Influence of soil——structure interaction on seismic collapse resistance of super-tall buildings

Numerous field tests indicate that the soilestructure interaction （SSI） has a significant impact on thedynamic characteristics of super-tall buildings, which may lead to unexpected structural seismic responsesand/or failure. Taking the Shanghai Tower with a total height of 632 m as the research object, thesubstructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower. Therefined finite element （FE） model of the superstructure of Shanghai Tower and the simplified analyticalmodel of the foundation and adjacent soil are established. Subsequently, the collapse process of ShanghaiTower taking into account the SSI is predicted, as well as its final collapse mechanism. The influences ofthe SSI on the collapse resistance capacity and failure sequences are discussed. The results indicate that,when considering the SSI, the fundamental period of Shanghai Tower has been extended significantly,and the collapse margin ratio has been improved, with a corresponding decrease of the seismic demand.In addition, the SSI has some impact on the failure sequences of Shanghai Tower subjected to extremeearthquakes, but a negligible impact on the final failure modes. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Simulation of the response of base-isolated buildings under earthquake excitations considering soil flexibility

The accurate analysis of the seismic response of isolated structures requires incorporation of the flexibility of supporting soil. However, it is often customary to idealize the soil as rigid during the analysis of such structures. In this paper, seismic response time history analyses of base-isolated buildings modelled as linear single degree-of-freedom （SDOF） and multi degree-of-freedom （MDOF） systems with linear and nonlinear base models considering and ignoring the flexibility of supporting soil are conducted. The flexibility of supporting soil is modelled through a lumped parameter model consisting of swaying and rocking spring-dashpots. In the analysis, a large number of parametric studies for different earthquake excitations with three different peak ground acceleration （PGA） levels, different natural periods of the building models, and different shear wave velocities in the soil are considered. For the isolation system, laminated rubber bearings （LRBs） as well as high damping rubber bearings （HDRBs） are used. Responses of the isolated buildings with and without SSI are compared under different ground motions leading to the following conclusions： （1） soil flexibility may considerably influence the stiff superstructure response and may only slightly influence the response of the flexible structures; （2） the use of HDRBs for the isolation system induces higher structural peak responses with SSI compared to the system with LRBs; （3） although the peak response is affected by the incorporation of soil flexibility, it appears insensitive to the variation of shear wave velocity in the soil; （4） the response amplifications of the SDOF system become closer to unit with the increase in the natural period of the building, indicating an inverse relationship between SSI effects and natural periods for all the considered ground motions, base isolations and shear wave velocities; （5） the incorporation of SSI increases the number of significant cycles of large amplitude accelerations for all the stories, especially for earthquakes with low and moderate PGA levels; and （6） buildings with a linear LRB base-isolation system exhibit larger differences in displacement and acceleration amplifications, especially at the level of the lower stories.

Influence of spiral anchor composite foundation on seismic vulnerability of raw soil structure

A typical single-layer raw soil structure in villages and towns in China is taken as the research object.In the probabilistic seismic demand analysis,the seismic demand model is obtained by the incremental dynamic time history analysis method.The seismic vulnerability analysis is carried out for the raw soil structure of nonfoundation,strip foundation,and spiral anchor composite foundation,respectively.The spiral anchor composite foundation can reduce the seismic response and failure state of raw soil structure,and the performance level of the structure is significantly improved.Structural requirements sample data with the same ground motion intensity are analyzed by linear regression statistics.Compared with the probabilistic seismic demand model under various working conditions,the seismic demand increases gradually with the increase of intensity.The seismic vulnerability curve is summarized for comparative analysis.With the gradual deepening of the limit state,the reduction effect of spiral anchor composite foundation on the exceedance probability becomes more and more obvious,which can reduce the probability of structural failure to a certain extent.

