Search

Objectives To assess the accuracy, repeatability, and reproducibility of T1 and T2 relaxation time measurements by three-dimensional magnetic resonance fingerprinting (3D MRF) using various dictionary resolutions. Methods The ISMRM/NIST phantom was scanned daily for 10 days in two 3 T MR scanners using a 3D MRF sequence reconstructed using four dictionaries with varying step sizes and one dictionary with wider ranges. Thirty-nine healthy volunteers were enrolled: 20 subjects underwent whole-brain MRF scans in both scanners and the rest in one scanner. ROI/VOI analyses were performed on phantom and brain MRF maps. Accuracy, repeatability, and reproducibility metrics were calculated. Results In the phantom study, all dictionaries showed high T1 linearity to the reference values (R2 > 0.99), repeatability (CV < 3%), and reproducibility (CV < 3%) with lower linearity (R2 > 0.98), repeatability (CV < 6%), and reproducibility (CV ≤ 4%) for T2 measurement. The volunteer study demonstrated high T1 reproducibility of within-subject CV (wCV) < 4% by all dictionaries with the same ranges, both in the brain parenchyma and CSF. Yet, reproducibility was moderate for T2 measurement (wCV < 8%). In CSF measurement, dictionaries with a smaller range showed a seemingly better reproducibility (T1, wCV 3%; T2, wCV 8%) than the much wider range dictionary (T1, wCV 5%; T2, wCV 13%). Truncated CSF relaxometry values were evident in smaller range dictionaries. Conclusions The accuracy, repeatability, and reproducibility of 3D MRF across various dictionary resolutions were high for T1 and moderate for T2 measurements. A lower-resolution dictionary with a well-defined range may be adequate, thus significantly reducing the computational load. Key Points • A lower-resolution dictionary with a well-defined range may be sufficient for 3D MRF reconstruction. • CSF relaxation times might be underestimated due to truncation by the upper dictionary range. • Dictionary with a higher upper range might be advisable, especially for CSF evaluation and elderly subjects whose perivascular spaces are more prominent.

Hollow section braces are often adopted in steel frame structures because of their superior performance. To connect tubular members with framing elements, field-bolted connections of the slotted-in single splice plate and gusset plate are majorly used because of their ease of construction. However, the eccentricity between the splice and gusset plate axes reduces the compressive strength of the brace and induces local connection failures under seismic excitations. To improve the compressive strength, this paper proposes a new connection configuration for circular hollow section braces in which cruciform rib-stiffened splice plates are eccentrically installed such that the gusset plate axis coincides with the brace axis. The concept of the proposed connection was first described with theoretical considerations. To demonstrate the effectiveness of the proposed connections, compressive loading tests and subsequent cyclic loading tests were conducted for four test specimens. Furthermore, finite element analyses with long-brace models were performed to demonstrate the good performance of the proposed connection for a wide range of slenderness ratios.

Hemorrhage inside the mammillary bodies (MMBs) is known to be one of the findings of Wernicke encephalopathy. Brain MRI of two patients with Wernicke-Korsakoff syndrome (WKS) demonstrated high susceptibility values representing hemosiderin deposition in MMBs by using quantitative susceptibility mapping (QSM). QSM provided additional information of susceptibility values to susceptibility-weighted imaging in diagnosis of WKS.

A cell-killing ability of natural killer (NK) cells has been evaluated by the leakage of marker molecules from target cells. Lactate dehydrogenase (LDH) and calcein are two major non-radioisotope markers used for the killing assay. The spontaneous death of NK cells during the killing-assay of cells is a major issue in the assay because it provides background signals to increase errors. In this study, the effect of the spontaneous death of NK cells on the killing assays based on LDH and the calcein method was comparatively evaluated. We found that the calcein method is much less sensitive to the spontaneous death of NK cells to enable an accurate evaluation of the cell killing.

