composites, e.g. glass fiber-reinforced polymers (GFRP), carbon fiber-reinforced polymers (CFRP) and steel-reinforced polymers (SRP), are well documented. Several researchers conducted research on the fatigue of reinforcing steel, (Ohno et al, 1978; Tilly, 1979), plain concrete (Hop, 1968; Shah and Chandra, 1970). Many studies have been conducted on the fatigue performance of reinforced concrete beams and slabs (Rezansoff et al, 1993; Petrou et al, 1994). The findings indicate that in a RC structural element subjected to cyclic loads, the failure is a result of the fatigue fracture in the steel reinforcement (Tilly, 1979). The fatigue performance of strand prestressed steel-concretecomposite girder or strengthened RC beams using externally bonded fiber-reinforced polymers (FRP) sheets has been well documented (Albrecht et al, 1995; Barnes and Mays, 1999; Shahawy and Beitelman, 1999; Papakonstantinou et al, 2001; Aidoo et al, 2004; Brena et al, 2005; Aidoo et al, 2006). Most of the research studies suggest that the addition of the FRP system results in an increase of the fatigue life of the beams. The role of the strengthening system, in terms of fatigue resistance, is to reduce the stresses on the steel reinforcing bars and thus increase the fatigue life. The fatigue relationship for steel- concretecomposite beam is generally regressed between fatigue life and stress range in steel reinforcing bar in either of following two expressions:
finite element model accounted for geometric and material nonlinearities including yielding and local buckling of the steel plates, and tensile cracking and compression plasticity of the concrete. The analysis results with experimental observations were used to explain the overall lateral load-deformation behavior of the CIS including the formation of ductile energy dissipating mechanisms in the SC walls. The authors recommended the 3D shell-solid models for evaluating the seismic (lateral load) behavior and design of similar CIS consisting of SC walls, where failure occurs in the SC walls. The simplified layered composite shell (LCS) model was recommended for evaluating the lateral stiffness and predicting the lateral load capacity of the CIS consisting of SC walls. The LCS elements have three layers (steel– concrete–steel), and each layer has several integration points through the thickness to account for speecific material behavior. The LCS model does not account for slip between the layers; therefore, the interaction between the steel and concrete portions are similar to a 3D shell-solid tie model.
Abstract—Shear wall structures have been widely used in high-rise buildings due to their good lateral resistant behavior. As a new type of shear wall structure, the double-skin steel-concretecomposite shear wall has high loading capacity, superior ductility and good crack resistant behavior. The mechanical properties of the composite walls need to be further studied. Based on the general FE package MSC.Marc(2005r2), an elaborate finite element analysis of the double-skin steel-concretecomposite shear wall is conducted to simulate the whole-process behavior of the shear wall. The load-displacement relationship is obtained, and the slippage characteristic of the steel plate-concrete interface is also intensively investigated through enforcing the spring elements at the interface. Finally, the influence of the axial compression ratio and the steel plate thickness is presented by a parametric analysis. The conclusions drawn from the analysis are that the maximum slippage of the shear wall occurs at the tension side of the wall bottom where the concrete cracks and the axial force-moment curve has a parabolic property. The relevant conclusions are useful for the routine design practice of tall buildings.
A major project to develop European design rules for SC structures in the format of the Eurocodes is currently underway. The project combines reliability analysis, testing and numerical studies and covers both the construction and in-service stages. It includes a series of large scale test programmes dealing with member behaviour, connection behaviour (T-shaped and wall to foundation connections), mechanical behaviour under moderate temperature thermal strains (of particular relevance to a loss of coolant accident (LOCA) leading to heating of the reactor building structure to 180°C), and fire tests of elements loaded axially and in bending. Data generated are complemented by nonlinear finite element analysis. Design rules will be prepared and tested through the design of a reference diesel generator building. The paper provides an overview of this four year project and highlights key results to date.
Historically, ground vehicles provide protection via monolithic metallic plates, which are not weight effi- cient. By replacing these heavy plates with multifunc- tional lightweight sandwich panels, improvements in specific strength, structural stiffness, and overall sur- vivability can be achieved. In addition, reducing the weight of military vehicles provides benefits, including increased range, manoeuvrability, fuel efficiency, and speed. While low-density sandwich panels hold signifi- cant promise for future ground vehicles, the ability to adequately join face sheets with a low-density core is important to the integration of sandwichstructures into multifunctional systems.
