Development and validation of a metallic haunch seismic retrofit solution for existing under‐designed RC frame buildings

The feasibility and efficiency of a seismic retrofit solution for existing reinforced concrete frame systems, designed before the introduction of modern seismic‐oriented design codes in the mid 1970s, is conceptually presented and experimentally investigated. A diagonal metallic haunch system is introduced at the beam–column connections to protect the joint panel zone from extensive damage and brittle shear mechanisms, while inverting the hierarchy of strength within the beam–column subassemblies and forming a plastic hinge in the beam. A complete step‐by‐step design procedure is suggested for the proposed retrofit strategy to achieve the desired reversal of strength hierarchy. Analytical formulations of the internal force flow at the beam–column‐joint level are derived for the retrofitted joints. The study is particularly focused on exterior beam–column joints, since it is recognized that they are the most vulnerable, due to their lack of a reliable joint shear transfer mechanism. Results from an experimental program carried out to validate the concept and the design procedure are also presented. The program consisted of quasi‐static cyclic tests on four exterior, ? scaled, beam–column joint subassemblies, typical of pre‐1970 construction practice using plain round bars with end‐hooks, with limited joint transverse reinforcement and detailed without capacity design considerations. The first (control specimen) emulated the as‐built connection while the three others incorporated the proposed retrofitted configurations. The experimental results demonstrated the effectiveness of the proposed solution for upgrading non‐seismically designed RC frames and also confirmed the applicability of the proposed design procedure and of the analytical derivations. Copyright © 2006 John Wiley & Sons, Ltd.     

The interplay of sediment characteristics,depth, water temperature,and ocean currents shaping the biogeography of lancelets (Subphylum Cephalochordata) in the NW Pacific waters

Lancelets (or amphioxus) are often found within the soft bottom of shallow tropical and temperate seas. The present study is the first to provide a fine‐scale biogeography of five species of lancelets (Asymmetron lucayanum, Branchiostoma belcheri, Branchiostoma japonicum, Epigonichthys cultellus, and Epigonichthys maldivensis) in the NW Pacific and examine the effects of multiple environmental parameters. From multivariate analyses, the distribution and abundance patterns of lancelets were explained by a combination of factors comprising depth, temperature of the collecting month, mean temperature of the coldest month in the year, medium particle size and silt/clay ratio of the sediments. In addition, ocean currents also affect their distribution range. The major occurrence of A. lucayanum and E. maldivensis was associated with the warm Kuroshio current, but E. maldivensis exhibited higher tolerance to low salinity and low temperature, and preferred substrata of slightly larger grain size, a lower ratio of suspended sediments, and deeper water. The closely related B. belcheri and B. japonicum exhibited fine‐scale habitat differentiation, and B. japonicum was abundant along the southern coast of China, where the salinity is lower in winter because of the China Coastal Current and the substratum is composed of very coarse sand with suspended sediments. Branchiostoma belcheri occurred in low abundance and was only recorded in Northern Taiwan and the Taiwan Banks. Epigonichthys cultellus was found only at the Taiwan Banks, which had deep water, coarse sand, and a negligible amount of suspended sediments.     

Generation of Power by Microbial Fuel Cell with Ferricyanide in Biodegradation of Benzene

The power generation potential of a microbial fuel cell (MFC) during the process of benzene biodegradation with potassium ferricyanide (0–200 mM) as the terminal electron acceptor was evaluated. Experimental results demonstrate that benzene was used as the sole carbon source in generating electricity by a mixed culture. The power density increased from 0.0276 to 2.1 mW m^?2 as the concentration of potassium ferricyanide in the cathode chamber was increased from 0 to 200 mM. With a benzene concentration of 10.87 mg L^?1 and a potassium ferricyanide concentration of between 0 and 150 mM, complete degradation of benzene was achieved in 22–24.5 h. However, when the concentration of potassium ferricyanide was raised to 200 mM, the time required for complete benzene degradation was prolonged to 35 h. The results of this investigation can be used as a basis for future assessments of the power generation capacity of MFCs that are used to treat benzene‐contaminated wastewater.     

The effects of exclosures in restoring degraded semi-arid vegetation in communal grazing lands in northern Ethiopia

Rangeland degradation is a widespread problem throughout sub Saharan Africa and its restoration is a challenge for the management of many semi-arid areas. This study assessed the effectiveness of exclosures that have been protected from livestock from 5 to 15 years in restoring vegetation in northern Ethiopia. The species composition and diversity of herbaceous and woody plants were higher in the exclosures than in the grazed areas. Species richness responded positively to an increase in herbaceous productivity. The mean aboveground biomass measured inside the exclosures was more than twice that of the adjacent grazed areas and more biomass was produced from the young than the old exclosures. Stem height, canopy height, canopy cover, and browsing capacity of woody species were higher in the exclosures than in the grazed areas. Our study shows that degraded semi-arid vegetation is able to recover in a relatively short time when protected. Extended protection, beyond 8–15 years, reduces herbaceous species diversity and in one of the sites also the herbaceous biomass. Therefore, we suggest a slight shift in management where exclosures protected for longer periods may be moderately used by livestock.     

