181 research outputs found
Serviceability assessment of the GĂłis footbridge using vibration monitoring
Footbridges are structures that may experience vibration amplification problems caused
by pedestrian and/or wind actions. Design codes deal with these phenomena limiting
the natural frequencies and the maximum accelerations expected. Aiming at taking into
consideration these dynamic phenomena, current procedures to evaluate the structural
performance of light-weight bridges based on experimental dynamic analysis are evaluated
in this study. To achieve this, the dynamic response of three pedestrians walking, running
and jumping was obtained. Maximum comfort limits of dynamic responses were then
determined. The results indicate that codes could overestimate the level of vibration in
this kind of footbridge(undefined
Single step joint: overview of European standardized approaches and experimentations
In the field of the built heritage restoration, engineers have to work with old structures made of badly preserved timber elements. The assessment of timber elements and connections is a major issue for engineers involved in a restoration project. Before thinking about any intervention technics, engineers have to properly understand how the carpentry connections fail, which parameters influence the failure modes (geometry of the joint, mechanical properties of the wood,…) and how the internal forces are distributed into the joint to finally figure out how to design the traditional carpentry connections. The present paper aims to raise those questions focusing on the Single Step Joint design. Even if this common joint between the rafter and the tie beam is geometrically simple, one may pick up three geometrical configurations of Simple Notched Joints from the past till today: the geometrical configuration ideal (GCID), the geometrical configuration perpendicular to the tie beam (GCPTB) and the geometrical configuration perpendicular to the rafter (GCPR). The first one is more recent because it requires a highest accuracy production, and so the use of the new technologies (e.g., CNC). For each one, some general design rules about the geometrical parameters of the Single Step Joint are defined by some European standards (Siem and Jorissen, 2015), but no one details how to design this connection to prevent shear cracks at the heel depth or the compressive crushing at the joint contact surfaces. Hence the design rules and the emergence of failure modes according to the geometrical parameters of the Simple Notched Joint must be defined. In order to check the design equations and the failure modes, lab tests about the three geometrical configurations of the Single Step Joint have been carried out, varying the heel depth, the shear length and the inclination of the rafter
Steel fibre reinforced concrete for elements failing in bending and in shear
Discrete steel fibres can increase significantly the bending and the shear resistance of concrete
structural elements when Steel Fibre Reinforced Concrete (SFRC) is designed in such a way that fibre
reinforcing mechanisms are optimized. To assess the fibre reinforcement effectiveness in shallow structural
elements failing in bending and in shear, experimental and numerical research were performed. Uniaxial
compression and bending tests were executed to derive the constitutive laws of the developed SFRC. Using a
cross-section layered model and the material constitutive laws, the deformational behaviour of structural
elements failing in bending was predicted from the moment-curvature relationship of the representative cross
sections. To evaluate the influence of the percentage of fibres on the shear resistance of shallow structures, three
point bending tests with shallow beams were performed. The applicability of the formulation proposed by
RILEM TC 162-TDF for the prediction of the shear resistance of SFRC elements was evaluated. Inverse
analysis was adopted to determine indirectly the values of the fracture mode I parameters of the developed
SFRC. With these values, and using a softening diagram for modelling the crack shear softening behaviour, the
response of the SFRC beams failing in shear was predicted.Fundação para a Ciência e a Tecnologia (FCT
An experimental and analytical investigation of reinforced concrete beam-column joints strengthened with a range of CFRP schemes applied only to the beam
This paper investigates the experimental and analytical behaviour of beam-column joints that are subjected to a combination of torque, flexural and direct shear forces, where different Carbon Fibre Polymer (CFRP) strengthening wraps have been applied only to the beam. These wrapping schemes have previously been determined by the research community as an effective method of enhancing the torsional capacities of simply supported reinforced concrete beams. In this investigation, four 3/4-scale exterior beam-column joints were subjected to combined monotonic loading; three different beam wrapping schemes were employed to strengthen the beam region of the joint. The paper suggests a series of rational formulae, based on the space truss mechanism, which can be used to evaluate the joint shear demand of the beams wrapped in these various ways. Further, an iterative model, based on the average stress-strain method, has been introduced to predict joint strength. The proposed analytical approaches show good agreement with the experimental results. The experimental outcomes along with the adopted analytical methods reflect the consistent influence of the wrapping ratio, the interaction between the combined forces, the concrete strut capacity and the fibre orientation on the joint forces, the failure mode and the distortion levels. A large rise in the strut force resulting from shear stresses generated from this combination of forces is demonstrated and leads to a sudden-brittle failure. Likewise, increases in the beams’ main steel rebar strains are identified at the column face, again influenced by the load interactions and the wrapping systems used
Residual properties of normal-strength concrete subjected to fire and sustained elevated temperatures: A comparative study
Creep behaviour of sandwich panels with rigid polyurethane foam core and glass-fibre reinforced polymer faces: Experimental tests and analytical modelling
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