The investigation requires a strain-compatible section analysis addressing the stress–strain relationships of mate- rials. For this, a ﬁber section analysis program to calculate the moment–curvature relationship of the cross section of composite members was developed. In the ﬁber section analysis, the cross section of a composite member is divided into a number of ﬁber elements with inﬁnitesimal area and then internal forces of the steel section, concrete slab, and reinforcements are determined by integrating the inﬁnitesi- mal stress and moment of each ﬁber element corresponding to strain. Figure 8 shows a typical moment–curvature rela- tionship of the cross section of composite beams. For composite beams under positive bending, the ultimate limit state is deﬁned as when the compressive strain of the extreme ﬁber of concrete slab reaches the ultimate strain e cu .
‐ 18 - of structure were also proposed through these experimental and analytical studies (Wright et al., 1991b; Roberts et al., 1995). Moreover, partial composite structure and full scale experimental tests were also carried out to investigate more structural behaviors of this type of structure (Wright et al., 1991d; Wright et al., 1991e). Double skin structures used as compression members were experimentally investigated by Wright and Oduyemi (1991c). Researches on strength and design of double skin structures were continued by Roberts et al. (1995) and Roberts et al. (1996). Based on these extensive studies on double skin beams and compression members, design guidelines on double skin structures were published for design purposes (Narayanan et al., 1994; Narayanan et al., 1997). More recently, tests on double skin beams was carried out by Subedi (2003). In the double skin structure, the two external steel plates were fixed to the core concrete through the connectors. Therefore, the composite action and bending moment capacity greatly depends on the shear strength of the headed shear stud embedded in the concrete. Moreover, the overlapped headed shear studs embedded in the concrete would link the concrete cracks developed in the core and thus provide the shear resistance to the section (Shown in Fig. 2.2) . This strength greatly depends on the tensile capacity of the headed shear stud. The disadvantage of this Double skin structure is that the structure loses both bending moment capacity and shear resistance immediately once the core concrete fails.
A number of different types of finite element formulations can be applied to frame structures using composite members. Beam elements reduce the three-dimensional behavior to one-dimension, utilizing a kinematic assumption (e.g., initially plane sections remain plane) to describe the deformations of any point within the member by the deformations of cross sections along the length of the member. Three-dimensional continuum analysis allows for detailed simulation of composite members. In this type of analysis, the concrete is commonly modeled with brick elements, while the steel is modeled with brick or shell elements (Schneider 1998; Johansson and Gylltoft 2002; Varma et al. 2002; Hu et al. 2003). The interface between the two materials may be modeled with gap and friction elements. Phenomena that are simplified for analysis using beam elements may be modeled explicitly. For example, confinement of the concrete can be modeled through the use of three-dimensional constitutive relations and local buckling of the steel member can be modeled through geometric and material nonlinear behavior. Despite the improved accuracy and rationality, the computational expense prevents continuum analysis from being a viable option for analysis of complete three-dimensional frames.
The study investigated the response of steel-concretecomposite panels subjected to air-blast loading. The composite panels consist of fiber-reinforced high-strength concrete on the incident face, together with a specially configured steelsandwich as the distal layer, which functions to dissipate the imparted blast energy. The performance of the novel composite panel is compared to a conventional steelconcretesteel (SCS) panel and an ordinary reinforced concrete panel. The dynamic response of the composite panel is obtained numerically using finite element analysis adopting a simplified modeling approach. Parametric studies are carried out by varying the charge weight, the concrete type, and a number of steelsandwich core structures. Furthermore, the energy absorption capacity is found by calculating the area under the resistance-deflection curve of the proposed composite panel. The relationship between the steelsandwich core structure and the energy absorption capacity, as well as the core design and total panel deflection subjected to various blast charges, are then derived. The combination of fiber reinforced high-strength concrete and cellular steelsandwich demonstrated good potential for use as blast mitigation panel due to the high weight-to-performance ratio and the high energy absorption properties of the composite system.
