Behaviour of uni‐axially loaded concrete‐filled‐steel‐tube columns confined by external rings

Concrete‐filled‐steel‐tube (CFST) columns have been widely adopted for column construction of tall buildings due to its superior strength and ductility performance contributed by the composite action. However, this beneficial composite action cannot be fully developed at early elastic stage as steel dilates more than concrete and thereby causing imperfect interface bonding. Hence, it reduces the elastic strength and stiffness of the CFST columns. To resolve the problem, external confinement in the form of steel rings is proposed in this study to restrict the lateral dilation of concrete and steel at initial elastic stage. In this paper, CFST columns of various dimensions cast with normal‐strength or high‐strength concrete and installed with external steel rings were tested under uni‐axial compression. From the results, it was evident that (a) the external steel rings could restrict the lateral dilation of CFST columns and improve the interface bonding condition and (b) externally confined CFST columns had uni‐axial strength and stiffness larger than those of unconfined CFST columns. With the experimental results, an analytical model taking into account the confining effects of steel tube and rings has been developed to predict the uni‐axial strength of ring‐confined CFST columns. Copyright © 2012 John Wiley & Sons, Ltd.     

Berechnung von Holz‐Beton‐Verbunddecken

Evaluation of Timber Concrete Composite Slabs If timber and concrete acts together in a cross section, the carrying and deformation behaviour of this new composite section is affected by many influences e.g. geometry, material properties, connecting device, long‐term behaviour, etc. The advantages of this building method and an optimization of the cross sections only can be achieved, if these influences are known and can be taken into account in the structural design. For the proof of the short term behaviour different procedures, e. g. [1], are available. Regarding the long‐term behaviour of the timber concrete composite floors it becomes obvious that the rheological behaviour of timber concrete composite structures is not considered sufficiently by the design method in [1].     

Biodegradation of chlorpyrifos and 3, 5, 6‐trichloro‐2‐pyridinol by a novel rhizobial strain Mesorhizobium sp. HN3

A chlorpyrifos (CP) and 3,5,6‐trichloro‐2‐pyridinol (TCP) degrading bacterial strain, Mesorhizobium sp. HN3, was isolated and characterized. Mesorhizobium sp. HN3 degraded CP efficiently up to 400 mg/L initial concentration at wide range of temperatures (30–40°C) and pH (6.0–8.0). However, optimal degradation of CP was achieved at 37°C and neutral pH (7.0) at an initial inoculum density 2 × 10⁷ colony forming unit/mL of culture medium. Kinetic parameters for CP degradation by Mesorhizobium sp. HN3 were estimated at different initial concentrations. Cultures exhibited significant variation (P ≤ 0.05) in the specific growth rate (μ), cell mass formation rate (Q_X) and the substrate uptake rate (Q_S) during degradation of CP. The values of kinetic parameters increased up to 100 mg/L CP and decreased at higher concentration. Investigation of degradation metabolites indicated that CP is converted to diethylthiophosphate and TCP that leads to the formation of 3,5,6‐trichloro‐2‐methoxypyridine.     

Experimental study of across‐wind aerodynamic damping of super high‐rise buildings with aerodynamically modified square cross‐sections

Across‐wind aerodynamic damping ratios are determined from the wind‐induced acceleration responses of 10 aeroelastic models of square super high‐rise buildings in an urban flow condition (exposure category C in the Chinese code) using the random decrement technique. Moreover, the influences of amplitude‐dependent structural damping ratio on the estimation of aerodynamic damping ratio are discussed. The validity of estimated damping is examined through a comparison with previous research achievements. On the basis of the estimated results, the characteristics of the across‐wind aerodynamic damping ratios of modified square high‐rise buildings are studied. The effects of aerodynamically modified cross‐sections, such as chamfered, slotted and tapered cross‐section, on the across‐wind aerodynamic damping ratio are investigated. The results indicate that modifications of cross‐sections are not always effective in suppressing the aeroelastic effects of super high‐rise buildings. Low corner‐cut ratios (chamfer ratios from 5% to 20% and slot ratios from 5% to 10%) and low taper ratio (1%) significantly decrease the magnitudes of absolute aerodynamic damping ratios. However, large modifications of cross‐sections (slot ratio of 20% and taper ratios from 3% to 5%) increase wind‐induced responses by changing the aerodynamic damping ratios. According to the database, empirical aerodynamic damping function parameters are fitted for high‐rise buildings with aerodynamically modified square cross‐sections. Copyright © 2013 John Wiley & Sons, Ltd.     

Visko‐elastisches Verhalten von Holz‐Klebstoff‐Verbindungen unter zyklischer Zug‐Druck‐Belastung

Visco‐elastic behavior of bonded wood under cyclic tensile and compression loading In the present contribution, a test method is used to simulate the static, cyclic loading of adhesive joints due to swelling and shrinking of the wood and to demonstrate the plastic deformation in the low load range. For tensile shear specimens prepared from beech wood and bonded with three different adhesives (MUF, PRF, PUR), the elastic behavior under cyclic tensile and compression loading was investigated and the loss and storage of energy was determined. All tested adhesives showed viscose parts even at a very low load level of 3 MPa. At a load level of 7 MPa, the PRF joints revealed a more elastic behavior than the other. The increased loss energy determined for the PUR bonding indicates a softening of the adhesive joint.     

The impacts of ‘run‐of‐river’ hydropower on the physical and ecological condition of rivers

This paper synthesises published literature on run‐of‐river hydropower, highlighting its potential to affect both the physical and ecological conditions of river systems. The paper considers the limited number of direct studies and reviews a wider literature on the two principal impacts of such schemes on river systems: the introduction or maintenance of in‐channel barriers and water abstraction/flow regime alteration. We outline how river systems are likely to be impacted by such schemes and identify the key issues arising from their continued development. Potential mitigation approaches are highlighted and the areas of future research required to adequately address current knowledge gaps are identified.