Share:


Stress, strain and creep analysis of the layered composite structures under sustained loading

Abstract

The paper proposes numerical and analytical models of the time-dependent analysis of a multilayered composite. These models enable us to predict the time-dependent behaviour of composite structures made of materials having age-variable properties. The proposed numerical model deals with a numerical solution of linear Volterra integral equation implying the validity of the principle of superposition for the layers. Meanwhile, the proposed analytical approach is based on the application of the age-adjusted effective modulus method for the composite. The validity of these models has been proven by a direct calculation of the time-dependent stresses and strains for the three-layered composite wall structure comparing the obtained theoretical values with those determined numerically. In particular, it was demonstrated that the analytical approach gave the identical values of the time-dependent stress strain state parameters. Relying on the results obtained, the concluding remarks have been summarized as follows: a) Despite the fact of sustained load, acting on the composite made of layers with different time-dependent deformational properties does not always hold time-invariant layer stress. In particular, the layers possessing a higher strain tend to produce relaxation while the layers with a lower strain are undergone the stress increase to maintain the equilibrium between internal and external forces (Fig. 4, b, e). Therefore, the failure should primarily be originated from the layer with a lower strain; b) Time variation in the elastic modulii of the layers is responsible for the increased stresses at time t in a higher strain layer due to a partial recovery of instantaneous strains. This effect is more progressive at a young age of the composite loaded (cf. Fig. 4, b and e); c) The ageing coefficient between the layers is different and is mainly subjected by the history of the ageing process of the layers. However, at the age of loading exceeding 28 days, the difference in the ageing coefficient of the layers is insignificant (Fig. 4, a). Moreover, it should be emphasized that the ageing coefficients of the layers are coincident with each other for the case of the time invariant elastic properties of the layers (Fig. 4, d). d) For the most practical purposes requiring long creep periods (exceeding 360 days), an approximate value of the ageing coefficient of the layers equal to 0.8 should be recommended predicting the stress-strain state of the layered composite using the proposed analytical method. More sophisticated functions for the ageing coefficients proposed by Lacidogna and Tarantino (1996), Ghali et al. (2002), ACI 209R-92 may be implemented for the sake of analysis accuracy. e) The values of the creep coefficient for the whole composite are mainly within the values of the creep coefficients of the layers.


Sluoksniuotųjų konstrukcijų įtempių ir deformacijų būvio bei valkšnumo analizė, veikiant ilgalaikei apkrovai


Santrauka


Sluoksniuotojo kompozito ilgalaikei įtempių ir deformacijų būvio analizei atlikti pasiūlyti skaitiniai ir analitiniai modeliai. Jie leidžia prognozuoti kompozitinių konstrukcijų, pagamintų iš bet kokio skaičiaus sluoksnių, kuriems būdingas ilgainiui pasireiškiantis senėjimas, tampriai valkšnios deformacijos savybes per laiką. Skaitinis modelis grindžiamas Volterra lygties skaitine formuluote, kai kintančių laike sluoksnių įtempių sukeltoms suminėms deformacijoms nustatyti taikomas poveikių superpozicijos principas, leidžiantis sumuoti šių sluoksnių įtempių prieaugių sukeltas deformacijas. Pasiūlyti analitiniai modeliai remiasi senėjančios medžiagos efektyviojo modulio metodo pritaikymu. Atlikta modelių verifikacija bei pateiktas nuoseklus trisluoksnės sienos skaičiavimo pavyzdys, kuris gali būti naudingas statybos inžinieriui, projektuojančiam kompozitines konstrukcijas. Tiesioginio skaičiavimo būdu taip pat parodyta, kad analitinis modelis duoda skaitiniu būdu gautus rezultatus. Sudalijus nagrinėjamą laiko intervalą į gana mažus laiko tarpsnius, skaitinis sprendimas yra laikytinas tiksliu. Taikant skaitinį ir analitinį modelius, nustatant jų privalumus ir galimybes, analizuoti įtempių ir deformacijų pasiskirstymo tarp sluoksnių dėsniai, apskaičiuoti valkšnumo parametrai.


First Published Online: 16 May 2013


Reikšminiai žodžiai: sluoksniuotoji konstrukcijaįtempių persiskirtymassenėjimo ir valkšnumo koeficientaikompozito valkšnumo matas.

Keyword : layered composite structure, time-dependent redistribution of stress, creep and ageing coefficients, creep coefficient for the whole composite

How to Cite
Marčiukaitis, G., & Balevičius, R. (2009). Stress, strain and creep analysis of the layered composite structures under sustained loading. Engineering Structures and Technologies, 1(3), 123-134. https://doi.org/10.3846/skt.2009.15
Published in Issue
Oct 29, 2009
Abstract Views
30
PDF Downloads
32
Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.