U-shaped Steel Research Articles

Jet-Pacs Project: Dynamic Experimental Tests and Numerical Results Obtained for a Steel Frame Equipped with Hysteretic Damped Chevron Braces

The experimental and numerical results obtained by Research Units of the University of Basilicata and University of Calabria for a steel frame, bare or equipped with metallic yielding hysteretic dampers (HYDs), are compared. The shaking table tests were performed at the Structural Laboratory of the University of Basilicata within a wide research program, named JETPACS (“Joint Experimental Testing on Passive and semiActive Control Systems”), which involved many Research Units working for the Research Line 7 of the ReLUIS (Italian Network of University Laboratories of Earthquake Engineering) 2005–2008 project. The project was entirely founded by the Italian Department of Civil Protection. The test structure is a 1/1.5 scaled two-story, single-bay, three-dimensional steel frame. Four HYDs, two for each story, are inserted at the top of chevron braces installed within the bays of two parallel plane frames along the test direction. The HYDs, constituted of a low-carbon U-shaped steel plate, were designed with the performance objective of limiting the inter-story drifts so that the frame yielding is prevented. Two design solutions are considered, assuming the same stiffness of the chevron braces with HYDs, but different values of both ductility demand and yield strength of the HYDs. Seven recorded accelerograms matching on average the response spectrum of Eurocode 8 for a high-risk seismic region and a medium subsoil class are considered as seismic input. The experimental results are compared with the numerical ones obtained considering an elastic-linear law for the chevron braces (in tension and compression), providing that the buckling be prevented, and the Bouc-Wen model to simulate the response of HYDs.

Design of Drawing Straightening Machine for Roll-Forming of U-Shaped Steel

The cold-roll-formed profiles usually defects such as bow, camber, twist, edge wave, corner buckling as well as edge cracking, and splitting. Straightening is used as the later part of working procedure in order to eliminate these defects and improve the quality of the final profile. A drawing straightening machine is designed to achieve the purposes of the U-shaped steel straightening. In the design coefficient of friction, forming speed, roll speed, methods to minimize defects.

Experimental Investigation and Nonlinear Finite Element Analysis of U-Shaped Steel-Concrete Composite Beam

U-shaped steel –concrete composite beam is a new form of structure components. Through the test of three groups of specimens, the failure modes of structure components, the strain distribution of cross-section, and the load –deformation relationship are analyzed. A preliminary understanding of mechanical characteristics and deformation performance is got from the experimental investigation. The composite beam element is used to conduct nonlinear Finite Element Analysis. Based on the theoretical calculations and experimental investigation, a practical formula of U-shaped steel- concrete composite beam deformation is established. Moreover, the calculated result is in good agreement with the test results.

Properties Uniformity Analysis of Cold Formed Steel Sheet Piling

Through analyzing the molding process characteristics of cold-formed steel sheet piling, mechanical testing and metallographic analysis was made on the curved position of the U-shaped cold-formed steel sheet piling , the following conclusions was drawn: Cold formed steel sheet pile was subjected to the complex cross-section cold roll forming process, resulting in the uneven performance of a steel sheet piling along the horizontal. For the open cold formed steel of asymmetric steel sheet piling and complex cross section, a simple test at flat panel location is difficult to represent the overall performance of cold-formed steel, therefore it is necessary to make a comprehensive performance test on locking. A test method to check the locking occlusion performance on the cold bending steel plate is put forward. The experimental tensile strength of the Q235 level of ordinary carbon steel production of cold-formed steel sheet piling locking bite is 66MPa.

Cyclic Seismic Testing of Composite Concrete-Filled U-Shaped Steel Beam to H-Shaped Column Connections

In this study, the cyclic seismic performance of a concrete-filled U-shaped steel beam to H-shaped steel column connections was experimentally evaluated. The concrete-filled U-shaped steel beams were compositely attached to the concrete floor slab. The test was conducted in two stages. The first testing program was carried out on one-sided moment connections to find the most promising connecting scheme. The strengthening scheme, or welding steel plates to the beam bottom flange with minimized stress concentration, was shown to be the most satisfactory, and it was used in the second-stage test on two full-scale cruciform specimens. Considering the unique constructional nature of the proposed composite connections, the critical limit states such as weld fracture, local buckling, concrete crushing, and rebar buckling were carefully addressed in designing specimens. Test results showed that the connection details and design procedures proposed in this study can successfully control the critical limit states mentioned previously. The proposed connection detail successfully pushed the plastic hinging to the tip of the strengthened zone as intended in design, thus effectively protecting the more vulnerable beam-to-column welded joint. The specimens typically exhibited a maximum story drift capacity of more than 5.5% rad, exceeding the minimum limit of 4% rad required of special moment frames. Four of the five specimens tested in this study eventually failed because of a low-cycle fatigue fracture across the beam bottom flange at a high story drift greater than 5.0% rad.

