Calculation of the effect of topography on the observed gravity becomes particularly important when modelling high-precision geoid. It requires a digital terrain model of appropriate resolution and accuracy. Various global, regional and local digital terrain models of different accuracy and resolution are recently available. Evaluation of the DTM used is required for verification and validation of its quality as well as for estimating accuracy of geoid model derived with considering the effect of topographic masses. Two DTMs: the SRTM3 of 3" x 3" resolution and the national DTM for Poland of l" x l" or l" x 2" resolution - called DTED2 - were evaluated with use of high-resolution local DTMs developed using digital photogrammetry of 25 m x 25 m as well as the regional model in Tatra mountains of 10 m x 10 m. Then the heights of almost 1000 GPS/levelling stations of Polish geodetic control were compared with the heights from the DTED2 model. The heights of over a million of gravity stations from gravity database, that were the basis of previous geoid modelling in Poland, were also compared with the heights from the DTED2 model. The effect of uncertainty of a DTM on estimation of mean gravity anomalies was discussed. In particular, the effect of replacing heights from gravity database with the heights from the DTED2 model in the process of calculating mean gravity anomalies, on the accuracy of geoid modelling was investigated. The use of the DTED2 model is at present recommended for determination of precise geoid model in Poland.

This paper investigates the influence of isolation systems on the seismic behavior of urban reinforce concrete bridge. The performance of the Hesarak Bridge constructed in Karaj city, Iran with two isolation systems; i.e. the existing elastomeric rubber bearing (ERB) and a proposed lead rubber bearing (LRB) is discussed. The numerical model was implemented in the well-known FEM software CSIBridge. The isolated bridge has been analyzed using nonlinear time history analysis method with seven pairs of earthquake records and the results are compared for the two isolation systems. The LRB isolators are shown to have superior seismic performance in comparison with the existing ERB systems based on the response evaluation including force on the isolator, pier base shear, deck acceleration, bending moment, pier displacement, and energy dissipation.

The research focuses on the properties of foam glass, popular insulation material used in various industries and applications, including construction, chemistry and defence, after several years of use under varying load, thermal and humidity conditions. The material used as an insulating sub-base underneath industrial steel tank, which had failed with a threat of leakage of the stored high-temperature medium (200°C), was tested. After macroscopic and material evaluation of the foam glass samples, their compressive strength, water absorption, and behaviour under complex conditions including loading, high temperature, and moisture were examined experimentally. Absorption of water considerably affects reducing the foam glass performance. Investigations show that the foam glass generally does not reach the declared compressive strength. If this surface is additionally heated to high temperature, the foam glass undergoes destruction by chipping or crushing just at stresses several times lower than the limits for this material, and even with no applied load. The test results show that foam glass exposed to simultaneous action of water and high temperature undergoes progressive deterioration, resulting in a decrease in declared parameters and losing its usability. Therefore, effective and durable protection from water is of critical importance to ensure reliability of foam glass exposed to high temperatures.