While the fragility curves obtained with the SAC/FEMA method considering only material uncertainties and with the OPUS method considering the mean maximal rotation coincide, the estimation of the failure probability differ by 5 %. Indeed the integration of the fragility curve to get the seismic risk is performed in a different way in both methods. For SAC/FEMA method, the median response is interpolated linearly between peak ground levels considered in the non linear dynamic analysis and ten intermediate points are defined before performing the numerical integration of equation (25). Regarding the OPUS method, the fragility curve is first approximated by a normal cumulative density function. This normal function is then used to compute the fragility curve and the seismic risk H for 180 different peak ground levels covering the whole range of interest. Next, the numerical integration of equation (25) is carried out using these 180 points.
this area, the majority of the analytical and computational procedures used to model SC structure response can generally be subdivided into two approaches: i) idealized strut-and-tie models which have met with some success for member level design and assessment applications and ii) finite element analysis procedures which have been more commonly employed in system level SC infrastructure applications. In the case of finite element procedures, the typical approach used to model SC structures has been to employ powerful general purpose computational software packages to develop a micro-model representation of the structure or substructure under consideration. Such modelling procedures require extremely fine meshing techniques, typically involving the explicit representation of each individual shear stud and tie-bar comprising the structure, and most often employ dense distributions of solid finite elements to create some form of three-dimensional continuum. The successes of this approach have been somewhat limited as not only are such procedures computationally expensive, but many of the available commercial software packages that have been used for these investigations rely on concrete constitutive formulations based on classical solid mechanics concepts with material relations developed from test data pertaining to small-scale unreinforced and uncracked concrete elements. Thus, for computational investigations focused on the performance of large-scale SC composite wall structures, the application of simple finite element modelling procedures employing behavioural models that have been shown to adequately capture the response of cracked reinforced concrete elements under a broad range of loading conditions, should be viewed as an equally viable, if not an improved, computational approach for assessing SC structure response.
The explained 3D building model is analyzed using Equivalent Static Method and Response Spectrum Method. The building models are then analyzed by the software ETABS 2015. Different parameters such as maximum storey displacement, storey drift, base shear and fundamental time period are studied for the seismic loads. Seismic codes are unique to a particular region of country. In India, Indian standard criteria for earthquake resistant design of structures IS 1893 (Part-1): 2016 is the main code that provides outline for calculating seismic design force. For the analysis and design, following design data is considered:
Saatcioglu and Naumoski, (2005) developed the design response spectra for six functional buildings (5 , 10 and 15 storeyed) and each building was moment resisting frame buildings considered in Vancouver and Ottawa and a total of the fifteen accelerograms were used for the seismic analysis. Computer software called the DRAIN-2DX was used for the analysis. These graphs give the peak value of the load. The result they obtained was that the higher floors showed higher amplification due the earthquake load and the difference in spectra are more profound for the low rise building. The response amplification relative to the ground Volume 01, No.5, May, 2015 Page 2 excitations varied from floor to floor. The amplification was of the highest at the roof level and the amplification factor for roof is approximately 4.0 for 5 – storeyed buildings and, 3.0 for 10 storeyed buildings and 2.0 for 15-storeyed buildings. It decreases gradually going from roof level to the first storey level. Equations were developed in the project and they can also
With the effectiveness of the ultrasonication method, some researchers combined the two method of surface modification with sonication. Amongst them, Cwirzen et al. (2008) used CNTs functionalised with carboxyl groups along with sonication process to disperse CNTs in water, while polyacrylic acid polymers were used as surfactant. Using a mix containing only 0.045% volume fraction of CNTs, they observed a significant increase (as high as 50%) in compressive strength of the cement composite. Similarly, Kowald (2004) investigated the influence of surface-modified MWNTs (by oxidation nitric or sulphuric acid) on the mechanical properties of cement mortar. Dispersion of MWCNT was done by sonication of the CNTs within the mixing water for 15 minutes and then adding the superplasticizer (SP) to wrap around the dispersed CNTs and sonicated for another 2 minutes. For 0.5 wt.% of superplasticiser wrapped MWNTs (untreated) the compressive strength was increased by 8% after 7d and 12% after 14d. When 1.0 wt % of MWNTs was added the water to cement ratio was necessarily increased from 0.22 to 0.26. The samples containing the MWNTs oxidised in nitric acid showed a very bad workability which leads to a loss in the mechanical strength of the composite. The samples with the MWNTs oxidised in sulphuric acid showed no in- or decrease in their compressive strength compared to the samples without MWNTs. Their result showed contrary results to Cwirzen et al. (2008), who stated the effectiveness of combined mixing method. This suggests that the surface treatment method has not been a promising method to be further investigated, therefore, researchers focused on the use of sonication.
