Sharif Digital Repository

This study proposes a novel type of metallic yielding damper called block slit damper or BSD. This damper is a slit damper with very low height to thickness ratio. This device has high shear capacities, and is more economical than SSD devices with high height to thickness ratios. Based on theoretical analysis the formulation for the BSD device's main parameters is derived. Then to investigate the hysteretic behavior of the proposed devices, 5 specimens with different aspect ratios (height-width ratios) were manufactured and tested in a quasi-static manner. The tests revealed that by reducing the aspect ratios, the shear and energy dissipation capacity increases while the displacement... 

A new semi-rigid beam-to-column, as well as bracing-to-frame, connection has been developed. In addition to its application in building structures, due to its special features and characteristics, it can best lend itself to offshore jackets, where fracture caused by fatigue has always been a major concern. The adverse effects of welding, material embrittlement, residual stresses, etc., pronounced by cyclic loading on such structures, can be overcome by using this new connection. Moreover, it can be easily used in the structure of various modules used in the topside of platforms and FPSOs. The particular feature of this connection is its geometry, which is so devised that it allows much... 

This paper investigates the influence of an opening in the infill steel plate on the behavior of steel trapezoidal corrugated infill panels. Two specimens of steel trapezoidal corrugated shear walls were constructed and tested under cyclic loading. One specimen had a single rectangular opening, while the other one had two rectangular openings. In addition, the percentage of opening in both specimens was 18%. The initial stiffness, ultimate strength, ductility ratio and energy dissipation capacity of the two tested specimens are compared to a specimen without opening. The experimental results indicate that the existence of an opening has the greatest effect on the initial stiffness of the... 

A new beam-to-column and bracing-to-frame connection that can tolerate high rotational and shear overload is described. The connection is a self-contained separate entity that comprises two parallel attachment plates between which two circular tubes are laid and fixed through welding. The whole combination can also be produced by extrusion, where the plates are laid in an orthogonal relation with the axis of bending. In the welded version, the two plates are laid in a parallel relation with the axis of bending  

In this paper a particular structural bracing system, called the Chevron Knee Bracing (CKB), is introduced. In this framing system, a special form of diagonal braces that are connected to knee elements instead of beam-column joints is investigated. The braces provide required stiffness during moderate earthquakes, while the knee elements yield in flexure or shear to dissipate energy during a severe earthquake, whereby buckling of the braces or yielding of the main structure is prevented. First, elastic analysis is applied to the new system and a suitable shape and angle for the knee and the brace elements is proposed, using new and practical parameters. Then, by developing a nonlinear... 

A new general semi-rigid beam-to-column connection for skeletal structures, also applicable to offshore platforms, was devised. In a previous paper (OMAE02-28264), the general features of this joint together with some proposed details for its use in fabricating new platforms, as well as retrofitting and repair of existing platforms, were introduced. Moreover, the results of some quasi-static tests on the 'original' version of the connection, in which the energy-dissipating elements (tubes) of the connection are laid in a parallel relation to the axis of bending, were reported. Here, in this paper, the results of recent experimental work on the 'alternate' version of the connection, in which... 

Seismic response of steel moment-resisting frames equipped with a novel passive damper called infilled-pipe damper (IPD) is investigated in this study. The IPD is a very economical and easily assembled structural control device with high energy absorption, invented recently by the authors. A simplified trilinear load-displacement model for IPD devices is suggested to be used in this study and further investigations. Next, criteria for IPD elements size selection are proposed for passive control of structures against earthquake loads. Steel frame structures of 5, 10, and 20 stories are designed without any IPD devices. Then, the frames are equipped with IPDs of different stiffness. The frames... 

Theoretical and experimental verification of the pipe damper was investigated in Part I of the two companion papers. In this paper, the application of the pipe damper to structures is examined. In particular, single span slab-girder bridges are considered for analytical investigations. A practical detail for the installation of the pipe damper is introduced. Nonlinear dynamic time history analyses are conducted on bridges equipped with the pipe damper and the results are compared with ordinary bridges. Bridge span, ground motion and the pipe length are varied in the analyses. Results show that the pipe damper is a reliable and economical metallic-yielding device that can easily be installed... 

