•A Gaussian residual is computed from vibration data in reference and damaged states.•Modal truncation is addressed for the evaluation of the residual sensitivity with respect to finite element model ...parameters.•Hierarchical clustering allows the treatment of large or redundant model parameterizations.•Statistical hypothesis testing with the minmax approach allows damage localization.•An application on ambient vibration data from a 3D steel frame, the Yellow Frame at UBC, validates the approach.
Damage diagnosis is a fundamental task for structural health monitoring (SHM). With the statistical sensitivity-based damage localization approach, a residual vector is computed from vibration measurements in the reference and the damaged state. The residual is analyzed statistically in hypothesis tests with respect to change directions defined by the sensitivities of the structural parameters associated to elements of a finite element (FE) model of the investigated structure. If the test for a parameter reacts, then the respective element of the structure is indicated as damaged. This approach offers a very generic and theoretically sound framework to analyze parametric changes in systems, and takes into account the intrinsic statistical uncertainty related to measurement data. Depending on the definition of the residual and of the parameterization, the approach offers a simple computation of the test statistics directly from the measurement data in the damaged system, without the need of system identification. Since an FE model is used, the approach is applicable on arbitrary structures, while no model updating is required and therefore the requirements on the FE model accuracy are less strict. While the theoretical framework has been developed previously, it lacked robustness so far for an application on real structures. The purpose of this paper is the development of this framework into a working damage localization method that is applicable on real data from complex structures. To achieve this goal, robust hypothesis tests are used, the sensitivity computation of the residual is revisited for more precision thanks to reduced modal truncation errors, and an adequate clustering approach is proposed for the case of a high-dimensional FE parameterization for complex structures. Furthermore, several robustness properties of the method are proven. Finally, an application of this framework is shown for the first time on experimental data for damage localization, namely in an ambient vibration test of a 3D steel frame at the University of British Columbia.
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For decades, engineers have assessed and analysed steel frames using simple joints between beams and columns. These joints are often based on oversimplified assumptions using hinges or a direct ...transfer of beam displacements without any relative displacements. More seldom is the use of spring models that allow relative beam and column displacements at the joints. This despite the standardised component method approach, which can be used to determine the rotational spring stiffness of the relative rotation in a joint. This paper gives a background overview of essential developments in joint modelling and generalised thin-walled beam modelling, including torsional, distortional and related warping effects. For particular situations, some recent proposals for joint models can be applied to joints between thin-walled beams. On this basis, this paper presents a novel idea and a generic methodology that allows the interface between an extended number of generalised beam displacement modes and joints that are modelled using shell elements. The main novelty is the idea to transform from standard degrees of freedom of the interface into a reduced number of beam displacement mode related degrees of freedom. Thus, the number of degrees of freedom of the joint can be reduced to the corresponding total sum of beam modes that have been chosen for the modelling of each of the connected beam elements. The total number of degrees of freedom used for modelling the complete framework will depend on the selected number of modes in each beam element and on the number of extra internal modes chosen in the joint models. For enhanced structural analysis with advanced beam elements and joints that allow relevant distortions and built-in refined connection components, it is believed that this methodology will enable the full detailed analysis of large steel frameworks with a reasonable number of degrees of freedom.
•A full displacement‐based mode formulation to analyse thin‐walled frames.•Illustration of activated beam modes by intensities and mode transmission.•A novel transformation of standard degrees of freedom into mode‐based degrees of freedom.•A review on the development of transmission and modelling of joint stiffness in frames.•A review on the development of advanced elastic thin‐walled beam theories.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
AbstractThis paper proposes a new mechanics-based model for the seismic design of beam-to-column panel zone joints in steel moment-resisting frames. The model is based on realistic shear stress ...distributions retrieved from continuum finite element (CFE) analyses of representative panel zone geometries. Comparisons with a comprehensive experimental data set suggest that the proposed model predicts the panel zone stiffness and shear strength with a noteworthy accuracy, even in panel zones featuring columns with thick flanges (thicker than 40 mm), as well as in cases with high beam-to-column aspect ratios (larger than 1.5). In that respect, the proposed model addresses the limitations of all other available models in the literature. If doubler plates are deemed necessary in the panel zone design, the CFE simulations do not depict any doubler-to-column web shear stress incompatibility, provided the current detailing practice is respected. Hence, the total thickness of the column web and doubler plates should be directly used in the proposed panel zone model. The panel zone shear strength reduction due to the axial load effects should be based on the peak axial compressive load, including the transient component due to dynamic overturning effects in exterior joints. It is found that the commonly used von Mises criterion suffices to adequately predict the shear strength reduction in the panel zone.