Zeghiche et al. (2005) tested columns under cyclic loading. For columns under cycling loads, the concrete-filled tubes showed a high level of ductility and tenacity; therefore, they were a practical solution for constructions subjected to dynamic loads such as earthquakes and wind pressure. The increase in the effective length of the columns considerably affected the column load carrying capacity with a load-decreasing rate much higher for higher concrete strength. The failure mode of these columns was overall instability. No sign of local buckling had recorded up to failure of the columns. Prakash et al. (2012) presented a paper on modified push-out tests. This paper presents, modified push-out tests conducted for the determination of shear strength and stiffness of high strength steel (HSS) studs. The HSS studs having ultimate strength of 900 MPa and yield strength of 680 MPa were used in the modified push-out specimens. Novelty of this study may be considered in highlighting the importance of confined concrete strength while designing push out specimens. It could be concluded from present experimental study that confinement of concrete near HSS stud significantly enhanced the compressive strength as well as splitting resistance of concrete. Therefore, it must be considered while designing concrete specimens for push out specimens.
For element CSRCW-1, the elastic limit of the concrete is at a force value equal to F = 8.7 kN, and a corresponding displacement of 0.23 mm. From load step number 18 it can be noticed that the concrete is cracked near the steel encased element; this can produce during the experimental test concrete splitting which can cause the buckling of the steel element at a value of the force lower that the one obtained in the numerical analysis. Therefore, a bigger attention has to be given to the confinement zone and to the shear connectors, to avoid buckling failure until bending or share failure occur in the wall. The elastic limit of the element is at a force value equal to F = 149.2 kN.
Practically all the available analyses of soil-steelstructures are based on two- dimensional modelling of the structures, i.e., assuming no load transfer in the longitudinal direction. Their analysis and stability are usually obtained assuming equilibrium between the acting dead and live loads on the conduit wall and the soil reaction. However, it has been reported that some failures of conduits have been triggered at their ends where no dead or live loads are acting at the top of the conduit. It can be appreciated that load transfer develops in the longitudinal direction in spite of the high flexibility of the conduit walls and due to its interaction with the soil. A three-dimensional analysis of soil-steelstructures is presented in this chapter in which the depth of cover above the conduit is varied from maximum at the middle part of the conduit to zero at the conduit edges.
there are very few steel bridges with a steel superstructure and steel substructure, and even fewer of this kind of bridges have been exposed to strong ground motions. However for another type of steel bridges with concrete substructures (piers), (abutments) there is significantly increasing in the population but still less than the concrete bridges. Even so, seismic performance data for these bridges is difficult to find, and especially for these bridges subjected to strong shaking (experience from recent North American earthquakes is generally for bridges in areas of low-to-moderate shaking). This data showed that steel bridge superstructures are easy to damage, even during low-to-moderate shaking, and appeared more fragile than concrete superstructures in this concern if not designed properly. The common damage such unseated girders and failures in connections, cross-frames, bearings, and expansion joints. In a few cases (during the Kobe earthquake) major carrying members have failed, triggered in some instances by the failure of components in the superstructure like the bearing for example ,  .
The specimens were extensively instrumented with a variety of measurement systems. Of particular interest was the moment-curvature relationship of the composite section along the length of the column; thus redundant measurements were taken to provide a reliable data set. The MAST system itself includes 8 load cells and LVDTs (corresponding to the 8 actuators) which are reduced to force and displacement in the 6 degrees of freedom at the top of the column. String pots were used in two orthogonal directions at several locations along the length of the columns. LVDTs were placed in set of three to measure the elongation or shortening over a certain gage length at different locations on the section in order to measure curvature. Multiple LVDTs sets were placed at the base of the column, where the curvature was expected to be the highest, and on LVDT set was placed at the top of the column. Sets of strain gages were also used in a similar manner, with sets of three being placed at locations along the length of the column. The Metris K600 DDM coordinate measurement system with approximately 40 LEDs was used to measure the displacement of the base of the column. These measurements are useful for determining the curvature as well as identifying local buckling. Additionally, video and photographic data was collected during each test.