K. Muthumani

DYNAMIC RESPONSE EVALUATION OF A FRAMED TYPE TURBO-GENERATOR FOUNDATION INCORPORATING DYNAMIC MODULUS AND OPERATING SPEED VARIATIONS

Framed type foundation structures supporting turbo-generator machinery in a power plant have stringent vibration limits to ensure proper functioning of turbine generators without any breakdown. Current dynamic analysis methodology for such dynamically sensitive structures involves modal synthesis considering a single value of operating speed for the machinery and a uniform dynamic modulus for the frame material, which cannot be realized in site conditions. Such variations in the dynamic modulus across the whole structure and running speed of the machinery during normal operation have a profound impact on its dynamic performance which may result in alarmingly increasing amplitudes leading to subsequent breakdown of the machinery. A new methodology is outlined that combines the effects of the two variations by way of considering an enhanced range of speeds on either side of the operating speed for the modal synthesis process. This study shows the effects of variations in the dynamic modulus and operating speed on the peak dynamic response of a typical framed turbo-generator foundation structure. The modal synthesis process adopted in the study includes the significant modes in the sub-resonant range and a band of modes around the operating speed to obtain the peak response of the framed structure.

Studies on Nonlinear Behavior of Shear Walls of Medium Aspect Ratio under Monotonic and Cyclic Loading

AbstractStructures designed according to performance-based seismic design (PBSD) are required to satisfy the target performance. PBSD requires extensive research for capacity evaluation and development of reliable nonlinear models. Shear walls are the ideal choice to resist lateral loads in multistoried RC buildings. They provide large strength and stiffness to buildings in the direction of their orientation (in-plan), which significantly reduces lateral sway of the building. Experimental studies on nonlinear behavior of shear walls of medium aspect ratios are limited. Nonlinear performance of medium aspect ratio shear wall specimens are studied on three identical shear wall specimens through application of monotonic and cyclic loading. In order to study the effect of axial load on the flexural behavior and ductility of shear wall, a parametric study is conducted using a layer-based approach, which is used to generate the analytical pushover curve for the shear wall and validated with the experimentally e...

Seismic Response Measurement of an Under‐Water Model Through High Speed Camera and Feature Tracking

Shake table testing is a viable validation tool for bench-marking the analytically computed seismic response of under-water structural models with fluid–structure interaction effects. Conventional displacement sensors like LVDTs (linearly variable differential transformer) cannot be used for under-water response measurements as they require a stationary platform near the measurement point as a reference. This rather limiting application of LVDTs in several situations warrants the use of high speed camera as a potential measurement tool. This article presents the vision based displacement measurement of an under-water model tested on a shake table. High speed video camera is used to record the motion during shaking. The video images are processed using a special motion tracking algorithm and displacements are measured. The sloshing effect of water on the test model and their free vibration at the end of the shaking are studied to calculate natural frequency and damping. Vital information on the allowable under-water motion of the test model is obtained and discussed.

Seismic protection of critical infrastructures through innovative technologies

Development of new technologies for seismic protection will better support the sustainable urban systems. The paper focuses on development of an innovative technology for seismic protection of bridges using smart materials. The seismic protection of structures with the use of special devices is widely accepted as a very effective technique, both for new constructions and for retrofitting of existing ones. Shape memory alloys show the potential to eliminate the limitations of the present technologies, presenting broader application domain. Damper cum restraining device with recentering capabilities has been developed within the laboratory and shake table experiments were conducted on an equivalent SDOF system for a specific narrow band spectrum. The model was subjected to a strong resonant earthquake ground motion in the horizontal direction and analytical investigations were carried out. The damper is found to be very effective for seismic performance enhancement of critical facilities like bridges offering great benefits for the sustainable development of urban systems.

Wind Loads on Curved Roofs: Effect of Side Walls

Wind tunnel pressure measurement studies on a rigid model (scale 1:300) of structure with curved roof has been carried out under open and suburban terrain conditions. The external pressures exerted over the roof due to the presence of side walls have been investigated for the following test cases: (i) roof springing from ground level i.e., side wall height, h = 0.0d and (ii) roof at elevated levels i.e., h = 0.15d and 0.29d, where ‘d’ is span of the roof. The model has been instrumented with point pressure taps on the roof and area averaged pressure taps on the gable end wall and sidewalls. In this paper, results pertaining to mean and standard deviation of pressure coefficients, ( pe C and pe C ~ ), at edge and mid arch locations on the roof for typical angles of wind incidence i.e., wind blowing (i) parallel ( = 0 ), (ii) perpendicular ( = 90 ), and (iii) diagonal w.r.t. normal to gable end ( = 45 ) have been presented. Based on the study, it is observed that the centre half and windward region of the roof of the model with h = 0.29d is subjected to high suction than that for model with h = 0, which is due to the presence of sidewall. Further, evaluated values of pe C for wind blowing parallel and perpendicular to the axis of the arch have been compared with values given in codes of practice and the evaluated values are observed to be between two values reported in AS/NZS and ASCE/SEI codes of practice for = 0 and reasonable agreement at windward quarter for = 90 .

Management and Maintenance Scheduling of Infrastructural Facilities: Road Map

AbstractA four-stage procedure for effective management and maintenance scheduling for infrastructural facilities is presented. The structure/component needing immediate attention is identified during the first stage. The second stage investigations reveal local or global damage and also the location of damage, based on the principles of damage assessment. Nondestructive testing and evaluation form the third stage. In the last stage, repair and remedial measures are carried out, which are followed by testing, if necessary. Out of the case study examples presented, two are specific to the third and fourth stage evaluation only, while one case study example is explained in full.

Seismic performance of polymer modified concretes in flexure-modelling

Considerable research has been carried out in the recent years in the development of models to simulate the inelastic responses of reinforced concrete elements. The enhancement of ductility and the post-peak behaviour are of special interest for the seismic design of structures. Polymer modified fibre concretes are found to be ideal for seismic application with its inherent structural characteristics. An experimental investigation has been undertaken to understand the flexural behaviour of the polymer-modified fibre concrete modified with natural rubber latex. The results are compared with the response of normal strength concrete beam. Analytical modelling of the beams were carried out in a user friendly finite element software to accurately predict the monotonic behaviour of the beams which is considered to be the envelope of cyclic curve. The strains developed were found and are compared with the theoretical results.