Experimental and numerical study of historic masonry with bed joint reinforced repointing

Induced seismicity due to gas extraction in the province of Groningen in the Nether- lands has a noticeable impact on building structures. Historic masonry structures in the area, which are non-engineered and lacking empirical design features often present in traditionally seismic regions, are especially vulnerable to dynamic loading. Compounding the problem, gas extraction additionally generates soil settlement, which can induce damage to masonry build- ings and thus reduce their capacity to bear seismic loads. The objective of this paper is the evaluation of the performance of a widely used structural intervention method applied in masonry structures in the Groningen region of the Netherlands. This method, initially developed against soil subsidence damage, consists in the embedment of stainless steel helical bars in repointed bed joints. Additionally, diagonal anchors are placed in drilled holes across existing cracks in the masonry. The increase in induced seismicity in Groningen raises the question whether this intervention technique can additionally enhance the behaviour of masonry structures during seismic loading. A masonry wall was experimentally tested in two configurations: a) a pre-damaged state, with simulated damage typical of imposed soil settlement, and b) a post-damaged and post- intervention state, this being the wall from the previous configuration after being tested to its maximum base shear and subsequently strengthened. Differences between the two configura- tions in terms of stiffness, peak force and prevalent damage patterns are discussed. Accompanying the experimental campaign, results of finite element simulations of the strength- ened wall are presented. The strengthened wall is simulated using non-linear macro-modelling techniques. The model accounts for the experimentally simulated damage as well as for the damage arising after the testing in the first configuration. The analysis results clarify and quantify the experimental observations on the strengthened wall, particularly as regards stress development and bond-slip in the reinforcement bars. Based on the experimental and numerical results, the effectiveness of the intervention in restoring the strength of the wall and in preventing the re-emergence of major diagonal cracking is confirmed.This research was funded by the Rijksdienst voor het Cultureel Erfgoed (RCE), part of the Ministerie van Onderwijs, Cultuur en Wetenschap (OCW), subsidy No. MS-2018-189, which is gratefully acknowledged.Peer ReviewedPostprint (published version

Experimental characterization of the axial behavior of traditional masonry wall metal tie connections in cavity walls

In recent years, the number of human-induced earthquakes in Groningen, a large gas field in the north of the Netherlands, has increased. The majority of the buildings are built by using unreinforced masonry (URM), most of which consists of cavity (i.e. two-leaf) walls, and were not designed to withstand earthquakes. Efforts to define, test and standardize the metal ties, which do play an important role, are valuable also from the wider construction industry point of view. The presented study exhibits findings on the behavior of the metal tie connections between the masonry leaves often used in Dutch construction practice, but also elsewhere around the world. An experimental campaign has been carried out at Delft University of Technology to provide a complete characterization of the axial behavior of traditional connections in cavity walls. A large number of variations was considered in this research: two embedment lengths, four pre-compression levels, two different tie geometries, and five different testing protocols, including monotonic and cyclic loading. The experimental results showed that the capacity of the connection was strongly influenced by the embedment length and the geometry of the tie, whereas the applied pre-compression and the loading rate did not have a significant influence

Numerical modelling of cavity wall metal ties

The assessment of the out-of-plane response of unreinforced masonry (URM) buildings with cavity walls has been a popular topic in regions such as Central and Northern Europe, Australia, New Zealand, China and several other countries. Cavity walls are particularly vulnerable as the out-of-plane capacity of each individual leaf is significantly smaller than the one of a solid wall. In the Netherlands, cavity walls are characterized by an inner load-bearing leaf of calcium silicate bricks, and by an outer veneer of clay bricks that has only aesthetic and insulation functions. The two leaves are typically connected by means of metallic ties. This paper utilizes the results of an experimental campaign conducted by the authors to calibrate a hysteretic model that represents the axial cyclic response of cavity wall tie connections. The proposed numerical model uses zero-length elements implemented in OpenSees with the Pinching4 constitutive model to account for the compression-tension cyclic behaviour of the ties. The numerical model is able to capture important aspects of the tie response such as the strength degradation, the unloading stiffness degradation and the pinching behaviour. The numerical modelling approach in this paper can be easily adopted by practitioner engineers who aim to model the wall ties more accurately when assessing the structures against earthquakes

A masonry catalogue for the Groningen region

Human induced seismicity has become an uprising problem in the Groningen region of The Netherlands, in which the vast majority of buildings are non-seismically engineered unreinforced masonry houses. In order to accurately assess the seismic vulnerability of these buildings, a characterization of the constitutive masonry is required. In 2015, as a part of a larger project, a campaign on the material characterization of existing buildings was performed, including laboratory and in-situ testing of the masonry walls. The campaign constitutes the germ for the creation of a regional material properties database. 16 buildings were tested in total, comprising residential structures and schools, dating from the early ‘20s to 2005. The constitutive walls included both clay and calcium silicate brick masonry of various qualities and conditions. The in-situ testing included non-destructive tests such as rebound hammer and sonic tests, and semidestructive test, i.e. flat jack and shove test. Samples were carefully taken to the laboratory, where the destructive campaign took place, including compressive, flexural, shear and bond wrench tests. Despite of the limited number of sampled buildings, the campaign provided a better insight of the researched material. The available data suggests that the use of sub-typologies (e.g. depending of the masonry quality or condition) could reduce the dispersion on the results. A first attempt of correlation between in-situ and laboratory tests is proposed, which could benefit from further calibration. In this paper, the material characterization campaign is described, and the main outcomes are discussed

Modeling the Structural Response of Reinforced Glass Beams using an SLA Scheme

This paper investigates whether a novel computational sequentially linear analysis (SLA) technique, which is especially developed for modeling brittle material response, is applicable for modeling the structural response of metal reinforced glass beams. To do so, computational SLA results are compared with experimental results of four-point bending tests. The results show similarities in loaddisplacement curves and to some extent also in cracking behaviour. Overall, it is concluded that the SLA scheme is a very promising technique to model the structural response of reinforced glass beams, which will be even further improved in future research

Regulatory impact assessment : a survey of selected developing and emerging economies

This article reports on an in depth survey of the practice of Regulatory Impact Assessment (RIA) in 16 developing and emerging economies. It reveals that RIA is playing an increasing role in these countries: eight have introduced RIA in the last ten years; one has recently redesigned its existing RIA system; another has a longstanding RIA system in place. However, RIA still remains at an early stage of development in the majority of cases and six countries do not practice RIA.http://www.tandfonline.com/loi/rpmm202017-08-31hb201