Car fire tests were conducted on fiber reinforced polymer (FRP) reinforced columns to evaluate the fire effects on piloti structures. The study involved a mid-size car (1,998 cc) with fuel and tire air pressure removed to reduce the risk of explosion. The objectives were to measure the heat release rate (HRR) and temperature distributions during the fire and to evaluate the fire behavior of the columns in the piloti structure. Results from the car combustion test showed a total heat release of 5,210 MJ, with a maximum temperature of 455.0 degrees C at 2.5m height above the car ceiling and an internal temperature of 1025.7 degrees C near the ignition point at the car seat. In the piloti structure fire test, consisting of four reinforced concrete (RC) columns with and without FRP reinforcement and a roof slab, the maximum temperature reached 728.5 degrees C under the slab. Thicker FRP reinforcement resulted in lower temperatures on the column surface. Fire Dynamics Simulator (FDS) software was used to validate the test results and showed accurate predicted temperatures at 3m (within 10 % error). However, discrepancies were observed at 2.5m (24 % error) and below, although the simulated fire behavior agreed well with the test results for heights of 2.0m and above.

Linear sliding electrostatic motors operate based on the Coulomb force between charges in repeatedly patterned electrodes in a slider and stator configuration. We present a model for linear electrostatic motors derived from the assumptions of the electric fields that formally provide the physical relationship between the motor design and the capacitance matrix. The cross-sectional actuation force is obtained with the capacitance matrix and explored for various motor parameters. We also extend the model for generic skewing patterns, five of which are shown representatively with their influences on the actuation force. The experimental results validate the derived capacitance matrix, the model for skewing patterns, and the resultant model of the actuation force. Overall, our model provides an insight into the effects of the parameters involved in the derivation of the actuation force.

As the frequency of earthquakes has risen globally, the importance of seismic design in building construction has intensified. Fiber-reinforced polymers (FRP) are increasingly utilized as seismic reinforcement materials for reinforced concrete (RC) columns because of their lighter weight and superior strength compared to concrete and steel. However, the epoxy resin commonly used for FRP reinforcement is susceptible to fire, as it exhibits a glass transition temperature below 100 degrees C, and its performance can vary depending on the skill of the applicator. A method was therefore proposed to involve the non-adhesive application of FRP panels using corner angles and angle connections, eliminating the need for epoxy resin. Experimental and analytical studies were conducted to assess the shear performance of FRP-reinforced RC columns without adhesive attachment. The findings revealed that the maximum shear force capacity increased by more than 1.5 times compared to traditional RC columns. By securing the corner angle and FRP panel with angle connection materials, the attachment effect can be maximized to the extent of the corner angle area, suggesting its potential for enhancing shear performance.

In this study, the influence of elevated temperature on the mechanical properties of the cement-based mortar with sands and refractory materials was investigated at 200, 400, 600, 800, and 1000 °C. Four different samples were prepared: two samples are general cement-based mortars with a cement to sand ratio of 1:1 and 1:3 (11C and 13C), and the other two are fire-resistant mortars that utilize silica fume/alumina and geopolymer as refractories (FRC and FRG). From microstructural investigation, it was shown that the matrices of FRC and FRG with refractory materials remained as comparatively denser structure with less defects than 11C and 13C with sands at high temperatures. To investigate pyrolysis behavior at elevated temperatures, thermogravimetry and differential thermal analysis were conducted. As a result, minimum weight loss was seen for the FRG sample at high temperatures, while there is seen relatively large weight loss for the 11C and 13C. The compressive strength was observed as 50, 41, 64 and 31 MPa for the pristine 11C, 13C, FRC and FRG samples, respectively, and it decreased to 9.0, 5.2, 15 and 9.7 MPa when exposed to 1000 °C owing to the increased defect structures. FRC exhibited superior compressive stress for all temperatures. On the other hands, FRG showed the lowest compressive stress below 600 °C, while the compressive stress above 800 °C surpasses that for the general cement-based mortars (11C and 13C). Comparably better thermal stability of FRG at very high temperatures seem to be due to geopolymer, which provide denser microstructures and the least weight losses.

Muscles in animals and actuation systems in advanced robots consist not of the actuation component alone; the motive, dissipative, and proprioceptive components exist in a complete set to achieve versatile and precise manipulation tasks. We present such a system as a linear electrostatic actuator package incorporated with sensing and braking components. Our modular actuator design is composed of these actuator films and a dielectric fluid, and we examine the performance of the proposed system both theoretically and experimentally. In addition, we introduce a mechanism of optical proprioceptive sensing utilizing the Moiré pattern innately generated on the actuator surface, which allows high-resolution reading of the position of the actuator without noise. The optical sensor is also capable of measuring the force exerted by the actuator. Lastly, we add an electroadhesive brake in the package in parallel with the actuator, introducing a method of mode switching that utilizes all three components and presenting control demonstrations with a robot arm. Our actuation system is compact and flexible and can be easily integrated with various robotic applications.

