Abstract: This paper deals with different modeling aspects of masonry infill: no infill model, Layered shell infill model, and strut infill model. These models consider the complicated behavior of the in-filled plane frames under lateral load similar to an earthquake load. Three strut infill models are used: NBCC (2005) strut infill model, ASCE/SEI 41-06 strut infill model and proposed strut infill model based on modification to Canadian, NBCC (2005) strut infill model. Pushover and modal analyses of a masonry infill concrete frame with a single storey and an existing 5-storey RC building have been carried out by using different models for masonry infill. The corresponding hinge status, the value of base shear at target displacement as well as their dynamic characteristics have been determined and compared. A validation of the structural numerical models for the existing 5-storey RC building has been achieved by comparing the experimentally measured and the analytically estimated natural frequencies and their mode shapes. This study shows that ASCE/SEI 41-06 equation underestimates the values for the equivalent properties of the diagonal strut while Canadian, NBCC (2005) equation gives realistic values for the equivalent properties. The results indicate that both ASCE/SEI 41-06 and Canadian, NBCC (2005) equations for strut infill model give over estimated values for dynamic characteristic of the building. Proposed modification to Canadian, NBCC (2005) equation shows that the fundamental dynamic characteristic values of the building are nearly similar to the corresponding values using layered shell elements as well as measured field results.
Abstract: This paper presents the data of a series of two-dimensional Discrete Element Method (DEM) simulations of a large-diameter rigid monopile subjected to cyclic loading under a high gravitational force. At present, monopile foundations are widely used to support the tall and heavy wind turbines, which are also subjected to significant from wind and wave actions. A safe design must address issues such as rotations and changes in soil stiffness subject to these loadings conditions. Design guidance on the issue is limited, so are the availability of laboratory and field test data. The interpretation of these results in sand, such as the relation between loading and displacement, relies mainly on empirical correlations to pile properties. Regarding numerical models, most data from Finite Element Method (FEM) can be found. They are not comprehensive, and most of the FEM results are sensitive to input parameters. The micro scale behaviour could change the mechanism of the soil-structure interaction. A DEM model was used in this paper to study the cyclic lateral loads behaviour. A non-dimensional framework is presented and applied to interpret the simulation results. The DEM data compares well with various set of published experimental centrifuge model test data in terms of lateral deflection. The accumulated permanent pile lateral displacements induced by the cyclic lateral loads were found to be dependent on the characteristics of the applied cyclic load, such as the extent of the loading magnitudes and directions.
Abstract: Experimental and analytical studies were carried out to investigate the structural behavior of precast foamed concrete sandwich panels (PFCSP) of total number (6) as one-way action slab tested under lateral load. The details of the test setup and procedures were illustrated. The results obtained from the experimental tests were discussed which include the observation of cracking patterns and influence of aspect ratio (L/b). Analytical study of finite element analysis was implemented and degree of composite action of the test panels was also examined in both experimental and analytical studies. Result shows that crack patterns appeared in only one-direction, similar to reports on solid slabs, particularly when both concrete wythes act in a composite manner. Foamed concrete was briefly reviewed and experimental results were compared with the finite element analyses data which gives a reasonable degree of accuracy. Therefore, based on the results obtained, PFCSP slab can be used as an alternative to conventional flooring system.
Abstract: A 15-storey RC building, studied in this paper, is
representative of modern building type constructed in Madina City in
Saudi Arabia before 10 years ago. These buildings are almost
consisting of reinforced concrete skeleton i.e. columns, beams and
flat slab as well as shear walls in the stairs and elevator areas
arranged in the way to have a resistance system for lateral loads
(wind – earthquake loads). In this study, the dynamic properties of
the 15-storey RC building were identified using ambient motions
recorded at several, spatially-distributed locations within each
building. Three dimensional pushover analysis (Nonlinear static
analysis) was carried out using SAP2000 software incorporating
inelastic material properties for concrete, infill and steel. The effect
of modeling the building with and without infill walls, on the
performance point as well as capacity and demand spectra due to EQ
design spectrum function in Madina area has been investigated. ATC-
40 capacity and demand spectra are utilized to get the modification
factor (R) for the studied building. The purpose of this analysis is to
evaluate the expected performance of structural systems by
estimating, strength and deformation demands in design, and
comparing these demands to available capacities at the performance
levels of interest. The results are summarized and discussed.
Abstract: One of the main purposes of designing bucklingrestrained
braces is the fact that the entire lateral load is wasted by
the braces, the entire gravitational load is moved to the foundation
through the beams, and the columns can be moved to the foundation.
