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Cladding systems are conventionally designed to serve architectural purposes and protect occupants from the environment. Some research has been conducted in altering the cladding system in order to provide additional protection against natural and man-made hazards. The vast majority of these solutions are passive energy dissipators, applicable to the mitigation of single types of hazards. In this paper, we propose a novel semiactive variable friction device that could act as a connector linking a cladding panel to the structural system. Because of its semiactive capabilities, the device, here termed variable friction cladding connection (VFCC), could be utilized to mitigate different hazards, either considered individually or combined, also known as multihazards. The VFCC consists of two sets of sliding friction plates, onto which a variable normal force can be applied through an actuated toggle system. A static model is derived to relate the device's Coulomb friction force to the actuator stroke. This model is integrated into a dynamic friction model to characterize the device's dynamic behavior. A prototype of the VFCC is constructed using 3D printing. The prototype is tested under harmonic excitations to identify the model parameters and characterized on a set of nonstationary excitations under different actuator stroke lengths. Results show good agreement between the model and experimental data, demonstrating that the device functions as-designed. KeywordsSemi-active damper, Variable friction, Cladding connection, Multi-hazard mitigation, High performance control systems, 3D printing Disciplines Dynamics and Dynamical Systems | Mechanics of Materials | Tribology CommentsThis is the pre-peer reviewed version of the following article: Gong, Yongqiang, Liang Cao, Simon Laflamme, Spencer Quiel, James Ricles, and Douglas Taylor. "Characterization of a novel variable friction connection for semiactive cladding system. " Structural Control and Health Monitoring 25, no. 6 (2018) AbstractCladding systems are conventionally designed to serve architectural purposes and protect occupants from the environment. Some research has been conducted in altering the cladding system in order to provide additional protection against natural and man-made hazards. The vast majority of these solutions are passive energy dissipators, applicable to the mitigation of single types of hazards. In this paper, we propose a novel semiactive variable friction device that could act as a connector linking a cladding panel to the structural system.Because of its semi-active capabilities, the device, here termed variable friction cladding connection (VFCC), could be utilized to mitigate different hazards, either considered individually or combined, also known as multi-hazards. The VFCC consists of two sets of sliding friction plates onto which a variable normal force can be applied through an actuated toggle system. A static model is derived to relate the device's Coulomb friction force to the actuator stroke. This model is integrated in...

Abstract. The alarmingly degrading state of transportation infrastructures combined with their key societal and economic importance calls for automatic condition assessment methods to facilitate smart management of maintenance and repairs. With the advent of ubiquitous sensing and communication capabilities, scalable data-driven approaches is of great interest, as it can utilize large volume of streaming data without requiring detailed physical models that can be inaccurate and computationally expensive to run. Properly designed, a data-driven methodology could enable fast and automatic evaluation of infrastructures, discovery of causal dependencies among various sub-system dynamic responses, and decision making with uncertainties and lack of labeled data. In this work, a spatiotemporal pattern network (STPN) strategy built on symbolic dynamic filtering (SDF) is proposed to explore spatiotemporal behaviors in a bridge network. Data from strain gauges installed on two bridges are generated using finite element simulation for three types of sensor networks from a density perspective (dense, nominal, sparse). Causal relationships among spatially distributed strain data streams are extracted and analyzed for vehicle identification and detection, and for localization of structural degradation in bridges. Multiple case studies show significant capabilities of the proposed approach in: (i) capturing spatiotemporal features to discover causality between bridges (geographically close), (ii) robustness to noise in data for feature extraction, (iii) detecting and localizing damage via comparison of bridge responses to similar vehicle loads, and (iv) implementing real-time health monitoring and decision making work flow for bridge networks. Also, the results demonstrate increased sensitivity in detecting damages and higher reliability in quantifying the damage level with increase in sensor network density.

Cladding systems typically serve architectural purposes and protect occupants against the external environment. It is possible to leverage these systems to enhance structural resiliency. A common application is the use of blast resistant panels for enhanced protection against man-made hazards, whereas energy is dissipated through sacrificial elements. However, because these protection systems are passive, their mitigation capabilities are bandwidth limited, therefore targeting single types of hazards. The authors have recently proposed a novel variable friction cladding connection (VFCC), which enables the leveraging of cladding inertia for mitigating blast, wind, and seismic hazards. The variation in the friction force is generated by an actuator applying pressure onto sliding friction plates via a toggle system. Previous work has characterized the dynamic behavior of a VFCC prototype, and established design procedures for blast mitigation applications. Here, work is extended for applications to wind mitigation. An analytical model is developed to characterize the dynamic behavior of the VFCC for wind-induced vibrations. A motion-based design framework is developed to enable an holistic integration of the device within the structural design phase. Numerical simulations are conducted on a 24-story building example to demonstrate the motion-based design methodology. Results show that the semi-active cladding system provides significant reduction in the wind-induced inter-story drift and floor acceleration, therefore demonstrating the promise of the VFCC for field applications.

Cladding systems are conventionally designed to serve an architectural purpose and provide environmental protection for building occupants. Recent research has been conducted to enhance structural resiliency by leveraging cladding systems against man-made and natural hazards. The vast majority of the work includes the use of sacrificial cladding panels and energy dissipating connectors. These passive protection systems, though effective, have typically targeted a single hazard one-at-a-time because of their limited frequency bandwidths. A novel semi-active friction connection has been previously proposed by the authors to leverage the cladding motion for mitigating blast and wind hazards. This semi-active friction device, termed variable friction cladding connection (VFCC), is designed to laterally connect cladding elements to the structural system and dissipate energy via friction. Its variable friction force is generated onto the sliding friction plates upon which a variable normal force is applied via actuated toggles. Because of its semi-active capabilities, the VFCC could be used over wide-band excitation frequencies and is thereby, an ideal candidate for multiple hazard mitigation. The VFCC in its passive in situ mode has been previously designed to mitigate air-blast effects towards the structure and its semi-active scheme has been applied to wind hazard mitigation. In this paper, a motion-based design (MBD) procedure is developed to apply the VFCC to seismic hazard mitigation, completing its application against multiple hazards. The MBD procedure begins with the quantification of seismic load and performance objectives, and afterwards, dynamic parameters of the cladding connection are selected based on non-dimensional analytical solutions. Simulations are conducted on two example buildings to verify and demonstrate the motion-based design methodology. Results show the semi-actively controlled VFCC is capable of mitigating the seismic vibrations of structures, demonstrating the promise of the semiactive cladding system for field applications.