Construction In Seismic Regions Research Articles

Investigating seismic behaviour of cold-formed steel moment frames with the welded through-plate flexural connection

The Cold-Formed Steel (CFS) construction in seismic regions requires carefully selecting and designing an approved seismic-force resisting system. Among the available seismically-resistant structural systems, the bolted CFS moment frames have recently gained some attention. However, given the currently existing design issues associated with the bolted connections in CFS moment frames, this paper seeks to conduct a numerical investigation into the potential substitution of bolt fasteners with the weld materials in CFS frames. The objective is to explore the possibility of including the welded connection as an alternative to bolted connections in subsequent editions of the ASCE 7 code. To this end, finite element models, consisting of two built-up CFS beams and twenty-three flare-bevel-groove and fillet weld specimens, are initially validated against the cyclically and monotonically loaded tests with data available in the relevant literature. Subsequently, the verified weld and CFS beam models are incorporated in the simulation of thirty-four CFS beam-to-column welded moment connections, each differing in beam dimension, weld length and size, and gusset plate thickness. The built-up beams comprise back-to-back and lip-to-lip double C-section profiles. Stress variations along the weld lines, derived initially from nonlinear finite element analyses and then computed from the theoretical elastic analysis, are compared to establish a basis for categorizing stress distribution patterns in the longitudinal welds. Finally, six CFS frames assembled with the welded moment connection and subjected to a combined column axial compression and cyclic lateral drift are examined, resulting in an estimated seismic modification coefficient, R, equal to 3.8. Overall, the welded moment connections demonstrate a stable seismic response with an average ductility ratio, μ, of 2.7. The dominant failure mode is a locally developed ductile fracture in the two end segments of the longitudinal welds, identified as critical regions.

Seismic Mitigation Effect of Lever-Type Lead Viscoelastic Node Dampers

Energy dissipation damping technology is usually used for infrastructure construction in seismic regions. In this study, a lever-type lead viscoelastic node damper (LTLVND), which can capture small rotational displacements of the infrastructure under seismic excitation, is innovatively proposed based on the leverage effect. The characteristics of energy-absorbing capacity of the LTLVND and its mitigation effect on the dynamics of the structure under seismic excitation are studied. Testing and modelling results show that a satisfactory energy dissipation effect can be observed for the innovative lead viscoelastic damper (LTLVND). Finally, a seismic analysis of a concrete frame structure with LTLVNDs is carried out. Pushover analysis and dynamic elastoplastic analysis are included. It is shown that a significant improvement in structural performance under seismic conditions can be achieved with the addition of LTLVNDs at appropriate locations.

A Fully Precast Pier System for Accelerated Bridge Construction in Seismic Regions

A Fully Precast Pier System for Accelerated Bridge Construction in Seismic Regions

Comparative Analysis of Seismic Design Codes for Shallow Foundations Adhering to the Kazakhstani and European Approaches

Since 2015 the transition from the traditional seismic design regulation to the newly developed code of practice has been initiated in Kazakhstan. The introduced regulatory system involves the application of the European approach for the seismic design of buildings and structures on the territory of Kazakhstan. This study aims to present a comparative analysis of seismic design codes applied in Kazakhstan (i.e., SP RK 5.01-102-2013* Foundations of Buildings and Structures and SP RK 2.03-30-2017* Construction in Seismic Regions) and SP RK EN 1998-5:2004/2012 Design of Structures for Earthquake Resistance, identical to Eurocode 8 (EC8). One of the critical aspects of the research investigates the difficulties of integrating European design standards into the local regulatory system. The necessity of applying the European approach considering the geotechnical features of the country provided in the National Annex (NA) is defined and proved. The designed codes of practice are also compared in terms of conservativeness, when considering a design problem verifying the seismic bearing capacity of a shallow foundation in Almaty city.