In other words, braces are designed for bearing lateral load. In the
implementation of the structure, it should be noted that the
implementation of various parts of the structure must be conducted in
such a way that the buckling-restrained braces would not bear the
gravitational load. Moreover, this type of brace has been investigated
under impact loading, and the design goals of designing method
(direct motion) are controlled under impact loading. The results of
dynamic analysis are shown as the relocation charts of the floors and
switch between the floors. Finally, the results are compared with each
other.
Abstract: In this study, a general approach to the reliability
based limit analysis of laterally loaded piles is presented. In
engineering practice the uncertainties play a very important role. The
aim of this study is to evaluate the lateral load capacity of free-head
and fixed-head long pile when plastic limit analysis is considered. In
addition to the plastic limit analysis to control the plastic behaviour
of the structure, uncertain bound on the complementary strain energy
of the residual forces is also applied. This bound has significant effect
for the load parameter. The solution to reliability-based problems is
obtained by a computer program which is governed by the reliability
index calculation.
Abstract: The paper aims at investigating the effect of number
of story on different structural components of reinforced concrete
building due to gravity and lateral loading. For the study, three
building models having same building plan of three, six and nine
stories are analyzed and designed using software package. All the
buildings are residential and are located in Dhaka city of Bangladesh.
Lateral load including wind and earthquake loading are applied to the
building along both longitudinal and transverse direction as per
Bangladesh National Building Code (BNBC, 2006). Equivalent static
force method is followed for the applied seismic loading. The present
study investigates as well as compares mainly total steel requirement
in different structural components for those buildings. It has been
found that total longitudinal steel requirement for beams at each floor
is 48.57% for three storied building, 61.36% for six storied building
when the total percentage is taken as 100% in case of nine storied
building. For an exterior column, the steel ratio is 2.1%, 3.06%,
4.55% for three, six and nine storied building respectively for the first
three floors. In addition, it has been noted that total weight of
longitudinal reinforcement of an interior column is 14.02 % for threestoried
building and 43.12% for six storied building when the total
reinforcement is considered 100% for nine storied building for the
first three floors.
Abstract: Environmental and functional conditions, sometimes,
necessitate the architectural plan of the building to be asymmetric,
and this result in an asymmetric structure. In such cases finding an
optimal pattern for locating the components of lateral load bearing
system, including shear walls, in the building’s plan is desired. In
case of shear wall in addition to the location the shape of the wall
cross-section is also an effective factor. Various types of shear walls
and their proper layout might come effective in better stiffness
distribution and more appropriate seismic response of the building.
Several studies have been conducted in the context of analysis and
design of shear walls; however, few studies have been performed on
making decisions for the location and form of shear walls in multistory
buildings, especially those with irregular plan. In this study, an
attempt has been made to obtain the most reliable seismic behavior of
multi-story reinforced concrete vertically chamfered buildings by
using more appropriate shear walls form and arrangement in 7-, 10-,
12-, and 15-stoy buildings. The considered forms and arrangements
include common rectangular walls and L-, T-, U- and Z-shaped plan,
located as the core or in the outer frames of the building structure.
Comparison of seismic behaviors of the buildings, including
maximum roof displacement and particularly formation of plastic
hinges and their distribution in the buildings’ structures, have been
done based on the results of a series of nonlinear time history
analyses, by using a set of selected earthquake records. Results show
that shear walls with U-shaped cross-section, placed as the building
central core, and also walls with Z-shaped cross-section, placed at the
corners give the building more reliable seismic behavior.
Abstract: This paper presents an experimental study on
structural performance of an innovative noise barrier consisting of
poly-block, light polyurethane foam (LPF) and polyurea. This wall
system (flexi-wall) is intended to be employed as a vertical extension
to existing sound barriers in an accelerated construction method. To
aid in the wall design, several mechanical tests were conducted on
LPF specimens and two full-scale walls were then fabricated
employing the same LPF material. The full-scale walls were
subjected to lateral loading in order to establish their lateral
resistance. A cyclic fatigue test was also performed on a full-scale
flexi-wall in order to evaluate the performance of the wall under a
repetitive loading condition. The result of the experiments indicated
the suitability of flexi-wall in accelerated construction and confirmed
that the structural performance of the wall system under lateral
loading is satisfactory for the sound barrier application. The
experimental results were discussed and a preliminary design
procedure for application of flexi-wall in sound barrier applications
was also developed.
