•An explicit COD expression was derived considering the elastoplastic behavior of the optical fiber coating.•The presented theoretical COD computations account for the inclination angle between the sensor axis and crack length.•The PPP- BOTDA-Distributed fiber optical sensor demonstrates high accuracy and sensitivity of COD monitoring.
Crack opening displacement (COD) is an essential parameter in fracture analysis of steel structures, and a novel methodology was developed for measurement of COD using high-resolution distributed fiber optical sensors. Based on crack-induced strain transfer mechanism, a theoretical model was firstly proposed to explicitly determine COD of steel element by strain singularity considering both the elastic and elastoplastic behavior of the optical fiber coating. The presented theoretical COD equations consider the inclination angle between the sensor axis and crack length as well. An experimental program of a pre-cracked pure bending steel element was then conducted to confirm the feasibility of the proposed monitoring approach. The PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) with 1-cm-level spatial resolution was used in distributed measurement of strain and determination of COD. Estimated CODs were also compared to those measured using traditional electronic digital display micrometer. The results indicate that the inclination effect of the optical fiber is slight on the COD within the inclination angle range of 30°. This proposed approach demonstrates great promise for high accuracy and sensitivity of COD monitoring applications.
•A novel plug-in modular steel structure (MSS) connection is developed.•Seismic retrofit with self-centering (SC) haunch braces is used for MSS connection.•Seismic performances of MSS and SC-MSS ...connections were evaluated by cyclic tests.•SC-MSS connection has improved stiffness, strength, and SC capability than MSS one.•SC-MSS connection achieves damage mitigation and post-quake functional recovery.
A novel plug-in modular steel structure (MSS) connection with cover plates for assembly efficiency, flexible serviceability, and stable workability is presented in this study. A seismic retrofit solution with self-centering (SC) haunch braces is then utilized for the MSS connection, aiming at damage mitigation and post-earthquake functional recoverability. In order to confirm the structural characteristics and evaluate the seismic behaviors of the MSS and self-centering MSS (SC-MSS) connections. Three corner connections were designed, manufactured, and tested under cyclic reversed loadings, including two MSS connection specimens with different design parameters and one SC-MSS connection specimen. Test results indicate that the two MSS connection specimens havetheabilityto make full development of the plastic strength of the modular beams and fail in the weld tearing, steel fracture, and local buckling of the beam flanges. The higher tenons of the plug-in connector enhance the local strength of the columns, guaranteeing more concentrated plasticity in the beams for better ductility. In comparison to the MSS connection specimens, the SC-MSS connection specimen has greatly improved stiffness, strength and displays the expected flag-shaped hysteretic responses with a satisfactory self-centering capability. The SC haunch braces effectively control the damage development in the connection core region and the surrounding components, mitigate the deterioration of global strength, significantly reduce the residual deformation, and thus achieve functional recoverability of the connection system. Furthermore, due to the prominent contribution of the haunch braces to the stiffness and strength, the SC-MSS connection shows great potential for sustainable and stable energy dissipation. This experimental study offers a reference for the practical design and application promotion of modular steel structures.
Estimation of natural period is indispensable for evaluating dynamic behavior such as wind induced vibration and earthquakes. However, it is complicated to estimation of natural period of truss tower ...supported steel chimney. Because there are many members that making up truss tower, it is impossible to uniquely determine the weight and stiffness of truss tower, and also chimney body weight concentrating on the tower support point height depends on the number of parts to support and the height. This paper presents estimation formula of natural period truss tower supported steel chimney except such kind of complicate process.
•Performance of four basic yielding elements is summarized.•Two historical cases using supports with combined yielding elements are analyzed.•Estimation method of rock squeezing potential is ...reviewed.•Applicability of yielding supports is discussed.•Recommendations for further research based on findings are provided.
The use of yielding supports has proven to be a highly effective measure for tunneling in squeezing grounds because of their agreement with the law of mechanical movement of rock mass. However, there is no well-established design method for yielding supports; hence, the purpose of this review is to discuss the recent advances in the development and application of these supports in squeezing tunnels. The review begins by briefly introducing the history of yielding supports and previous research work, and explaining the importance of investigating this issue. The causes of time-dependent deformation occurring in squeezing tunnels are then explained, and the definition and principle of yielding supports are introduced in Section 2. The working characteristics and mechanical performance of four basic yielding elements energy-absorbing rockbolts, compressible layer, segmental shotcrete with highly deformable elements and steel arch with sliding connections are summarized in Section 3. In Section 4, two case studies are used to illustrate tunnel performance when supported by yielding support systems combining different yielding elements. Section 5 includes a review of rock squeezing potential estimation methods and a summary of the applicability of yielding supports. Final comments on yielding supports are presented in Section 6, followed by recommendations for further research on these supports. Finally, a brief summary of the contents presented is provided in Section 7.
•An autoencoder based framework for structural damage identification is proposed.•It supports deep neural networks for solution of pattern recognition problems.•Dimensionality reduction and ...relationship learning are included in the framework.•Accurate identification results are obtained considering uncertainties and noises.•Numerical and experimental investigations are conducted to validate the approach.