Synthetic small molecules that redirect endogenous antibodies to target cells are promising drug candidates because they overcome the potential shortcomings of therapeutic antibodies, such as immunogenicity. Previously, we reported a novel class of bispecific molecules targeting the antibody Fc region and folate receptor, named Fc-binding antibody-recruiting molecules (Fc-ARMs). Fc-ARMs can theoretically recruit most endogenous antibodies, inducing cancer cell elimination via antibody-dependent cell-mediated cytotoxicity (ADCC). Here, we describe new Fc-ARMs that target prostate cancer (Fc-ARM-Ps). Fc-ARM-Ps recruited antibodies to cancer cells expressing prostate membrane-specific antigen but did so with lower efficiency compared with Fc-ARMs targeting folate receptor. Upon recruitment by Fc-ARM-P, defucosylated antibodies efficiently activated natural killer cells and induced ADCC, whereas antibodies with intact N-glycans did not. The results suggest that the affinity between recruited antibodies and CD16a, a type of Fc receptor expressed on immune cells, could be a key factor controlling immune activation in the Fc-ARM strategy.

Redirecting endogenous antibodies in the bloodstream to tumor cells using synthetic molecules is a promising approach to trigger anti-tumor immune responses. However, current molecular designs only enable the use of a small fraction of endogenous antibodies, limiting the therapeutic potential. Here, we report Fc-binding antibody-recruiting molecules (Fc-ARMs) as the first example addressing this issue. Fc-ARMs are composed of an Fc-binding peptide and a targeting ligand, enabling the exploitation of endogenous antibodies through constant affinity to the Fc region of antibodies, whose sequence is conserved in contrast to the Fab region. We show that Fc-ARM targeting folate receptor-α (FR-α) redirects a clinically used antibody mixture to FR-α+ cancer cells, resulting in cancer cell lysis by natural killer cells in vitro. Fc-ARMs successfully interacted with antibodies in vivo and accumulated in tumors. Furthermore, Fc-ARMs recruited antibodies to suppress tumor growth in a mouse model. Thus, Fc-ARMs have the potential to be a novel class of cancer immunotherapeutic agents., Fc-binding antibody-recruiting molecules provide robust and sufficient opportunities to employ endogenous antibodies for anti-tumor immune responses.

Case Presentation A 78-year-old man with asthma and COPD presented with shortness of breath, cough, and severe malaise for 4 days. Upon arrival, the patient was conscious and body temperature was 37.5°C. Arterial oxygen saturation (Spo2) was 80% on room air. Laboratory data demonstrated a WBC count of 17,400/μL (89.5% neutrophils) and C-reactive protein of 5.00 mg/dL. CT scan of chest revealed scattered ground-glass in the upper right lobe and thickening of the bronchial wall. Based on these findings, acute bronchopneumonia was diagnosed and antibacterial therapy was started. The day after admission, the patient's general condition and shortness of breath had gradually improved. We treated and observed him carefully for 10 days in the hospital on antibacterial therapy because of his underlying comorbidities (asthma and COPD) and his ongoing hypoxemia. Three days after discharge, the patient re-presented with shortness of breath, hypoxemia, and loss of appetite. The patient was hospitalized for a second time.

The purpose of this study is to evaluate whether thin-slice high-resolution 2D fat-suppressed proton density-weighted image of the knee joint using denoising approach with deep learning-based reconstruction (dDLR) with MPR is more useful than 3D FS-PD multi planar voxel image. Twelve patients who underwent MRI of the knee at 3T and 13 knees were enrolled. Denoising effect was quantitatively evaluated by comparing the coefficient of variation (CV) before and after dDLR. For the qualitative assessment, two radiologists evaluated image quality, artifacts, anatomical structures, and abnormal findings using a 5-point Likert scale between 2D and 3D. All of them were statistically analyzed. Gwet’s agreement coefficients were also calculated. For the scores of abnormal findings, we calculated the percentages of the cases with agreement with high confidence. The CV after dDLR was significantly lower than the one before dDLR (p p p p