In the context of a low environmental impact energy mix, the embodied energy of building materials can account for up to 46% of a building's life cycle energy over a 50-year service life. Fifty ...percent of this energy corresponds to the combination of the structure and building envelope. While most studies have compared different residential building systems or wall assemblies, this study aims to quantify the contribution of initial embodied impacts to the environmental impacts of wall assemblies' life cycle for the exterior walls of an office building in Quebec City (Canada). Cradle-to-grave life cycle assessments were conducted on eight wall assemblies, three of which use light-frame construction, one lightweight steel framing, two cross-laminated timber and two glued-laminated timber in a post and beam approach. The life cycle impacts were evaluated using openLCA, the ecoinvent database and the TRACI method. Energy consumption during the use stage was simulated using EnergyPlus. The results indicate that initial embodied impacts can account for 40% to 66% of all environmental impacts throughout the wall assemblies' life cycle. These results suggest that, in this specific context, the initial embodied impacts can become the dominant source of environmental impacts in wall assemblies' life cycle. Many factors have been identified as affecting initial embodied impacts such as the choice, the quantity and the nature of materials. The results of this study will help decision makers to identify where efforts should be made to reduce a building's environmental impacts in similar context.
•The energy mix context affects the initial embodied impacts' contribution.•Initial embodied impacts can account for 40%–66% of all environmental impacts.•The choice, the quantity and the nature of materials affect environmental impacts.•Some parameters affect LC stages' contribution as per sensitivity analyses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A new all bolt-connected prefabricated steel frame structure (ABPSFS) was presented.•Shaking table test of a 1:4 scaled ABPSFS model was conducted.•Dynamic properties, seismic responses, and failure ...modes of ABPSFS were analyzed.•Dynamic failure mechanism of column-to-column bolted flange connection (CBFC).•Performance objectives for the seismic design of ABPSFS were proposed.
To study the seismic performance of an all bolt-connected prefabricated steel frame structure (ABPSFS), a shaking table test was conducted of a 1:4 scaled ABPSFS model in which high-strength bolts were used for column-to-column and beam-to-column connections. The dynamic properties, seismic responses, and failure mechanisms of the ABPSFS under different peak ground accelerations (PGAs) were analysed. This research also examined the dynamic failure mechanism of column-to-column bolted flange connections and proposed corresponding performance objectives in the seismic design of ABPSFS. The results indicated that the failure modes of ABPSFS were the warping of flange plates, the slipping of washers in bolted joints, and the cracking of concrete floors. With an increase in PGA, the fundamental frequency and stiffness of the structural model decreased while the damping ratio increased. The splicing layer became the weak layer of the entire structure and its acceleration amplification coefficient significantly increased in line with PGA. The dynamic failure mechanism of column-to-column bolted flange connection (CBFC) was buckling of the flange plate, opening of flange gap, and bolt fracture. For ABPSFS, 1/350 rad is recommended as the elastic storey drift angle and 1/70 rad as the elastic–plastic storey drift angle.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The deformation laws of shallow loess tunnel was analyzed.•The optimal setting angle of foot reinforcement bolt was calculated.•The influence of setting angle of FRB on tunnel deformation was ...analyzed.
During the construction of shallow tunnel in loess, installation angle of foot reinforcement bolt (FRB) has a significant effect on settlement at tunnel vault. In this paper, according to the failure modes of shallow tunnel in loess, considering the internal force transmission, deformation coordination, and arch foot displacement between the steel frame and the FRB, a mechanical calculation model for joint load-bearing and displacement of the steel frame for primary support and the FRB is proposed, and found that the maximum anti-sliding force is at angle of 47 degrees of FRBs. The calculated angle is used at different sections of the Jianzicha No. 2 tunnel, measured settlement and deformation of the tunnel vault in field tests showed the angle is applicable in construction. By using the finite element simulation, the influence of anchor pipe angle on the settlement of tunnel vault was studied. The results showed that, FRBs at 47 have the best effect in controlling settlement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
AbstractThis paper presents results from 21 large-scale experiments on steel columns that examined their collapse behavior as related to steel moment resisting frames (MRFs). The test specimens ...included wide-flange and square hollow structural shapes (HSS) and were tested until complete loss of their lateral load-carrying capacity. The test results suggest that the collapse rotations of steel columns under collapse protocols, representing near-fault events, are two to three times larger than those of their counterparts under standard symmetric cyclic protocols, regardless of the examined cross-sectional compactness. Conversely, when ground motion duration is an important seismic hazard characteristic, the collapse behavior of steel columns is reasonably traced with a standard symmetric cyclic protocol. It is shown experimentally that steel columns have an inherent reference energy dissipation capacity regardless of the employed loading history. Axial shortening attributable to local buckling is up to 10 times larger in interior than in end columns, which leads to differential axial shortening within a steel MRF story even at modest lateral drift demands during subduction zone seismic events. The test data underscore that the formation of local buckling at a column’s fixed end caps the strain demands at about 1% near complete joint penetration welds between the column and the base plate, even when the transient axial load demand becomes tensile. Simpler welds may provide adequate ductility in steel columns featuring cross sections near the compactness limits for highly ductile members according to current design standards. It is shown that the estimated rotations by current ASCE 41 acceptance criteria for collapse prevention are 5–10 times smaller than the measured collapse rotations, even for columns with moderately compact profiles.
