|
Application of BCP-2007 and UBC-97 in seismic vulnerability assessment of gravity designed RC buildings in Pakistan
Muhammad Usman ALI, Shaukat Ali KHAN, Muhammad Yousaf ANWAR
Front. Struct. Civ. Eng.. 2017, 11 (4): 396-405.
https://doi.org/10.1007/s11709-017-0436-4
Recent earthquakes in Pakistan (Kashmir 2005, Balochistan 2008, and Balochistan 2013) revealed the vulnerability of existing building stock and the deficiencies in the then prevalent Pakistan Seismic Code (PSC-86 (1986)). This study investigates, through an analytical framework, the seismic vulnerability of these and other such buildings, in accordance with the newly developed Building Code of Pakistan – Seismic Provisions 2007 (BCP-SP 07). Detailed failure mode is presented for buildings designed as per the new code. Collapse of structures is predicted for only 8% increase in PGA after moderate damage. A previously developed method, based on Eurocode-8 (2004), is used as baseline. A deficient reinforced concrete frame, typical to local building practices, is analyzed and assessed for vulnerability using the BCP- SP 07 (2007) framework. A comparison is drawn for the same building, based on Eurocode-8 (2004). Derived vulnerability curves show that the previous framework overestimated the damage and hence the vulnerability. Comparison of vulnerability parameters with previous studies show slight difference in performance of buildings.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Compressive strength and stability of sustainable self-consolidating concrete containing fly ash, silica fume, and GGBS
Osama Ahmed MOHAMED, Omar Fawwaz NAJM
Front. Struct. Civ. Eng.. 2017, 11 (4): 406-411.
https://doi.org/10.1007/s11709-016-0350-1
This paper presents the findings of an experimental program seeking to understand the effect of mineral admixtures on fresh and hardened properties of sustainable self-consolidating concrete (SCC) mixes where up to 80% of Portland cement was replaced with fly ash, silica fume, or ground granulated blast furnace slag. Compressive strength of SCC mixes was measured after 3, 7, and 28 days of moist curing. It was concluded in this study that increasing the dosage of fly ash increases concrete flow but also decreases segregation resistance. In addition, for the water-to-cement ratio of 0.36 used in this study, it was observed that the compressive strength decreases compared to control mix after 28 days of curing when cement was partially replaced by 10%, 30%, and 40% of fly ash. However, a fly ash replacement ratio of 20% increased the compressive strength by a small margin compared to the control mix. Replacing cement with silica fume at 5%, 10%, 15%, and 20% was found to increase compressive strength of SCC mixes compared to the control mix. However, the highest 28 day compressive strength of 95.3 MPa occurred with SCC mixes in which 15% of the cement was replaced with silica fume.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Numerical study on the seismic response of the underground subway station- surrounding soil mass-ground adjacent building system
Guobo WANG, Mingzhi YUAN, Xianfeng MA, Jun WU
Front. Struct. Civ. Eng.. 2017, 11 (4): 424-435.
https://doi.org/10.1007/s11709-016-0381-7
Ground buildings constructed above metro station have increased very quickly due to the limited land resources in urban areas. In this paper, the seismic response of the Underground subway station-Surrounding soil mass-Ground adjacent buildings (USG) system subjected to various seismic loading is studied through numerical analysis. The numerical model is established in terms of the calculation domain, boundary condition, and contact property between soil and structure based on the real project. The reciprocal influence between subway station and ground adjacent building, and their effects on the dynamic characteristics of surrounding soil mass are also investigated. Through the numerical study, it is found that the impact of underground structure on the dynamic characteristics of the surrounding soil mass depends on its own dimension, and the presence of underground structure has certain impact on the seismic response of ground adjacent building. Due to the presence of underground structure and ground adjacent building, the vertical acceleration generated by the USG system cannot be ignored. The outcomes of this study can provide the references for seismic design of structures in the USG system.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
The effect of SiO2 nanoparticles derived from hydrothermal solutions on the performance of portland cement based materials
Ismael FLORES-VIVIAN, Rani G.K PRADOTO, Mohamadreza MOINI, Marina KOZHUKHOVA, Vadim POTAPOV, Konstantin SOBOLEV
Front. Struct. Civ. Eng.. 2017, 11 (4): 436-445.
https://doi.org/10.1007/s11709-017-0438-2
The nanoparticles of SiO2 were used in cement systems to modify the rheological behavior, to enhance the reactivity of supplementary cementitious materials, and also to improve the strength and durability. In this research, low-cost nano-SiO2 particles from natural hydrothermal solutions obtained by membrane ultrafiltration and, optionally, by cryochemical vacuum sublimation drying, were evaluated in portland cement based systems. ??The SiO2-rich solutions were obtained from the wells of Mutnovsky geothermal power station (Far East of Russia). The constant nano-SiO2 dosage of 0.25% (as a solid material by weight of cementitious materials) was used to compare the cement systems with different nanoparticles against a reference mortar and a commercially available nano-SiO2. Nanoparticles were characterized by X-Ray Diffraction (XRD), BET Surface Area, Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR) spectroscopy techniques. It was demonstrated that the addition of polycarboxylate ether superplasticizer and the dispersion treatment using an ultrasound processor can be used to facilitate the distribution of nano-SiO2 particles in the mixing water. The effect of nano-SiO2 particles in portland cement mortars was investigated by evaluating the flow, heat of hydration and compressive strength development. It was demonstrated that the use of nano-SiO2 particles can reduce the segregation and improve strength properties.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Seismic analysis of semi-gravity RC cantilever retaining wall with TDA backfill
Il-Sang AHN, Lijuan CHENG
Front. Struct. Civ. Eng.. 2017, 11 (4): 455-469.
https://doi.org/10.1007/s11709-017-0392-z
The seismic behavior of Tire Derived Aggregate (TDA) used as backfill material of 6.10 m high retaining walls was investigated based on nonlinear time-history Finite Element Analysis (FEA). The retaining walls were semi-gravity reinforced concrete cantilever type. In the backfill, a 2.74 m thick conventional soil layer was placed over a 3.06 m thick TDA layer. For comparison purpose, a conventional all soil-backfill model was also developed, and the analysis results from the two models under the Northridge and Takatori earthquakes were compared. The FEA results showed that both models did not experience major damage in the backfill under the Northridge earthquake. However, under the Takatori earthquake, the TDA-backfill model developed substantially large displacement in the retaining walls and in the backfill compared with the soil-backfill model. Regions of large plastic strain were mainly formed in the TDA layer, and the soil over the TDA layer did not experience such large plastic strain, suggesting less damage than the soil-backfill model. In addition, the acceleration on the backfill surface of the TDA-backfill model decreased substantially compared with the soil-backfill model. If an acceleration sensitive structure is placed on the surface of the backfill, the TDA backfill may induce less damage to it.
Figures and Tables |
References |
Related Articles |
Metrics
|
12 articles
|