Abstract: The use of energy dissipation systems for seismic applications has increased worldwide, thus it is necessary to develop practical and modern criteria for their optimal design. Here, a direct displacement-based seismic design approach for frame buildings with hysteretic energy dissipation systems (HEDS) is applied. The building is constituted by two individual structural systems consisting of: 1) a main elastic structural frame designed for service loads; and 2) a secondary system, corresponding to the HEDS, that controls the effects of lateral loads. The procedure implies to control two design parameters: a) the stiffness ratio (α=Kframe/Ktotal system), and b) the strength ratio (γ=Vdamper/Vtotal system). The proposed damage-controlled approach contributes to the design of a more sustainable and resilient building because the structural damage is concentrated on the HEDS. The reduction of the design displacement spectrum is done by means of a damping factor (recently published) for elastic structural systems with HEDS, located in Mexico City. Two limit states are verified: serviceability and near collapse. Instead of the traditional trial-error approach, a procedure that allows the designer to establish the preliminary sizes of the structural elements of both systems is proposed. The design methodology is applied to an 8-story steel building with buckling restrained braces, located in soft soil of Mexico City. With the aim of choosing the optimal design parameters, a parametric study is developed considering different values of હ and . The simplified methodology is for preliminary sizing, design, and evaluation of the effectiveness of HEDS, and it constitutes a modern and practical tool that enables the structural designer to select the best design parameters.
Abstract: Concentric bracing systems have been in practice for many years because of their effectiveness in reducing seismic response. Depending on concept, seismic design codes provide various response modification factors (R), which itself consists of different terms, for different types of lateral load bearing systems but configuration of these systems are often ignored in the proposed values. This study aims at considering the effect of different x-bracing diagonal configuration on values of ductility dependent term in R computation. 51 models were created and nonlinear push over analysis has been performed. The main variables of this study were the suitable location of X–bracing diagonal configurations, which establishes better nonlinear behavior in concentric braced steel frames. Results show that some x-bracing diagonal configurations improve the seismic performance of CBF significantly and explicit consideration of lateral load bearing systems seems necessary.
Abstract: This paper presents a comparative study of static analysis procedure for seismic performance based on UBC-1997 and SBC-301-2007(Saudi Arabia). These building codes define different ductility classes and corresponding response reduction factors based on material, configuration and detailing of reinforcements. Codes differ significantly in specifying the procedures to estimate base shear, drift and effective stiffness of structural members. One of the major improvements made in new SBC (based on IBC-2003) is ground motion parameters used for seismic design. In old SBC (based on UBC) maps have been based on seismic zones. However new SBC provide contour maps giving spectral response quantities. In this approach, a case study of RC frame building located in two different cities and with different ductility classes has been performed. Moreover, equivalent static method based on SBC-301 and UBC-1997 is used to explore the variation in results based on two codes, particularly design base shear, lateral loads and story drifts.
Abstract: Conventional concentrically-braced frame (CBF)
systems have limited drift capacity before brace buckling and related
damage leads to deterioration in strength and stiffness. Self-centering
concentrically-braced frame (SC-CBF) systems have been developed
to increase drift capacity prior to initiation of damage and minimize
residual drift. SC-CBFs differ from conventional CBFs in that the
SC-CBF columns are designed to uplift from the foundation at a
specified level of lateral loading, initiating a rigid-body rotation
(rocking) of the frame. Vertically-aligned post-tensioning bars resist
uplift and provide a restoring force to return the SC-CBF columns to
the foundation (self-centering the system). This paper presents a
parametric study of different prototype buildings using SC-CBFs.
The bay widths of the SC-CBFs have been varied in these buildings
to study different geometries. Nonlinear numerical analyses of the
different SC-CBFs are presented to illustrate the effect of frame
geometry on the behavior and dynamic response of the SC-CBF
system.
Abstract: Shear walls are used in most of the tall buildings for
carrying the lateral load. When openings for doors or windows are
necessary to be existed in the shear walls, a special type of the shear
walls is used called "coupled shear walls" which in some cases is
stiffened by specific beams and so, called "stiffened coupled shear
walls".
In this paper, a mathematical method for geometrically nonlinear
analysis of the stiffened coupled shear walls has been presented.
Then, a suitable formulation for determining the critical load of the
stiffened coupled shear walls under gravity force has been proposed.
The governing differential equations for equilibrium and deformation
of the stiffened coupled shear walls have been obtained by setting up
the equilibrium equations and the moment-curvature relationships for
each wall. Because of the complexity of the differential equation, the
energy method has been adopted for approximate solution of the
equations.