In earthquake-prone countries such as Japan, effects of earthquakes are one of the major design objectives in buildings and infrastructures. Recent advances in earthquake engineering have improved the safety and reliability of buildings and infrastructures. Better understanding of geomorphology of earthquakes also enables us to better predict and estimate propagation of such natural hazard. For example, the Earthquake Early Warning (EEW) system in Japan provides advanced warnings using the different arrival times of P and S waves. On the other hand, techniques and methods in passive, semi-active and active vibration control have flourished. Base-isolation is a proven technique which enhances earthquake resilience of buildings and bridges. In general, this technique involves decoupling a superstructure from its foundation and lengthens its natural period of vibration. This technique is mature and commercialization has taken place worldwide. However, wind-resistance of base-isolated structures is generally a concern as the lateral stiffness of a base-isolated structure is low and serviceability wind effects may induce unacceptable lateral movement and/or vibration of the structure. This paper presents a new concept which the base-isolation system is activated by EEW system through a mechatronic system. In other times the structure is not base-isolated and provides strong lateral resistance against wind loads. As a backup design, the proposed system also equips with its own network of accelerometers which can trigger base isolation system independent from EEW system. The smart mechatronic base isolation system is fully automated, and resets itself after each ground motion. The paper describes the conceptual framework of proposed system and presents laboratory-scaled proof-of-concept experiments. Four historical earthquake time histories were used as ground excitations. Structural responses are compared between the two triggering mechanisms and results are discussed. Finally, the concept of Internet of Things (IoT) which make use of EEW is discussed, allowing connectivity between a single control unit and a network of infrastructures to achieve economy of scale.

We developed conjugates between monoclonal antibody (mAb) and folic acid (FA) by using a tryptophan (Trp)-selective reaction, which yields relatively homogenous products compared to conventional methods. The obtained mAb–FA conjugates showed significant cellular cytotoxicity toward folate receptor-expressing cancer cells, demonstrating that the conjugates retained the Fc region's original function.

Although monoclonal antibodies (mAbs) have revolutionized cancer treatment, their accumulation in solid tumors is limited and requires improvement to enhance therapeutic efficacy. Here we developed a strategy to modify mAb with a donor of nitric oxide (NO) because NO functions to vasodilate as well as to enhance the permeability of vascular endothelium, which will contribute to enhancing the tumor accumulation of mAb. We selected S-nitrosothiol as a NO donor and established the procedure to modify S-nitrosothiol group on mAb under ambient conditions. The modified mAb (Ab-SNO) thus obtained released NO in a preferable speed and maintained its original properties such as binding affinity to a target antigen and efficacy to induce antibody-dependent cellular cytotoxicity. We demonstrated that Ab-SNO enhanced the tumor accumulation of co-administered proteins such as antibody and serum albumin.

This paper presents an innovative application of buckling-restrained knee braces (BRKBs) for spreading plasticity at the beam ends of rigid moment connections. A slender knee brace configuration consisting of a steel core bar and tube buckling restrainer is proposed. The benefit of adopting a steel bar is that it enables the downsizing of the knee brace connections between braces and beam flanges. The advantages of tube buckling restrainers include relatively simple implementation for ease of construction and reduced weight compared to mortar-filled buckling restrainers. Displacement-controlled cyclic loading tests were conducted to examine the spreading of the plasticity behaviors of rigid moment connections using the proposed BRKBs. Structural performance metrics such as hysteretic behavior, strength capacity under a given loading, and strain distributions at beam flanges were measured and analyzed in detail. Additionally, the optimal parameters for the proposed BRKBs were determined through an extensive numerical study. The results revealed that the optimal parameters of the proposed slender BRKBs significantly improve load-bearing capacity and reduce stress concentrations in the vicinity of the rigid beam-to-column connections. As a result, the plastic region on the beam is spread both inside and outside the knee brace area. Based on the research conducted thus far, it was determined that the proposed BRKB is a viable option for spreading plasticity along beams in rigid beam-to-column connections.

