Multi-story Steel Structures Research Articles

Mechanical State of Multi-Story Structures Induced by Wind Action

AbstractObjective of the present study is to define the dynamic mechanical response of multi-story structures acted upon by wind. Structural response is associated to the dynamically applied wind and is approached by considering its three components: static, kinematic and energy states. Proposed objective is achieved by structural dynamic analyses performed on multi-story steel structures in elastic domain. The dynamic model is the multi-degree of freedom system associated to lateral story level displacements. Dynamic forces are computed from recorded velocities of wind through a simple velocity – pressure – force transform. The matriceal differential equation of wind induced vibratory state is dealt with by both, direct integration and modal decomposition. The three components of the mechanical state are expressed via base shear force – the static state, lateral story-level displacements – the kinematic state and wind induced energy – the energy state. Modal decomposition of the dynamic response allows for immediate computation of modal contribution to the total wind response. Computed values of the parameters are numerically and graphically presented and commented. Relevant conclusions are inferred.

Response of Steel Moment and Braced Frames Subjected to Near-Source Pulse-Like Ground Motions by Including Soil-Structure Interaction Effects

Most seismic regulations are usually associated with fixed-base structures, assuming that elimination of this phenomenon leads to conservative results and engineers are not obliged to use near-fault earthquakes. This study investigates the effect of soil–structure interaction on the inelastic response of MDOF steel structures by using well known Cone method. In order to achieve this, three dimensional multi-storey steel structures with moment and braced frame are analysed using non-linear time history method under the action of 40 near-fault records. Seismic response parameters, such as base shear, performance of structures, ductility demand and displacement demand ratios of structures subjected to different frequency-contents of near-fault records including pulse type and high-frequency components are investigated. The results elucidate that the flexibility of soil strongly affects the seismic response of steel frames. Soil–structure interaction can increase seismic demands of structures. Also, soil has approximately increasing and mitigating effects on structural responses subjected to the pulse type and high frequency components. A threshold period exists below which can highly change the ductility demand for short period structures subjected to near-fault records.

Performance Base Design of Multi-Storey Steel Structures Considering Dynamic Loads Originated by Geological Agents

Dynamic stresses generated by geological agents such as earthquakes, sand storms and hurricanes causes great damages to the structures. In this research dynamic loads the effect of generated by these geological agents have been taken into account for the performance base evaluation and design of rigid steel frames. The effect of fundamental periods on the design of these frames taking into account the variation in the behaviour factor and drift limitations is highlighted. The periods are obtained from the modal dynamic analysis; their performances were tested through nonlinear pushover analysis and these are then compared with the periods obtained from codified formulations. The weight of the designed frames are normalised with respect to the modal periods. It is observed that as the drift limitation varies from the lower limit (relaxed one) to the upper limit (stringent one); the fundamental period of the frames decreases and so the stiffness of the frame increases due to the members (beam and columns) sizes. Furthermore, it can be noted that the periods calculated from the codified formulations are in the same range to the one obtained from the modal analysis when the strict drift limit is incorporated.

Geometric Non-Linear Approach to Stiffness State of Semi–Rigid Structures

Abstract Present contribution intends to emphasize the contribution of geometric non-linearity to the stiffness state of semi-rigid multi–storey steel structures. Though semi-rigidity of beam – column connections involves a nonlinearity at constitutive bending momentrelative rotation level, the geometric nonlinearity associated to deformed conFigure uration at element level is less referred to. The main objective of the study is to express the stiffness state of geometric non-linear elements semi-rigidly connected at its ends. Stiffness state is, in its term, expressed by element level stiffness matrix considering the six degrees of freedom of the planar element. Regarding the reference system, both local and global systems are employed allowing a simple and direct transition from element level vectorial relations to their structural level forms. The three fundamental vectorial relations (static equilibrium, kinematic compatibility, material constitutivity) emphasize that the principle of virtual work holds in the case of semi-rigidly connected skeletal structures as well.

