TY - JOUR

T1 - Collapse processes and associated loading of square light-frame timber structures due to bore-type waves

AU - Krautwald, Clemens

AU - von Häfen, Hajo

AU - Niebuhr, Peter

AU - Vögele, Katrin

AU - Stolle, Jacob

AU - Schimmels, Stefan

AU - Schürenkamp, David

AU - Sieder, Mike

AU - Goseberg, Nils

N1 - Funding Information: Four pressure transducers were installed in the centerline of the front panel (PS 1–4). These pressure sensors were mounted to the rigid structure only, since a structural collapse would potentially cause damage to these sensors. Therefore, pressure data on rigid structures exist and could be used for calibration procedures. However, they are not used in this study since a comparison of the pressure distribution with elasto-plastic structures is not possible. A multi-axis sensor was installed underneath the structures to acquire total forces and moments in all spatial directions (cf. Fig. 3). Fig. 3 a) shows the adjustable steel substructure that was required for perfect alignment of the multi-axis sensor. Furthermore, the multi-axis sensor (IP68) could not be permanently submerged for longer durations as per ingress protection rating, so a drainage procedure by small pumps was carried out at the end of each test day. Four inertial measurement units (IMU) were installed on the timber studs supporting the front panels (IMU 1–4). Each inertial measurement unit recorded three-dimensional (3D) acceleration, turn rate as well as magnetic field intensity. On the one hand, the IMUs transmit the data in real time to a gateway, which also ensures synchronous triggering, and on the other hand, the data is stored locally on the IMU. However, the data could only be partially recovered after the tests, and as a result, the incomplete data is not used in this study. Two high-speed cameras were mounted at a height of z = 11.6 m with their field of view (FOV) directed towards the horizontal platform. High-speed camera images allow to investigate the structural failure process in detail, however, the reader is referred to von Häfen et al. (2022) for a discussion on a more detailed analysis of the hydrodynamics using large-scale PIV methods.A second failure mechanism (ii) is associated with the insufficient transfer of tensile forces at the roof's rear joist, visualized by high-speed camera photographs in Fig. 11 and illustrated with a schematic sketch in Fig. 12. Initially, the structural front is bent towards the inside comparable to failure mechanism (i) but in this case the studs remain sturdy (Fig. 11 (b)). Instead, the roof sheathing gets detached from the rear joist, interrupting the shear transfer from the sheathing to the rear joist and causing a sideward rotation of the sheathing. Therefore, the collapse is initiated at the rear side of the structure and causes the roof to lose its structural integrity. Further, the structural front loses support from the roof so the front studs have to transfer increased loads towards the bottom plate and get ultimately damaged. This failure mechanism is accompanied by a sudden upward movement of the roof that is partially overtopped as the entire failure occurs at a later stage (Fig. 11 (d)). Furthermore, the collapse process is supported by the load time-histories (Fig. 11 (a)), where the load curves are comparable between the two structures for the entire impulsive phase up to the quasi-steady phase at t = 1.6 s. This indicates that the high forces during the impulsive phase could be transferred via the front studs, while subsequently the structural deformation became so severe that the bore separated individual fastener connections – in this case by dislodging the roof from the lateral walls.As part of the Volkswagen Foundation project “Beyond Rigidity - Collapsing Structures in Experimental Hydraulics”, this work was sponsored under the funding code 93826.The authors are indebted to the technical staff and student assistants involved in the construction of the specimens at iBHolz at Technische Universität Braunschweig. Further, the authors express their gratitude to the technical staff at the Coastal Research Center, Hannover, and the Leichtweiβ-Institute for Hydraulic Engineering and Water Resources who greatly eased conducting experiments at large-scale. The cost of operation of the large wave flume at Coastal Research Center is jointly covered by the Leibniz University Hannover and Technische Universität Braunschweig. The support of the Volkswagen Foundation (project ‘Beyond Rigidity - Collapsing Structures in Experimental Hydraulics’, No. 93826) through a grant held by N. Goseberg is greatly acknowledged. Funding Information: As part of the Volkswagen Foundation project “Beyond Rigidity - Collapsing Structures in Experimental Hydraulics”, this work was sponsored under the funding code 93826 .

PY - 2022/10

Y1 - 2022/10

N2 - Extreme hydrodynamic events such as hurricanes or tsunamis threaten coastal regions in particular. Such hazards must be assessed and appropriately incorporated into building codes to mitigate casualties and damages to coastal structures. Guidelines are often developed through experimental investigations that assume buildings remain rigid during hydrodynamic loading. To challenge this ‘rigid building paradigm’, test specimens were designed to replicate the deformation characteristics of an idealized light-frame timber structure using Froude-Cauchy similarity. Subsequently, a large-scale experimental study was conducted at the Large Wave Flume of the Coastal Research Center in Hannover. Hydrodynamic loads and load gradients were investigated to describe both the influence of an elasto-plastically modeled test specimen compared to a rigid reference model and the effect of load history on the structural loads. Finally, the collapse sequences of elasto-plastic specimens were extracted from high-speed photographs and classified into three failure mechanisms. In this study, data analyses are presented with the intention to not only inform local authorities for future development of guidelines but also serve as calibration and validation data for improving numerical methods.

AB - Extreme hydrodynamic events such as hurricanes or tsunamis threaten coastal regions in particular. Such hazards must be assessed and appropriately incorporated into building codes to mitigate casualties and damages to coastal structures. Guidelines are often developed through experimental investigations that assume buildings remain rigid during hydrodynamic loading. To challenge this ‘rigid building paradigm’, test specimens were designed to replicate the deformation characteristics of an idealized light-frame timber structure using Froude-Cauchy similarity. Subsequently, a large-scale experimental study was conducted at the Large Wave Flume of the Coastal Research Center in Hannover. Hydrodynamic loads and load gradients were investigated to describe both the influence of an elasto-plastically modeled test specimen compared to a rigid reference model and the effect of load history on the structural loads. Finally, the collapse sequences of elasto-plastic specimens were extracted from high-speed photographs and classified into three failure mechanisms. In this study, data analyses are presented with the intention to not only inform local authorities for future development of guidelines but also serve as calibration and validation data for improving numerical methods.

KW - Bore

KW - Collapse process

KW - Hydrodynamic loading

KW - Physical model experiment

KW - Tsunami

KW - Wood-frame structures

UR - http://www.scopus.com/inward/record.url?scp=85135403686&partnerID=8YFLogxK

U2 - 10.24355/dbbs.084-202208291215-0

DO - 10.24355/dbbs.084-202208291215-0

M3 - Article

AN - SCOPUS:85135403686

VL - 177

JO - Coastal engineering

JF - Coastal engineering

SN - 0378-3839

M1 - 104178

ER -