Steel hollow section members are often applied as bracing in steel structures. Field-bolted connections of the slotted-in single splice plate and the gusset plate are popular because of their ease of construction. However, eccentricity between the splice and gusset plate axes reduces the compressive strength of the brace. This study proposes compressive strength improvement of rectangular hollow section braces using eccentrically installed splice plates such that the gusset plate axis coincides with the brace axis. To demonstrate the efficacy of the proposed concept, four compressive loading test results are examined in this study. Test results reveal the influences of splice plate eccentric installation on the brace compressive strength, the out-of-plane displacement, and the strain distribution. The proposed concept is effective for the brace with stiffened splice plates for inducing overall buckling with plastic hinges in the gusset plates. Variation of compressive strength is finally discussed based on the discrepancy between the brace axis and the axis of the plates in which the plastic hinges form at the overall buckling mode ends.

Small molecules emulating the effector functions of antibodies have potential clinical benefits because of their low immunogenicity. Antibody-recruiting molecules (ARMs) are bispecific molecules designed to redirect endogenous antibodies to targets. However, endogenous antibodies show intra/inter-patient differences regarding their concentrations and affinities, limiting the potential of ARMs. We sought to address this issue using a Fc-binding peptide instead of an antigen for antibody redirection. Fc-binding ARM (Fc-ARM) targeting folate receptor-α (FR-α) expressed on cancer cells, formed a ternary complex of Fc-ARM, FR-α, and antibody on cancer cells. The ability of this ternary complex to activate natural killer cells was positively correlated with its Fc affinity, and did not require the Fab region. Fc-ARM hitchhiked on pooled human IgG to enhance its blood retention, and suppressed tumor growth in a mouse xenograft model of human cancer. Thus, Fc-ARM has the potential to be employed as a less immunogenic alternative to therapeutic antibodies.

This paper presents an experimental investigation on buckling-restrained steel bar dampers used at the lower sides of a spine frame. The dampers are mainly composed of round steel bar cores restrained by round steel tubes, and additional components called supporters that provide the lateral support against flexural buckling of the round steel tube. One characteristic of the proposed damper is that its buckling length can be controlled by using supporters. Cyclic loading tests were conducted on 10 scaled specimens to assess the functionality and energy dissipation performance of the proposed damper. The test specimens differed mainly with regard to the number of supporters, number of contraction allowance zones, type of connection to the base beam, and damper length. The performance of the damper was extensively discussed base on the cyclic behavior of the different specimen configurations and the mechanical performance of the different damper components. Furthermore, the supporter connection was assessed via collapse mechanism analysis to determine strength requirements. The test results revealed the optimal configurations, the functionality, and the plastic deformation capacity of the proposed system.

This paper presents results of experimental and numerical investigations of a seesaw energy dissipation system (SEDS) using fluid viscous dampers (FVDs). To confirm the characteristics of the FVDs used in the tests, harmonic dynamic loading tests were conducted in advance of the free vibration tests and the shaking table tests. Shaking table tests were conducted to demonstrate the damping capacity of the SEDS under random excitations such as seismic waves, and the results showed SEDSs have sufficient damping capacity for reducing the seismic response of frames. Free vibration tests were conducted to confirm the reliability of simplified analysis. Time history response analyses were also conducted and the results are in close agreement with shaking table test results.

This paper presents an investigation into the cyclic behavior of a passive vibration control system in which steel slit dampers are applied to a seesaw energy dissipation system. The fundamental concept of the seesaw system is the quasi-linear motion mechanism, which enables the bracing members to remain in tension during vibration. The lateral stiffness and strength formulae of the frame with this system are derived first. Six cyclic loading tests were conducted to reveal that the proposed system has a stable hysteretic property and a large energy dissipation capacity. For all specimens, the slit dampers yielded at early stages of the tests around a story rotation angle of 0.001 rad. This property is preferred for energy dissipation properties to reduce story drift in building structures under seismic loads. The important seesaw system characteristic of the bracing members remaining tensile was also observed. The tri-linear hysteretic model is introduced to model the cyclic behavior of the proposed damping system. A comparison of the hysteretic loops and the energy dissipation amount between the model and test results reveals the adaptability of the tri-linear model to the hysteretic behavior of the proposed system. The validity of the stiffness and strength prediction is also shown from the test results.

