A Simplified Solution of the Torsional Rigidity of the Composite Beams by Using FEMSaygun, A.; Omurtag, M. H.; Orakdogen, E.; Girgin, K.; Kucukarslan, S.; Darilmaz, K.
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417726
In this paper, the torsional rigidity of the composite sections formed by different materials is obtained by using a finite element procedure. In the derivation of the differential equation, the Saint-Venant's stress function was used. The obtained partial differential equation was discretized by finite elements to get the potentials in the nodal points. After the calculations of the unknown potentials on the composite cross-section, the torsional rigidity is calculated by integrating the potentials on the solution domain. To test the validity of the proposed algorithm, the available analytical and numerical results from the previous studies were studied. It was seen that this new algorithm is efficient and simpler than the previous ones.
Finite Element Study of Shear Behavior of Spandrel Ledges and Comparison with PCI Shear Design ProvisionsHassan, Tarek K.
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417690
Punching shear failure of spandrel ledges has been observed by many researchers and heightened concerns have been raised questioning the safety level of the PCI shear design provisions for beam ledges. This paper presents non-linear finite element analyses conducted to model the behavior of prestressed L-shaped spandrel beams. Special emphasis was given to the behavior of the ledge at the end regions of the spandrel, where punching shear controls the design. The accuracy of the finite element model is demonstrated by comparing the predicted behavior to the results of one major test by another researcher. The influence of different parameters included in the PCI shear design provisions for beam ledges is discussed. The analysis is extended to illustrate the effect of other parameters including the prestressing level, hanger reinforcement and the amount of debonded strands at the end regions of the spandrel beam. Results of the analyses showed that the PCI shear design provisions for spandrel ledges are dangerously unconservative. The provisions do not account for key parameters, which affect the punching shear behavior.
Post-Tensioned Interior Precast Wide Beam—Column Connections Subjected to Lateral LoadingMoon, J. H.; Choi, Y. C.; Lim, J. H.; Lee, L. H.; Kwon, K. H.; Kim, K. S.
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417654
The post-tensioned precast concrete system (PPS) developed in this study consists of U-shaped precast wide beams and concrete columns, where the continuity of wide beam-column joint is provided with the cast-in-place concrete on the U-shaped precast wide beam and the post-tensioning to the beam after casting of slab. The PPS structure can overcome the defect of discontinuity in the connections of precast members using cast-in-place concrete on precast members, and complement the low sectional efficiency of wide beam by applying the post-tensioning. In this study, an experimental investigation was performed with three half-scale specimens of interior connection fabricated employing PPS structure. Specifically, this paper presents the response of PPS interior beam-column joint subjected to cyclic lateral loading and evaluates the relevance of the beam-to-column width ratio criteria specified in ACI 318–05. The test results indicate that the PPS specimens can resist properly seismic loads maintaining overall structural integrity.
Semi-Active Stiffness Dampers for Seismic Control of StructuresKori, Jagadish G.; Jangid, R. S.
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417744
This paper describes the application of semi-active variable stiffness damper (SAVSD) for response control of the seismically excited structure. The SAVSD consists of hydraulic damper connected in the form of bracing in a selected story of frame structure. The SAVSD changes its stiffness depending upon the structural response and accordingly adds the control forces in the structural system. In this paper, the comparative study and the performance of SAVSD under different ratios of damper stiffness to structural story stiffness is presented. The specific objective of this study is to evaluate the optimum value of damper stiffness ratio and its importance in structural response reduction. The optimum stiffness ratio is investigated for the structure subjected to four different types of earthquake ground motions. Here, the switching control law and newly proposed modified switching control law are used and the results are compared with uncontrolled and passive control cases. A numerical study is performed on five and ten-story shear building with different configurations of damper placement. The numerically evaluated optimum parametric values are considered for the analysis of the optimum damper placement in the structure. It is revealed that, the proposed modified switching control law is very effective in reducing the story displacements and inter-story drifts without increasing the top floor accelerations. The numerical results of various analyses indicate that SAVSD shows better performance over the passive dampers in reducing the structural responses.
