Structural Solutions

Structural Solutions

GSI is involved in the pre-disaster capacity assessment of existing structures, post-disaster damage assessment followed by retrofit design implementation for existing structures and new design of earthquake-resistant structures via its design center. Moreover; structural engineers and geotechnical engineers at GSI are working in collaboration with Ehime University Satellite Office (Kathmandu) in the field of earthquake engineering conducting interdisciplinary research, especially after the 2015 Gorkha earthquake.

1. Microtremor Survey

Micro-tremor survey of ground and multi-storied buildings for site vs structural response characterization in Kathmandu valley, site characterization of Pokhara valley are current studies under the flagship of Ehime University Satellite Office. The principal aim of these surveys is to develop seismic micro-zonation maps of varying resolutions for various urban and urbanizing areas of Nepal for site based consideration in assessment of existing structures as well as in design of new structures.

2. Post Earthquake Assessment

In the aftermath of the Gorkha earthquake, as part of the post-earthquake damage assessment, the GSI team conducted numerous site studies (commercial services included) focusing on both geotechnical and structural aspects of observed damages. These site studies primarily focused around the most notably damaged areas of Kathmandu, Lalitpur, Bhaktapur, Sindhupalchowk and Dolakha districts.

GSI also facilitated early studies on microtremor monitoring at heritage sites (Basantapur Durbar Square, Bhaktapur Durbar Square, Patan Durbar Square, Changu Narayan, Swayambhunath, Pashupatinath, Sankhu,etc.) with international scholars from Kagawa University and Ehime University.

3. Performance-Based Capacity Assessment of Existing Structures

Performance-based earthquake engineering (PBEE) analysis techniques are applied in evaluating the capacity of existing structures –both masonry and reinforced concrete structures. FEMA 356, ATC 40, ASCE 41 and EN 1998:2004 are followed in absence of clarifying the information in the technical guideline prepared by the Department of Urban Development and Building Construction (DUDBC) Nepal.

Fragility analysis is carried out to quantitatively assess the expected performance of the structure in future strong ground motion events. HAZUS MH guideline is followed for the fragility curve generation. Since material properties of structural elements play a crucial role in its estimated performance, laboratory testing is explicitly carried out for capacity assessment purposes.

If applicable, capacity assessment results in the need for retrofit intervention for the structure to be code compliant for design level performance.

4. Retrofit Analysis, Design and Implementation

Retrofit analysis and design are carried out after the capacity evaluation of damaged structures. Economic analysis is carried out prior to retrofit design based on the age of the structure, utility value after the retrofit, client’s preference, etc. Once economically justified, the retrofit design is carried out based on principles of performance-based design.

In RC framed structures, FEM based modeling is used in the retrofit design. In the case of masonry structures, 3MURI® based on EN 1998:2004 is used applying Frame by Macro Element (FME) modeling.

5. Earthquake Resistant Design and Analysis of New Structures

GSI provides earthquake resistant design using state-of-art numerical software; especially in the analysis and design of masonry structures by using Frame by Macro-element (FME) approach of 3MURI® (complaint to the provisions of EN:1998:2004).

6. Material Testing

The material testing laboratory of GSI meets the requirements of ASTM, IS and JGS standards. It can perform a variety of concrete and aggregate tests. The major test includes:

Aggregates

  • Particle size distribution analysis
  • Specific gravity
  • Hygroscopic moisture
  • Angularity
  • Hardness
  • Unit weight
  • Absorption
  • Los Angeles abrasion test

Asphalt and Concrete

  • Concrete mix test
  • Concrete compressive and flexural strength
  • Concrete or asphalt coring
  • Asphalt absorption
  • Asphalt mix design and verification
  • Asphalt bulk density
  • Marshall stability and flow
  • Asphalt specific gravity