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In this paper solution of a non-stationary one dimensional (1D) heat conduction problem has been presented. The finite difference method, i.e. by applying energy balance has been used. The finite difference method has been applied and the partial differential equation of heat conduction has been reduced to an algebraic form. This procedure is also called discretization problem. By solving the system of algebraic equations, temperatures at discrete points - network nodes were obtained. Additional discretization was performed in non-stationary processes over time. Numerical 1D non- stationary calculation was performed on six walls of different thickness made of aerated concrete 50 mm, 75 mm, 100 mm, 120 mm, 150 mm and 250 mm thick are exposed to the developed fire. The developed fire represents the logarithmic dependence of the temperature as a function of time according to the standard SRPS EN 834-1. The period of wall heating was analyzed, i.e. period until the moment when the temperature rise is observed on the non-exposed side of the wall. The paper compares the achieved experimental results with the obtained numerical results.

The unsteady heat conduction in composite planar structure, with arbitrary number of layers, using analytical approach based on Greeds Functions (GF) is analyzed. The analytical solution for spatial and temporal temperature distribution is evaluated in the general form and expressed in the terms of the convolution integrals. The GF are employed in the novel approach for calculation of Thermal Response Factors (TRF) with arbitrary shape functions for unsteady heat conduction in composite planar structure. The two pairs of TRF for spatial and temporal distribution of the temperature and the thermal flux are obtained. The whole analysis is performed in the time domain. A numerical scheme for efficient evaluation of convolution integral suitable for practical application in the case of the long term measurements with lower sampling rates is developed. The in-situ measurements of inside and outside surface temperatures and outside heat flux for a building wall under real dynamical environmental conditions during the period of then days are used for validation of the presented results and to demonstrate the possible practical application. Using developed approach and recorded surface temperatures as inputs the temporal and spatial distributions of the temperature and the thermal flux are obtained. These results are compared with experimental data and numerical simulations obtained by the Finite Volume Method (FVM).

Purpose – This study aims to reveal more information and understanding on performance and failure mechanisms of high strength steel endplate connections after fire. Design/methodology/approach – An experimental and numerical study on seven endplate connections after cooling down from fire temperature of 550°C has been carried out and reported herein. Moreover, the provisions of European design standard for steel structures, Eurocode 3, were validated with test results of high strength steel endplate connections. Findings – In endplate connections, a proper design using a thinner high strength steel endplate can achieve the same failure mode, similar residual load bearing capacity and comparable or even higher rotation capacity after cooling down from fire. It is found that high strength steel endplate connection can regain more than 90 per cent of its original load bearing capacity after cooling down from fire temperature of 550°C. Originality/value – The post-fire performance of high strength steel endplate connection has been reported. The accuracy of Eurocode 3 for endplate connections is validated against test results. Keywords Numerical study, Experimental study, High strength steel, After fire, Endplate connection, Steel & Composite Structures

Purpose – This study aims to reveal more information and understanding on performance and failure mechanisms of high strength steel endplate connections after fire. Design/methodology/approach – An experimental and numerical study on seven endplate connections after cooling down from fire temperature of 550°C has been carried out and reported herein. Moreover, the provisions of European design standard for steel structures, Eurocode 3, were validated with test results of high strength steel endplate connections. Findings – In endplate connections, a proper design using a thinner high strength steel endplate can achieve the same failure mode, similar residual load bearing capacity and comparable or even higher rotation capacity after cooling down from fire. It is found that high strength steel endplate connection can regain more than 90 per cent of its original load bearing capacity after cooling down from fire temperature of 550°C. Originality/value – The post-fire performance of high strength steel endplate connection has been reported. The accuracy of Eurocode 3 for endplate connections is validated against test results. Keywords Numerical study, Experimental study, High strength steel, After fire, Endplate connection, Steel & Composite Structures