Shear deformations based on variable angle truss model for concrete beams reinforced with FRP bars

Ngoc C.T. Tran,Son N. Vu 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.3

The contribution of shear deformations to total deflections in slender concrete beams is often ignored in design practices. The negligence of shear deformations could lead to the underestimation of total deflections in slender concrete beams, which will result in unsafe designs of slender concrete beams at service conditions. The shear deformations could be more critical in concrete beams reinforced with FRP bars than reinforced concrete beams because of the lower elastic modulus of FRP bars as comparing to steel ones. To address this problem, this paper attempts to determine shear deformations of slender concrete beams reinforced with FRP bars based on the variable angle truss model. The shear span of the slender concrete beams is divided into the truss units. The inclinations of struts in these truss units are first calculated by using the principle of virtual work. The shear deformations of the beams are then evaluated by summing all the shear deformations in the truss units. The calculated shear deformations are incorporated into ACI 440.1R-15’s deflection approach (2015). Comparisons are made between the analytical and available experimental results of slender concrete beams reinforced with FRP bars with respect to the deflections at 50% and 75% of the failure loads. Better results as comparing to the existing design guidelines in calculating the deflections of the slender concrete beams reinforced with FRP bars are obtained by incorporating the proposed shear deformations.

Seismic fragility assessment of self-centering RC frame structures considering maximum and residual deformations

Lu-Xi Li,Hong-Nan Li,Chao Li 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.6

Residual deformation is a crucial index that should be paid special attention in the performance-based seismic analyses of reinforced concrete (RC) structures. Owing to their superior re-centering capacity under earthquake excitations, the post-tensioned self-centering (PTSC) RC frames have been proposed and developed for engineering application during the past few decades. This paper presents a comprehensive assessment on the seismic fragility of a PTSC frame by simultaneously considering maximum and residual deformations. Bivariate limit states are defined according to the pushover analyses for maximum deformations and empirical judgments for residual deformations. Incremental Dynamic Analyses (IDA) are conducted to derive the probability of exceeding predefined limit states at specific ground motion intensities. Seismic performance of the PTSC frame is compared with that of a conventional monolithic RC frame. The results show that, taking a synthetical consideration of maximum and residual deformations, the PTSC frame surpasses the monolithic frame in resisting most damage states, but is more vulnerable to ground motions with large intensities.

Buckling of plates including effect of shear deformations: a hyperelastic formulation

Idris A. Musa 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.6

Consistent finite strain Plate constitutive relations are derived based on a hyperelastic formulation for an isotropic material. Plate equilibrium equations under finite strain are derived following a static kinematic approach. Three Euler angles and four shear angles, based on Timoshenko beam theory, represent the kinematics of the deformations in the plate cross section. The Green deformation tensor has been expressed in term of a deformation tensor associated with the deformation and stretches of an embedded plate element. Buckling formulation includes the in-plane axial deformation prior to buckling and transverse as well as in-plane shear deformations. Numerical results for a simply supported thick plate under uni-axial compression force are presented.

The stick-slip decomposition method for modeling large-deformation Coulomb frictional contact

Amaireh, Layla. K.,Haikal, Ghadir Techno-Press 2018 Coupled systems mechanics Vol.7 No.5

This paper discusses the issues associated with modeling frictional contact between solid bodies undergoing large deformations. The most common model for friction on contact interfaces in solid mechanics is the Coulomb friction model, in which two distinct responses are possible: stick and slip. Handling the transition between these two phases computationally has been a source of algorithmic instability, lack of convergence and non-unique solutions, particularly in the presence of large deformations. Most computational models for frictional contact have used penalty or updated Lagrangian approaches to enforce frictional contact conditions. These two approaches, however, present some computational challenges due to conditioning issues in penalty-type implementations and the iterative nature of the updated Lagrangian formulation, which, particularly in large simulations, may lead to relatively slow convergence. Alternatively, a plasticity-inspired implementation of frictional contact has been shown to handle the stick-slip conditions in a local, algorithmically efficient manner that substantially reduces computational cost and successfully avoids the issues of instability and lack of convergence often reported with other methods (Laursen and Simo 1993). The formulation of this approach, however, has been limited to the small deformations realm, a fact that severely limited its application to contact problems where large deformations are expected. In this paper, we present an algorithmically consistent formulation of this method that preserves its key advantages, while extending its application to the realm of large-deformation contact problems. We show that the method produces results similar to the augmented Lagrangian formulation at a reduced computational cost.

Analysis of a strip footing on a homogenous soil using element free Galerkin method

Ganaiea, Aashiq H.,Sawant, Vishwas A. Techno-Press 2015 Coupled systems mechanics Vol.4 No.4

Strip footing is an important type of shallow foundations and is commonly used beneath the walls. Analysis of shallow foundation involves the determination of stresses and deformations. Element free Galerkin method, one of the important mesh free methods, is used for the determination of stresses and deformations. Element free Galerkin method is an efficient and accurate method as compared to finite element method. The Element Free Galerkin method uses only a set of nodes and a description of model boundary is required to generate the discrete equation. Strip footing of width 2 m subjected to a loading intensity of 200 kPa is studied. The results obtained are agreeing with the values obtained using analytical solutions available in the literature. Parametric study is done and the effect of modulus of deformation, Poisson's ratio and scaling parameter on deformation and stresses are determined.

