Base Of Wall Research Articles

Seismic design of basement walls: evaluation of current practice in British Columbia

The current state of practice for the seismic design of basement walls in Vancouver is based on the Mononobe–Okabe (M–O) method using a peak ground acceleration (PGA) of 0.46g mandated by the National Building Code of Canada (NBCC). A series of dynamic numerical analyses are conducted to study the seismic performance of basement walls designed for the M–O earth pressures derived from different fractions of the current building code mandated PGA. The walls are subjected to seven ground motions spectrally matched to the uniform hazard spectrum (UHS) prescribed by the NBCC for Vancouver. The analyses show that current engineering practice for designing basement walls based on the M–O method and using a PGA of 0.46g is too conservative. The analyses suggest that a wall designed using a 50%–60% PGA will give an acceptable performance in terms of drift ratio. The results of sensitivity analyses on input parameters are also presented and discussed.

Design tables for URM / Hilfsmittel für die praxisnahe Bemessung von unbewehrtem Mauerwerk

AbstractDue to the coming introduction of Eurocode 6 (DIN EN 1996) in Germany many structural engineers ask for design assistances in order to apply the regulations and to accomplish the calculations in a cost‐effective manner. At the same time however, such design tables must result in efficient solutions with respect to the materials used because masonry has to compete with other building materials. This article adresses this issue. Design tables to determine the load bearing capacity using the very simplified and simplified calculation methods in accordance with DIN EN 1996‐3/NA are presented. Additionally diagrams for assessing the required minimum load on external walls exposed to wind loads and for determining the size of basement walls subjected to lateral earth pressure are given. This leads to the conclusion that, in almost all practical cases, it is possible to determine the cross‐section resistance of unreinforced masonry in accordance with Eurocode 6 quickly and effectively while still making the best possible use of the materials employed.

Geochemistry of A-type granites in the Huangshaping polymetallic deposit (South Hunan, China): Implications for granite evolution and associated mineralization

The Huangshaping granites in Hunan Province, South China were investigated for their geochemical characteristics. Three types of granites have been petrographically identified: quartz porphyry, granophyre, and granite porphyry. Whole rock geochemistry suggests that the Huangshaping granites, especially the granite porphyry, exhibit typical A-type granite characteristics with their enrichment in Si, Rb, U, Th, and Nb and significant depletion in Ba, Sr, Ti, Eu, and P. Based on the Al, Y and Zr contents as well as the REE patterns of the rocks investigated, the quartz porphyry and the granophyre are classified as A1 type alkaline granites whereas the granite porphyry is considered as A2 type aluminous granite. Whole rock and quartz/feldspar O isotope data yields a wide range of δ18OSMOW values (11.09–26.32‰). The granites are characterized by high radiogenic Pb isotopic composition. The present-day whole rock Pb isotopic ratios are 206Pb/204Pb=18.706–19.155, 207Pb/204Pb=15.616–15.711 and 208Pb/204Pb=38.734–39.296. Combining the O–Pb isotope compositions with major, trace and REE geochemistry and regional geology characteristics, the Huangshaping granites were determined to resemble within-plate granites that were mainly derived from a felsic infracrustal source related to continental extension. The magma source of the quartz porphyry and the granophyre may have been generated from deeper depths, and then ascended rapidly with limited water content and low oxygen fugacity, which contributed to Cu, Pb and Zn mineralization. On the other hand, the magma that generated the granite porphyry may have ascended relatively slower and experienced pronounced crystal fractionation, upper-crustal basement rock contamination (assimilation) and wall–rock interaction, producing the Sn- and W-rich granite porphyry. This study reveals the crustal extension process and associated magmatic–metallogenic activities during 180–150Ma in South Hunan.