A vertical diaphragm scheme is proposed to connect the concrete-filled thin-walled steel tube (thin-walled CFT) column and steel beam, as an alternative to horizontal diaphragm connections: dual vertical diaphragms are installed inside the steel tube, considering poor out-of-plane resistance of the thin tube wall. For verification of the moment connection, two experimental programs were carried out. In the first experiment, an ultimate tension test was conducted for flange-to-column connections, to identify the fundamental behavior of the proposed connection (i.e., strength, failure mode, and out-of-plane deformation). The design parameters, such as the thickness, number, and continuity of the vertical diaphragms, were considered. All the test specimens exceeded the design strengths based on a yield line model (i.e., the tensile capacity-to-demand ratios ranged T-u/T-YL = 1.11-1.31), without early fracture of welded joints. In particular, at the design strengths, the tube out-of-plane deformations were more limited with the heavier diaphragms. In the second experiment, beam-to-column connections using prototype I-section steel were tested under cyclic flexure, to verify the joint flexural strength and rigidity as well as the seismic performance. The beam-to-column connections failed by the beam flexural mechanism, whereas damage was marginal at the joint wall (i.e., the flexural capacity-to-demand ratios ranged M-u/M-j = 0.87-1.09). Overall, the dual diaphragms were effective in achieving rigid (full-strength) connections with satisfactory plastic rotation of the beam. On the basis of the test results, design considerations were recommended for the vertical diaphragm connections.

Soft electromagnetic artificial muscles (SEAMs) that use electric currents are reported as their power sources. The proposed actuator consists of fully soft components: microfluidic coils, stretchable magnets, ferromagnetic silicone, and stretchable housings. The soft coils are fabricated by directly printing room-temperature liquid metal on a stretchable substrate, enabling the generation of high-density electromagnetic fields. Based on design optimization through modeling and simulation, the proposed actuators have a characteristic of bistability following the relationships of the forces acting on the components. Depending on the design configurations, the proposed actuators generate contraction and expansion motions as well as vibrations in a bidirectional manner, enabled by electromagnetic actuation. The main advantages of the proposed actuators are fully compliant structures, compact form factors, and short response times, which have not been observed in existing polymer-based artificial muscles. Another advantage is the self-detection of the actuation states by measuring the inductance change in the coils. Last, the modular design fully packaged with a coil and magnets in a soft housing makes it possible to easily resize and reconfigure the robotic systems with multiple actuator modules for different applications. Examples of applications demonstrated are a modular crawling robot, energy-efficient grippers, a multi-degrees of freedom (DOF) soft manipulator, and a high-frequency swimming robot.

Piloti-type buildings have been widely constructed for the convenience of parking. However, the 2016 Gyeongju earthquake and the 2017 Pohang earthquake revealed the vulnerability of these structures to shear in the soft-story structures and local fires in the car parks.[1],[2] To address these issues, seismic retrofitting with carbon and glass fiber polymers (CFRP and GFRP) has been applied to improve the ductility and strength of the structural components.[3] Despite this, few studies have examined the fire performance of seismically designed piloti structures, highlighting the need for further research in this area.[4] In this study, the fire performance of typical piloti building structures with CFRP strengthening was numerically investigated to prevent fire spread through structural fire analysis. A representative type of existing piloti buildings was selected, and a construction method suitable in terms of fire resistance of structural members was proposed through seismic performance evaluation and seismic retrofit design.[4] Possible fire scenarios

In this study, full-scale mock-up tests were conducted to evaluate the deformation behavior of a newly developed deep deck plate with a depth of 300 mm for construction loads. Test parameters were the thickness of the deck plate, span length, use of shoring, and type of loading (in-situ sand and concrete loading). The measured deflections of the deck plates were compared with the calculated deflections. In the sand loading test, the maximum deflection at the final load (6.24 kN/m2) was 27.6 mm for 1.1 mm thick deck plates with a 6.6 m span, and 44.4 mm for 1.4 mm thick deck plates with an 8.4 m span. In the concrete loading test, after casting a 130 mm topping concrete (4.87 kN/m2), the final net deflection was 22.2 mm (L/275) for a 6.6 m span and 40.9 mm (L/193) for an 8.4 m span. The measured deflections were 0.95 to 1.29 times larger than the calculated deflections using the effective moment of inertia according to AISI S100-16. The net deflection under construction load was less than L/180, and the total deflection limit of 20 mm could be met by introducing camber. Measured strains showed that the deck plates remained within the elastic range even at the final load step, indicating that the deflection caused by the construction loads can be assumed to be recoverable.