FEATURES OF THE DESIGN OF STEEL EARTHQUAKE-RESISTANT STRUCTURES OF HIGH-RISE BUILDINGS

The design, construction and operation of buildings in Ukraine is associated with the need to take into account additional special loads and impacts, namely: seismic, in complex en-gineering and geological conditions, on weak soils, artificial territories and subsidence soils, and in the conditions of the war with Russia during missile and artillery shelling and bom-bardment of populated areas – effects from explosions, blast waves, spread of fires, etc. [3].
 The territory of Ukraine is located on the outskirts of the powerful Azores-Mediterranean-Alpine-Trans-Asian seismogenic belt of the planet. In general, Ukraine does not belong to particularly seismically dangerous regions of the planet. Low- and medium-magnitude (magnitude 3...6) earthquakes were recorded only within three of its regions: the Ukrainian Carpathians and the Crimean Moun-tains, the Azov region. But observations of the consequences of numerous earthquakes have shown that in different parts of the same seis-mic area they differ significantly in intensity. Thus, the intensity of the earthquake on the surface of the earth in areas with loose soils is 15 times greater than in areas with rocky ones. Therefore, during the design of buildings and structures, one should take into account the peculiarities of construction in the complex engineering and geological conditions of the territory of Ukraine, which are associated with research, design and arrangement of bases and foundations on weak water-saturated, clayey and peaty soils, peat and silt, subsidence, swell-ing, saline, swelling and unevenly compacted soils, loose sands and floating karst and forged territories, taking into account seismic and dy-namic action in compliance with the require-ments of DBN B.1.1-12:2014 "Construction in seismic regions of Ukraine" [5] and DBN V.1.1-45:2017 "Buildings and structures in difficult engineering and geological conditions. General Provisions" [6].
 The design of modern buildings in seismic areas is developing in two directions that corre-spond to the main principles of seismic protec-tion - traditional (passive) and special (active). Complex systems of seismic protection of buildings combine passive and active systems.
 With traditional seismic protection, the load-bearing capacity of the main load-bearing structures of buildings is increased (the dimen-sions of cross-sections, their reinforcement, strengthening of joints, etc.) to absorb addition-al forces caused by seismic influences. At the same time, the nature of the buildings does not change. Special (active) measures to improve the seismic resistance of buildings consist in reducing loads due to modifications of their dynamic work schemes. Active seismic protec-tion of buildings is a new direction, which con-sists in the implementation of additional con-structive measures to prevent dangerous reso-nant oscillations and thereby reduce seismic impacts. It is achieved by changing the dynam-ic stiffness or periods of natural oscillations of buildings during earthquakes as a result of the use of special structural devices: sliding belts, connections that can be turned on or off, instal-lation of dynamic vibration dampers, kinematic or pile foundations, which have dissipative characteristics of self-organization, frame-linking systems with complex stiffness dia-phragms, rubber-steel cylindrical supports, etc.The article analyzes the features of design-ing earthquake-resistant steel structures of high-rise buildings. The schemes of earthquake-resistant high-rise buildings with steel frames were studied. The feasibility of using steel en-ergy-absorbing elements is substantiated and schemes for their installation in earthquake-resistant buildings with steel frames are pre-sented.

Simplified analytical models for partially grouted reinforced masonry shear walls

Partially grouted (PG) masonry shear walls have commonly been used for construction in seismic regions. However, predicting their behaviour is quite complicated due to the non-uniformity presented by the materials’ variety. In this paper, an extensive analytical study was carried out to establish simplified backbone models referred here as “analytical models” as a first attempt in the literature to simulate PG masonry walls’ behaviour. A nonlinear finite element model was developed and validated against several experimental specimens from the literature. The numerical model was then utilized to compensate for the lack of experimental data by generating a comprehensive matrix of 196 numerical models covering a wide range of design and detailing parameters. These parameters include the aspect ratio, the spacing between vertical and horizontal grouted cells, the axial load, the ratio of vertical and horizontal reinforcement, and the compressive strength of grouted and ungrouted masonry units. Subsequently, three penta-linear load–displacement backbone models were proposed using linear regression analysis. Five secant stiffness expressions, namely: cracking, yielding, ultimate, 20% strength reduction, and 40% strength reduction, were derived to define the backbone curve of each wall category. Consequently, the proposed analytical models were examined against samples from the numerical matrix and the experimental specimens, which were not considered in the calibration of the analytical models. The results showed that the proposed analytical models provide good predictions of the response of PG masonry walls. Finally, the stiffness reduction factor provided by CSA S304-14 for masonry, α, was updated by developing three new coefficients for the PG walls’ categories based on regression analyses between the numerical stiffnesses at yielding and their corresponding values calculated using α.

