•Establishes a framework to identify bridge frequencies from a moving test vehicle.•Gives theoretical support to eliminate the negative effect of road roughness.•Adopts a dimensionless description to ...cope with the time-varying nature of VBI.•The method is verified via numerical experiments with both SDOF and MDOF vehicles.•Allows identification considering practical vehicle speeds and poor road surface.
This study establishes a short-time stochastic subspace identification (ST-SSI) framework to estimate bridge frequencies by processing the dynamic response of a traversing vehicle. The formulation uses a dimensionless description of the response that simplifies the vehicle-bridge interaction (VBI) problem and brings forward the minimum number of parameters required for the identification. With the aid of the dimensionless parameters the analysis manages to successfully apply ST-SSI despite the time-varying nature of the VBI system. Further, the proposed approach eliminates the adverse effect of the road surface roughness using a transformed residual vehicle response obtained from two traverses of a vehicle at different speeds over the bridge. The study verifies the proposed ST-SSI approach numerically: it first performs the dynamic VBI simulations to obtain the response of the vehicle, and then applies the proposed ST-SSI method, assuming the dynamic characteristics of the vehicle are available. The numerical experiments concern both a sprung mass model and a more realistic multi-degree-of-freedom (MDOF) vehicle model traversing a simply supported bridge. The results show that the proposed approach succeeds in identifying the first two bridge frequencies for test-vehicle speeds much higher (e.g., 10 m/s = 36 km/h and 20 m/s = 72 km/h) than previously considered, even in the presence of high levels of road surface roughness.
This study examines experimentally and numerically the performance of a full-scale bamboo truss footbridge. The truss is built of multi-culm bamboo axial members with bolted steel connections, joined ...together via steel gusset plates. The study proposes a hierarchical simulation approach with the aid of existing and new material/structural member experimental test results. Specifically, it models first the non-linear (bilinear) behaviour of the multi-culm bamboo structural members, and then using the structural member model as building block, it creates a non-linear model of the entire truss structure. The proposed numerical simulations return realistic force–displacement response of the truss structure. The axial deformation of truss members is mostly due to bolt deformation and embedment, since the bamboo culms are significantly stiffer than the bolted connections. The simulated yielding and damage modes occur at similar locations in the truss structure as those observed experimentally. The simulated sequence of damage modes is affected by the natural variability of bamboo culms. Overall, the developed simulations are promising towards predicting via a hierarchical systematic modelling approach, the non-linear response of the bamboo structures, after modelling the behaviour of its multi-culm bamboo structural members.
•An original full-scale bamboo footbridge is examined numerically and experimentally.•The truss structure is modelled using a hierarchical simulation approach.•The numerical simulations consider the non-linear behaviour of structural members.•The simulated force–displacement response of the truss structure agrees with reality.•The sequence of damage modes is sensitive to the natural variability of bamboo culms.
•Critical review of literature since 1980s on tensile performance of cast-in anchors.•Thorough investigation of concrete cone failure mode of cast-in anchors.•Recent developments and modifications to ...concrete cone design (CCD) method.•Shortcomings of current methods to assess concrete cone failure of cast-in anchors.
The Concrete Capacity Design (CCD) method, which was first proposed in 1995, has since been adopted in design standards worldwide because of its accuracy and simplicity. With advancements in concrete technology and construction industry, there are new applications whereby the behaviour of anchors cannot be predicted by the original formulation of the CCD method. This paper intends to provide a comprehensive review of the recent research on tensile behaviour of single cast-in headed anchors failing due to a concrete cone failure mode without the influence of concrete edge. The review includes, but is not limited to, studies on the effect of deep embedment of anchors, anchor head size, variation in size and shape of concrete aggregates, prestressed concrete, fibre-reinforced concrete, high strength concrete, lightweight concrete, as well as age of concrete at the time of loading on behaviour of anchors. Where discrepancy is found in the literature, critical review is presented through an in-depth examination of available results. In addition to recent modified (CCD) prediction models, older models are also presented for a better demonstration of how prediction models have evolved over the past five decades. The paper concludes with a detailed list of identified knowledge gaps in the area and proposals for future work.