지하 영구벽체 말뚝단면 구조형식의 효용성 분석

지하 영구벽체 말뚝단면 구조형식의 효용성 분석

Crystallization and eruption ages of Breccia Museo (Campi Flegrei caldera, Italy) plutonic clasts and their relation to the Campanian ignimbrite

The Campi Flegrei volcanic district (Naples region, Italy) is a 12-km-wide, restless caldera system that has erupted at least six voluminous ignimbrites during the late Pleistocene, including the >300 km3 Campanian ignimbrite (CI) which originated from the largest known volcanic event of the Mediterranean region. The Breccia Museo (BM), a petrologically heterogeneous and stratigraphically complex volcanic deposit extending over 200 km2 in close proximity to Campi Flegrei, has long remained contentious regarding its age and stratigraphic relation to the CI. Here, we present crystallization and eruption ages for BM plutonic ejecta clasts that were determined via uranium decay series and (U–Th)/He dating of zircon, respectively. Despite mineralogical and textural heterogeneity of these syenitic clasts, their U–Th zircon rim crystallization ages are indistinguishable with an average age of 49.7 ± 2.5 ka (2σ errors; mean square of weighted deviates MSWD = 1.2; n = 34). A subset of these crystals was used to obtain disequilibrium-corrected (U–Th)/He zircon ages which average 41.7 ± 1.8 ka (probability of fit P = 0.54; n = 15). This age closely overlaps with published CI 40Ar/39Ar eruption ages (40.6 ± 0.1 ka) after recalibration to recently revised flux monitor ages. Concordant eruption ages for BM and CI agree with previous chemostratigraphic and paleomagnetic correlations, suggesting their origin from the same eruption. However, they are at variance with recalibrated 40Ar/39Ar ages which have BM postdate CI by 3 ± 1 ka. BM syenites show similar geochemical and Sr–Nd isotopical features of pre-caldera rocks erupted between 58 and 46 ka, but are distinctive from subsequent caldera-forming magmas. Energy-constrained assimilation and fractional crystallization modeling of Nd–Sr isotopic data suggests that pre-caldera magmas formed a carapace of BM-type intrusions in a mid-crust magma chamber (≥8 km depth) shielding the younger CI magma from contamination by Hercynian basement wall rocks. An ~41–50 ka hiatus in crystallization ages implies rapid solidification of these pre-CI intrusions. This argues against protracted pre-eruptive storage of a large volume of CI magma at shallow crustal levels.

Earth pressure distribution behind rigid non-yielding walls under the effect of repeated loading on backfill

One of the most important factors in optimized design of non-yielding retaining walls like basement walls and bridge abutments is to determine the exact variation of earth pressure acting on such walls. In this paper, the distribution of at rest earth pressure behind a laboratory model of a fixed and rigid retaining wall with a cohesionless dry backfill is measured under the effect of static and repeated loads. The same conditions of the experimental model are then simulated numerically with a two-dimensional finite-difference analysis computer code. For the purpose of model verification, the results of numerical model are compared to the results of the experimental model, which is similar in geometrical and geomechanical properties. Cyclic surcharges with different amplitudes and frequencies are applied in different distances from the wall, and the earth pressure distribution, the resultant force, and its point of application are investigated. The effect of soil and loading parameters on the at rest earth pressure is also evaluated, and a parametric study has been carried out. The results of model show a significant increase in the earth pressure due to cyclic loading compared to static loading, especially in the initial cycles of loading. It indicates that the effect of cycling nature of loading should be essentially taken into account in the design of retaining walls.

Histological study of the effect of Piroxicam on testes of albino mice Mus musculus

Non- Steroidal Anti Inflammatory Drugs (NSAIDs) are the most frequently prescribed therapeutic agents, used for the treatment of rheumatic diseases, because they have analgesic, antipyretic and anti inflammatory action. Piroxicam is a well-known member of family NSAIDs use to reduce inflammation, pain associated with arthritis , osteoarthritis and ankylosing spondylitis .The objective of the present study is to evaluate the effect of different doses of Piroxicam upon testis tissue in mice. Twenty four male albino Swiss mice were randomly divided into control (n = 6 ) and experimental (n =18) groups .The experimental groups are subdivides into three groups of six mice. Each received (0.29, 1.428, 2.857)mg/kg/day for fourteenth days , respectively ; however the control group just received distill water. In fifteenth day , mice were killed and testes tissue was prepared for light microscopic study .All animals exposed to drug were serve to have a depletion of germ cells, germinal cell necrorosis , especially in Spermatogonia and Leydig cells which had an abnormal fibroblast like appearance , abnormal space between neighboring Sertoli cells, thickness in seminiferous tubules basement membrane and wall arteries, therefore it is recommended that usage of this drug have harmful side effects on male fertility.