In this article, the cyclic performance of an innovative precast beam-to-column connection is evaluated experimentally and numerically. Two full-scale beam-column cross-shape interior connection specimens named PF-1 and PF-2 are tested. By adding extra nuts to the connecting bolts, specimen PF-2 behaves in a more shear-dominant pattern and shows less pinching. Comparison of performance of these specimens with the numerical monolithic model in terms of stiffness, strength, ductility and energy dissipation capacity indicates the proposed system can provide conditions close to the monolithic connection. However, to reduce the pinching drawback, a minor modification was made leading to... 

The Energy Dissipating Restraint (EDR) is a friction device which can be used to dissipate the energy introduced to a structure by a seismic event. In this paper, the performance of the structures which are equipped with the EDR is investigated in several intensity levels by using a novel seismic analysis method, namely the Endurance Time (ET) method. By reasonably estimating the response of structures over the entire range of the desired intensity levels through each time-history analysis, this method can effectively reduce the computational cost, offering an appropriate procedure for performance-based design of structures. The EDR performance in the seismic control of steel frames is... 

This paper presents the experimental investigation of an innovative energy dissipation system in steel moment resisting frames. In the proposed system, a replaceable beam with a smaller cross-section than that of the main beam is placed at the mid span of the beam designed to act as a shear fuse. This shifts the location of the plastic hinging from the end of the beam to the middle since the shear fuse yields in shear prior to the flexural yielding of the main beam. This system eliminates the need to comply with the rigorous limitation on the beam span-To-depth ratio that is proposed by seismic design codes to ensure the formation of plastic hinges at the two ends of the beam. Moreover, this... 

In this article, a novel passive control system, ribbed bracing system (RBS), has been proposed to deal with the buckling problem. RBS is a bracing system with a simple mechanism that can be installed in braces as a supplemental part. The behavior of RBS is similar to that of conventional braces under tensile loading. However, under compressive force, it endures an insignificant force and prevents the braces from buckling through length reduction. In addition, seismic damage is concentrated in the bracing system of the structures equipped with RBS, decreasing the dissipated hysteretic energy in other structural members. There are two different mechanisms for RBS: 1) completely-closed RBS... 

Thermoelastic damping (TED) is one of the main energy dissipation mechanisms in structures with small scales. On the other hand, the classical continuum theory is not capable of describing the mechanical behavior of small-scale structures. In this paper, small-scale effects on the thermoelastic damping in microplates are studied. To this end, the coupled governing equations of motion and heat conduction are obtained based on the non-classical continuum theory of the modified couple stress and the dual-phase-lag heat conduction model. By solving these coupled equations, an explicit expression including small-scale effects for calculating TED in microplates is derived. The results are compared... 

Concentric braced frames are commonly used in steel structures to withstand lateral forces. One of the drawbacks of these systems is the possibility that the braces are buckled under compressive loads, which leads to sudden reduction of the bearing capacity of the structure. To overcome this deficiency, the idea of the Buckling Restrained Brace (BRB) has been proposed in recent years. The length of a BRB steel core can have a significant effect on its overall behavior, since it directly influences the energy dissipation capability of the member. In this study, numerical methods have been utilized for investigation of the optimum length of BRB steel cores. For this purpose, BRBs with... 

The low-cycle fatigue performance of shear panel damper (SPD) highly depends on the geometry of its shape and the criterion considered for its design. The main contribution of the current study is to find the optimum shape of the SPD subjected to cyclic loading by considering two different objective functions. The maximum equivalent plastic strain and the ratio of energy dissipation through plastic deformation to the maximum equivalent plastic strain are selected as the first and second objective functions, respectively. Since the optimization procedure requires high computational efforts, a hybrid computational approach is used to perform two paramount phases of estimating the inelastic...