Special Moment Resistant Steel Buildings

The seismic response of special moment-resisting frames (SMRF), buckling restrained braced (BRB) frames and self-centering energy dissipating (SCED) braced frames is compared when used in building structures many stories in height. The study involves pushover analysis as well as 2D and 3D nonlinear time history analysis for two ground motion hazard levels. The SCED and BRB braced frames generally experienced similar peak interstory drifts. The SMRF system had larger interstory drifts than both braced frames, especially for the shortest structures. The SCED system exhibited a more uniform distribution of the drift demand along the building height and was less prone to the biasing of the response in one direction due to P-Delta effects. The SCED frames also had significantly smaller residual lateral deformations. The two braced frame systems experienced similar interstory drift demand when used in torsional irregular structures.

Calculated assessment of the impact of geometric deviations from the design on the parameters of mechanical safety of building metal structures within the framework of scientific and technical support for construction

An important part of scientific and technical support of civil engineering facilities at a construction stage - evaluation of influence of fluctuations from a designed geometry onto mechanical safety parameters of load-bearing metal structures - is considered. A multi-tier structure (industrial frame tower) is employed to demonstrate main features of such an assessment. Given is an approach to an analysis of as-built documentation and to a choice of most significant fluctuations of structural metal elements from a designed geometry. Effect of erection sequence being taken into consideration, the so-called genetic non-linearity, during computational estimation of a stress-strain state of metal structures mounted with deviations from their design positions is investigated. Results of static and dynamic analyses of designed and as-built (with geometry fluctuations taken into consideration) models of the multi-level industrial frame tower are obtained and compared with each other. Basing on these results, guidelines for computational assessment of effects of fluctuations from a designed geometry onto mechanical safety parameters of similar frame systems are formulated.

The application efficiency of precast monolithic frame systems in civil engineering

Introduction. The partial replacement of cast-in-situ concrete with precast concrete in the residential construction sector allows to reduce construction time and cost, increase labour productivity and cut CO2 emissions. Combinations of prefabricated and monolithic elements in precast monolithic frames are presented; they encompass 6 different structural options of precast monolithic frames and 2 types of monolithic frames. The co-authors compare production costs and integrated labor intensity for all frame design options, construction periods per 1,000 m3 of a residential building for various structural options of the frame, and assess potential reduction in carbon dioxide emissions due to a change in the amount of precast reinforced concrete in the building frame structure. Materials and methods. The co-authors have developed a method that employs weighted average to identify the optimal type of a precast monolithic frame. The method takes account of such factors as production costs, integrated labour intensity, construction time and reduction in carbon dioxide gas emissions (in per centum) per 1,000 m3 of the frame structure. Results. The optimal structure of a precast monolithic frame was selected and calculated using weighted average. Weighted average was used to identify the most effective structural frame. The calculation results have shown that ARKOS precast monolithic frame with precast columns is the leader in terms of weighted average; it best suits the construction of a residential building. If we consider each of the selected indicators separately, RECON frame with precast floors is to be selected; however, RECON is inferior to ARKOS in terms of weighted average due to different values of the weight coefficients attached to each of the assessment criteria. Conclusions. The co-authors have proven the efficiency of precast monolithic frame systems in comparison with monolithic frames if applied to construct a residential building. The proposed method was employed to select the optimal type of frame.

Electrodynamics in noninertial frames

The electromagnetic theory is considered in the framework of the generally covariant approach, that is applied to the analysis of electromagnetism in noninertial coordinate and frame systems. The special-relativistic formulation of Maxwell’s electrodynamics arises in the flat Minkowski spacetime when the general coordinate transformations are restricted to a class of transformations preserving the Minkowski line element. The particular attention is paid to the analysis of the electromagnetism in the noninertial rotating reference system. For the latter case, the general stationary solution of the Maxwell equations in the absence of the electric current is constructed in terms of the two scalar functions satisfying the Poisson and the biharmonic equations with an arbitrary charge density as a matter source. The classic problem of Schiff is critically revisited.

Discrete Rigid Block Analysis to Assess Settlement Induced Damage in Unreinforced Masonry Façades

In this study, a system of discontinuous rigid blocks is employed to simulate the possible damage mechanisms in unreinforced masonry (URM) façades and load-bearing frame systems subjected to settlement using the discrete element method (DEM). First, the employed modeling strategy is validated utilizing the available experimental results presented in the literature. Once there is a good agreement between the computational models and experimental findings, a sensitivity analysis is performed to quantify the influence of the input parameters defined in the DEM-based numerical model. Finally, the proposed modeling strategy is further utilized to assess the damage pattern that may develop in a URM façade due to uniform and non-uniform settlement profiles. The results of this study clearly show that the discrete rigid block analysis (D-RBA) provides robust numerical solutions that can be employed to visualize and assess the possible damage patterns and related collapse mechanisms of URM masonry systems as an alternative modeling strategy to standard continuum-based solutions.