Experimental testing of hybrid sliding‐rocking bridge columns under torsional and biaxial lateral loading

AbstractHybrid sliding‐rocking (HSR) bridge columns are precast concrete segmental columns with unbonded posttensioning, end rocking joints, and intermediate sliding joints. Having been developed for construction in seismic regions, HSR columns offer self‐centering, energy dissipation, and low damageability. Recent advances in the computational modeling of HSR columns have resulted in the proposal of a number of refinements to their original design, leading to the introduction of Second‐Generation HSR columns. Compared to First‐Generation HSR columns, Second‐Generation HSR columns use a reduced number of sliding joints made of high‐performance polytetrafluoroethylene (PTFE) materials to provide desirable levels of sliding and frictional energy dissipation. The seismic performance of Second‐Generation HSR columns was recently investigated through an extensive experimental study. The present paper discusses the major results of the tests performed on two half‐scale HSR column specimens under combined lateral‐torsional loading and biaxial lateral loading to demonstrate their performance under such loading scenarios. A variety of loading protocols were used to test each column specimen, including both cyclic and arbitrary paths. Both columns sustained minimal damage under displacement demands representing 975‐ and 2475‐year seismic hazards, meeting their design objectives. Because of the torsional sliding at sliding joints, the column subjected to lateral‐torsional loading did not exhibit any distinct torsional damage. The biaxial lateral loading was, however, found more damaging to HSR columns than torsional and uniaxial lateral loading.

Application of Modified Peat Aggregate for Lightweight Concrete

The scientific article "Application of Modified Peat Aggregate for Lightweight Concrete" presents the results of studies of the properties of a new composite material for use in enclosing structures of residential and public buildings. Physical and mechanical characteristics of possible aggregates of local production for this type of concrete affecting its operational properties are considered. The prospects of using fly ash as an additive improving the characteristics of polystyrene concrete with the addition of modified peat have been established. The analysis was made and the optimal compositions for obtaining lightweight concrete based on peat and polystyrene foam were selected. The desorption properties of lightweight concrete important for its effective operation as a wall material were tested. It was found that the use of new types of surfactants can improve the water wettability of peat particles and polystyrene granules, thereby reducing the water-cement ratio and improving the compressive strength of the material. Possible efficiency of application of this type of concrete for use in enclosing structures of buildings and constructions under construction in seismic regions of Russia is considered. The presence of damping effect manifested in the material due to the presence of polystyrene granules in the perception of a certain level of load, which is important for the work of concrete under seismic influences, was experimentally established.

Retraction Note: On the seismic performance of bamboo structure

While the earthquake resistant building design and construction code has been developed in sophisticated national/city level, the implementation at the local level has been more of an exception than the rule. Other than concrete and steel, one such material that can be used in construction in the seismic zone area of the developing countries like India, especially in the northeast states, is bamboo, where bamboo is available in abundant. Bamboo’s light weight and relative flexibility make it a particularly attractive alternative for residential construction in seismic regions. Compared on a mass-per-volume basis to concrete, steel and wood, bamboo is second to concrete for strength, and ranks first for stiffness. As strong as mild steel with the compression strength of concrete, amazingly, one inch of bamboo can hold up to 7 1/2 tons of weight. This present study is an attempt to implement bamboo construction in Manipur which is regarded as one of the most seismically active regions worldwide. In this work, a bamboo housing system and a reinforced concrete frame structural system was modeled using finite element analysis program SAP, considering the model structures to be taken from the types of building that is built in Manipur. A parametric study is conducted to investigate the seismic performance of the structures and El-Centro Earthquake and Kobe Earthquake recorded excitation are used for input in the dynamic analysis on the models. The study has revealed that the bamboo structures are performing better in earthquake than the commonly built RC residential building. The behavior of the bamboo structure modeled in this present study gives an opportunity to accept bamboo as a construction material in seismic zone areas.

