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A generalized buckling solution for anisotropic laminated composite fixed–free columns under axial compression is developed using the critical stability matrix. The axial, coupling, and flexural equivalent stiffness coefficients of the anisotropic layup are determined from the generalized constitutive relationship through the static condensation of the composite stiffness matrix. The derived formula reduces down to the Euler buckling equation for isotropic and some special laminated composites. The analytical results are verified against finite element solutions for a wide range of anisotropic laminated layups yielding high accuracy. A parametric study is conducted to examine the effects of ply orientations, element thickness, finite element type, column size, and material properties. Comparisons with numerical results reveal a very high accuracy across the entire parametric profile and a linear correlation between the percentage error and a non-dimensional condensed parameter is extracted and plotted.

Nonlinear analysis of structural members is vital to understand the behavior and the response of reinforced concrete members. Even though most design procedures concentrate on the ultimate stage of response towards the end of the post-yielding zone as the decisive design criterion, the structural members usually function at the service load levels within the post-cracking zone. Therefore, cracking is a critical aspect of concrete behavior that affects the overall response of reinforced concrete beams. The initiation and the propagation of the cracks are affected directly by the tension and shear stresses in the beam. In flexural beams, the tensile stresses dominate the crack onset and its growth. Cracks in reinforced concrete flexural beams leave non-cracked regions in between the cracked sections. In order to apply a consistent analysis strategy, the smeared crack approach averages the behavior of these different cracked sections and uncracked in between regions to generate an accurate global response of the entire beam. This study presents a numerical constitutive tensile model that captures the complete tensile response of the reinforced concrete flexural member, in terms of averaged/smeared crack response. As a second step, this model was examined against a large pool of experimental data to validate its accuracy. Overall, the main objective of this study is to develop a representative constitutive tensile model for reinforced concrete flexural members and validate its accuracy against experimental results. The full nonlinear sectional response is analytically realized, based on the assumed trilinear moment–curvature response and the assumed trilinear moment–extreme fiber compressive strain response. This is considered as the secondary outcome of the present study.

Reinforced Concrete (RC) barriers are used for different purposes in the highway inventory. An important purpose is the use of concrete barriers to act as railing that protects bridge piers against vehicular collision force (VCF). Therefore, these barriers are designed to absorb the collision energy and/or redirect the vehicle away from the parts being protected. Accurate estimation of the capacity of RC barriers during crash events is an important consideration in their design and placement. The American Association of State Highway and Transportation Officials (AASHTO) considers yield line analysis (YLA) with the V-shape failure pattern to predict the barrier capacity. AASHTO’s analysis method involves some assumptions that are intended to simplify the analysis process. Some of these assumptions have been shown to underestimate the actual barrier capacity and might disqualify many existing RC barriers from acting as intervening structures due to structural inadequacy. Many researchers have proposed alternative failure patterns and methodologies in an attempt to better predict the capacity of RC barriers. This research shows that AASHTO’s YLA, with the current V-shape failure pattern, can be improved and still predict the barrier capacity when some of the simplifying assumptions are eliminated. Also, the research presents an alternative innovative truss analogy model to predict the capacity of RC barriers. The results of the improved YLA and the proposed truss model are validated by finite element analysis (FEA) using Abaqus. The results of this research will help structural engineers in the highway industry to initially design new barriers for the intended capacity as well as estimate the capacity of existing ones.

Extensive experimental verification has shown that the use of fiber-reinforced polymer (FRP) anchors in combination with externally bonded FRP composites increases the flexural capacity of existing reinforced concrete (RC) structures. Thus, a rational prediction model is introduced in this study so that fiber splay anchors may be accurately designed for practical strengthening applications. Simplified structural mechanics principles are used to build this model for capacity prediction of a group of fiber splay anchors used for FRP flexural strengthening. Three existing test series using fiber splay anchors to secure FRP-strengthened T-beams, block-scale, and one-way slabs were used to calibrate and verify the accuracy and applicability of the present model. The present model is shown to yield very accurate predictions when compared to the results of the block-scale specimen and eight different one-way slabs. The proposed model is also compared with the predictions of a design equation adapted from the case of channel shear connectors in composite concrete-steel construction. Results show a very promising correlation. Keywords: anchor shear capacity; bent fiber splay anchor; fiber-reinforced polymer (FRP) strengthening; prediction model.