Extended Abstract In this study, compartment fire test was conducted to evaluate the fire characteristics of steel members in case of a fire for performance-based fire design of steel structures. Two H-sections (H-300×300×10×15) and six rectangular steel tubes ( □ -200×100×9) with a height of 1.0 m were installed inside a compartment of 2,400 mm (B) × 3,600 mm (D) × 2,400 mm (H), which is the same size ISO 9705 room-corner test. Fire intensity was set as a half-scale fire based on the fire load of 17.45kg/m 2 in the living room of the house and 81 wood clips with dimensions of 50mm (B) × 50mm (D) × 730mm (L) were used as a fire source

This paper presents a study to numerically predict fire loads for open car parks of piloti structures subjected to real fire accidents involving car fires and to provide a basis for performance-based fire-resistant design of buildings. Numerical models to simulate the fire in open car parks were built using a computational fluid dynamics (CFD) code, fire dynamic simulator (FDS). A validation study for the CFD modeling methodology of the fire model was performed using previous experimental and analytical studies. Fire scenarios for open car parks subjected to fire and the corresponding simulation matrix were established based on the validated numerical model in consideration of design parameters including the fire source, arrangement of vehicles, structural planning, and material characteristics. Results for the considered fire scenarios in the open car parks were provided using the parametric numerical results, with an emphasis on distributions of temperatures and fire durations.

Concrete-encased-and-filled steel tube (CEFT) columns with a circular tube section can be potentially used for hollow precast concrete (PC) constructions, in which thin PC encasement is used to reduce the lifting weight of a large PC column. In the present study, connection methods were studied for steel beam-CEFT column joints with the thin concrete encasement. Two sets of testing were performed focusing on the local behavior of the connection: 1) monotonic tension test for beam flange-column connections, and 2) cyclic loading test for beam-column joints. In the first test, the local out-of-plane behavior of the flange plate-tube connections and the associated damage mode of the concrete encasement were identified. The load-deformation relationships of the test specimens were evaluated by nonlinear finite element analysis. Based on the results, exterior beam-column joint specimens were designed, and the flexural behavior of the connections was verified under cyclic loading. The joint specimens were strengthened with connection methods such as tension bars, thick steel tube, and vertical continuity plate, inducing the beam failure. In particular, the thick tube and vertical continuity plate were effective in restraining the concrete damage. The tensile and flexural strengths of the test specimens were evaluated using design equations.

Biological muscle is a multifunctional actuator capable of varying its stiffness and damping. The design of similarly multipurpose variable impedance actuators has benefits for improving physical robot interaction, such as by enabling variable impedance manipulators with more capability and greater safety. We present the concept for a soft jamming brake and artificial muscle (SJBAM). By incorporating a jamming brake inside of a pneumatic artificial muscle, we achieve synergistic benefits, which enable new functionalities, improve muscle static and dynamic response, and expand the brake's capabilities. The SJBAM can store elastic energy, such as a pneumatic artificial muscle, and also act as a brake or clutch. By independently controlling the muscle and brake pressures, we can vary the SJBAM's stiffness and damping. We derive models for this actuation concept and examine the performance of the SJBAM both theoretically and experimentally. In addition, we present open- and closed-loop position control demonstrations with a 1-degree-of-freedom manipulator actuated by an antagonistic pair of SJBAMs.

Recent efforts on wearable robots have focused on augmenting the motor performance and/or protecting the wearer's body with lightweight structures. However, providing human-scale force and structural stiffness usually conflicts with the wearability. Inspired by sandwich-structured composites with high structural strengths, widely employed in both nature and man-made structures, a mechanism of selectively stiffening garments (SSGs) utilizing anisotropic cellular cores and rubber-laminated face sheets is proposed. While the proposed mechanism shows a high compliance allowing for conformity to the wearer's body when unjammed, it provides a significantly high force density when jammed, compared to conventional jamming methods, allowing for the ability to adjust mechanical properties based on the designs and materials. In this paper, various designs of the sandwich jamming structures for the SSGs with analytical characterizations and experimental validations are introduced. Potential applications for force and motion assistance are also demonstrated and impacted mitigation.