Anti-Seismic Bracing in a Hollow-Core Slab of Formwork-Free Shaping for The Possibility of Creating a Rigid Disk in a Building Floor Slab

Building codes and regulations for construction in seismic regions of many countries (including Uzbekistan) require that the floors slabs and elements of a building should possess resistance to seismic impacts, have such functions that not only distribute seismic load between the supporting elements of the building (walls, crossbars and frame columns), but also ensure the spatial operation of the building as a result of reliable bracing of these elements. Therefore, floor slabs made of reinforced concrete prefabricated elements must present rigid horizontal diaphragms (disks) that uniformly distribute seismic loads between load-bearing structures. To fulfill the above requirements, the building standards of Uzbekistan KMK 2.01.03-96 “Construction in seismic areas” oblige designers to provide the strength and rigidity of floors slabs of buildings (structures) by installation the anti-seismic bracings in inter-slab joints between the side surfaces of adjacent slabs; between the end supporting sections of slabs and the frame elements or the anti-seismic belts of stone buildings. The same standards require the presence of free lengths of reinforcement bars or concrete inserts at the ends of slabs for connecting floor slabs with each other and with an anti-seismic belt (or a framing beam); these requirements apply to the production of floor slabs using the aggregate-flow technology. An installation of bracing elements for hollow-core slabs of formwork-free shaping with adjacent structures is not provided since the slabs of a set length are fabricated on a production line by cutting a molded monolithic tape on the line. In this regard, hollow-core slabs of formwork-free shaping must have anti-seismic joint units that provide the bearing capacity of building structures of various systems at the stages of their life cycle. Typical solutions of such units for hollow-core slabs of formwork-free shaping have not been developed. An anchor node with a unit in the void at the end section of the slab has been developed for the anti-seismic bracing of a hollow-core floor slab of formwork-free shaping with adjacent building structures (through a seismic belt or a framing beam). For anti-seismic bracing in inter-slab joints between the lateral surfaces of adjacent floor slabs, a constructive solution is proposed for the cross section of a hollow-core slab of formwork-free shaping with a widened lower flange relative to the upper flange to install a reinforced concrete framing beam in the inter-slab joints. This creates a rigid disk in the building floors. Tests for pulling out anchor rods from nodes arranged in voids at the end sections of a hollow-core slab of formwork-free shaping assessed the strength and serviceability of the proposed antiseismic coupling units. The pulling out of the anchor rods in all tested units occurred before the loss of cohesive strength in the contact zone “concrete of the body of anchor unit - concrete of the slab”. The use of hollow-core slabs of formwork-free shaping with a widened lower flange relative to the upper flange greatly simplifies the installation of reinforced concrete framing beams in the inter-slab joints of buildings. A useful model was patented in the Intellectual Property Agency of the Republic of Uzbekistan; a constructive solution was proposed for a hollow-core slab of formwork-free shaping with a widened lower flange relative to the upper flange, application number FAP20180174 with priority date 11/08/2018. The proposed solutions for the anti-seismic ties of a hollow-core slab of formwork-free shaping with a building structure meet the requirements of the building codes of Uzbekistan KMK 2.01.03-96 “Construction in seismic areas” for transforming a floor slab made from prefabricated plates into a continuous beam slab to create a rigid horizontal diaphragm. The arrangement of the proposed anti-seismic connecting units in a hollow-core slab of formwork-free shaping does not change the manufacturing technology of this type of slabs, and allows the creation of a wide range of products for buildings and structures with various architectural, planning and structural solutions that increase the possibilities of housing, civil and industrial construction in seismic areas.

