Computational Structural Engineering

Pt not only give the problems beautiful solution, but he also showed us how to build it., Now a days , as architectural demand ,structure become more slender and have a very long span ,by RCC we cannot fulfill architecture requirement ,in some case RCC also fulfill architecture requirement for a certain span length but after span RCC structure become costly , so it’s a research work which structure is economical for post tensioning ,for a span, also high labour cost countries is to avoid external scaffolding, for low-rise structures to precast as far as practical and to prestress concrete, not only horizontally, but also vertically so as to resist lateral loads. In most structures today, the increasing use of prestressing has given new freedom to any concept of forms previously considered uneconomic or unfeasible or unduly bulky to resist loads. Curvilinear forms have produced an entirely new vocabulary for architecture that inprevious decades would have been thought of as impractical. The use of prestressing has also been found to be a way of achieving waterproof flat roof surfaces even without the application of normal bituminous waterproofing, since the concrete is kept in continual compression and resists cracking which can otherwise lead to water penetration in the long term.

"Following the current technical rules (EN
1992-1-2), it is possible to assess fire resistance
of reinforced concrete structures by means of
member analysis (tabular methods, simplified or
general calculation methods) subjected to a conventional
time-temperature curve (standard fire).
Nevertheless this approach doesn’t lead necessarily
to a safe design for fire situation, in particular
dealing with precast structures, that often fail
because of hardly depictable phenomena. For this
type of structures often happens that damages
exceed causal circumstances.
In the paper a case study is discussed with
particular regard to the structural behavior during
fire; achieved remarks are based on the reports of
fire brigade e author’s survey.
The actual fire load has been reenacted and
the fire spread simulated in order to understand
the real thermal load acting on the structural elements.
We have ascertained a considerable difference
between the actual fire resistance R and the
requested one (usually 120 min). The reason of
such difference frequently must be researched in
the lack in details design and in insufficient care in
assembling the several elements of the structure."

This paper presents two alternative approaches for the study of reinforced concrete beams under blast loads. In the first approach, the beam is modeled by means of Euler–Bernoulli’s theory and its elastic–plastic behavior is expressed through a new nonlinear relationship between bending moment and curvature. In the second approach, instead, the beam is idealized as a single degree of freedom system. The effects of strain rate, which are of paramount relevance in blast problems, are taken into consideration by introducing time-variable coefficients into the equations of motion derived from the two models. The latter are employed to assess the time-history of the maximum deflection of a simply supported beam subjected to a uniformly distributed blast load. By comparing the theoretical results with some experimental findings available in literature and with the solution obtained from a commercial finite element software, it is found that the first approach is capable of accurately evaluating the maximum deflection of the beam at failure; on the other hand, the second approach provides a less precise prediction, however it is simpler to implement in practice because it requires less computational effort.

The average Chinese resident now consumes 3 kW while a U.S. resident uses about 10 kW on a 24hr/7day basis while an African use only 0.5 kW. Finally, over 1 billion people on the planet are without electricity today. These electrical power consumption rates will greatly increase in the future sustained by the use of coal and natural gas as the primary energy source. Globally, this increase will result in massive increases in greenhouse gases and exacerbate globally warming. There is little scientific doubt now, that this unmitigated human action is threatening the earth's biosphere, resulting in the marked increase in glacial water loss, severe weather disruptions, hurricanes, wild fires, flooding and uncontained biological stress of the planet's ecosystem. There are numerous reasons for the reversal of the optimistic projections for U.S. nuclear electrical power growth made in the 1970's and 1980's.