The modeling of concrete constitutive relationships in cyclic compression has attracted a lot of research attention. In this study, a normalized envelope stress-strain curve made for concrete in uniaxial compression is mathematically derived. The compression loops are formulated using a bilinear unloading path followed by a linear reloading path based on thorough observations and calibrations of available experimental data. The proposed normalized model is calibrated against a set of experimental cyclic stress-strain data. This model is shown to yield robust results by proving it successful in capturing five other independent experimental cyclic stress-strain curves. This proposed model may prove valuable for the implementation and analysis of members subjected to cyclic loading in numerical finite element analysis.

In this study, a first attempt is established to develop a rational yet simplified truss analogy approach to predict the full response of reinforced concrete deep beams. The bilinear load-deflection curve is characterized by two key points-namely, yielding and ultimate. Timoshenko's first-order shear deformation theory is invoked to linearize the strain profile by including the shear strain contribution. Based on the levels of strain in different truss members, a nonlinear analysis scheme is devised to compute the yielding and ultimate load and displacement. Comparisons with a wide range of shear span-depth ratios in tested beams are successfully made. Predictions of the response and failure modes are found to agree with experimental observations.

Due to the lack of sufficient experimental studies, the subject of fiber-reinforced polymer (FRP) anchorage has not been addressed in ACI 440.2R-17 in a quantifiable sense. This study is intended to examine the seismic performance of flexural frame members strengthened with carbon fiber-reinforced polymer (CFRP) and anchored using CFRP wrapping and CFRP splay anchors. Five full-scale reinforced concrete assemblages were tested as a control, strengthened with full wraps, strengthened with two arrangements of splay anchors, and strengthened with a combination of a splay anchor and full wrap. The seismic response is traced cyclically up to 3% drift ratios. Various response parameters were extracted from the hysteresis curves of the specimens, and are presented and discussed in this paper. The dense splay anchor specimen along with the splay anchors plus full-wrap specimen provided adequate confinement/stabilization to the plastic hinge region and yielded the best seismic performance overall. The dense splay anchorage arrangement is suggested to use when access is not available to provide full wrapping at the critical plastic hinge zone. Keywords: carbon fiber-reinforced polymer (CFRP) splay anchors; cyclic load; flexural strengthening; full wrapping; hysteresis; seismic behavior.

This study was conducted because of the lack of an existing theory to accurately predict diagonal tension cracking in shallow reinforced concrete beams. A rational approach is followed to numerically derive the shear stress profile across the depth of the section in cracked beams based on the smeared crack approach. Furthermore, the determined shear stress distribution coupled with the normal axial stress distribution are used to predict the principal stress variation across the depth and along the shear span using the standard Mohr's circle. Following a biaxial stress cracking criterion, the likely diagonal tension cracks along their orientation profile are predicted. Keywords: cracked concrete; diagonal tension cracks; shear-flexure cracks; shear stress analysis.

The prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value f cc (at zero eccentricity) to the unconfined value f c ′ (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of P – ε and M – φ response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe.

The development of stress-strain models for prestressing wires has not been performed in earlier studies. The existing modeling approaches (the PCI strand equation and the ACI equation) lack sufficient accuracy when compared to the actual response of prestressing wires. This paper improves the accuracy in predicting fps by modifying the existing \"Power Formula\" to suit the response of these wires. The newly developed \"Wire Specific Formula\" was based on using the actual stress-strain curves collected from experimental testing in an analytical modeling process. A total of 13 types of prestressing wires with 5.32 mm (0.2094 in.) diameter were tested and the wires 'geometric properties were measured. The adapted Power Formula captured the accuracy of the actual experimental or design-oriented stress-strain response very well through linear regression of key parameters, showing strong correlation. Then, the same Power equation is redeveloped for design-oriented purposes when the level of ultimate prestressing strength is specified or assumed. The present version of the Power Formula can, accordingly, be used either for specific wire type (Wire Specific Formula) or certain strength grade (Wire Strength Formula).