On the Seismic Performance of Hat Knee Bracing System in Low-Rise Multistory Steel Structures

In this paper, the behavior and performance of a new type of bracing system called Hat Knee Bracing (HKB) is investigated in low-rise multistory steel structures. This novel form of resistant system, which provides reasonable stiffness in moderate earthquakes, consists of a V shaped knee member connected to mid span of the beam and the brace members. In this research work, the “FEMA P695 evaluation method” is utilized in order to explore the nonlinear behavior of the HKB frame, and quantification of three seismic performance factors: Response Modification Factor, Over-strength Factor, and Deflection Amplification Factor. The seismic response simulation of archetype frames is performed using the OpenSees software. The results of analyses reveal that the performance of the HKB is suitable under a rare earthquake and under moderate intense earthquakes the damages are mostly concentrated in knee members instead of the principal members such as beams and columns.

Impact Analysis of Load-Bearing Structure Form on the Construction Cost of Steel Frame Structure House

The influence of bearing structure form on the construction cost of use of steel in house building is obvious. Based on the calculation of different bearing structure forms, the steel consumption are given and the analysis of the influence on cost are shown in this paper. And the most economical bearing structure form of multi-storey steel structure house is also obtained.

보 붕괴형 메커니즘을 가지는 강구조 다층골조의 손상분포

부재의 내력비, 강성비에 영향을 받는 다층 강구조 골조의 내진성능을 평가하기 위하여 내력비 및 강성비를 설계 파라메타로 하여 동적 비탄성 응답해석을 수행하였다. 해석 결과에 대한 분석을 통하여 내력비와 강성비의 변화폭이 큰 다층골조의 손상분포 예측식을 제안하였다. 본 연구에서 얻어진 결과는 다음과 같이 요약할 수 있다. 1) 보기둥 내력비 및 강성비가 작아질수록 1층의 기둥 주각부에서의 손상집중 현상이 크게 나타났다. 2) 보기둥 내력비 및 강성비를 고려하여 보붕괴형 강구조 다층골조의 손상분포를 예측할 수 있는 식을 제안하였으며, 예측식은 응답해석 결과와 좋은 대응을 보였다. 3) 본 연구에서 제안한 손상분포 예측식은 강접 및 반강접 보붕괴형 강구조 다층골조의 손상분포를 예측할 수 있을 것으로 판단된다. In order to evaluate the limit earthquake resistance of multi-story steel frames influenced by the strength and stiffness ratios of members, a series inelastic response analysis were carried out. From the analysis results, the damage distribution rules of multi-story steel frames were proposed. Conclusions are summarized as follows; 1)As the stiffness ratios of beam and column becomes small, the damage concentrates on the lower end of columns of the first story. 2) Considering the strength and stiffness ratios of the beam and column with weak beam type mechanism, the equations predicting the damage distribution of multi-story steel flames were proposed. 3) Through the equation which was supposed in this study, it is speculated that the damage distribution of the rigid or semirigid beam collapse type multi-story steel structure building can be predicted.

Plastic Collapse, Shakedown, and Hysteresis of Multistory Steel Structures

The entire spectrum of incremental collapse behavior, including alternating plasticity, shakedown, and plastic (limit state) collapse, of multibay, multistory structures composed of elastic‐perfectly plastic materials can be determined from a consideration of the irrecoverable energy (hysteresis energy) dissipated by the plastic hinges that occur in such structures. An extensive study utilizing computer models of the relevant structural behavior has revealed that much of this hysteresis energy dissipation is concentrated in a relatively few dominant plastic hinges. Strengthening or weakening structural components at those locations where dominant plastic hinges form can significantly alter the incremental collapse behavior of the entire structure. The rate of energy dissipation, as well as the rate of approach to failure, can vary in a complex manner in multibay, multistory structures subjected to many cycles of repetitive loads. It is demonstrated that this complex structural behavior may be unraveled by performing a detailed investigation of the evolution of hysteresis energy at each of the plastic hinges that forms in the structure. A series of such investigations has revealed the roles that prominent and latent plastic hinges play in the overall response of the structure to repetitive loads. New directions for research aimed at improving the analysis and design of earthquake‐resistant buildings are indicated by the results, which show that the global resistance of the entire structure to incremental collapse depends upon the details of the applied loading program, as well as upon the local plastic moment resistance of the individual structural components. Illustrative results from the application of the new method are given for a two‐bay, two‐story rigid frame structure.