Efficient Horizontal Ground Heat Exchanger Simulation with Zone Heat Balance Integration

For horizontal heat exchangers buried near a building slab or basement, interaction between the heat exchanger and the zone can be significant. Thermal interference effects can also be significant for heat exchangers with multiple pipes in close proximity. Previous simulation methodologies have not modeled these phenomena in a general manner and have lacked integration with other simulation domains, including zone heat balance calculations and fluid loop solvers. A numerical model for horizontal ground heat exchanger applications is presented, featuring a computationally efficient mesh and flexible heat exchanger tube placement. The model integrates the ground with zone heat balance and hydronic system simulations through boundary conditions within a whole-building energy simulation program. Thermal interference between pipes is captured, including circuiting effects of the fluid flow direction in individual pipes. Validation is performed using experimental data from a foundation heat exchanger research facility. Undisturbed ground temperature data is used to estimate ground and boundary properties. The model predicts heat pump entering fluid temperature with mean error of 1.3°C (2.3°F) and basement wall heat flux with mean error of 1.1 W/m2 (0.35 btu/hr-ft2). This accuracy is achieved with a coarse grid, ensuring a small computational burden suitable for whole-building energy simulation.

Variation in residential radon levels in new Danish homes

Radon-222 gas arises from the radioactive decay of radium-226 and has a half-life of 3.8 days. This gas percolates up through soil into buildings, and if it is not evacuated, there can be much higher exposure levels indoors than outdoors, which is where human exposure occurs. Radon exposure is classified as a human carcinogen, and new Danish homes must be constructed to ensure indoor radon levels below 100 Bq/m(3). Our purpose was to assess how well 200 newly constructed single detached homes perform according to building regulations pertaining to radon and identify the association between indoor radon in these homes and municipality, home age, floor area, floor level, basement, and outer wall and roof construction. Median (5-95 percentile) indoor radon levels were 36.8 (9.0-118) Bq/m(3) , but indoor radon exceeded 100 Bq/m(3) in 14 of these new homes. The investigated variables explained nine percent of the variation in indoor radon levels, and although associations were positive, none of these were statistically significant. In this study, radon levels were generally low, but we found that 14 (7%) of the 200 new homes had indoor radon levels over 100 Bq/m(3). More work is needed to determine the determinants of indoor radon.

"In the Footsteps of Kraków’s European Identity" The Rynek Underground Archaeological Exhibit

"In the Footsteps of Kraków’s European Identity" The Rynek Underground Archaeological Exhibit

Recent findings on seismic earth pressures

SUMMARYDespite a lack of evidence or credible case histories of engineered retaining walls and basement walls being damaged during earthquakes, design codes and standard of engineering practice have dictated that seismic earth pressures should be included in the design of earth retaining structures in seismic regions. Methods of estimating seismic earth pressures are based on experiments and theories performed and developed decades ago without consideration of geometric and material property equivalence or scaling. More recent experiments using centrifuges that can properly scale geometry and material properties have given new insights on the development of seismic earth pressures on various types of earth retaining wall systems with different types of retained soil. Copyright © 2012 John Wiley & Sons, Ltd.

An estimated prediction of the deformability of mineral wool (MW) slabs under long-term compressive stress

This paper presents the results of testing the strength and deformability of mineral wool slabs used for insulating flat roofs, facades, cast-in-place floors and external basement walls as well as for sound insulation in the floor slabs of buildings. The empirical equations for calculating the stress σ10%, tangential modulus of elasticity E and ultimate relative strain ɛcr (which, when exceeded, causes a considerable strain increase) of mineral wool slabs under short-term compression are provided. A regression model of the interrelationship between the predicted pointwise values of creep strains for a lead time of 10years and parameters such as the density, long-term compressive stress σc=0.35·σ10% and ultimate relative strain ɛcr of slabs under short-term compression is suggested.