Probabilistic Estimation Seismic Resistance of Plain Steel Frame

The purpose of the study is to estimate the coefficient K1, which considers the permissible damage to buildings and structures in a probabilistic formulation. For the study, a flat steel frame was designed in accordance with SP 14.13330.2014 “Construction in seismic regions”. The frame calculation was performed in the LS-DYNA software package in a nonlinear dynamic formulation for a set of synthesized accelerograms. The set of accelerograms represents 50 implementations of random earthquake action with a fixed mathematical expectation of the dominant frequency. By gradually increasing the intensity of the action, the frame was brought to fracture in a numerical experiment, the results of which determined the safety margin of load-bearing capacity at each implementation. Further, by considering the safety margin and coefficient K1, their average values were determined. The obtained results showed that the actual coefficient K1 for the structure under study is significantly lower than its standard value, and the steel structure under consideration has a significant margin of seismic resistance. Thus, the developed method enables to estimate the actual value of the coefficient K1.

Prefabricated hybrid steel wall panels for mid-rise construction in seismic regions

Light steel framing systems are increasingly used in a variety of low-rise buildings, while are gradually penetrating to the mid-rise residential construction. The increased demand for mid-rise light weight steel frames in recent years has resulted in various research activities being undertaken in order to enhance the performance of these systems in compliance with the increased demands of mid-rise construction. This paper investigates the performance of a hybrid wall panel system (HWPS) made of a hot-rolled steel panel and a cold-formed steel panel in seismic regions. The hot-rolled steel panel resists the shear force, while the gravity load is distributed proportionally between the hot-rolled and cold-formed panels. The research employs the results of an experimental program to investigate the performance of the proposed hybrid panel, and a numerical study on the seismic performance of a 4-storey building made by HWPS. A practical design procedure is suggested for the system according to relevant specifications, and the results are compared with those obtained from employing a fully hot-rolled steel frame (moment resisting frame) and then a fully CFS frame system. The structural performance and the construction cost of two systems are then compared.

Seismic performance and design of bridge column‐to‐pile shaft pipe‐pin connections in precast and cast‐in‐place bridges

SummaryHinge or “pin” connections may be used in integral bridges to connect columns to pile shafts to reduce the foundation force demand. Used in combination with prefabricated columns, pins facilitate accelerated bridge construction (ABC). These innovative methods could improve the quality and economy of project compared with conventional construction in seismic regions. This study developed pipe pins that reduce moment transfer between the column and pile shaft under seismic excitations. The pipe pins consist of two steel pipes and a rod that transfer shear and tension while allowing rotation between the column and shaft. The primary objective of this research was to investigate the seismic performance and develop design guidelines of column‐to‐pile shaft pipe pins for cast‐in‐place and precast constructions. This research was composed of experimental and analytical studies. The experimental portion of the study consisted of testing of a large‐scale bent model subjected to seismic loadings. The test results confirmed that the proposed design method meets the safety and performance requirements of the codes under seismic loadings. The pins maintained structural integrity with minimal damage, while the columns reached the full plastic hinge capacity. The analytical studies consisted of (a) a simple stick model to be used as a design tool, (b) a finite element model (FEM) for global analysis of bridges, and (c) an elaborate FEM to investigate the microscopic performance and interaction of the components. The analytical models were subsequently used in parametric studies.

Seismic behavior of autoclaved aerated concrete low rise buildings with reinforced wall panels

Reinforced Autoclaved Aerated Concrete (AAC) wall panels are more commonly used to construct load-bearing walls in low-rise prefabricated buildings located in seismic zones. In the scope of this study, the seismic response of buildings constructed with reinforced AAC wall panels was investigated. To this end, an in situ test was conducted on a two-story test building under reversed cyclic displacement excursions. It was determined that the test building could carry a lateral load of 60% more than its weight and has a global displacement ductility of about 3.5. The first story of the building was observed to be critical and the failure of the building was due to overturning response of the whole system. In addition, the proposed numerical models for simulating the behavior of the AAC wall panels were validated. These calibrated numerical models were utilized to conduct nonlinear static analysis of the test building and a reasonably good agreement was observed between the test results and simulations. The results of the incremental dynamic analyses demonstrated that i) the two-story test building could resist strong ground motions with PGA values up to 0.6 g without undergoing significant plastic deformations and ii) a reserve of ductility and over strength is available for the AAC panel building to survive earthquakes with PGAs reaching nearly 0.6 g. Based on these numerical results, reinforced AAC wall panel buildings appear to be good alternatives for low-rise construction in seismic regions.