Cyclic loading test for concrete-filled U-shaped steel beam–RC column connections

Concrete filled U-shaped steel beams are used to increase the flexural strength and stiffness of the steel beams by using concrete fill. In this study, a seismic detail for the concrete filled U-shaped steel beam–RC column connection was developed. A special detail using diagonal re-bars and welded re-bar connections was used to strengthen the beam–column joints. To verify the seismic performance of the beam–column connection, two full-scale specimens were tested under cyclic loading. The test parameter was the size of the U-shaped steel beam. The depths of the composite beams were 610mm (steel plate thickness=6mm) and 710mm (steel plate thickness=8mm) including the slab depth of 160mm. The test results showed that the specimens exhibited good strength, deformation, and energy dissipation capacities. The deformation capacity exceeded 4% inter-story drift ratio. The primary failure mode of the specimens was buckling and fracture of the steel plate in the beam.

水平2方向載荷下における繰り返し変形性能に関する実験

Evaluation of bi-directional characteristics of base-isolation devices is a very important issue for base-isolated structures. This paper describes a bi-directional loading test of U-shaped steel dampers widely-used for energy dissipation in base-isolated structures. The major findings obtained from the test are as follows: (1) torsion-induced residual deformation leads to contact with damper connections; (2) evaluation method of cyclic deformation capacity, which divides bi-directional orbit into deformations in 0 and 90 degree, is proposed and the validity is verified; (3) cyclic deformation capacity is reduced by cumulative torsion; (4) two indices Jc and Jf proposed in this paper can evaluate the limitation of cumulative torsion until contact with connections and the tendency of torsioninduced reduction of cyclic deformation capacity.

Development of Passive Energy Dissipation Device with U-Shaped Steel Damper Based on Quasi-Linear Motion Mechanism

This paper presents a new energy dissipation device for earthquake protection of structures. The proposed device, which uses a quasi-linear motion mechanism, achieves dissipation of seismic energy into the structure through yielding of U-shaped steel dampers. Consequently bracing members are subjected to only tensile force. Cyclic loading tests of the portal moment frames with the proposed device are conducted. Results and discussions are presented with emphasis on key features which affect energy dissipation capability. The lateral load and story drift angle relationships show that the proposed device provides stable and reasonably large energy dissipation capability. The effect of pre-tension applied to the bracing members is also examined through the brace axial strain and lateral load relationship.

Development of Passive Energy Dissipation Device with U-Shaped Steel Damper Based on Quasi-Linear Motion Mechanism

This paper presents a new energy dissipation device for earthquake protection of structures. The proposed device, which uses a quasi-linear motion mechanism, achieves dissipation of seismic energy into the structure through yielding of U-shaped steel dampers. Consequently bracing members are subjected to only tensile force. Cyclic loading tests of the portal moment frames with the proposed device are conducted. Results and discussions are presented with emphasis on key features which affect energy dissipation capability. The lateral load and story drift angle relationships show that the proposed device provides stable and reasonably large energy dissipation capability. The effect of pre-tension applied to the bracing members is also examined through the brace axial strain and lateral load relationship.

Evaluation of vibration control system with U-dampers based on quasi-linear motion mechanism

This paper presents a new vibration control system for protection of steel structures from earthquakes. The proposed system, which uses a quasi-linear motion mechanism, achieves dissipation of seismic energy into the structure through yielding of U-shaped steel dampers. Based on the linear motion mechanism characteristics, the bracing members are subjected only to tensile force. This feature can eliminate the brace-buckling problem for braces, making rod members applicable to bracing members. This paper presents an outline of the vibration control system with subsequent evaluation of the lateral stiffness and strength of the frames with the proposed device. Six cyclic loading tests are conducted using the frame models with the proposed system. The accuracy of the evaluation is discussed by comparing the cyclic loading test results.