The main aim of this work is to investigate the seismic vulnerability of traditional masonry buildings, taking into account the impact of dynamic soil-structure interaction (SSI). More specifically, the dynamic response of a typical unreinforced masonry (URM) building constructed over a silty sand layer is examined. The main novelty of the present study is that it considers time-varying soil mechanical properties, i.e., depending on the soil saturation level, which usually varies with time. In addition, a new structural assessment approach, which aims to accurately assess the performance levels (Limit States) of historic buildings and monuments after performing certain seismic rehabilitation measures has been applied. Under this perspective, a quite simple and efficient-in terms of time, cost and effectiveness-intervention was considered, in which blocks of expanded polystyrene (EPS) geofoam are placed at the perimeter of the foundation of theURM building in order to improve its dynamic response and reduce its seismic vulnerability under the examined circumstances. Subsequently, the calculation of building's nominal life is performed in a realistic manner by taking into account the annual changes in the soil saturation level. 1 INTRODUCTION Modern regulations for the evaluation of existing structures [1-3] are based on performance-based assessment, which aims to implement a number of limit states in relation to predetermined seismic actions scenarios [4]. On the other hand, the challenge of balancing safety versus maintenance of the architectural and artistic features of historic structures remains a crucial issue to address, usually on a case-by-case basis. Τhere is a lack of a unified approach for the assessment of seismic risk of monuments and historic structures. Ensuring the monumental buildings' integrity in long terms is an issue that needs further attention and improvements. The most important difficulty, in creating a holistic methodology for assessing the seismic hazard of cultural heritage structures, is the limitations that are imposed on structural interventions. The constraints on the implementation of interventions in cultural heritage buildings are arising from the internationally accepted guidelines and the conceptual differences compared to design of new structures [5]. The best retrofitting practice in monumental structures is considered the application of reversible interventions in order to limit their vulnerability in a less intrusive manner. Performance through Limited Duration Rehabilitation Interventions (LDRI) is a new methodology, which aims to assess the seismic risk of monumental structures [6, 7]. This methodology attempts to provide a framework that quantifies the " safe " duration (i.e., the nominal life) of an intervention that upgrades structural integrity in a specified manner. The nominal life of an intervention is defined as the period for which this action ensures that the structure fulfills selected performance level(s) for a certain seismic scenario (e.g., probability of exceedance 10% and 20% in 50 years, respectively for Significant Damage and Damage Limitation Levels). A typical two-storey URM building, recently presented by the authors [8], was selected as a case study to perform the LDRI methodology, introducing also a new retrofitting scheme as it will be presented in the sequence. In the previous work [8], the impact of silty sand soil saturation level on the dynamic response of a typical masonry building was presented. Additionally, a slight retrofitting scheme was also examined, in which reinforced concrete (RC) friezes were placed at the floor levels and wooden lintels were replaced with RC lintels. The results indicated that the examined building presented higher drifts when the structure was constructed on relatively dry soil, while the slight strengthening with RC elements substantially improved its

"Nowadays, the issue of structural safety under blast loading has become a dramatic problem.
The tragic news  of the terrorist attacks of recent years (9/11/2001, New York; 7/7/2005, London; 7/23/2005, Sharm El Sheik; 1/24/2011, Moscow; etc), raise important, urgent questions regarding the real safety and reliability of our buildings. Extreme loads such as impacts, explosions, etc., can occur in everyday life with unexpectedly high frequency. Actually, the problem of terrorist attacks, so important for strategic and military building design, has been linked to residential and industrial building explosion accidents. The present thesis deals with the flexural failure of Reinforced Concrete beams under blast loads. The main aim is firstly to develop dynamic and energy models capable of evaluating the response of R.C. under explosive load. Then a sensitivity analysis is obtained by means of the above mentioned models in order to determine what are the key  parameters in the beam response. In this way it is possible to attain simple predictive polynomial formulations and, finally, simple table for early tructural assessment of beams under blast load during the design rocedure.
The thesis is composed of three sections. Various dynamic models are developed in Section 1, taking into  account the strain-rate sensitivity of both steel and concrete, as well as other nonlinearities in structural behaviour. Models with different levels of complexity are presented, from the simplest Single Degree Of
Freedom (SDOF) system to Continuous Beam and Finite Element models. The characteristics, advantages and disadvantages of each approach are stated and discussed. The author compares his models with some experimental findings available in the scientific literature. The principal innovation that can be inferred from this section is the hypothesis of distributed plasticity along the beam (in the continuous model), represented by a non-linear smooth relationship between bending moment and curvature. This relationship, in addition to the Euler-Bernoulli beam equation, yields a non-linear Partial Differential Equation solved by means of the Finite Difference Method. In Section 2, the same problem is solved in a different way: starting from the principle of energy conservation, the innovative procedure, developed by the author, can calculate the displacement field of a R.C. beam under blast load. This procedure, less accurate than the previous one, produces very good results regarding midspan displacement, especially as it requires less computation time.
In order to better understand the phenomenon, with the aim of identifying the key parameters in structural response, a sensitivity analysis is developed in Section 3. To this end, the author has performed a numerical investigation referring to the SDOF model presented in Section 1. Several numerical simulations are performed, with random variation of beam and load characteristics. Results are expressed in terms of maximum deflection and maximum velocity for each case. Then a least-squares interpolation has produced various polynomial curves and surfaces representing both a simplified tool to estimate structural response and a sensitivity analysis of the key parameters involved. One of the possible developments of this useful work is represented by simple tables that provide the response of the beam under blast load for early assessment in design procedures."

In the case of structures subjected to explosive loading, the load itself is very uncertain, as it is widely accepted that explosive event is difficult to predict in position, intensity and possibility of occurrence. These random effects associated with material, geometry and loading uncertainty, require to consider them into a probabilistic analysis in order to have a more realistic estimation of the structural response. This paper presents a parametric investigation of the reliability of reinforced concrete (RC) beam flexural members subjected to blast loadings. In particular, the probabilistic responses of the maximum displacement and displacement ductility factor for a reinforced concrete (RC) flexural member against potential blast loadings are evaluated by non linear dynamic analysis of its equivalent single-degree-of-freedom (SDOF) system. Reliability of such elements is presented and discussed.