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Masonry structures, which differ from other types of structures in terms of construction techniques and the properties of load-bearing members, may have sufficient strength against vertical loads applying compressive stresses, but an insufficient level of strength against seismic loads involving tensile and shear stresses. Accordingly, it is necessary to seismically strengthen masonry structures to ensure their structural safety and to prolong their service life. The present study deals with the process of strengthening a historical masonry structure that was built in the late 19th century but was abandoned for many years after being used for various functions. The structure is currently planned to be refunctioned as a service building for a university through conventional and non-conventional techniques. The study is being planned in three phases, beginning with a research into the examined structure's historical process, followed by a seismic performance analysis and culminating in strengthening applications. In the building background survey, the functional changes that the structure has undergone since its construction are analyzed, and a numerical analysis is made to assess the seismic performance of the structure under earthquake loads in its current state. In the final stage, the strengthening applications for the load-bearing members of the structure are presented in detail. It is aimed for this study to serve as a representative application for the seismic retrofitting of historical masonry buildings.

This paper presents a new steel wind- and seismic-resisting wall, called a lever viscoelastic wall (LVEW) that includes a velocity-dependent VE damper and a displacement-dependent friction damper in a device, characterized by two different motion phases. In Phase one motion (i.e., small drifts), the VE damper which is activated by a lever delivers amplified lateral force and energy dissipation to the frame structure. In Phase two motion (i.e., medium-to-large drifts), the VE damper is constrained by a stopper and the friction damper, instead, is activated to provide frictional energy dissipation to the frame. The damping is provided by incorporating VE material and sliding friction in a wall configuration, reducing both the wind and earthquake responses of structures in a single unit. The objectives of the work were to (1) develop the force transfer mechanism and kinematics of the LVEW, (2) verify the cyclic response of LVEWs at low and large drifts, and (3) evaluate the limitation of LVEWs for the applications. Three full-scale LVEW specimens were designed and tested to validate the hysteretic response in two motion phases. The hysteretic response of LVEWs obtained from the test was compared to that from the analytical formulation.

Design codes (ACI 318-08, 2008; ACI Committee 352-02, 2010) place restrictions on the use of reinforced concrete (RC) wide-beam framing systems in regions of seismic hazard because there are little or insufficient information about their behavior under the effects of earthquake loads. The current study constitutes the second part of an experimental investigation carried out for (i) evaluating the seismic response of RC wide and shallow beam-narrow column joints when designed and detailed under gravity load; and (ii) for exploring the potential of improving the seismic performance of the same joints without introducing significant changes in the design and construction practices. The first part of the investigation concentrated on exterior joints, the results of which were reported elsewhere (Elsouri, 2013). This study concentrates on interior joints, in which four full-scale beam-column sub-assemblages were tested under quasi-static cyclic loading. Two of the joints, referred to as “as-built”, were designed and detailed for gravity load in accordance with local design and construction practices. The other two joints, referred to as “earthquake-resistant”, were also designed assuming gravity load but their reinforcement detailing were improved to satisfy part of the ACI 318-08 requirements and ACI-ASCE 352-02 recommendations for seismic-resistant structures. The as-built joints experienced shear failure within the joint core at early lateral drift. With a slight improvement of the reinforcement detailing, despite violating the limits of joint dimensions and some detailing requirements of ACI 318-08, the earthquake-resistant joints acquired considerably improved seismic performance by preventing or delaying joint shear failure; and by developing higher lateral load, deformation, and energy dissipation capacities when compared with the as-built joints.

Engineered cementitious composites are highly ductile materials, which can greatly improve the ductility of structures. However, there is no systematic design guide for composite structures with engineered cementitious composite. In this study, we investigated the hysteretic behavior of bridge columns with a plastic hinge enhanced by an engineered cementitious composite jacket for seismic resistance by pseudo-static test and numerical analysis. The results showed that the application of engineered cementitious composite jacket reduces the damage of the bridge column and improves its ultimate displacement tolerance and energy dissipation capacity. A height of engineered cementitious composite jacket no less than 1.5 times the column diameter and an axial compression ratio of 0.2 are recommended to ensure the integrity, lateral bearing capacity, and energy dissipation. This study provides valuable experience for the practical engineering application of engineered cementitious composite columns in seismic areas.

The steel slit panel–frame is a new system for seismic resistance of buildings. The steel slit panels are bolted to beams which are simply connected to the columns. The steel slit panels are steel plates with rows of vertical slits forming a series of flexural members within the plate. The steel slit panels are designed to resist the entire lateral load and provide all the stiffness and energy dissipation in the system. The steel slit panel–frame system was studied via an experimental program, divided into two series of testing. The first series studied the fundamental characteristics of the steel slit panels, while the second series studied the behavior of the steel slit panels within the frame (i.e., behavior of the steel slit panel–frames). A concise introduction to the system is presented first, followed by the findings from the experimental study.

