Embedded carbon fiber-reinforced polymer rod in reinforced concrete frame and ultra-high-performance concrete frame joints

Beam–column joints play an important role in providing lateral stiffness and integrity of frames during dynamic loading such as earthquake. In the high humidity areas, during functioning of the building cracks occur, which leads to the corrosion of the reinforcement due to the environmental exposures. Therefore, one of the main failures mechanism of building during an earthquake is caused by easily yielding of corroded steel reinforcement, which leads to reduce functionality of the frame joints in transferring the loads. This study proposed a new design to reinforce the beam-column joints with embedded carbon fiber-reinforced polymer (CFRP) rods, due to their extremely high strength and stiffness, along with the fact that they will not rust or corrode and very light weight. CFRP rods are used in reinforced concrete (RC) frame and ultra-high-performance concrete (UHPC) frame subjected to dynamic load. The prototype of the proposed design is constructed as frame with conventional concrete and frame with UHPC material to conduct experiments Test as well as numerical analysis to evaluate the performance of the proposed joints under dynamic loads. The results showed improvement in the performance of the frames reinforced with embedded CFRP in joints in terms of lateral load resistance capacity, ductility behaviour, overall stiffness, and failure mechanism.

Numerical investigation of a new structural configuration of a concrete barrier wall under the effect of blast loads

In this study, a non-linear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D, which is an extensive code dealing with explosion problems. A high explosive material (comp-B) is blasted against several concrete wall barriers. The model was first validated using referenced experimental tests and has shown good results. Several numerical models were carried out to study the effect of changing the shape of wall barrier from flat to convex curve and concave curve, and also investigated the effect of changing the angle of curvature. The results showed that changing the shape of a wall barrier from flat to convex curve has the best performance in mitigating the effect of blast waves. It is also concluded that convex walls with 60° angle of curvature have the best performance compared to other barrier walls.

Formulation of a new finite element based on assumed strains for membrane structures

In this paper, a new triangular membrane finite element with in-plane drilling rotation has been developed using the strain-based approach for static and free vibration analyses. The proposed element, having three degrees of freedom at each of the three corner nodes, is based on assumed strain functions satisfying both compatibility and equilibrium equations. Numerical investigations have been conducted using several tests, including static and free vibration problems, and the obtained results are compared with analytical and numerical available solutions. It is found that efficient convergence characteristics and accurate results can be achieved using the developed element.

Investigation on cold-formed steel built-up new innovative hat-shaped closed section under bending

The objective of this study is to make the experimental and finite element simulations of buckling behaviour of cold-formed steel (CFS) built-up hat-shaped closed section under simply supported end condition subjected to two-point loading. Numerical simulation is carried out using the software ABAQUS. The test result is compared with numerical results and good correlation is achieved. Next, for validation, a series of parametric studies are carried out using the validated numerical model, such as the effect of length, depth, width, thickness and angle of the inclined element. The local buckling and the interaction of local and flexural buckling are studied. To end with, a design equation is proposed in accordance with the direct strength method specification for CFS structure.

Structural assessment of remodelled shells of Heinz Isler

Heinz Isler as the most famous contemporary shell designer has widely employed physical pre-modelling techniques for construction of many concrete shell structures. Through the physical approach to optimal form finding, Isler accomplished shell structures with robust performance. It would be interesting and beneficial to re-assess Isler’s shells, hence, this article attempts to study the structural performance of eight notable shells of Isler. Through reverse engineering and by the assistance of Rhino, MATLAB and Grasshopper, the precise geometry of Isler’s selected shells were modelled for the finite element analysis under their self-weight. The structural analysis was performed, with the parallel use of finite element software SAP2000 and Abaqus. The identical results of the two packages, further confirmed the accuracy of the analysis. The essential properties of various forms of the shells and their differences in behaviour were pinpointed and discussed within the calculations and the results were compared with the data of the genuine published references on Isler’s works. The internal forces, the amount of von Mises stresses, support reactions and the buckling loads of the shells are explored. The analyses revealed that, despite of their major membrane action, all the shells had negligible amount of bending moments, especially near the supports. However, in general, all the shells exhibited an appropriate performance under the applied actions. But, at the same time, they exhibited different buckling behaviour as a probable source of instability in them.

Static analysis of tall buildings based on Timoshenko beam theory

In this paper, the continuum model, which is known as Kwan model, has been presented for the analysis of tall buildings that have been as an appropriate approximation of the overall behavior of the structure. Tall building was modeled as a cantilever beam and analyzed with the assumption of flexural behavior based on Euler–Bernoulli Beam Theory, then the displacement of floors was calculated. o consider the shear lag effects in the overall displacement of the structure, Timoshenko’s beam model has been considered and related relations were extracted. The lateral displacement formulas obtained and calculated for the framed tube system modeled by Kwan’s method. To verify the results, numerical models were created in software (ETABS) and statically were analyzed for lateral loading. Finally the results were compared with those obtained by computer analysis and the corresponding diagrams were presented. At the end, the shape factor formula has been developed to improve the results of the Timoshenko’s theory.