Extended consecutive modal pushover procedure for estimating seismic responses of one-way asymmetric plan tall buildings considering soil-structure interaction

Performance based design becomes an effective method for estimating seismic demands of buildings. In asymmetric plan tall building the effects of higher modes and torsion are crucial. The consecutive modal pushover （CMP） procedure is one of the procedures that consider these effects. Also in previous studies the influence of soil-structure interaction （SSI） in pushover analysis is ignored. In this paper the CMP procedure is modified for one-way asymmetric plan mid and high-rise buildings considering $SI. The extended CMP （ECMP） procedure is proposed in order to overcome some limitations of the CMP procedure. In this regard, 10, 15 and 20 story buildings with asymmetric plan are studied considering SSI assuming three different soil conditions. Using nonlinear response history analysis under a set of bidirectional ground motion; the exact responses of these buildings are calculated. Then the ECMP procedure is evaluated by comparing the results of this procedure with nonlinear time history results as an exact solution as well as the modal pushover analysis procedure and FEMA 356 load patterns. The results demonstrate the accuracy of the ECMP procedure.

Seismic Evaluation of Steel Moment Resisting Frames (MRFs)—Supported by Loose Granular Soil

Soil underneath a structure might affect the behavior and the overall response of the structure in seismic events. The role of loose soil conditions and the inclusion of soil-structure interaction (SSI) in the analysis are important issues that need to be addressed. Since steel structures are light, two configurations designed as spatial and perimeter are considered to study the effect of soil on the steel structural frames for the same building. The paper provides a parametric analysis on the influence of SSI on the overall performance of MRFs (Moment Resisting Frames) according to the provisions of Saudi Building Code (SBC) [1]. A case study has been developed in which spatial and perimeter moment resisting frames of 12, 6 and 3 stories residential buildings are designed using Saudi Building Code (SBC) prescriptions. A modal response spectrum analysis has been carried out to see the influence of SSI on the fundamental period of vibration, top story displacement and inter-story drift limitations. Moreover, a static non-linear analysis has been performed to investigate the performance of frames, thus allowing to identify the influence of SSI on the structural design of steel MRFs.

Seismic response of tall building considering soil-pile-structure interaction

The seismic behavior of tall buildings can he greatly affected by non-linear soil-pile interaction during strong earthquakes.In this study a 20-storey building is examined as a typical structure supported on a pile foundation for different conditions:(1) rigid base,i.e.no deformation in the foundation:(2) linear soil-pile system;and (3) nonlinear soil-pile system. The effects of pile foundation displacements on the behavior of tall building are investigated,and compared with the behavior of buildings supported on shallow foundation.With a model of non-reflective boundary between the near field and far field, Novak's method of soil-pile interaction is improved.The computation method for vibration of pile foundations and DYNAN computer program are introduced comprehensively.A series of dynamic experiments have been done on full-scale piles, including single pile and group,linear vibration and nonlinear vibration,to verify the validity of boundary zone model.

Earthquake induced pounding between adjacent buildings considering soil-structure interaction

Many closely located adjacent buildings have suffered from pounding during past earthquakes because they vibrated out of phase. Furthermore, buildings are usually constructed on soil; hence, there are interactions between the buildings and the underlying soil that should also be considered. This paper examines both the interaction between adjacent buildings due to pounding and the interaction between the buildings through the soil as they affect the buildings＇ seismic responses. The developed model consists of adjacent shear buildings resting on a discrete soil model and a linear visco- elastic contact force model that connects the buildings during pounding. The seismic responses of＇ adjacent buildings due to ground accelerations are obtained for two conditions： fixed-based （FB） and structure-soil-structure interaction （SSSI）. The results indicate that pounding worsens the buildings＇ condition because their seismic responses are amplified after pounding. Moreover, the underlying soil negatively impacts the buildings＇ seismic responses during pounding because the ratio of their seismic response under SSSI conditions with pounding to those without pounding is greater than that of the FB condition.

Production and Characterization of Pozzolan with Raw Clay from Burkina Faso

Four raw deposits clayey materials in Burkina Faso have been characterized using X-ray diffraction, infrared spectroscopy and ICP-AES to evaluate their suitability to be used as pozzolan in cement. The samples have been activated by thermal treatment at 730°C during 5 hours. The obtained metakaolin was investigated by means of complementary techniques for their use as pozzolan in building materials. Fineness, surface area and amorphousness of metakaolins were the dominant factors which influenced their pozzolan reactivity. The compressive strengths of blended specimens were slightly increased with metakaolins named MK1 and MK2 than the reference for the substitution of 20 - 25 wt%. This was due to the metakaolins’ pozzolan reactivity and their filler effects which promoted CSH formation and reduced pores in the specimens. MK1 and MK2 were suitable for replacement of Portland cement in the field of building materials.

