Response Modification Factors for Concrete Bridges in Europe

The paper presents a methodology for evaluating the actual response modification factors (q or R) of bridges and applies it to seven concrete bridges typical of the stock found in southern Europe. The usual procedure for analytically estimating the q-factor is through pushover curves derived for the bridge in (at least) its longitudinal and transverse directions. The shape of such curves depends on the seismic energy dissipation mechanism of the bridge; hence, bridges are assigned to two categories, those with inelastically responding piers and those whose deck is supported through bearings on strong, elastically responding piers. For bridges with yielding piers, the final value of the q-factor is found as the product of the overstrength-dependent component (qs) and the ductility-dependent component (qμ), both estimated from the pertinent pushover curve. For bridges with bearings and nonyielding piers of the wall type, an equivalent q-factor is proposed, based on spectral accelerations at failure and at design level. In this paper, pushover curves are also derived for an arbitrary angle of incidence of seismic action using a procedure recently developed by the authors, to investigate the influence of the shape of the pushover curve on the estimation of q-factors. It is found that in all cases the available force reduction factors are higher than those used for design to either Eurocode 8 or AASHTO specifications

Characterizing the performance of transversely confined multi-culm bamboo to steel connections

The present research experimentally examines the axial behavior of transversely confined multi-culm bamboo to steel connections, using Kao Jue (Bambusa pervariabilis) bamboo species. The study characterizes under axial monotonic loading, the performance in terms of strength, ductility and failure modes. It then evaluates changes in performance under axial quasi-static reversed cyclic loading. Findings reveal that transverse confinement (through hose-clamps) is highly effective in preventing longitudinal splitting of bamboo culms. The connections exhibit large plastic deformations with sufficient strength and ductility. When compared to the monotonic response, early bolt-fracture hinders the cyclic performance. The connections nevertheless comply with the philosophy of capacity-based design — the ductile components (i.e. the bolts) fail before the brittle components (i.e. the culms). Notably, the adopted European Yield Model can analytically estimate the experimental yield loads with good accuracy. This ultimately indicates a path towards a more rational and engineered design of bamboo structures

Characterizing the performance of transversely confined multi-culm bamboo to steel connections

The present research experimentally examines the axial behavior of transversely confined multi-culm bamboo to steel connections, using Kao Jue (Bambusa pervariabilis) bamboo species. The study characterizes under axial monotonic loading, the performance in terms of strength, ductility and failure modes. It then evaluates changes in performance under axial quasi-static reversed cyclic loading. Findings reveal that transverse confinement (through hose-clamps) is highly effective in preventing longitudinal splitting of bamboo culms. The connections exhibit large plastic deformations with sufficient strength and ductility. When compared to the monotonic response, early bolt-fracture hinders the cyclic performance. The connections nevertheless comply with the philosophy of capacity-based design — the ductile components (i.e. the bolts) fail before the brittle components (i.e. the culms). Notably, the adopted European Yield Model can analytically estimate the experimental yield loads with good accuracy. This ultimately indicates a path towards a more rational and engineered design of bamboo structures

Application of short-time stochastic subspace identification to estimate bridge frequencies from a traversing vehicle

© 2020 Elsevier Ltd 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