Recent deployments of Earthquake Early Warning (EEW) system in Japan and some other earthquake-prone regions provide the vital warning signals prior to the arrival of destructive ground motions. The EEW system uses the different traveling speed of seismic P- and S-waves to achieve the goal of earthquake warning. This technology is primarily used to produce warning signals to alert the public to avoid potential risks, such as to evacuate from buildings. It is also used to mitigate other risks such as reducing train speed of Shinkansen trains. The present study suggests a new seismic-risk mitigation technique by connecting a base isolation system with the EEW. Base isolation is a mature technology which decouples structure from its base and lengthens its natural period of vibration. However, existing base isolation devices must possess certain lateral resistance to withstand service lateral forces such as wind, and such stiffness hinders the effectiveness of vibration isolation. In addition, supplementary damping devices are sometimes added to control excessive displacements in isolation level. This paper proposes a smart system which changes the property of a base isolation system upon EEW signal. In normal times when earthquake risk is not present, the base isolation system is locked by shear keys. When an earthquake is signalled by the EEW system, a mechanical system releases the base isolation system. When the earthquake ceases, the system resets and base isolation is locked again. On-board vibration sensors are added to activate the system in case of EEW fails to detect incoming waves. A crucial benefit of the system is that supplementary damper is no longer required to control excessive isolator displacements, and elastic stiffness of base isolation is no longer required to re-enter the base isolation system. The result is that it maximizes the vibration isolation effectiveness. A conceptual framework of proposed system is described and demonstrated by laboratory-scaled experiments. A 6-storey test frame is excited on a shake table subjected to historical earthquakes. Results indicates that the proposed system is effective in reducing earthquake responses on the building. It is an IoT-enabled earthquake-risk mitigation system.

In the design of steel building frames, comprehensive consideration is required to determine beam-to-column connections because their characteristics largely influence the performance of the whole frame. Recent studies by some researchers have investigated the application of dampers to bolted beam-to-column connections, where the dampers are often positioned between the bottom beam flange and the column. This study investigates the application of buckling-restrained round steel bar dampers to bolted beam-to-column connections. The configuration of the proposed connection and its design method are first described. Then, cyclic loading tests of six specimens are presented to clarify the structural performance of the proposed connection. The hysteretic behavior is largely influenced by the configuration of the damper, such as bar length, shank diameter, and damper position. Furthermore, finite element analyses of the damper and connection models are demonstrated for the detailed examination of their plastic behavior characteristics such as the spiral buckling deformation of the bar. The ratio of the beam shear force acting on the dampers is discussed based on the analysis results of the connection model.

This paper presents a new stiffening method for bolted end-plate beam–column connections in which steel member assemblies of steel angles and plates are used as stiffeners. An important benefit of this method is that it can eliminate transverse stiffeners and doubler plates, thereby enabling use of the space between the column-flanges for architectural demands such as ducting. The local tensile strength was first evaluated based on the yield line theory. To examine failure behavior in the tension part of end-plate connections, three local tensile loading tests were conducted for the T-stub connection models. Then the local compressive strength was also evaluated by consideration of previous studies. Subsequently, to ascertain the stiffening method efficiency, one cyclic loading test was conducted for the real-size beam-to-column bolted end-plate connection. Accuracy of the strength formulae was demonstrated by comparing the predictions and the loading test results. The proposed method using the steel member assemblies was revealed to be effective to stiffen bolted end-plate connections.

SUMMARY Seesaw energy dissipation system (SEDS), a vibration control system used to provide enhanced seismic protection, has been proposed and investigated numerically. Because of its complicated arrangement, verification experiments are necessary to demonstrate the SEDS damping capacity. This paper presents the results of experimental investigation of the SEDS using fluid viscous dampers. Free vibration tests are conducted to demonstrate the SEDS damping capacity. Results of the free vibration test show that the SEDS has sufficient damping capacity for reduction of the seismic response of the frames. Parametric experimental investigations of the SEDS were conducted, the results of which demonstrate the effects of the system parameter on the damping capacity. Copyright © 2014 John Wiley & Sons, Ltd.

