. Utilizing the equivalent wall thickness theory, SCF calculation methods for CFST K-joints with array-arranged and circular-arranged internal studs are derived, yielding errors of less than 19.6% and 21.4%, respectively.

Squat reinforced concrete shear walls usually have diagonal shear– or sliding shear–controlled behavior. Due to the lack of experimental data, there is uncertainty on how squat wall design parameters define their behavior modes. Two real-scale tests were conducted at ETH Zurich on specimens of equal geometry and reinforcement, but different axial load ratios (ALR), employing hybrid simulation techniques to apply recorded ground-motion excitation in a quasi-dynamic manner. Specimen HSW01 had an ALR of 4.02%, whereas the ALR for Specimen HSW02 was 8%. Specimen HSW01 failed in sliding shear, exhibited a quasi-ductile behavior, developed a peak resistance of 2,730 kN, and reached a displacement corresponding to a 3% drift ratio without losing the ability to carry its axial load. Specimen HSW02 failed in shear diagonal compression and lost the ability to carry its axial load at a horizontal displacement corresponding to a 2% drift ratio and a peak resistance of 3,360 kN. The crack patterns, crack width, and damage progression observed in both tests are presented. Finally, the results were compared with similar specimens tested using a displacement-driven incremental symmetric quasi-static cyclic test protocol. Hybrid simulations using recorded ground-motion excitation did not affect the failure mode of the specimens but allowed them to sustain larger displacements than those tested cyclically.

This research assesses and compares the seismic performance of four reinforced concrete columns subjected to lateral cyclic loading. Two columns were reinforced with ASTM A955 Grade 75 reinforcement, whereas the other two were reinforced with CSA G30.18 400W reinforcement, each with aspect ratios of 3 and 6. This study aims to lay the foundation for future performance-based seismic design guidelines for reinforced concrete (RC) bridge piers reinforced with stainless steel rebars. This is achieved by delving into various aspects of seismic behavior, including hysteretic response, column ductility, energy dissipation, plastic hinge length, and performance damage states. The ASTM A955 Grade 75 columns showed similar hysteretic behavior to the CSA G30.18 400W columns up to 7.5% drift and ductility level of 4. At failure (20% strength degradation), the stainless steel columns demonstrated comparable drift ratios, albeit a lower overall ductility capacity due to their higher displacement at yield. In terms of energy dissipation, the CSA G30.18 columns showed higher energy dissipation at similar drift levels and at failure compared to the ASTM A955 Grade 75 columns. Evaluation of plastic hinge length prediction models revealed higher discrepancies for columns reinforced with stainless steel reinforcement, and further investigation is warranted. Also, performance damage states, including concrete cracking, cover spalling, stirrup yielding, bar buckling, and bar fracture, showcased material-specific responses and unveiled critical insights about the applicability of code strain limitations and prediction models for ASTM A955 Grade 75 reinforcement. The research emphasizes the need for tailored approaches based on the distinct behavior of stainless steel.

Load-bearing masonry is widely used in North America, offering architects various unit patterns, including running bond and stack bond, for both architectural and load-bearing purposes. However, stack pattern masonry in load-bearing walls faces additional design restrictions compared to running bonds. Many prefer stack patterns for their aesthetics but are often unaware of the structural limitations. These constraints originate from research on unreinforced or ungrouted stack pattern walls, with the misconception arising when horizontal reinforcement or continuous grouting is used. Thus, stack pattern walls may end up, after engineering design, being significantly weaker in flexure than running bond pattern walls. Hence, the primary objective of this study is to investigate the structural behavior of stack pattern and running bond pattern tall masonry walls under constant axial and varying out-of-plane loading. Three running bond patterns and three stack pattern reinforced concrete block masonry walls, each 4.0 m tall ×2.4 m long ×0.19 m thick, were tested under combined out-of-plane bending and axial loading. The test data showed that the failure modes of stack pattern and running bond pattern walls are similar. This study found that the out-of-plane flexural capacity of the stack pattern wall is 8% to 11% lower than the counterpart running bond wall. However, the postcracking behavior of the stack pattern and counterpart running bond walls were found to be similar. Findings from this research suggest that changes to both Canadian Standards Association (CSA) S304 and TMS 402/602 provisions regarding stack pattern masonry are warranted.