A Tool for the Rapid Seismic Assessment of Historic Masonry Structures Based on Limit Analysis Optimisation and Rocking Dynamics

This paper presents a user-friendly, CAD-interfaced methodology for the rapid seismic assessment of historic masonry structures. The proposed multi-level procedure consists of a two-step analysis that combines upper bound limit analysis with non-linear dynamic (rocking) analysis to solve for seismic collapse in a computationally-efficient manner. In the first step, the failure mechanisms are defined by means of parameterization of the failure surfaces. Hence, the upper bound limit theorem of the limit analysis, coupled with a heuristic solver, is subsequently adopted to search for the load multiplier’s minimum value and the macro-block geometry. In the second step, the kinematic constants defining the rocking equation of motion are automatically computed for the refined macro-block model, which can be solved for representative time-histories. The proposed methodology has been entirely integrated in the user-friendly visual programming environment offered by Rhinoceros3D + Grasshopper, allowing it to be used by students, researchers and practicing structural engineers. Unlike time-consuming advanced methods of analysis, the proposed method allows users to perform a seismic assessment of masonry buildings in a rapid and computationally-efficient manner. Such an approach is particularly useful for territorial scale vulnerability analysis (e.g., for risk assessment and mitigation historic city centres) or as post-seismic event response (when the safety and stability of a large number of buildings need to be assessed with limited resources). The capabilities of the tool are demonstrated by comparing its predictions with those arising from the literature as well as from code-based assessment methods for three case studies.

New Hardware Static and Reconfigurable Architectures for Video Watermarking System

The watermarking technique is an active subject in current research used as a solution for copyright protection in multimedia documents. In this paper, we propose the first hardware invisible robust video watermarking application based on motion estimation. Since the designers of this application face many challenges, two types of architecture are performed: static and dynamic/partial reconfigurable architecture. The proposed architecture is adapted to HEVC encoded video. Two protection techniques are linked up: the digital watermarking to insert a watermark in the video, and the scrambling technique for overall video protection. The watermark embedding is treated in the horizontal and vertical components of even motion vectors. Eventually, the entire vectors are scrambled. The used watermark is a binary sequence where only one bit is inserted into the horizontal and the vertical components of motion vectors. The recommended architecture applies for slow and fast video sequence, where we use a motion estimator reconfigured according to the macro-block video movement. We also utilize a pipeline structure and a clock gating module to increase computing power and reduce power consumption. Experimental results show that the suggested static and dynamic/partial reconfigurable architecture guarantees material efficiency and superior performance in terms of frequency and power consumption.

Nonlinear Static and Dynamic Analysis of Rocking Masonry Corners Using Rigid Macro-Block Modeling

The corner failure is one of the most typical local mechanisms in masonry buildings vulnerable to earthquakes. The seismic assessment of this mechanism is poorly studied in the literature and in this paper it is addressed by means of both nonlinear static and dynamic analyses of rocking rigid blocks. The static approach is based on the displacement-based method and is aimed at predicting the onset of the 3D failure mechanism and its evolution through incremental kinematic analysis. This approach also considers the presence of a thrusting roof and the stabilizing contribution of frictional resistances exerted within interlocked walls. The capacity in terms of both forces and displacements is compared with the seismic demand through the construction of acceleration–displacement response spectra, with some originality. The nonlinear dynamic approach is based on the seminal Housner’s work on rocking rigid blocks and considers the influence of transverse walls, roof overloads and outward thrust, all included in an updated equation of one-sided motion. In particular, the process of defining an equivalent prismatic block, representative of the original corner geometry, is presented to convert the 3D dynamic problem into a 2D rocking motion. The wide suitability and advantage of such modeling approaches to assess the seismic response of rocking masonry structures with reference to specific limit states are demonstrated through a real case study, i.e. the collapse of a corner in a masonry school building during the 2016–2017 Central Italy seismic sequence. The compared results provide a good agreement of predictions in terms of both onset and overturning conditions, for which the static model appears to be more conservative than the dynamic one.

Improved Logarithmic Search for Efficient Video Compression

For efficient video compression, the BMAs should be designed and implemented in such a way that that the Motion Estimation takes very less time and will have lesser complexity. In this paper, two new algorithms namely Improved Logarithmic Search (ILS) and Zero motion predicted ILS (ZMILS) are proposed which are based on the basic idea of Three Steps Search (TSS) algorithm. In these BMA, the search pattern of proposed algorithms changes the efficiency both in terms of complications required for each macro block (MB) and quality of the compensated images. We improved the TSS and NTSS by changing the searching pattern of locations in reference frame and by adding no movement early prediction case with these algorithms we further reduced the computations. The computations required by the new developed algorithm are lesser per macro block and even 50% of few existing techniques while retaining the quality of the reconstructed image

Modified Boundary Matching algorithm for Error detection and Error Concealment for Video Communication

As the demand of video transmission over communication network has grown rapidly, the data compression and error correction in video processing have shown significant improvement day by day. When the error occurs in a single frame, the visual quality of the subsequent frames gets degraded due to error propagation. Thus, the error control techniques are required for the recovery. Concealment of error at the receiver (decoder) side feats the spatial and temporal characteristics of the frame. Without the requirement of the extra bandwidth and retransmission delay, it enhances the quality of the reconstructed video. However, the output of the error concealment may get affected if the error located before is misleading. Thus error detection also plays an important role while reconstructing the video. However, the output of the error concealment may get affected if the error located before is misleading. This paper proposes error detection and concealment approach for the recovery of lost Macro Block (MB) in video. The spatio-temporal techniques has been used for the error detection followed by the MB type decision applied for classifying the damaged macro block .For the concealment method a new method i.e. Modified Spatio-Temporal Boundary Matching Algorithm (MSTBMA) has been proposed. The proposed work is compared with various existing method for spatial and temporal error concealment. The comparison has been done for various types of error such as block error (single, multiple), burst error and random error generated by the software. Performance is improves in terms of PSNR and visual quality by considering the type of lost MB.