This study proposes a buckling-restrained brace (BRB) which is composed of round steel bar cores restrained by inner round steel tubes and an outer square steel tube. One advantage of using the round steel bar cores against the steel plates and tubes is that the bar-ends can be connected to the structural members using screw-joints. The cyclic loading tests were conducted on two test specimens to examine the hysteretic performance of the proposed BRBs. Test results revealed the applicability, restraining capacity, and end-coupler performance of the proposed brace. With an increase in the number of contraction allowance zones, efficacy and performance of the brace became more satisfactory. Furthermore, a theoretical method for designing the proposed BRB in a simplified and optimal way is discussed. For the creation of the design guideline, the braces were analyzed comparatively over a wide range of sections, lengths, and different load conditions, which are most suitable for low to mid-rise buildings. It was found that the design is governed by the heaviest components of the brace, and that the pin connection to the frame was a key component for optimal design.

This paper presents a new vibration control system based on a seesaw mechanism with fluid viscous dampers. The proposed vibration control system comprises three parts: brace, seesaw, and fluid viscous dampers (FVDs). In this system, only tensile force appears in bracing members. Consequently, the brace buckling problem is negligible. This benefit is useful for steel rods for bracing members. By introducing pre-tension in rods, long steel rods are applicable for bracing between the seesaw members and the moment frame connections over several stories. The relation between the frame displacement and the damper deformation is first derived in consideration of the rod deformation. Simplified analysis models of seesaw energy dissipation system are developed based on this relation. Subsequently, seismic response analyses are conducted for three-story and six-story steel moment frames with and without dampers. In addition to the proposed system, a diagonal-brace-FVD system and a chevron-brace-FVD system are analyzed for comparison. Parameter analyses of rod stiffness and damping coefficient are conducted for the six-story frame. The maximum story drift angle and response of the top floor displacement are discussed. Results show a high capability of seesaw energy dissipation system for improving the structural response.

Background Nonvitamin K antagonist oral anticoagulants may cause interstitial lung disease (ILD) similar to that seen for other cardiovascular drugs. The aim of this study was to determine trends and medical conditions associated with ILD in patients taking apixaban. Methods A single-center observational survey conducted between February 2013 and May 2015 examined patients who developed ILD after initiation of apixaban administration. Results Chest computed tomography showed that 4 (~.45%) out of approximately 870 apixaban users developed ILD. All patients were elderly Japanese men with decreased creatinine clearance who had nonvalvular atrial fibrillation. Three of the four were confirmed smokers, whereas three had a history of lung disease. Dyspnea occurred during the initial week after starting apixaban administration in 3 patients and at 90 days in 1 patient. All patients underwent methylprednisolone pulse therapy, with three requiring mechanical ventilation. Although 2 patients recovered, the other two died of respiratory failure. Conclusions Development of ILD during anticoagulation with apixaban is not rare. When apixaban is administered in elderly high-risk patients, subjects need to be carefully monitored for respiratory symptoms. As drug-induced ILD is often reported in Japan, further studies that clarify if these types of cases are common in countries other than Japan will also need to be undertaken.

SUMMARY Vibration control systems are being used increasingly worldwide to provide enhanced seismic protection for new and retrofitted buildings. This paper presents a new vibration control system on the basis of a seesaw mechanism with viscoelastic dampers. The proposed vibration control system comprises three parts: brace, seesaw member, and viscoelastic dampers. In this system, only tensile force appears in bracing members. Consequently, the brace buckling problem is negligible, which enables the use of steel rods for bracing members. By introducing pre-tension in rods, long steel rods are applicable as bracing between the seesaw members and the moment frame connections over some stories. Seesaw mechanisms can magnify the damper deformation according to the damper system configuration. In this paper, first, the magnification factor, that is, the ratio of the damper deformation to the story drift, is delivered, which includes the rod deformation. Results of a case study demonstrate that the magnification factor of the proposed system is greater than unity for some cases. Seismic response analysis is conducted for steel moment frames with the proposed vibration control system. Energy dissipation characteristics are examined using the time-history response results of energy. The maximum story drift angle distributions and time-history response results of displacement show that the proposed system can reduce the seismic response of the frames effectively. Copyright © 2012 John Wiley & Sons, Ltd.

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.

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.

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.

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.