Studying Control Strategies for Dimensional Precision in Aerospace Parts Machining

Waqas Saleem,Hassan Ijaz,Muhammad Zain-ul-Abdein,Aqeel Ahmed Taimoor,Wang Yunqiao 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.1

Dimensional instability in machined aerospace parts is a complex engineering problem which is contributed by many factors. Mainly, the machining stresses developed during the part’s material cutting, cause dimensional imperfections. The complex interaction of mechanical, thermal, and metallurgical transformations makes it difficult to establish the exact reasoning of part’s desired dimensional instability. The research work presented here deals with the investigations of machining stresses and subsequent dimensional deformations in aerospace grade aluminum alloys. A commercial finite analysis code is applied to simulate the residual stresses and machining process. The stress profiles developed from the numerical simulations are compared with standard curves. The actual machined part’s deviations are measured on a CMM (coordinate measuring machine). The experimental and numerical results are found consistent with each other. This validates the control strategies adopted to simulate the machining stresses and resultant deformations.

Seismic performance of concrete frames reinforced with superelastic shape memory alloys

Youssef, M.A.,Elfeki, M.A. Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.9 No.4

Reinforced concrete (RC) framed buildings dissipate the seismic energy through yielding of the reinforcing bars. This yielding jeopardizes the serviceability of these buildings as it results in residual lateral deformations. Superelastic Shape Memory Alloys (SMAs) can recover inelastic strains by stress removal. Since SMA is a costly material, this paper defines the required locations of SMA bars in a typical RC frame to optimize its seismic performance in terms of damage scheme and seismic residual deformations. The intensities of five earthquakes causing failure to a typical RC six-storey building are defined and used to evaluate seven SMA design alternatives.

Seismic performance of concrete frames reinforced with superelastic shape memory alloys

M.A. Youssef,M.A. Elfeki 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.9 No.4

Reinforced concrete (RC) framed buildings dissipate the seismic energy through yielding of the reinforcing bars. This yielding jeopardizes the serviceability of these buildings as it results in residual lateral deformations. Superelastic Shape Memory Alloys (SMAs) can recover inelastic strains by stress removal. Since SMA is a costly material, this paper defines the required locations of SMA bars in a typical RC frame to optimize its seismic performance in terms of damage scheme and seismic residual deformations. The intensities of five earthquakes causing failure to a typical RC six-storey building are defined and used to evaluate seven SMA design alternatives.

Conceptual design of prestressed slab bridges through one-way flexural load balancing

Marcello Arici,Michele Fabio Granata 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

In this paper a study on prestressed concrete slab bridges is presented. A design philosophy based on the concept of load balancing through prestressing is proposed in order to minimize the effects of delayed deformations due to creep. Aspects related to the stress redistribution inside these bridges for timedependent phenomena are analyzed and discussed, by applying the principles of aging linear visco-elasticity. Prestressing is seen as an equivalent external load which counterbalances the permanent loads applied to the bridge, nullifying the elastic deflections due to sustained loads, and thus avoiding the related delayed deformations. An optimization of the structural behavior through the use of one-way prestressing is achieved. The determination of a convenient variable depth of slab bridges and the correspondent layout of tendons is considered as a useful means for applying the load balancing concept in actual cases of structures like long cantilevers or bridge decks. A case-study related to the slab bridges built 30 years ago at Jeddah in Saudi Arabia is presented and discussed, in order to show the effectiveness of the proposed approach to the conceptual design of prestressed concrete bridges.

Conceptual design of prestressed slab bridges through one-way flexural load balancing

Arici, Marcello,Granata, Michele Fabio Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

In this paper a study on prestressed concrete slab bridges is presented. A design philosophy based on the concept of load balancing through prestressing is proposed in order to minimize the effects of delayed deformations due to creep. Aspects related to the stress redistribution inside these bridges for time-dependent phenomena are analyzed and discussed, by applying the principles of aging linear visco-elasticity. Prestressing is seen as an equivalent external load which counterbalances the permanent loads applied to the bridge, nullifying the elastic deflections due to sustained loads, and thus avoiding the related delayed deformations. An optimization of the structural behavior through the use of one-way prestressing is achieved. The determination of a convenient variable depth of slab bridges and the correspondent layout of tendons is considered as a useful means for applying the load balancing concept in actual cases of structures like long cantilevers or bridge decks. A case-study related to the slab bridges built 30 years ago at Jeddah in Saudi Arabia is presented and discussed, in order to show the effectiveness of the proposed approach to the conceptual design of prestressed concrete bridges.