Main structure design (structural design) for constructions
Until now, as design office, the company "L I L Structural Design" S.R.L. has directly insured the main structure design or the structural design*) for the following construction types:
large shopping centers (as "hypermarkets" or "supermarkets");
buildings of large commercial spaces (as "mall");
retail centers and retail parks;
blocks of flats;
other types of civil buildings and civil construction structures.
colums (piles) with different destinations;
towers with different destinations;
other types of special buildings and special structures.
In addition, the "L I L Structural Design" S.R.L. may insure, on the beneficiaries’ request – indirectly, by the collaborators of an irreproachable quality – the performance of construction design works and on other specializations (topography, geotechnics, architecture, installations, roads, bridges, inside design, etc.), with or without the obtaining of the “Quality verification resumes of the projects” (on different requirements) from the MLPAT certified technical verifiers.
*) The main structure design or the structural design of a building or of a construction is supposing – mainly – the performance of the following stages:
1. Structural analysis of the main structure
This stage -"of finesse"- of the structural design is involving the performance of the following steps:
1.a) structural conception, supposing the settlement of the configuration of the resistance structure and the predimensioning of the elements composing it, starting from:
- the plans of the architectural project;
- norms and / or normatives of structural conformation in force;
- prescriptions regarding the choice of the geometric dimensions of the construction elements according to the of the structure conformation (openings, bays), their way of support and even according to the similar projects previously elaborated;
1.b) structural modeling, supposing the modeling of the main structure (conceived within the previous stage) within a structural analysis program (FEA software), which in the greatest majority of the cases, is based on the Finite Element Method (MEF); more specifically, by the aid of the pre-processor of the structural analysis program, there is introduced the following data regarding the model of the structure:
- structural elements:
- columns and beams - modeled with the one-dimensional elements, as “bars”;
- panels, diaphragms - modeled with the bi-dimensional elements, as plain or curved “surface or area elements”;
- blocks and massive elements - modeled with tri-dimensional elements, as “volume elements”.
- material characteristics: density; elastic modules (longitudinal – Young and transversal); coefficient of the transverse contraction – Poisson: resistance; etc.);
- restrictions (imposed by the nodes – in displacements; in stresses and / or efforts; in elastic constancies, etc.); these restrictions are improperly denominated “rests”, “arresters” or "supports";
- loads, introduced as forces (distributed – concentrated, constant – variable, static – dynamic, etc.); they are mentioned both in load cases and as load combinations;
1.c) properly structural analysis, supposing the use of the analyzer of the structural analysis program, for the obtaining of the results regarding the solicitation level of the main structure elements, in the different hypothesis of load and load combinations.
This stage is ending up with the use of the post-processor of the structural analysis program (FEA software), for following and verifying the obtained result, emphasizing the three aspects of the solicitation:
- geometric aspect, emphasized through:
- mechanic aspect, emphasized through:
- energetic aspect, emphasized through:
- potential deformation energy;
- mechanic work of the force fields;
A properly successful structural analysis is having as end the validity of the obtained results.
REMARK: This stage is called by some (improperly, wrongly!) as the statical analysis of the structure or the static calculation of the structure. The error is coming from especially from the fact that a complete structural analysis is involving also the dynamic analysis or the dynamic calculation of the structure (more specifically, a modal analysis and a seismic analysis of this one). Thus, it is wrongly to talk about the static analysis and the static calculations when it is about structural analysis.
2. The structural dimensioning of the structure (the dimensioning of the elements of the main structure)
This – “routine” – stage, of the structural design supposes the use of the obtained results through the structural analysis within the calculation methods provided by the norms and normatives regarding the dimensioning of the different types of element sections, for the settlement (from quality and quantity point of view) of the materials which must be used on the performance of the main structure, so that this should correspond from the point of view of the previously modeled requests, in the 1st stage (from above).
4. Structural optimization (optimization of the main structure)
This - “consciousness” – stage, of the structural design, supposes the iterative route of the steps 1.c. and 2 (from above), for the previously modeled and configured main structure to reach some structural performance indexes, such as: minimal consumption of materials; minimum manpower consumption; reduced performance time; etc.
This stage is considered by some designers as an additional stage, optional, of the structural design, which must make the object of some special clauses within the "Design contract" or even the object of another autonomous contract, independent of the initial one. And this, because it is involving additional efforts, very hard to quantify by the designer and not easely verifiable by the beneficiary and which – for many times – do not find the financial covering in the service agreement concluded between the two parties.
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