This paper proposes an innovative type of two-level yielding steel coupling beams (TYSCB) to improve the seismic performance of coupled shear wall systems. The proposed TYSCB consists of two key components: shear-yielding beam and bending-yielding beam. For a minor earthquake, the former is expected to yield to dissipate energy while the latter still stays in elastic to provide the stiffness demand. Under a severe earthquake, both the shear and bending-yielding beams are designed to yield to dissipate seismic energy. Experiments are carried out on four full-scale TYSCB specimens to investigate their seismic behavior and yielding mechanism. These specimens vary in lengths, heat treatments of welding joints, web forms and strengthening of end joints. The experimental results show that TYSCBs have fully developed hysteresis behavior and the preferred yielding sequence. The equivalent damping coefficients of all the tested specimens reach up to 45%. The energy dissipation ability increase by 94% with only 27.3% reduction in stiffness compared with traditional complete steel coupling beams under minor earthquakes. On the other hand, its stiffness can increase by 37.5% with only 44.1% reduction in energy dissipation capacity compared with fuse steel coupling beams under minor earthquakes. A trilinear hysteretic model is proposed to reasonably simulate the cyclic behavior of TYSCBs. A nonlinear finite element model is also developed and validated against the test results. The hysteretic and finite element models are to facilitate the application of TYSCBs in the seismic design of shear wall systems.

The paper analyzes the seismic resistance of a ventilation stack on a reactor building, including the possible reserves of increasing the resistance. Structures of this type are highly sensitive to seismic loads, as the tuning of the stack (the spectrum of its lowest natural frequencies) corresponds with the frequency spectrum of excitation due to seismic effects. The purpose of the paper is to present an example of an actual structure to show the character of the response of the structure, and the participation of the individual frequency components of the response in the overall stress and strain state of a structure of this type. The methodology for a numerical analysis of the structure is also given. The load of the stack proper is modified by the transfer characteristics of the building. In engineering practice, the system is usually divided into two subsystems: the building with the sub-base, and the stack proper. The level of justification for the application of this simplification depends on the distance of the natural frequencies of the stack from the natural frequencies of the building. Finally, the paper deals with possible errors in determining the actual seismic resistance of the stack structure.

In this paper a Romanesque masonry church is analysed in order to assess its structural behaviour and its seismic vulnerability with respect to the actual state of conservation. Starting from a specific case study, a contribution to the issue of modelling and analysis of monumental masonry buildings under seismic action is provided. A finite element methodology for the static and dynamic nonlinear analysis of historical masonry structures is described and applied to the case study. A quasi-static approach (the seismic coefficient method) for the evaluation of the seismic loads has been used (as indeed is common in many analyses of the seismic behaviour of masonry structures). The comparison demand vs. capacity confirms the susceptibility of this type of building to extensive damage and possibly to collapse, as frequently observed. Moreover the actual efficiency of current techniques for repairing and strengthening are analyzed in order to evaluate their benefits. The analysis of repairing and strengthening techniques show the effectiveness of the usual structural reinforcement in terms of increased seismic capacity. The paper advocates that significant information can be obtained from advanced numerical analysis, namely with respect to the understanding of existing damage and to the minimum and adequate design of strengthening. A clear understanding of the structural behaviour and reliable strengthening, based on sophisticated tools of structural analysis, can therefore reduce the extent of the remedial measures in the restoration of ancient structures.

A CFT truss, in which the chord members comprise concrete-filled tubes (CFTs), may have an excellent capacity to deform, even under cyclically repeated loads such as earthquakes. This paper first provides a brief explanation of the two conditions necessary to prevent a CFT truss from chord-buckling. If both of the conditions are fulfilled, the truss has excellent ductility, making it desirable for use in new earthquake resistant systems. As an example, a multistorey building with a CFT truss is considered herein. The CFT truss in the building is expected to work as a vertically continuous shear wall and to prevent the building from collapsing in a local-storey mode. The ability of a structural system composed of a CFT truss to plastify is demonstrated based on both static and dynamic response analyses.

The observations and results from an experimental investigation of the seismic resistance of partially encased beam-columns given in the companion paper are used to assemble and verify analytical models incorporating the salient behavioural features of the test specimens. The analytical models, which employ either the commonly used bilinear kinematic hardening constitutive relationship for structural steel or the more advanced multi-surface plasticity model, are shown to achieve good agreement with the experimental results, while remaining sufficiently economical for application to larger structures. The relative performances of both material models are compared, the seismic resistance of partially encased beam-columns as identified by the experimental investigations is evaluated and the implications of the use of such structural elements in the earthquake-resistant design of multi-storey structures is discussed.