Pultruded FRP Plank as Formwork and Reinforcement for Concrete MembersBank, Lawrence C.; Oliva, Michael G.; Bae, Han-Ug; Barker, Jeffrey W.; Yoo, Seung-Woon
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417681
A feasibility study in which the use of a commercially produced pultruded fiber reinforced polymer (FRP) plank for both permanent formwork and secondary or primary tensile reinforcement of a concrete structural member is described in this paper. To achieve satisfactory bond at the interface between the smooth surface of the FRP plank and the concrete, two kinds of aggregate, gravel and sand, were epoxy bonded to the planks. Concrete beams using the aggregate-coated FRP planks were fabricated and tested. Satisfactory bond between the FRP plank and the concrete was developed which was evidenced by numerous well-distributed flexural cracks, and ultimate capacities of the aggregate coated FRP plank specimens greater than the steel rebar reinforced control specimen. ACI 440 equations were found to provide good predictions of the flexural strengths but poor predictions of the shear strengths of the FRP plank reinforced beams. ACI 318 equations, however, provided good shear strength predictions.
Axial Load Behavior of Rectangular CFT Stub Columns with Binding BarsCai, Jian; Long, Yue-Ling
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417663
This paper presents an experimental study on the axial load behaviour of rectangular concrete-filled steel tubular (R-CFT) stub columns with binding bars. Eight specimens were concentrically loaded in compression to failure in order to investigate the effects of the binding bars, depth-to-wall thickness ratio and cross-sectional aspect ratio on the ultimate strength and ductility of the composite columns. Experimental results indicate that the binding bars increase the confinement of the concrete core and delay local buckling of the tube. The results also show that R-CFT columns with binding bars have better ductility than those without binding bars. A model is proposed to predict the ultimate strength of the specimens. A comparison of the ultimate strengths between tests and design codes shows that the proposed model gives reasonable predictions of the ultimate strength of rectangular CFT stub columns with binding bars while the codes EC4 (1996), AIJ (1997) and GJB (2001) conservatively estimate the ultimate strength by 17.6%, 22.9% and 9.7% respectively.
Flat Slabs at Slab-Column Connection: Nonlinear Finite Element Modelling and Punching Shear Capacity Design CriterionXiao, R. Y.; Chin, C. S.
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417717
Nonlinear finite element analysis has become very useful in modelling complicated structural systems and their behaviour. In this paper, an attempt has been made to utilize a tension softening material (TSM) model to simulate the full pre-cracking and post-cracking response of fibre reinforced concrete flat slabs at slab-column connections by finite element analysis. Validation of the developed numerical model was carried out by means of comparisons with test results. In addition, a universal analytical model has been proposed to predict the ultimate punching shear strength of slab-column connections. Compared with the relevant design codes (BS 8110, ACI 318–05, EC 2 1991, EC 2 2004/CEB-FIP MC90 and JSCE 1986), the model proposed herein has been shown to be accurate, with low coefficient of variation. Furthermore, a distinctive failure mode indicator has also been derived.
Effect of a Dent of Different Sizes and Angles of Inclination on Buckling Strength of a Short Stainless Steel Cylindrical Shell Subjected to Uniform Axial CompressionPrabu, B.; Bujjibabu, N.; Saravanan, S.; Venkatraman, A.
2007 Advances in Structural Engineering
doi: 10.1260/136943307782417735
Generally, thin cylindrical shells are susceptible for geometrical imperfections like non-circularity, non-cylindricity, dents, swellings etc. All these geometrical imperfections decrease the static buckling strength of thin cylindrical shells, but in this paper only effect of a dent on strength of a short (L / D ∼1 and R/t = 280) stainless steel cylindrical shell is considered for analysis. The dent is modeled on the FE surface of perfect cylindrical shell for different angles of inclination and sizes at half the height of cylindrical shell. The cylindrical shells with a dent are analyzed using non-linear static buckling analysis. From the results it is found that in case of shorter dents, size and angle of inclination dents do not have much effect on static buckling strength of thin cylindrical shells, where as in the case of long dents, size and angle of inclination of dents have significant effect. But both short and long dents reduce the static buckling strength drastically.