Local stability of concrete arch bridge based on Ritz method

In order to minimize the self-weight and prevent local buckling failure of thin-walled box concrete arch bridges at the same time, the limit values of width-thickness ratios are deduced based on Ritz method and equivalent strut theory of arch bridge. A new method of determining sectional forms based on the limit values of width-thickness ratios is put forward. Based on Mupeng bridge, the theoretical results are verified by finite element software ANSYS. Results show that the limits of width-thickness ratios are related to concrete grade, equivalent calculation length and radius of gyration, the allowable minimum thickness of Mupeng bridge is 15 cm to avoid local buckling. The limit values of width-thickness ratios deduced in this paper are reasonable and this new method of determining sectional forms is simple and rational to apply in engineering. A scientific engineering calculation method on arch ring design is put forward and it can provide a theoretical basis for the design of thin-walled box concrete arch bridges constructed by cantilever pouring.

Comparison of Modelling Strategies of R.C Walls for Seismic Analysis

Reinforced concrete walls are being widely adopted as lateral load resisting systems for high rise structures. The current practice among design engineers for modelling of such walls is by idealizing the same as ‘wide’ columns, which is uncertain from safety as well as economy point of view. The most efficient modelling strategy of RC walls involves use of shell elements. Such an approach can be computationally much intensive, especially from a seismic analysis perspective. The present study utilizes an equivalent strut approach for modelling RC walls. The modelling strategy is demonstrated on a G + 15 storey residential apartment located in Calicut city. The proposed methodology will be compared with the traditional ‘wide’ column method as well as the one with shell element discretization. Comparison of modal properties such as frequencies and vibration modes from the various models are initially made to assess the model accuracy. Various seismic analyses viz. Equivalent static approach, Response spectrum approach and the assessment the storey shear, inter storey drifts as well as computation times using various models were performed using time history analysis. From preliminary results, it is understood that the modelling strategy could serve as an efficient alternative to more robust and computationally demanding scheme involving use of shell elements.

Investigation on Seismic Behaviour of Masonry Infilled Self-Centring-Beam Moment-Frames using New Infill Material Model

This paper conducted experimental and numerical investigations on seismic behaviour of masonry infilled self-centring-beam moment-frames (SCB-MFs). First, an efficient hysteretic material model was proposed for use with the equivalent strut modelling approach of infill walls. This model was defined by backbone parameters and hysteretic parameters and implemented in the OpenSees platform to facilitate its application. Then, an approximately half-scale test of infilled SCB-MFs was carried out. The test observations and load-carrying capacities of masonry walls in the specimen were reported and analysed. The experimental hysteresis was reproduced by the numerical model using the proposed infill material. Finally, structural analyses were conducted for 3-, 6-, 9-, and 12-storey infilled SCB-MFs based on the calibrated computational model. Comparisons of the hysteretic behaviours obtained by the simulation with experimental results showed that the proposed infill material could capture the strength, stiffness, and energy dissipation during reloading, along with the residual drift during unloading. The nonlinear dynamic analyses also validated the feasibility of using the proposed model to simulate the dynamic responses of infilled SCB-MFs.

Seismic analysis of reinforced concrete buildings with participating masonry infills

ABSTRACT In this paper, seismic analyses are performed of a reinforced concrete frame building with participating masonry walls are carried out. The spectral method of the Brazilian code – ABNT 15421:2006 – was used to obtain the lateral seismic loads. The equivalent diagonal-strut model was employed to simulate the axial stiffness of the masonry walls in the frames, according to different formulations founded in literature. The main purpose is to evaluate the differences implemented by the different formulations for the equivalent strut on the seismic response. This paper also aims at comparing results obtained when the masonry stiffness is not considered under seismic loads. The results obtained are analyzed with the purpose of providing contributions for structural engineers in the design of framed structure buildings with participating masonry walls subjected to seismic loads.

Numerical Analysis of Masonry Assemblages through Simplified Micro-Modeling

Recently, research focused on preventing the aging of masonry structures, and minimization of damage caused by earthquakes to these structures has gained significant attention. To improve the performance of these structures, an appropriate method is required for their performance evaluation. Generally, the equivalent strut model is employed for the performance evaluation of a masonry wall. However, this method is known to have limitations in implementing reinforced masonry and in reflecting the actual reinforcement effect. Appropriate evaluation techniques should be developed to implement the performance improvement methods developed in the future. Therefore, in this study, analysis methods were developed considering the nonlinear static analysis method for masonry elements. In addition, using these methods, the analysis considering the various reinforced thicknesses and shapes was performed, and the appropriate reinforcement methods were presented for these structures.

SEISMIC DESIGN OF MASONRY-INFILLED FRAMES: A REVIEW OF CODIFIED APPROACHES

This paper reviews the approach of eleven national codes on the analysis and design of masonry-infilled frames. It is shown that, in general, codes can be divided into two groups. The first group isolates the masonry and frame members by providing gaps to minimize the interaction between them. This method ensures that the complexities involved in analyzing the structure is avoided. However, the width of the gaps recommended is different for each of the codes. The second group takes advantage of the presence of high stiffness and strength masonry infill. In this technique, an equivalent-strut modeling strategy is mostly recommended. It is shown that the strut model suggested in each of the codes is different. An attempt to obtain a generic model for masonry-infilled frame failed largely due to the existence of many behavior-influencing parameters. Finally, it is suggested to have a paradigm shift in the modeling strategy where the masonry-infilled frames are classified into different categories and a model is suggested for each of them.