Earthquake-resisting frame systems that are designed based on current seismic provisions provide life safety performance in a large earthquake, but may have significant structural damage or residual drift due to energy dissipation in designated structural members. The damage leads to difficult or expensive repairs after a large earthquake. Therefore, development of a structural system that has both energy dissipation and self-centering properties in earthquakes is needed to improve seismic performances of buildings. This paper presents a viable solution that was validated by multiple cyclic tests of an innovative brace, called a dual-core self-centering sandwiched buckling-restrained brace (SC-SBRB). The proposed brace combines the self-centering property of a dual-core self-centering brace (DC-SCB) and the energy dissipation of a sandwiched buckling-restrained brace (SBRB) together. The dual-core SC-SBRB is essentially a DC-SCB that is positioned concentrically with a SBRB to create both the self-centering and energy dissipation properties in either tension or compression. A 7860 mm-long dual-core SC-SBRB, which uses ASTM A572 Gr. 50 steel as bracing members and ASTM A416 Grade 270 steel tendons as tensioning elements, was cyclically tested six times to validate its kinematics and cyclic performance. The test program demonstrated that the proposed dual-core SC-SBRB provides stable hysteretic responses with appreciable energy dissipation, self-centering behavior and large deformation capacity before low-cycle fatigue failure of the SBRB core.

Columns are considered to be critical members of moment-resisting structural systems. In seismically active regions, it is important to improve the ductile deformation capacity and energy dissipation capacity of columns so that the entire structure can endure severe ground motion and dissipate a considerable amount of seismic energy. Against this background, this paper presents the idea of a new transverse reinforcement configuration (TRC) for improved seismic performance of rectangular (including square) reinforced concrete (RC) columns. The novel features of the new TRC compared to conventional TRCs using rectangular hoops and cross ties mainly include the use of additional small circular spirals near the column ends (i.e., potential plastic hinge regions). Such a simple change can significantly enhance the performance of RC columns without complicating their construction. In this paper, the rationale for the new TRC together with its expected advantages is first explained. A series of axial compression tests on RC columns with the new TRC are then presented to demonstrate some of the expected advantages. The test results confirmed that the concrete is very effectively confined by the new TRC, leading to significant enhancements in both the load capacity and ductility of RC columns.

The use of concrete-filled steel tubular (CFST) columns and reinforced concrete (RC) shear wall mixed structures has attracted the interest of structural engineers. The connection between the composite columns, the shear-wall edge members and concrete wall are critical. The connection behavior at the interface of the different elements has been a major subject of this study. Therefore, ten specimens were tested to investigate the force–slip behavior between a CFST column and an RC shear wall. Also a simplified model (two models: model with nonlinear springs, simple truss model) for predicting the force–slip relation based on experimental and numerical studies was presented.

Precast segmental ultra-high performance concrete (UHPC) columns with post-tensioned (PT) tendons can effectively protect the compression toe from damage and enhance energy dissipation (ED) capacity of column compared to conventional segmental concrete columns. Extensive experiments and numerical studies have been carried out to explore the cyclic response of segmental UHPC columns in the existing literature; however, the effect of such novel columns on the seismic safety of bridge structures has not been thoroughly understood. This study aims to numerically assess the seismic fragility and seismic life-cycle loss of bridge structures supported by the precast segmental UHPC columns. For comparison, the seismic performance of the same bridge with monolithic reinforced concrete (RC) piers are also evaluated. Here, three-dimensional (3D) numerical models are generated to simulate these two bridge types. A performance-based earthquake engineering (PBEE) framework is used to evaluate and compare their seismic performance. The segmental UHPC column model is validated with the previous experimental studies. The validated model is combined into the whole bridge. Numerical results showed that the precast segmental UHPC bridge experiences similar peak acceleration and larger peak displacement in comparison to the monolithic RC bridge. The segmental UHPC bridge pier experiencing lower residual deformation can effectively reduce the damage probability and life-cycle loss of a bridge compared to the conventional monolithic RC pier. Under the design event (2475-year return period) and maximum considered event (5000-year return period), the expected losses of the segmental bridge in the lifetime were approximate 92% and 84% of that of the monolithic bridge, respectively. The segmental UHPC bridge has a noticeable economic benefit when such a bridge is constructed in regions of high seismicity.

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.

This study aims to evaluate the feasibility of using ultra-ductile Engineered Cementitous Composites (ECC) as a means to enhance the performance of beam–column connections. Nine one-third scale specimens, consisting of type 2 (ACI352R-02) interior connections at a zone of high seismicity (UBC-zone 3), were tested under reverse cyclic loading, simulating seismic excitation. The joints of these specimens were typical in geometry and main reinforcement detailing to specimens of a prototype building frame designed according to ACI318-08. The primary variables were the amount and arrangement of transverse reinforcements, and the materials within the plastic zone of the connection. The performances of a series of ECC-enhanced beam–column interior connections were compared to that of a control concrete counterpart to evaluate the benefits of using ECC in this type of application. The column load–displacement response (including the ultimate load and ultimate displacement), the (hysteresis) energy absorption capacity, and the cracking response were used as criteria in the comparison. The test results indicated that the use of ECC material in the connection plastic zone as a replacement of concrete and partial replacement of transverse (confinement) reinforcement can significantly enhance the joint shear resistance, energy absorption capacity, and cracking response, thereby, enhancing the joint seismic resistance and reducing reinforcement congestion and construction complexity.