•Experimental study to investigate the stress distribution around a conduit buried within a soil slope.•Prediction of the soil-conduit interaction using experimental, numerical and analytical ...means.•Detailed explanation of the relevant mechanisms.•Regression analysis.
The use of conduits for transportation of utilities is very common around the world. The safe design and installation of these conduits depend upon the understanding of the soil-conduit interaction and the resulting stress distribution. This research paper presents a laboratory model test investigation of the effect of crest distance of the conduit buried within a sandy soil slope on the stress distribution around it and its structural response to the applied surface pressure. The crest distance of the conduit was varied from 0.25Bc to 2Bc; Bc being the outer diameter of the conduit. The results show that the stress distribution around the conduit buried within the soil slope differs significantly as compared to the conduit buried under the horizontal ground. The crest distance of the conduit from the slope edge and the resulting soil-conduit interaction governs the stress distribution and its structural response to the applied pressure. The graphical presentations, and the predicted soil-conduit interactions, as included in this paper, can be used routinely by the practicing engineers for the safe design and installation of the conduits buried within a soil slope.
•Plain bolted connections fail early by brittle splitting of bamboo culms.•Hose-clamps resist brittle splitting drastically increasing strength and ductility.•Cement mortar infill further increases ...the strength but diminishes the ductility.•Sufficient end-length inhibits culm-damage and allow higher bolt deformation.•The European Yield Model accurately predicts connection yield loads.
The present research examines experimentally the performance of a new type of full-culm bamboo to steel bolted connection under monotonic axial loading. The examined culms are of the Kao Jue (Bambusa pervariabilis) bamboo species. The study characterizes the performance of the proposed bamboo to steel connections in terms of failure modes, load-carrying capacity and ductility. It specifically examines the influence on the mechanical behavior of (a) the end-length (i.e. the distance between bamboo culm-end and outer bolt-hole); (b) the transverse confinement provided by hose-clamps, and (c) the grouted cement mortar added within the connection zones. The findings reveal that hose-clamps effectively resist the brittle splitting behavior observed in plain bamboo to steel - bolted connections. Combined with adequate end-lengths the connections achieve remarkable gains in strength and ductility. The results also show that the mortar infill results to connections of higher strength, but often at the cost of reduced ductility, compared to the pertinent hollow-section connections with hose clamps. Importantly, the analytically estimated yield loads of the examined connections using the European Yield Model are in good agreement with the experimentally determined values.
This study experimentally investigates the axial response of bamboo to steel connections under quasi-static reversed cyclic loading. It examines three different connection configurations: (Type A) ...plain bolted; (Type B) transversely confined by hose-clamps; (Type C) transversely confined by hose-clamps and infilled with cement mortar. The study specifically evaluates the effects of loading history in terms of strength degradation, pinching and dissipated energy, and recommends equivalent viscous damping coefficients. In general, the Type B and C connections are superior to Type A; they develop higher strength, possess ductile failure modes and dissipate more hysteretic energy. Compared to the monotonic response however, their cyclic performance is limited by early bolt-fracture. Nevertheless, the examined connections show promise towards a capacity-based design as the ductile components (i.e., the bolts) fail before the brittle components (i.e., the culms). All members are composed of pairs of Bambusa pervariabilis (Kao Jue) bamboo culms.
•Plain bolted connections suffer longitudinal splitting and show poor cyclic performance.•Hose-clamps with or without infill arrest splitting and improve cyclic performance.•Early bolt-fracture limits the strength and ductility during cyclic loading.•Cyclic deterioration occurs mainly by embedment and plastic deformation of bolts.•Bolt-embedment creates cavities in the culm-wall and pinched hysteresis loops.
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