The Stability Control Technology of Crosscut while Mining without Coal Pillar in Steep Seam

In order to improve the mining benefit of coal resources, Chang Gouyu Coal Mine carried out the technology of mining without coal pillar in steep seam. The key of the technology was to ensure a long-term stability of the cross-entry roadway across the seam. Through the analysis of the nature of steep seam roof and floor rock, and based on the stability analysis and loose circle measured of surrounding rock of crosscut roadway, we brought forward adopting shotcrete rockbolt mesh and U-shaped steel complex support structure system. This complex support system could flex lengthways and compress in radial direction. The entirety integrated with the surrounding rock, and they formed into a whole. Application of the complex support system could effectively control the deformation of the surrounding rock collapse, and maintain the stability of the crosscut.

Experimental Study on Infrared Radiation Changes with the Fracture and Progressive Failure of the Submarine Soft Rock Roadway

Based on the submarine soft rock supporting engineering in Beizao Mine, the physical model tests of four kinds of supports were carried out including high strength (HS) roadway without support, HS soft rock roadway with U-shape steel support (U-S-S-S), low strength (LS) roadway with bolt support (B-S), and LS roadway with U-S-S. The thermal infrared (TIR) changes with the fracture and damage of roadway are investigated. It is discovered that the TIR radiation is the stronger in the stress concentrated area, strong friction and interaction range between U-steel support and roadway than that in the stress relaxed area and week friction. The TIR temperature (TIRT) of the fracture increased higher and changed rapidly than other parts. The TIR radiation of soft rock is influenced with seawater. The TIR-anomaly appears at the stress concentrated area, interaction ranges and fractures. The TIR omens occur when load is 65%~90% of the peak load.

직교자계가 디펌성능에 미치는 영향

An orthogonal magnetic field is often used for a military vessel in the deperm process such as Flash D deperm protocol and Anhysteretic deperm protocol. The effect of the orthogonal magnetic field on a deperm performance was investigated for a sample with strain-induced magnetization and field-induced magnetization given to different direction. A 70mm wide, 110mm long and 0.25mm thick rectangular steel plate was bent to have U-shape and to generate a strong strain on the bottom region of U-shaped steel plate. Field-induced magnetization was attached by NdFeB permanent magnet. Demagnetization was performed by applying magnetic field with a step decrement from the first field(the first shot) under the action of DC bias field.

Experimental Investigation on the New-Type Outer-Plated Steel-Concrete Continuous Composite Beams

Static load tests are conducted for two outer-plated steel-concrete continuous composite beams. Performance of the tested beams, including the load-deflection curve，load-strain curve，load-moment curve, plastic-hinge region and the crack of concrete flange of specimens, is analyzed. The test results indicate that effective cooperation can be achieved by the shear connector between the concrete part and the outer-plated steel beam; the composite beams have good overall performance. The concrete filling inside the U-shaped steel beam enhances the global and local stability of the outer-plated steel beam. At the bearing capacity limit state, the plastic strain on sections of both the negative and positive maximum moment develops fully so that ideal plastic hinges are formed relatively. At the serviceability limit state, the deformation and the crack width of continuous composite beams can be controlled effectively.

PLASTIC DESIGN OF STEEL FRAMES WITH VIBRATION CONTROL SYSTEM BASED ON QUASI-LINEAR MOTION MECHANISM

This paper presents a plastic design method of steel frames with a vibration control system with U-shaped steel dampers based on a quasi-linear motion mechanism. Firstly, a plastic collapse load of the damper system is evaluated using the upper bound theorem where the U-shaped dampers are assumed to have three plastic hinges. The accuracy of the evaluation is examined by comparing the cyclic loading test results. Secondly, the plastic design is discussed for steel frames considering some collapse mechanisms. The shear stress in the beam web is also discussed for the beam attached with the U-shaped dampers. Finally, for the sake of introducing the proposed device into the practice, nonlinear finite element analyses are conducted for the three-story three-span steel moment frames with and without the damper system. Relationships between the story shear and story drift obtained from the static pushover analysis are examined. The Von-Mises stress distributions are also examined to reveal the influence of the proposed device on the steel moment frame.

Dynamic Tests on a Steel Frame Equipped with Hysteretic and Visco-Re-Centring Energy Dissipating Bracing Systems

