André Plumier

Behaviour of connections

This paper provides an overview of the state of the art in connection design. The general principles and the various ductile and non-ductile local phenomena of the connection zone are reviewed, with a particular emphasis on the influence of the real yield stress distribution. Recent test results corresponding to various types of structures, various connecting techniques on site, rigid or semi-rigid connections are analysed. This review is completed by a summary on modelling of the connections zones. Conclusions bear on general design principles and define some research needs.

General report on local ductility

Abstract A series of factors contributes to the poor local ductility of steel structures, which was observed during recent earthquakes in the USA and Japan. These factors are explained. The factors on the resistance side are the discrepancies between real and design yield stress, the value of through thickness resistance of steel, the need for requirements on toughness of the base and weld material and the effect of strain rate. On the action effect side, other factors contributed to a bad ductility: the past underestimates of needed plastic rotations, the existence of 3D stress states created in welded connections of high beams, the consideration of wrong stress distributions in beam ends, a bad design of connections and the influence of the composite character of beams. The recent trends aiming at an improved local ductility are explained. They consist in forcing the development of plastic hinges in beams of moment frames to take place away from the columns, by either a connection strengthening or a beam weakening. Qualified connections are being developed. The other connections should go through a severe qualification process. However, future research work could relax this request by developing explicit requirements on the connections themselves.

Seismic resistance of steel and composite frame structures

Abstract A recent research programme on prefabricated composite steel concrete structures under seismic loading provides information on the behaviour of various design of connections in steel frames and on the influence of concrete on the mechanical behaviour of the beam-column connection zone. Practical conclusions for better design and simple computation approach of the plastic resistance of composite regions under cyclic loading are proposed.

Seismic Behavior of Thin-Bed Layered Unreinforced Clay Masonry Shear Walls Including Soundproofing Elements

According to the current standards, unreinforced masonry may only be used in regions of low seismicity as the material for the lateral-load resisting system. This requirement may be too safe-sided and leading to not cost-effective solutions for moderately seismic regions. This chapter presents overview of experimental results from shake table tests on unreinforced masonry shear walls carried out in the EQUALS Laboratory of Bristol University, in order to assess, and possibly enhance, the current seismic design rules. The study also includes as additional parameter the presence of soundproofing devices required in buildings with numerous dwellings, in order to achieve the acoustic isolation recommended by recent standards. In practice the required level of acoustic isolation is obtained by locating horizontal rubber layers in the wall. These layers are likely to influence significantly the dynamic response of the wall and hence of the whole structure under seismic actions. Tests are performed on walls realized with masonry units and construction methods typical of North-Western Europe.

A Design Method for Walls with Encased Steel Profiles

The design of walls or columns with several encased steel profiles as reinforcement has similarities with classical reinforced concrete, but also original aspects which need specific design approaches. Until now there has been experimental research and numerical models, but simple design methods are lacking. In the proposed method, the classical truss model used to design reinforced concrete for shear is extended to bring in the encased profiles contribution to shear stiffness. This allows to distinguish the action effects in the steel profiles and in concrete and to make separate checks for shear of the steel profiles and the concrete section with transverse reinforcements. A method to evaluate longitudinal shear action effects and the compression stresses at the steel profile – concrete interface is developed. Design checks in the format of Eurocodes 2 and 4 are proposed.

Overview of Seismic Hazard and Vulnerability of Ordinary Buildings in Belgium: Methodological Aspects and Study Cases

Northwest Europe is a region in which damaging earthquakes exist. Assessing the risks of damages is useful, but this is not an easy work based on exact science.In this paper, we propose a general tool for a first level assessment of seismic risks (rapid diagnosis). General methodological aspects are presented. For a given building, the risk is represented by a volume in a multi‐dimensional space. This space is defined by axes representing the main parameters that have an influence on the risk. We notably express the importance of including a parameter to consider the specific value of cultural heritage.Then we apply the proposed tool to analyze and compare methods of seismic risk assessment used in Belgium. They differ by the spatial scale of the studied area. Study cases for the whole Belgian Territory and for part of cities in Liege and Mons (Be) aim also to give some sense of the overall risk in Belgium.

Numerical Study of the Fatigue Crack in Welded Beam-To-Column Connection Using Cohesive Zone Model

The fatigue behaviour of the welded beam-to-column connections of steel moment resisting frame in seismic area must be evaluated. The cohesive zone model is an efficient solution to study such connections by finite elements. It respects the energetic conservation and avoids numerical issues. A three-dimensional cohesive zone model element has been implemented in the home made finite element code Lagamine [1]. It is coupled with the fatigue continuum damage model of Lemaître and Chaboche [2]. The cohesive parameters are identified by the inverse method applied on a three points bending test modelling.

Seismic Resistant Composite Structures

In the beginning of the years 1990’s very little design guidance did exist for the seismic design of composite steel concrete structure. The available test data were rather scarce, like were the numerical analysis.

Experimental Study Regarding Shear Behavior of Concrete Walls Reinforced by Multiple Steel Profiles

The objective of the present contribution is to present the outcomes of an experimental campaign carried out in the frame of the European research program Smartcoco and aiming at validating a design approach for determining the shear performances of RC wall reinforced by multiple encased steel profiles. The experimental campaign comprises 6 walls, ranging from a classical RC wall taken as a reference to configurations with multiple profiles with studs or plate stiffeners to ensure the transfer of the longitudinal shear at the steel-concrete interface. Vertical cantilever tests were performed on the specimens specifically detailed to fail in shear. Tests are carried out on walls with a width of 240 mm, a length of 880 mm and a height of 2250 mm with a regular concrete quality (C25/30). This contribution describes the test specimens, summarizes their design, presents a summary of the most relevant observations and a short interpretation of the obtain results. It is concluded from this set of tests that the new design method is able to predict the shear capacity with a good accuracy and can therefore be considered as a suitable solution for designing practical cases.

Transfer of the Longitudinal Shear at the Steel-Concrete Interface in Concrete Members Reinforced by Steel Profiles

The European research project SmartCoCo (Smart Composite Components) aims at elaborating a design methodology to be used for all situations in which steel profiles are used to reinforce locally what for else remains a classical reinforced concrete structure. In this framework, an experimental campaign is carried out to study the transfer of compression/tension forces from a steel profile to the surrounding concrete by longitudinal shearing of the steel-concrete interface without creating local disturbances, like transverse cracking or splitting of concrete around the steel profile. The present paper presents the general context and the proposed design methodology. It describes then the test specimens, test procedure and results. It concludes with recommendations for the calibration of the design procedure, including values of the bond resistance, shear resistance associated to a load transfer using mechanical connectors (shear studs or welded plate) and detailing of the transverse reinforcement.