Plastic hinge models for the displacement-based assessment of wall-type bridge piers with poor detailing

This paper presents a plastic hinge modelling approach for wall-type bridge piers with detailing deficiencies such as low transverse reinforcement ratios and lap splices in potential plastic hinge regions. Currently available plastic hinge length estimates and strain limits are validated against a series of seven large scale tests, representing poorly detailed bridge piers. Besides the flexural deformations, which are predicted with the plastic hinge approach, the shear deformations need to be taken into account due to the geometry and detailing of the considered piers. Shear-flexure interaction is accounted for by relating the shear distortion to the axial strains in the plastic hinge. Lap splices in potential plastic hinge regions have a significant influence on the displacement capacity of the structure as their degradation may lead to a nearly instant loss of lateral load bearing capacity. Hence, strain limits defining the onset of splice degradation are assessed using the experimental data

Behaviour of poorly detailed lap-splices under cyclic loading

This paper presents the first part of a series of uniaxial cyclic tests on lap-splices. The work is conducted within the framework of a project on the seismic behaviour of existing, poorly detailed bridge piers which are typically constructed with a lap-splice above the footing. The test series presented here was initiated to study the influence of load history, specially with regards to the compression levels, and confinement on the behaviour of lap-splices. The test units represent the boundary elements of previously tested large scale bridge piers. This paper describes three tests on units with varying transverse reinforcement ratios, which were subjected to the same cyclic load history, in more detail. Particular attention is given to their failure modes and selected measurements, such as slip of the bars and concrete strain levels, are presented

Probabilistic mechanics-based loss scenarios for school buildings in Basel (Switzerland)

Developing earthquake scenarios for cities in areas with a moderate seismicity is a challenge due to the limited amount of available data, which is a source of large uncertainties. This concerns both the seismic hazard, for which only recordings for small earthquakes are available and the unknown earthquake resistance of the majority of structures not designed for seismic loading. The goal of the present study is to develop coherent probabilistic mechanics-based scenarios for a mid-size building stock including a comprehensive analysis of the uncertainties. As an application, a loss assessment for the school buildings of the city of Basel is performed for different scenarios of historical significance, such as the 1356 event, and from the deaggregation of the Swiss Probabilistic Seismic Hazard Model of 2015. The hazard part of the computations (i.e. ground motion estimation) is based on this model, a regional microzonation and recordings of small earthquakes on a dense strong motion network to compute site-amplification factors. The school buildings, which are mainly unreinforced masonry or reinforced concrete shear wall buildings, have been classified according to a specifically developed taxonomy. Fragility curves have been developed using non-linear static procedures and subsequently, vulnerability curves in terms of human and financial losses are proposed. The computations have been run with the OpenQuake engine, carefully propagating all the recognized uncertainties. Scenarios before and after retrofitting measures show their impact on the earthquake safety. A sensitivity analysis shows that the largest uncertainties come from the ground motion prediction although an improvement of all parts of the model is necessary to decrease the uncertainties. Although improved data and models are still necessary to be developed, probabilistic mechanics-based models outperform the capabilities of deterministic and/or empirical models for retrieving realistic earthquake loss distributions

Evaluation of the Response of Shear Critical Walls Using a Three-Parameter Kinematic Theory

peer reviewedThis paper discusses a newly developed three-parameter kinematic theory (3PKT) for shear critical walls with the help of four wall tests. The 3PKT is used to predict the pre- and post- peak response of the test units. Comparisons are performed with finite element (FE) models and plastic hinge models in combination with a shear degradation model. It is found that the latter underestimate the displacement capacity of the walls while the former do not predict well the post-peak response. The 3PKT with only three degrees of freedom captures the complete response of the walls provided that the size of the critical loading zone (CLZ) of the wall is well predicted

Three-Parameter Kinematic Theory for Shear-Dominated Reinforced Concrete Walls: Implementation

The tree-parameter kinematic theory (3PKT) is aimed at addressing the need for physically accurate and computationally effective models for predicting the response of shear-dominated reinforced concrete walls. The theory is based on a three-degree-of-freedom kinematic model for the deformation patterns in walls with aspect ratios smaller than approximately 3. In the kinematic model the wall is divided into two parts - a rigid block and a fan of struts - by a diagonal crack. The mechanisms of shear resistance across this crack are modelled with non-linear springs to capture the pre- and post- peak shear behavior of the member. The base section of the wall is also modelled to account for yielding of the reinforcement and crushing of the concrete. The complete formulation of the 3PKT is presented in an ASCE Journal of Structural Engineering paper by Mihaylov, Hannewald and Beyer. The attached Matlab code represents an implementation of the 3PKT for time-efficient computation of the response of shear-dominated walls. The limits of applicability of the 3PKT and the code are defined in the ASCE paper