System identification on the seismic behavior of an isolated bridge

Seismic isolation devices and technology have been developed in the last two decades and the first seismic‐isolated bridge, Bai‐Ho Bridge, in Taiwan was completed in 1999. This bridge was equipped with a seismic monitoring system under the Taiwan Strong Motion Instrumentation Program (TSMIP). On 22 October 1999, a moderate earthquake took place and struck the bridge. The seismic monitoring sensors were normally triggered and produced an intact time history for the health monitoring of the bridge system. The data set provided valuable records about the seismic response of the isolation bridge structure. This paper uses this data to explore the vibration mechanism of Bai‐Ho Bridge. The analysis includes (1) the global dynamic behavior identification and (2) the local component mechanism of the bridge such as the LRB and boundary condition between the deck and the abutments. Both the EMD+HHT method and the non‐linear parametric model were used to identify the model of the bridge structure. Copyright © 2003 John Wiley & Sons, Ltd.     

Experimental evaluation of force analogy method (FAM) by element type

The force analogy method(FAM) is considered as one of the most time-saving and cost-efficient methods for analyzing frames. Through a set of assumptions and restoring forces, FAM analyzes nonlinear frames responses through Hooke's law. This study evaluates the effect of element type on FAM through numerical and experimental tests. The conventional Euler Bernoulli(EB) element is replaced by the Timoshenko(TS) beam-column element and the results are interpreted and compared with experimental findings. Three experimental tests were conducted for benchmarking and comparison purposes via 2 D aluminum frames. The results indicated that during the analysis, when the frame response is in the linear region, there is no difference between the element types in the response of the frames. When the frame entered the plastic region, the frames which were analyzed by the TS element revealed closer responses to the experimental outcomes. The gap between the results of the frame which was analyzed by EB and TS enlarged especially when the frame experienced a sharp or huge rotation of more than 0.2 rad. The final recorded deformations based on the TS element revealed an accuracy between 98.05% to 98.65%, while the EB element showed 14.66% to 45.14% for rotations of more than 0.2 rad at plastic hinge locations(PHLs).     

Design and experiment of a small boat track-keeping autopilot

A real time kinematic (RTK), GPS-based, track-keeping control of a small boat is discussed in this paper. The internal model control (IMC) method is adopted in the autopilot design and the controller is recast in the PID controller format that is characterized by its simple structure and relative ease of implementation. The track-keeping mission is achieved through a sequence of course-changing maneuvers and the reference heading is computed with the line-of-sight (LOS) guidance law. Path planning based on Bezier curves to achieve obstacle avoidance is investigated. First, computer simulations are carried out to find the feasible controller design parameter that achieves satisfactory simulation results. Then the feasible controller design parameter is applied in the small-boat-based experiments to demonstrate the practical use of the proposed autopilot design method.     

Application of subspace identification technique to long‐term seismic response monitoring of structures

This paper addresses the issue of structural system identification using earthquake‐induced structural response. The proposed methodology is based on the subspace identification algorithm to perform identification of structural dynamic characteristics using input–output seismic response data. Incorporated with subspace identification algorithm, a scheme to remove spurious modes is also used to identify real system poles. The efficiency of the proposed method is shown by the analysis of all measurement data from all measurement directly. The recorded seismic response data of three structures (one 7‐story RC building, one midisolation building, and one isolated bridge), under Taiwan Strong Motion Instrumentation Program, are analyzed during the past 15 years. The results present the variation of the identified fundamental modal frequencies and damping ratios from all the recorded seismic events that these three structures had encountered during their service life. Seismic assessment of the structures from the identified system dynamic characteristics during the period of their service is discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

An integral eigenvalue approach to three-dimensional field problems--A low-frequency variation of SEM

The three-dimensional (3-D) eddy-current transient field problem is formulated first using theu-vmethod. This method breaks the vector Helmholtz equation into two scalar Helmholtz equations. Null-field integral equations and the appropriate boundary conditions germane to the problem are used to set up an identification matrix which is independent of null-field point locations. Embedded in the identification matrix are the unknown eigenvalues of the problem representing its impulse response in time. These eigenvalues are found by equating the determinant of the identification matrix to zero. The eigenvalues, which can be equated with temporal response, are found to be intimately linked to the initial forcing function which triggers the transient in question. When this initial forcing function is Fourier decomposed into its respective spatial harmonics, it is possible to associate with each Fourier component a unique eigenvalue by this technique. The true transient solution comes through a convolution of the impulse response so obtained with the particular imposed external field governing the problem at hand. The technique is applied to the FELIX medium cylinder (a conducting cylinder placed in a collapsing external field) and compared to data. A pseudoanalytic confirmation of the eigenvalues so obtained is formulated to validate the procedure. The technique proposed is applied in the low-frequency regime where the near-field effects must be considered. Application of the technique to a high frequency follows directly if the Coulomb gauge is adopted to represent the vector potential.