An extensive program of dynamic experimental tests, named JetPacs (Joint Experimental Testing on Passive and semiActive Control Systems), has been carried out at the Structural Laboratory of the University of Basilicata considering a 1:1.5 scaled three-dimensional steel frame, derived from a 2-storey, 1-bay prototype building. The JetPacs Project was developed within the RELUIS 2005-08 project, founded by Italian Dept. of Civil Protection. This work refers to the experimental tests on the model equipped with two different EDB systems based on Hysteretic Dampers (HD) and visco-re-centering devices (SMA+VD). The devices were designed with the purpose of limiting the inter-storey drifts so that the frame yielding is surely prevented. The visco-re-centering device was obtained by coupling Viscous Dampers (VD), with re-centering device based on shape memory alloy (SMA) wires, while the Hysteretic Damper was constituted by low-carbon U-shaped steel plates. The main objective of this paper is to compare the seismic response of the structure with SMA+VD and HD EDB's in order to calibrate a new performance based design procedure for the evaluation of the mechanical characteristics of SMA+VD devices. In this paper, the experimental results of the shaking table tests, in terms of comparison of both design solutions which lead to a comparable level of protection for the framed structure, are shown. The results obtained by numerical nonlinear time history analysis (NTHA) of both design solutions are also showed and compared with experimental ones.

VIBRATION CONTROL SYSTEM WITH U-SHAPED STEEL DAMPERS BASED ON QUASI-LINEAR MOTION MECHANISM

This paper presents a new energy dissipation device for earthquake protection of structures. In the proposed device, the dissipation of seismic energy into structure is achieved through yielding of U-shaped steel dampers. The system is based on a quasi-linear motion mechanism and consequently bracing members are subjected to only tensile force. This can eliminate the brace-buckling problem. The stiffness and strength evaluations are performed for the steel frame with the proposed devices. Cyclic loading tests of the portal moment frames with the proposed device are conducted. Results and discussions are presented with emphasis on key features which affect energy dissipation capability. The lateral load and story drift angle relationships show that the proposed device provides stable and reasonably large energy dissipation capability. The effect of pre-tension applied to the bracing members is also examined through the brace axial strain and lateral load relationship.

Investigation on initial structural condition and analytical modeling of U-shaped steel girder bridge

Investigation on initial structural condition and analytical modeling of U-shaped steel girder bridge

EXPERIMENTAL EVALUATION OF CYCLIC DEFORMATION CAPACITY OF U-SHAPED STEEL DAMPERS FOR BASE-ISOLATED STRUCTURES

U-shaped steel dampers are used widely for energy dissipation in base-isolated structures. However, dynamic loading tests of full-scale U-shaped steel dampers had not been conducted yet. Therefore, effects of dynamic loadings on cyclic behavior and cyclic deformation capacity of the dampers had not been made clear. In this paper, dynamic loading tests of full-scale U-shaped steel dampers were carried out to verify these effects. The major findings obtained from the tests are: (1) cyclic deformation capacity of various-sized U-shaped steel dampers can be evaluated based on horizontal shear deformation γ calculated from the lateral displacement δ divided by the height of the dampers; (2) in-plane (0-degree) loading is the critical direction for U-shaped steel dampers in the range of horizontal shear deformation γ from 20 to 200% ; (3) the effect of dynamic loading on cyclic behavior and fatigue characteristics is minimal.

Integration of Thermal Treatment and Catalytic Transformation for Upgrading Biomass Pyrolysis Oil

The upgrading of bio-oil by catalytic transformation upon acidic catalysts is aimed at adapting its composition to that of conventional fuel, or at obtaining petrochemical raw materials, such as olefins and aromatics. A further alternative of growing interest for bio-oil upgrading is catalytic reforming for obtaining H2. The viability of any of these alternatives requires minimizing both the plugging problems that arise in the reactor when the bio-oil is fed and the rapid deactivation of the catalyst, which are associated with the thermal degradation of the lignocellulosic components. In this paper, the catalytic transformation of bio-oil (obtained by fast pyrolysis of vegetable biomass) in a fluidized bed reactor upon a Ni-HZSM-5 zeolite catalyst has been studied, and special attention has been paid to the design of the feed preheating zone. Operation in a single-unit (U-shaped steel tube) for the thermal treatment of the bio-oil (in the downward zone of the U-tube) and its catalytic transformation (in a fluidized bed located in the upward zone of the U-tube) has been compared with operation in a two-unit system, where both steps are carried out in separate units connected through a thermostated line (U-shaped tube for thermal treatment, followed by a fluidized bed reactor for catalytic transformation). It has been proven that a separate step of thermal treatment prior to the catalytic transformation notably improves the global process of bio-oil upgrading. Firstly, it contributes to minimizing coke deposition on the acidic catalyst, mainly the deposition of "thermal" coke (which is associated with the thermal degradation of the bio-oil components at high temperatures), leading to an important attenuation of catalyst deactivation. Secondly, the bio-oil components degraded in the thermal treatment can subsequently be subjected to another upgrading treatment (by steam activation or pyrolysis) in order to obtain a high quality char, which involves upgrading the entire bio-oil.