Technical note: Airtightness of older-generation energy-efficient houses in Saskatoon

The aim of this study was to collect long-term in-service energy efficiency data from older-generation energy-efficient houses built in Canada in the past decades. Six houses with highly insulated building envelope assemblies built (or retrofitted) from 1979 to 1992 in the Saskatoon area were inspected during March 2012. As typical energy-efficient houses for this area, all were built with double 2 × 4 stud walls with the gap between walls ranging from 4 to about 12 in and with nominal wall insulation varying from RSI * 6.34 (R* 36) to RSI 10.57 (R 60). The roof insulation ranged from RSI 10.57 (R 60) to RSI 14.09 (R 80). The below-grade walls were also well insulated, and these were mainly permanent wood foundations. Polyethylene was used as a combined air barrier and vapour barrier for the building envelopes. The major results included the following: the airtightness values based on blower-door tests ranged from 0.78 to 2.55 air changes per hour at 50 Pa measured under normal operation conditions, with four houses below 1.50 air changes per hour at 50 Pa after 20–30 years. The No. 2 house had an original airtightness of 0.29 air changes per hour at 50 Pa and 0.22 air changes per hour when the windows were sealed with masking tape after the energy retrofit in 1982. The airtightness was measured to be 1.23 air changes per hour at 50 Pa in this survey after the owner installed new windows without properly sealing the interior air barrier. The No. 4 house had an airtightness of 0.78 air changes per hour, while the original airtightness test was 0.47 air changes per hour when the house was built over 20 years ago. All the six houses had EnerGuide Rating System of over 80, and one had a remarkable EnerGuide Rating System of 87. Windows and ventilation air were identified to be the largest heat loss components, followed by basement and exterior walls.

Clinical and pathological features of dense deposit disease in Chinese patients

Dense deposit disease (DDD) is a rare disease that has no universally effective treatment. Herein we explore the clinical and pathological features of DDD in Chinese patients and the therapeutic effect of Tripterygium wilfordii (TW). Clinical and pathological data of 10 Chinese patients with biopsy-proved DDD were collected and analyzed retrospectively. The patients consisted of 6 males and 4 females. All of them had heavy proteinuria and microscopic hematuria. Gross hematuria, renal insufficiency, anemia, hypertension and low serum complement 3 (C3) occurred in 3, 3, 5, 6 and 8 cases, respectively. Under light microscopy (LM), 8 cases exhibited membranoproliferative glomerulonephritis (MPGN). Periodic acid-Schiff (PAS) stain disclosed intense PAS-positive bright ribbon-like thickening of glomerular basement membranes (GBM). Immunofluorescence mainly showed diffuse fine granular and short linear deposition of C3 along the glomerular capillary wall. Under electron microscopy, ribbon-like electrondense intramembranous deposits were identified in the lamina densa of the GBM, along the tubule basement membranes (TBM) and wall of Bowman's capsule. Before admission, 6 cases were treated with prednisone, cyclophosphamide and/or cyclosporin A with no response. Proteinuria in 8 cases who received TW during the course decreased at different degrees. The clinical and pathological features in DDD patients were various. The effect of TW in patients with DDD merits further investigation.

Implications of rising groundwater level on structural integrity of underground structures – investigations and retrofit of a large building complex

PurposeGroundwater levels (GWL) are rising in many cities in the world. The purpose of this study is to present the multi‐faceted approach adopted for examining the impact of a 3 m rise in GWL on the durability, stability and strength of the structural components of a building complex with 40,000 m2 basement. It also reports on the retrofit measures adopted to remedy the situation.Design/methodology/approachThe overall stability of the building complex was examined for the revised loading conditions as well as the need to strengthen the structurally deficient components to satisfy owner's requirement of a dry and operational basement without the dewatering operation. Structural conditions of the basement walls and a slab of the building complex were assessed based on code guidelines, visual observations, site investigations, analytical finite element model (FEM) studies and sound engineering judgement.FindingsAbout 25 percent of the existing basement slab was found to be structrally deficient to resist the applied hydrostatic load. A number of articulation and construction details were also found to be inadequate. Various options for retrofit for the deficient structural components and articulation details were examined and design details were presented for a cost‐effective solution.Research limitations/implicationsThe presented methodology is general and can be adopted for similar situations. However, the presented solutions and conclusions are specific to the problem presented herein and modifications will be required for adoption to other situations.Practical implicationsPractising engineers are made aware of the problem of rising GWL for underground structures. Practical information is presented for practising engineers to solve the problem of water leakage in a large basement.Originality/valueThis paper presents an integrated approach for addressing the structural implications of rising groundwater level in an operational basement of a large building complex.