Influence of ground motion duration on ductility demands of reinforced concrete structures

This article investigates the level of influence that strong motion duration may have on the inelastic demand of reinforced concrete structures. Sets of short-duration spectrally equivalent records are generated using as target the response spectrum of an actual long-duration record. The sets of short-duration records are applied to carefully calibrated numerical models of the structures along with the target long-duration records. The input motions are applied in an incremental dynamic analysis fashion, so that the duration effect at different levels of inelastic demand can be investigated. It was found that long-duration records tend to impose larger inelastic demands. However, such influence is difficult to quantify, as it was found to depend on the dynamic properties of the structure, the strength, and stiffness degrading characteristics, the approach used to generate the numerical model and the seismic scenario (target spectrum). While for some scenarios, the dominance of the long record was evident; in other scenarios, the set of short records clearly imposed larger demands than the long record. The detrimental effect of large strong motion durations was mainly observed in relatively rigid structures and poorly detailed flexible structures. The modeling approach was found to play an important role in the perceived effect of duration, with the lumped plasticity multilinear hysteretic models suggesting that the demands from the long records can be up to twice the inferred from distributed plasticity fiber models.

Numerical analysis and experimental testing of ultra-high performance fibre reinforced concrete keyed dry and epoxy joints in precast segmental bridge girders

Although ultra-high performance fiber reinforced concrete (UHPFRC) has been used recently as a sustainable construction technique for many precast segmental bridges (PSBs), no exhaustive numerical and experimental studies exist to assess the shear capacity and failure pattern of the joints in these bridges. Hence, to accurately investigate the shear behavior of the joints in UHPFRC precast segmental bridges, a numerical analysis model based on finite-element code was established in this study. Concrete damaged plasticity model was used to analyze the UHPFRC joint models by considering all the geometries, boundaries, interactions and constraints. In this paper, the numerical model was calibrated by two full-scale UHPFRC keyed dry and epoxy joints under confining pressure effect. The excellent agreement between the numerical results and experimental data demonstrated the reliability of the proposed numerical model. The validated numerical model was then utilized to investigate the parameters affecting shear behaviour of the joints in PSBs. For this purpose, 12 FE models were analyzed under different variable parameters namely, number of shear keys, confining stress, and types of joints (dry or epoxy). Furthermore, the numerical results were also compared with the five existing shear design provision models available in literature in terms of ultimate shear capacity.

Short-term deflection of RC beams using a discrete rotation approach

Quantifying the deflection of RC beams has been performed traditionally using full-interaction moment–curvature methods without considering the slip that takes place between the reinforcement and the surrounding concrete. This was commonly carried out by deriving empirically based flexural rigidities and using elastic deflection equations to predict the deformation of RC structures. However, as flexural and flexural/shear cracks form in RC beams with increase in applied load, the reinforcement steel begins to slip against the surrounding concrete surface causing the cracks to widen and ultimately increasing the deflection at mid-span. Current design rules cannot cope directly with the deformation induced by the widening of cracks. Because of that, this study focused on predicting the non-time dependent deflection of RC beams at both service and ultimate limit states using a mechanics-based discrete rotation approach. The mechanics-based solution was compared with experimental test results and well-established code methods to which a good agreement between the results was observed. The method presented accounts for the non-linear behavior of the concrete in compression, the partial-interaction behavior of the reinforcement, and the deflection was computed while considering the rotation of discrete cracks. Due to its generic nature, the method presented does not require any calibration with experimental findings on the member level, which makes it appropriate to quantify the deflection or RC structures with different types of concrete and novel reinforcement material.

Numerical comparison on the efficiency of conventional and hybrid buckling-restrained braces for seismic protection of short-to-mid-rise steel buildings

Buckling-restrained brace (BRB) is a specific kind of bracing system which has an acceptable energy dissipation behavior in a way that would not be buckled in compression forces. However, considerable residual deformations are noticed in strong ground motions as a result of the low post-yield stiffness of the BRBs. The seismic performance of a modern lateral load resisting system, which is called the hybrid BRB, and its conventional counterpart are assessed and compared in this paper. Multiple plates with different stress–strain behavior are used in the core of this new innovative system, and this is its difference with the existent BRBs. Nonlinear static and incremental dynamic analyses are carried out for three building frames with different structural heights, which use conventional and hybrid BRB systems. To carry out response history analyses, the FEMA P695 far-field earthquake record set was adopted in different hazard levels. The hybrid BRBs are shown to have superior seismic performance in comparison with the conventional systems based on the response modification factor and the damage measures including residual displacements and inter-story drift ratios.