A New Mode of Coal Mining Under Buildings with Paste-Like Backfill Technology

The formation of the paste like backfill technology was introduced briefly in this paper. From the actual cases of coal mines, a new mode of coal mining under buildings with the technology was proposed. And its specificity was analyzed, and a further introduction to the full sand soil solidifying material was given. The main parts of the backfill system, such as the backfill preparation system, the pipeline transportation system, the backfill systems in fully mechanized mining faces and the backfill process, were presented emphatically.

RECOMMENDATIONS FOR THE SELECTION,STABILIZATION,AND COMPACTION OF SOIL FOR RAMMED EARTH WALL CONSTRUCTION

Rammed earth possesses environmental advantages over most other competing construction materials.However,if it is to be more routinely used in the construction of modern,sustainable buildings,its material properties and produc-tion processes must be properly quantified.This paper proposes practical recommendations for soil selection,stabilizer treatment,and on-site compaction for rammed earth,based on a recent set of 219 stabilization experiments.The pur-pose of the recommendations is to maximize the probability of constructing rammed earth walls that meet or exceed a compressive strength criterion of 2 MPa.The recommendations cover:(1)Quantifying the natural soil properties of linear shrinkage and texture in a staged sequence in order to identify suitable soils to stabilize(and to reject unsuit-able soils);(2)Quantifying the amounts of cement and/or lime to be added to the selected soil according to the values of soil properties measured;and(3)Quantifying the forces involved in on-site compaction of stabilized soil(for both manual and pneumatic ramming),and relating these to laboratory-based test standards.Although the recommenda-tions need to be tested and verified/refined using new data,their initial application to rammed earth construction situations in Australia indicates that they have predictive utility.Further research will also indicate the degree of applicability of the recommendations to the production of compressed earth bricks.

Reinforcement of Clay Soils through Fracture Grouting

Fracture grouting is widely used for building foundation reinforcement,however the underpinning mechanisms are still not clear.Using numerical results about a single-hole fracture grouting process as a basis,a model composed of soil and grouting veins has been created to analyze the reinforcement mechanism.The influence weights of the grouting vein skeleton and compaction effect have been studied,thereby obtaining relevant information on the compressive modulus of the considered composite soil.The research results show that the compaction effect plays a leading role in the soil fracture grouting reinforcement.The grouting pressure,the hardened grouting vein modulus,and the shape of the grouting veins all influence the compressive modulus of the composite soil.

A Study on Water Repellent Effectiveness of Natural Oil-Applied Soil as a Building Material

This study was performed to investigate the water repellent effectiveness of natural oil-applied soil when it is used as a building material. Natural oil types such as olive oil, bean oil, perilla oil and linseed oil, which are being used for producing water repellent timber, are selected for the experiments. It is expected that perilla oil and in seed oil, which are drying oil types will have better water repellent effectiveness than the other types. For the evaluation of water repellence of natural oil-applied soil, a contact angle test was performed. A contact angle of water drop on various surface conditions were tested, and large differences were seen between the natural oil-applied soil and untreated soil. As a result, it is showed that all natural oil types have water repellent effectiveness. However, linseed oil, which is a drying oil type, shows an outstanding water repellent effectiveness value, while perila oil, which is also a drying oil type, shows the lowest value. Additionally, results show that there is no link between water repellent effectiveness and the number of applications of natural oil. Nevertheless, existing commercial water repellents show better performance than natural oil, and it is anticipated that the results of this study will provide essential information for further research to enhance the water repellent effectiveness of soil as a building material.