This study designed and manufactured a 1/5‐scale model of a three‐story steel frame structure. Various types of ground motions, including non‐long period (NLP) ground motions, near‐fault pulse type ...(NFPT) ground motions, and non‐pulse long‐period (NPLP) ground motions, were selected following the site conditions of the structure. The multiple unidirectional single‐particle damper (MUSPD) and its layout schemes were then designed. A series of shaking table tests for the three‐story steel frame with and without MUSPD were performed. Subsequently, a mechanical model of the multi‐degree‐of‐freedom structure with MUSPDs was established, and a corresponding numerical simulation method was proposed. The results revealed that MUSPDs achieved an average damping rate of 18.24% for peak and 27.41% for Root Mean Square (RMS). Notably, MUSPD exhibited a superior damping effect on the RMS of the structure compared to the peak. The distributing floor particle mass according to the first‐order mode of the structure resulted in excellent damping performance. Additionally, determining the particle movement distance for each floor involved calculating the optimal distance using a single‐degree‐of‐freedom structure. MUSPDs exhibited a better damping effect under NLP ground motions compared to NFPT and NPLP ground motions. The shaking table test results confirmed the rationality and feasibility of the proposed numerical simulation method, demonstrating a high level of accuracy.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The progressive collapse resistance of seismically designed steel braced frames is investigated using validated computational simulation models. Two types of braced systems are considered: namely, ...special concentrically braced frames and eccentrically braced frames. The study is conducted on previously designed 10-story prototype buildings by applying the alternate path method. In this methodology, critical columns and adjacent braces, if present, are instantaneously removed from an analysis model and the ability of the model to successfully absorb member loss is investigated. Member removal in this manner is intended to represent a situation where an extreme event or abnormal load destroys the member. The simulation results show that while both systems benefit from placement of the seismically designed frames on the perimeter of the building, the eccentrically braced frame is less vulnerable to progressive collapse than the special concentrically braced frame. Improvement in behavior is due to improved system and member layouts in the former compared to the latter rather than the use of more stringent seismic detailing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Real-time hybrid simulation (RTHS) is an alternative to shake table testing.•Stability of RTHS loop is dependent on appropriate compensation of actuator dynamics.•An adaptive model reference ...controller (aMRC) is presented for RTHS applications.•The aMRC enhances actuator tracking even in the presence of modeling uncertainties.•RTHS and reference structure performances match closely because of the aMRC.
The real-time hybrid simulation (RTHS) methodology is an experimental technique involving substructuring of a full-scale experiment into numerical and experimental partitions. It offers a cost-effective solution and is highly practical in confined laboratory settings. Successful implementation of RTHS is dependent on successful tracking control and robustness of the hybrid simulation loop. This paper addresses the benchmark problem in RTHS, which intends to assess available actuator tracking controllers and other advanced computational frameworks for successful RTHS implementation. Most existing control algorithms tend to instability when faced with challenges of plant uncertainty and nonlinearity. Stability has been at odds with excellent tracking, where controllers with rigorous tracking have had poor stability performance and robust controllers have had poor tracking performance.
This paper introduces an Adaptive Model Reference Control (aMRC) method for displacement tracking of actuators, which offers an excellent tracking ability and maintains robustness under unmodeled dynamics and uncertainties. The proposed controller is composed of feedforward and feedback links, a reference model, and an adaptation law. The tracking and robustness performance of the proposed algorithm are evaluated through a numerical RTHS of the three-story steel frame building described in the benchmark problem statement. The benchmark problem defines different mass and damping configurations while partitioning the structure. Additionally, the experimental substructure is made uncertain by modeling several actuator and stiffness parameters probabilistically, per the benchmark problem. The performance of the proposed controller is compared to several commonly employed control techniques and assessed using the evaluation criteria described in the benchmark problem statement. The results show that the proposed aMRC algorithm tracks the desired reference signal well while maintaining robustness.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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