Effects of soil non-linearity on the seismic response of restrained retaining walls

Retaining structures characterised by high rigidity and various kinematic constraints, such as bridge abutments and basement walls, do not permit limit-equilibrium conditions to be developed. Therefore, according to contemporary norms and geotechnical design practice worldwide, they are most frequently designed utilising the elasticity-based methods, which usually lead to substantially increased dynamic earth pressures. The present paper aims to examine how and to what extent the potentially developed non-linearity of the retained soil may affect: (a) the dynamic distress of a rigid fixed-base retaining wall, and (b) the seismic response of the retained soil layer. For this purpose, a parametric study is conducted which is based on two-dimensional dynamic finite-element analyses using various idealised or real seismic excitations scaled to several intensity levels. Soil non-linearity is realistically taken into account via the commonly used equivalent-linear approach. The results of the present study demonstrate that potential non-linearity of a soil layer retained by a rigid fixed-base wall alters the soil amplification pattern behind the wall and leads to dynamic earth pressures usually lower than those proposed by seismic norms.

전단경간비에 따른 합성지하벽의 거동과 접촉면의 조건을 고려한 유한요소 해석

본 연구의 목적은 전단경간비에 따른 합성지하벽의 거동을 실험적으로 연구하고 유한요소해석 프로그램인 ADINA를 활용하여 합성지하벽 (Composite Basement Wall, CBW)의 비선형 거동의 예측이다. 특히 각 층 바닥 부근과 같이 콘크리트가 압축응력상태일 때의 합성벽의 거동을 연구하였다. 특히 강재와 콘크리트가 접촉되는 부분의 모델링 방법에 따른 해석방법의 적합성을 검토하고자 하였다. 콘크리트 벽체부분이 압축응력상태에 있는 합성지하벽의 거동을 이해하기 위하여 합성지하벽에 대한 실험을 실시하고 ADINA 프로그램을 이용하여 유한요소해석을 실시하였다. 해석의 편의를 위하여, 철근은 별도의 독립 요소로 모델링하지 않고, 콘크리트에 등분포되어 콘크리트와 함께 거동하는 것으로 하고 모든 요소는 소성거동을 표현하기 위하여 이선형 모델로 하였다. 강재와 콘크리트의 접촉면과 관련해서는 접촉면의 연결조건에 따라, AGO, SEGO-T 그리고 SEGO-NT로 모델링하여 해석을 실시한 뒤 각 조건에 따른 응력흐름과 집중정도를 관찰하고 그 결과를 실험결과와 비교하였다. 연구결과, 합성지하벽은 전단경간비가 비록 1에 가깝더라도, 강재의 소성변형에 의해 충분히 연성적인 거동을 보이는 것으로 나타났으며, 이와 같은 거동을 묘사하기 위하여 ADINA 프로그램을 이용하여 콘크리트와 강재 및 스터드볼트의 비선형특성을 고려하고 접촉면 요소로서 강재와 콘크리트의 접합면을 모델링하여 해석한 결과 접촉면연결과 모든 절점공유 옵션을 사용한 모델을 적용할 경우, 실험결과와 근사한 예측이 가능한 것으로 나타났다. The objective of this paper is to study the structural behavior of Composite Basement Wall (CBW) according to shear span-to-depth ratio through an experiment and predict the nonlinear behavior of CBW by using ADINA program widely has been being used for FE analysis. Especially, this study focuses on the part of CBW in which the Reinforced Concrete (RC) is under compression stress; At the region of CBW around each floor, RC part stresses by compressive force when lateral press by soil acts on the wall. The contact condition between RC wall and steel (H-Pile) including stud connector is main factor in the analysis since it governs overall structural behavior. In order to understand the structural behavior of CBW whose RC part is under compressive stress, an experimental work and finite element analysis were performed. Main parameter in the test is shear span-to-depth ratio. For simplicity in analysis, reinforcements were not modeled as a seperated element but idealized as smeared to concrete. All elements were modeled to have bi-linear relation of material properties. Three type of contact conditions such as All Generate Option (AGO), Same Element Group Option with Tie(SEGO-T) and Same Element Group Option with Not tie(SEGO-NT) were considered in the analysis. For each analysis, the stress flow and concentration were reviewed and analysis result was compared to test one. From the test result, CBW represented ductile behavior by contribution of steel member even if it had short shear span-to-depth ration which is close to "1". The global composite behavior of CBW whose concrete wall was under compressive stress could be predicted by using contact element in ADINA program. Especially, the modeling by using AGO and SEGO-T showed more close relation on comparing with test result.