Shell Roof of Tall Buildings in Earthquake Zones

This paper studies and analyzes tall buildings with shell and flat roof responses designed for gravity and earthquake loads in different zones having different soil profiles. These tall buildings having two different heights and different configurations are simulated with different load combinations. The responses of the simulated structural models with flat and shell roofs are studied and analyzed. These responses draw recommendations and guidelines for preliminary design of structurally efficient and reliable tall buildings with shell roof in earthquake zones. Five different earthquake zone factors (Z1 - Z5) along with the five different soil profiles (S1 - S5) are selected in this study. The non-linear dynamic response of buildings was obtained using three simulated models of buildings;square/rectangular, circular, and tube-shaped building. Total of 12 building models, four under each category, are analyzed using the finite element software (STAAD pro) subjected to the gravity as well as earthquake loading defined by UBC and IBC codes. Each building model is analyzed with two different story heights;which are 120 meters for 30 stories and 72 meters for 18 stories respectively. Horizontal and vertical displacement comparison is made among the flat roof and shell roof building for 32 and 18 stories building satisfying the ACI code of design requirement and drift index of 1/500 (0.002). The results showed that the drift index value for all the studied buildings is close to 0.002. All the maximum horizontal and vertical deflections occur under the earthquake zone-5 (0.40 gravitational acceleration) with soil profile-5 (Soft soil). The shell roof slab with less thickness than the flat roof slab did satisfy the horizontal and vertical deflection limits, therefore, it is more economical than the flat roof slab.

Physico-Chemical Studies of the Bricks in Mud Raw Used in the Construction of Century-Old Huts(Straw Huts):Case of the Urban Commune of Kouroussa

Building construction using cement bricks on the one hand,and mud bricks on the other hand,presents problems of resistance and durability in the face of natural weathering in our country(Republic of Guinea).These difficulties could be linked to non-compliance with standards and the failure to master certain physico-chemical,mechanical and technical parameters when constructing a building.In order to remedy this problem,a series of studies were carried out on samples of mud bricks used in the construction of century-old straw hut buildings in the urban commune of Kouroussa(Republic of Guinea).To this end,the compressive strength of the brick samples was assessed either:0.10 MPa,and sensory techniques of certain characteristics were carried out to evaluate the cohesion of the elements in the brick samples,such as:coward boule technique,hand washing test,withdrawal of a soil(pellet or ring test)and of the jar test.The physico-chemical analyses methods were carried out using XRF(X-Ray Fluorescence Spectrometry),granulometry and Atterberg limits in accordance with NF P 94-051.These results showed a high insoluble residue content(49.9%)and the sample had a clay-like appearance with a low PI(Plasticity Index)=8%.This study could be an alternative guide for the authorities in charge of housing and construction in the Kouroussa prefecture(Republic of Guinea).because,the majority of houses in Upper Guinea are built with mud raw bricks or fired bricks.

Thermomechanical and Hydrous Effect of Heavy Fuel Oil in a Building Material Based on Silty Clayey Soil

This study focuses on the use of heavy fuel oil in construction in Burkina Faso.Mixed with silty and/or clay soil,it is used as a coating to reinforce the walls of raw soil constructions which are very sensitive to water.The interest of this paper is to shed light on the thermomechanical and above all water effects of heavy fuel oil on a sample of silty clayey soil.To achieve this,we used heavy fuel oil added in different proportions to silty clayey soil,to make sample of bricks on which tests were carried out.At the end of the experimental tests carried out on materials made(bricks)with our soil sample,it appears that heavy fuel oil moderately reduces the mechanical resistance of bricks and slightly increases thermal diffusion through them.On the contrary,we note a very good water resistance of the bricks thanks to the heavy fuel oil,in particular their water absorption by capillarity.This confirms that the mixture of heavy fuel oil and a silty-clayey soil used as a coating makes it possible to prevent the infiltration of water into the walls of raw soil constructions.However,its use as a construction material does not guarantee very good mechanical resistance,and slightly increases thermal diffusion.

Thermophysical, Mechanical and Durability Characterization of Adobe Bricks Reinforced with Fonio (Digitaria exilis) Sounds

