Hervé Degée

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.

Effect of the steel material variability on the seismic capacity design of steel-concrete composite structures: a parametric study

Modern seismic codes recommend the design of ductile structures able to absorb seismic energy through high plastic deformation. Since seismic ductile design relies on an accurate control of plastic hinges formation, which mainly depends on the distribution of plastic resistances of structural elements, efficiency of the design method strongly depends on the actual mechanical properties of materials. The objective of the present contribution is therefore to assess the impact of material variability on the performance of capacity-designed steel-concrete composite moment resisting frames.

Volcano-related materials in concretes: a comprehensive review

Massive volcano-related materials (VRMs) erupted from volcanoes bring the impacts to natural environment and humanity health worldwide, which include generally volcanic ash (VA), volcanic pumice (VP), volcanic tuff (VT), etc. Considering the pozzolanic activities and mechanical characters of these materials, civil engineers propose to use them in low carbon/cement and environment-friendly concrete industries as supplementary cementitious materials (SCMs) or artificial/natural aggregates. The utilization of VRMs in concretes has attracted increasing and pressing attentions from research community. Through a literature review, this paper presents comprehensively the properties of VRMs and VRM concretes (VRMCs), including the physical and chemical properties of raw VRMs and VRMCs, and the fresh, microstructural and mechanical properties of VRMCs. Besides, considering environmental impacts and the development of long-term properties, the durability and stability properties of VRMCs also are summarized in this paper. The former focuses on the resistance properties of VRMCs when subjected to aggressive environmental impacts such as chloride, sulfate, seawater, and freezing–thawing. The latter mainly includes the fatigue, creep, heat-insulating, and expansion properties of VRMCs. This study will be helpful to promote the sustainability in concrete industries, protect natural environment, and reduce the impacts of volcano disaster. Based on this review, some main conclusions are discussed and important recommendations regarding future research on the application of VRMs in concrete industries are provided.

Influence of variability of material mechanical properties on seismic performance of steel and steel–concrete composite structures

Modern standards for constructions in seismic zones allow the construction of buildings able to dissipate the energy of the seismic input through an appropriate location of cyclic plastic deformations involving the largest possible number of structural elements, forming thus a global collapse mechanisms without failure and instability phenomena both at local and global level. The key instrument for this purpose is the capacity design approach, which requires an appropriate selection of the design forces and an accurate definition of structural details within the plastic hinges zones, prescribing at the same time the oversizing of non-dissipative elements that shall remain in the elastic field during the earthquake. However, the localization of plastic hinges and the development of the global collapse mechanism is strongly influenced by the mechanical properties of materials, which are characterized by an inherent randomness. This variability can alter the final structural behaviour not matching the expected performance. In the present paper, the influence of the variability of material mechanical properties on the structural behaviour of steel and steel/concrete composite buildings is analyzed, evaluating the efficiency of the capacity design approach as proposed by Eurocode 8 and the possibility of introducing an upper limitation to the nominal yielding strength adopted in the design.

A preliminary assessment of slenderness and overstrength homogeneity criteria used in the design of concentrically braced steel frames in moderate seismicity

This study has been realized thanks to the research fund received from European commission with the contract MEAKADO RFSR-CT-2013-00022.

Seismic Behaviour of Thin-Bed Layered Unreinforced Clay Masonry Frames with T- or L-Shaped Piers

According to current standards, the use of unreinforced masonry is only recommended in regions of low to moderate seismicity as a resisting system to carry earthquake-induced horizontal forces. This requirement is however felt as rather conservative and leading to uneconomical constructive solutions, in particular for low seismic regions. Moreover, the seismic analysis of masonry structures has to be performed along two main perpendicular directions, usually neglecting the contribution of wall elements perpendicular to the seismic action. Horizontal elements (spandrel, etc.) are also commonly disregarded. In such a context, the present contribution provides an overview of experimental results obtained from shake table tests on unreinforced masonry frames carried out in the EQUALS Laboratory of Bristol University in order to assess, and possibly enhance, current design rules. The study is focused on the contribution of walls perpendicular to the seismic action and on the influence of the frame effect induced by the coupling of the walls through horizontal reinforced concrete elements, such as lintels and floor slabs. Another point of interest of the study is the influence of the gravity loading situation, comparing a floor slab supported by the shear walls as well as by the perpendicular elements, with a floor slab supported by the perpendicular walls only. Tests are performed on walls constructed with units and construction methods typical of the North-Western European region.

Rocking behaviour of simple unreinforced load-bearing masonry walls including soundproofing rubber layers

This paper compares experimental measurements with predictions of different rocking models. These comparisons are carried out on the base of recent experimental results obtained by shake-table tests of four simple unreinforced load-bearing clay masonry walls that have exhibited a significant rocking behaviour for the highest acceleration inputs. In a first stage, the simple model proposed by Housner is used after slight modifications needed to properly consider the actual mass distribution. Two parameters are identified as governing the model response, namely the criterion defining the initiation of motion and the restitution coefficient. Then, a two stacked blocks model is developed and solved by an event-driven strategy. This two-block model is intended to allow a better description of the behaviour of tested specimens through a more precise modelling of the additional mass. Finally, the presence of rubber layers positioned at the top and bottom of two of the tested walls with the purpose of improving their acoustic behaviour required the development of an updated rocking model with viscous and flexible interfaces at the base of the wall and between the two stacked blocks. The properties of these interfaces are deduced from experimental data and their significant influence on the response is evidenced.

Non Gaussian Response of Bridges Subjected to Turbulent Wind – Effect of the non Linearity of Aerodynamic Coefficients

Wind loads acting of bluff bodies like bridge decks are complex functions of the components of the turbulence and of the structural displacements and velocities. In order to simplify the representation of these loads, approached models are generally considered. Since a convenient linear approximation gives accurate results in many cases, such a model has been widely used during last decades. Some researchers have however showed that it is possible, and even necessary, to account for the non linearity of this kind of loading. Such a non linearity is likely to come either from the squared velocity or from the shape of the aerodynamic coefficients as functions of the wind angle of attack.

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.

Application of Variance Analyses Comparison in Seismic Damage Assessment of Masonry Buildings Using Three Simplified Indexes

The reasonable assessment of potential damage type of masonry structures in seismic-prone zone is very significant to strengthen existing masonry structures and guide the construction of the new building. The primary objective of the study is to propose and determine a reasonable assessment index to predict the damage type of masonry structures in different seismic intensity zones using the survey results of the 2008 Wenchuan earthquake and variance analyses comparison methods. Three potential theory assessment indexes are considered in the evaluation of damage of masonry structures, including wall density index , strength index , and combined index . In order to compare the feasibility of the three indexes, One-way analysis of variance and Scheffe’s method were used for in-depth discussion. Based on the proposed assessment indexes, further analyses and recommendations were provided. Results show the combined index has a high potential to predict the damage levels of masonry structures. Based on the study, several recommendations were provided for the masonry structures in seismic-prone zones.