Modeling soil–foundation–structure interaction

SUMMARYThis paper offers a guided tour through the various ways, used in practice, of accounting for soil–structure interaction in design and analysis, ranging from a complete analysis of the total combined system of foundation, soil and structure to approximate models of the system. The focus is on three types of structures: bridges on pile foundations, tall buildings with several levels of underground parking and large basement slabs with shallow embedment. The paper also reports on preliminary results from the study of seismic pressures against deep basement walls commissioned by the Structural Engineers Association of British Columbia. Copyright © 2011 John Wiley & Sons, Ltd.

Long-term prediction of creep strains of mineral wool slabs under constant compressive stress

The results obtained in determining the creep strain of mineral wool slabs under compressive stress, used for insulating flat roofs and facades, cast-in-place floors, curtain and external basement walls, as well as for sound insulation of floors, are presented. The creep strain tests were conducted under a compressive stress of σ c =0.35σ 10%. Interval forecasting of creep strain was made by extrapolating the creep behaviour and approximated in accordance with EN 1606 by a power equation and reduced to a linear form using logarithms. This was performed for a lead time of 10 years. The extension of the range of the confidence interval due to discount of the prediction data, i.e. a decrease in their informativity was allowed for by an additional coefficient. Analysis of the experimental data obtained from the tests having 65 and 122 days duration showed that the prediction of creep strains for 10 years can be made based on data obtained in experiments with durations shorter than the 122 days as specified by EN 13162. Interval prediction of creep strains (with a confidence probability of 90%) was based on using the mean square deviation of the actual direct observations of creep strains in logarithmic form to have the linear trend in a retrospective area.

Thermal response of basement wall systems with low-emissivity material and furred airspace

In basement wall systems, airspaces can contribute in obtaining a higher thermal resistance, if a low-emissivity material such as reflective foil is installed within a furred-airspace. In this study, numerical simulations were conducted using the hygrothermal model ‘hygIRC-C’ that was developed at the National Research Council of Canada’s Institute for Research in Construction to investigate the steady-state and transient thermal performance of basement wall systems. This model solves simultaneously the energy equation in the various material layers, surface-to-surface radiation equation in the furred-airspace assembly, Navier–Stokes equation for the airspace, and Darcy and Brinkman equations for the porous material layers. The wall systems used in the simulations incorporate a low-emissivity material (foil with emissivity = 0.04) bonded to a moulded/expanded polystyrene foam that is installed in a furred-airspace assembly. The furring is installed horizontally and covered with a gypsum board. The structural element of the wall (external layer) is a poured-in-place concrete. Walls with and without furred-airspace assembly were considered in this study. Also, consideration was given to investigate the effect of the above-grade and below-grade portions of the wall on the thermal performance when these walls are subjected to two different Canadian climates. Results showed that at steady-state condition, the effective thermal resistance ( R-value) of the wall with a furred-airspace assembly depends on the soil, outdoor, and indoor temperatures. Additionally, these wall configurations resulted in an energy savings of ~17% compared to walls without furred-airspace assembly when these walls are subjected to two different climate conditions.