Abstract: Impact is one of very important subjects which always have been considered in mechanical science. Nature of impact is such that which makes its control a hard task. Therefore it is required to present the transfer of impact to other vulnerable part of a structure, when it is necessary, one of the best method of absorbing energy of impact, is by using Thin-walled tubes these tubes collapses under impact and with absorption of energy, it prevents the damage to other parts.Purpose of recent study is to survey the deformation and energy absorption of tubes with different type of cross section (rectangular or square) and with similar volumes, height, mean cross section thickness, and material under loading with different speeds. Lateral loading of tubes are quasi-static type and beside as numerical analysis, also experimental experiences has been performed to evaluate the accuracy of the results. Results from the surveys is indicates that in a same conditions which mentioned above, samples with square cross section ,absorb more energy compare to rectangular cross section, and also by increscent in speed of loading, energy absorption would be more.
Abstract: Earthquakes produce some of the most violent loading
situations that a structure can be subjected to and if a structure fails
under these loads then inevitably human life is put at risk. One of the
most common methods by which a structure fails under seismic
loading is at the connection of structural elements. The research
presented in this paper investigates the interlock systems as a novel
method for building structures. The main objective of this
experimental study wasto determine the dynamic characteristics and
the seismic behaviour of the proposed structures compared to
conventional structural systemsduring seismic motions. Results of
this study indicate that the interlock mechanism of the panels
influences the behaviour of lateral load-resisting systems of the
structures during earthquakes, contributing to better structural
flexibility and easier maintenance.
Abstract: Structural redundancy is an interesting point in
seismic design of structures. Initially, the structural redundancy is
described as indeterminate degree of a system. Although many definitions are presented for redundancy in structures, recently the
definition of structural redundancy has been related to the configuration of structural system and the number of lateral load
transferring directions in the structure. The steel frames with infill walls are general systems in the constructing of usual residential buildings in some countries. It is
obviously declared that the performance of structures will be affected by adding masonry infill walls. In order to investigate the effect of
infill walls on the redundancy of the steel frame which constructed
with masonry walls, the components of redundancy including redundancy variation index, redundancy strength index and
redundancy response modification factor were extracted for the
frames with masonry infills. Several steel frames with typical storey number and various numbers of bays were designed and considered.
The redundancy of frames with and without infill walls was evaluated by proposed method. The results showed the presence of infill causes increase of redundancy.
Abstract: Basic objective of this study is to create a regression
analysis method that can estimate the length of a plastic hinge which
is an important design parameter, by making use of the outcomes of
(lateral load-lateral displacement hysteretic curves) the experimental
studies conducted for the reinforced square concrete columns. For
this aim, 170 different square reinforced concrete column tests results
have been collected from the existing literature. The parameters
which are thought affecting the plastic hinge length such as crosssection
properties, features of material used, axial loading level,
confinement of the column, longitudinal reinforcement bars in the
columns etc. have been obtained from these 170 different square
reinforced concrete column tests. In the study, when determining the
length of plastic hinge, using the experimental test results, a
regression analysis have been separately tested and compared with
each other. In addition, the outcome of mentioned methods on
determination of plastic hinge length of the reinforced concrete
columns has been compared to other methods available in the
literature.
Abstract: Recent trends in building constructions in Libya are
more toward tall (high-rise) building projects. As a consequence, a
better estimation of the lateral loading in the design process is
becoming the focal of a safe and cost effective building industry. Byin-
large, Libya is not considered a potential earthquake prone zone,
making wind is the dominant design lateral loads. Current design
practice in the country estimates wind speeds on a mere random
bases by considering certain factor of safety to the chosen wind
speed. Therefore, a need for a more accurate estimation of wind
speeds in Libya was the motivation behind this study. Records of
wind speed data were collected from 22 metrological stations in
Libya, and were statistically analysed. The analysis of more than four
decades of wind speed records suggests that the country can be
divided into four zones of distinct wind speeds. A computer “survey"
program was manipulated to draw design wind speeds contour map
for the state of Libya.
The paper presents the statistical analysis of Libya-s recorded
wind speed data and proposes design wind speed values for a 50-year
return period that covers the entire country.
Abstract: Composite steel shear wall is a lateral load resisting system which consists of a steel plate with concrete wall attached to one or both sides to prevent it from elastic buckling. The composite behavior is ensured by utilizing high-strength bolts. This paper investigates the effect of distance between bolts, and for this purpose 14 one-story one-bay specimens with various bolts spacing were modeled by finite element code which is developed by the authors. To verify the model, numerical results were compared with a valid experiment which illustrate proper agreement. Results depict increasing the distance between bolts would improve the seismic ever, this increase must be limited, because of large distances will cause widespread buckling of the steel plate in free subpanels between bolts and would result in no improvement. By comparing the results in elastic region, it was observed initial stiffness is not affected by changing the distance.