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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.

Intense research works on twin-cell box-girder bridges are limited when compared to single-cell box-girder bridges and hence, not many sources are available to study the simultaneous effect of bending and torsion in them. The estimation of ultimate load in a twin-cell box-girder bridge under different modes of failure using the two existing simplified methods--namely, the space truss analogy and collapse mechanism--demands more research attention. The primary objective of this paper is to develop simplified equations for twin-cell box-girder bridges using the principles of collapse mechanism. The second main objective is to check the suitability of using space truss analogy and collapse mechanism in different modes of failure. Experimental work for studying the effects of various structural actions due to an eccentric loading on a simply supported twin-cell concrete box-girder bridge is conducted and numerical analyses are presented to understand the effect of load positions and reinforcement ratios in the failure modes. Keywords: collapse mechanism; failure modes; space truss analogy; twin-cell box-girder bridges.

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.

Numerous methods for calculating shear strengths of structural walls are available. However, due to the complexity of wall behaviors and possible loading combinations that they may be subjected to, it is quite challenging to derive a method that is reasonably simple but can accommodate various influencing parameters in order to acquire more accurate predictions of wall shear strengths. The authors had earlier tested a series of very-high-strength concrete wall specimens ([f'.sub.c] = 100 MPa [14,500 psi]) to investigate the influence on shear strength of several parameters, such as: height-to-length ratios, shear (web) reinforcement ratios in the vertical and horizontal directions, as well as the presence of flanges (boundary elements). The conclusions of the authors' experimental study in the light of other research results reported by other researchers will be summarized herein and will be used as a guide for deriving a proposed truss model. The proposed model is based on modern truss analogy principles (softened truss model, compression field theory) and it has been shown by comparing it with experimental results to be accurate and stable. The design and analysis procedure based on the proposed truss model will also represent an improvement over existing ACI and Eurocode design procedures. Keywords: building codes; high-strength concrete; horizontal reinforcement; shear reinforcement; shear strength; structural walls; truss analogy; vertical reinforcement.

B-Regions are parts of the structure in which Bernoulli's principle of straight-line strain is used. D-Regions are parts of the structure with a complicated variation in strain. In essence, D-Regions contain the parts of structure which are near to the concentrated forces or steep changes in geometry which are so-called geometrical discontinuities or static discontinuities. Strut-and-Tie Model (STM) is one of the best models to analyse the D-regions. Nevertheless, according to the existing literature, there are still some challenges about STM which are addressed in this paper. STM and its details are investigated to show its common challenges presents some recommendations to overcome these challenges. According to this review, the major challenges in STM are related to the strut effectiveness factor, static uncertainties of STM, strain compatibility, and anchorage requirements in STM. The scope of this research is confined to the two dimensional STM.

Design codes provide the necessary tools to check the torsional strength of reinforced concrete (RC) members. However, some researchers have pointed out that code equations still need improvement. This study presents a review and a comparative analysis of the calculation procedures to predict the torsional strength of RC beams from some reference design codes, namely the Russian, American, European, and Canadian codes for RC structures. The reliability and accuracy of the normative torsional strengths are checked against experimental results from a broad database incorporating 202 RC rectangular beams tested under pure torsion and collected from the literature. The results show that both the readability and accuracy of the codes’ equations should be improved. Based on a correlation study between the experimental torsional strengths, and geometrical and mechanical properties of the beams, refined yet simple equations are proposed to predict torsional strength. It is demonstrated that the proposed formulation is characterized by a significant improvement over the reference design codes. The efficiency of the proposed formulae is also assessed against another equation earlier proposed in the literature, and an improvement is noted as well. From the results, it can be concluded that the proposed equations in this study can contribute to a more accurate and economical design for practice.