Optimal shapes are found for a reduced beam section of a cantilever H-beam subjected to forced cyclic displacement at the free end. The beam is discretized to finite elements, and a commercial software package called ABAQUS is used for elastoplastic analysis. The numerical results are first compared with experimental results to verify the accuracy. The objective function to be maximized is the dissipated energy throughout the loading history. The constraint is given for the maximum equivalent plastic strain at the welded section. Global optimal solutions are searched for by a heuristic approach called simulated annealing, which is successfully combined with ABAQUS. It is shown that the energy dissipation capacity is significantly improved by optimizing the flange shape.

We study the influence of the P-Δ effect on the dynamic response of 20 story moment-resisting steel frames under extreme earthquake ground motions. In this paper, we perform nonlinear time-history analyses of 3 frame models having different design base shear. The major findings include; (a) If the design base shear was close to the lower bound of existing buildings, deformation in lower stories accumulated in one direction under a synthetic long-period earthquake ground motion. This led to significant residual story drift. (b) The deformation accumulation was suppressed by increasing the post-yield stiffness. (c) The deformation accumulation occurred even if the columns are all elastic except the base of the 1st story.

Eccentric beam-to-square tubular column connections in steel building frames have been investigated by many researchers. For eccentric beam-to-wide flange column connections, fewer efforts have been made in the past. In a recent study by the authors, local strength of the eccentric beam flange-to-wide flange column connections was examined. This paper presents strength evaluation of panel zones in the eccentric beam-to-wide flange column connections. A torsional moment induced by an eccentric beam-flange force is considered in the derivation of the panel zone strength formula. Cyclic loading tests of T-shaped connection models have been conducted to examine the hysteretic characteristics. The test results show that the eccentric connections have adequate ductility and hysteretic energy dissipation capacity. The strength formula of the panel zones has a reasonable accuracy. Elastic-plastic finite element analyses performed for the cruciform connection models demonstrate influence of the stiffener sizes on the panel zone strength.

Extensive researches have been conducted on the application of eccentric beam-to-column connections in the steel frames composed of square tubular columns. For eccentric beam-to-wide-flange column connections, fewer efforts have been made in the past. This paper presents the local yield strength of the eccentric beam-to-wide-flange column connections. For the connection stiffening, both transverse stiffeners and vertical stiffeners are employed. By applying the yield line theory, strength formulae of the beam flange-to-column connections are derived for five different types of collapse mechanisms. Six loading tests are performed for the local connection models to examine the elastic-plastic behavior of the connections with eccentricity. The measured strain distributions and the residual flange deformations confirm the validity of the collapse mechanism including beam-flange rotation.

This paper presents a new seismic resisting system for moment-resisting frames using wire-rope bracing. The braces used in this system can increase the lateral strength without reducing ductility of the moment frame. By delaying the bracing action, energy dissipation capacity is kept large and further the story-displacement can be reduced within a specified amplitude range. Comparison of the loading test results for the portal steel moment frames with and without the braces shows the fundamental characteristics of the proposed bracing system. Numerical response analyses are performed for the three-story moment-resisting frames with and without the bracing members. The analysis results reveal that the proposed wire-rope bracing system has a re-centering effect on the vibration center and a deformation dispersion effect along the height of the frame that can suppress deformation concentration into local stories.

The purpose of this paper is to show that the performance of a structural component is drastically improved utilizing shape optimization considering inelastic responses. Optimal flange shapes are found as an example for an H-beam to show that the energy dissipation capacity is significantly improved by shape optimization. The forced displacement is given at the free end of the cantilever beam so that the average deformation angle reaches the specified value. The constraint is given for the maximum equivalent plastic strain at the welded section. Global optimal solutions are searched by a heuristic approach called simulated annealing, which is successfully combined with a commercial finite-element analysis code ABAQUS for elastoplastic analysis. It is shown in the examples that the maximum plastic strains near the welded section are reduced and the plastic deformation is widely distributed around the reduced section of the optimal solution; thus, allowing large energy dissipation under small maximum plastic strain. The results show the advantage of the optimal shape over the conventional circular cut.