The steel dual-core self-centering brace (SCB) is an innovative structural member that provides both energy dissipation and re-centering properties to structures, reducing the residual drift of braced structures in earthquakes. The axial deformation capacity of the brace is doubled by using two inner cores and one outer box and by serial axial deformations of two sets of parallel tensioning elements. The original dual-core SCB that used E-glass fiber tendons or T-700 carbon fiber tendons as tensioning elements exhibited good self-centering and energy dissipation up to an interstory drift of 2.5%. The new cross-anchored dual-core SCB halves the work required to apply the initial post-tensioning forces to tendons. The potential use of high-strength steel tendons as tensioning elements is studied herein, and the effects of the number of cycles on the brace behavior, energy dissipation, and durability of the steel tendon-anchorage system are also examined. First, the mechanics and cyclic behavior of the new brace are explained; a 7950 mm-long cross-anchored dual-core SCB is then tested six times. The cross-anchored dual-core SCB exhibits excellent self-centering property up to a drift of 2.5% and a maximum axial load of 1700 kN. No damage to the steel tendons, anchors or bracing members is found after three cyclic loading tests with increasing displacement amplitudes and 60 low-cycle fatigue tests. Finite element analysis further confirms the hysteretic responses and mechanics of the cross-anchored dual-core SCB in the cyclic test.

International audience; The stability analysis of a piled embankment under seismic loading is considered, with a special emphasis on the optimization of the reinforcement layout by splitting the initial group of vertical piles into two symmetrically inclined arrays of parallel inclusions. The bidirectionally-reinforced soil thus obtained is appropriately described, at the macroscopic scale, by a three-phase model, conceived as an extension of the two-phase model previously developed for unidirectionally-reinforced soils. The model is implemented in a finite element formulation and related numerical code, which is used for simulating the behavior of the piled embankment up to failure. The results of these simulations, which favourably compare with upper bound yield design calculations, clearly indicate that the seismic resistance of the embankment can be considerably increased from symmetrically inclining the piles, even without taking the potential benefits of their flexural resistance into account

In this paper a finite element methodology for the static and dynamic non-linear analysis of historical masonry structures is described and applied to a case study. A basilica-type masonry church is analysed in order to assess its structural behaviour and its seismic vulnerability with respect to the actual state of conservation. Moreover the actual efficiency of current techniques for repairing and strengthening are analyzed in order to evaluated their benefits. A quasi-static approach (the seismic coefficient method) for the evaluation of the seismic loads have been used (as indeed common in many analyses of the seismic behaviour of masonry structures). This paper addresses the concern of seismic analysis and vulnerability of a basilica-type church with a specific case study: the Farneta abbey. The comparison demand vs. capacity confirms the susceptibility of this type of buildings to extensive damage and possibly to collapse, as frequently observed. The analysis of repairing and strengthening techniques show the effectiveness of the usual structural reinforcement in term of increased seismic capacity. It is believed that the conclusions obtained with respect to the seismic assessment of masonry church can be extrapolated for the wide variety of historical basilica-type church.

In this paper, a new type of the seismic resisting members with the shape memory alloys (SMA) wire, such as brace and exposed-type column base, were proposed as a hysteretic damper for building structures. Pulsating tension loading tests were performed with constant, increasing and decreasing strain amplitude to investigate restoring force characteristics of the wire. Then, the metallo-thermomechanics model with internal variable was introduced. Using the numerical model, the restoring force characteristics of the wire under high speed loading, such as a seismic loading, were predicted. The results showed that the phenomena should be treated in the numerical model with transformation. Furthermore, these results are used to discuss the applicability and availability of the SMA wire for the seismic resisting members.

In recent years, steel plate shear walls have been used in a number of tall buildings, mainly in Japan and North America, to resist lateral forces induced by wind and earthquakes. The perceived advantages of such shear walls, in seismic resistant structures, are enhanced stiffness, strength and ductility, stable hysteretic characteristics and a large capacity for plastic energy absorption. They are also much lighter than equivalent reinforced concrete shear walls, which reduces the dynamic forces and loads on the foundations. Recent experimental and theoretical research into the structural performance of steel plate shear walls is discussed. Particular emphasis is given to the development of theoretical models for representing the hysteretic characteristics, which can be incorporated in nonlinear dynamic analyses of steel plate shear walls subjected to prescribed dynamic loading or ground motion.