Buildings constructed using modern materials such as cement are energy-intensive, facilitate heat transfer and thus promote warming inside the building. However, the Sudano-Sahelian regions have a hot climate occupying a large period of the year, thus requiring not only sustainable construction materials, but also which provide thermal comfort in the building by limiting the energy demand for air conditioning. These qualifications are important for sub-Saharan African countries in general and those of the Sudano-Sahelian zone in particular, which need ecological materials with good thermal performance to limit heating inside buildings. This study is an energy recovery of agricultural waste in buildings with a view to offering the populations of the northern regions of Cameroon suitable materials at lower cost for the construction of buildings. The soil used for this study was extracted from the locality of Yagoua where the populations make abundant use of mud bricks. Fonio waste was incorporated at low levels into the earth bricks, particularly at 0%, 1%, 2%, 3%, and 4%, with a view to strengthening their thermophysical and mechanical properties. The results obtained indicate that earth bricks reinforced with 4% waste showed better thermal and mechanical insulation properties compared to other formulations with an improvement of 16% and 78% respectively compared to the unreinforced samples. This research allows us to conclude that fonio waste can be used practically without expense in the building with a view to its energy recovery and will promote not only thermal comfort and the limitation of the energy supply for air conditioning, but the construction of more sustainable buildings with a cleaner environment.

Thermophysical Characterization of Local Materials from a Locality in Chad for Use in Eco-Building

With the aim of enhancing the value of local building materials, the subject of this paper is a thermophysical study of natural Chadian clay from the eastern region of Chad, “Abeche”. Samples were taken from a brickwork in Abeche from a depth of 1 m, then using a clay brick-making press, 4 × 5 × 8 cm3 clay test tubes were made with 2%, 4%, 6% and 8% cow dung, and a 100% clay sample was used as a control. These samples underwent thermophysical characterization using the hot-wire method with a hot-plane option, yielding results that could improve thermophysical performance. The thermal conductivity of the test sample is in the order of 0.715 to 0.420 W/m. K, at 8% for cow dung, so the addition of cow dung as a percentage in the clay matrix enabled us to obtain various satisfactory thermal parameters.

Simple and fast prediction of train-induced track forces,ground and building vibrations

A simple and fast prediction scheme is presented for train-induced ground and building vibrations.Simple models such as(one-dimensional)transfer matrices are used for the vehicle–track–soil interaction and for the building–soil interaction.The wave propagation through layered soils is approximated by a frequency-dependent homogeneous half-space.The prediction is divided into the parts“emission”(excitation by railway traffic),“transmission”(wave propagation through the soil)and“immission”(transfer into a building).The link between the modules is made by the excitation force between emission and transmission,and by the free-field vibration between transmission and immission.All formula for the simple vehicle–track,soil and building models are given in this article.The behaviour of the models is demonstrated by typical examples,including the mitigation of train vibrations by elastic track elements,the low-and high-frequency cut-offs characteristic for layered soils,and the interacting soil,wall and floor resonances of multi-storey buildings.It is shown that the results of the simple prediction models can well represent the behaviour of the more time-consuming detailed models,the finite-element boundary-element models of the track,the wavenumber integrals for the soil and the three-dimensional finite-element models of the building.In addition,measurement examples are given for each part of the prediction,confirming that the methods provide reasonable results.As the prediction models are fast in calculation,many predictions can be done,for example to assess the environmental effect along a new railway line.The simple models have the additional advantage that the user needs to know only a minimum of parameters.So,the prediction is fast and user-friendly,but also theoretically and experimentally well-founded.

Availability of seismic vulnerability index(K_g) in the assessment of building damage in Van, Eastern Turkey

The seismic vulnerability index(Kg) is a parameter that depends on the dynamic properties of soil. With this parameter, it is possible to evaluate the vulnerability of a point-based site under strong ground motion. Since it is related to the natural vibration period and amplification factor, the parameter can be calculated for both soil and structure. In this study, HVSR microtremor measurements are recorded at more than 200 points in the Van region to generate a seismic vulnerability index map. After generating the map, it is determined that the hazard potential and seismic vulnerability index is high at the sites close to Van Lake and at the densely populated city center. Damage information of the buildings investigated after the 2011 Van earthquakes(Mw = 7.1) are placed on the seismic vulnerability index map and it is realized that there may be a correlation between the damage and the seismic vulnerability index. There is a high correlation, approximately 80 percent, between the damage rate map based on the damaged building data and the K_g values. In addition, vulnerability indexes of buildings are calculated and the effect of local soil conditions and building properties on the damage levels are determined. From the results of this study and the site observations after the 2011 Van earthquakes, it is found that structural damage is not only structure-dependent but is also related to the dynamic behavior of soil layers and local soil conditions.