Hysteretic behavior investigation of self-centering double-column rocking piers for seismic resilience

Seismic resilient structures with low structural damage and self-centering behavior after an earthquake are focus issues of current earthquake engineering. Unbonded pretensioned rocking columns offer advantages for accelerated bridge construction in seismic regions, which utilize column-uplifting mechanisms, high strength post-tensioning, and replaceable energy dissipation devices to enhance seismic performance and resilience. The experiment of three 1:3 scale unbonded, post-tensioned rocking bridge bents with different types of external replaceable energy dissipation devices subjected to quasi-static loading protocols, were carried out according to practical engineering demand in high-intensity earthquake regions. An improved analytical model was proposed for predicting the force-displacement relationship of the post-tensioned rocking bridge bent systems considering the neutral axis depth. Minimal physical damage was observed for the post-tensioned rocking bridge bent systems, which exhibit good energy dissipation and self-centering behavior. Especially, the external replaceable buckling-restrained plates dissipaters can be easily replaced if severely damaged subjected to higher than expected ground motions. The satisfactory analytical and experimental comparisons are presented as a validation of the reliability for the high-performance seismic-resistant bridge bent systems and the modelling techniques in this study.

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

Impact of physical seismic damage on the fire resistance of reinforced concrete walls

Numerical simulations are conducted to investigate the impact of physical seismic damage on the fire resistance of (steel) reinforced concrete (RC) structural walls. A wall with characteristics representative of typical construction in seismic regions is utilized as the basis of the simulations. A two-story wall is considered, with lateral restraint at all floors and at the top only to simulate loss of restraint from floor slabs. The behavior of an undamaged wall is assessed relative to the behavior of slices of walls typically explored in simulation studies. The non-uniform layout of reinforcement is shown to provide a complex deformed shape. Individual damage states, representative of damage observed following earthquakes and in laboratory tests, are introduced to the wall to assess impact on fire resistance. Cracking is shown to have a greater impact on the thermal-insulation fire resistance than on the load-bearing fire resistance. Cover loss or core concrete crushing in the boundary elements or web is shown to result in the possibility of increased out-of-plane deformations and decreased fire resistance. The location of cover loss has remarkable impact on the deformed shape of a wall and its load-bearing fire resistance. Lateral restraint at the floors provides significant support that minimizes the effects of damage on the load-bearing fire resistance. While the load-bearing fire resistance is reduced by damage in the wall studied, fire resistance times are not of concern; however additional studies would be warranted for thin walls and walls with large axial load ratios.

Capacity Spectrum Seismic Design Methodology for Bridges with Hybrid Sliding-Rocking Columns

AbstractBridges with hybrid sliding-rocking (HSR) columns offer an attractive alternative for accelerated construction in seismic regions. HSR columns include internal unbonded post-tensioning, end...

Time Analysis of Building Dynamic Response Under Seismic Action. Part 2: Example of Calculation

The second part of the article illustrates the use of the time analysis method (TAM) by the example of the calculation of a 3-storey building, the design dynamic model (DDM) of which is adopted in the form of a flat vertical cantilever rod with 3 horizontal degrees of freedom associated with floor and coverage levels. The parameters of natural oscillations (frequencies and modes) and the results of the calculation of the elastic forced oscillations of the building’s DDM – oscillograms of the reaction parameters on the time interval t ∈ [0; 131,25] sec. The obtained results are analyzed on the basis of the computed values of the discrepancy of the DDS motion equation and the comparison of the results calculated on the basis of the numerical approach (FEM) and the normative method set out in SP 14.13330.2014 “Construction in Seismic Regions”. The data of the analysis testify to the accuracy of the construction of the computational model as well as the high accuracy of the results obtained. In conclusion, it is revealed that the use of the TAM will improve the strength of buildings and structures subject to seismic influences when designing them.

Unbonded Pretensioned Columns for Accelerated Bridge Construction in Seismic Regions

Unbonded Pretensioned Columns for Accelerated Bridge Construction in Seismic Regions