Artificial neural networks are computational approaches based on machine learning to learn and make predictions based on data, and have been applied successfully in diverse applications including structural health monitoring in civil engineering. It is difficult to optimize the weights in the neural networks that have multiple hidden layers due to the vanishing gradient issue. This paper proposes an autoencoder based framework for structural damage identification, which can support deep neural networks and be utilized to obtain optimal solutions for pattern recognition problems of highly non-linear nature, such as learning a mapping between the vibration characteristics and structural damage. Two main components are defined in the proposed framework, namely, dimensionality reduction and relationship learning. The first component is to reduce the dimensionality of the original input vector while preserving the required necessary information, and the second component is to perform the relationship learning between the features with the reduced dimensionality and the stiffness reduction parameters of the structure. Vibration characteristics, such as natural frequencies and mode shapes, are used as the input and the structural damage are considered as the output vector. A pre-training scheme is performed to train the hidden layers in the autoencoders layer by layer, and fine tuning is conducted to optimize the whole network. Numerical and experimental investigations on steel frame structures are conducted to demonstrate the accuracy and efficiency of the proposed framework, comparing with the traditional ANN methods.
•Shaking table test research on prefabricated corrugated steel utility tunnels.•Seismic performance of the tunnel and inside brackets is analyzed and compared.•Displacement response of the soil ...surface is tested and analyzed by DIC.
A series of shaking table model tests were performed to investigate dynamic responses and damage mechanisms of prefabricated corrugated steel utility tunnels holding various brackets and pipelines. Details of the shaking table experimental setup for this kind of new utility tunnel are presented in this paper for the first time. Multiple seismic responses are measured, including the displacement of the soil surface, acceleration and strain of the utility tunnel, pipelines and brackets, as well as the acceleration and dynamic earth pressure of the test soil. The results demonstrate that the model box designed by our lab did not impose an obvious boundary effect. Displacement of the overlying soil above two sides of the utility tunnel was larger than that of the center of the model in the field nearby. The acceleration response of the structure was perfectly consistent with the surrounding soil. Dynamic earth pressures acting against the tunnel sidewall were significantly affected by the tunnel’s mass distribution under strong excitations. Response acceleration varied with different kinds of pipelines and brackets. The peak strain obtained from the suspending bracket was larger than that of the standing bracket. Different types of brackets were suitable for different applications. Both of the utility tunnel and brackets were not yielded under strong ground motions. The results provide valuable insight into the seismic performance of the shallow-buried underground steel structure and the safe design of the prefabricated corrugated steel utility tunnel.
•Predicting fatigue damage is a challenge because of complexity of crack localization.•We develop a general damage model for predicting the elasto-plastic fatigue life.•A new perspective is inspired ...for fatigue damage life-cycle of steel structures.
Fatigue resistance is a key performance for the life-cycle sustainability of materials and structures. Structural members subjected to flexural forces such as spring hinges in origami structures are one of the most commonly existing in nature and engineering practice but predicting their fatigue resistance is a challenge because of complex mechanisms of crack localization, nonstationary amplitudes in the time domain, and the influence of stress gradient due to bending moment. We developed a general lumped damage simulation model for predicting the fatigue life and the associated crack propagation in the full range of elastic and plastic amplitudes. It is found that the developed comprehensive damage model demonstrates a new perspective for fatigue-induced remaining life quantification for engineering structures.
Among different structural elements, floor elements account for the largest portion of the mass and thus the embodied energy of the structures. Therefore, a viable approach to reduce the embodied ...energy of buildings may involve replacing the conventional floor systems with alternative low embodied energy floor systems. This paper investigates the potential reductions in the life cycle energy of the steel structures achievable through the adoption of steel-timber composite (STC) elements as floor and shear wall systems. Evaluating the life cycle energy implications of adopting STC elements is especially important due to the trade-off between their positive and negative effects on embodied energy and operating energy, respectively, when compared to alternative conventional elements with a higher thermal mass including concrete and steel elements. The life-cycle energy of four different structures designed for a building is evaluated by accounting for energy use in material extraction and processing, component manufacturing, transportation, construction, operation and end of life phases. Two steel structures with STC and steel-concrete composite floors and concrete shear walls are considered to evaluate the effects of STC floors on the energy-usage footprint. The third structure is designed with STC floor system and CLT shear walls; and the fourth structure is designed as a concrete structure to provide a basis for comparison between energy footprint of steel structures with STC and reinforced concrete structures. The results indicate that when designing the building with a steel structure, adoption of STC floor and shear wall systems resulted in 107.5% decrease in the embodied energy at the expense of only a slight increase in the operating energy. Furthermore, adopting a steel structure with STC floors was found to result in considerable life cycle energy savings, viz. 895 MJ/m2, when compared with the same building designed with a concrete structure.
Abstract
For the strength check method of expansive stressed grouted clamp for repairing damaged joints of offshore platforms, a simplified method of clamp modeling and the grout check criteria ...suitable for complex joints are proposed. Then, for strengthening two penetration cracks in the PL19-3 offshore platform, the corresponding expansive stressed grouted clamp was designed. And the strength check on the clamp was carried out by ANSYS software employing the suggested method. It is shown that the equivalent stress of steel structure and the Tresca stress of grout ring are all within a reasonable range. This paper provides a simplified design idea for the finite element calculation method of the expansive stressed grouted clamp to repair complex joints.
